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Surface Complexation Modeling Of Cd(Ⅱ) Adsorption On Montmorillonite/Kaolinite-Bacillus Subtilis Composites

Posted on:2016-04-23Degree:MasterType:Thesis
Country:ChinaCandidate:N WangFull Text:PDF
GTID:2271330461996051Subject:Environmental Science
Abstract/Summary:PDF Full Text Request
The mobility and fate of heavy metals in environments were determined by the adsorption of metal irons on soil and sediment. Surface complexation modeling(SCM) has emerged as a powerful tool for describing the adsorption processes and mechanisms of heavy metals on the surface of soil solid components. The simulation can be used to predict the adsorption and distribution of heavy metals in soils, and to evaluate the risk of heavy metal contamination. In the current study, the atomic force microscope(AFM), potentiometric titrations, zeta potential measurement, isothermal adsorption, EXAFS analysis and SCMs were employed to investigate the surface properties, Cd adsorption characteristics, distribution of cadmium on gram-positive bacteria B.subtilis, montmorillonite,kaolinite and their composites.We developed molecular-level constant capacity models of Cd adsorption on montmorillonite, kaolinite, B.subtilis, and adopted CA-SCM to describe the adsorption of Cd on the montmorillonite/kaolinite-B.subtilis composites. The adsorption of Cd on the surface of the composites can be described by CA-SCM over the whole p H range studied. More negative charge surface of the montmorillonite/kaolinite –B.subtilis composite compare to end-member phase may be responsible for the deviation of prediction of Cd sorption on the composite at p H < 5 and p H < 4, respectively. The complexes X2 Cd, SOCd+, R-COOCd+ and R-POCd+ were the predominant species of Cd on the surface of the composites over the whole p H range studied. Montmorillonite and B.subtilis controlled the adsorption of Cd on the montmorillonite-B.subtilis and kaolinite-B.subtilis composite, respectively. The distribution of the total adsorbed Cd between the montmorillonite and B.subtilis fractions of the composite predicted by CA-SCM(71.4% : 28.6%) matched the results obtained from EXAFS spectra analysis(69.1% : 30.9%).
Keywords/Search Tags:Surface complexation model, component additivity approach, composite, EXAFS, Cd adsosption
PDF Full Text Request
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