Comparative study of fabricated composites based on phosphogypsum and Al-hydroxide for uranium separation from aqueous and waste solutions

Abstract

ABSTRACT The using of phosphogypsum (known as a waste by-product of phosphoric acid production) with cheap compound alumina afforded environmental and economic aspects, as well as targeted production of promising adsorbents for uranium adsorption. Three fabricated composites based on phosphogypsum and Al-hydroxide were thermally synthesised to adsorb uranium from aqueous and wastes solution. The first one (PGA) was synthesised by mixing phosphogypsum, aluminium chloride and caustic soda at 800°C. Also, the other two composites are prepared by mixing of phosphogypsum with sodium molybdate or zirconium oxychloride to synthesis PAM and PAZ, respectively. We conducted several batches to determine the factors affecting the adsorption of uranium, including pH, initial uranium concentration, adsorbent weight, equilibrium time and interfering ions. The adsorption isotherm models were satisfactory to fit with Langmuir isotherm, exhibiting theoretical adsorption capacities of 400, 454 and 477 mg/g for composites PGA, PAM and PAZ, respectively. The adsorption studies of U in the presence of some possible interfering elements have been discussed. Elution of uranium has been achieved and optimised using 2 N of hydrochloric acid. The adsorption of uranium on the composites compatible with pseudo-second-order model, but the liquid film diffusion model and the intraparticles diffusion model were not the only limiting step.