Study of Colloidal Complexation Behavior in Aquatic System of Fe-As-OM
Arsenic(As),a kind of metalloid element,has drawn public concerns due to its characters of carcinogenicity and bio-accumulation which incur considerable hazards in aquatic environment.The colloidal complexation behavior of As in the process of its migration in the aquatic environment is the key process of its morphology change;however,researches on the migration of As based on the colloidal complexation behaviors of Fe-As or Fe-As-organic matter(Fe-As-OM)has yet been scarcely reported.In this study,the Fe-As colloidal complexation behavior were analyzed at different values of pH and initial Fe concentration,meanwhile,the effects of different OM and anions on the colloidal complexation behavior and the Zeta potential were investigated.The results showed that pH was the key to the formation of Fe-As colloidal complexes,colloidal complexes could be formed under either weakly acidic condition or alkaline condition;and with the increases of value of pH,the colloidal complexes were gradually converted into flocs forming precipitates;and the formation amount of colloidal complexes increased with the initial Fe concentration,however the presence of OM inhibited this process.Besides,the presence of anion alone(except SiO32-)promoted the formation of colloidal complexes,but when OM coexisted,all anions would inhibit the formation of colloidal complexes,among others,SiO32-was the most significant inhibitory anion.The Zeta potentials of the colloidal complexes in different systems varied,and overall Fe-As and Fe-As-OM systems were positively charged,while the colloidal complexes in the oxalic acid system appeared to be negatively charged,and played a dominant role in the system.Therefore,the study of the colloidal complexation behavior of As in the aquatic environment could provide an important reference for the management of As pollution in water bodies,especially in the field of drinking water safety.
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