Roles of natural iron oxides in the promoted sequestration of chromate using calcium polysulfide: pH effect and mechanisms
Roles of natural iron oxides in the promoted sequestration of chromate using calcium polysulfide: pH effect and mechanisms
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天然铁氧化物在多硫化钙促进铬酸盐螯合中的作用：pH 效应和机制
DOI：
10.1016/j.seppur.2019.116350
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发表时间：
2020
影响因子：
8.6
通讯作者：
Liu Bin
中科院分区：
文献类型：
--
作者：
Wang Tao;Wang Wanyu;Liu Yuanyuan;Li Wei;Li Yunyi;Liu Bin
多硫化钙(CPS)已被广泛用于修复六价铬(Cr(VI))污染的环境，但天然铁氧化物在铬(VI)固定过程中的作用尚不清楚。在这项研究中，我们研究了天然铁氧化物对使用CPS修复含铬(VI)环境的影响及其机制。针铁矿和赤铁矿显著促进了CPS对铬(VI)的吸附，但在pH为7.0时，铬(VI)的去除效率和表观速率常数均增加。在pH值为7.0时，针铁矿对铬(VI)的去除效率从80.6%提高到98.6%，表观速率常数从0.0074增加到0.028 L·−·1min·−~(-1)。同样，赤铁矿使CP对铬(VI)的去除效率提高到98.4%，表观速率常数增加到0.024 L·mol·−·1min·−~(-1)。pH对针铁矿和赤铁矿在酸性条件下对铬(VI)的去除效率影响不大，而在碱性条件下对铬(VI)的去除效率有显著影响。此外，pH对CPS与针铁矿或赤铁矿促进铬(VI)的吸附过程有显著影响。在酸性pH条件下，针铁矿和赤铁矿对铬(VI)的吸收增加主要是由于针铁矿和赤铁矿对铬(VI)的吸附，同时伴随着↔反应的针铁矿和赤铁矿的Fe(III)-O-Fe(II)和Fe(II)表面沟道中的电子对Cr(VI)的少量还原。在中性和碱性pH条件下，针铁矿和赤铁矿表面多硫化物活化的Fe(III)充当了多硫化物与铬(VI)之间的桥梁，加速了多硫化物向铬(VI)的电子穿梭，而铬(VI)与FeS2和含Fe(II)-S键的化合物的反应则促进了铬(VI)的还原。我们的研究表明，在富含铁氧化物的铬(VI)污染环境的修复过程中，天然铁矿物可以通过CPS加强对铬(VI)的固定。
Calcium polysulfide (CPS) has been widely used for the remediation of hexavalent chromium (Cr(VI))-contaminated environments; however, the roles of natural iron oxides during the process of Cr(VI) sequestration are not well understood. In this study, we investigated the impact of natural iron oxides on the remediation of environments containing Cr(VI) using CPS and the mechanisms underlying such effects. Goethite and hematite markedly accelerated Cr(VI) sequestration by CPS, while Cr(VI) removal efficiency and apparent rate constant were increased at pH 7.0. Goethite increased the Cr(VI) removal efficiency of CPS from 80.6% to 98.6% at pH 7.0, while the apparent rate constant increased from 0.0074 to 0.028 L mol−1min−1. Similarly, hematite increased the Cr(VI) removal efficiency of CPS to 98.4%, while the apparent rate constant increased to 0.024 L mol−1min−1. pH had a negligible impact on the efficiency of Cr(VI) uptake by CPS with goethite or hematite under acidic conditions, whereas a pronounced effect on Cr(VI) removal efficiency was shown under basic conditions. Moreover, pH could significantly influence processes of promoted Cr(VI) sequestration using CPS with goethite or hematite. At acidic pH, increased Cr(VI) uptake was attributed mainly to the adsorption of Cr(VI) on goethite and hematite, which was accompanied by minor Cr(VI) reduction by electrons from the surface channel of >Fe(III)-O-Fe(II) ↔ >Fe(II)-O-Fe(III) and Fe(II) from CPS-reacted goethite and hematite. At neutral and basic pH, polysulfide-activated Fe(III) on the surface of goethite and hematite acted as a bridge between CPS and Cr(VI), which accelerated electron shuttling from polysulfides to Cr(VI), while Cr(VI) reduction was enhanced by the reactions of Cr(VI) with FeS2and compounds containing Fe(II)-S bonds. Our study demonstrates that natural iron minerals can enhance Cr(VI) sequestration using CPS during the remediation of Cr(VI)-contaminated environments rich in iron oxides.