Paracetamol degradation by photo-assisted activation of peroxymonosulfate over ZnxNi1−xFe2O4@BiOBr heterojunctions

Abstract

Developing efficient and recyclable heterogeneous catalysts in advanced oxidation processes towards aqueous organic pollutants degradation on real samples remains challenging. Herein, semiconductor heterojunction photocatalysts with variable composition (ZnxNi1−xFe2O4@BiOBr; x = 0, 0.2, 0.5, 0.8 and 1) were synthesized through a two steps hydrothermal process. The influence of cation composition, microstructure heterojunction, catalyst and peroxymonosulfate (PMS) dosage and pH variation were investigated for the degradation of paracetamol (PAM) as target pollutant. Real degradation datasets from commercial tablet solutions were compared with pure paracetamol (p-PAM). Doping Ni into ZnFe2O4 significantly affect the catalytic performance as well as enable magnetic removal of catalyst. The ratio between ZnxNi1−xFe2O4 and BiOBr was also optimized to realize best catalytic degradation. Complete removal of PAM was achieved after 100 min at optima conditions (0.5 g/L Zn0.8Ni0.2Fe2O4@BiOBr, 2 mM PMS, 10 mg/L PAM, UV-A, pH 7) while 64% removal account in 100 min in darkness. A chemical method probe, through free radical scavengers, revealed that SO4•- is the main specie involved in the degradation reaction. A novel degradation mechanism was proposed by the identification of eight different intermediates. Reusability of the heterojunction photocatalysts was studied after five consecutive treatments. Zn0.8Ni0.2Fe2O4@BiOBr efficiently activate PMS under UV-A irradiation vanishing PAM, one contaminants of most emerging concern found in water. This study will shed light into the understanding of photo-assisted PMS activation for aqueous pollution abatement.