Ion exchange properties of strontium on in situ precipitated polyantimonic acid in amberlite XAD-7

Polyantimonic acid was precipitated in the pores of Amberlite XAD-7 (PAA-XAD) and studied for the ion exchange of strontium as a function of various parameters, such as time, strontium ion concentration and temperature. Nearly 30% of the Sb2O5 was impregnated into XAD-7 exhibiting an experimental capacity of 23 mg/g of strontium. Distribution coefficient of strontium on PAA-XAD was found to be 6069 mL/g at 0.1 mol/L nitric acid and it decreased with increase in the concentration of nitric acid. Rapid uptake in the initial stages of equilibration was observed followed by sluggish rate of exchange and the ion exchange reaction was found to follow the second order rate equation. The rate constant and energy of activation for such reaction were found to be 8.4 × 10−3 L mg-1 min-1 at 300 K and 79 kJ/mol, respectively. The data obtained in this study were fitted into Langmuir adsorption model and Langmuir constants obtained at various temperatures were utilized for estimating the enthalpy change (ΔHo) accompanied by the ion exchange. The performance of the sorbent under dynamic conditions was evaluated by following a breakthrough curve using simulated waste solutions.