Isotherms, kinetics and thermodynamic studies of removal of thorium from aqueous solution by boehmite granules

The performance of boehmite granules in the adsorption of thorium ions from aqueous solution was studied in batch and continuous processes. The effective parameters such as pH and temperature were evaluated. First, the pH value was optimized, and then, several experiments were carried out in the optimized pH value and various temperatures (30, 40 and 55 °C). The equilibrium adsorption data were analyzed using Weber–van Vliet, Fritz–Schlunder and Hill isotherm models to find the best-fit isotherm. Thermodynamic parameters including standard enthalpy change (∆H°), standard entropy change (ΔS°) and standard Gibbs free energy change (∆G°) were determined in the batch mode. The application of adsorbent for thorium removal from aqueous solutions was examined through column breakthrough studies. The effect of various parameters such as inlet concentration, flow rate and bed height on the breakthrough curves was investigated. The maximum column capacity was found to be about 57.78 mg thorium per gram of boehmite. Three widely used models, including Thomas, Adams–Bohart and Bed Depth Service Time (BDST), were used to fit the data obtained from the experiments. The results indicated that the Thomas model could describe the column dynamics in all operating situations. But, the Adams–Bohart model can only estimate the primary section of the breakthrough curves.