Microbial reduction of arsenic (As)-bearing Fe(III)-(oxyhydr)oxides is one of the major processes for the release of As in various environmental settings such as acid mine drainage, groundwater, and flooded paddy soil. Pyrogenic carbon has recently been reported to facilitate microbial extracellular reduction of Fe(III)-(oxyhydr)oxides. The aim of this study was to investigate the important hot topic regarding the fate and transformation of As during activated carbon (AC) facilitated microbial reduction of As-bearing ferrihydrite. Our results show that the rate and extent of Fe(III) reduction in As-bearing ferrihydrite by Shewanella oneidensis MR-1 were accelerated by AC. The AC facilitated reduction caused the release of As(III) into the solution, whereas it caused the preferential immobilization of As(V) on the solid phase. Furthermore, AC accelerated the precipitation of vivianite and siderite in sequence during microbial reduction processes. Both of the formed vivianite and siderite had an insignificant capacity for capturing As(III); however, As(V) was selectively immobilized by vivianite compared to that of siderite. Taken together, our findings provide crucial insights into understanding the role of AC on the redox and immobilization of Fe and As in suboxic and anoxic environments and thus their environmental fate when pyrogenic carbons are employed for agronomic and environmental applications.

中文翻译：

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活性炭促进含砷水铁矿微生物还原过程中As（III）和As（V）的命运

含砷（As）的Fe（III）-（羟基）氧化物的微生物还原是在酸性环境下的排水，地下水和水淹水稻田等各种环境条件下释放As的主要过程之一。最近有报道说热解碳有助于微生物胞外还原Fe（III）-（oxyhydroxy）oxides。这项研究的目的是调查有关活性炭（AC）促进含砷水铁矿微生物还原过程中As的命运和转变的重要热点话题。我们的结果表明，沙瓦氏菌（Shewanella oneidensis）还原含砷水铁矿中Fe（III）的速率和程度交流电加速了MR-1。AC促进的还原导致As（III）释放到溶液中，而它却导致As（V）优先固定在固相上。此外，在微生物还原过程中，AC依次促进了堇青石和菱铁矿的沉淀。生成的堇青石和菱铁矿均具有微不足道的捕获As（III）的能力。然而，与菱铁矿相比，Vivianite选择性地固定了As（V）。综上所述，我们的发现为理解AC在低氧和缺氧环境中对AC和Fe和As的氧化还原和固定化所起的作用提供了重要的见解，因此，当将热解碳用于农业和环境应用时，它们的环境命运也至关重要。