determination of cobalt in seawater using neutron activation...

Research ArticleDetermination of Cobalt in Seawater Using NeutronActivation Analysis after Preconcentration by Adsorptiononto 120574-MnO2 Nanomaterial

Van-Phuc Dinh 1 Ngoc-Chung Le2 Ngoc-Tuan Nguyen3

Quang-Thien Tran3 Van-Dong Nguyen4 Anh-Tuyen Luu5 N Quang Hung6

Tran Duy Tap4 and Thien-Hoang Ho1

1Dong Nai University 4 Le Quy Don Tan Hiep Ward Bien Hoa City Dong Nai Province Vietnam2Dalat University Dalat City Lam Dong Province Vietnam3Nuclear Research Institute Dalat City Lam Dong Province Vietnam4University of Science Vietnam National University Ho Chi Minh City Vietnam5Center for Nuclear Techniques Vietnam Atomic Energy Institute Ho Chi Minh City Vietnam6Institute of Fundamental and Applied Sciences Duy Tan University 3 Quang Trung Da Nang City Vietnam

Correspondence should be addressed to Van-Phuc Dinh dinhvanphuc82gmailcom

Received 14 September 2017 Revised 4 January 2018 Accepted 28 January 2018 Published 22 February 2018

Academic Editor Jean-Marie Nedelec

Copyright copy 2018 Van-Phuc Dinh et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The 120574-MnO2 nanomaterial has been used to adsorb cobalt in the seawater at Phan Thiet City Binh Thuan Province Vietnam Itsconcentration is determined by using the neutron activation analysis (NAA) method at the Dalat nuclear research reactor Factorsaffecting the uptake of cobalt on the 120574-MnO2 material such as the pH adsorption time and initial cobalt(II) concentration areinvestigated The irradiated experiment data are calculated using the K0-Dalat program The results obtained show that the tracedissolved cobalt in Phan Thiet seawater is found equal to 025 plusmn 004 120583gL (119899 = 5 119875 = 95) with the adsorption efficiency beinghigher than 95 (119899 = 4 119875 = 95)

1 Introduction

Cobalt is an essential micronutrient and the central metalcofactor in the Vitamin B12 [1] It can be found in thebiological and environmental samples such as fish eggmilk green vegetable and seawater In seawater dissolvedcobalt (DCo) exists mainly as a cobalt(II) ion in chloro-carbonate complexes [2] and bound to organic ligands [3]Although the concentration of DCo in seawater is ratherlow it can affect the growth rate of coccolithophorids andcyanobacteria some metabolic processes the phytoplanktoncommunity structure and the carbon flux at the atmosphere-ocean interface [4] In addition the concentration of DCo inseawater which can vary differently depending on the humanactivities at different ocean regions such as dust mineral

activity and industry can lead to the unpredictable effects onenvironment and food resources Therefore determinationof the DCo concentration in seawater has recently becomean important topic for interdisciplinary researches includingphysics chemistry and environment However it is difficultto determine directly the total DCo in seawater by themost commonly used instrumental analytical methods dueto their limited sensitivity andor matrix effects Thereforethe separation of cobalt from the sample matrices as wellas the preconcentration of cobalt is crucial for the accurateand efficient determinations of cobalt at the ultratrace levelsin seawater Various methods in addition to the moderninstrumental methods have been used to enrich the level ofcobalt in seawater such as the coprecipitation [2] liquid-liquid phase extraction [5] and solid phase extraction [6 7]

HindawiJournal of ChemistryVolume 2018 Article ID 9126491 8 pageshttpsdoiorg10115520189126491

2 Journal of Chemistry

Neutron activation analysis (NAA) is a sensitive and spe-cial method for determining simultaneously a large numberof elements [8] One of the advantages of the NAA methodover the common spectrometric methods is that it allows usto directly analyze the samples in original forms without theuse of dissolution steps that may cause the sample dilutionand contaminationWithin theNAA the preconcentration ofthe trace elements from the aqueous samples such as seawaterabsorbed on solid materials is usually preferred among theother methods However a drawback of this method is that itis not able to analyze the water samples since the radiolysis ofwater itself may cause a release of radiogas or even anexplosion out of the container [9] Hence the adsorptionused to preconcentrate the elements from the water ontothe solid phase is a promising method for the detectionof trace elements in seawater as well as in other solutionsSome adsorbents have been used for these preconcentrationsteps such as the magnesium oxide [9] charcoal [10ndash14] andaluminium and iron(III) oxides [15] However the use ofnanooxide as an adsorbent material for the retention of traceelements from seawater before being determined by the NAAmethod has still been limited so far

In fact the nanomaterials which have their own physic-ochemical properties and therefore differ from the nonnano-materials have been applied to a variety of areas Among thenanomaterials the manganese oxides with various types ofcrystalline structures such as 120572- 120573- 120574- MnO2 have beenextensively studied owing to their structural varieties andexcellent chemical characteristics As a result they have beenapplied to different areas such as batteries molecular sievescatalysts and adsorbents [16 17] However the use of 120574-MnO2 nanomaterial as a solid phase for the preconcentrationof cobalt from seawater has still been rarely studied

In the present work the 120574-MnO2 nanomaterial is used asa preconcentration agent to extract cobalt from the seawatercollected at Hon Rom Beach Phan Thiet City Binh ThuanProvince Vietnam before applying the NAA method todetermine its concentration Furthermore factors affectingthe adsorption capacity of this nanomaterial such as the pHadsorption time and initial cobalt concentration are alsoinvestigated within the present work

