Sorption profile and chromatographic separation of uranium (VI) ions from aqueous solutions onto date pits solid sorbent

Abstract

The retention profile of uranium (VI) as uranyl ions (UO 2 2+) from the aqueous media onto the solid sorbent date pits has been investigated. The sorption of UO 2 2+ ions onto the date pits was achieved quantitatively (98 ± 3.4%, n = 5) after 15 min of shaking at pH 6–7. The sorption of UO 2 2+ onto the used sorbent was found fast, followed by a first order rate equation with an overall rate constant, k of 4.8 ± 0.05 s −1. The sorption data were explained in a manner consistent with a “solvent extraction” mechanism. The sorption data were also subjected to Freundlich isotherm model over a wide range of equilibrium concentration (1–20 μg mL −1) of UO 2 2+. The results revealed that, a “dual-mode” of sorption mechanism involving absorption related to “solvent extraction” and an added component for “surface adsorption” is most likely operated simultaneously for uranyl ions uptaking the solid sorbent. The thermodynamic parameters (−Δ H, Δ S and Δ G) of the uranyl ions uptake onto the date pits indicated that, the process is endothermic and proceeds spontaneously. The interference of some diverse ions on the sorption UO 2 2+ from the aqueous media onto the date pits packed column was critically investigated and the data revealed quantitative collection of UO 2 2+ at 5 mL min −1 flow rate. The retained UO 2 2+ was recovered quantitatively with HCl (3.0 mol L −1) from the column at 5 mL min −1 flow rate. The mode of binding of the date pits with UO 2 2+ was determined from the IR spectral date bits before and after extraction of uranium (VI). The height equivalent (HETP) and the number ( N) of theoretical plates of the date pits packed column were determined from the chromatograms. Complete retention and recovery of UO 2 2+ spiked to wastewater samples by the date pits packed column was successfully achieved. The capacity of the used sorbent towards retention of uranium (VI) from aqueous solutions was much better than the most common sorbents.