草酸-FeCl3复合淋洗剂对Pb、Zn污染土壤淋洗效果研究

采用草酸-FeCl_3复合淋洗剂对土壤中严重超标的Pb和Zn进行振荡淋洗试验,并研究了淋洗剂浓度、液土比、淋洗时间、淋洗次数等因素对重金属去除效率的影响,采用BCR形态分级法分析淋洗前后重金属形态的变化。结果表明,淋洗剂对土壤中Pb、Zn的去除效果从大到小依次为草酸-FeCl_3复合、FeCl_3、草酸。草酸-FeCl_3复合淋洗剂的最适淋洗条件为草酸浓度0.1 mol/L,FeCl_3浓度0.4 mol/L;淋洗时间8 h;液土比20 m L∶1 g;淋洗1次,Pb去除率达到85.71%,Zn去除率达到78.49%。草酸-FeCl_3复合淋洗剂对土壤中酸溶态、可还原态和可氧化态的Pb和Zn均具有较好的去除效果,有效去除了土壤中生物活性高的Pb和Zn,降低了其环境风险。

Ways for remediation to Pb and Zn contaminated soil via washing-out effluent combined oxalic acid with FeCl3

The paper is to devote itself to an evaluation of an effluent combined oxalic acid with FeCl3 to remove Pb and Zn contaminants in the environmentally polluted soil in case the soil contaminated by high grade pollutants of Pb (726.0 mg/kg) and Zn (756.2 mg/kg).For the said study purpose,we have studied the best favorable washing conditions and the distribution of Pb and Zn contaminants when the washing activities are ready to go by using the oxalic acid-FeCl3.The results of our study indicate that,as compared with the single washing agent to be used,the effluent mixed with oxalic acid and FeCl3 has been found to be more effective for the aforementioned purpose.What is more,it has been proven to be more effective when FeCl3 is used as a single washing agent than along with oxalic acid.The optimal dosage for oxalic acid and FeCl3 account for 0.1 mol/L and 0.4 mol/Lrespectively.The other accompanying washing conditions can be illustrated as follows:the washing time to be taken:8 h;the ratio of the liquid to solid:20:1 (mL:g);and the washing cycles:1 for a single factor control experiment.The Pb and Zn removing rates can be made to reach 85.71％ and 78.49％,respectively.Through co-leaching,the mass ratio of Pb and Zn in the soil can be made to reach 103.75 mg/kg and 163.65 mg/kg,respectively,that is,to reach level two in accordance with the standard of the soil environment quality.And,finally,when analyzing the contaminants of Pb and Zn in the soil pre-and-pro the said coleaching activity done in BCR procedure,it can been found that the rate of Pb and Zn in the soil turns out to account for 3.93％ of the acid soluble,40.49％ for the reducible,5.36％ for the oxidizable,and 50.22％ for the residue of Pb.At the same time,the chief content constituent components in the soil are made of 24.68％ of acid soluble,15.65％ of reducible,13.79％ of oxidizable,and,45.88％ of residue Zn.After leaching,the results show that the removal rates of Pb and Zn can be made to be so high as 100％ of acid soluble,94.77％ of reducible,69.57％ of oxidizable,77.53％ of residue Pb and 100％ of the acid soluble,93.50％ of reducible,79.06％ of oxidizable,only 57.74％ of residue Zn.What is more,the effluent proves to have a strong impact on the morphology of Pb because of the efficient removal of residue Pb,whereas the acid soluble,reducible and oxidizable Pb/Zn can be removed efficiently,too.In addition,they are very easy to be absorbed by the plants.Thus,it can be inferred that the soil washing by using the effluent combined with oxalic FeC(]) can be used as an available form for successful removal of Pb and Zn,so as to reduce the human and environmental hazards of the remedial soil.