Acrylamide/ethyl cellulose Schiff base hydrogel for uranium capture from aqueous solutions using response surface...

In this study, a novel acrylamide Schiff base hydrogel was synthesized as an efficient adsorbent for uranium removal from contaminated environments. The hydrogel was characterized using a range of techniques, and its adsorption performance was systematically evaluated through batch experiments that investigated the effects of pH, contact time, initial ion concentration, adsorbent dosage, and temperature. Under optimized conditions, pH 4.0, 120 min, 70 mg adsorbent, 298 K, and 100 mg L^-1 U(VI), a uranyl ion removal efficiency of 99.92 % was achieved. Notably, using a lower adsorbent dose (5 mg) resulted in a maximum adsorption capacity of 148 mg g^-1. Adsorption isotherm and kinetic studies revealed that the data best fit the Langmuir model (R² = 0.98) and pseudo-second-order kinetics (R² = 0.99), indicating a monolayer chemisorption mechanism; the Langmuir model also provided a maximum adsorption capacity of 159.23 mg g^-1. Thermodynamic analysis confirmed that the adsorption process was spontaneous and exothermic. The hydrogel further demonstrated excellent selectivity and resistance to interference from coexisting ions. Optimization using Central Composite Design (CCD) within the framework of Response Surface Methodology (RSM) enabled the development of a predictive polynomial model to assess and optimize the key operational parameters. Finally, the practical applicability of the hydrogel was demonstrated through successful remediation of a real water sample.