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Adsorption of lanthanum by magnetic alginate-chitosan gel beads

Wu, Dongbei, Zhang, Ling, Wang, Li, Zhu, Baohui, Fan, Liyan
Journal of chemical technology and biotechnology 2011 v.86 no.3 pp. 345-352
Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, adsorption, aqueous solutions, binding sites, cadmium, cation exchange, chitosan, cobalt, copper, electrostatic interactions, gels, ions, iron oxides, lanthanum, lead, metal ions, nanoparticles, nickel, oxygen, pH, pollution, risk, temperature
BACKGROUND: The risk of environmental pollution is aggravated by the increasing application of considerable amounts of rare earth elements in advanced materials. This paper reports the preparation of novel magnetic alginate-chitosan gel beads and their application for adsorption of lanthanum ions from aqueous solution. RESULTS: Stable magnetic alginate-chitosan gel beads with average diameter 0.85 ± 0.05 mm were prepared by loading iron oxide nanoparticles onto a combined alginate and chitosan absorbent. The performance of the prepared beads for the adsorption of lanthanum ions from aqueous solution was tested. It was found that various parameters, such as aqueous pH, contact time, metal ion concentration, ion strength and temperature, have an effect on the adsorption. Adsorption equilibrium was reached in 10 h and the maximum uptake capacity was 97.1 mg g⁻¹. From the analysis of pH, FTIR and XPS data, it is proposed that lanthanum adsorption proceeds through mechanisms of cation exchange, electrostatic interaction and surface complexation, with the oxygen atoms the main binding sites. In addition, lanthanum ions could be selectively separated from coexisting base metal ions such as Pb (II), Cd (II), Co (II), Ni (II) and Cu (II) in the aqueous solution. CONCLUSION: The prepared magnetic alginate-chitosan gel beads exhibit high uptake capacity and selectivity for lanthanum sorption, and thus can be used for adsorptive recovery of lanthanum from aqueous solutions.