In recent years, one of the more effective developments in the fixation of arsenic from waste has been the synthesis of scorodite via the co-precipitation of arsenic with iron during Fe(II) oxidation. This work examines the impact of cation impurities on the process with the aim of widening the application of this approach to incorporate the use of seawater and the treatment of metallurgy waste. Scorodite formation was promoted by the presence of cations in the order of Cu >> Zn > Al > Ca ∼ Mg, with differences in precipitation behaviour, yield and kinetics due to specific cation effects on iron oxidation. A grain size increase was observed with Cu, while the opposite was found with Al, attributed to crystallisation from solution over epitaxial growth. The use of seawater decreased As precipitation by <4 % without affecting grain size, showing the potential to be utilised as reaction medium. While the presence of Na hinders As precipitation, the impact appears less pronounced with seawater due to competing effects from other cations. Since scorodite precipitation is slowed down by high Fe(III) in the feed, a pre-reduction approach with Al, Cu and Zn base metals was examined for conversion of Fe(III) in metallurgical waste to Fe(II) prior to co-precipitation with As. While this produced stable scorodite precipitates, the yield and presence of unstable by-products were impacted by the method of reductant addition.

中文翻译：

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海水和溶解阳离子对铁共沉淀合成臭葱石的影响


近年来，从废物中固定砷的更有效的进展之一是通过 Fe(II) 氧化过程中砷与铁的共沉淀来合成臭葱石。这项工作研究了阳离子杂质对该过程的影响，旨在扩大该方法的应用范围，将海水的使用和冶金废物的处理结合起来。阳离子的存在促进了臭葱石的形成，其顺序为 Cu >> Zn > Al > Ca ∼ Mg，由于特定的阳离子对铁氧化的影响，沉淀行为、产率和动力学存在差异。 Cu 观察到晶粒尺寸增大，而 Al 则相反，这归因于外延生长过程中从溶液中结晶。海水的使用随着降水量减少 <4%，但不影响颗粒尺寸，显示出用作反应介质的潜力。虽然钠的存在阻碍了砷的沉淀，但由于其他阳离子的竞争作用，这种影响在海水中似乎不太明显。由于进料中的高 Fe(III) 会减缓臭葱石的沉淀，因此研究了使用 Al、Cu 和 Zn 贱金属的预还原方法，以在共还原之前将冶金废物中的 Fe(III) 转化为 Fe(II)。与As沉淀。虽然这产生了稳定的臭葱石沉淀物，但不稳定副产物的产率和存在受到还原剂添加方法的影响。