Development of speciation scheme for cadmium, copper, lead and zinc in water using ultrafiltration and different solid sorbents

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dc.contributor.authorSuitcharit, Charuwan
dc.date.accessioned2014-11-03T02:27:17Z
dc.date.available2014-11-03T02:27:17Z
dc.date.issued2006
dc.descriptionPhDen_US
dc.description.abstractA method for the speciation studies of dissolved metal species at natural concentration levels has been developed. The method is based on a combination of physical characterization by size fractionation using ultrafiltration and chemical characterization by retention studies on different solid sorbents. The ultrafiltration offers information on size at different molecular-weight levels, which are based on the molecular weight cutoff of its membranes. The different sorbents, namely, cation-exchange resin Chelex- 100, anion-exchange resin Dowex 1-X8 and C-18 reversed phase were used in column systems for the discrimination of lability of operationally-defined classes of the metal species among its species with different charges or chemical behaviour. The retention of Cd, Cu, Pb and Zn in each size fraction onto the sorbents at different pH conditions was investigated with both individual columns and three-columns systems. Experiments were performed with metals in the presence of model ligands, namely, nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), humic acid (HA), 8- hydroxyquinoline-5-sulphonic acid (SOX) and 8-hydroxyquinoline (OX). The results obtained were compared with those computed according to theoretical species distribution of all the metal species as a function of pH except for the M-HA complexes. Results have shown that the pH range from 5.5 to 7.5 plays an important role in speciation patterns of the metal species in the presence of HA except for Cd in which cadmium-humated coprecipitation was observed. The speciation patterns of the metal species in the presence of EDTA seem to be independent of pH between pH 5.5 to 7.5 and there are similar to patterns in the presence of SOX and OX except for Cd and Zn, which have little effect on speciation patterns. The change of pH slightly affects speciation patterns of the metal species in the presence of NTA. The arrangement of three-columns systems was investigated by changing the column sequence in series. Six types of three-columns combination were used for the study of retention behaviour of metals in the presence of different ligands at natural pH. The investigation demonstrates that the sequence of column gives speciation patterns of the system from different points of view. However, the overall trend of retention of the metals in the presence of EDTA, OX and HA onto three-columns systems is not significantly different among the six types of combinations at 95% confidence level by ANOVA testing. Type C with the sequence: Chelex-100, Dowex 1-X8 and C-18 columns, was selected to apply for the speciation studies of dissolved metals in Songkhla Lake waters. Total recoveries of all the metals were in the range of 96% to 110%.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/312
dc.language.isoenen_US
dc.subjectChemical scienceen_US
dc.subjectSpeciation schemeen_US
dc.subjectUltrafiltrationen_US
dc.subjectSolid sorbentsen_US
dc.titleDevelopment of speciation scheme for cadmium, copper, lead and zinc in water using ultrafiltration and different solid sorbentsen_US
dc.typeThesisen_US
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