LAUSR

Abstract Arsenite (As(III)) is more mobile and has higher toxicity than arsenate [As(V)]. To improve the removal of As(III), preoxidation of As(III) to As(V) is considered necessary due to its low affinity to many adsorbents. However, this method usually involves extra operations and costs. In this study, an original S-doped copper- lanthanum bimetallic oxide (S-CuLaO) was prepared as an adsorbent material for the removal of As(III) via simultaneous oxidation and adsorption (no extra chemical agents as oxidants). The material was successfully synthesized with a simple co-precipitation method. The majority of Cu species present in the adsorbent was Cu(I). The maximum adsorption capacity of the adsorbent towards As(III) reached 314.91 mg g−1, which far exceeds that of previously reported adsorbents. In a wide pH range of 3 to 9, the adsorbent exhibited excellent removal efficiency of As(III), and 30 mg L−1 As(III) was completely removed by S-CuLaO (0.2 g L−1). The mechanistic investigation revealed that the presence of Cu(I) in the adsorbent allowed cooperation with the dissolved O2 to promote the oxidation of As(III) by the generated O 2 • - to As(V). The produced As(V) was adsorbed onto the surface of the adsorbent via electrostatic attraction. Subsequently, –OH groups on the adsorbent surface participated in As(V) adsorption via ligand exchange. Furthermore, the removal efficiency of As(III) (1 mg L−1) in well water by S-CuLaO (1.0 g L−1) maintained >99% even in the fourth cycle (without regeneration), resulting in a residual arsenic concentration of 0.7 μg L−1. Therefore, the use of S-CuLaO is promising and feasible for the effective removal of As(III) from aqueous solution.