Utilizing of heavy metal ions adsorption by new urea-based-polyvinyl chloride solid support: equilibrium and thermodynamic characteristics

A new urea-modified polyvinyl chloride composite (PVC-urea) has been strategically synthesized and rigorously characterized as a prospective sorbent for the efficient extraction of uranyl ions from solutions. Comprehensive spectroscopic and analytical techniques, including FT-IR, 1H-NMR, SEM-EDX, 13C-NMR, TGA, and GC/MS, have been employed to confirm the successful fabrication and structural integrity of the PVC-urea composite. The adsorption performance of the synthesized material has been meticulously optimized by systematically investigating the influence of key operational strictures, likes, pH, initial uranyl ion concentration, contacting time, adsorbent dosage, and competing ions, temperature, and the efficacy of various eluting agents. Under optimized conditions (25 °C, pH 4.5, 10 minute agitation, and an initial uranyl ion concentration of 0.63×10-3 mol/L), the PVC-urea composite demonstrated a maximum uranyl ion uptake ability of 25 mg/g. Adsorption isotherm analysis revealed a superior fit to the Langmuir modelling reviewed to the Freundlich modelling, with a theoretical extreme adsorption capacity of 24.1 mg/g, closely aligning with the experimentally determined value. Kinetic judges indicated that the adsorption manner is well-described by a mixed pseudo-first order and pseudo-second order model, yielding theoretical retention capacities of 25.35 mg/g and 25.31 mg/g, respectively. Thermodynamic analysis suggests that the adsorption process is exothermic (ΔH = -10.62 kJ/mol) and non-spontaneous, as evidenced by positive Gibbs free energy values ranging from 3.43 to 6.1 kJ/mol at 298 to 353 K, with favorable adsorption observed at lower temperatures (ΔS = -0.0472 kJ/mol). Furthermore, quantitative recovery of the adsorbed uranyl ions was achieved with high efficiency (97%) using 0.5 M H2SO4 as an eluting agent, underscoring the economic viability of the process. The PVC-urea composite exhibited notable selectivity towards uranyl ions in the attendance of a range of common co-ions, demonstrating a robust tolerance limit and highlighting its potential for selective uranyl ion extraction in complex environmental matrices.