Facile fabrication of Co-doped cerium-manganese oxide for enhancing peroxymonosulfate activation to rapidly achieve simultaneous elimination of p-arsanilic and its oxidation by-product As(V)

Abstract

Efficient purification of the wastewater containing organoarsenic by activated peroxymonosulfate (PMS) usually faces with a great challenge because the degradation of organoarsenic is coupled with the release of its byproduct As(V). Heterogeneous catalysts with catalytic and adsorption functions show great potential in activating PMS for the degradation of organoarsenic and the removal of secondary inorganic arsenic. In this study, Co-CeMnO was designed and fabricated to realize simultaneous elimination of p-arsanilic (p-ASA) and As(V) in Co-CeMnO (0.2 g/L)/PMS (0.25 mM) system, in which 50 µM p-ASA was almost completely degraded within 5 min and approximately 100% of the produced As(V) was removed within 30 min. The rate constant of the pseudo-first-order kinetics for the p-ASA degradation by PMS mediated with Co-CeMnO was high up to 0.65 min−1, approximately 6.5 times higher than that in the system of CeMnO/PMS. It was revealed that SO4•−, •OH and 1O2 acted as the main oxidant species responsible for the oxidation of organics and As(III), and the surface −OH of Co-CeMnO led to the adsorption of As(V) via ion exchange. The excellent reusability and stability of Co-CeMnO was verified by five cycles with high removal efficiencies of p-ASA (>92% within 10 min) and arsenic (>98% within 90 min) and low leached metal ion concentrations (Co ions < 0.27 mg/L; Mn ions < 0.15 mg/L; Ce ions ≈ 0). Under the condition of initial pH 5, p-ASA was degraded completely and over 98% of total arsenic was adsorbed in different water matrices, indicating the practical application potential of Co-CeMnO/PMS system. Thus, the present study provided a reliable PMS activation strategy by constructing bifunctional catalysts to achieve satisfactory treatment of the wastewater containing p-ASA.