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Abstract: Biosorbent Ni2+-imprinted chitosan beads were synthesized using epichlorohydrin cross-linking and nickel ion as the template for the selective adsorption of nickel ions from bimetallic aqueous solution comprising Ni2+ and Co2+. The effect of several parameters, i.e., pH, initial metal ions concentration, and contact time on the adsorption capacity and separation coefficient was examined. The selective and competitive adsorption processes of nickel and cobalt ions on the Ni2+-imprinted chitosan beads were studied separately. The equilibrium adsorption data of nickel could be well fitted with the Langmuir model even in the presence of high background cobalt concentrations, and the kinetics data were best fitted with the pseudo-second order kinetics model. In sole solution, the non-selective adsorption capacities of nickel and cobalt reached maximum (44.8 and 17.8 mg g-1, respectively) at a solution pH of 5. In a binary metal species solution, when the cobalt-to-nickel concentration ratio was 1,500, the separation coefficient (KNi/Co) was ~45, indicating the excellent selectivity of the beads toward nickel adsorption. It was also found that initially adsorbed cobalt ions on Ni-imprinted chitosan beads were displaced by subsequently adsorbed nickel ions from the solution. It was speculated that the displacement result from an adjacent adsorption and repulsion mechanism. Additionally, Fourier transform infrared and X-ray photoelectron spectroscopy results revealed that the Ni2+-imprinting technology enabled the generation of abundant recognition sites for nickel ions on the Ni2+-imprinted chitosan beads and amine groups primarily bound to Ni2+ via chelation
Template and target information: nickel ion, Ni(II)
Author keywords: Ni-imprinted chitosan, Separation coefficient, nickel, cobalt