The treatment of As(III)-contaminated water by using granular Fe-Mn-Cu composite oxide: Removing As(III) via the oxidation-adsorption process and handling the release of manganese ions

It is a challenge to obtain an outstanding removal performance for the treatment of As(III)-contaminated water without the risk of secondary pollution. In this study, a novel granular adsorbent of Fe-Mn-Cu composite oxide (GFMCO) was fabricated by the redox-precipitation method. Batch adsorption experiments were conducted to investigate the adsorption behavior of As(III) onto GFMCO, including adsorption isotherms, adsorption kinetics, the influences of pH and competing anions, and reuse performance. The adsorption equilibrium of As by GFMCO could be achieved within 12 h. As(III) can be effectively oxidized to As(V) and adsorbed by GFMCO with a theoretical maximum As adsorption capacity of 72.88 mg/g. The As removal performance remained stable within a wide pH range of 3–9. Phosphate and silicate anions inhibited As removal, whereas chloride ions, sulfate anions, calcium ions, and magnesium ions had little effect. In addition, GFMCO could be successfully regenerated and reused with almost no loss in adsorption capacity during four consecutive cycles. Moreover, the GFMCO-packed column used as an adsorption reactor could produce approximately 969 bed volumes of treated water with the effluent arsenic concentration below 10 μg/l. Although divalent manganese ions (Mn(II)) were released from the GFMCO-packed column, efficient Mn(II) removal could be achieved with the combination of sodium hypochlorite dosing and the manganese sand filtration. Overall, this work provides a promising adsorbent for As(III) removal with satisfactory efficiency and good security.