H2O2氧化联合化学淋洗修复电镀工厂铬污染黏性土壤的试验研究

以合肥某电镀工厂遗留的铬污染黏性土壤为研究对象,采用H₂O₂氧化联合盐酸和柠檬酸进行化学淋洗对土壤中的总铬和Cr(Ⅵ)进行修复去除,并对氧化剂H₂O₂的浓度、淋洗剂盐酸和柠檬酸的浓度对土壤中铬的去除率的影响进行探究。结果表明:单独采用H₂O₂氧化,在浓度为10.0%时,其对土壤中铬的去除效果最佳,Cr(Ⅵ)去除率达到51.5%,总铬去除率达到20.9%;单独H₂O₂氧化、盐酸和柠檬酸淋洗后土壤中Cr(Ⅵ)浓度仍然超过GB 36600—2018《土壤环境质量 建设用地土壤污染风险管控标准(试行)》二类用地标准。而对H₂O₂氧化后土壤继续联合盐酸或柠檬酸淋洗,当盐酸浓度为1.0 mol/L、固液比为1∶4时,H₂O₂氧化联合化学淋洗修复后的土壤中Cr(Ⅵ)浓度为4.4 mg/kg,达到GB 36600—2018二类用地标准,此时土壤中Cr(Ⅵ)去除率为85.5%,总铬去除率为50.6%。Tessier五步提取形态分析表明:修复后土壤中残渣态铬的比例从44.7%提高到93.4%,显著降低了铬二次释放的风险。研究结果可为铬污染土壤的治理修复和铬的回收利用提供参考。

EXPERIMENTAL STUDY OF H2O2 OXIDATION COUPLED WITH CHEMICAL WASHING TO REMEDY CHROMIUM-CONTAMINATED CLAYED SOIL FROM AN ELECTROPLATE FACTORY

In this work, H₂O₂ oxidation combined with soil chemical washing to remove hexavalent chromium and total chromium of contaminated soil collected from the electroplating factory in Hefei was developed. The effects of concentration of hydrogen peroxide, and eluting agents on remediation efficiency of chromium-contaminated soil were evaluated via batch experiment. The maximum removal efficiencies of hexavalent chromium and total chromium could achieve 51.5% and 20.9% for 10% H₂O₂ oxidation treatment. The soil was also washed by hydrochloric acid alone and citric acid alone, respectively, and the hexavalent chromium concentrations that remained in the soil under these conditions still exceeded the standard value in Soil Environmental Quality, Risk Control Standard for Soil Contamination of Development Land in China. However, hexavalent chromium and total chromium removal efficiency were promoted after combining H₂O₂ oxidation with hydrochloric acid washing, achieving 85.5% and 50.6% when the concentration of hydrochloric acid was 1.0 mol/L and the solid-liquid ratio was 1∶4. The hexavalent chromium that remained in the soil was as low as 4.4 mg/kg, which was lower than the standard value. The morphological analysis by Tessier’s five-step extraction showed that the proportion of residual form obtained in the soil increased from 44.7% to 93.4% after this technology was applied, which significantly reduced the risk of chromium re-release. This work can provide a way for remediation and utilization of heavy metal chromium from chromium-contaminated soil.