Authors' response to comments on 'Factors influencing the removal of divalent cations by hydroxyapatite' Discussion

Recently. it has come to our attention, that a polemical note by Milonjic [S.K. Milonjic, Comments on "factors influencing the removal of divalent cations by hydroxyapatite", J. Hazard. Mater. 162 (2009) 1588-1589]. has been published raising several critical comments on some experimental procedures, as well as the presentation and interpretation of some data found in the cited paper by Smiciklas et al. [L. Smiciklas, A. Onjia. S. Raicevic, Dj. Janackovic, M. Mitric, Factors influencing the removal of divalent cations by hydroxyapatite, J. Hazard. Mater. 152 (2008) 876-884]. Since we have not received any prior copy of this discussion through the process involved in the acceptance of these comments, we now take the opportunity of responding. We have reviewed some scientific papers dealing with cation sorption, in order to demonstrate variety of experimental approaches used for batch sorption tests, regarding solution pH. Finally, we justified experimental methods and data interpretation methods we chose to perform in the mentioned manuscript.