Iron and nitrogen modified sludge biochar efficiently activated persulfate for mineralization of sulfamethoxazole in groundwater

Abstract

In this work, iron-nitrogen co-doped sludge biochar (Fe@N-SBC) was successfully prepared by a facile synthetic method using sludge as a precursor. We investigated the degradation effect of Fe@N-SBC activated peroxodisulfate (PDS) on sulfamethoxazole (SMX), a common antibiotic pollutant in groundwater, and explored its reaction mechanism. The removal of SMX in the Fe@N-SBC /PDS system reached more than 99%, and it could still reach 97.8% in actual groundwater with complex composition. Under the condition of sufficient dosage, the final mineralization of SMX can reach more than 95%, which means that there is no risk of secondary pollution of intermediate products to the environment. The main mechanism for the degradation of SMX by Fe@N-SBC/PDS system is the electron transfer mechanism mediated by the substable [Fe@N-SBC-PDS* ] complex formed on the surface of Fe@N-SBC, followed by the non-radical reaction mechanism dominated by singlet oxygen, and thus it has a wide pH range and strong resistance to ionic interference. The addition of N can significantly reduce the leaching of metal ions in the material, and the leaching amount of Fe in Fe@N-SBC is only 0.1 μg/g, while other toxic and harmful heavy metals are hardly leached. Overall, Fe@N-SBC is an environmentally friendly catalyst with simple preparation, high catalytic activity, wide applicable pH range, strong resistance to ionic interference, and selectivity for electron-rich organics, which has good application prospects in practical groundwater treatment. • The Fe@N-SBC/PDS system can achieve removal rate of 97.8% for SMX in real groundwater. • Over 95% mineralization of SMX could achieved in the Fe@N-SBC/PDS system. • Non-free radical pathways are mainly involved in the degradation process. • The addition of N can significantly reduce the leaching of metal ions in the catalyst.