State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, China.
State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, China.
Chemosphere. 2018 Dec;213:172-181. doi: 10.1016/j.chemosphere.2018.08.143. Epub 2018 Sep 8.
Remediation of high concentrations of Cr(VI) in wastewater involves its chemical reduction to Cr(III), a product with low toxicity that can be easily removed. To date, NaBH has rarely been used to reduce Cr(VI). This article reports a comparative study of Cr(VI) removal by NaBH and five sulfur-based reducing agents (FeSO, NaSO, NaHSO, NaSO, and NaSO). The potential mechanisms of Cr(VI) removal by these six reducing agents with and without fly ash leachate (FAL) are also discussed. The results revealed that the reduction and subsequent removal of Cr(VI) are influenced by the hydrolysis and ionization of the reducing agents in solution. Thus, the reduction reaction was significantly enhanced when NaSO and NaHSO were added in excess of 600 mg L. Combined with FAL, smaller amounts of NaBH were required to reduce Cr(VI) to Cr(III) at pH 3.0 compared to those with the other reducing agents. NaBH combined with FAL at a dose of 100 mg L afforded a total Cr (Cr) removal of 96.32% within 20 min, a value much higher than that obtained with the other reducing agents. The catalytic mechanism of NaBH for such a FAL-catalyzed Cr(VI) reduction system is similar to that of acid catalysis via the hydrolysis of the Fe(III) and Al(III) species in FAL. Improvement of the Cr removal was also observed via Cr(VI) entrapment in the structure of Fe(III) and Al(III) metal hydroxides. These results indicate that relatively low loadings of NaBH combined with FAL show great promise for Cr(VI) pollution remediation.
废水高浓度六价铬的修复涉及将其化学还原为三价铬，三价铬毒性低，易于去除。迄今为止，硼氢化钠很少用于还原六价铬。本文报道了硼氢化钠与五种含硫还原剂（硫酸亚铁、亚硫酸钠、亚硫酸氢钠、硫代硫酸钠和连二亚硫酸钠）去除六价铬的对比研究。还讨论了这六种还原剂在有和没有粉煤灰浸出液（FAL）时去除六价铬的潜在机制。结果表明，还原和随后的六价铬去除受到溶液中还原剂水解和电离的影响。因此，当过量添加 600mg/L 的亚硫酸钠和亚硫酸氢钠时，还原反应显著增强。与其他还原剂相比，在 pH 3.0 时，将硼氢化钠与 FAL 结合使用，仅需较少的量即可将六价铬还原为三价铬。在 100mg/L 的剂量下，硼氢化钠与 FAL 结合在 20min 内可实现总铬（Cr）去除率 96.32%，远高于其他还原剂。硼氢化钠与 FAL 协同作用的催化机制类似于 FAL 中水解铁（III）和铝（III）物种的酸催化机制。还观察到通过六价铬在铁（III）和铝（III）金属氢氧化物结构中的捕获来改善铬的去除。这些结果表明，相对低负载的硼氢化钠与 FAL 结合在六价铬污染修复方面具有很大的应用前景。
