Efficient oxidation and absorption of As(III) from aqueous solutions for environmental remediation via CuO@MNW membranes

Abstract

Arsenic exists mainly in aqueous solution in the form of trivalent (As (Ш)) and pentavalent (As (Ⅴ)), but because of the fluidity and high toxicity of As (Ш), it is very difficult to be removed compared to As (Ⅴ), and therefore, this is the main change in arsenic-contaminated water treatment. To effectively remove the contaminant of As (Ш), a novel CuO nanoparticle coated MnO2 nanowire membrane (CuO@MNW) was constructed by physically depositing CuO nanoparticles onto the surface of MnO2 nanowires (MWs) in an ethanol after being assembled into a composite membrane material. Results showed that As (Ш) was oxidized by MnO2 to become As (V) and then adsorbed on the surface of CuO. The toxicity was reduced and the ability of CuO@MNW to remove As (Ш) was significantly improved. The as-obtained CuO@MNW exhibits outstanding As (Ш) removal efficiency and the maximum removal rate of 97%. The outstanding removal performance was ascribed to the rich -OH on the surface of CuO@MNW which facilitates ion exchange with arsenate ions. Furthermore, the possible separation mechanism was also proposed. The pH study indicated that acidic environment is conducive to the removal of As (Ш) by CuO@MNW, while under alkaline environment, the separation of arsenic was inhibited due to the electrostatic repulsion enhanced by the deprotonation of CuO@MNW surface and the competitive ions showed that the phosphate ions significantly reduce the removal efficiency of arsenic. Additionally, our essay proves that CuO@MNW possesses excellent recyclability and can still achieve 60% removal efficiency after five cycles. In short, the CuO@MNW is a promising separation material with a great potential for removing arsenic.