Mechanistic insight into Cr(Ⅵ)retention by Si-containing ferrihydrite  

作　　者：Ying Hu Qiang Xue Honghan Chen Huaming Guo Kenneth C.Carroll Song Wang 

机构地区：[1]MOE Key Laboratory of Groundwater Circulation and Environmental Evolution,School of Water Resources and Environment,China University of Geosciences(Beijing),Beijing 100083,China [2]Beijing Key Laboratory of Water Resources and Environmental Engineering,School of Water Resources and Environment,China University of Geosciences,Beijing 100083,China [3]State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Beijing 100083,China [4]Plant&Environmental Science,New Mexico State University,NM 88003,USA [5]Institute of Theoretical Chemistry,College of Chemistry,Jilin University,Changchun 130023,China

出　　处：《Journal of Environmental Sciences》2024年第5期217-225,共9页环境科学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China(Nos.42130509 and 42177061);the National Key Research and Development Program of China(No.2020YFC1808300);Jilin Province Science and Technology Development Projects(No.20190303056SF)。

摘　　要：Hexavalent chromium[Cr(Ⅵ)]causes serious harm to the environment due to its high toxicity,solubility,and mobility.Ferrihydrites(Fh)are the main adsorbent and trapping agent of Cr(Ⅵ)in soils and aquifers,and they usually coexist with silicate(Si),forming Si-containing ferrihydrite(Si-Fh)mixtures.However,the mechanism of Cr(Ⅵ)retention by Si-Fh mixtures is poorly understood.In this study,the behaviors and mechanisms of Cr(Ⅵ)adsorption onto Si-Fh with different Si/Fe molar ratios was investigated.Transmission electron microscope,Fourier transform infrared spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,and other techniques were used to characterize Si-Fh and Cr(Ⅵ)-loading of Si-Fh.The results show that specific surface area of Si-Fh increases gradually with increasing Si/Fe ratios,but Cr(Ⅵ)adsorption on Si-Fh decreases with increasing Si/Fe ratios.This is because with an increase in Si/Fe molar ratio,the point of zero charge of Si-Fh gradually decreases and electrostatic repulsion between Si-Fh and Cr(Ⅵ)increases.However,the complexation of Cr(Ⅵ)is enhanced due to the increase in adsorbed hydroxyl(A-OH-)on Si-Fh with increasing Si/Fe molar ratio,which partly counteracts the effect of the electrostatic repulsion.Overall,the increase in the electrostatic repulsion has a greater impact on adsorption than the additional complexation with Si-Fh.Density functional theory calculation further supports this observation,showing the increases in electron variation of bonding atoms and reaction energies of inner spherical complexes with the increase in Si/Fe ratio.

关 键 词：Hexavalent chromium FERRIHYDRITE Si/Fe ratio Cr(Ⅵ)Adsorption 

分 类 号：X50[环境科学与工程—环境工程] X131