Dissolution of realgar by Acidithiobacillus ferrooxidans in the presence and absence of zerovalent iron: Implications for remediation of iron-deficient realgar tailings. (October 2018)

• Record Type: Journal Article
• Authors: Fan, Lijun; Zhao, Fenghua; Liu, Jing; Hudson-Edwards, Karen A.
• Is Part Of: Chemosphere. Volume 209(2018)
• Page Start: 381
• Page End: 391
• Publication Date: 2018-10
• Subjects: Realgar -- ZVI -- A. ferrooxidans -- Dissolution -- Arsenic; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2018.05.192
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Realgar (As4 S4 )-rich tailings are iron-deficient arsenical mine wastes. The mechanisms and products of the dissolution of realgar by Acidithiobacillus ferrooxidans ( A. ferrooxidans ) in the presence (0.2 g and 2 g) and absence of zerovalent iron (ZVI) are investigated for three stages (each of 7 d with fresh A. ferrooxidans medium addition between the stages). SEM-EDX, FTIR, XPS and selective extraction analysis are used to characterize the solid-phase during the experiments. ZVI addition causes the systems to become more acid-generating, although pH increases are observed in the first day due to ZVI dissolution. Arsenic is released to solution due to realgar oxidation (∼30 mg L −1 in the 0 g ZVI system in Stage I), but low concentrations are observed in the ZVI-added systems (<5 mg L −1 ) and in Stages II and III of the 0 g ZVI system. As(III) dominates the released As(T) at day 1 (83–89% of As(T)), but is largely oxidized to As(V) at day 7 of each stage (53–98% of As(T)). Arsenic attenuation is attributed to the formation of mixed As-Fe oxyhydroxides and oxyhydroxy sulfates that take up released arsenic and are abundant in the 2.0 g ZVI system, and to passivation of the realgar surface. Consequently, a new strategy that combines A. ferrooxidans and exogenous ZVI addition for treating in-situ iron-deficient realgar-rich tailings is proposed, although its long-term effects need to be monitored. Highlights: Realgar dissolution by A. ferrooxidans with and without zerovalent iron studied. Arsenic released to solution due to realgar oxidation. Low aqueous arsenic observed in ZVI-added systems. Arsenic attenuation due to formation of As-bearing Fe oxyhydr-oxides and –sulfates. Zerovalent iron and A. ferrooxidans could be used to remediate realgar tailings.