2 Experimental Method

21 Reagents and Materials The cobalt(II) ion is used as anadsorbate A 1000mgL standard stock solution containingeach set of cobalt(II) ions is prepared by dissolving theCo(NO3)2 (Merck pa) in the double-distilled water TheHNO3 (Merck pa) and NaOH (Merck pa) are then usedto adjust the pH of the solution The 120574-MnO2 nanomaterialis synthesized via the reaction between the potassium per-manganate (KMnO4) (Merck pa) solution and the ethanol(C2H5OH) (Merck pa) at the room temperature as reportedpreviously in [17 18] A 300ml potassium permanganate(KMnO4) saturated solution is gradually placed into a 300mlof the mixture between the ethanol (C2H5OH) and thedistilled water which is then strongly agitated during 8 hTheobtained solid precipitate is dried at 100∘C in 12 h After that

Figure 1 Hon Rom Beach Phan Thiet City Binh Thuan ProvinceVietnam where the seawater samples are collected

it is cleaned several times by using the distilled water in orderto get the 120574-MnO2 products

Seawater collected from the Hon Rom Beach PhanThiet City Binh Thuan Province Vietnam at the position of10∘57N-108∘19W (see Figure 1) is filtered through 02120583mSar-tobran 300 cartridges (Sartorius) which are later used for theDCo analyses The samples are collected in the acid cleaned250mL LDPE Nalgene bottles which are rinsed 5 timestogether with the samples before the collection After thatthe processes are similar to those presented in Section 2 of[19] except that HNO3 at 001M (Merck) has been used toacidify the sampleswithin an hour instead of using ultrapureHCl as in [19]

22 Instruments The phase of the crystalline structure isdetermined by using the X-ray diffractometer (XRD) D5000made by Siemens (Germany) with the X-ray radiation ofCuK120572 and wavelength 120582 = 15406 A The ultrahigh resolu-tion scanning electron microscopy (SEM) S-4800 made byHitachi (Japan) and the transmission electron microscope(TEM) JEM1010made by JEOL (Japan) are used to investigatethemorphology of thematerialsThe surface area of themate-rials is calculated within the BrunauerndashEmmettndashTeller (BET)theory [26]The concentration of the samples before and afterthe adsorption is determined by using the atomic absorptionspectrophotometer (AAndash7000) made by Shimadzu (Japan)In addition the pHmeasurements are performed using a pH-meter Mi-150 (MARTINI Instruments made in Romania)The latter is standardized using the HANNA instrumentalbuffer solutions with different values of pH namely 401 plusmn001 701 plusmn 001 and 1001 plusmn 001 A temperature-controlledshaker (Model IKA R5) is used for the studies of theequilibrium states

Journal of Chemistry 3

Table 1 Isotherm equilibrium parameters calculated from different models

Models Equations Parameters RMSE 1205942

Langmuir 119902119890 =119876max sdot 119870119871 sdot 1198621198901 + 119870119871 sdot 119862119890

119876max (mgg) 9091 119870119871 (Lmg) 05430 1999 02918

Freundlich 119902119890 = 119870119865 sdot 1198621198901119899 119870119865 (Logg) 6382 1n 00769 2233 03418

Sips 119902119890 =119876119878 sdot 119862119890

120573119878

1 + 120572119904 sdot 119862119890120573119878 119876119904 (mgg) 9500 120572119904 (Lmg) 09810 120573119904 05694 1593 01751

Notations 119902119890 adsorption capacity at equilibrium (mgg) 119862119890 equilibrium concentration (mgL) 119876max monolayer maximum adsorption capacity (mgg)119870119871 Langmuir constant 119870119865 Freundlich constant 119899 adsorption intensity 119876119878 the maximum adsorption capacity (mgg) 120572119904 Sips isotherm model constant(Lmg) 120573119904 Sips isotherm model exponent RMSE root-mean-square error (RMSE = radic(1(119899 minus 1))sum119899119899=1(119902119890meas minus 119902119890calc)2) 1205942 nonlinear chi-square test(1205942 = sum119899119899=1(119902119890meas minus 119902119890calc)2119902119890calc)

23 Adsorption Study A 01 gram of the nanomaterials isplaced into a 100mL conical flask containing 50mL of thecobalt(II) ionsThe influences of pH (2ndash55) adsorption time(10ndash240min) and metal ion concentrations (40ndash400mgL)on the nanomaterials are also studied The concentrations ofcobalt(II) ions before and after the adsorption process aredetermined by using the atomic absorption spectroscopymethod The adsorption ability of the 120574-MnO2 nanomaterialis calculated as [27]

Removal =(119862119900 minus 119862119890) times 100119862119900

(1)

whereas the adsorption capacity can be obtained from themass balance equation for the adsorbent as [27]

119902 =(119862119900 minus 119862119890) times 119881119898

(2)

where q is the adsorption capacity (mgg) at the equilibriumand Co and Ce are the initial and equilibrium concentrations(mgL) respectively V is the volume (L) of the solution andm is the mass (g) of the adsorbent used In fact severaladsorption isotherm equations [28] have been applied in thepresent work in order to assess the adsorption ability of the120574-MnO2 materials as well as the nature of the uptake aspresented in Table 1

24 Neutron Activation Analysis A 1-gram 120574-MnO2 is addedto 15 liters of seawater and they are mixed by magneticallystirring at the speed of 240 rpm in 120mins The solid iscollected via the filtration process and dried at 80∘C in 24hours An accurate weight of the dried 120574-MnO2 is packedand sealed in the polyethylene containers and then irradiatedin the core of the Dalat nuclear research reactor with theneutronflux of 31012 ncm2sdots in002010 hours After 30 days ofradioactive decay the samples are measured during 18000 secin order to determine the cobalt concentration To controlour experimental method the standard-addition techniquehas been used by placing 10 gram of 120574-MnO2 with 15 litersof seawater which contain 10 15 and 20 120583g of cobalt standardsolutionThe time for the added cobalt being equilibriated inseawater is 10mins at the room temperatureThe preparationirradiation and decaying and measuring times are kept to bethe same as for the above samples

