Assessment of the adsorption of thorium onto styrene–divinylbenzene-based resin: Optimization using central composite design and thermodynamic parameters

Adsorption of thorium on styrene–divinylbenzene-based resin was investigated to obtain the optimum adsorption conditions by using the central composite design (CCD) method. This study was performed in 30 runs of experiments as a function of pH, thorium concentration, contact time and temperature. Adsorption performance of styrene–divinylbenzene-based resin was higher than 98%. The optimum adsorption of thorium using styrene–divinylbenzene-based resin can be successfully predicted statistically by the CCD method. In addition, sorption isotherm models such as Langmuir, Freundlich and Dubinin–Radushkevich were applied, and adsorption of Th(IV) was described most precisely by the Langmuir isotherm, which has the highest R2 (0.99) value. Thermodynamic parameters showed that the adsorption is an exothermic and spontaneous physical process. The results of this study reveal that this type of synthetic resin can be used as an effective sorbent material for the removal of Th(IV) ions from weakly aqueous solutions in remediation and nuclear wastewater treatment. © 2017 Institution of Chemical Engineer

Assessment of reaction between thorium and polyelectrolyte nano-thin film using Box–Behnken design

Sandwich type polyelectrolyte nano-thin films (PENTFs) were prepared by using polyallylamine hydrochloride and polyacrylic acid from layer-by-layer assembly process with spin coating system. Their nanostructures have been studied by scanning electron microscope, atomic force microscope, and attenuated total reflectance Fourier transform infrared spectroscopy. In order to understand the effects of the initial concentration of thorium, initial solution pH, temperature, and contact time on the reaction between thorium and PENTF, an experiment data set was designed according to Box–Behnken model. The analysis of variance calculations for regression model were carried out in 95% confidence level and were checked for fitting experimental data and predicted values. The correlation coefficient value (R2) obtained as 94% showed that there was a correlation between the predicted and the observed values. The optimum pH, temperature, initial concentration of thorium, and interaction time in studied ranges were found as 2.81, 35?, 160 mg·L-1, and 120 min, respectively. At these conditions thorium (IV) ions adsorption yield was obtained as 89 ± 2%. The Freundlich, Langmuir, and Dubinin–Radushkevich isotherms were used to investigate the characteristics of the process. These characteristics data imply that the Freundlich model fits better than the Langmuir model for the Th (IV) sorption onto PENTFs with KF and n values were found to be 20.6 mg·g-1 and 1.08 L·mg-1, respectively. The thermodynamic parameters were also computed as negative ?H value suggest that adsorption of Th (IV) is exothermic nature. The calculated negative and positive values of ?G indicate that the sorption process is favorable (energetically) while running below 40? and over this point the process status change to non-spontaneous, respectively. © 2017, © The Author(s) 2017