Efficient degradation of sulfamethazine in a silicified microscale zero-valent iron activated persulfate process

Abstract

Microscale zero-valent iron (mZVI) is used as a catalyst for peroxide activation and, has attracted considerable attention for the degradation of organic contaminants. However, surface inherent oxide films impedes electron transfer in mZVI and decrease its activation efficiency. Herein, the mZVI surface was modified by sodium disilicate (Si-mZVIbm) using a mechanical ball-milling approach. The mechanochemically silicified mZVI enhanced the sulfamethazine removal rate by 2.9–23.8 fold in relation to unmodified ZVI; this rate increased with the Si/Fe molar ratio (0–8%). Reactive intermediates, including radicals and non-radicals, were efficiently generated via peroxydisulfate (PDS) activation over Si-mZVIbm both SO4•- and Fe(IV) contributed toward sulfamethazine removal. The excellent performance of PDS activation over Si-mZVIbm particles was attributed to the continuous generation of ferrous ions, which was due to the accelerated iron release and more effective Fe3+/Fe2+ cycles in the Si-mZVIbm/PDS system after silicification.