10

20

30

40

50

60

70

Inte

nsity

(au

)

25 30 35 40 45 50 55 60 65 70 75 80202-theta (deg)

222∘

378∘

425∘

563∘

657∘

-MnO2

Figure 2 The XRD spectrum of the 120574-MnO2 nanomaterial

25 Gamma Activity Measurement In order to measurethe activated samples we employ the calibrated gamma-ray spectrometers based on the HPGe detectors (ORTECGMX-30190 model) with the acquisition software providedby CANBERRA Genie-2KThe K0-Dalat program [29 30] isapplied to calculate the elemental concentrations the uncer-tainties and the detection limits

3 Results and Discussion

31 Characterization of the 120574-MnO2 Nanomaterial Shown inFigure 2 are the XRD patterns of the 120574-MnO2 nanostructureAs can be seen in this Figure 2 some specific peaks aredeveloped at the different angles 2120579 equal to 222∘ 378∘ 425∘563∘ and 657∘ These peaks are certainly associated with theorthorhombic structure of the 120574-MnO2material (JCPDS cardnumber 82-2169)

Figure 3 presents the SEM (a) and TEM (b) images of120574-MnO2 These figures clearly show a porous surface whichincludes many nanospheres with diameters from 10 nm to 80nm These results indicate that the 120574-MnO2 nanomaterialmight offer more adsorption sites for the adsorbates

The surface area and pore size of 120574-MnO2 are investi-gated within the BET and Barrett-Joyner-Halenda (BJH) [31]methods The results obtained are presented in Table 2 It is


Table 2 The BET and BJH analytical results

BJH Adsorption average pore width BJH desorption average pore width BET surface area120574-MnO2 4178 A 3402 A 650m2sdotgminus1

100 nm

(a)

134 nm

167nm

129 nm

105 nm

105 nm 114 nm

151 nm

100 nm

(b)

Figure 3 SEM (a) and TEM (b) images of the 120574-MnO2 nanomaterial

seen that the surface area of 120574-MnO2 is about 65 m2g with

a pore size smaller than 500 A and larger than 20 A whichcorresponds to the size of the mesoporous materials [32]

32 Factors Affecting the Adsorption of Cobalt The pH is oneof the essential factors which affects the adsorption of thecobalt(II) ion onto the 120574-MnO2 nanomaterials As can be seenin Figure 4(a) at the low pH values the uptake of cobalt(II)ion on the material surfaces decreases because of two mainreasons The first reason is due to the charge of the materialsurface which is positive and is not favorable for the uptakeof Co(II) cation [33ndash38] The second reason is that thereis a competition between the H+ and Co2+ ions [37 38]At the high pH values the adsorption of cobalt(II) ionreaches a plateau due to the formation of different typesof cobalt(II) such as Co(OH)+ and Co(OH)2 which inhibitthe adsorption of Co2+ ions on 120574-MnO2 [39] Therefore arange of pH values has been chosen from 20 to 55 inorder to achieve the optimum adsorption of cobalt As aresult the maximum adsorption is obtained at pH ge 40with an approximate removal of 988 at the initial cobaltconcentration of 150mgL

The effects of pH and contact time on the adsorption ofCo(II) onto the 120574-MnO2 nanomaterial are shown in Figures4(a) and 4(b) respectively These figures show that theadsorption increases with increasing both the pH and thecontact time and reaches the equilibrium after 120mins at thepH value of 4 despite different initial cobalt concentrationsHence 120mins of adsorption time has been chosen foradsorbing cobalt from the seawater samples Moreover it canbe seen also from these figures that the higher the initialconcentration of Co(II) is the lower the adsorption rate ofCo(II) onto the 120574-MnO2 nanomaterial is achievedThis resultcan be explained by the saturation of the binding-sites of thenanomaterial when the concentration is increasing

33 Adsorption Isotherm Studies Figure 5 shows the plotsof the Langmuir Freundlich and Sips nonlinear isotherm

models whose parameters are given in Table 1 It is knownthat the Langmuir model assumes the uptake of cobalt(II)on the 120574-MnO2 nanomaterial to be monolayer adsorptionOn the other hand the Freundlich model is based on theassumption that the adsorption of cobalt(II) ions should bewith multilayers and there is an interaction between theadsorbate and absorbent However both of models above arerestricted by the solute concentrations Therefore the Sipsequation which combines the Langmuir and Freundlichmodels has been proposed in order to describe well theuptake of cobalt(II) onto the 120574-MnO2 nanomaterial By com-paring the results obtained from the root-mean-square error(RMSE) with the corresponding 1205942 values it is found thatthe Sips model offers the best fit to experimental data asthis model has the smallest RMSE and 1205942 values among theother two Langmuir and Freundlich models The monolayeradsorption and adsorption capacities calculated from theLangmuir and Sips models are 9091mgg and 9500mggrespectivelyThese results indicate that the 120574-MnO2 nanoma-terial can be used as an adsorbent to extract and concentratethe cobalt ions from the water samples

