Hydroxy- and fluorapatite as sorbents in Cd(II)–Zn(II) multi-component solutions in the absence/presence of EDTA

Carboxylate-modified apatite adsorbents for detection of Zn(II) ions

“…These values are significantly smaller than the equilibrium pHs obtained for the corresponding powder suspensions without Zn 2+ or with unmodified HAp in the presence of Zn 2+ (pH 6.3). In agreement with previous reports [19,20], the observed decrease in equilibrium pH can be attributed to the strong affinity of the adsorbent surface against Zn 2+ ions, leading to Zn 2+ complexation on carboxylate-modified apatite surface, and hence releasing of protons into solution. This process is more evident with a-HAp and c-HAp compared to other adsorbents which are related to the number and chain length of -COOH functions, but they are present in a larger amount in the a-HAp case.…”

Calcium, Barium and Strontium apatites: A new generation of catalysts in the Biginelli reaction

“…This approach does not exclude catalysis by Lewis acids that were not incorporated into the apatite structure. In our case nonincorporated metal salts were washed out with water and the only metal ions present were those in the apatite structure [46,47]. Although metal-modified apatites had higher catalytic activity than nonmodified hydroxyapatite the reaction rate remained slow.…”

Adsorption of Zn2+ from aqueous solutions by si‐substituted carbonated hydroxylapatite: Equilibrium, kinetics, and mechanisms

“…To ensure whether the adsorption process is physical or chemical, D-R isotherm [25] is introduced according to the following Eqs. (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14):…”