5th international seminar on process hydrometallurgy
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5th InternationalSeminar on ProcessHydrometallurgy PresentationsTRANSCRIPT
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ed i t o r s
Fernando ValenzuelaCourtney Young
5th International Seminar on Process Hydrometallurgy
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5th International Seminar on Process Hydrometallurgy
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ed i t o r s
Fernando ValenzuelaCourtney Young
5th International Seminar on Process Hydrometallurgy
July 10 - 12, 2013
Santiago, Chile
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CopyrightGecamin,Chile.Allrightsreserved.Nopartofthispublicationmaybereproduced,storedortransmittedinanyformorbyanymeans,electronic,mechanical,byphotocopying,recordingorotherwise,withoutthepriorwrittenpermissionfromGecamin.
Authors disclaimerAnyviewsandopinionspresentedinthearticlespublishedintheseproceedingsaresolelythoseoftheauthorsanddonotnecessarilyrepresentthoseofGecamin.Theauthorstakefullandexclusiveresponsibilityfortechnicalcontent,style,languageandaccuracyoftheinformationpublishedherein.Thisinformationisnotintendednorimpliedtobeasubstituteforprofessionaladvice.Theeditorsarenotresponsibleforanydamagetopropertyorpersonsthatmayoccurasaresultofuseoftheinformationcontainedinthisvolume.
I.S.B.N.978-956-8504-88-5
GecaminPaseoBulnes197,Piso6Santiago,ChilePostcode:8330336Telephone:+56226521500www.gecamin.com
Online proceedings www.gecaminpublications.com/hydroprocess2013
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Contents
11 Organizers 13 Committees 17 Foreword 19 Preface 21 Acknowledgements
chap. 1 Plenary presentations
Impregnated activated carbon for gold extraction from thiosulfate solutions. Courtney Young and Nick Gow
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Geotechnical lessons learned from the operation of Cerro Verdes Crush Leach Pad 4-A. Helbert Galdos, Javier Guevara and Arnaldo Saavedra
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chap. 2 Base metals hydrometallurgy
Daily process mineralogy: A metallurgical tool for optimized copper leaching. Wolfgang Baum, Kevin Ausburn and Randy Zahn
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Direct production of high-purity cobalt sulfate heptahydrate from a NiCo deposit concentrate. Alex Mezei, Michael Johnson, Cornelia Lupu, Ron Molnar, Keith Lee and Robin Goad
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Copper extraction from oxide ore using sea water. Cynthia Torres, Mara Elisa Taboada, Tefilo Graber, Hctor Galleguillos and Helen Watling
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Kinetics of chalcopyrite leaching in either ferric sulfate or cupric sulfate media in the presence of NaCl. Tcia Veloso, Johne Peixoto, Michael Rodrigues and Versiane Albis Leo
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Mineral QTs in place leaching, standard sector. Hugo Letelier, Patricio Gimnez, Carola Gonzlez, Luis Zenteno and Carlos Castillo
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Study of the steel dust leaching for the recovery of zinc and cadmium. Ernesto de la Torre, Alicia Guevara and Cynthia Espinoza
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Zinc recovery from electric-arc furnace dust by hydrochloric leaching and bi-electrolyte electrolysis. Jos Ricaurte and Ernesto de la Torre
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A step closer to the leaching of primary sulfides. Guillermo Velarde111
Controlling the irrigation flow in heap leach piles of El Soldado mine by canopy system with thermal camera. Javier Ruiz-del-Solar, Omar Daud, Mauricio Correa and Marco Torres
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Hydrothermal mineral replacement reactions and their applications in mining and processing. Jing Zhao, Allan Pring, Jol Brugger, Fang Xia, Kan Li and Yung Ngothai
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Study of the recovery of silica from the zircon chemical treatment. Laura Rocha and Carlos Morais
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Maboumine process: Example of a promising process for developing a polymetallic ore deposit. Florent Delvalle, Valrie Weigel and Antoine Greco
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chap. 3 Cyanidation, leaching and recovery of gold
A theoretical study of sArt precipitate generation: Operational and safety impacts. Humberto Estay, Pablo Carvajal, Karina Gonzlez and Vernica Vsquez
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Development of a new technique to recover cyanide for gold mining using membranes contactors. Humberto Estay, Miguel Ortiz and Julio Romero
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Leaching of sulfide gold ores using dithiooxamide, a non-cyanide solvent of low-toxicity. Juan Pablo Serrano and Ernesto de la Torre
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Copper cyanocomplexes adsorption on activated carbon: Effects on the selectivity of gold dicyanide adsorption. Clauson Souza, Virginia Ciminelli and Daniel Majuste
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Cyanide leaching of copper-gold-silver ores. Humberto Estay, Pablo Carvajal, Karina Gonzlez, Hctor Yez, Waldo Bustos, Sergio Castro and Francisco Arriagada
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Successful application of sArt technology for gold-copper ore deposits. Kresimir Ljubetic, scar Lpez, David Kratochvil and David Sanguinetti
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chap. 4 Solvent extraction and ion exchange
Analysis phase separation profiles in copper extraction. Patricio Navarro and Sebastin Jara
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Mo recovery process from high acidity solutions via solvent extraction using CYANeX600. Mauricio Salamanca, Alejandro Quilodrn and Osvaldo Castro
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Use of Nr reagents in presence of nitrate ion in SX: A revision of the present moment. Rodrigo Zambra, Alejandro Quilodrn, Gonzalo Rivera and Osvaldo Castro
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Advantages and contributions of modifiers to copper extraction. Rodrigo Zambra, Alejandro Quilodrn, Osvaldo Castro and Sara Pascuale
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Regeneration process for copper solvent extraction reagents. Piritta Salonen and James Kabugo
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Metallurgical performance of small and medium size copper SX plants: Relevance of the SX reagent formulation. Philippe Joly and Francisco Reyes
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Removal of some heavy metals from a sulfate-containing residual mining solution using nano-structured calcium silicates. Fernando Valenzuela, Jaime Sapag, Carlos Basualto and Luis Verdugo
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chap. 5 Electrometallurgical processes and electrochemistry
Electrochemistry of enargite: Reactivity in alkaline solutions. Nick Gow, Courtney Young, Hsin-Hsuing Huang and Greg Hope
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Effects of organic impurities on zinc electrowinning. Daniel Majuste, Virginia Ciminelli, Eder Martins and Adelson de Sousa
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SeLe Technology: An alternative to boosting current efficiency and cathode quality in eW plants. Pedro Aylwin, Nicols Lagos and Patricio Melani
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Tankhouse parameters for transition from lead to alternative anodes. Scot Sandoval, Casey Clayton, Ephrem Gebrehiwot and Jason Morgan
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CoolBar: A new intercell bar for electrolytic processes. Gerardo Cifuentes and Rodolfo Mannheim
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Practical determination of galvanic corrosion of steel induced by mineral particles. Genny Leinenweber and Luis Cceres
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Mirs Starter Sheet Robotic Stripping Machine (ssrsM). Luis Felipe Ramrez
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chap. 6 Bioleaching processes
Bioaccelerant: A new biotechnological product for bioleaching process optimization. Mara de la Luz Osses, Matas Saavedra and Simn Beard
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The effect of temperature on column bioleaching of secondary copper sulfide ores. Michael Rodrigues, Klinger Lopes, Hamilton Lencio, Tcia Veloso and Versiane Albis Leo
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Leaching of copper oxide ore by in situ biological generation of sulphuric acid. Debora Monteiro de Oliveira, Luis Sobral and Diogo de Oliveira Padro
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A real-time method for detecting active microorganisms in commercial-scale biohydrometallurgical processes. Davor Cotoras and Pabla Viedma
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Bioleaching of covellite from low grade copper sulfide ore and tails. Vctor Zepeda, Pedro Galleguillos, Cecilia Demergasso, Dina Cautivo, Jos Soto and Yasna Contador
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chap. 7 Modeling, and optimizing hydrometallurgical operations and circuits
Implications of hydrodynamic testing for heap leach design. Stefan Robertson, Amado Guzmn and Graeme Miller
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Dynamic model of copper recovery in heaps, Compaa Minera Doa Ins de Collahuasi. Eduardo Flores, Juan Pablo Garcs, Christian Hu and Jess Casas
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Dynamic simulator of ore preparation processes and leaching. Francisco Reyes, Gabriel Tejeda, Pablo Karelovic, Aldo Cipriano, Miguel Herrera, Fernando Romero, Solange Rojas and Cristian Salgado
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DroP Project: Leaching process optimization for reducing water consumption in copper mining. Ulrike Broschek, Jorge Lobos, Jorge Cornejo, Luis Bravo, Josu Lagos and Karien Volker
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Rheometallurgical process risk mitigation through engineering data generation. Alex Mezei and Mike Ashbury
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chap. 8 Hydrometallurgical processes for producing salt and non-metals compounds
Some improvements in Caliche heap leaching. Javier Ordez, Silvia Valdez, Luis Moreno and Luis Cisternas
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Author's index439
Editors443
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Organizers
The Hydroprocess 2013 Seminar was organized by Montana Tech of the Uni-versity of Montana, UsA and Gecamin, Chile.
Montana Tech of the University of Montana
With more than 2,800 students on two campuses, Montana Tech is composed of the School of Mines & Engineering; College of Letters, Sciences & Profes-sional Studies; Highlands College; Graduate School; and the Montana Bureau of Mines & Geology.
Montana Tech emphasizes teamwork, collaboration, and hands-on learning. Montana Techs vision is to meet the changing needs of society by supplying knowledge and education through a strong curriculum augmented by research, graduate education and service. Its vision is to be a leader for higher education and research in the Pacific Northwest in engineering, science, energy, health, information sciences, and technology.
