School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Electric Power Research Institute, Charlotte, NC 28213, USA.
J Hazard Mater. 2019 Jul 5;373:572-579. doi: 10.1016/j.jhazmat.2019.03.117. Epub 2019 Mar 27.
To achieve zero liquid discharge, the flue-gas-desulfurization (FGD) wastewater at coal-fired power plants can be concentrated into brine through thermal evaporation to maximize water reuse; however, the hot brine generated requires further treatment prior to disposal. To address this need, this study investigates the performance of aged, micron-sized zero-valent iron (ZVI) for heavy metal removal in simulated and real FGD hot brines, which was scarcely studied previously. The effects of temperature, pH, total dissolved solids, ZVI dosage, major cations, nitrate and sulfate on the reactivity of ZVI in the brines were evaluated. Among many factors, higher temperature and Mg exert the dominant influence. At 80 °C, almost 100% of arsenate (1 mg/L) and chromate (1 mg/L) can be removed in <5 min using 4.17 g/L of ZVI in simulated brines, while selenate (25 mg/L) and cadmium (5 mg/L) can be completely removed within 30 min. Mg ions naturally present in FGD brines account for the depassivation of aged ZVI. X-ray diffraction results suggest that green rust is the reactive intermediate for selenate and cadmium removal. Overall, this study demonstrates that ZVI is an effective material for removing heavy metals in hot FGD brines generated through thermal evaporation at power plants.
为实现零液体排放，燃煤电厂的烟气脱硫 (FGD) 废水可以通过热蒸发浓缩成卤水，以实现最大程度的水再利用；然而，产生的热卤水在处置前需要进一步处理。针对这一需求，本研究考察了老化的微米级零价铁 (ZVI) 在模拟和实际 FGD 热卤水中去除重金属的性能，这在以前很少研究过。评估了温度、pH 值、总溶解固体、ZVI 剂量、主要阳离子、硝酸盐和硫酸盐对卤水中 ZVI 反应性的影响。在许多因素中，较高的温度和镁产生主导影响。在 80°C 下，使用 4.17 g/L 的 ZVI 在模拟卤水中可在 <5 min 内去除 1 mg/L 的砷酸盐（1 mg/L）和铬酸盐（1 mg/L），而硒酸盐（25 mg/L）和镉（5 mg/L）可在 30 min 内完全去除。FGD 卤水中天然存在的镁离子导致老化 ZVI 的去钝化。X 射线衍射结果表明，绿色锈是硒酸盐和镉去除的反应中间体。总体而言，本研究表明 ZVI 是一种有效去除电厂热蒸发产生的热 FGD 卤水中重金属的材料。
