Sequestration of hexavalent chromium by Fe(II)/Fe(III) hydroxides: Structural Fe(II) reactivity and PO43− effect

摘要: Abstract As Fe(II)-rich minerals, Fe(II)/Fe(III) hydroxides were intensively investigated in the sequestration of aqueous Cr(VI). Results showed that content Cr(VI) sequestrated ([Cr(VI)] se ) was proportional to absolute structural Fe(II) ( Fe(II)). Molecular ratios [Fe(II)] co (consumed Fe(II))/[Cr(VI)] close 3:1, theoretical ratio, indicated high reactivity Fe(II), which could also be confirmed by fact 278 mg Cr(VI)/g achieved. In other words, negligible inhibitory effect deduced case surface Cr(III)-solids, responsible for limited previous reported Fe(II)-contained minerals. Large area induced adsorption, accompanied simultaneous reduction, supposed govern rapid reaction within initial 10 min. Reaction 10–20 min well fit a pseudo-first-order model, demonstrating electron transfer efficiency from inner adsorbed/aqueous Cr(VI), though Cr(III)-solids formed. containing end solid products found goethite, CrOOH and Cr(OH) 3 , benefit establish interfacial reduction–precipitation mechanism sequestration. The negative OH − on availability cases [Fe(II)]/[OH ] higher or lower than 1:1. Simultaneous PO 4 addition caused vivianite generation, resulting decrease. This investigation gave implication applied regulated reduction precipitation possible heavy metal ions.