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

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/PDA HCl ) for Cr(VI) removal from wastewater. Co doping can help CS–Co/PDA HCl 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/PDA HCl 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/PDA HCl for Cr(VI) greatly exceed its adsorption capacity for Ni (II) and Mn (II). Because of the high selectivity of CS–Co/PDA HCl for Cr(VI), 1 kg of CS–Co/PDA HCl (cost approximately $31) could reduce the concentration of Cr(VI) in 87 m 3 of secondary electroplating wastewater containing various complex components to the drinking water standard. Owing to the high selective adsorption capacity of CS–Co/PDA HCl for Cr(VI) and its good regeneration ability and expected economic feasibility, CS–Co/PDA HCl can find potential applications in removing Cr(VI) from real wastewater .