Coprecipitation mechanisms of Zn by birnessite formation and its mineralogy under neutral pH conditions

作     者：Shota Tajima Shigeshi Fuchida Chiharu Tokoro Shota Tajima;Shigeshi Fuchida;Chiharu Tokoro

作者机构：Graduate School of Creative Science and EngineeringWaseda University3-4-1 OkuboShinjuku-kuTokyo 169-8555Japan Faculty of Science and EngineeringWaseda University3-4-1 OkuboShinjuku-kuTokyo 169-8555Japan Faculty of EngineeringThe University of Tokyo7-3-1 HongoBunkyo-kuTokyo 113-8656Japan 

出 版 物：《Journal of Environmental Sciences》 (环境科学学报（英文版）)

年 卷 期：2022年第34卷第11期

页      面：136-147页

核心收录：

学科分类：081803[工学-地质工程] 08[工学] 0818[工学-地质资源与地质工程] 

基　　金：supported by the Research Institute of the Sustainable Future Society and Research Organization for Open Innovation Strategy, Waseda University a grant from the Japan Mining Industry Association 

主　　题：δ-MnO2 Zinc removal Surface complexation X-ray absorption fine structure 

摘      要：Birnessite(δ-Mn(IV)O_(2))is a great manganese(Mn)adsorbent for dissolved divalent *** this study,we investigated the coprecipitation mechanism of δ-MnO_(2) in the presence of Zn(II)and an oxidizing agent(sodium hypochlorite)under two neutral pH values(6.0 and 7.5).Themineralogical characteristics and Zn–Mn mixed products were compared with simple surface complexation by adsorption modeling and structural *** coprecipitation experiments at different Zn/Mn molar ratios showed a Langmuir-type isotherm at pH 6.0,which was similar to the result of adsorption experiments at pH 6.0 and 7.5.X-ray diffraction and X-ray absorption fine structure analysis revealed triple-corner-sharing innersphere complexation on the vacant sites was the dominant Zn sorption mechanism on δ-MnO_(2) under these experimental conditions.A coprecipitation experiment at pH 6.0 produced some hetaerolite(ZnMn(Ⅲ)_(2)O_(4))and manganite(γ-Mn(Ⅲ)OOH),but only at low Zn/Mn molar ratios(1).These secondary precipitates disappeared because of crystal dissolution at higher Zn/Mn molar ratios because they were thermodynamically ***(ZnMn(IV)_(3)O_(7)•2H_(2)O)was produced in the coprecipitation experiment at pH 7.5 with a high Zn/Mn molar ratio of *** resulted in a Brunauer–Emmett–Teller(BET)-type sorption isotherm,in which formation was explained by transformation of the crystalline structure ofδ-MnO_(2) to a tunnel *** experiments demonstrate that abiotic coprecipitation reactions can induce Zn–Mn compound formation on theδ-MnO_(2) surface,and that the pH is an important controlling factor for the crystalline structures and thermodynamic stabilities.