Enhanced removal of selenate from mining effluent by H2O2/HCl-pretreated zero-valent iron

Abstract

Direct use of zero-valent iron (ZVI) in reductive removal of selenate (Se(VI)) is inefficient due to the intrinsic passive layer of ZVI. Here we observed that ZVI pretreated with H2O2 (P-ZVI-O) performs much better in Se(VI) removal from a mining effluent than other three modes of ZVI alone, acid washing ZVI (P-ZVI-A), and simultaneous addition of H2O2 and ZVI (ZVI-O) as well. The P-ZVI-O exhibits exceptionally high Se(VI) removal at a low dosage, wide pH range, with Se dropping down from 93.5 mg/L to <0.4 μg/L after 7-h reaction. Interestingly, the initial pH (2–6) of the mining effluent exerted little influence on the final Se(VI) removal. H2O2/HCl pretreatment results in the formation of various reducing corrosion products (e.g. Fe3O4, FeO and Fe2+), which greatly favors the efficient Se(VI) removal. In addition, surface-bound Fe2+ ions participated in the reduction of Se(VI). Combined with the influence of Se valence as well as pH and Fe2+ (whether dissolved or surface bound), it is deduced that the P-ZVI-O mode induced efficient Se(VI) removal via the adsorption-reduction and/or co-precipitation. This study demonstrates that H2O2/HCl pretreatment of ZVI is a very promising option to enhance the efficiency of reductive removal of Se(VI) from real effluents.

A Bibliometric Analysis of Research on Selenium in Drinking Water during the 1990–2021 Period: Treatment Options for Selenium Removal

“…Enhancing the corrosion of ZVI has been observed as an effective approach to promote its decontamination performance and the role of additional oxidants in this promotion has gained relevance. The addition of chemicals, such as hydrogen peroxide, sodium hypochlorite or potassium permanganate, achieved highly efficient and rapid selenium oxyanion removal [164][165][166]. Moreover, some treatment proposals have taken advantage of the magnetic properties of some ironbased adsorbents to improve the performance of the process by application of magnetic fields [167][168][169].…”

Mechanism of galvanic reduction of selenate oxyanions and surface immobilization by nano zero-valent iron aggregates under anaerobic conditions: towards high electron efficiency

“…19 Galvanic reduction with zero-valent iron (ZVI) 20,21 is another process that has been considered in treating Seladen wastewater or soil decontamination but again this is mostly successful with selenite reduction. 22,23 This system is analogous to the corrosion of iron 20 with the surface of iron comprising anodic (Fe → Fe 2+ + 2e − ) and cathodic sites (Se 4+ + 4e − → Se 0 ) covered by corrosion products (hydrous Fe(II)/ Fe(III) oxides). 24 The limitations of ZVI as a reductant 21 have led to the development of nano zero-valent iron (nZVI) reductants to enhance the reductive reactivity and adsorption capacity via the larger area surface iron oxides and nanosized features.…”