Effective separation of uranium from mine process effluents using chitosan as a recyclable natural adsorbent

This study aimed to efficiently and cost-effectively recover uranium from real mine effluents derived from the processing of uranium-bearing ore. A natural bioactive polymer, chitosan, was applied as a low-cost material to separate uranium ions and characterised using a scanning electron microscope coupled with an energy dispersive spectrometer, and a Fourier transform infrared spectroscopy analysis. Rapid adsorption (over 90% within 10 min) was recorded in the examined batch-type system. The kinetics of the reactions were calculated, and the rate of uranium adsorption tended to follow a second-order equation. The maximum adsorption capacities of the biopolymer given by the Langmuir model were 17.44 mg/g and 7.51 mg/g for the flotation and Knelson tailings water, respectively. The results demonstrated that the separation of uranium ions from effluents was temperature- and pH-dependent. Studies have revealed an enhancement in uranium uptake at elevated water temperatures. As the pH increased from 2 to 10, the net charge on the biopolymer surface changed from positive to negative, which indicated the possible involvement of electrostatic interactions in the binding of the metal ions. In addition, interactions between uranyl ions and biopolymer functional groups were confirmed. The regeneration possibility and reusability of the biopolymer were investigated, and approximately 73% of the uranium was recovered by the fourth adsorption–desorption cycle.