All programs derive a special character and emphasis from the unique setting and continued tradition of high quality that has characterized Montana Tech since its founding. Montana Tech has a long standing reputation for producing outstanding graduates and is committed to research; resulting in an unprecedented growth in its funded research over the last several years.
Learn more by visiting www.mtech.edu
Gecamin
Powering professional development for sustainable mining
Gecamin is a Chilean company with 15 years of experience organizing technical and international conferences for the mining industry. Our conferences aim to inform and inspire professionals from all over the world, fostering the exchange of best practices and innovative experiences.
Over 12,000 professionals have attended our events and have been trained in areas fundamental to the mining industry. These areas include Geology and
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Mining, Mineral Processing, Hydrometallurgy, Sustainability and Environment, Water and Energy, Maintenance and Automation, and Human Capital.
Gecamin seeks to contribute to the sustainable development of the mining industry by openly addressing its most pressing concerns and by offering a platform for knowledge exchange that aims at identifying the most sustainable solutions.
In 2012, Gecamin organized 10 conferences and 12 courses, with a total of 501 technical presentations, gathering more than 2600 delegates. A total of 128 mining houses from 37 countries were represented.
Learn more about Gecamin conferences by visiting www.gecamin.com
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Executive Committee
ch a i r
Gabriel Meruane , r&d Project Director, sQM Industrial, Chile
co - ch a i r sCourtney Young , Department Head and Lewis S. Prater Distinguished Professor, Metallurgical and Materials Engineering, Montana Tech, UsA
Javier Guevara , Hydrometallurgical Process Manager, Sociedad Minera Cerro Verde, Peru
2 0 1 2 ch a i rSergio Castro , Senior Processing Consultant, Arcadis, Chile
e x e cu t i v e d i r e c t o rCarlos Barahona , General Manager, Gecamin, Chile
t e chn i c a l coord i n at o rFernando Valenzuela , Professor, Universidad de Chile
s em i na r coord i n at o rFabiola Bustamante , Gecamin, Chile
a s s i s ta n t coord i n at o rRebekah Zale , Gecamin, Chile
Directing Members
Alejandro Dagnino , Mining Resources and
Development Manager, Minera Gaby SpA, Chile
Marcelo Jo , General Manager of Technical
Support, Xstrata Copper, Chile
Cleve Lightfoot , Global Practice Leader
Technology, Bhp Billiton, Chile
Percy Mayta , Technical Services Manager,
Freeport-McMoran Copper & Gold Inc., Peru
scar Rosas , Plant Manager, El Soldado
Division, Anglo American, Chile
Gustavo Tapia , Technological Innovation and
Process Manager, Antofagasta Minerals, Chile
Advisory Committee
Pablo Amigo , Jacobs Chile s.a.
Corby Anderson , Colorado School of Mines, usa
Francisco Arriagada , Arcadis, Chile
Antonio Ballester , Universidad
Complutense de Madrid, Spain
Directing Members
Alejandro Dagnino , Mining Resources and
Development Manager, Minera Gaby SpA, Chile
Marcelo Jo , General Manager of Technical
Support, Xstrata Copper, Chile
Cleve Lightfoot , Global Practice Leader
Technology, Bhp Billiton, Chile
Percy Mayta , Technical Services Manager,
Freeport-McMoran Copper & Gold Inc., Peru
scar Rosas , Plant Manager, El Soldado
Division, Anglo American, Chile
Gustavo Tapia , Technological Innovation and
Process Manager, Antofagasta Minerals, Chile
Advisory Committee
Pablo Amigo , Jacobs Chile s.a.
Corby Anderson , Colorado School of Mines, usa
Francisco Arriagada , Arcadis, Chile
Committees
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Antonio Ballester , Universidad
Complutense de Madrid, Spain
Enrique Carretero , amira International
Latin America Ltda., Chile
Dick Celmer , Fluor, Chile
Virginia Ciminelli , Universidade Federal
de Minas Gerais (uFmG), Brazil
Clenilson Da Silva Souza Junior , Instituto
Federal do Rio de Janeiro, Brazil
Ernesto de la Torre , Escuela Politcnica Nacional, Ecuador
George P. Demopoulos , McGill University, Canada
Claudia Diniz , Vale, Brazil
David Dixon , University of British Columbia, Canada
Steve Dixon , GoldCorp, usa
scar Ferrada , Minera Escondida, Chile
Rick Gilbert , Freeport-McMoran Copper & Gold Inc., usa
Manuel Guzmn , Molibdenos y Metales s.a., Chile
Miguel Herrera , Universidad Adolfo Ibez, Chile
Jorge Ipinza , Jri Engineering, Chile
Joaqun Martnez , Royal Institute of Technology, Sweden
Jorge Menacho , De Re Metallica Ingeniera Ltda., Chile
John Monhemius , Imperial College
London, United Kingdom
Miguel Monroy , Xstrata Copper, Lomas Bayas, Chile
Luis Moreno , Royal Institute of Technology, Sweden
Patricio Navarro , Universidad de Santiago de Chile
Felipe Nez , Minera Florida, Yamana, Chile
Manuel Olivares , ara Worley Parsons s.a., Chile
Kwadwo Osseo-Asare , Penn State University, usa
Vladimiros Papangelakis , University of Toronto, Canada
Eduardo Patio , Bhp Billiton Chile Inc.
Sergio Rivera , El Salvador Division, Codelco, Chile
David Robinson , csiro, Australia
Eloy Romn , Hochschild Mining, Peru
Luis Snchez , Bhp Billiton Pampa Norte, Chile
Nathan Stubina , Barrick Gold, Canada
Juan Carlos Tapia , amec International
Engineering and Construction, Chile
Julio Cesar Tremolada , Iberometex s.a.c., Peru
Petrus Van Staden , Mintek, South Africa
Guillermo Velarde , Sociedad Minera Cerro Verde s.a., Peru
Joan Vials , Universidad de Barcelona, Spain
Technical Committee
Fernando Acevedo , Pontificia Universidad
Catlica de Valparaso, Chile
Jaime Alfaro , Xstrata Copper, Tintaya, Peru
Luis Bergh , Universidad Tcnica Federico Santa Mara, Chile
Germn Cceres , Universidad de Atacama, Chile
Francisco Carranza , Universidad de Sevilla, Spain
Jess Casas , Process Consulting, Chile
Gerardo Cifuentes , Universidad de Santiago, Chile
Luis Cisternas , Universidad de Antofagasta/
cicitem/csiro, Chile
Francisco Cubillos , Universidad de Santiago de Chile
Manuel Chvez , Freeport-McMoran, Minera El Abra
Francisco Daz , The Chilean Commission
for Nuclear Energy, Chile
Jos Fernndez , Mantos Blancos
Division, Anglo American Chile
Juan Pablo Garcs , Ca. Minera Doa
Ins de Collahuasi, Chile
Juan Carlos Gentina , Pontificia Universidad
Catlica de Valparaso, Chile
Tefilo Graber , Universidad de Antofagasta, Chile
Nlida Heresi , Jri Ingeniera, Chile
Christian Hu , Ca. Minera Doa Ins de Collahuasi, Chile
Jos Hernndez , Universidad de Chile
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Juan Patricio Ibez , Universidad Tcnica
Federico Santa Mara, Chile
Hugo Letelier , El Teniente Division, Codelco, Chile
Hugo Maturana , Universidad de La Serena, Chile
Gonzalo Montes-Atenas , Universidad de Chile
Rafael Padilla , Universidad de Concepcin, Chile
Carolina Paipa , Universidad de Playa Ancha, Chile
Nelson Parra , Jri Ingeniera, Chile
Geysa Pereira , Hydrometallurgy, Vale, Brasil
Eduardo Robles , Hatch, Chile
Eladio Rojas , Chuquicamata Division, Codelco, Chile
Leonardo Romero , Universidad Catlica del Norte, Chile
Vernica Rueda , snc Lavalin, Chile
Andrs Soto , Universidad Mayor, Chile
Mara Elisa Taboada , Universidad de Antofagasta, Chile
Jaime Tapia , Universidad Arturo Prat, Chile
Diego Verdejo , Antofagasta Minerals, Chile
Editorial Committeeed i t o r sFernando Valenzuela , Universidad de Chile
Courtney Young , Montana Tech, usa
co p y e d i t o rRebekah Zale , Gecamin, Chile
r e v i ewer s
Versiane Albis Leo , Universidade
Federal de Ouro Preto, Brazil
Jaime Alfaro , Xstrata Tintaya, Peru
Francisco Arriagada , Arcadis, Chile
Pedro Aylwin , New Tech Copper SpA, Chile
Antonio Ballester , Universidad
Complutense de Madrid, Spain
Carlos Basualto , Universidad de Chile
Jess Casas , Process Consulting, Chile
Sergio Castro , Arcadis, Chile
Gerardo Cifuentes , Universidad de Santiago, Chile
Luis Cisternas , Universidad de Antofagasta/
cicitem/csiro, Chile
Davor Cotoras , Biohidrica, Biotecnologas del Agua, Chile
Clenilson Da Silva Souza Junior , Instituto
Federal do Rio de Janeiro, Brazil
Ernesto de la Torre , Escuela Politcnica Nacional, Ecuador
Javier Delgado , Novigi Ltda., Chile
Diana Endara , Escuela Politcnica Nacional, Ecuador
Humberto Estay , Arcadis, Chle
Helbert Galdos , Sociedad Minera Cerro Verde s.a.a., Peru
Nick Gow , FLSmidth, usa
Tefilo Graber , Universidad de Antofagasta, Chile
Alicia Guevara , Escuela Politcnica Nacional, Ecuador
Nlida Heresi , Jri Ingeniera, Chile
Miguel Herrera , Universidad Adolfo Ibez, Chile
Juan Patricio Ibez , Universidad Tcnica
Federico Santa Mara, Chile
Marcelo Jo , Xstrata Copper, Chile
Hugo Letelier , El Teniente Division, Codelco, Chile
Daniel Majuste , Federal University of Minas Gerais, Brazil
Hctor Mlaga , Sociedad Minera Cerro Verde s.a.a., Peru
Joaqun Martnez , Royal Institute of Technology, Sweden
Jorge Menacho , De Re Metallica Ingeniera Ltda., Chile
Gabriel Meruane , r&d Project Director,
sQm Industrial, Chile
Alex Mezei , sGs Mineral Services,
Metallurgical Operations, Canada
John Monhemius , Imperial College
London, United Kingdom
Luis Moreno , Royal Institute of Technology, Sweden
Caroline Muzawasi , University of Cape Town, South Africa
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Patricio Navarro , Universidad de Santiago de Chile
Rafael Padilla , Universidad de Concepcin, Chile
Vladimiros Papangelakis , University of Toronto, Canada
Jochen Petersen , University of Cape Town, South Africa
Li Qian , School of Minerals Processing and
Bioengineering, Central South University, China
Francisco Reyes , dictuc s.a., Chile
Stefan Robertson , Mintek, South Africa
Julio Romero, Universidad de Santiago de Chile
Javier Ruiz-del-Solar , Universidad de Chile
Scot Sandoval , Freeport-McMoRan Copper & Gold Inc., usa
Ruberlan Silva , Vale, Brazil
Luis Sobral , Centre for Mineral Technology, cetem, Brazil
Andrs Soto , Universidad Mayor, Chile
Clauson Souza , Federal University of Minas Gerais, Brazil
Mara Elisa Taboada , Universidad de Antofagasta, Chile
Luis Alberto Texeira , Pontificia Universidade
Catlica do Rio de Janeiro, Perxidos do Brasil
Csar Ugarte , Hatch, Peru
Petrus Van Staden , Mintek, South Africa
Diego Verdejo , Antofagasta Minerals, Chile
Jacques Wiertz , Universidad de Chile
Rodrigo Zambra , Cytec, Chile
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In the last three decades the role of hydrometallurgy has changed. What started as a secondary process alternative is now recognized as a primary option with key advantages. Hydro-processes are able to treat lower quality minerals, reduce the environmental impact of mining and recovery processes significantly, and require lower initial capital costs thus giving opportunities to small and medium sized producers.
