Hierarchically-structured Co-CuBi2O4 and Cu-CuBi2O4 for sulfanilamide removal via peroxymonosulfate activation

Herein, we report the syntheses of Co-CuBi2O4 and Cu-CuBi2O4 composites using a facile hydrothermal synthesis method for sulfanilamide (SA) removal via peroxymonosulfate (PMS) activation. The composites were characterized using FESEM, XRD and porosimeter and the results indicated that they were hierarchically-structured with several phases. The performance of the composites as catalysts for PMS activation was evaluated with respect to different initial pHs (4.5-9.5), catalyst loadings (L, 0.10-0.60 g L-1) and Oxone (R) dosages (D, 0.03-0.30 g L-1) and the empirical relationship between the K-app, L and D were obtained. The results also indicated that Cl- and humic acid exerted negative effect on SA degradation due to the intrinsic competition between Cl- and humic acid with SA for SO4 center dot- oxidation. The principal reactive radical in the Co-CuBi2O4/PMS and Cu-CuBi2O4/PMS systems was identified to be SO4 center dot-. A simple method to calculate the normalized steady-state concentrations of SO4 center dot- ([SO4 center dot-](Nss)). A simple method to calculate the normalized steady-state concentrations of SO4 center dot- ([SO4 center dot-](Nss)) and (OH)-O-center dot ([(OH)-O-center dot](Nss)) in the heterogeneous catalyst/PMS system is proposed. The results indicated that the generated SO4 center dot- and (OH)-O-center dot in the Co-CuBi2O4/PMS system were utilized at least five times more efficiently than the Cu-CuBi2O4/PMS system. The proposed method for calculating [SO4 center dot-](Nss) and [(OH)-O-center dot](Nss) can be potentially employed to characterize and compare the intrinsic catalytic activity of various heterogeneous catalyst/PMS systems in future studies. (C) 2016 Elsevier B.V. All rights reserved.