Formation and recovery of Co2+, Ni2+, Cu2+ macromolecular complexes with polystyrene and acrylic acid

The formation and structure of Co2+, Ni2+ and Cu2+ macromolecular complexes with a series of polystyrene and acrylic acid copolymers (PSt/AA) were studied. Both the copolymers and the metal complexes (M-PSt/AA) were characterized by FTIR, elemental analysis, Gel Permeation Chromatography and AAS. It is shown that the PSt/AA copolymer has rather strong coordination ability to the metal ions by chelation with the carboxylate group, and the microstructures of the M-PSt/AA complexes can be well controlled. Its adsorption behavior toward Co2+, Ni2+ or Cu2+ and various related parameters in the separation process were determined. The results indicate that the adsorption capability varies with pH and the maximum adsorption capacities were 337 mg/g for Co2+, 338 mg/g for Ni2+ and 341 mg/g for Cu2+ at around pH 7. Adsorption isotherms reveal that the adsorption process is consistent with the Freundlich equation. Experiments show that PSt/AA can recover Co2+, Ni2+ or Cu2+ with a high adsorption rate and high selectively coefficient from a simulated industry solution containing Ca2+ and Mg2+ as impurities. The resin can be readily stripped with acid and recycled for re-use after transformation to its sodium form.