However, as an established technology further growing faces new challenges. Complex ore mineralogy, including lower grade materials, forces us to look for continuous improvement in chemical processes. It is challenging to move over the standard operation and force continuous innovation cycles to adapt mineral processing to new conditions.
Another critical limitation is water availability. The intensive use of sea water shows new challenges and opportunities. The requirement to increase water reuse and recycling is now not only an environmental responsibility but also a cost factor. Increasing water cycling produces an increase in yield but impurities accumulate as a side effect. New process conditions should be faced and the proper forecast is a key to sustain the operation standard.
Thirdly, we observe that the role of hydrometallurgists has changed in recent years. Ones initial role preparing flow sheets and balances has been superseded by new responsibilities. Safety management, environmental responsibility, operations and human resources management, risk assessment, and finances appear more often. The traditional academic curriculum for mining, metallurgy and chemical professionals should be critically analyzed to include new time requirements. Limitations are observed not only with regards to the availability of qualified professionals but also in their initial toolkit of abilities.
Global markets have given us a very good opportunity to grow. However, we are now facing the instability and uncertainty associated with the European markets. The normal reaction of shareholders is to contain production costs to be more competitive. It is our challenge to support the innovation cycles despite limits in resources. Crisis periods are especially fertile for creativity and innovation.
Foreword
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Hydroprocess 2013 is an opportunity to look over these and other important challenges in the industry for the coming years. Here we will share our positive results, critical opportunities and foster coming dreams. Certainly we are discuss-ing the state of art in the aqueous processing industry, and we feel proud to be part of it every year.
Many thanks and welcome to you all.
Gabriel Meruane Naranjoch a i rHydroprocess 2013 | 5th International Seminar on Process Hydrometallurgy
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The realization of the 5th International Seminar on Process Hydrometallurgy is the outcome of great efforts and special dedication from all those involved. This seminar provided an excellent opportunity to work with many renowned professionals and researchers from different countries who have selflessly collaborated with us. Hydroprocess 2013, held from July 10 - 12, 2013 at the Sheraton Hotel in Santiago, Chile, is effectively the fifth in a series of interna-tional seminars on Process Hydrometallurgy initiated in 2006 by Gecamin.
Undoubtedly, this seminar has become the site of an international forum where all professionals and executives involved in Hydrometallurgy can analyze and discuss innovations and developments concerning the liquid processes of ores and materials involving the use of aqueous chemistry and physics. The papers presented in these proceedings of the fifth version of Hydroprocess speak of a consolidated seminar given the important assortment of technical subjects covered and the number of enterprises and countries represented.
As was defined in the initial call, the main objectives of this seminar are to (i) learn about innovations and developments in the hydrometallurgical processing of metals including valuable metals, non-metal compounds and industrial minerals, (ii) identify the best practices and technologies used in hydrometallurgical plant operation and design, and (iii) fortify an international network of collaboration and exchange between professionals related to hydrometallurgy.
This book contains 45 abstracts written by delegates from 11 different countries. The conference has been organized by area of interest, including: Plenary presentations (2); Base metals hydrometallurgy (12); Cyanidation, leaching and recovery of gold (6); Solvent extraction and ion exchange (7); Electrometallurgical processes and electrochemistry (7); Bioleaching pro-cesses (5); Modeling and optimizing hydrometallurgical operations and circuits (5); and Hydrometallurgical processes for producing salt and non-metals compounds (1).
I would like to thank all those whose efforts have helped in making Hy-droprocess a success. Thank you to the authors and their organizations for submitting papers; to all the technical experts, for sharing their expertise,
Preface
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dedicating valuable time correcting the articles, and for providing insightful comments thus enhancing the quality of this publication and the standard of the seminar. Finally, I would like to thank all the Gecamin personnel for their efforts in ensuring all the goals proposed for the seminar were successfully achieved.
Fernando Valenzuelat e chn ic a l c o or d i n at or a n d e d i t orHydroprocess 2013 | 5th International Seminar on Process Hydrometallurgy
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The Organizing Committee acknowledges with gratitude the efforts of all the authors for contributing a large variety of high quality, detailed and in-novative papers to the technical program. We also would like to thank the reviewers, Montana Tech of the University of Montana, the employees from Gecamin, and all those involved in the creation of these proceedings for their assistance. The support of the Organizing, Advisory and Technical Committees has been greatly appreciated, as has been the support of the Hydroprocess 2013 Chair, Co-Chairs and the Chairs of the technical sessions.
The Organizing Committee also wishes to thank the following sponsors (as of June 7, 2013 in alphabetical order) for their generous support:
Gold : BASF, GEA Westfalia, Inppamet and SNF FloMin
Silver : BTA, Cytec, Metalex, Outotec, RSR Anodes and Verne SpA
Social : SQM
Official Material : Arcadis and BASF
Institutional Partners : Consejo Minero, Chile; Instituto de Ingenieros de Minas del Per; Servicio Nacional de Geologa y Minera (serNAGeoMiN), Chile; and Sociedad Nacional de Minera (soNAMi), Chile
Official Media : AreaMinera, Chile
Media Partners : Ecoamrica, Chile; Elsevier, United Kingdom; Infomine, Canada; and Mining Engineering, UsA.
Finally, we would like to thank all the delegates who attended the seminar and exchanged their valuable knowledge and expertise, thus contributing to the great success of this 5th edition of the International Seminar on Process Hydrometallurgy, Hydroprocess 2013. We are looking forward to seeing you all again during the next version of Hydroprocess, in the year 2014.
Executive Organizing CommitteeHydroprocess 2013 | 5th International Seminar on Process Hydrometallurgy
Acknowledgements
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Plenary presentations
ChAP. 1
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Hydrometallurgical processing of gold is almost exclusively accomplished with cyanidation. However, cyanidation has been attacked from environmental, health and safety aspects due to cyanide toxicity, poor tailings management, and desires to eliminate open pit mining. Although these attacks are predomi-nantly unwarranted, they have led to an increase in studies about cyanide alternatives, particularly thiosulfate. Thiosulfate leaching of gold is similar to cyanidation; however, gold recovery from thiosulfate solutions is not possible with conventional carbon adsorption. This necessitates the use of more ex-pensive resin adsorption/ion exchange processes to recover the gold from thio-sulfate solution. In order to make gold recovery cheaper as well as cost-competitive against cyanidation, a novel non-resin technology is described and character-ized. In this technology, activated carbon is impregnated with cyano-cuprous species which allows for high gold extraction followed by traditional elution. Elution efficiency depends on how much copper is present with the gold on the activated carbon surface. Optimal conditions for extracting and eluting the gold were identified from computational models developed from statisti-cally designed experiments. The impregnated activated carbon technology has been patented because it makes thiosulfate leaching cost effective compared to cyanidation by replacing resin adsorption/ion exchange; however, the tech-nology needs to be tested on both a continuous and large scale.
