Oxidation of Cr(Ⅲ) on birnessite surfaces: The effect of goethite and kaolinite  

作　　者：Laiyuan Zhong Jiewen Yang Liming Liu Baoshan Xing 

机构地区：[1]Department of Resources and Environmental Sciences, College of Agriculture, Guangdong Ocean University [2]Stockbridge School of Agriculture, University of Massachusetts [3]Department of Land Resources Management, College of Resources and Environmental Sciences, China Agricultural University

出　　处：《Journal of Environmental Sciences》2015年第11期8-14,共7页环境科学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China (Nos. 41130526, 41101214 and 41371316);the USDA NIFA Hatch Program (No. MAS00475)

摘　　要：Oxidation of Cr（Ⅲ） by manganese oxides may pose a potential threat to environments due to the formation of toxic Cr（Ⅵ） species. At present, it was still unclear whether the extent of Cr（Ⅲ） oxidation and fate of Cr（Ⅵ） would be changed when manganese oxides co-exist with other minerals, the case commonly occurring in soils. This study investigated the influence of goethite and kaolinite on Cr（Ⅲ） oxidation by birnessite under acidic p H condition（p H 3.5）and background electrolyte of 0.01 mol/L Na Cl. Goethite was found not to affect Cr（Ⅲ）oxidation, which was interpreted as the result of overwhelming adsorption of cationic Cr（Ⅲ） onto the negatively-charged birnessite（point of zero charge（PZC） 〈 3.0） rather than the positively-charged goethite（PZC = 8.8）. However, more Cr（Ⅵ） would be retained by the surface with the increase in addition of goethite because of its strong ability on adsorption of Cr（Ⅵ） at low p H. Moreover, either Cr（Ⅲ） oxidation or distribution of the generated Cr（Ⅵ）between the solid and solution phases was not affected by kaolinite（PZC 〈 3.0）, indicating its low affinity for Cr species. Reactions occurring in the present mixed systems were suggested, which could be partly representative of those in the soils and further indicates that the mobility and risk of Cr（Ⅵ） would be decreased if goethite was present.Oxidation of Cr（Ⅲ） by manganese oxides may pose a potential threat to environments due to the formation of toxic Cr（Ⅵ） species. At present, it was still unclear whether the extent of Cr（Ⅲ） oxidation and fate of Cr（Ⅵ） would be changed when manganese oxides co-exist with other minerals, the case commonly occurring in soils. This study investigated the influence of goethite and kaolinite on Cr（Ⅲ） oxidation by birnessite under acidic p H condition（p H 3.5）and background electrolyte of 0.01 mol/L Na Cl. Goethite was found not to affect Cr（Ⅲ）oxidation, which was interpreted as the result of overwhelming adsorption of cationic Cr（Ⅲ） onto the negatively-charged birnessite（point of zero charge（PZC） 〈 3.0） rather than the positively-charged goethite（PZC = 8.8）. However, more Cr（Ⅵ） would be retained by the surface with the increase in addition of goethite because of its strong ability on adsorption of Cr（Ⅵ） at low p H. Moreover, either Cr（Ⅲ） oxidation or distribution of the generated Cr（Ⅵ）between the solid and solution phases was not affected by kaolinite（PZC 〈 3.0）, indicating its low affinity for Cr species. Reactions occurring in the present mixed systems were suggested, which could be partly representative of those in the soils and further indicates that the mobility and risk of Cr（Ⅵ） would be decreased if goethite was present.

关 键 词：Cr（Ⅲ） oxidation Birnessite Goethite Kaolinite 

分 类 号：X53[环境科学与工程—环境工程]