Self-enhanced and efficient removal of As(III) from water using Fe-Cu-Mn composite oxide under visible-light...

Here, we prepared a novel nanostructured Fe-Cu-Mn composite oxide (FCMO_x) adsorbent using an ultrasonic coprecipitation method. The maximum adsorption capacity of As(III) and As(V) reached 158.5 and 115.2 mg/g under neutral conditions, respectively. The effects of several environmental factors (coexisting ions, solution pH, etc.) on the removal of inorganic arsenic using FCMO_x were studied through batch experiments. The results showed that except for PO₄^3- and high initial pH, it was not significantly affected by ionic strength and other existing anions, implying a higher selectivity and adaptability. Combined with EPR, FTIR, and XPS analysis, we concluded that the Cu component and the reactive oxygen species (ROS) it generates played a decisive role in maintaining the stability of the redox cycle between Mn(IV)/Mn(III)/Mn(II) and enhancing the oxidation efficiency of As(III). Meanwhile, the adsorption mechanism of As(V) was mainly through the replacement of the FCMO_x surface -OH to form stable inner-sphere arsenic complexes, while the removal mechanism of As(III) may involve the process of synergistic oxidation and chemisorption coupling. Additionally, the effective removal of As from the simulated As-contaminated water and its satisfactory reuse performance make FCMO_x adsorbents favorable candidates for the removal of As-contaminated water in the future.