Kinetic studies on Al3+ removal from phosphoric acid by cation exchange resin

Abstract An investigation on the removal of aluminum ions from phosphoric acid by ion exchange resin (001 × 7)732 was carried out for optimizing the wet process of phosphoric acid (WPA). Various parameters such as contact time, temperature, ratio between resin and solution, and agitation speed were studied to evaluate their effects on the ion exchange equilibrium and optimizing the process conditions. The experimental conditions of temperature 40 °C, contact time 20 min, ratio between resin and solution 50 g/200 g, and agitation speed 500 rpm could get the best sorption capacity at 6.62 × 10 −3 g/g and removal efficiency at 49.8 %. Empirical kinetic equations such as pseudo‐first‐order and pseudo‐second‐order kinetic equations, and broadly applicable diffusion models such as film diffusion, pore diffusion, and moving boundary process were employed to process the dates. Results showed the ion exchange process followed the pseudo‐second‐order model. In addition, the rate limiting steps in the ion exchange reaction were both of film and particle diffusion. The activation energy (10.77 KJ/mol) also indicated a diffusion controlled process. Furthermore scanning electron microscopy (SEM) coupled with X‐ray energy dispersed spectrometer and FTIR analyses for the resin before and after aluminum adsorption, demonstrated that aluminum containing nodules existed in the interior of the resin, the functional group is −SO 3 − .