Investigation of the adsorption behavior of uranium ion from aqueous solution on the impregnated XAD-4 resin with acidic complexing agent

One of the most important persistent and non-degradable pollutants are heavy metals, which are among the most toxic pollutants in the environment. Therefore, removing these pollutants is of particular importance. Uranium, as one of the heavy metals, is a natural radionuclide that has harmful effects on human health and the environment due to its serious toxicity and radiation properties. In this research, Amberlite XAD-4 resin impregnated with bis-2-hydroxybenzaldehyde 1,2-diaminoethane (H2L) Schiff base ligand was used for the adsorption of uranium from aqueous solution. The effect of effective parameters such as aqueous phase pH, contact time, amount of adsorbent and temperature dependence of the process were investigated. The results showed that 98% of uranium ions in the optimal conditions of pH5.5, adsorbent amount 0.1 g, contact time 60 min. and temperature 25˚C, uranium ion with an initial concentration of 20 mg/L was quantitatively removed from 20 mL of the aqueous solution. A comparing the adsorption percentage of non-impregnated resin with impregnated resin with Schiff base ligand shows a shift for uptake of the uranium ions vs. pH curves towards lower pH the values (about ΔpH0.51) and the adsorption behavior of the resin at pH5.5 improves with increasing adsorption from 52% to 98%. Kinetic and adsorption data correspond well with pseudo-second-order equation and Freundlich isotherm, respectively. Thermodynamic investigation also showed that the studied ion adsorption process is based on entropy.