Arsenic is one of the most hazardous pollutants released by the mining industry. Processes such as ore concentration and smelting produce high volumes of arsenic-rich wastewater, and several methods have been proposed to treat this arsenical wastewater. Arsenic precipitation using ferric ions yields compounds such as scorodite, a kind of ferric arsenate, while similar compounds can also be produced by iron-oxidizing microorganisms. However, both cases require high temperatures, potentially leading to significant economic costs when industrial applications are conceived. Then, arsenic removal with mesophilic iron-oxidizing microorganisms would greatly benefit from a decrease in operational temperature. Hence, this work aims to evaluate the biological removal of arsenic in wastewater, using a consortium of mesophilic (35 °C) iron-oxidizing microorganisms adapted to As (III). Our results indicate that arsenic speciation is a key factor for microbiologically assisted arsenic removal efficiency. Indeed, a maximum of 25 % or 91 % of arsenic was removed using As (III) or As (V), respectively. The effect of iron concentration was also evaluated, and the results showed that increasing iron concentration led to an increase in arsenic removal. Chemical controls removed more arsenic than inoculated assays when Fe:As molar ratios 1.0, 1.5, and 2.0 were used. Interestingly, inoculated tests achieved the best arsenic removal within a shorter timeframe (48 h) when a high Fe:As molar ratio (3.5) was used. This highlights the advantage of using a biological approach for arsenic removal under mesophilic conditions. In assays performed with smelting wastewater from a Chilean copper smelter, inoculated tests achieved 66 % arsenic removal when compared to 7 % obtained in chemical control. Energy dispersive X-ray spectroscopy analysis confirmed the presence of arsenic and iron in the solid residues, with no other metals detected. This finding opens the possibility of sustainable secondary copper recovery by reprocessing rich-arsenic smelting wastewater.

中文翻译：

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利用中温财团去除铜冶炼废水中的砷


砷是采矿业释放的最危险的污染物之一。选矿和冶炼等过程会产生大量富砷废水，人们提出了几种处理这种含砷废水的方法。使用铁离子沉淀砷会产生臭葱石（一种砷酸铁）等化合物，而铁氧化微生物也可以产生类似的化合物。然而，这两种情况都需要高温，在考虑工业应用时可能会导致巨大的经济成本。然后，使用中温铁氧化微生物去除砷将大大受益于操作温度的降低。因此，这项工作旨在使用适应 As (III) 的嗜温 (35 °C) 铁氧化微生物群来评估废水中砷的生物去除。我们的结果表明砷形态是微生物辅助除砷效率的关键因素。事实上，使用 As (III) 或 As (V) 分别最多可去除 25% 或 91% 的砷。还评估了铁浓度的影响，结果表明铁浓度的增加导致砷去除率的增加。当使用 Fe:As 摩尔比 1.0、1.5 和 2.0 时，化学对照比接种测定去除更多的砷。有趣的是，当使用高 Fe:As 摩尔比 (3.5) 时，接种试验在较短的时间范围内（48 小时）实现了最佳的砷去除效果。这凸显了在中温条件下使用生物方法去除砷的优势。在对智利铜冶炼厂的冶炼废水进行的分析中，接种测试实现了 66% 的砷去除率，而化学控制中的砷去除率为 7%。 能量色散 X 射线光谱分析证实固体残留物中存在砷和铁，未检测到其他金属。这一发现开启了通过再处理富砷冶炼废水可持续二次回收铜的可能性。