34 Determination of Cobalt in Seawater Figures 6 and 7depict the gamma-ray spectra of the 120574-MnO2 nanomaterialbefore and after the adsorption of elements in seawater Theresults obtained from the analysis of some elements in thesurface seawater at Hon Rom Beach Phan Thiet City (10∘571015840North-108∘191015840 East) using the NAAmethod after the precon-centration by adsorption onto the 120574-MnO2 nanomaterial arepresented in Table 3 These results show that the content ofcobalt in the surface seawater at the location above is found tobe 025 plusmn 004 120583gL (119899 = 5 119875 = 095) with the recoveryof about 969ndash104 (119899 = 4 119875 = 095) These resultsare also in good agreement with the original concentrationsfound in the seawater samples as well as the added analyteconcentrations Furthermore some other elements are newlydetected as shown in Table 4 It is worthwhile mentioninghere that in principle the added cobalt can be bound to


0 1 2 3 4 5 6 70

20

40

60

80

100

rem

oval

pH

300 mgL150mgL

(a)

60

80

100

re

mov

al

150mgL170mgL220mgL

50 100 150 200 250 3000Time (mins)

(b)

Figure 4 Effects of pH (a) and contact time (b) on the adsorption of Co(II) onto the 120574-MnO2 nanomaterial at different initial concentrationsof cobalt

0 30 60 90 120 15060

70

80

90

100

ExperimentLangmuir

FreundlichSips

qe

(mg

g)

Ce (mgL)

Figure 5 Plots of the adsorption capacity at the equilibriumq119890 versus the equilibrium concentration C119890 obtained within theLangmuir Freundlich and Sips nonlinear isotherm models

make some particulate materials andor dissolved organicligands depending on the complexation kinetics and time forwhich the added cobalt can be exposed to the seawater How-ever this effect which might cause the change of the analyti-cal results is considered to be relatively small since the dissol-ubility of the solution used in the present study (10ndash20120583gL)is rather high and the seawater samples before being ana-lyzed are carefully filtered and acidified as described inSection 21

35 Comparison with Other Studies Table 5 presents thecontent of cobalt in seawater at some areas in the worlddetermined by the same andor different methods It is foundthat the concentration of DCo in the surface seawater at

0

20

40

60

80

100

Energy (keV)

Zn-65

Co-60 Co-60

0

200

400

600

800

1000

1200C

ount

s

Cou

nts

500 1000 1500 20000Energy (keV)

1100 1150 1200 1250 1300 1350

13325 keV11732 keV

1115 keV

Figure 6 Gamma-ray spectrum of the 120574-MnO2 nanomaterialbefore the adsorption of elements in the seawater

0 500 1000 1500 2000

0

50

100

150

200

Energy (keV)

Sc-46

Zn-65

Co-60Co-60

Fe-59 Fe-59

Cou

nts

0

200

400

600

800

1000

1200

Cou

nts

Energy (keV)1100 1150 1200 1250 1300 1350

1291 kev1099 kev

1173 kev1332 kev

1115 kev

1120 kev

Figure 7 Same as Figure 6 but after the adsorption of elements inthe seawater


Table 3 Analytical results for cobalt in seawater

Element Co(II) added(120583gL) Found (120583gL) SD Recovery ()

Cobalt

0 025plusmn 005 (119899 = 5 119875 = 095) 00410 101 plusmn 116 (119899 = 4 119875 = 095) 073 988015 148 plusmn 108 (119899 = 4 119875 = 095) 068 969320 211 plusmn 277 (119899 = 4 119875 = 095) 174 10400

SD standard deviation

Table 4 Elements found in seawater by using the NAA method

Elements Found (120583gL) (119899 = 5 119875 = 095) SDFe 213 plusmn 189 152Zn 701 plusmn 172 138Ce 192 plusmn 023 019Sc 007 plusmn 001 0008SD standard deviation

Table 5 Content of cobalt in the seawater at some areas in the world obtained within the same andor different analytical methods HereGFAAS and SF-ICP-MS stand for graphite furnace atomic absorption and sector field inductively coupled plasma mass spectrometersrespectively

Area DCo (120583gL) Analytical methods RefMediterranean Sea 002 SF-ICP-MS [19]Bosphorus 428 GFAAS [20]South East Atlantic 030sdot10minus3ndash348sdot10minus3 Flow-Injection Analysis (FIA) and chemiluminescence [21]Crozet Islands Southern Ocean 142sdot10minus3ndash289sdot10minus3 ICP-MS [22]Western Atlantic Ocean 083sdot10minus3ndash585sdot10minus3 Chemiluminescence [23]North Atlantic gyre Atlantic Ocean 138sdot10minus3 FIA with chemiluminescence [24]South Atlantic gyre Atlantic Ocean 325sdot10minus3 FIA with chemiluminescence [24]Angola Gyre Atlantic Ocean 071sdot10minus3ndash974sdot10minus3 Ultrahigh resolution mass spectrometry [25]BinhThuan Vietnam 025 NAA This study

Binh Thuan coast Vietnam obtained within the presentwork is 025 120583gL This amount is higher than the resultsobtained from some different locations in the world suchas Mediterranean Sea [19] South East Atlantic [21] CrozetIslands Southern Ocean [22] Western Atlantic Ocean [23]North and South Atlantic gyre of Atlantic Ocean [24] andAngola Gyre of Atlantic Ocean [25] except the Bosphorusarea [21] (see Table 5)The reason is that the seawater samplesused in the present analysis are collected from the beachwhich is located near the residential area that might cause theincrease in the level of cobalt

4 Conclusions

The neutron activation analysis method at the Dalat nuclearreactor (Vietnam) has been used to determine the concen-tration of dissolved cobalt in the seawater at Phan ThietCity Binh Thuan Province Vietnam after the preconcen-tration by adsorption onto the 120574-MnO2 nanomaterial Theconcentration of dissolved cobalt in the surface seawater isfound to be 025 plusmn 004 120583gL (119899 = 5 119875 = 095) with the

approximate recovery of 9693ndash104 (119899 = 4 119875 = 095) Inaddition some elements and their concentrations have beennewly determined namely Fe (212 120583gL) Zn (701 120583gL)Ce (192 120583gL) and Sc (007 120583gL) All the results obtainedshow that the 120574-MnO2 nanomaterial can indeed be usedas an adsorbent to preconcentrate the trace elements fromthe water samples before being determined by the neutronactivation analysis method

