Enhanced Removal Of Se???from Water Via Pre-corrosion Of Zerovalent Iron Using H₂O₂/HCl

Selenium(Se)is a necessary trace nutrient element,but elevated level of Se would pose serious risks to human and various living organics.Water is the main source of selenium intake.Thus,strict standards have been implemented for Se in wastewater prior to discharge.However,certain industrial wastewaters from refining,mining,and smelting contain high concentrations of Se and a variety of coexisting ions such as sulfate.Hence,efficient technologies for Se removal from water are in great demand.The interaction of Se(?)with most metal oxides is predominantly via outer sphere complexation,which is subject to interference induced by coexisting anions.Thereby,the removal of Se(?)is inefficient by adsorption or ion exchange.Chemical reduction of Se(?)into Se(?)or lower-valent state is regarded as an effective strategy for its efficient remove from water.Zero-valent iron(ZVI)is a well-known inexpensive material with moderate reducing power for water decontamination.Although the removal of Se(?)from water by using zero-valent iron(ZVI)is a promising method,the passivation of ZVI severely inhibits its performance.It is important to enhance ZVI reactivity sustainably and economically for effective removal of Se(VI)by ZVITo overcome such issue,an efficient technique was developed to enhance Se(VI)removal via pre-corrosion of ZVI with H2O2/HCl in a short time(15 min).The resultant pcZ? suspension was weakly acidic(pH 4.56)and contained abundant aqueous Fe2+.57Fe Mossbauer spectroscopy showed that pcZ? mainly consisted of Fe0(66.2%),hydrated ferric oxide(26.3%),and Fe3O4(7.5%).Efficient removal of Se(?)from sulfate-rich solution was achieved by pcZ? compared with Z?(in the absence and presence of H2O2)and acid-pretreated ZVI.Moreover,the efficient removal of Se(?)by pcZ? sustained over a broad pH range(3-9)due to its strong buffering power.It is not necessary to conduct the anaerobic environment.The presence of chloride,carbonate,nitrate,and common cations(Na+,K+,Ca2+,and Mg2+)posed negligible influence on the removal of Se(VI)by pcZ?,while the inhibitory effect induced by sulfate,silicate,and phosphate indicated the significance of Se(?)adsorption as a prerequisite step for its removal.The continued consumption of aqueous Fe2+ was associated with Se(?)removal,and X-ray absorption near edge structure revealed that the main pathway for Se(?)removal by pcZ? was a stepwise reduction of Se(?)to Se(?)and then Se0 as the dominant final state(78.2%).Moreover,higher electron selectivity of pcZ? and the efficient Se(?)removal were attributed to the enhanced enrichment of Se oxyanions via hydrous ferric oxides(HFO)prior to their reduction.Therefore,this study provided a promising strategy to enhance Z? reactivity in wastewater treatment and remove Se(?)from sulfate-rich solution.