Simultaneous oxidation of 4-aminophenylarsonic acid and adsorption of the produced inorganic arsenic by a combination of Co3O4-La2CO5@RSBC with peroxymonosulfate

Abstract

4-aminophenylarsonic acid (p-ASA) is usually employed as feed antibiotics which can kill bacteria, protozoa and spirochetes. When p-ASA is released into the environment by biological metabolism, it could be broken down to produce hypertoxic inorganic arsenic, including arsenite (AsO33-) and arsenate (AsO43-). In this study, cobalt and lanthanum composites loaded on rice straw biochar labelled as Co3O4-La2CO5@RSBC was obtained. The material was used as an efficient catalyst for peroxymonosulfate (PMS) activation and adsorbent to achieve the simultaneous degradation of p-ASA and adsorption of arsenic. 100% decomposition of p-ASA (50 μmol L-1) could be realized within 30 min, coupled with nearly complete removal of inorganic arsenic during 80 min at initial pH = 7. Co3O4-La2CO5@RSBC also possessed superior reusability and stability. Even in the third cycle, more than 95% of p-ASA was decomposed and meanwhile 92.5% of inorganic arsenic was removed. No cobalt ions were detected, and the concentration of lanthanum ions in the three cycles ranged from 8.05 to 9.90 mg L-1, which was much lower than those reported in previous studies. A series of the material characterizations, electron paramagnetic resonance technology and scavenger tests were utilized to unveil the possible catalytic mechanism and the transformation pathways of p-ASA and arsenic. It was confirmed that 1O2, O2∙-, OH∙, and SO4∙- generated from the PMS activation were responsible for the degradation of p-ASA and the oxidation of As(III) to As(V). Meanwhile, As(V) was rapidly adsorbed by Co3O4-La2CO5@RSBC. This study provides us with a novel and efficient approach to control p-ASA pollution in aqueous solution.