Impregnated activated carbon for gold extraction from thiosulfate solutions
Courtney Young. Montana Tech, USA
Nick Gow. FLSmidth, USA
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INTRODUCTION
During cyanidation, gold (Au) is reacted with cyanide (CN-1) and oxygen (O2) causing its oxidation
and dissolution by forming cyano-aurous complex [Au(CN)2-1] and hydroxide (OH-1) (Marsden &
House, 2006). The process was patented by MacArthur (1916) and was conclusively shown to be
electrochemical in nature by Kudryk & Kellogg (1954) but was not combined with carbon
adsorption for recovering the Au from solution until 1970 (Marsden & House, 2006). If copper (Cu)
is present, it will leach via the same mechanism and form one of four cyano-cuprous species
[CuCN, Cu(CN)2-1, Cu(CN)3-2 and Cu(CN)4-3] depending on the pH (Adams, 1994). Because Cu is
usually present in larger amounts than Au, cyano-cuprous species result in higher concentrations
and compete more with cyano-aurous for the adsorption sites on the activated carbon (Jay, 2000).
Using cyanide toxicity and poor tailings management as excuses (Young, 2001), political groups
have attacked cyanidation to eliminate mining, a foundation of modern society. In response,
researchers in the mining industry have examined alternatives to cyanide leaching including, but
not limited to, chlorine, bromine, ammonia, nitric oxide, thiourea, thiocyanate and thiosulfate
(Young, 2001). Based on its leaching mechanism being similar to that of cyanide including the use
of a neutral pH, thiosulfate leaching is the leading contender even though various chemicals are
needed to stabilize the thiosulfate by preventing polythionate formation. In this regard, Cu has
been found to be the most effective and additionally shown to act as a catalyst (Marsden & House,
2006). Unfortunately, Au recovery from thiosulfate solution can only be accomplished by ion
exchange with resins, which are inherently expensive and suffer from fouling with polythionates.
However, Young et al. (2005) conceived an activated carbon technology that shows great promise
for making thiosulfate leaching cheaper and therefore cost-competitive against cyanidation.
It is well known that activated carbon, by itself, has no affinity for Au thiosulfate (Marsden &
House, 2006) and must be pretreated in order to recover Au from thiosulfate solution. Knowing
that Cu is needed as a catalyst as well as a thiosulfate preservative, Young et al. (2005) suggested
using Cu to impregnate the activated carbon with cyano-cuprous by chemisorption forming
Cu(CN)2-1 ads in order for the following metal exchange reaction to take place:
Au(S2O3)2-3 + Cu(CN)2-1 ads Au(CN)2-1ads + Cu(S2O3)2-3 [1]
and thereby extract the Au from thiosulfate solution. In this paper, the development of this novel,
non-resin technology is reviewed from its proof of concept (Gow, 2006) at low adsorption density of
Cu(CN)2-1 to confirmation (Melashvili, 2009) at high adsorption density and subsequent elution.
Results have been presented in detail elsewhere (Young et al., 2012) but are reviewed here along
with, for the first time, a brief discussion on cost.
CYANO-CUPROUS CHEMISORPTION
Experiments of cyano-cuprous chemisorption on activated carbon were conducted at room
temperature (20C) and elevated temperature (40C) as well as variable pH (9-12). Adsorption
densities averaged near 15,000 g Cu/g C which equates to approximately 1,500 opt Au assuming
Cu and Au exchange in a 1:1 molar ratio according to Reaction 1. Because carbon adsorption
26
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during cyanidation yields Au loadings near 300 opt (Marsden & House, 2006), this would more
than satisfy industrial needs. Furthermore, adsorption densities were found to increase with
increasing temperature and therefore to be endothermic yielding maxima of approximately 8,000
g Cu/g C at room temperature (20C) and 20,000 g Cu/g C at elevated temperature (40C) at pH 9.
However, these values were found to increase moderately by approximately 2,000 g Cu/g C at pH
12. The studies were conducted using caustic (NaOH) to adjust the pH and therefore in the absence
of lime [Ca(OH)2] which eliminates Ca+2 adsorption and therefore the formation of ion pairs
(MacDougall et al., 1980). This was done to keep the chemistry of the system as simple as possible
and thereby enable thermodynamic calculations to verify that cyano-cuprous chemisorbs.
After converting the adsorption densities to surface coverages, fitting the resulting values to
Langmuir Isotherms, and using the isotherms to determine reaction constants according to the
Stern-Langmuir Equation, free energies of adsorption (Gads) were determined and then used to calculate enthalpies (Hads) and entropies (Sads) of adsorption as well using the Clausius-Clapeyron Equation and the fundamental thermodynamic expression, respectively (Young 1994).
Results presented in Table 1 show that Gads at 20C and 40C average -27.4 and -32.6 kJ/mol, respectively. Because Gads are negative and Hads are positive, adsorption is both favorable and endothermic. Furthermore, because the free energies are significantly lower than -20 kJ/mol,
adsorption is confirmed to be chemisorption.
In order to optimize chemisorption densities, tests were conducted via full, two-level, factorial-
designed experiments using Stat-Ease software by systematically varying 4 factors between low
and high values, initial Cu concentration (0.001 or 0.1 M); pH (9 or 12); time (1 or 5 hours); and
temperature (20 or 40C), and using mid-point determinations (0.01 M, pH 10.5, 3 hours and 30C).
Resulting models were used to construct 3-dimensional plots to clearly illustrate the conditions that
yield maximum chemisorption. Results were found to be relatively independent of time and were
higher at increased temperature (40C) verifying its endothermic behavior. Taking cross-sections of
the plot at constant pH yields adsorption isotherms similar to those described earlier but as a
function of surface coverage as opposed to adsorption density. Clearly, the optimal conditions for
cyano-cuprous chemisorption on activated carbon occur at shorter time (1 hour), higher
temperature (40C), higher pH (pH 12), and higher cyano-cuprous concentration (0.1M).
Table 1 Thermodynamic Data for Cyano-Cuprous Chemisorption on Activated Carbon
Temperature (C) Gads (kJ/mol) Hads (kJ/mol) Sads (J/mol/K)
20 @ pH 9 -26.8 41.02 223.8
40 @ pH 9 -31.4
20 @ pH 12 -28.1 55.65 276.8
40 @ pH 12 -33.8
GOLD-COPPER ION EXCHANGE
Impregnated carbon prepared under conditions where minimum chemisorption would occur in
anticipation that they would be favored by industry: 1 hour, 20C, 0.001M and pH 9. It was then
contacted with 20 ppm Au thiosulfate solution and characterized with Raman Spectroscopy to see if
the proposed reaction products could be observed (see Reaction 1). Raman spectra of impregnated
27
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carbon before and after contact with Au cyanide are shown in Figure 2. Raman shifts near 2100 cm-
1 in Figure 2a are due to cyano-cuprous with the band at 2118 corresponding to dicyano-cuprous
[Cu(CN)2-1] and those at 2096 and 2127 cm-1 representing tricyano-cuprous [Cu(CN)3-2] (Young et al.,
2008). These peaks are slightly shifted from their aqueous counterparts at 2137, 2094 and 2108 cm-1,
respectively (Lukey et al., 1999). Likewise, Raman band at 2227 cm-1 in Figure 2b are due to cyano-
aurous that formed at the activated carbon surface. It is slightly shifted from the 2239 cm-1 band for solid KAu(CN)2 (Parker et al., 2008). It is understood that, as the pH increases, dicyano cuprous
will convert to tricyano cuprous with excess cyanide present (Marsden & House, 2006).
Consequently, it is reasonable to conclude that increased chemisorption at increased pH is due to
the additional tricyano cuprous available.
Figure 1 3-dimensional plot showing the effect of cyano-cuprous concentration and pH on surface coverage
() at 40C after 1 hour of chemisorption (Young et al., 2012)
Surfa
ce Co
ver
age
()
9.00
9.75
10.50
11.25
12.00
0.001 0.026
0.051 0.075
0.100
0.490
0.617
0.745
0.873
1.000
pH
Initial [Cu]
28
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Figure 2 Raman spectra of activated carbon showing (a) the appearance of cyano-cuprous bands following
impregnation and (b) their disappearance along with the appearance of the cyano-aurous band following Au
extraction (Young et al., 2012)
Because all of the cyano-cuprous bands disappeared following contact of the impregnated carbon
with Au thiosulfate solution, the Au must have ion exchanged with both of the cyano-cuprous
species, resulting in the formation of cyano-aurous species. Clearly, Reaction 1 is confirmed but the
results also suggest that the reaction mechanism should also include tricyano-cuprous:
Au(S2O3)2-3 + Cu(CN)3-2 ads Au(CN)2-1ads + CN- + Cu(S2O3)2-3 [2]
As with Reaction 1, it is assumed in Reaction 2 that the Cu and Au exchange in a 1:1 molar ratio. To
test this, impregnated carbon was prepared under various conditions to yield different cyano-
cuprous chemisorption densities and then contacted with Au thiosulfate solutions of varying
concentrations (5-50 ppm). Resulting Au concentrations were measured by ICP. Differences
between initial and final Au concentrations were used to calculate the amount extracted. Results
showed that, when the molar ratio of Cu on the impregnated carbon to Au in solution (Cu:Au) was
greater than approximately 1.5:1, Au extraction efficiencies of 100% were observed. Cu
concentrations were also measured but results were indeterminant yielding ratios ranging from 0:1
to 1:1, likely caused by precipitation when excess thiosulfate was not present to keep it solubilized.
Optimization tests of Au extraction via its ion exchange with Cu were also conducted with Stat-
Ease software using full two-level, factorial-design. In this case, three factors were systematically
varied and midpoints were examined: time (1 or 4 hrs), pH (10 or 12) and Au concentration (10 or
20 ppm). The temperature was fixed at 20C and the cyano-cuprous impregnation was established
at approximately 20,000 g Cu/g C so that Cu:Au ratios at the surface would not exceed either 2:1
or 1:1 assuming complete Au extraction. All variables were found to be important but Au extraction
1500 2000 2500 3000
Raman Shift, cm-12050 2100 2150
a) Cu-CN Bands Appear
b) Au-CN Band
Appears
Cu-CN Bands Disappear
29
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at high Au concentration was slower. The 3-dimensional plot in Figure 3 shows the effect of time
and pH on Au extraction at the high Au concentration. It indicates that Au extraction is a maximum
at high pH and long times. Projecting the plot onto the base (i.e., pH-Time plane) yields contours of
which five are shown and three are labeled 90, 70 and 50%. For example, the conditions needed to
achieve >90% extraction range from pH 10.5 and 4 hours to pH 12 and 2.5 hours. Clearly, in this
case, the contours allow the conditions to be seen easier.
