Fe(II)-mediated transformation of schwertmannite associated with calcium from acid mine drainage treatment.
Fe(II)-mediated transformation of schwertmannite associated with calcium from acid mine drainage treatment.
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DOI：
10.1016/j.jes.2022.05.044
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发表时间：
2022-06
影响因子：
6.9
通讯作者：
Cong Fan;C. Guo;Wei Chen;G. Lu;Yueling Shen;Zhi-yuan Dang
中科院分区：
文献类型：
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作者：
Cong Fan;C. Guo;Wei Chen;G. Lu;Yueling Shen;Zhi-yuan Dang
Schwertmannite是酸性矿山水污染地区重要的铁(III)-羟基氧硫酸根，其稳定性取决于周围环境因子和前结合元素。AMD的处理和中和通常涉及石灰的使用，这导致矿区大量钙的排放。这样的环境扰动提出了一个重要而很少被考虑的问题，即与共存的Ca相关的schwertmanite的还原性转化是如何发生的。本文研究了Fe（II）介导的钙吸附schwertmanite的转化和随后的Ca重分配行为。结果表明，吸附的Ca对Fe（II）介导的schwertmanite转化有微弱的抑制作用。SO42−释放和SEM图像均表明，在Ca的影响下，schwertmannite的转化速率降低。XRD图表明，在0.4 mmol/L Fe（II）处理下，Ca的吸附改变了schwertmannite的转化途径和产物组成。Sch的最终产物中明显含有针铁矿和鳞片石；而SchCa的转化产物一直只含针铁矿。注入Fe（II）后6小时内，约33.5%的表面吸附ca被释放到溶液中。在Fe（II）介导的SchCa转化过程中，溶液中的Ca表现出“先释放后固定”的行为，表明溶解和二次矿化驱动了Ca的迁移。吸附的Ca阻断了后续Fe（II）吸附的表面位点，限制了Fe(II)-Fe(III) ETAE，降低了转化速率。这项工作揭示了AMD环境中环境扰动影响下的schwertmanite复杂的地球化学行为。
Schwertmannite is an important Fe(III)-oxyhydroxysulfate in acid mine drainage (AMD) polluted areas and its stability depends on surrounding environmental factors and previously bound elements. The treatment and neutralization of AMD normally involve the use of lime, which leads to the discharge of abundant Ca in the mining area. Such an environmental disturbance brings up an important and less considered problem of how the reductive transformation of schwertmannite associated with coexisting Ca occurred. Here, the Fe(II)-mediated transformation of Ca-adsorbed schwertmannite and subsequent Ca repartitioning behaviors were investigated. Results showed that adsorbed Ca had a weak inhibitory effect on Fe(II)-mediated schwertmannite transformation. Release of SO42−and SEM images both indicated that transformation rates of schwertmannite decreased under the influence of adsorbed Ca. XRD patterns indicated that adsorbed Ca altered schwertmannite transformation pathways and product compositions upon treatment with 0.4 mmol/L Fe(II). The end products of Sch notably contained both goethite and lepidocrocite; however, transformation products of SchCa only contained goethite all along. Approximately 33.5% of the surface adsorbed-Ca was released into solution within 6 hr after Fe(II) injection. Aqueous Ca behaved in a “first release and then im-mobilization” manner, which indicated dissolution and secondary mineralization drove Ca migration during the Fe(II)-mediated transformation of SchCa. Adsorbed Ca blocked the surface sites for subsequent Fe(II) adsorption, limited the Fe(II)-Fe(III) ETAE, and decreased the transformation rates. This work sheds light on the complex geochemical behavior of schwertmannite under the influences of environmental perturbations in AMD environments.