Abstract Lime dosing in a high-density sludge (LD-HDS) process is amongst the most widely applied acid mine drainage (AMD) treatment processes worldwide. It is effective and reliable, however, an intrinsic issue for metalliferous mining derived AMD is the formation of an ecotoxic metal(loid)-bearing (e.g. As, Pb, Ni, Cd and Sb) ochre waste product. Herein the efficacy and selectivity of AMD (pH 3.5; 1–500 g/L), citric and oxalic acid (0.01–1 M) for ecotoxic metal(loid) dissolution from such ochre has been investigated. When AMD is applied at a low solid-liquid ratio (namely 1 g/L) or citric and oxalic acids are at low concentrations (namely ≤0.1 M) such lixiviants are selective for certain ecotoxic metals which have been designated by BCR 4-step sequential extraction as “exchangeable” (namely: Sb, Cd, Cu and Ni) in preference to Fe. This suggests that they could potentially be integrated into the LD-HDS process in order to lower the ecotoxicity of the final ochre product and thereby valorise it for use in a wide range of commercial applications. Conversely when AMD is applied at a higher solid-liquid ratio (namely ≥100 g/L) ecotoxic metal precipitation occurred (due to the alkaline pH of the ochre). This suggests that the ochre could also be reused for AMD remediation.

中文翻译：

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使用酸性矿山排水和有机酸从石灰投加厂含金属赭石中选择性浸出生态毒性金属

摘要 高密度污泥 (LD-HDS) 工艺中的石灰投加是全球应用最广泛的酸性矿山排水 (AMD) 处理工艺之一。它是有效和可靠的，但是，金属采矿衍生的 AMD 的一个内在问题是形成具有生态毒性的金属（类）轴承（例如 As、Pb、Ni、Cd 和 Sb）赭石废品。本文研究了 AMD（pH 3.5；1–500 g/L）、柠檬酸和草酸（0.01–1 M）从这种赭石中溶解生态毒性金属（液）的功效和选择性。当 AMD 以低固液比（即 1 g/L）或柠檬酸和草酸处于低浓度（即 ≤ 0.1 M）时，此类浸出剂对 BCR 4 步指定的某些生态毒性金属具有选择性顺序提取作为“可交换”（即：Sb、Cd、Cu 和 Ni）优先于 Fe。这表明它们有可能被整合到 LD-HDS 工艺中，以降低赭石最终产品的生态毒性，从而使其在广泛的商业应用中发挥作用。相反，当 AMD 以更高的固液比（即≥100 g/L）应用时，会发生生态毒性金属沉淀（由于赭石的碱性 pH 值）。这表明赭石也可以重新用于 AMD 修复。