Efficient degradation of roxarsone and simultaneous in-situ adsorption of secondary inorganic arsenic by a combination of Co3O4-Y2O3 and peroxymonosulfate

Roxarsone (ROX), as one of aromatic organoarsenic compounds (AOCs), is extensively used in livestock industry, which tends to transform into high-toxic inorganic arsenic in environments. Herein, a bifunctional Co3O4-Y2O3, possessing extremely excellent catalytic and adsorption performance due to the synergy of Co3O4 and Y2O3, was designed and employed to activate peroxymonosulfate (PMS) for the elimination of ROX and the simultaneous in-situ adsorption of secondary inorganic arsenic, in which Co3O4 acted as the primary catalyst, and Y2O3 served as the main adsorbent. 50 mu M (3.75 mg-As/L) of ROX was almost completely degraded, coupled with the conversion of As(III) to As(V) in the system of Co3O4-Y2O3 (0.2 g/L) and PMS (0.5 mM) within 15 min at initial pH 7. Meanwhile, > 99.3% of the secondary As(V) would be removed within 120 min. The reactive oxygen species (ROS) were identified to be (OH)-O-center dot, SO4 center dot-, and O-1(2), which were responsible for the ROX degradation and the formation of As(V). Simultaneously, the produced As(V) were effectively adsorbed via the ligand/anion exchange with surface -OH and CO32- anions of Co3O4-Y2O3. The possible degradation pathways of ROX were further proposed on the basis of the intermediates identification. Our findings may provide an insight into the degradation of AOCs and the simultaneous removal of secondary inorganic arsenic via the PMS activation with Co3O4-Y2O3.