Separatable polydopamine-coated cobalt-chitosan beads for Cr(VI) removal from wastewater with superior capacity

Abstract

The discharge of hexavalent chromium [Cr(VI)] in industrial wastewater into the natural environment can seriously cause harm to the environment and human health. We modified chitosan (CS) with Co and polydopamine (PDA) to synthesize a spherical adsorbent (CS–Co/PDAHCl) for Cr(VI) removal from wastewater. Co doping can help CS–Co/PDAHCl maintain a high adsorption capacity (666.7 mg g-1) for Cr (VI) while retaining a complete bead shape after multiple recycling. In addition, CS–Co/PDAHCl can maintain 96% of its initial adsorption capacity after five adsorption cycles, demonstrating a strong regeneration ability. Under competitive conditions, the adsorption capacity of CS–Co/PDAHCl for Cr(VI) greatly exceed its adsorption capacity for Ni (II) and Mn (II). Because of the high selectivity of CS–Co/PDAHCl for Cr(VI), 1 kg of CS–Co/PDAHCl (cost approximately $31) could reduce the concentration of Cr(VI) in 87 m3 of secondary electroplating wastewater containing various complex components to the drinking water standard. Owing to the high selective adsorption capacity of CS–Co/PDAHCl for Cr(VI) and its good regeneration ability and expected economic feasibility, CS–Co/PDAHCl can find potential applications in removing Cr(VI) from real wastewater.