Removal of radioactive elements from aqueous solutions by adsorption onto polyacrylamide–expanded perlite: Equilibrium, kinetic, and thermodynamic study

In this research, a novel composite, poly(acrylamide-expanded perlite) [P(AAm–EP)], was synthesized and its adsorptive features were investigated for UO22 + and Th4 + ions. The composite's adsorptive features were evaluated for UO22 + and Th4 + ions in light of the dependency of the ion concentration, pH, temperature, time, and reusability. The composite could bind UO22 + and Th4 + ions with strong chemical affinity. The correlation coefficients indicate that the Langmuir model fits better for the UO22 + and Th4 + onto P(AAm–EP) composite with adsorption capacities as 0.66 and 0.74 mol kg− 1, respectively. Adsorption equilibrium of UO22 + and Th4 + ions was achieved in about 34 and 32 min, respectively. The kinetic data conformed better to the pseudo-second order equation. The adsorption of UO22 + and Th4 + ions increased with increasing pH and reached a plateau value at around pH 3.0. Thermodynamic parameters ΔH and ΔS values showed that the sorption process was spontaneous (ΔG < 0), endothermic (ΔH > 0), and had increased entropy (ΔS > 0). It was also found that the adsorption kinetics followed the pseudo-second-order model and that the rate-controlling step was chemical adsorption. The reusability of the composites was confirmed for 5 sequential reuses.

► Adsorption capacities (XL) of uranium and thorium ions were found to be 0.66 and 0.77 mol kg− 1.
► Adsorption data for uranium and thorium ions were well fitted by the Langmuir and D–R isotherms.
► Kinetic data corresponds well to the second order equation.
► Uranium and thorium ion adsorption onto P(AAm–EP) composite is an endothermic and spontaneous process.
► The composite is reused up to 5 times with no loss of removal efficiency.