Authors’ response to comments on “Factors influencing the removal of divalent cations by hydroxyapatite”

Comments on the authors’ response to the comments on “Factors influencing the removal of divalent cations by hydroxyapatite”, by Smiciklas et al.

“…I believe that an authors' response should be a scientific contribution. The authors' response [1] also contains similar mistakes given in their article [3]. Avoiding discussion on all points, I just focus on the main issues.…”

“…I appreciate the effort made by Smičiklas et al [1] to respond to my comments [2] on their article "Factor influencing the removal of divalent cations by hydroxyapatite" [3]. However, for me, this is not an authors' response but rather a rebuttal indicating their misunderstanding of the problem.…”

“…Responding to my comment that the sorption isotherms, for all investigated ions, are not given for a constant equilibrium pH, the authors [1] cited 25 articles in which batch sorption experiments were conducted in different ways concerning pH determination. In 16 articles final pH values were measured, while in 9 articles neither pH values were mentioned nor final (equilibrium) pH values measured.…”

“…In authors' response, Smičiklas et al [1] wrote, "By keeping constant pH along cation sorption, the sorbent/(sorbate solution) system is artificially maintained under forced conditions. Since the purpose of our experiments is to evaluate certain sorbent as a metal removing agent, these conditions will not be realistic if the sorbent is applied on actual contaminated water, where maintaining constant pH is not reasonable or not possible at all".…”

“…Further, it stays in authors' response [1] that "Addition of acidic or alkaline solutions can often change the volume, composition and consequently concentration of the solution". To investigate the sorption process as a function of various equilibrium pH's it is necessary to add an amount of acid or alkali into the investigated suspension/dispersion.…”