Feng Shixu, Ou Yiwen, Li Xintong, Wu Yunhao, Deng Yaxi, Zhao Hongxia
Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environ. Sci. Technol., Dalian University of Technology, Dalian, 116024, China.
Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environ. Sci. Technol., Dalian University of Technology, Dalian, 116024, China.
Environ Res. 2025 Aug 1;278:121681. doi: 10.1016/j.envres.2025.121681. Epub 2025 Apr 24.
Soil contamination with polycyclic aromatic hydrocarbons (PAHs) is severe, and their high biotoxicity and recalcitrance made effective remediation challenging. The heterogeneous Fenton process utilizing nanoscale zero-valent iron (nZVI) has been recognized as a promising technology for organic pollutant removal in various remediation media (e.g., soil, groundwater, sediments). However, nZVI cannot release sufficient Fe(II), limiting its ability to activate hydrogen peroxide (HO). Therefore, this study proposes the addition of oxalic acid (OA), which is economical, environmentally friendly, and readily available, to enhance nZVI-activated HO for remediating PAHs-contaminated soil. Results showed that the addition of OA to the nZVI/HO system increased the removal efficiency of benzo [a]pyrene (BaP) from 39.28 % to 95.33 % within 60 min, with over 80 % efficiency for various PAHs in both actual and spiked soils. Free radical scavenging experiments indicated that hydroxyl radicals (•OH) were the primary contributors to BaP removal. Further investigation of the mechanism revealed that OA promoted the dissolution of large amounts of Fe(II) from nZVI through the formation of a FeCO shell layer with high proton (H) conductivity on the surface of nZVI as well as the lowering of pH to provide H to nZVI. Based on the results of mass spectrometry analysis and ECOSAR and T.E.S.T. software, BaP degradation intermediates and their toxicity were identified. The toxicity of all degradation intermediates was lower than that of BaP. These findings provided a simple and cost-effective advanced oxidation method for the removal of PAHs from soil.
土壤中多环芳烃（PAHs）污染严重，其高生物毒性和难降解性使得有效修复具有挑战性。利用纳米零价铁（nZVI）的非均相芬顿工艺已被认为是在各种修复介质（如土壤、地下水、沉积物）中去除有机污染物的一种有前景的技术。然而，nZVI不能释放足够的Fe(II)，限制了其活化过氧化氢（HO）的能力。因此，本研究提出添加经济、环保且易于获得的草酸（OA），以增强nZVI活化的HO对PAHs污染土壤的修复效果。结果表明，在nZVI/HO体系中添加OA，可使苯并[a]芘（BaP）在60分钟内的去除效率从39.28%提高到95.33%，在实际土壤和加标土壤中，各种PAHs的去除效率均超过80%。自由基清除实验表明，羟基自由基（•OH）是去除BaP的主要贡献者。对其作用机制的进一步研究表明，OA通过在nZVI表面形成具有高质子（H）传导性的FeCO壳层以及降低pH值为nZVI提供H，促进了大量Fe(II)从nZVI中溶解。基于质谱分析结果以及ECOSAR和T.E.S.T.软件，鉴定了BaP降解中间体及其毒性。所有降解中间体的毒性均低于BaP。这些发现为从土壤中去除PAHs提供了一种简单且经济高效的高级氧化方法。