Figure 3 3-dimensional plot showing the effect of time and pH on Au extraction by impregnated carbon from
Au thiosulfate solution at 20 ppm (Young et al., 2012)
GOLD ELUTION
Au-loaded, impregnated carbon produced in this manner was eluted using the AARL method
(Marsden & House, 2006) and thereby pretreated with 2% NaCN and 1% NaOH solution for an
hour, transferred to a water-jacketed column controlled at 97C, and eluted with distilled water.
Resulting eluant was collected as a function of time, reported in bed volumes (BV), and analyzed
for free cyanide by ISE and Au and Cu concentration by ICP. Example profiles and a Au recovery
curve are shown in Figure 4. Cu is being eluted somewhat selectively which is common in
cyanidation circuits (Marsden & House, 2006). It was not until 5 BVs have passed that the Au
concentration became significant. After approximately 15 BVs, Au concentrations reached a
maximum of 420 mg/L (ppm) which is comparable to cyanidation circuits as well. In this case, Au
recovery reaches a maximum of 83% at 70 BVs but other tests ranged from lows of 5% when Cu
was still present in significant amounts on the surface to 100% when relatively no Cu was on the
surface. Clearly the best results were obtained at low chemisorption densities of cyano-cuprous
such that, after Au extraction, relatively no Cu was left on the surface. However, if some Cu did
remain, it could be selectively eluted or separated by conventional smelting technology.
Au
Ex
trac
tio
n (
%)
10.0
10.5
11.0
11.5
12.0
1.0
1.8
2.5
3.3
4.0
50
64.8
79.5
94.3
109
pH Time
90%
70%
50%
30
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Figure 4 Elution (a) and recovery (b) of Au from impregnated activated carbon as a function of bed volume at
97C using distilled water, 2% NaCN and 1% NaOH according to the AARL method (Young et al., 2012)
FLOWSHEET DESIGN AND COST ANALYSIS
Figure 5 shows a conceptualized flowsheet for thiosulfate heap leaching as determined in this study
and compares it to cyanidation. As can be seen, the two processes are virtually identical. In both
cases, a leachant is added to the heap through which it trickles to leach the Au. The pregnant
solution is then extracted of its Au by adsorption onto activated carbon such that the barren
solution is recycled back to the heap and the loaded carbon is sent to stripping. At this point,
because the carbon contains an adsorbed cyano-aurous species, both processes include stripping
with conventional elution technology followed by electrowinning onto steel wool and eventually
smelting to produce Au dore. Stripped carbon will then be reactivated and recycled back to the
carbon columns, and raffinate from electrowinning will be recycled back to stripping. Steps for
carbon reactivation are not shown in these flowsheets.
a) b)
31
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Figure 5 Flowsheets for heap leaching and Au recovery by (a) cyanide and (b) thiosulfate using the novel,
non-resin, activated carbon process with cyano-cuprous impregnation (Young et al., 2012)
Clearly, the envisioned thiosulfate process uses the same unit operations as cyanidation. The cost
difference between the two heap leaching operations will therefore be predominantly due to the
impregnation step as well as the consumption of chemicals throughout. The impregnation step will
require conditioning tanks and pumps beyond that needed for cyanidation but capital and
operating costs for these items will be minimal. Although lime/caustic consumption will increase
due to the impregnation step, thiosulfate leaching (at pH 8) has less consumption than cyanidation
(at pH 10.5); hence, the overall consumption rates will be similar. Assuming the leachants (cyanide
vs thiosulfate) have the same costs, the only difference will be the cost for cyano-cuprous reagent
which is available for the plating industry at moderate costs near US$6/kg and in large quantities
on the order of MTPD. With chemisorption densities near 15,000 g Cu/g C, cyano-cuprous costs
will also be negligible. It is additionally noted that, because of the impregnation step, the Au dore
product could become contaminated with Cu. This could be prevented by selective elution, as
mentioned earlier, and/or by the proper management of the smelting step. If Cu is present in the ore
either process may be pursued and consequently these costs are not considered as well.
CONCLUSIONS
A novel carbon adsorption technology for extracting Au from thiosulfate solutions has been
developed and shows promise at becoming a cost effective method allowing thiosulfate leaching to
become economically competitive against cyanide leaching. Unless impregnated, activated carbons
will not adsorb Au thiosulfate. However, by first adsorbing cyano-cuprous species onto the carbon,
Au can be extracted from thiosulfate solution. Thermodynamic analysis of the adsorption data
a) b)
32
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verified that the adsorption process was chemisorption and endothermic. Factorially-designed
experiments verified that maximum cyano-cuprous adsorption occurred at high pH and
temperature and verified the tests. Similar tests conducted for Au extraction showed the Au
followed the Cu. Raman spectroscopy revealed that increased adsorption with increasing pH was
due to both di- and tri-cyano-cuprous and the resulting adsorbed Au species was likely cyano-
aurous [Au(CN)2-1]. Flowsheets similar to current cyanidation processes were designed and could
be employed immediately. At question is whether Au and Cu separation can be done in the process
or in subsequent smelting and refining processes. Based on these promising results, a patent has
been granted; however, the technology needs to be tested on a continuous basis.
ACKNOWLEDGEMENTS
Many thanks are extended to Newmont Mining Corporation for their support of this project as well
as the patent granted in the U.S.A. and pending in Canada and Australia.
REFERENCES
Adams, M.D. (1994), Removal of Cyanide from Solution using Activated Carbon, Mineral Engineering,
7(9):1165-1177.
Gow, R.N. (2008), Pretreatment of Activated Carbon for Gold Adsorption from Thiosulfate Leach Liquors,
Thesis, Montana Tech, Butte, MT.
Jay, W.H. (2000), Copper Cyanidation Chemistry and the Application of Ion Exchange Resins and Solvent
Extractants in Copper-Gold Cyanide Recovery Systems, In: Proceedings of Alta 2000 Conference,
Adelaide, Australia.
Kudryk, V. and H.H. Kellogg, (1954), Mechanism and RateControlling Factors in the Dissolution of Gold in
Cyanide Solution, Trans. AIME J. of Metals, 541-548.
Lukey, G.C., van Deventer, J.S.J., Huntington, S.T., Chowdhury, R.L., Shallcross, D.C. (1999), Raman Study on
the Speciation of Copper Cyanide Complexes in Highly Saline Solutions, Hydrometallurgy, 53:233-244.
MacArthur, J.S. (1916), Discovery of Cyanidation, Mining & Scientific Press, London.
MacDougall, G.J., Hancock, R.D., Nicol, M.J., Wellington, O.L. and Copperthwaite, R.J. (1980), The Mechanism
of the Adsorption of Gold Cyanide on Activated Carbon, J. S. Afr. Inst. Min. & Metall., 80: 344-356.
Marsden, J. and I. House (2006), The Chemisty of Gold Extraction, Ellis Horwood Publishers, New York.
Melashvilli, M. (2009), Gold Recovery from Thiosulfate Solutions using Activated Carbon Pretreated with
Copper-Cyanide: Mechanism, Quantification and Elution, Thesis, Montana Tech, Butte, MT.
Parker, G.K., Gow, R.N. and Young, C.A. Twidwell, L.G. and Hope, G.A. (2008), Spectroelectrochemical
Investigation of the Reaction between Adsorbed Cuprous Cyanide and Gold Thiosulfate ions at
Activated Carbon Surfaces, In: Hydrometallurgy 2008: Proceedings of the 6th International Symposium
Honoring Robert S. Shoemaker, C.A. Young, P.R. Taylor, C.G. Anderson and Y. Choi (Editors), SME,
Littleton, CO.
Young, C.A. (1994), Characterization of Adsorbed Oleate at Calcite and Flourite Surfaces by Infrared and
Raman Spectroscopy, Dissertation, University of Utah, pp. 287.
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Young, C.A. (2001), Cyanide: Just the Facts, in: Cyanide: Social, Industrial and Economic Aspects, C.A. Young, L.G.
Twidwell and C.G. Anderson (Editors), TMS, Warrendale, PA.
Young, C.A., Gow, R.N. and Melashvilli, M. (2011), Method for Aqueous Gold Thiosulfate Extraction Using
Copper Cyanide Pretreated Carbon Adsorption, U.S. Patent Publication Number US 20110259148 A1.
Young, C.A., Gow, R.N., Melashvilli, M. and LeVier, M. (2012), Impregnated Activated Carbon for Gold
Extraction from Thiosulfate Solutions, In: Separation Technologies for Minerals, Coal and Earth
Resources, Proceedings of the Roe-Hoan Yoon Symposium, C.A. Young and G.H. Luttrell (Editors),
SME, Littleton, CO.
Young, C.A., Gow, R.N., Parker, G. and Hope, G. (2008), Cu-Cyanide Adsorption on Activated Carbon, In:
Hydrometallurgy 2008: Proceedings of the 6th International Symposium Honoring Robert S. Shoemaker, C.A.
Young, P.R. Taylor, C.G. Anderson and Y. Choi (Editors), SME, Littleton, CO.
