The maximum uptake of cadmium ions from aqueous solution by sorption on calcium hydroxyapatite was measured in different experimental conditions. A 'slow introduction process' leads to a larger uptake than for standard batch experiments. The main differences are: a larger incorporation of Cd in the crystal framework of apatite through a substitution -diffusion process, a different distribution among Ca(1) and Ca(2) sites and a lower concentration gradient. For the larger Cd concentration, a dissolution -precipitation also appears. leading to the formation of cadmium hydrogenophosphate, but the formation of this solid phase remains a minor process, The results also confirmed that sorption of cadmium ions on calcium hydroxyapatites does not achieve equilibrium in standard experimental laboratory time intervals. The higher achieved uptake is particularly attractive for the practical use of apatites in the decontamination of solutions polluted by cadmium.