Equilibrium and kinetic modelling of cadmium(II) biosorption byC. vulgaris in a batch system: effect of temperature

The biosorption of cadmium(II) ions to C. vulgaris studied in a batch system with respect to the temperature, initial pH and initial metal ion concentration. The algal biomass exhibited the highest cadmium(II) uptake capacity at 20°C, at the initial pH value of 4.0 and at the initial cadmium(II) ion concentration of 200 mg l−1. Biosorption capacity decreased from 85.3 to 51.2 mg g−1 with an increase in temperature from 20 to 50°C at this initial cadmium(II) concentration. Freundlich and Langmuir isotherm models were tried to represent the equilibrium data of cadmium(II) biosorption depending on temperature. Equilibrium data fitted very well to both the models in the studied concentration range of cadmium(II) ions at all the temperatures studied. The pseudo first- and pseudo second-order kinetic models were also applied to experimental data assuming that the external mass transfer limitations in the system can be neglected and biosorption is sorption controlled. The results showed that cadmium(II) uptake process followed the second-order rate expression and adsorption rate constants decreased with increasing temperature. Using the second-order kinetic constants, the activation energy of biosorption was also evaluated.

ChemosphereVolume 54, Issue 7, February 2004, Pages 951–967

Cr(VI) removal from synthetic wastewater using coconut shell charcoal and commercial activated carbon modified with oxidizing agents and/or chitosan

In this study, the technical feasibility of coconut shell charcoal (CSC) and commercial activated carbon (CAC) for Cr(VI) removal is investigated in batch studies using synthetic electroplating wastewater. Both granular adsorbents are made up of coconut shell (Cocos nucifera L.), an agricultural waste from local coconut industries. Surface modifications of CSC and CAC with chitosan and/or oxidizing agents, such as sulfuric acid and nitric acid, respectively, are also conducted to improve removal performance. The results of their Cr removal performances are statistically compared. It is evident that adsorbents chemically modified with an oxidizing agent demonstrate better Cr(VI) removal capabilities than as-received adsorbents in terms of adsorption rate. Both CSC and CAC, which have been oxidized with nitric acid, have higher Cr adsorption capacities (CSC: 10.88, CAC: 15.47 mg g−1) than those oxidized with sulfuric acid (CSC: 4.05, CAC: 8.94 mg g−1) and non-treated CSC coated with chitosan (CSCCC: 3.65 mg g−1), respectively, suggesting that surface modification of a carbon adsorbent with a strong oxidizing agent generates more adsorption sites on their solid surface for metal adsorption.

Water ResearchVolume 33, Issue 11, August 1999, Pages 2469–2479

A review of potentially low-cost sorbents for heavy metals

The use of low-cost sorbents has been investigated as a replacement for current costly methods of removing heavy metals from solution. Natural materials or waste products from certain industries with a high capacity for heavy metals can be obtained, employed, and disposed of with little cost. Modification of the sorbents can also improve adsorption capacity. In this review, an extensive list of sorbent literature has been compiled to provide a summary of available information on a wide range of potentially low-cost sorbents, including bark, chitosan, xanthate, zeolite, clay, peat moss, seaweed, dead biomass, and others. Some of the highest adsorption capacities reported for cadmium, chromium, lead and mercury are: 1587 mg Pb/g lignin, 796 mg Pb/g chitosan, 1123 mg Hg/g chitosan, 1000 mg Hg/g CPEI cotton, 92 mg Cr(III)/g chitosan, 76 mg Cr(III)/g peat, 558 mg Cd/g chitosan, and 215 mg Cd/g seaweed.

Title :   Low-Cost Sorbents: A Literature Summary.

The capital and regeneration costs of activated carbon and ion exchange media suggest that better process economics may be achieved with disposable sorbents for the treatment of metals-contaminated water and waste streams. An extensive literature search was conducted to identify potentially inexpensive sorbents that could be disposed, rather than regenerated, after use. The literature indicates that many materials with this potential are readily available, either as process by-products or in their natural form. The most promising sorbents identified in this literature search will be tested at bench scale with synthetic metal solutions.