Young, C.A., Twidwell, L.G and Hope, G. (2005), Recovery of Gold from Thiosulfate Leach Liquor Using Activated
Carbon, CAST Proposal, Montana Tech, Butte, MT.
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The leaching process started in Cerro Verde in the late 1970s. At that time, the leach pad operating criteria centered around metallurgical and production parameters only. Little or no consideration was given to slope stability, phreatic levels or permeability issues. Later on, when new leach pads were started up in the early 1990s, unusual slope stability issues began to take place; however, these did not pose risks to the operation because overall pad heights were small compared to todays permanent pads. In 1996, the Crush Leach Pad 4-A was engineered and constructed using the best technology available at the time. The design considered twenty 4-meter lifts, which quickly became 6-meter and then 8-meter lifts with improvements in ore agglomeration technology, forced air injection and larger and taller stacking equipment. Recently, Pad 4-A has reached its maximum capacity; twenty lifts have been stacked at an average of 5.5 meters per lift. The metallurgical optimization, coupled with changes in ore quality, entailed geotechnical challenges that led to modified variable irrigation rate schemes, ore stacking, lift rinsing practices, dewatering and phreatic level controls. Lessons learned at Pad 4-A, described in this paper, have been taken into consideration in the engineering and construction of the new Crush Leach Pad 4-B. This paper also describes the geotechnical best practices and design considerations implemented at this new leach pad.
Helbert Galdos, Javier Guevara and Arnaldo Saavedra. Sociedad Minera Cerro Verde S.A.A ., Peru
Geotechnical lessons learned from the operation of Cerro Verdes Crush Leach Pad 4-A
35
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INTRODUCTION
The main purpose of this paper is to describe the experience gained by Sociedad Minera Cerro
Verde S.A.A. (SMCV) in the geotechnical control of permanent leach pads of crushed and
agglomerated mineral. Proper control is critical to the slope stability of leach operations. The
phreatic levels inside the heaps must be controlled as they can seriously affect safety, the
environment, metallurgy and the operation. Nevertheless, they are not always given the attention
which they deserve.
On the other hand, the geotechnical control of leach heaps has been improving. It has become more
complex and elaborate as the leach heaps, platforms or pads, have grown in size. Furthermore,
governmental and internal mining company regulations have been changing as part of more
demanding risk management programs.
In general, it is clear that the geotechnical control of leach heaps has evolved in a simple, almost
always reactive manner, instead of in a more elaborate preventative way. Experience has taught
that it is much more convenient to incorporate geotechnical controls from the engineering stage
than when the leach platforms have already been started and have several layers of mineral being
treated.
The first part of this paper briefly describes the leach operation at SMCV, then the geotechnical and
operational problems encountered at the leach heap of crushed and agglomerated Pad 4-A will be
described, along with the corrective measures implemented. Next, the geotechnical controls
implemented at Pad 4-A as part of a preventative program will be discussed. Finally, the paper will
show the application of the experience obtained at Pad 4-A for the engineering, construction and
operation of the new leach platform, Pad 4-B, which began operations in December 2012. All of
which were intended to guarantee, from the initial design, the stability of the heap, and its
operational continuity to avoid having to implement much more expensive corrective measures
later.
The leach process at Sociedad Minera Cerro Verde S.A.A.
At Sociedad Minera Cerro Verde, secondary sulfide and transitional coppers are leached. The
leaching of low-grade (ROM) minerals is carried out at the leach heaps MegaPad ROM and Pad 1X.
On the other hand, the leaching of high grade mineral, previously crushed and agglomerated with
sulfuric acid, takes place at the heap Pad4-A and, more recently, at Pad 4-B.
Both processes involve multilayer permanent heaps of the valley-leach type, i.e. the mineral is
stacked up until it reaches the storage capacity of the pad. The heaps at Cerro Verde are unique in
that they are built in small ravines, that are filled until they reach the height of the platform and
then an upright pyramid is formed by continuing to stack the mineral until the maximum area of
the platform is reached. Thereafter, the pyramid is formed with ever decreasing stack area. The
total height of Pad 4-A is 110 meters with 20 layers of mineral and its slopes have global gradients
of 2.5H : 1V.
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Operational and geotechnical problems of leach heaps
The most common operational, metallurgical and geotechnical problems found at the permanent
heaps are as follows:
Operational problems
The collapse of the leach solution collection pipes and/or their connections occurs due to lack of
quality control during installation, or while the protective geo-membrane material (overliner) is
being put in place, or by the uncontrolled movement of heavy equipment such as tractors or
conveyor belts. These collapses significantly reduce the drainage capacity of the system,
producing an increase in the phreatic level inside the pad, reducing the factor of safety and
increasing the risk of liquefaction of the saturated mineral and destabilization and collapse of
the slopes.
Leakages from the pipes near the slopes affect the geometry of the slopes.
Removing leached material from the bases of the slopes, for example, to open/maintain access
routes to the leach heaps, weakens the base of the slope.
Increasing the rate of irrigation without bearing in mind the limit of permeability of the material,
or the settling of the underlying material with each layer placed on top.
Geotechnical problems
Internal erosion and piping due to the concentration of fluid at the base of the slope. In some
cases, a cavern is developed which grows towards the interior of the heap.
Localized instability of a side (bank) due to an increased phreatic level near the slope.
Interruptions to vertical flow caused by the presence of layers of low permeability due to their
high clay contents, badly scarified interfaces (badly carried out drainage and ripping).
The presence of craters (sink holes) in the surface produced by damaged collection pipes
followed by internal erosion.
Surface channels caused by rain, flow from broken pipes, or the overflow of an area with
ponded solution resulting in superficial slipping on sides or banks.
Internal canalization of the solution through high-permeability zones (due to the presence of
highly permeable or segregated material) and lateral discharge over the perimeter.
Metallurgical problems
Excessive increase in clay content (montmorillonite and kaolinite) and high percentage of fines
(below mesh 100) in the agglomerated mineral stacked on the leach heap.
Low quality agglomerated mineral due to insufficient control during agglomeration and mineral
transportation to the leach platforms.
Pooling (ponding) of the irrigation solution due to the presence of mineral with high-clay and
and content and ore fines, which generate areas of very low permeability.
37
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Solutions implemented
The operational, metallurgical and geotechnical solutions implemented were the following:
Operational solutions
The localizing of segments of collapsed main drainage collection pipes with the help of infrared
cameras mounted on small remote-control vehicles moving inside the pipes, or by following the
behavior of craters or sink holes on the irrigated surface.
Excavating until the collapsed main pipes are located, replacing the damaged sections and
replacing the removed material, increasing its permeability by mixing it with coarser material.
Blending of minerals in the mine to reduce the concentration of clays and fines being fed to the
crushing and agglomeration plant.
Inspection and periodic replacement of the main and auxiliary high-density polyethylene
(HDPE) pipes in the irrigation system, which show damage due to a reduction in their thickness
caused by handling or transportation, or excessive contraction and expansion due the daily
fluctuations in ambient temperature. The latter involves the use of ultrasound techniques to
evaluate the integrity of the fused unions of the HDPE pipes.
Geotechnical solutions
The installation in the bases of the slopes of banks of horizontal drains of 38 and 102 milllimeters
of exterior diameter, 100 and 150 meter long, respectively. In the right number and length, these
horizontal drains help to reduce the phreatic levels near the slopes of the leach heaps.
Reconstruction of slopes affected by the incorrect removal of material from the toe of the slope.
The latter can be aided by analysing the stability of the slope before and after the reshaping
work to ensure that the minimally acceptable geotechnical safety factors have been maintained
for static and post-seismic conditions.
The construction of small rock buttresses or retaining walls at the base of unstable slopes. This
method stabilizes the slope and canalizes the solution so that it can be drained, which avoids a
localized increase in ore moisture and saturation.
The installation of French drains to capture and evacuate the pools of solutions which can
accumulate on the surface near the base of the slope. These consist of ditches excavated in the
gravel, which are refilled with selected crushed stone (filter), which contains a perforated or
slotted pipe. The pipe must have a slope of at least 1% and operate at full flow. Before the end of
discharge, the slotted pipe will be replaced by a blind pipe and a low-permeable plug put in
place.
The installation of banks or batteries of vertical dewatering wells with exterior diameters of
between 204 and 356 millimeters of perforated PVC pipe to lower the phreatic levels inside the
leach heap. These wells have submergible pumps, pressure sensors (transducers), and low-level
switches to optimize the recovery of the solution retained inside the heap due the loss of
permeability of the mineral.
38
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Stabilization of the craters (sink holes) by refilling with gravel or highly permeable mineral with
particle sizes of from 102 to 204 millimeters; the repaired area is then covered with layers of non-
woven geotextil and geonet to stop the sink hole from affecting underlaying layers.
Repairing of channels in the slopes of the leach heaps, caused by rain or by the spillage of
solution, which result in erosion. The loose material is removed (as it has a high content of fines)
and is replaced by material of an appropriate size distribution, which is wetted and compacted
layer by layer to avoid further erosion.
Stability buttresses are constructed at the base of the principal slopes of the leach heaps, which
due to the high phreatic levels or deterioration in the angle of design of the slope, do not meet
the minimum factors of safety. The main purpose of a buttress is to increase vertical pressure
and to keep the base of the slope in place (only a localized effect). Likewise, as a side-effect, it
strengthens shear resistance when potential faulty zones pass through it. Buttresses are made
from leached material, rubble or waste material from the mine. The material is checked, wetted
and compacted in horizontal layers. Its weight is crucial. These buttresses contain filter zones or
drains of highly permeable gravel to lower or eliminate the phreatic level to ensure their long
term slope stability.