Conflicts of Interest

The authors declare that there are no conflicts of interestregarding the publication of this paper

References

[1] R U Shelley B Zachhuber P N Sedwick P J Worsfold andM C Lohan ldquoDetermination of total dissolved cobalt in UV-irradiated seawater using flow injection with chemilumines-cence detectionrdquo Limnology and Oceanography Methods vol8 no JULY pp 352ndash362 2010


[2] Q Zhang H Minami S Inoue and I Atsuya ldquoDeterminationof ultra-trace amounts of cobalt in seawater by graphite fur-nace atomic absorption spectrometry after pre-concentrationwith Ni8-quinolinol1-nitroso-2-naphthol complexrdquo AnalyticaChimica Acta vol 407 no 1-2 pp 147ndash153 2000

[3] J Bown M Boye and D M Nelson ldquoNew insights on the roleof organic speciation in the biogeochemical cycle of dissolvedcobalt in the southeastern Atlantic and the Southern OceanrdquoBiogeosciences vol 9 no 7 pp 2719ndash2736 2012

[4] C E Thuroczy M Boye and R Losno ldquoDissolution of cobaltand zinc from natural and anthropogenic dusts in seawaterrdquoBiogeosciences vol 7 no 6 pp 1927ndash1936 2010

[5] M R Jamali B Soleimani R Rahnama and S H A RahimildquoDevelopment of an in situ solvent formation microextractionand preconcentration method based on ionic liquids for thedetermination of trace cobalt (II) in water samples by flameatomic absorption spectrometryrdquoArabian Journal of Chemistryvol 10 pp S321ndashS327 2017

[6] Y Wang X Ke X Zhou J Li and J Ma ldquoGraphene forseparation and preconcentration of trace amounts of cobalt inwater samples prior to flame atomic absorption spectrometryrdquoJournal of Saudi Chemical Society vol 20 pp S145ndashS152 2016

[7] S Hirata Y Hashimoto M Aihara and G Vitharana MallikaldquoOn-line column preconcentration for the determination ofcobalt in sea water by flow-injection chemiluminescence detec-tionrdquoFreseniusrsquo Journal of Analytical Chemistry vol 355 no 5-6pp 676ndash679 1996

[8] D F Schutz and K K Turekian ldquoThe investigation of thegeographical and vertical distribution of several trace elementsin sea water using neutron activation analysisrdquo Geochimica etCosmochimica Acta vol 29 no 4 pp 259ndash313 1965

[9] J M Lo K S Lin J C Wei and J D Lee ldquoEvaluation onchemical neutron activation analysis for trace metals in sea-water using magnesium oxide as the preconcentration agentrdquoJournal of Radioanalytical and Nuclear Chemistry vol 216 no1 pp 121ndash124 1997

[10] E Hasanen and P Manninen ldquoDetermination of total organicchlorine and bromine in water samples by adsorption onto acti-vated carbon and neutron activation analysisrdquo Chemospherevol 16 no 5 pp 969ndash972 1987

[11] Y Sakai T Tomura K Ohshita and S Koshimizu ldquoDetermi-nation of trace copper in water samples by neutron activationanalysis preceded by preconcentration on activated carbonpowderrdquo Journal of Radioanalytical and Nuclear Chemistry vol230 no 1-2 pp 261ndash263 1998

[12] H A Van Der Sloot ldquoThe determination of chromium in watersamples by neutron activation analysis after preconcentrationon activated carbonrdquo Journal of Radioanalytical Chemistry vol37 no 2 pp 727ndash739 1977

[13] A M Yusof M M Rahman and A K H Wood ldquoSpeciationof some trace elements in water samples after preconcentrationon activated carbon by neutron activation analysisrdquo Journal ofRadioanalytical and Nuclear Chemistry vol 259 no 3 pp 479ndash484 2004

[14] M T Valentini Ganzerli L Maggi and V Caramella CrespldquoPreconcentration and neutron activation analysis of thoriumand uranium in natural watersrdquo Journal of Radioanalytical andNuclear Chemistry vol 262 no 1 pp 143ndash146 2004

[15] U Kerdpin O A Arquero R Watanesk and U SriyothaldquoManganese (II) adsorption stdudies on Aluminium oxide andIron (III) oxide by neutron activation analysisrdquo Journal of theScience Society of Thailand vol 24 pp 73ndash80 1998

[16] J Li B Xi Y Zhu Q Li Y Yan and Y Qian ldquoA precursor routeto synthesize mesoporous 120574-MnO2 microcrystals and theirapplications in lithium battery and water treatmentrdquo Journal ofAlloys and Compounds vol 509 no 39 pp 9542ndash9548 2011

[17] N C Le and D Van Phuc ldquoSorption of lead (II) cobalt(II) and copper (II) ions from aqueous solutions by 120574-MnO2nanostructurerdquo Advances in Natural Sciences Nanoscience andNanotechnology vol 6 no 2 Article ID 025014 2015

[18] V P Dinh N C Le L A Tuyen N Q Hung V D Nguyenand N T Nguyen ldquoInsight into adsorption mechanism oflead(II) from aqueous solution by chitosan loaded MnO2nanoparticlesrdquo Materials Chemistry and Physics vol 207 pp294ndash302 2018

