Enhanced removal of sulfamethoxazole in soil by ball-milled Fe0-FeS@BC activated persulfate process

A heterogeneous combination of different materials is a viable way to prompt persulfate (PS) activation in the removal of organic compounds in soil. In this study, the hybrids of Fe0, FeS and biochar (Fe0-FeS@BC) was synthesized by ball milling method to activate PS in soil-water suspension environment to degrade sulfamethoxazole (SMX) which remains a high detection rate in soil and may have serious eco-system and health risks. Fe0-FeS@BC performed the highest SMX removal efficiency among the tested materials (BC, FeS, Fe0, ball milled Fe0-FeS, and Fe0-FeS@BC). The interference and involvement of mineral fraction (MF) and soil organic matter (SOM) complicated the removal process of SMX in soil/Fe0-FeS@BC/SMX/PS system. The coexistence of 1O2, O2•-, •OH, SO4 • - and persistent free radical (PFR) was proposed to explicate the removal of SMX in soil/Fe0-FeS@BC/SMX/PS system. In addition, several influencing factors incorporating Fe0-FeS@BC dosage, Fe0-FeS/BC mass ratio, initial pH, PS dosage and soil-water ratio were investigated to demonstrate the applicability of the Fe0-FeS@BC/PS system in soil remediation. Prevailing reducing condition possessed high Fe3+/Fe2+ cycle that resulted in the continuous SMX degradation. Correspondingly, intermediates and possible degradation pathways of SMX were also proposed. In general, the Fe0-FeS@BC/PS system performed prompting efficiency on the removal of SMX in soil and showed great potential for soil remediation.