Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Environ Sci Pollut Res Int. 2022 Dec;29(59):88989-89001. doi: 10.1007/s11356-022-21952-x. Epub 2022 Jul 16.
Electrokinetic (EK) remediation technology can enhance the migration of reagents to soil and is especially suitable for in situ remediation of low permeability contaminated soil. Due to the long aging time and strong hydrophobicity of polycyclic aromatic hydrocarbons (PAHs) from historically polluted soil, some enhanced reagents (oxidant, activator, and surfactant) were used to increase the mobility of PAHs, and remove and degrade PAHs in soil. However, under the electrical field, there are few reports on the roles and combined effect of oxidant, activator, and surfactant for remediation of PAHs historically contaminated soil. In the present study, sodium persulfate (PS, oxidant, 100 g L) or/and Tween 80 (TW80, surfactant, 50 g L) were added to the anolyte, and citric acid chelated iron(II) (CA-Fe(II), activator, 0.10 mol L) was added to catholyte to explore the roles and contribution of enhanced reagents and combined effect on PAHs removal in soil. A constant voltage of 20 V was applied and the total experiment duration was 10 days. The results showed that the removal rate of PAHs in each treatment was PS + CA-Fe(II) (21.3%) > PS + TW80 + CA-Fe(II) (19.9%) > PS (17.4%) > PS + TW80 (11.4%) > TW80 (8.1%) > CK (7.5%). The combination of PS and CA-Fe(II) had the highest removal efficiency of PAHs, and CA-Fe(II) in the catholyte could be transported toward anode via electromigration. The addition of TW80 reduced the electroosmotic flow and inhibited the transport of PS from anolyte to the soil, which decreased the removal of PAHs (from 17.4 to 11.4% with PS, from 21.3 to 19.9% with PS+CA-Fe(II)). The calculation of contribution rates showed that PS was the strongest enhancer (3.39.9%), followed by CA-Fe(II) (3.98.5%) (with PS), and the contribution of TW80 was small and even negative (-1.4~0.6%). The above results indicated that the combined application of oxidant and activator was conducive to the removal of PAHs, while the addition of surfactant reduced the EOF and the migration of oxidant and further reduced the PAHs removal efficiency. The present study will help to further understand the role of enhanced reagents (especially surfactant) during enhanced EK remediation of PAHs historically contaminated soil.
电动修复技术可以增强试剂在土壤中的迁移能力，特别适用于低渗透性污染土壤的原位修复。由于历史污染土壤中多环芳烃（PAHs）的老化时间长、疏水性强，因此使用一些增强试剂（氧化剂、活化剂和表面活性剂）来增加 PAHs 的迁移性，并去除和降解土壤中的 PAHs。然而，在电场作用下，对于氧化剂、活化剂和表面活性剂在修复历史污染土壤中的 PAHs 的作用和联合效应的报道较少。本研究在阳极液中添加过硫酸钠（PS，氧化剂，100g/L）和/或吐温 80（TW80，表面活性剂，50g/L），在阴极液中添加柠檬酸铁(II)（CA-Fe(II)，活化剂，0.10mol/L），以探索增强试剂的作用和贡献以及联合效应对土壤中 PAHs 去除的影响。施加 20V 的恒定电压，总实验时间为 10 天。结果表明，各处理中 PAHs 的去除率为 PS+CA-Fe(II)（21.3%）>PS+TW80+CA-Fe(II)（19.9%）>PS（17.4%）>PS+TW80（11.4%）>TW80（8.1%）>CK（7.5%）。PS 和 CA-Fe(II)的组合对 PAHs 的去除效率最高，而阴极液中的 CA-Fe(II)可通过电动迁移运移到阳极。添加 TW80 降低了电渗流并抑制了 PS 从阳极液向土壤的传输，从而降低了 PAHs 的去除率（PS 从 17.4%降至 11.4%，PS+CA-Fe(II)从 21.3%降至 19.9%）。贡献率的计算表明，PS 是最强的增强剂（3.3%9.9%），其次是 CA-Fe(II)（3.9%8.5%）（与 PS 一起），而 TW80 的贡献较小，甚至为负（-1.4%~0.6%）。上述结果表明，氧化剂和活化剂的联合应用有利于 PAHs 的去除，而表面活性剂的添加降低了电渗流和氧化剂的迁移，进一步降低了 PAHs 的去除效率。本研究将有助于进一步了解增强试剂（特别是表面活性剂）在电动强化修复历史污染土壤中 PAHs 过程中的作用。
