FeCl_(3)淋洗修复Pb-Ni复合污染土壤机制研究

Study on the mechanism of FeCl_(3) leaching remediation for Pb-Ni composite polluted soil

Pb、Ni复合污染对土壤的危害大,协同修复难度高。本文以修复建设用地为目标,模拟配制了不同污染程度的Pb、Ni复合污染土壤,以FeCl_(3)为淋洗剂,考察淋洗时间、淋洗剂浓度和液固比等关键参数对Pb、Ni复合污染土壤的影响及其修复机制。结果表明:当FeCl_(3)浓度为0.6 mol/L,液固比为5∶1、淋洗时间为10 h时,Pb、Ni的淋洗效果最好,Pb低、中、高污染土壤的淋洗率分别为80.75%、89.32%和91.45%,Ni低、中、高污染土壤的淋洗率分别为77.31%、92.01%和96.29%;FeCl_(3)对Pb和Ni的快速反应阶段在0~4 h时间段内,至12 h时基本达到平衡。采用双常数和Elovich模型拟合淋洗动力学过程发现,FeCl_(3)对Pb和Ni的淋洗主要是非均相扩散过程;FeCl_(3)对Pb和Ni不同污染程度土壤的去除效果排序为高污染>中污染>低污染,对重金属的去除能力排序为Ni>Pb,FeCl_(3)可有效去除Pb和Ni的弱酸可溶态和可还原态。经FeCl_(3)淋洗后的土壤中Pb和Ni含量均低于第一类建设用地的管制值,对人体健康危害小。

The combined pollution of Pb and Ni has great harm to the soil and the difficulty of synergistic remediation is high.In this paper,with the goal of repairing construction land,Pb and Ni combined polluted soil with different pollution levels was simulated and prepared.FeCl_(3) was used as the eluent to investigate the effects of key parameters such as leaching time,eluent concentration and liquid-solid ratio on Pb and Ni combined polluted soil and its remediation mechanism.The results show that when the FeCl_(3) concentration is 0.6 mol/L,the liquid-solid ratio is 5∶1,and the leaching time is 10 h,the leaching effect of Pb and Ni is the best.The leaching rates of Pb low,medium and high contaminated soils are 80.75%,89.32% and 91.45%,respectively,and the leaching rates of Ni low,medium and high contaminated soils are 77.31%,92.01% and 96.29%,respectively.The rapid reaction stage of FeCl_(3) on Pb and Ni occurs within the time period of 0~4 h,and and basically reaches equilibrium by 12 h.It was found that the leaching kinetics of Pb and Ni by FeCl_(3) is mainly a heterogeneous diffusion process,as fitted by the double constant and Elovich models.The removal efficiency of Pb and Ni in soils with different pollution levels by FeCl_(3) is ranked as high pollution>medium pollution>low pollution,and the removal capacity of heavy metals is ranked as Ni>Pb.FeCl_(3) can effectively remove the weak acid soluble and reducible states of Pb and Ni.The contents of Pb and Ni in the soil after FeCl_(3) leaching are lower than the control values of the first type of construction land,which is less harmful to human health.