Metallurgical solutions
Optimization of the quality of the agglomerated mineral, ensuring the correct level of humidity,
dosage of sulphuric acid during the agglomeration, transportation and stacking stages of high-
grade mineral. For the above, an instrument has been designed, which by measuring the
conductivity of the agglomerated mineral can optimize both the dosage of leach solution and
acid for curing of the mineral. It should be mentioned that an excessive dosage of acid
deteriorates the matrix of the rock of the mineral.
A widening (coarsening) of the size distribution curve of crushed mineral to reduce the level of
fines in the crushing circuit. This method is adopted after ensuring that an increase in ore size
would not reduce copper recovery any more than that caused by the presence of clays and fines
due to damage to or compaction (settling) of the mineral with every new layer stacked on the
permanent pad.
Implementation of geotechnical controls
The geotechnical controls of a leach heap are by nature almost always preventative, focused on
monitoring the phreatic levels, the surface and depth movements of key slopes, the vertical
pressure on the base of the slope and the settling of the mineral. Alternatively, the settling which
takes place between the layers can be monitored which would allow changes to the dry density and
porosity of the material to be controlled.
If the global hydraulic conductivity of the leached material is to be evaluated, a large-scale
pumping test should be carried out, which would obtain much more realistic results than localized
testing, an example is provided by the Lefranc tests which are made inside perforations. Another
alternative to measure hydraulic conductivity, but only locally, are the water addition (slug) tests
which take place inside an open-tube piezometer. These tests can also determine whether the
instrument can detect, over time, losses in permeability of the surrounding material due to
deterioration (decrepitation) or aging of the mineral.
39
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If the leach heap contains gravel which is likely to suffer from liquefaction, seismographs should be
installed to register important seismic events and to correlate these to any resulting damage to the
heaps. A fixed seismograph should be installed on solid rock and a mobile one set up on the crest of
the heap to analyze signal amplification and the filtration of frequencies.
The geotechnical controls used at SMCV are as follows:
a) Periodical evaluations of slope stability
The periodical evaluations of stability analyze the stability of the heap slopes using the limit
equilibrium method. This analysis is bi-dimensional and as part of the hypothesis, the surface is
considered to act like a rigid solid. This method does not measure movements, only the resulting
safety factor. For a given surface, which is likely to suffer a fault, this method divides the block
into vertical slices, calculates and compares the resistance forces with the destabilization forces.
If the forces which are available to withstand movement are greater than the forces which
destabilize the slope (FS1), then the slope is considered to be stable.
FS = (Resistance Forces / Destabilizing Forces) 1
In general, the following conditions can be analyzed in heaps: static (short and long-term),
pseudo-static, post-seismic with reduced shear resistance, and post-seismic with liquefaction.
Given the large size of the slope, local, intermediate and global faults are investigated. The
potential fault surfaces are circular, blocks or random. Each type of analysis has its
corresponding minimum recommended factor of safety, established by the industry and by
technical literature. Normally, several control sections are established and for each one, the
factors of safety are calculated, which are compared with the required minimum values. Table 1
shows the required minimum safety factors for the leach platform Pad 4-A.
Table 1 Factors of Safety Leach Heap Slope Stability
Condition Safety Factor (FOS) Notes
Short-Term Static 1.3 Only for temporary slope cut work
Long-Term Static 1.5 For all important slopes
Pseudo-Static 1.0 Not applicable as the mineral of Pad 4A below the
phreatic level will undergo liquefaction in the event of
a high magnitude seism.
Post-seismic with
degraded resistance
1.3 Not applicable as the mineral of Pad 4A below the
phreatic level will undergo liquefaction in the event of
a high magnitude seism.
Post-seismic with
Liquefaction
1.1 Normal value to control slope stability. This is the most
critical parameter to be complied.
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b) Maximum permissible phreatic levels
The maximum permissible phreatic levels are limits or threshold values beyond which it is not
safe to operate the leach heap. Below these thresholds, all the applicable safety factors are met
(static, pseudo-static and/or pseudo-seismic with liquefaction). These are established using slope
stability analysis (by the limit equilibrium method); they depend on the properties of shear
resistance of the terrain, the geometry of the slope and the phreatic level. Figure 1 shows an
example of the control of phreatic levels with respect to the maximum permissible values.
Figure 1 Comparison of Phreatic Levels with Maximum Permissible Values
c) Manual of operations
The Manual of Operations is a field document which attempts to standardize criteria, provide
instructions, procedures and recommendations to monitor and control the phreatic level inside
the leach heap by setting a series of maximum permissible operational levels. The manual
indicates the actions to be taken if these permissible limits are exceeded.
d) Prisms
These are optical instruments which facilitate the monitoring of the surface movements of the
slope in three directions; they are fixed to the terrain by a metallic tube which is embedded in a
concrete base. They can detect settling and/or bulging on the face of the slope, and are read
using electronic surveying equipment with accuracies of a few millimeters.
Geotechnical controls incorporated in the design of Pad 4B leach heap
Based on geotechnical experience acquired during the operation of the leach heap of high-grade
mineral, Pad 4-A; it was decided to include, from the engineering stage, the following elements of
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geotechnical control in the design of the new high grade ore leach platform, Pad 4-B, which was
successfully started-up in December 2012.
a) Vibrating-wire settlement sensors
This type of sensor allows continuous monitoring of the vertical deformation of the foundations
of the leach heap, due to the vertical pressure of the stacked mineral and the phreatic level. This
sensor is especially useful when the terrain of the foundations has compressible layers or there
are thick refills. Furthermore, they allow indirect measurement of geomembrane stretching or
elongation. They are normally placed under the membrane (underliner layer), either on the mass
or on the structure of the refill. They are accurate to a few millimeters.
b) Inclinometers
Inclinometers are used to measure lateral deformation of the terrain of the foundations of the
heap which are caused by deep breaches (shear surfaces). They are installed outside the heap,
either on the containment berm or on the containment wall. An inclinometer consists of a plastic
tube with special grooves in two perpendicular directions which is installed and connected to
the terrain with grout or with slurry of cement and bentonite. Readings are taken with a biaxis
electronic probe (torpedo) which registers, over 50 centimeter sections, vertical deviations of the
tube in two perpendicular directions. They are accurate to a few millimeters.
c) Vibrating-Wire piezometers
Piezometers measure the pore pressure of the fluid contained in the void spaces of the leached
material (ripios) or in gravel when they are completely full of liquid, that is, saturated (100%
degree of saturation). They are based on the vibrating-wire principle and are very accurate.
Knowing the specific density of the fluid, it is possible to calculate the equivalent height of
column of liquid (piezometric height).
d) Vibrating-wire pressure cells
Vibrating-wire pressure cells measure the total vertical pressure increase at the base of the heap
over its useful lifetime. This pressure is that of the weight of the mineral and the solution.
Knowing the height of the heap, it is possible to estimate the average wet density if required,
which is important operational information. The pressure measurements and those taken from
the foundations allow the plotting of the settling curve of the pad against vertical pressure and
hence calculate the rigidity of the foundation terrain, which is important information for future
designs.
e) The main solution collection system
The system of collection of copper pregnant leach solution (PLS) at Pad 4-B has undergone the
following improvements:
A system to collect the main solution has been installed on a cut zone of bedrock material at
the bottom of the ravine to prevent differential settlement (uneven settling), which can
decouple the pipe joints. In other words, by installation of the main collection drains on
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bedrock, and not on structural fill, the possibility of future differential settlement is
eliminated.
The principal collection pipes are interconnected which prevents the retention of solution
inside the heap due to obstruction of the collection system.
Together with the system of corrugated and perforated pipes, a system of solid perforated
HDPE collection pipes has been installed in order to ensure continued drainage if a collapse
occurs in the corrugated collection pipes.
Collection pipes have been installed inside trapezoidal ditches (canals) to generate an arc
effect in the mineral located above them and thus transfer the vertical loads of the heap
towards the sides and so reduce deformation.
f) Gravel screens
To prevent phreatic levels from exceeding those considered in the geotechnical design of the
leach, Pad 4-B has permeable gravel screens installed in the space formed by the union of toe of
the slopes of two adjacent cells. These gravel screens are installed in two sectors near the front
slope by the PLS weir upstream the PLS ponds. These gravel screens will also be installed in the
upper levels up to Lift 4, so that, they form a permeable front, perpendicular to the flow of leach
solution on its way to the PLS weir. These screens allow the removal of the leach solution from
the leach zones most adjacent to the front slope, avoiding solution build-up and abating high
phreatic levels affecting the factor of safety of the front slope. This area is the most critical area of
the pad from a geotechnical perspective.
Figure 2 Gravel Screen Pad 4B
g) Large diameter wells for the recovery of solution from the phreatic level
The purpose of these large size wells (nominal diameter of 2.50 meters) is to limit the phreatic
levels inside the heap from the beginning of the operation by providing the opportunity of
installing and operating pumps when the phreatic level starts to increase. The idea is to avoid
costly drilling for dewatering purposes. They have the advantage that they are built in stages
with each new lift being stacked on top of the previous. These well rest on the base of the heap,
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taking advantage of the entire saturated height of mineral; their size ensures that they have the
required capacity. Solid, perforated pipes of 457 millimeters in diameter have been installed.