[19] G Dulaquais H Planquette S LrsquoHelguen M J A Rijkenbergand M Boye ldquoThe biogeochemistry of cobalt in the Mediter-ranean SeardquoGlobal Biogeochemical Cycles vol 31 no 2 pp 377ndash399 2017

[20] O G Saglam and U Koklu ldquoAtomic absorption spectrometricdetermination of cobalt and nickel after preconcentration by theapplication of chelate adsorption on amino-modified silica-gelrdquoJournal of Trace and Microprobe Techniques vol 21 no 2 pp249ndash257 2003

[21] J Bown M Boye A Baker et al ldquoThe biogeochemical cycle ofdissolved cobalt in the Atlantic and the Southern Ocean southoff the coast of South Africardquo Marine Chemistry vol 126 no1-4 pp 193ndash206 2011

[22] M Castrillejo P J Statham G R Fones H Planquette F Idrusand K Roberts ldquoDissolved trace metals (Ni Zn Co Cd Pb Aland Mn) around the Crozet Islands Southern Oceanrdquo Journalof Geophysical Research Oceans vol 118 no 10 pp 5188ndash52012013

[23] G Dulaquais M Boye R Middag et al ldquoContrasting biogeo-chemical cycles of cobalt in the surface westernAtlantic OceanrdquoGlobal Biogeochemical Cycles vol 28 no 12 pp 1387ndash1412 2014

[24] R U Shelley N J Wyatt G A Tarran A P Rees P JWorsfold and M C Lohan ldquoA tale of two gyres Contrastingdistributions of dissolved cobalt and iron in the Atlantic Oceanduring an Atlantic Meridional Transect (AMT-19)rdquo Progress inOceanography 2016

[25] M A Saito A E Noble N Hawco et al ldquoThe accelerationof dissolved cobaltrsquos ecological stoichiometry due to biologi-cal uptake remineralization and scavenging in the AtlanticOceanrdquo Biogeosciences vol 14 no 20 pp 4637ndash4662 2017

[26] S Brunauer P H Emmett and E Teller ldquoAdsorption of gasesin multimolecular layersrdquo Journal of the American ChemicalSociety vol 60 no 2 pp 309ndash319 1938

[27] M Rafatullah O Sulaiman R Hashim and A AhmadldquoAdsorption of copper (II) chromium (III) nickel (II) and lead(II) ions from aqueous solutions bymeranti sawdustrdquo Journal ofHazardous Materials vol 170 no 2-3 pp 969ndash977 2009

[28] K Y Foo and B H Hameed ldquoInsights into the modeling ofadsorption isotherm systemsrdquo Chemical Engineering Journalvol 156 no 1 pp 2ndash10 2010

[29] H M Dung and P D Hien ldquoThe application and developmentof k0-standardization method of neutron activation analysis atDalat research reactorrdquo Journal of Radioanalytical and NuclearChemistry vol 257 no 3 pp 643ndash647 2003

[30] M D Ho Q T Tran V D Ho D V Cao and T S NguyenldquoQuality evaluation of the k 0-standardized neutron activationanalysis at theDalat research reactorrdquo Journal of Radioanalyticaland Nuclear Chemistry vol 309 no 1 pp 135ndash143 2016


[31] E P Barrett L G Joyner and P P Halenda ldquoThe determinationof pore volume and area distributions in porous substancesI Computations from nitrogen isothermsrdquo Journal of theAmerican Chemical Society vol 73 no 1 pp 373ndash380 1951

[32] W C Tsai S Ibarra-Buscano C C Kan C M Futalan M L PDalida and M W Wan ldquoRemoval of copper nickel lead andzinc using chitosan-coated montmorillonite beads in single-and multi-metal systemrdquo Desalination and Water Treatmentvol 57 pp 9799ndash9812 2016

[33] A M Cardenas-Pena J G Ibanez and R Vasquez-MedranoldquoDetermination of the point of zero charge for electrocoagula-tion precipitates from an iron anoderdquo International Journal ofElectrochemical Science vol 7 no 7 pp 6142ndash6153 2012

[34] T Mahmood M T Saddique A Naeem P Westerhoff SMustafa and A Alum ldquoComparison of different methods forthe point of zero charge determination of NiOrdquo Industrial ampEngineering Chemistry Research vol 50 no 17 pp 10017ndash100232011

[35] M Gheju I Balcu and G Mosoarca ldquoRemoval of Cr(VI)from aqueous solutions by adsorption on MnO2rdquo Journal ofHazardous Materials vol 310 pp 270ndash277 2016

[36] M Singh D N Thanh P Ulbrich N Strnadova and FStepanek ldquoSynthesis characterization and study of arsenateadsorption from aqueous solution by 120572- And 120575-phase man-ganese dioxide nanoadsorbentsrdquo Journal of Solid State Chem-istry vol 183 no 12 pp 2979ndash2986 2010

[37] Z L Zhu H M Ma R H Zhang Y X Ge and J F ZhaoldquoRemoval of cadmium using MnO2 loaded D301 resinrdquo Journalof Environmental Sciences vol 19 no 6 pp 652ndash656 2007

[38] Y RenN Li J Feng et al ldquoAdsorption of Pb(II) andCu(II) fromaqueous solution on magnetic porous ferrospinel MnFe2O4rdquoJournal of Colloid and Interface Science vol 367 no 1 pp 415ndash421 2012

[39] A Heidari H Younesi Z Mehraban and H HeikkinenldquoSelective adsorption of Pb(II) Cd(II) and Ni(II) ions fromaqueous solution using chitosan-MAA nanoparticlesrdquo Interna-tional Journal of Biological Macromolecules vol 61 pp 251ndash2632013

