Fabrication of magnetic bifunctional composite via anchoring CoY on waste heating pad as a cycling material for peroxymonosulfate activation to degrade p-arsanilic acid and simultaneously eliminate secondary As(V)

Abstract

Herein, waste heating pad, which mainly contains iron and vermiculite components after calcination in air, was used to support cobalt-yttrium bimetallic oxide for the first time. The magnetic material (IV@CoY) was applied for the activation of peroxymonosulfate (PMS) to simultaneously realize the removal of p-arsanilic acid (p-ASA) and the secondary inorganic arsenic (As(V)). 50 µM p-ASA was completely degraded in the system of IV@CoY (0.2 g/L) and PMS (0.5 mM) within 7 min, and about 99 % of the produced As(V) was adsorbed within 150 min. Electrochemical experiments illustrated that IV@CoY possessed the superior conductivity as compared to CoY, which greatly boosted PMS activation. The pseudo-first-order rate constant (kIV@CoY) was high up to 0.873 min−1, which was 7.6 times larger than kCoY (0.115 min−1). Catalytic mechanism analyses revealed that the produced SO4•−, •OH and 1O2 participated in the oxidation of p-ASA and As(III). The adsorption of the produced As(V) was achieved by ion exchange with −OH/CO32− on the surface of IV@CoY. The degradation pathways of p-ASA were further proposed on the basis of the detection of its intermediate products. Initial pH exerted a significant effect on the degradation-adsorption reaction and weak acidic or neutral condition was beneficial to the removal of p-ASA and As(V). To evaluate the practical application potential of IV@CoY, the disposal of p-ASA and secondary As(V) were also carried out in real water samples. Furthermore, IV@CoY was consecutively used for 5 times, and almost 100% degradation of p-ASA and over 97% adsorption of inorganic arsenic were still achieved even in the fifth round, which prove its high stability and reusability. Our results fully demonstrate that the magnetic IV@CoY is a promising catalyst to activate PMS for eliminating organoarsenic from water.