Kinetics and Thermodynamics of Cr(VI) Adsorption on Functionalized Polymeric Resin

Abstract Hexavalent chromium (Cr(VI)) in wastewater poses severe environmental and ecological risks. In this study, amide‐ and amidoxime‐functionalized polymers were synthesized via suspension polymerization, followed by amidation and hydroxylamine modification, for efficient Cr(VI) removal from simulated wastewater. The polymers were characterized using EDX, SEM, FTIR spectroscopy, solid‐state 13 C NMR spectroscopy, and BET analysis. Batch adsorption studies assessed the effects of initial Cr(VI) concentration, adsorbent dose, pH, temperature, and counter ions. Adsorption performance was influenced by pH, solid‐to‐liquid ratio, and Cr(VI) concentration. At pH 2, 4, 6, 8, and 10, Cr(VI) removal efficiencies of AN‐DMAPA polymer were 97.70%, 97.45%, 96.80%, 94.50%, and 90.15%, respectively, while those for AN‐amidoxime polymer were 86.50%, 83.20%, 70.00%, 58.22%, and 54.12%, respectively. Both polymers exhibited excellent regeneration capabilities, with efficiencies exceeding 92% (AN‐DMAPA) and 80% (AN‐Amidoxime) after three adsorption‐desorption cycles. Adsorption followed the Langmuir isotherm and pseudo‐second‐order kinetic models. Dynamic testing, including Cr(VI) breakthrough curve analysis, confirmed the polymer's effectiveness. Additionally, a 5% sodium chloride solution was employed to effectively recover the extracted Cr(VI) quantitatively. These results demonstrate the significant potential of AN‐DMAPA and AN‐amidoxime polymers for environmental remediation, providing an efficient solution for Cr(VI) removal from wastewater and addressing critical environmental challenges.