Reverse osmosis applied to metal finishing wastewater

The electroplating industry is a great water consumer and, as a consequence, one of the biggest producers of liquid effluent. The metal finishing industry presents one of the most critical industrial waste problems. There is therefore growing interest in developing methods for reclaiming metals from plating waste stream and recovery of water using membrane technology [1,2]. The application of reverse osmosis (RO) to the global effluent from the electroplating industry has been studied in this paper. The results obtained show that there is 75–95% recovery of water and nearly total removal of metals in the permeate.

Removal of arsenic from groundwater using low cost ferruginous manganese ore

A low cost ferruginous manganese ore (FMO) has been studied for the removal of arsenic from groundwater. The major mineral phases present in the FMO are pyrolusite and goethite. The studied FMO can adsorb both AS(III) and As(V) without any pre-treatment, adsorption of As(III) being stronger than that of As(V). Both As(III) and As(V) are adsorbed by the FMO in the pH range of 2–8. Once adsorbed, arsenic does not get desorbed even on varying the pH in the range of 2–8. Presence of bivalent cations, namely, Ni2+, Co2+, Mg2+ enhances the adsorption capability of the FMO. The FMO has been successfully used for the removal of arsenic from six real groundwater samples containing arsenic in the range of 0.04–0.18 ppm. Arsenic removals are almost 100% in all the cases. The cost of the FMO is about 50–56 US$ per metric tonne.

Changes in the Biochemical Oxygen Demand Procedure in the 21st Edition of "Standard Methods for the Examination of Water and Wastewater"

The dilution biochemical oxygen demand (BOD) test has widespread application for design and operation of wastewater treatment processes, evaluating the quality of natural waters, and assessing the effect of wastewater discharges on these waters. While standardization of the BOD-measuring method has become of prime importance in maintaining dependable data acquisition, changes are made as needed in response to questions raised by analysts and to accommodate new applications. The purpose of this article is to describe changes that have been incorporated in the 20th and 21st editions of "Standard Methods for the Examination of Water and Wastewater" (APHA et al., 1998 and 2004). These changes include changes in text format to clarify the procedural steps, allowance for use of bottle sizes ranging from 60 mL or larger, improvements in quality-control procedures, and improvements in the method of calculating BOD. Other changes include allowance for the use of allylthiourea for nitrification inhibition and broadening the source of seed that can be used for inoculation of BOD samples.

Removal of heavy metal from industrial wastewater using chitosan coated oil palm shell charcoal

  

This research focuses on understanding biosorption process and developing a cost effective technology for treatment of heavy metals-contaminated industrial wastewater. A new composite biosorbent has been prepared by coating chitosan onto acid treated oil palm shell charcoal (AOPSC). Chitosan loading on the AOPSC support is about 21% by weight. The shape of the adsorbent is nearly spherical with particle diameter ranging 100~150 µm. The adsorption capacity of the composite biosorbent was evaluated by measuring the extent of adsorption of chromium metal ions from water under equilibrium conditions at 25ºC. Using Langmuir isotherm model, the equilibrium data yielded the following ultimate capacity values for the coated biosorbent on a per gram basis of chitosan: 154 mg Cr/g. Bioconversion of Cr (VI) to Cr (III) by chitosan was also observed and had been shown previously in other studies using plant tissues and mineral surfaces. After the biosorbent was saturated with the metal ions, the adsorbent was regenerated with 0.1 M sodium hydroxide. Maximum desorption of the metal takes place within 5 bed volumes while complete desorption occurs within 10 bed volumes. Details of preparation of the biosorbent, characterization, and adsorption studies are presented. Dominant sorption mechanisms are ionic interactions and complexation.

Water ResearchVolume 26, Issue 4, April 1992, Pages 469–472

A series of different functionalized biopolymers were prepared and their comparative efficiencies for removing lead (II) and copper (II) ions from water at part per million concentrations determined. The biopolymers evaluated included cellulose, alginic acid, chitin, chitosan and carrageenan. Besides the base biopolymers, the carboxymethyl and hydroxamic acid derivatives of these materials were prepared and tested as well. Terephthalic acid and its hydroxamic acid derivative and a state of the art ion exchange resin, Chelex 20™ (Bio-Rad), were also tested as controls. It was found that, generally, the hydroxamic acid derivatives were the most efficient at removing both metals at a number of different starting ion concentrations although no one material was found to be the best under all experimental circumstances.

