SORPTION OF URANYL IONS BY A MODIFIED CHITOSAN - KINETIC AND EQUILIBRIUM STUDIES

The uranium sorption of an ascorbic chitosan derivative polymer (N.D.T.C. N-[2-(1,2-dihydroxyethyl) tetra-hydrofuryl] chitosan) was shown to be three to four times greater than chitosan under the same conditions, reaching 600 mgU.g-1 polymer (i.e. 2.5 mmolU.g-1 polymer). The effect of variation of the classic parameters was studied: pH, metal concentration and particle size. pH and metal concentration, which induced a change in metal solution chemistry, were found to be the controlling parameters, mainly affecting intraparticle diffusion; the diffusion rate is strongly affected by ionic size of solute, as opposed to a limited effect on external mass transfer. pH plays an important part in equilibrium studies, and sorption isotherms are mainly a function of pH. The Freundlich model shows a better correlation coefficient than the Langmuir modal when fitted to experimental results; the uptake mechanism involves a monolayer sorption with molecular interactions between molecules sorbed on surface.