Selective and efficient removal of As(III) from water by Ce-Mn oxide-modified biochar: Synergetic role of rapid oxidation and enhanced adsorption

Abstract

Pre-oxidation of trivalent arsenic (As(III)) to pentavalent arsenic (As(V)) with subsequent in-situ adsorption serves as a viable strategy for the As(III) removal from water environment. Herein, a simple pyrolysis-impregnation-pyrolysis method was used to create the Ce-Mn oxides modified biochar (CMBC) and the as-prepared CMBC was applied to a persulfate (PS) system to establish a multiphase catalytic process for the rapid oxidation of As(III) and efficient adsorption of As(V) in aqueous solution. The maximum adsorption capacity of As(III) arrived up to 162.09 mg g−1 under CMBC/PS system, and the excellent removal performance of As(III) could be achieved in both acidic and alkaline situations (pH ranging from 3 to 11). Ionic strength, natural organic matter, as well as coexisting anions (except for phosphate) and cations did not inhibit As(III) removal in CMBC/PS system. Especially, the adsorption of As(III) under diverse coexisting ions reached adsorption dynamic equilibrium within 90 minutes, implying that the process has relatively fast adsorption kinetics and is resistant to interference. Moreover, the adsorbent could be effortlessly renewed with regenerant while retaining the desired removal rate. Persulfate activated by CMBC generated radical species, however, the free radical trapping experiments, EPR experiments, and electrochemical technique analysis revealed that there existed a non-radical-dominated electron transfer pathway in the CMBC/PS system. The ideal regeneration performance, anti-disturbance ability, and high adsorption capacity imply that CMBC/PS may serve as a promising approach to removal As(III) via adsorption method, and the results also gain insight into the electron transfer pathway in the system.