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018


International Journal ofInternational Journal ofPhotoenergy


Journal of

Chemistry


Advances inPhysical Chemistry

Hindawiwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2018

Bioinorganic Chemistry and ApplicationsHindawiwwwhindawicom Volume 2018

SpectroscopyInternational Journal of


Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Medicinal ChemistryInternational Journal of


NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Applied ChemistryJournal of



Biochemistry Research International


Enzyme Research


Journal of

SpectroscopyAnalytical ChemistryInternational Journal of


MaterialsJournal of



BioMed Research International Electrochemistry

International Journal of


Na

nom

ate

ria

ls


Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom


Neutron activation analysis (NAA) is a sensitive and spe-cial method for determining simultaneously a large numberof elements [8] One of the advantages of the NAA methodover the common spectrometric methods is that it allows usto directly analyze the samples in original forms without theuse of dissolution steps that may cause the sample dilutionand contaminationWithin theNAA the preconcentration ofthe trace elements from the aqueous samples such as seawaterabsorbed on solid materials is usually preferred among theother methods However a drawback of this method is that itis not able to analyze the water samples since the radiolysis ofwater itself may cause a release of radiogas or even anexplosion out of the container [9] Hence the adsorptionused to preconcentrate the elements from the water ontothe solid phase is a promising method for the detectionof trace elements in seawater as well as in other solutionsSome adsorbents have been used for these preconcentrationsteps such as the magnesium oxide [9] charcoal [10ndash14] andaluminium and iron(III) oxides [15] However the use ofnanooxide as an adsorbent material for the retention of traceelements from seawater before being determined by the NAAmethod has still been limited so far

In fact the nanomaterials which have their own physic-ochemical properties and therefore differ from the nonnano-materials have been applied to a variety of areas Among thenanomaterials the manganese oxides with various types ofcrystalline structures such as 120572- 120573- 120574- MnO2 have beenextensively studied owing to their structural varieties andexcellent chemical characteristics As a result they have beenapplied to different areas such as batteries molecular sievescatalysts and adsorbents [16 17] However the use of 120574-MnO2 nanomaterial as a solid phase for the preconcentrationof cobalt from seawater has still been rarely studied

In the present work the 120574-MnO2 nanomaterial is used asa preconcentration agent to extract cobalt from the seawatercollected at Hon Rom Beach Phan Thiet City Binh ThuanProvince Vietnam before applying the NAA method todetermine its concentration Furthermore factors affectingthe adsorption capacity of this nanomaterial such as the pHadsorption time and initial cobalt concentration are alsoinvestigated within the present work

2 Experimental Method

21 Reagents and Materials The cobalt(II) ion is used as anadsorbate A 1000mgL standard stock solution containingeach set of cobalt(II) ions is prepared by dissolving theCo(NO3)2 (Merck pa) in the double-distilled water TheHNO3 (Merck pa) and NaOH (Merck pa) are then usedto adjust the pH of the solution The 120574-MnO2 nanomaterialis synthesized via the reaction between the potassium per-manganate (KMnO4) (Merck pa) solution and the ethanol(C2H5OH) (Merck pa) at the room temperature as reportedpreviously in [17 18] A 300ml potassium permanganate(KMnO4) saturated solution is gradually placed into a 300mlof the mixture between the ethanol (C2H5OH) and thedistilled water which is then strongly agitated during 8 hTheobtained solid precipitate is dried at 100∘C in 12 h After that

Figure 1 Hon Rom Beach Phan Thiet City Binh Thuan ProvinceVietnam where the seawater samples are collected

it is cleaned several times by using the distilled water in orderto get the 120574-MnO2 products

Seawater collected from the Hon Rom Beach PhanThiet City Binh Thuan Province Vietnam at the position of10∘57N-108∘19W (see Figure 1) is filtered through 02120583mSar-tobran 300 cartridges (Sartorius) which are later used for theDCo analyses The samples are collected in the acid cleaned250mL LDPE Nalgene bottles which are rinsed 5 timestogether with the samples before the collection After thatthe processes are similar to those presented in Section 2 of[19] except that HNO3 at 001M (Merck) has been used toacidify the sampleswithin an hour instead of using ultrapureHCl as in [19]

22 Instruments The phase of the crystalline structure isdetermined by using the X-ray diffractometer (XRD) D5000made by Siemens (Germany) with the X-ray radiation ofCuK120572 and wavelength 120582 = 15406 A The ultrahigh resolu-tion scanning electron microscopy (SEM) S-4800 made byHitachi (Japan) and the transmission electron microscope(TEM) JEM1010made by JEOL (Japan) are used to investigatethemorphology of thematerialsThe surface area of themate-rials is calculated within the BrunauerndashEmmettndashTeller (BET)theory [26]The concentration of the samples before and afterthe adsorption is determined by using the atomic absorptionspectrophotometer (AAndash7000) made by Shimadzu (Japan)In addition the pHmeasurements are performed using a pH-meter Mi-150 (MARTINI Instruments made in Romania)The latter is standardized using the HANNA instrumentalbuffer solutions with different values of pH namely 401 plusmn001 701 plusmn 001 and 1001 plusmn 001 A temperature-controlledshaker (Model IKA R5) is used for the studies of theequilibrium states





119876max (mgg) 9091 119870119871 (Lmg) 05430 1999 02918


Sips 119902119890 =119876119878 sdot 119862119890

120573119878

1 + 120572119904 sdot 119862119890120573119878 119876119904 (mgg) 9500 120572119904 (Lmg) 09810 120573119904 05694 1593 01751




(1)


119902 =(119862119900 minus 119862119890) times 119881119898

(2)



10

20

30

40

50

60

70

Inte

nsity

(au

)

25 30 35 40 45 50 55 60 65 70 75 80202-theta (deg)

