Kinetics, equilibrium, and thermodynamics investigation on the sorption of gadolinium by synthetic polymers

The adsorption behaviour of gadolinium on grafted co-polymers was evaluated. Batch tests, such as effects of adsorbent weight, shaking times at various temperatures, and initial gadolinium (III) concentration, were used to evaluate the adsorption behaviour. The best results were obtained using 5.5 pH and 400 mg/L of gadolinium as an initial concentration. According to the experimental data, the adsorption capacities of prepared polymers have been improved by addition of silica (powder and gel form). The capacity of the (poly acrylamide-acrylic acid-sodium styrene sulphonate) is 129.36 mg/g which improved to 158.48 and 168.07 for (poly acrylamide-acrylic acid- sodium styrene sulphonate-silica powder) and (poly acrylamide-acrylic acid- sodium styrene sulphonate-silica gel), respectively. The polymer (poly(sodium styrene sulphonate)-(silica gel)–acrylic acid-polyacrylamide) [P-SG] has a high adsorption capacity and the adsorption statistics are more closely related to the Langmuir model. Monolayer capacities of the three prepared polymers are 133.33, 184.8 and 206.61 mg/g. The rate of gadolinium removal improved as the temperature rose, indicating that the sorption process is endothermic. The results of experiments were matched using pseudo-second order based on the kinetics model evaluated results. The mechanism may be chemically sorption.