Construction Of Fe(ii)/sulfite Oxidation System And Investigation Of The Transformation Mechanisms Of As(iii)

Arsenic pollutants,including arsenite?As????and arsenate?As?V??,is widely occuring in many natural aquatic environments and a variety of relevant industrial effluents.Due to their hypertoxicity,carcinogenicity and stong mobility,As???has been stipulated as priority pollutant.Compared with As?V?,As???is more toxic and mobile,which results in inferior immobilization efficiency in many current arsenic-removal technologies.Therefore the pre-oxidation of As???is a critical link in many current arsenic remediation processes,but it often consumes additional chemical reagents and/or energy.This study we attempt to developed a green and cost-effictive method of oxidizing As???with the comprehensive utilization of sulfite wastewaters duiring the industry desulfurization process.Firstly,this study preliminarily investigated the oxidation ability of Fe???/sulfite reaction system by examining its application in Rhodamine B?RhB?decolouration.In this system,the effects of reactant initial concentration,solution initial pH,Fe-ligands and special alcohols?EtOH and TBA?on the decolouration efficiency of RhB were also examined.Besides,active radicals were detected by fluorescence spectroscopy to probe the underlying reaction mechanisms.The experimental results demonstrate that highly oxiditive species,i.e.,SO₄^·-and^·OH,were produced in Fe???/S???reaction system.When organic pollutant RhB were introduced into the above reaction system,it can scaveng these active radicals,leading to oxidative decolouration.Secondly,this study furtherly evaluated the applicability of Fe???/S???/As???system for simultaneous oxidation of As???and S???in one process.The effects of reactant initial concentration,solution initial pH,Fe-ligands and special alcohols?EtOH and TBA?on the oxidation of As???and S???were also examined.It was found that pH and S???concentration were the key effects on the oxidation of As???and S???.Besides,by Fe-ligands interference experiment and calculation of the equilibrium state of iron ion species,the electron transfer between iron ion and ligand S???is the key to the generation of free radical and further oxidation of As???.Though fluorescence spectroscopy technology with coumarin and radical scavenger experiment with EtOH and TBA,the active radicals(etc.,^·OH?SO₄^·-?SO₅^·-)and in stu formed peroxymonosulfate were the major reactive species responsible for the simultaneous oxidation of As???and S???.Finally,based on the above study,the free radical reaction mechanism of Fe???/S???reaction system was further defined,and the reaction mechanism of As???oxidative transformation was proposed.