Calcium sorption on hydroxyapatite in aqueous solutions: reversible and nonreversible components

Methodology to obtain exchange properties of the calcite surface—Application to major and trace elements: Ca(II), , and Zn(II)

“…In our concern, the results presented above for both 45 Ca(II) and H 14 CO À 3 suggest that the process observed here is a combination of at least two processes: a first one rapid and reversible stage, finished in few hours, and a second one, with slower kinetics, whose stationary state is not reached in 1 month. Therefore, our purpose in this paper was to quantify the reversible fraction of the global sorption, by using the method proposed by Badillo-Almaraz and Ly [40]. This method was based on isotopic ratios and was presented, at the origin, for the interpretation of the sorption of calcium at the surface of an apatite, the calcium being a structural element of this mineral.…”

“…For more precise information concerning the hypothesis involved in this modeling exercise and the demonstration of the formula, the reader can refer to Ref. [40].…”

“…We used the following equations to calculate distribution coefficients for the sole ''reversible component," called Kd à s and Kd à d for sorption and desorption, respectively (see Badillo-Almaraz and Ly [40], for demonstration),…”

A novel determination of calcite dissolution kinetics in seawater

“…This near-equilibrium (X ¼ 1:07) enrichment could be due to isotopic exchange, or it could be due to actual carbonate dissolution. Solid-solution exchange has been investigated before, and typically models partition the solid into labile and trapped reservoirs of calcium and carbonate groups on the calcite surface (Badillo-Almaraz and Ly, 2003;Tertre et al, 2010). Using radiolabeled calcium and bicarbonate, Tertre et al (2010) showed immediate (minutes to hours) exchange of the labile solid surface with the solution; after this initial equilibrium was reached, the solid The data from (a) converted to the moles of labeled carbonate dissolved based on Eq.…”

Goldschmidt Abstracts 2007- L

“…Moreover, Kd's calculated with desorption experimental data are systematically higher than those calculated with the sorption ones. In order to test the occurence of a first reversible ion exchange step, we applied the approach of Badillo-Almaraz and Ly (2003) put forward for the interpretation of Ca sorption onto hydroxyapatite. More specifically, on the basis of isotopic equilibrium principle and from the knowledge of the isotopic ratios ( 45 Ca/Ca tot ), it is possible to calculate "reversible" Kd's of 45 Ca for both sorption and desorption steps.…”