ChemosphereVolume 55, Issue 1, April 2004, Pages 135–140

Preparation of alginate–chitosan hybrid gel beads and adsorption of divalent metal ions

Naturally occurring polysaccharides such as alginic acid and chitosan have been recognized as one of the most effective adsorbents to eliminating low levels of heavy metal ions from waste water stream. The present study intended to use alginic acid and chitosan simultaneously, which are expected to form a rigid matrix structure of beads due to electrostatic interaction between carboxyl groups on alginic acid and amino groups on chitosan, and to prepare alginate–chitosan hybrid gel beads. This could be achieved for the first time by using water-soluble chitosan, which was obtained by deacetylating chitin to 36–39% degree. The water-soluble chitosan dissolved in water could remain in solution in the presence of sodium alginate, and the homogeneous solution of chitosan and alginate was dispensed into a CuCl2 solution to give gel bead particles. The resultant beads were then reinforced by a cross-linking reaction of aldehyde groups on glutaraldehyde with amine groups on the chitosan. The cross-linking reaction made the beads durable under acidic conditions. The adsorption of Cu(II), Co(II), and Cd(II) on the beads was significantly rapid and reached at equilibrium within 10 min at 25 °C. Adsorption isotherms of the metal ions on the beads exhibited Freundlich and/or Langmuir behavior, contrary to gel beads either of alginate or chitosan showing a step-wise shape of adsorption isotherm.

On the Modification and Characterization of Chemical Surface Properties of Activated Carbon:  In the Search of Carbons with Stable Basic Properties

Differences between the surface chemical properties of hydrogen- and nitrogen-treated samples of an activated carbon were quantified using several complementary techniques. Calorimetric studies conducted at 303 K revealed that the sample treated in N2 at 1223 K adsorbs a great deal of oxygen with unusually high differential heats. In fact, both the quantity and the heat of adsorption increased when the treatment temperature was raised from 773 to 1223 K. In contrast, samples treated in H2 adsorbed less and less O2 as the temperature of treatment was raised; after treatment at 1223 K, virtually no O2 adsorption occurred. At the same time the H/C ratio in the H2-treated samples decreased with increasing treatment temperature. Point of zero charge measurements revealed that only H2 treatments at high temperature (>1073 K) create basic (hydrophobic) surfaces which are stable after prolonged air exposure. These findings are consistent with the notion that the removal of oxygen in the form of CO and CO2 during high-temperature N2 treatment leaves unsaturated carbon atoms at crystallite edges; these sites are very active for subsequent oxygen adsorption. In contrast, high-temperature H2 treatment accomplishes three tasks:  (a) it also removes surface oxygen; (b) it stabilizes some of the (re)active sites by forming stable C−H bonds; (c) it gasifies the most reactive unsaturated carbon atoms. The relative contributions of these three effects depend on the temperature of H2 treatment. The carbon surface resulting from high-temperature H2 treatment is stable against subsequent O2 adsorption in ambient conditions.

Modified activated carbon for the removal of copper, zinc, chromium and cyanide from wastewater

