EFFECT OF THE STRONGLY BASIC ANION EXCHANGER AB-17–8 DISPERSION ON THE KINETICS OF URANIUM (VI) REMOVAL FROM MODEL SOLUTIONS

The by-products of commercial ion exchange resins are characterized by varying degrees of particle dispersion. They are potential adsorbents for the removal of heavy metal ions, including uranium, from aqueous media. The effect of the strongly basic anion exchanger AB-17–8 in the Cl-form dispersion on the efficiency, kinetics and mechanism of uranium removal from model carbonate solutions was investigated. Dispersion analysis was conducted for three fractions of anion exchanger AB-17–8. The studied fractions are polydisperse systems with effective diameters of 31–122 µm (fraction 1), 14–80 µm (fraction 2), and 5–70 µm (fraction 3). The kinetics of uranium adsorption was studied as a function of adsorbent dispersion and temperature. It was found that the uranium adsorption rate increases with decreasing adsorbent particle size and increasing temperature. The activation energy of the adsorption process was calculated (kJ/mol): 45.1 (fraction 1), 11.6 (fraction 2) and 7.5 (fraction 3). It was found that uranium adsorption occurs in the transition region (fraction 1) or in the diffusion region (fractions 2 and 3). The kinetics of uranium adsorption was modelled and the main kinetic characteristics of the uranium adsorption process were calculated using kinetic models (pseudo-first and pseudo-second order) and diffusion models (external diffusion and internal Boyd’s diffusion). It was found that the kinetics of uranium adsorption follows a pseudo-second-order model and proceeds in a mixed-diffusion regime, but external diffusion limits the overall process rate to a greater extent.