222∘

378∘

425∘

563∘

657∘

-MnO2










100 nm

(a)

134 nm

167nm

129 nm

105 nm

105 nm 114 nm

151 nm

100 nm

(b)










0 1 2 3 4 5 6 70

20

40

60

80

100

rem

oval

pH

300 mgL150mgL

(a)

60

80

100

re

mov

al

150mgL170mgL220mgL

50 100 150 200 250 3000Time (mins)

(b)


0 30 60 90 120 15060

70

80

90

100

ExperimentLangmuir

FreundlichSips

qe

(mg

g)

Ce (mgL)




0

20

40

60

80

100

Energy (keV)

Zn-65

Co-60 Co-60

0

200

400

600

800

1000

1200C

ount

s

Cou

nts

500 1000 1500 20000Energy (keV)

1100 1150 1200 1250 1300 1350

13325 keV11732 keV

1115 keV


0 500 1000 1500 2000

0

50

100

150

200

Energy (keV)

Sc-46

Zn-65

Co-60Co-60

Fe-59 Fe-59

Cou

nts

0

200

400

600

800

1000

1200

Cou

nts

Energy (keV)1100 1150 1200 1250 1300 1350

1291 kev1099 kev

1173 kev1332 kev

1115 kev

1120 kev





Cobalt








4 Conclusions





References















































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls








119876max (mgg) 9091 119870119871 (Lmg) 05430 1999 02918


Sips 119902119890 =119876119878 sdot 119862119890

120573119878

1 + 120572119904 sdot 119862119890120573119878 119876119904 (mgg) 9500 120572119904 (Lmg) 09810 120573119904 05694 1593 01751




(1)


119902 =(119862119900 minus 119862119890) times 119881119898

(2)



10

20

30

40

50

60

70

Inte

nsity

(au

)

25 30 35 40 45 50 55 60 65 70 75 80202-theta (deg)

222∘

378∘

425∘

563∘

657∘

-MnO2










100 nm

(a)

134 nm

167nm

129 nm

105 nm

105 nm 114 nm

151 nm

100 nm

(b)










0 1 2 3 4 5 6 70

20

40

60

80

100

rem

oval

pH

300 mgL150mgL

(a)

60

80

100

re

mov

al

150mgL170mgL220mgL

50 100 150 200 250 3000Time (mins)

(b)


0 30 60 90 120 15060

70

80

90

100

ExperimentLangmuir

FreundlichSips

qe

(mg

g)

Ce (mgL)




0

20

40

60

80

100

Energy (keV)

Zn-65

Co-60 Co-60

0

200

400

600

800

1000

1200C

ount

s

Cou

nts

500 1000 1500 20000Energy (keV)

1100 1150 1200 1250 1300 1350

13325 keV11732 keV

1115 keV


0 500 1000 1500 2000

0

50

100

150

200

Energy (keV)

Sc-46

Zn-65

Co-60Co-60

Fe-59 Fe-59

Cou

nts

0

200

400

600

800

1000

1200

Cou

nts

Energy (keV)1100 1150 1200 1250 1300 1350

1291 kev1099 kev

1173 kev1332 kev

1115 kev

1120 kev





Cobalt








4 Conclusions





References















































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls







100 nm

(a)

134 nm

167nm

129 nm

105 nm

105 nm 114 nm

151 nm

100 nm

(b)










0 1 2 3 4 5 6 70

20

40

60

80

100

rem

oval

pH

300 mgL150mgL

(a)

60

80

100

re

mov

al

150mgL170mgL220mgL

50 100 150 200 250 3000Time (mins)

(b)


0 30 60 90 120 15060

70

80

90

100

ExperimentLangmuir

FreundlichSips

qe

(mg

g)

Ce (mgL)




0

20

40

60

80

100

Energy (keV)

Zn-65

Co-60 Co-60

0

200

400

600

800

1000

1200C

ount

s

Cou

nts

500 1000 1500 20000Energy (keV)

1100 1150 1200 1250 1300 1350

13325 keV11732 keV

1115 keV


0 500 1000 1500 2000

0

50

100

150

200

Energy (keV)

Sc-46

Zn-65

Co-60Co-60

Fe-59 Fe-59

Cou

nts

0

200

400

600

800

1000

1200

Cou

nts

Energy (keV)1100 1150 1200 1250 1300 1350

1291 kev1099 kev

1173 kev1332 kev

1115 kev

1120 kev





Cobalt








4 Conclusions





References















































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls





0 1 2 3 4 5 6 70

20

40

60

80

100

rem

oval

pH

300 mgL150mgL

(a)

60

80

100

re

mov

al

150mgL170mgL220mgL

50 100 150 200 250 3000Time (mins)

(b)


0 30 60 90 120 15060

70

80

90

100

ExperimentLangmuir

FreundlichSips

qe

(mg

g)

Ce (mgL)




0

20

40

60

80

100

Energy (keV)

Zn-65

Co-60 Co-60

0

200

400

600

800

1000

1200C

ount

s

Cou

nts

500 1000 1500 20000Energy (keV)

1100 1150 1200 1250 1300 1350

13325 keV11732 keV

1115 keV


0 500 1000 1500 2000

0

50

100

150

200

Energy (keV)

Sc-46

Zn-65

Co-60Co-60

Fe-59 Fe-59

Cou

nts

0

200

400

600

800

1000

1200

Cou

nts

Energy (keV)1100 1150 1200 1250 1300 1350

1291 kev1099 kev

1173 kev1332 kev

1115 kev

1120 kev





Cobalt








4 Conclusions





References















































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls







Cobalt








4 Conclusions





References















































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls

















































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls




determination of cobalt in seawater using neutron activation...

Documents