Modified activated carbon are carbonaceous adsorbents which have tetrabutyl ammonium iodide (TBAI) and sodium diethyl dithiocarbamate (SDDC) immobilised at their surface. This study investigates the adsorption of toxic ions, copper, zinc, chromium and cyanide on these adsorbents that have undergone surface modification with tetrabutyl ammonium (TBA) and SDDC in wastewater applications. The modification technique enhance the removal capacity of carbon and therefore decreases cost-effective removal of Cu(II), Zn(II), Cr(VI) and CN− from metal finishing (electroplating unit) wastewater. Two separate fixed bed modified activated carbon columns were used; TBA-carbon column for cyanide removal and SDDC-carbon column for multi-species metal ions (Cu, Zn, Cr) removal. Wastewater from electroplating unit containing 37 mg l−1Cu, 27 mg l−1 Zn, 9.5 mg l−1 Cr and 40 mg l−1 CN− was treated through the modified columns. A total CN− removal was achieved when using the TBA-carbon column with a removal capacity of 29.2 mg g−1 carbon. The TBA-carbon adsorbent was found to have an effective removal capacity of approximately five times that of plain carbon. Using SDDC-carbon column, Cu, Zn and Cr metal ions were eliminated with a removal capacity of 38, 9.9 and 6.84 mg g−1, respectively. The SDDC-carbon column has an effective removal capacity for Cu (four times), Zn (four times) and Cr (two times) greater than plain carbon.

Title :   Low Cost Sorbents Screening and Engineering Analysis of Zeolite for Treatment of Metals Contaminated Water and Soil Extracts

Heavy metals contamination is an environmental problem at Army installations engaged in firearms training and munitions production. Weathering and corrosion of expended munitions and leaching from wastewater lagoons, landfills and bum pits, has resulted in heavy metals contamination of the soil at these facilities. Transport of metals to the groundwater has been confirmed in some locations, requiring treatment of the groundwater at the site. Certain treatment processes for contaminated soil produce metals laden extracts, which also require treatment before reuse or disposal. Low cost sorbents with a high affinity for metals that can be disposed after use may provide an economic alternative to ion exchange and activated carbon. Metals sorption capacity is reported in the literature for a variety of natural materials and industrial byproducts. This information is useful in identifying potentially useful sorbents, but is limited to the specific conditions studied. Of primary interest are those sorbents with a demonstrated affinity for the metals of interest, that are inexpensive and readily available, and that require no modification prior to use. A field ready sorption technology for treatment of metals-contaminated water and waste streams was the principal objective of this work unit.

Use of Activated Carbon for the Recovery of Chromium from Industrial Wastewaters

A technique for the removal and recycling of hexavalent chromium from electroplating industries was developed. It involves a two-phase process which consists of (1) the use of an activated carbon bed for the accumulation of chromium onto the surface of activated carbon followed by (2) the regeneration of the carbon leading to a concentrated chromium solution with potential for reclamation or reuse within the plating operation. Results from continuous ýow experiments showed that in excess of 99% chromium removal efficiency can be achieved. It was also revealed that regeneration of the exhausted carbon under acidic conditions recovered chromium in the trivalent state with concentrations as high as 3 g dm~3, more than 12 times the inýuent concentration. The adsorption capacity of the activated carbon was found to increase with successive cycles of adsorption/regeneration. However, when regeneration was achieved under alkaline conditions, the chromium was recovered in the hexavalent state with concentrations as high as 8·4 g dm~3, in excess of 33 times the chromium inýuent concentration. In addition, under caustic regeneration conditions, the data showed that the adsorption capacity in this case decreases with the increased number of exhaustion cycles. Mass balance calculation for both acid and caustic regeneration indicated that in both cases the regeneration process was incomplete with a recovery efficiency averaging around 50%. In an attempt to maximise the recovery efficiency, a combination of caustic followed by acid regeneration was applied to the exhausted activated carbon and the results led to a drastic improvement in the total recovery process (85–98%). These results clearly show that activated carbon is a viable candidate for the removal and recovery of chromium from electroplating industries. The critical advantage in the use of activated carbon is (1) the ability to regenerate and thus prepare a concentrated chromium solution for potential reclamation or recycle to the plating operation, and (2) the potential of avoiding the generation of hazardous sludge for land disposal.

