Ascorbic acid promoted sulfadimidine degradation in the magnetite-activated persulfate system by facilitating the Fe(III)/Fe(II) cycle.

Abstract

Persulfate (PS) activation technologies were of significant importance to the organic contaminant treatment. In this study, ascorbic acid (AA) was introduced to the traditional PS-activated process by using magnetite (Fe3O4) as the activator; herein, the degradation efficiency of sulfadimidine (SM2) was improved from 30 to 93% within 3h, and the observed removal rate was about 8.0 times higher than that of the Fe3O4/PS system. These improvements were found to be induced by the added AA because it could reduce the surface Fe(III) to Fe(II) on Fe3O4 and thus facilitate the Fe(III)/Fe(II) cycle, which was conducive to producing reactive oxygen species (ROSs) in the oxidation process during PS activation. Meanwhile, AA could also promote the Fe(III)/Fe(II) cycle in the homogeneous solution, further advancing the PS decomposition for SM2 degradation. The ROS trapping experiments indicated that SM2 removal in the Fe3O4/PS/AA system was attributed to •OH and •SO4-, and •SO4- was the dominant ROS. Moreover, the reusability test experiment revealed that magnetite retained good activity after five cycles in the Fe3O4/AA/PS system. This study provides a promising PS activation technology for efficient organics contaminant treatment.