Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 13, issue 19
Biogeosciences, 13, 5557–5566, 2016
https://doi.org/10.5194/bg-13-5557-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 5557–5566, 2016
https://doi.org/10.5194/bg-13-5557-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 06 Oct 2016

Research article | 06 Oct 2016

Surface complexation modeling of Cd(II) sorption to montmorillonite, bacteria, and their composite

Ning Wang1,2,*, Huihui Du1,2,*, Qiaoyun Huang1,2, Peng Cai1,2, Xingmin Rong2, Xionghan Feng2, and Wenli Chen1 Ning Wang et al.
  • 1State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China
  • 2Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
  • *These authors contributed equally to this work.

Abstract. Surface complexation modeling (SCM) has emerged as a powerful tool for simulating heavy metal adsorption processes on the surface of soil solid components under different geochemical conditions. The component additivity (CA) approach is one of the strategies that have been widely used in multicomponent systems. In this study, potentiometric titration, isothermal adsorption, zeta potential measurement, and extended X-ray absorption fine-structure (EXAFS) spectra analysis were conducted to investigate Cd adsorption on 2 : 1 clay mineral montmorillonite, on Gram-positive bacteria Bacillus subtilis, and their mineral–organic composite. We developed constant capacitance models of Cd adsorption on montmorillonite, bacterial cells, and mineral–organic composite. The adsorption behavior of Cd on the surface of the composite was well explained by CA-SCM. Some deviations were observed from the model simulations at pH < 5, where the values predicted by the model were lower than the experimental results. The Cd complexes of X2Cd, SOCd+, R-COOCd+, and R-POCd+ were the predominant species on the composite surface over the pH range of 3 to 8. The distribution ratio of the adsorbed Cd between montmorillonite and bacterial fractions in the composite as predicted by CA-SCM closely coincided with the estimated value of EXAFS at pH 6. The model could be useful for the prediction of heavy metal distribution at the interface of multicomponents and their risk evaluation in soils and associated environments.

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We developed surface complexation model for Cd(II) adsorption on montmorillonite, B. subtilis, and their composite. The Cd adsorption behavior onto the composite can be described by a component additivity approach (CA-SCM). The Cd complexes of X2Cd, SOCd+, R-COOCd+, and R-POCd+ were the predominant species on the composite over the pH range of 3 to 8. The model could be useful for the prediction of heavy metal distribution at the interface of multicomponents and their risk evaluation in soils.
We developed surface complexation model for Cd(II) adsorption on montmorillonite, B. subtilis,...
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