The role of intraparticle diffusion in the sorption of Cu2+ ions onto hydroxyapatite

The Cu2+ sorption onto HAP was investigated as a function of time, in the concentration range 5·10-4 - 5·10-3 mol/dm3. The experimentally obtained kinetic data were fitted with the intraparticle diffusion model. The correlation coefficients were low considering the overall reaction period. However, q versus t0.5 plots could be divided into three segments, out of which the second linear segment can be attributed to the intraparticle diffusion. Intraparticle diffusion rate constants (ki) increased from 3.57·10-3 to 7.80·10-3 mmol/g min0.5 with the increase of the initial Cu2+ concentration. As the lines did not pass through the origin it was concluded that intrapaticle diffusion is not the only rate-controlling step.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200