Protocatechuic acid enhanced Fe(III) activated peroxymonosulfate system for Sulfamethoxazole degradation in groundwater

Abstract

The advanced oxidation process based on Fe(Ⅱ) activated is easy to produce Fe(Ⅲ) accumulation, and the slow process of Fe(III)/Fe(II) conversion greatly hinders pollutant degradation performance of Fe(III)/peroxymonosulfate (PMS) system. Herein, protocatechuic acid (PCA)-regulated Fe(III)-activated PMS system was proposed for remediation of SMX-contaminated groundwater. The results presented the highest degradation efficiency (97.2 %) at room temperature and neutral pH with appropriate PCA-Fe(III) ratio (1:3) and PS concentration (1 mM), which was 89.5 % higher than that of the system without PCA, and over 60 % higher than that of other acid-regulated systems. The excellent degradation performance was principally owing to the reduction and chelation of PCA, which expedited the circulation of Fe(III)/Fe(II) via generating PCA-Fe chelate and benzoquinone, thus promoting the PMS activation. Moreover, SO4•−, O•H, O2•−, and 1O2 worked together to contribute to SMX decomposition, and 1O2 played a dominant role. In addition, the system had strong tolerance to co-existing ions (e.g., CO32−, Cl−, and NO3−) and humic acid in groundwater, Cl-, NO3− and HA had no significant effect on SMX degradation, and although CO32− reduced the degradation efficiency of SMX, more than 80 % of SMX was removed after reaction. And the system possessed universal applicability to real water bodies and different pollutants. Overall, the PCA/Fe(III)/PMS system presented preeminent application potential for the remediation of organics-polluted groundwater.