低分子量有机酸及其共聚物去除土壤重金属研究

为探究低分子有机酸以及其共聚物对土壤中重金属的去除效果,通过振荡淋洗法研究了富马酸和丙烯酸-2-丙烯酰胺基-2-甲基丙磺酸共聚物在不同浓度、pH和时间条件下对土壤中Cd、Pb和Zn的去除率,并采用传统人工螯合剂乙二胺四乙酸做对比。结果表明,土壤中Cd、Pb和Zn的去除率随着有机酸浓度的增加呈现先上升后趋于平稳的趋势。丙烯酸-2-丙烯酰胺基-2-甲基丙磺酸共聚物和富马酸在浓度为10 g·L-1时对Cd、Pb和Zn的去除率分别为54.75%、69.60%、51.42%和42.03%、55.00%、46.97%,乙二胺四乙酸对Cd和Pb的去除率与富马酸趋于一致,但其对Zn的去除率显著低于富马酸(P0.05),仅为34.11%。两种有机酸对重金属去除率受pH的影响较大,其在pH为4~5时能有效去除土壤中Cd、Pb和Zn;富马酸在60 min时达到最大去除率,而丙烯酸-2-丙烯酰胺基-2-甲基丙磺酸共聚物在大于120 min时去除率最高。此外,经过两种有机酸和人工螯合剂乙二胺四乙酸淋洗后,土壤中Cd、Pb和Zn的可交换态和碳酸盐结合态含量大幅度下降。因此,富马酸和丙烯酸-2-丙烯酰胺基-2-甲基丙磺酸共聚物对重金属污染土壤具有潜在修复能力。

Study on the removal of heavy metals in soil by low molecular weight organic acid and organic acid polymer

It is necessary to remove heavy metals from contaminated soils. The effects of fumaric acid(FA)and 2-acrylamido-2-methylpropanesulfonic acid copolymer(AMPS-AA)on the removal of Cd, Pb, and Zn from soils at different concentrations, pH, and time durations were studied by soil washing, and compared with those of ethylenediaminetetraacetic acid(EDTA). The results indicated that the efficiency of Cd, Pb, and Zn removal from the soil increased at first, and then became steady with the increase in the concentrations of organic acid. The Cd, Pb, and Zn removal efficiencies at the leaching concentration of 10 g·L^-1 were 42.03%, 55.00%, and 46.97% respectively for FA, and 54.75%, 69.60%, and 51.42% respectively for AMPS-AA, compared with those of EDTA, which were 45.44%, 38.29%, and 34.11% respectively. The two organic acids can effectively remove Pb, Zn, and Cd in the soil at a pH ranging from 4 to 5, and their removal abilities were greatly affected by the pH. The leaching times of their maximum efficiencies were 60 minutes for FA and over 120 minutes for AMPSAA. In addition, the exchangeable and carbonate bound fractions of Cd, Pb, and Zn in the soil decreased significantly after leaching with the agents. Therefore, FA and AMPS-AA have potential for the remediation of heavy metals in contaminated soils.