Abstract The mineral schwertmannite forms in acidic sulfate-rich environments (pH 2.9–4) and has a large sorption potential for oxyanions. In this study we tested the properties of granulated schwertmannite produced from material obtained from a mine water treatment plant to remove SeO32−, SeO42−, MoO42−, PO43−, and Sb(OH)6−. We studied the kinetics of sulfate release from the granulated schwertmannite in suspensions containing various concentrations of HCO3− and its effect on the sorption kinetics of the oxyanions in synthetic solutions and industrial wastewater through batch experiment at acidic and neutral pH. We further tested the suitability of the granulated schwertmannite adsorbents as filter bed materials to remove SeO32−, MoO42−, and PO43− from synthetic solution via column experiments. Using a two-step pseudo-first order model, we were able to distinguish between an initial fast sorption process and a second slow reaction with characteristic reaction times (1/k) of ~10 min and ~ 10 h, respectively. Ligand exchange with surface bound sulfate is proposed to be responsible for the fast reaction while intraparticle diffusion and exchange with structural sulfate control the slow process. At neutral pH values, sulfate release is complete within one week, suggesting partial transformation of schwertmannite into a new ferric oxyhydroxide phase. The sorption kinetics were reflected in the results from the column experiments where only the fast sorbing fraction of surface sites participated in the retention of oxyanions at a mean residence times τ of 8 min with retention capacities of 149 μmol ∙ (g SHM)−1 for SeO32− and 242 μmol ∙ (g SHM)−1 for MoO42−. Hydraulic residence time increased the retention of PO43− with 213 μmol ∙ (g SHM)−1 at τ = 4.75 min and 508 μmol ∙ (g SHM)−1 at τ = 47.5 min. In summary, granulated schwertmannite turned out to be a promising adsorbent to remove the tested oxyanions from contaminated waters. Our results demonstrated that its application in filter bed systems needs to consider the trade-off between residence time and sorption kinetics. An increase in residence time clearly increases the retention capacity.

中文翻译：

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颗粒状施威曼石吸附剂从污染水中去除氧阴离子（SeO32-、SeO42-、MoO42-、PO43-、Sb(OH)6-）的潜力

摘要 矿物施维特曼石在富含硫酸盐的酸性环境 (pH 2.9-4) 中形成，对氧阴离子具有很大的吸附潜力。在这项研究中，我们测试了从矿井水处理厂获得的材料生产的颗粒状施维特曼石的特性，以去除 SeO32-、SeO42-、MoO42-、PO43- 和 Sb(OH)6-。我们通过在酸性和中性 pH 值下的批量实验研究了硫酸盐从含有不同浓度 HCO3− 的悬浮液中的颗粒状施威曼石释放的动力学及其对合成溶液和工业废水中氧阴离子吸附动力学的影响。我们通过柱实验进一步测试了粒状施维特曼吸附剂作为过滤床材料从合成溶液中去除 SeO32-、MoO42- 和 PO43- 的适用性。使用两步伪一阶模型，我们能够区分初始快速吸附过程和第二个缓慢反应，特征反应时间 (1/k) 分别为~10 分钟和~10 小时。建议与表面结合硫酸盐的配体交换负责快速反应，而颗粒内扩散和与结构硫酸盐的交换控制缓慢的过程。在中性 pH 值下，硫酸盐释放在一周内完成，表明施维特曼石部分转化为新的羟基氧化铁相。吸附动力学反映在柱实验的结果中，其中只有表面位点的快速吸附部分参与了氧阴离子的保留，平均停留时间 τ 为 8 分钟，保留容量为 149 μmol ∙ (g SHM)-1 SeO32− 和 MoO42− 的 242 μmol ∙ (g SHM)−1。水力停留时间增加了 PO43− 的保留，τ = 4.75 分钟时为 213 μmol ∙ (g SHM)-1，τ = 47.5 分钟时为 508 μmol ∙ (g SHM)-1。总之，颗粒状施维特曼石是一种很有前途的吸附剂，可以从受污染的水中去除所测试的氧阴离子。我们的结果表明，它在滤床系统中的应用需要考虑停留时间和吸附动力学之间的权衡。停留时间的增加明显增加了保留能力。我们的结果表明，它在滤床系统中的应用需要考虑停留时间和吸附动力学之间的权衡。停留时间的增加明显增加了保留能力。我们的结果表明，它在滤床系统中的应用需要考虑停留时间和吸附动力学之间的权衡。停留时间的增加明显增加了保留能力。