Oxidative dissolution of Cr(OH)_(3) and mixed Fe-Cr(Ⅲ)phases by aqueous Mn(Ⅲ)-pyrophosphate complex  

作　　者：Mismel Ruiz-Garcia Jordan Stanberry Giovanna Ballerini Ribeiro Vasileios Anagnostopoulos 

机构地区：[1]Department of Chemistry,University of Central Florida,Orlando FL 32816,USA

出　　处：《Journal of Environmental Sciences》2024年第5期105-113,共9页环境科学学报（英文版）

基　　金：Nuclear Regulatory Commission(NRC)for the funds provided under award 31310019M0010。

摘　　要：The key role of manganese(Mn)in the biogeochemical cycle of trace elements has been of great interest in recent years.Nevertheless,the redox properties of aqueous Mn(Ⅲ)have been studied to a lesser extent.Mn(Ⅲ)is not stable in solution by itself.However,when complexed with inorganic ligands,it has shown potential to oxidize and reduce trace elements.In the present study,we are exploring the redox characteristics of the complex Mn(Ⅲ)-Pyrophosphate(Mn(Ⅲ)-PP).This complex is stable over a wide range of pH values but requires the ratio of Mn:PP to be less than 1:6.Specifically,the redox reaction of chromium(Cr(Ⅲ))and Mn(Ⅲ)-PP is investigated.A solid,Cr(OH)_(3),is used as a source of Cr(Ⅲ).For this reaction,environmentally relevant parameters,such as pH,ionic strength,ratio Mn(Ⅲ)/Cr(Ⅲ),and excess of ligand,were assessed.Results showed that Mn(Ⅲ)can effectively oxidize Cr(Ⅲ)to Cr(Ⅵ),taking about 15 days for the reaction to complete.This reaction occurs only under acidic conditions(pH4),and with a low excess of Pyrophosphate.The initial Mn(Ⅲ)concentration decreases as the Cr(Ⅵ)is produced,and Cr(Ⅵ)can be adsorbed back into the Cr(OH)_(3)surface,limiting the mobility of this toxic species.Despite this adsorption,significant amounts of Cr(VI)are release in the aqueous phase.This study shows the importance of a mobile species(Mn-PP complex)in the oxidation of Cr(Ⅲ)and the release of Cr(Ⅵ)to the environment.

关 键 词：Chromium MANGANESE Pyrophosphate complex SORPTION Ionic strength Redox 

分 类 号：X50[环境科学与工程—环境工程]