They have a gravel band of around 1m thick around them. Due to their large diameter, the pipes
remain upright until agglomerated mineral is stacked around them. Before being put into
operation, the wells should be cleaned and developed to remove fines from the filter and the
surrounding gravel to maximize solution collection and recovery pumping.
h) Wick drains
In the future, to eliminate serious permeability problems due to the presence of perched solution
(pockets of solution), wick drains will be installed; these are vertical drains made from a
corrugated plastic center wrapped in a nonwoven geotextile. They are used to manage complex
hydrogeological processes and to hydraulically connect the pad vertically. They allow the
drainage of perched phreatic levels, the crossing of areas of low hydraulic conductivity and the
reduction of pressure in artesian zones. A metallic lance (pole) is used to sink them into the
terrain. They can reach depths from 30 to 35 meters in leach ripios, with a maximum diameter
size of from 19 to 25 millimeters.
i) Horizontal internal drains
In the future, to eliminate serious permeability issues of the mineral and thanks to the presence
of bedrock banks located to the east and south-east of Pad 4-B, a design for the installation
(while stacking) of horizontal internal drains has been developed. It is much more practical to
proactively install drains than to try to perforate horizontal drains once the heap exhibits poor
permeability; these drains will be made from corrugated perforated pipe, 102 millimeters in
diameter, which will be connected to the PLS collection secondary drain pipes located on top of
the bedrock banks.
CONCLUSIONS
The process metallurgists and leach operators should be aware of the geotechnical concepts
involved in heap leaching practice in order to understand the mechanical, physical and hydraulic
phenomena, which occur inside heaps, their affect on process performance and the physical
stability of the slopes.
In light of the concepts described above, it is possible to avoid future slope stability problems, both
in dynamic and permanent multilayer leach pads by developing solutions that integrate
geotechnical, operational and metallurgical concepts to protect personnel from safety incidents,
meet environmental requirements and achieve production targets.
AKNOWLEDGEMENTS
This paper describes the development of solutions for the geotechnical and operational problems
which occurred at the permanent leach heaps of Cerro Verde. These ideas generally came from all
the members of the Hydrometallurgical Processes Area and the consultancy firms with which they
work. We would like to thank all of the people involved for their creativity and effort.
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REFERENCES
Memorndum Tcnico: Preliminary Extraction Well Design, North Face, Pad 4A, SMCV, Arequipa, Peru, URS,
Febrero 2009
Evaluacin Geotcnica Integral del Pad 4A, Vector S.A.C., Octubre 2009
Leach Pad N 4A Buttress and Slope Regrading, URS, Noviembre 2009
Memorndum Tcnico: Final Cerro Verde Pad 4A - Liquefaction Analysis, Summary of Runout Estimate, URS,
Julio 2010
Memorndum Tcnico 002 - Anlisis de Estabilidad Adicional Seccin C-C Pad 4A, Ausenco vector,
Septiembre 2011.
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Base metals hydrometallurgy
ChAP. 2
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Although future copper ores will increasingly require concentrator operations, heap and stockpile leaching (including bio-leaching of low grade primary sulfides) will continue to represent a significant production segment in copper mining. Future copper leach operations will be faced with lower grades, harder, finer grained and more acid-consuming ores, complex mineralogy and cost increases related to water, power, reagents and steel wear. It is, therefore, imperative that existing and new leach operations are well-designed and have robust data bases and daily control of the ore feed mineralogy. In order to achieve optimal and consistent crushing, best-practice agglomeration, good permeability, efficient curing, and lowest acid consumption, a leach operation will require quantitative routine mineralogy data. Several heap leach operations in Arizona, Peru and Northern Chile have benefited from long-term mineralogi-cal feed and leach residue analyzes. Typically, modern laboratory technology such as Xrd Rietveld, near infrared, optical microscopy and automated mineral analyzers were used. The application of the characterization techniques for daily blast hole analysis in two Arizona mines and select operations in Chile and Peru has minimized ore routing errors, supported a better p80 and throughput in crushing, reduced permeability failures, and optimized hydro-metallurgical treatment. This paper provides application examples and recom-mendations for production mineralogy in conventional copper leaching, bio-leaching and/or hybrid heap-stockpile concepts. The use of automated small to large mineralogy laboratory modules for mine-site mineralogy will be illustrated.
Daily process mineralogy: A metallurgical tool for optimized copper leaching
Wolfgang Baum, Kevin Ausburn and Randy Zahn. FLSmidth, USA
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INTRODUCTION
Future mining of sulfide ores will be faced with lower grades, harder and finer grained rock
matrices, complex mineralogy, more reagent consumption, remote locations, severe staff shortages,
and cost escalations for power, water, reagents and (steel) wear. To exacerbate these challenges, the
cyclical exploration approach may not be able to provide sufficient re-fills in the reserve
pipelines. High throughput heap leach (and stockpile bio-leach) operations of the future will have
to use considerably better ore characterization and production control mineralogy in order to
achieve good copper extraction while maintaining low operating cost.
These better ore characterization approaches were pioneered in the 1980s and started to become
increasingly accepted in the new copper leach operations in Chile in the 1990s.
One case study example is the step-changing process mineralogy work at the El Indio gold-silver-
copper operation (then owned by St. Joe Minerals Corporation) which resulted in substantial plant
metallurgy improvements and significant gold, silver and copper recovery increases (Baum et al
1989).
A break-through for process mineralogy for copper leach operations was accomplished with the
extensive use of mineralogical ore characterization by both the El Abra and Radomiro Tomic leach
operations. Specifically at Radomiro Tomic, the first robust, semi-quantitative copper and alteration
mineralogy was carried out on large sample numbers and probably contributed to good startup
and continuously high leach extraction (Cuadra C. and Rojas S. , 2001) and Baum 1998b cited in
Cuadra and Rojas).
Challenges in copper leaching
A ground rule for optimized copper leaching (J.Campbell, 2004, pers. comm.) states maximize
your first cycle leach recovery and control your mineralogy
The copper leach operations of the past had the advantage of relatively good ore grades combined
with oxide copper mineralogy. These ore types are becoming depleted and a variety of ores
including secondary sulfide ores, mixed oxide-sulfide ores, bornite-dominated and, finally, low-
grade chalcopyrite ores will make up the feeds of the future. Also, the future ores may be harder
and will have high(er) acid consumption depending on the host rock type and increase of skarns
and volcanic rocks. Finally, in order to compensate for the declining grades, leach operations
require higher throughput. All of the factors mentioned will place considerable demands on good
ore control which is synonymous with reliable ore characterization.
Operating competitive future heap and bio-stockpile leaching will not be economically attractive
without routine quantitative feed and leach residue mineralogy. Mineralogical analyses, today, are
capable of providing daily/weekly data on:
Mineralogical data Process parameters optimized by mineralogy
Overall gangue mineralogy Geo-technical features
Pyrite content Blast indexing & crusher efficiency
Copper deportment Agglomeration
Clay content Curing requirements
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Acid consumers Permeability failures
Salting potential Acid, Ferric, PLS Impurities, Cu extraction
Although diagnostic extraction tests (i.e. flash leach tests), copper assays, bottle roll, column and
mini heap tests remain baseline metallurgical tools, they cannot and will not provide the answers
for low recoveries, high acid consumption, poor agglomeration and low permeability (to name a
few). Mineralogical analyses are required to assess the cause(s) for poor metallurgy.
The following examples (Tables 1 and 2) illustrate the importance of mineralogy for identifying
leach problems:
Table 1 Variance in Acid Consumption Oxide Leach Ore Northern Chile
Parameter Ore Type A Ore Type B
Leach extraction, % 74.3 58.9
Acid consumption, lbs/t 18.9 29.6
Matrix fracturing, % 26.5 41.2
Iron hydroxides, % 16.2 25.4
Ca-Montmorillonite,% 4.3 15.8
Modified after Baum, Smith & Sepulveda 1996
Table 2 Diagnostic Quick Leach & Copper Deportment Errors
Total Cu = 0.89% - Cyanide Soluble Cu = 69%
Diagnostic Leach Conclusion: 77% Covellite/Chalcocite Mineralogy
Actual Mineralogy
Copper Mineral % Distribution Leach Type
Cu-Fe-hydroxide/Chrysocolla 36 Semi-Refractory
Covellite/Chalcocite 20 Ferric Acid Leachable
Chrysocolla/Malachite 29 Acid Soluble
Chalcopyrite/Turquoise 15 Refractory
Estimated Total Recovery
Mineralogy 60% Diagnostic Leach 77%
Assays 53%
Bottle Roll Tests 65%
45 Day Column Tests 59%
Modified after Baum 1998a
METHODOLOGY
The currently available mineralogical tools consist of 5 major optimized techniques or innovations
which were introduced during the last 20 years:
1. Automated sample preparation for high throughput and fast turnaround
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2. Polarized Light Microscopy
3. XRD (x-ray diffraction) Rietveld mineralogy (quantitative)
4. NIR or FT-NIR (near infrared or Fourier transform near infrared) analyses
5. Automated mineralogy (via QEMSCAN, MLA, TIMA, others*) *QEMSCAN, QEMSCAN WellSite, MLA, MLA Express, ASPEX: FEI, Hillsboro, OR USA TIMA: Tescan USA, Cranberry Township/PA USA RoqSCAN: Fugro Robertson/Carl Zeiss, Houston, TX USA EVO MA 15 & Particle SCAN VP: Carl Zeiss, Oberkochen, Germany
Further, the availability of larger, automated or central laboratories, permits mineralogical work on
daily blast hole samples and the use of these data for constant ore control, ore blending, ore routing
and, last but not least, for process control (Allen et al. 2007, Baum, 1996a & b, 1998a, 1999, 2007,
2009, 2013).
Automated sample preparation
The introduction and implementation of robotics technology for sample preparation at various
mining companies has been a step change in providing fast and high-throughput laboratory data
(Best et al, 2007). Specifically, for mineralogy, the availability of automated XRD-NIR laboratories
has enabled data feedback for mining and processing on a daily basis (Baum, 2009).
- Both Freeport-McMo-Ran Copper & Gold laboratories, the Central Analytical Service
Center (Best et al 2007) and the AXN XRD-NIR Mineralogy Lab (Baum 2009) are good
examples of integrating the daily use of mineralogy for leach and concentra