Adsorption of Hg2+ and UO22+ from aqueous solution by aminated magnetic chitosan resin

The chitosan magnetic microparticles were prepared by the water/oil (W/O) emulsion cross-linking technique and then modified with ethylenediamine (EMCR) as an adsorbent to remove Hg2+ and UO22+ from the water solution. EMCR was characterized by optical microscopy, X-ray diffraction (XRD), the Fourier transform infrared (FT-IR) spectra, specific surface area and pore diameter.The effects of various parameters, such as pH, contact time, and initial concentration, on the adsorption of Hg2+ and UO22+ by EMCR were investigated. The results showed that the adsorption capacities of both Hg2+ and UO22+ increased with pH increasing. Selective separation of Hg2+ from UO22+ was achieved at pH<3. This was explained by the ability of Hg2+ to adsorb on chitosan resin through ion-exchange in the acidic media while UO22+ would not.Equilibrium data were fitted well with Langmuir isotherms with the maximum adsorption capacity of 2.14 mmol/g for Hg2+ and 1.50 mmol/g for UO22+. The adsorption reaction followed the pseudo-second order kinetics, indicating the main adsorption mechanism of chemical adsorption. The metal ion-loaded EMCR were regenerated with an efficiency of more than 90% using 0.02-0.1M thiourea. (authors)