School of Metallurgy and Environment, Central South University, Changsha, 410083, China.
Chinese National Engineering Research Center for Control and Treatment of Heavy Metal Pollution, Changsha, 410083, China.
Environ Geochem Health. 2020 Mar;42(3):769-780. doi: 10.1007/s10653-019-00273-y. Epub 2019 Mar 9.
In recent years, acid rain had a serious negative impact on the leaching behavior of industrial waste residue. Researches were mainly focused on the environmental hazards of heavy metal in the leachate, but ignored the effects of heavy metal speciation on the stability of waste residue in the subsequent stabilization process. In this study, the unstable calcium-arsenic compounds in the arsenic calcium residue were firstly removed by leaching process; subsequently, the crystallization agent was added to treat the remaining calcium-arsenic mixture. The results of the leaching process demonstrated that the decrease in particle size and pH value directly affected the increase in the cumulative leaching amount of arsenic, and the cumulative leaching ratio reached 1.55%. In addition, the concentration of arsenic decreased from 3583 to 49.1 mg L. After the crystallization process, the arsenic concentration was lower than the limit value of Identification Standards for Hazardous Wastes (GB 5085.3-2007). The SEM analysis showed the bulk structures, and XRD pattern confirmed that they were the stable compounds. Moreover, the result of XRD and SEM illustrated that acid concentration, chloride ions and sulfate ions were contributed to the transformation and growth of stable calcium arsenate compounds. Therefore, effective control of the acidity of acid rain, the type of anions in acid rain, and the particle size of residues would contribute to adjusting the arsenic speciation to be more stable. The leaching-crystallization process was of great significance to improve the stability of the arsenic-containing residue.
近年来，酸雨对工业废渣的浸出行为产生了严重的负面影响。研究主要集中在浸出液中重金属的环境危害上，但忽略了重金属形态对后续稳定化过程中废渣稳定性的影响。本研究首先通过浸出过程去除砷钙渣中不稳定的钙砷化合物；然后，添加结晶剂处理剩余的钙砷混合物。浸出过程的结果表明，粒径和 pH 值的降低直接影响砷的累积浸出量的增加，累积浸出率达到 1.55%。此外，砷浓度从 3583 降至 49.1mg/L。结晶过程后，砷浓度低于危险废物鉴别标准（GB 5085.3-2007）。SEM 分析显示了大块结构，XRD 图谱证实了它们是稳定的化合物。此外，XRD 和 SEM 的结果表明，酸浓度、氯离子和硫酸根离子有助于稳定的砷酸钙化合物的转化和生长。因此，有效控制酸雨的酸度、酸雨的阴离子类型和残渣的粒径有助于调整砷的形态以使其更加稳定。浸出-结晶过程对提高含砷残渣的稳定性具有重要意义。
