Abstract Conventional chemical precipitation methods of salinity removal from mine drainage (MD) are ineffective to deal with sulfate concentrations lower than the solubility of gypsum (CaSO4·2H2O). As the standards of sulfate concentrations become more stringent, this limitation of conventional methods of precipitation drives the need for complementary or alternative solutions. In this context, this study evaluates the efficiency of electrocoagulation (EC) as a stand-alone treatment or as a polishing step following chemical precipitation. The best performance in batch of synthetic MD was obtained at the lowest current density tested of 20 mA/cm2 and at the lowest initial sulfate concentration of 1.3 ± 0.1 g/L. The role of pH was also deemed essential, with acidic pH favouring the coagulation process. Despite EC proving rather inefficient at removing sulfates on its own (in the range of 6 to 31% in 30 min) relative to hydrated lime (Ca(OH)2, 17% removal) and mostly high density sludge (HDS, 45% removal), the combination of EC with the above-mentioned chemical precipitation methods allowed substantial improvement in sulfate removal (up to 35% with Ca(OH)2 and 52% with HDS) much faster (in 30 min instead of 120 min).

中文翻译：

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通过电凝聚从矿井排水中去除硫酸盐作为独立的处理或抛光步骤

摘要 传统的化学沉淀法去除矿井排水（MD）中的盐分，无法处理低于石膏溶解度（CaSO4·2H2O）的硫酸盐浓度。随着硫酸盐浓度标准变得更加严格，传统沉淀方法的这种限制推动了对补充或替代解决方案的需求。在这种情况下，本研究评估了电凝 (EC) 作为独立处理或作为化学沉淀后的抛光步骤的效率。在测试的最低电流密度为 20 mA/cm2 和最低初始硫酸盐浓度为 1.3 ± 0.1 g/L 时，在批次合成 MD 中获得最佳性能。pH 值的作用也被认为是必不可少的，酸性 pH 值有利于凝结过程。