The kinetics of exchange of thorium and uranyl ions on Al‐13‐phosphatoantimonic acid (Al‐13‐PAA) was studied in nitrate solution at pH 1. The investigations were carried out under particle diffusion mechanism and the limited batch technique. The effects of particle size, concentration, and temperature have been studied. The effective diffusion coefficient, activation energy, and entropy of activation have been evaluated. The exchange capacity was evaluated and found to be 0.9 and 0.7 meq g−1 for uranyl and thorium ions respectively.