Abstract Scorodite waste during its short-term storage in an iron environment has proved to pose an arsenic pollution risk. However, the long-term stability of scorodite is not completely understood. This work investigated the effect of iron reduction by enolic hydroxyl groups as reductive natural organic matter on long-term stability of scorodite. The results showed that 38.3% and 31.3% of As was released into the aqueous phase after 99.4% and 82.6% of Fe(III) was reduced to Fe(II) at pH 6 and 7 for 134 days, respectively. Compared with the observations regarding 3-day reactions in our previous work, arsenic was further dissolved and the degree of Fe(III) reduction increased over time. In contrast, the release of Fe(II) at pH 6 and 7 exhibited a descending trend from the 240th h, with the percentage of aqueous Fe(II) falling to 9.1% and 5.6%, respectively. Most of Fe(II) and As(V) were immobilized by solids. Crystalline parasymplesite as the only secondary solid was responsible for the fixation of arsenic. Chemical analysis together with solid characterization indicated that the transformation of the secondary solid involved the conversion of FeHAsO4 (Fe/As molar ratio of 1) to Fe3(AsO4)2·8H2O (Fe/As molar ratio of 1.5), causing more As release. Scorodite, therefore, was unstable during its long-term storage in an Fe-reducing environment at (slightly) circum-neutral pH.

中文翻译：

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铁还原对臭葱石在烯醇羟基和矿物转化中长期稳定性的影响

摘要 臭葱石废物在铁环境中短期储存期间已被证明会造成砷污染风险。然而，臭葱石的长期稳定性尚不完全清楚。这项工作研究了烯醇羟基作为还原性天然有机物对铁的还原对臭葱石长期稳定性的影响。结果表明，在 pH 6 和 7 条件下，分别将 99.4% 和 82.6% 的 Fe(III) 还原为 Fe(II) 134 天后，38.3% 和 31.3% 的 As 释放到水相中。与我们之前工作中关于 3 天反应的观察结果相比，砷进一步溶解并且 Fe(III) 的还原程度随着时间的推移而增加。相比之下，pH 6 和 7 时 Fe(II) 的释放从第 240 小时开始呈下降趋势，Fe(II) 水溶液的百分比下降到 9.1% 和 5.6%，分别。大多数 Fe(II) 和 As(V) 被固体固定。作为唯一的次要固体的结晶副共轭铁负责砷的固定。化学分析和固体表征表明，二次固体的转变涉及 FeHAsO4（Fe/As 摩尔比为 1）向 Fe3(AsO4)2·8H2O（Fe/As 摩尔比为 1.5）的转化，导致更多的 As 释放. 因此，臭葱石在其在（略微）周围中性 pH 值的 Fe 还原环境中长期储存期间是不稳定的。化学分析和固体表征表明，二次固体的转变涉及 FeHAsO4（Fe/As 摩尔比为 1）向 Fe3(AsO4)2·8H2O（Fe/As 摩尔比为 1.5）的转化，导致更多的 As 释放. 因此，臭葱石在其在（略微）周围中性 pH 值的 Fe 还原环境中长期储存期间是不稳定的。化学分析和固体表征表明，二次固体的转变涉及 FeHAsO4（Fe/As 摩尔比为 1）向 Fe3(AsO4)2·8H2O（Fe/As 摩尔比为 1.5）的转化，导致更多的 As 释放. 因此，臭葱石在其在（略微）周围中性 pH 值的 Fe 还原环境中长期储存期间是不稳定的。