Removal of refractory organic matter from landfill-contaminated groundwater by a permeable reactive barrier coupled with an Fe0/PMS advanced oxidation system

Abstract

Advanced oxidation technology based on peroxymonosulfate (PMS) has attracted much attention because of its good degradation and even mineralization of refractory organic matter, but it is less used in the removal of refractory organic matter from landfill-contaminated groundwater (CGW). In this study, an Fe0/PMS advanced oxidation system-based permeable reactive barrier (Fe0/PMS-PRB) has been employed to remove refractory organic matter from landfill leachate CGW. The results show that the Fe0/PMS system offers a significantly higher removal efficiency of organic matter, especially humus, from CGW than other control systems. The main active oxygen species are SO4•─ and HO•, which can facilitate electron-transfer, carbonylation, electrophilic addition, decarboxylation, and other pathways to effectively degrade various refractory organic substances (e.g., bisphenol A, diclofenac acid, and ciprofloxacin). The pseudo-first-order reaction rates reached 0.1083, 0.3030, and 0.0641 min−1, respectively, effectively reducing the bio-toxicity of the effluent. Based on observations by scanning electron microscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy, a reaction mechanism was proposed, which involves homogeneous oxidation, heterogeneous oxidation, adsorption, and precipitation of Fe0. In long-term seepage tests, under conditions of an Fe0 loading of 0.7 g, a PMS concentration of 0.8 mm, and a hydraulic retention time of 15 min, after running for 10 pore volumes, the removal extents of aromatic organic matter and total organic carbon from the CGW by the Fe0/PMS-PRB reached 79.01 % and 68.25 %, respectively. Therefore, Fe0/PMS-PRB can effectively remove refractory organic matter from CGW and has good application prospects.