直流电压施加对Pb/As复合污染土壤电动修复的影响

IMPACT OF DC VOLTAGE ON ELECTRO-REMEDIATION OF Pb AND As CONTAMINATED SOIL

重金属复合污染土壤的治理修复对环境污染防治具有重要意义。以河南某冶炼厂地表含Pb、As复合污染土壤为对象,通过施加不同直流电压对污染土壤进行电动修复,基于迁移率和形态变化对修复效果进行评价。修复过程中,分别对电流变化、Pb/As的迁移规律、土壤含水率、电导率、pH值以及Pb/As的形态转化进行研究。结果表明:施加的直流电压变化对土壤中Pb的迁移影响显著,而对As的迁移影响较弱;当施加直流电压为10 V时,土壤中阴极区域的As含量可降至43.18 mg/kg,当施加的直流电压为30 V时,土壤中阴极区域的Pb含量可降至334 mg/kg,先施加低压后施加高压更有利于提升Pb、As复合污染土壤的电动修复效果;修复完成后Pb和As的弱酸态占比降低,可还原态占比升高,土壤中的Pb和As含量低于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)》中第1类建设用地筛选值。

The remediation and restoration of soil contaminated by heavy metals is considered to be of great significance to the prevention and control of environmental pollution. In this paper, a complex contaminated soil on the surface with Pb and As in a smelter in Henan was taken as the research object. By applying different DC voltages, electrokinetic remediation was carried out. Then based on the mobility and form changes, the restoration effect was evaluated. During the restoration process, we studied the current change, Pb/As migration law, soil moisture content, electrical conductivity, pH value, and Pb/As speciation transformation. The results showed that the change of applied DC voltage had a stronger effect on the migration of Pb in the soil, but a weaker effect on the migration of As. When the applied DC voltage was 10 V, As content in the cathode region of the sample soil was reduced to 43.18 mg/kg;and when the applied DC voltage was 30 V, the Pb content in the cathode region was reduced to 334 mg/kg. The operation of applying low-voltage current first and then high-voltage current was more effective to improve the electrokinetic remediation effect of Pb and As compound contaminated soil. In the restored soil, the proportion of weak acid state of Pb and As decreased, and the proportion of reducible state increased. The content of Pb and As in soil was lower than the screening value for construction land Class Ⅰ in GB 36600—2018.