复合稳定剂对砷污染土壤的稳定研究

重金属污染土壤均含有多种元素,使用一种药剂对土壤进行稳定的效果不佳且处理费用较高.本研究采集富含砷(As)、镉(Cd)、锌(Zn)的重金属污染土壤,选用无机和有机稳定剂对土壤进行快速化学稳定化实验研究,利用酸浸提程序(TCLP法)评价土壤中重金属的浸出毒性,结果表明,含钙物质、含硫物质以及含铁物质对于降低金属流动性非常有效,6种试剂中稳定效率排序为:氧化钙>硫化钠>有机硫>壳聚糖>硫酸亚铁>二乙基二硫代氨基甲酸钠.根据不同试剂稳定重金属的靶向特性对两种类型稳定剂进行组合,对复合稳定剂的稳定效果进行评价,分析结果显示复配试剂的综合稳定效率更高:铁钙复配(3%硫酸亚铁+5%氧化钙)对土壤中3种金属的稳定率为81.7%、97.2%、68.2%,而有机硫氧化钙复配试剂(3%氧化钙+5%有机硫)对3种金属的稳定率达到76.6%、95.7%、93.8%.重金属形态测试的结果认为重金属从可交换态转变为还原态(无机类试剂)或氧化态(有机类试剂)是重金属稳定的主要原因,且形态转变程度决定了土壤的稳定程度.

Study on Composite Stabilization of Arsenic (As) Contaminated Soil

Since the contaminated soil may contain various kinds of heavy metals, use of single chemical reagent leads to poor remediation and high cost. In this study, soil containing As, Zn, Cd was sampled, and different reagents were selected to carry out the rapid stabilization of contaminated soil. The TCLP (toxicity characteristic leaching procedure) was used to evaluate the leachate toxicity of heavy metals and the results indicated that calcium-containing, sulphur-containing and iron-containing reagents had good performance in reducing the metal mobility. The stabilization efficiency of the six reagents tested ranked in the order of CaO>Na₂S>organic sulfur>Chitosan>FeSO₄>(C₂H₅)₂NCS₂Na. Two types of reagents (six reagents) were combined based on the target properties of different reagents and the stabilization efficiency was evaluated and analyzed. The results indicated that the composite reagents had higher stabilization efficiency: the efficiency of 3%FeSO₄+5%CaO was 81.7%,97.2% and 68.2% for As, Cd and Zn, respectively, and the efficiency of 3%CaO+5%organic sulfur was 76.6%, 95.7% and 93.8% for these three metals, respectively. Speciation analysis was carried out in this study and the results suggested that it was the change of metals from the exchangeable state to the reduction (for inorganic reagent) or oxidation state (for organic reagent) that caused the soil stabilization and the degree of change determined the stabilization efficiency.