Removal of chromium from water and wastewater by ion exchange resins

Removal of chromium from water and wastewater is obligatory in order to avoid water pollution. Batch shaking adsorption experiments were carried out to evaluate the performance of IRN77 and SKN1 cation exchange resins in the removal of chromium from aqueous solutions. The percentage removal of chromium was examined by varying experimental conditions viz., dosage of adsorbent, pH of the solution and contact time. It was found that more than 95% removal was achieved under optimal conditions. The adsorption capacity (k) for chromium calculated from the Freundlich adsorption isotherm was found to be 35.38 and 46.34 mg/g for IRN77 and SKN1 resins, respectively. The adsorption of chromium on these cation exchange resins follows the first-order reversible kinetics. The ion exchange resins investigated in this study showed reversible uptake of chromium and, thus, have good application potential for the removal/recovery of chromium from aqueous solutions.

Adsorption of Cu(II) and Cr(VI) ions by chitosan: kinetics and equilibrium studiesR Schmuhl, HM Krieg, K Keizer

The ability of chitosan as an adsorbent for Cu (II) and Cr (VI) ions in aqueous solution was studied. The experiments were done as batch processes. Equilibrium studies were done on both cross-linked and non-cross-linked chitosan for both metals. Cr (VI) adsorption behaviour could be described using the Langmuir isotherm over the whole concentration range of 10 to 1000 mg·l-1 Cr. The maximum adsorption capacity for both types of chitosan was found to be 78 mg·g-1 for the non-cross-linked chitosan and 50 mg·g-1 for the cross-linked chitosan for the Cr (VI) removal. For the Cu (II) removal the Freundlich isotherm described the experimental data over the whole concentration range of 10 to 1000 mg·l-1 Cu (II). The maximum adsorption capacity for both types of chitosan can be estimated to be greater than 80 mg·g-1. Cr (VI) removal was the highest at pH 5 but pH did not have a large influence on Cu (II). From these results it is clear that the adsorption of heavy metals is possible with chitosan, but that with this method, end concentrations of below 1 mg·l-1 can hardly be obtained.

Removal of Heavy Metal from Contaminated Water by Biopolymer Crab Shell ChitosanM.S. Rana, M.A. Halim, S. Safiullah, M. Mamun Mollah, M.S. Azam, M.A. Goni, M. Kamal Hossain andM.M. Rana

The study focuses on potential of using crab shell chitosan as a low-cost biosorbent, for heavy metals removal from aqueous solutions in an adsorption filtration system. Chitosan was synthesized from chitin by the treatment of strong alkali solution under reflux condition and chitin was extracted from crab shell followed by decalcification and deproteinization treatment. Spectrometric (AA and UV) method was employed to detect the heavy metals concentration. Prepared 10 mg L-1 solutions of zinc, lead, cadmium, cobalt, nickel, chromium, manganese and iron were passed through the 5 g of chitosan separately and it was found that chitosan was excellent adsorbent in removing mentioned heavy metals. The removal efficiency of chitosan was in the following order Mn>Cd>Zn>Co>Ni>Fe>Pb>Cr. The result also showed that the time required for 100% breakthrough of prepared chitosan for Mn and Zn was approximately 27 and 23 h whereas it was only 16 h for both Cr and Pb, respectively. The research revealed that prepared chitosan showed better removal performance for Mn, Cd, Zn whereas the removal efficiency was satisfactory for Co, Ni and Fe but it exhibited relatively least performance for Pb and Cr.

Modified crab shell particles for the removal of lead[II] ions from aqueous solutions

By: Ramalingham Senthilkumar, Josephraj Jegan, Puthugramam Venkitakrishnan Ramachandra Iyer, Manickam Velan

Courtesy of International Journal of Environment and Waste Management (IJEWM)Published:Apr. 9, 2012

The ability of crab shell particles to remove lead[II] was evaluated in a batch reactor and in a fixed–bed column. The binding of lead[II] by crab shell was found to be affected significantly by pH, with maximum sorption capacity 714 mg/g observed at pH 4. The sorption isotherm of lead[II] on crab shell particles was modelled by the application of Langmuir followed by Sips, Redlich–Peterson and Freundlich. The kinetic data followed pseudo–second–order kinetics. A glass column (2 cm I.D and 35 cm height) was used to study the continuous lead[II] biosorption performance of crab shell particles with different bed heights.Keywords: biosorption, crab shells, kinetics, packed bed column, lead removal, Portunus sanguinolentus, crab shell particles