A new glance at ruthenium sorption mechanism on hydroxy, carbonate, and fluor apatites: Analytical and structural studies

Insight into the nature of active redox sites in Ru-containing hydroxyapatite by DRIFT spectroscopy

“…The EXAFS study indicated that the first shell surrounding ruthenium on RuHAp consists of two hydroxy ligands and four oxygen atoms bound to two phosphorus atoms. Recently, Tonsuaadu et al concluded from EXAFS measurements that the Ru 3+ ions are surrounded by six oxygen atoms and chlorine is not present in the first two shells surrounding the Ru 3+ ions [13]; this interpretation is in line with our results.…”

“…A widely used representative is rutheniumhydroxyapatite (RuHAp), which can be prepared by immersion of HAp in an aqueous RuCl 3 solution (soaking) under ambient conditions [9]. RuHAp is a highly selective catalyst for the partial oxidation of alcohols [9][10][11][12][13], amines [14], and organosilanes [15] using molecular oxygen as the sole oxidant. The catalytic material is also effective in Diels-Alder and aldol reactions [16], as well as in the racemization of configurationally stable chiral secondary alcohols [17].…”

Sorption of tartrate ions to lanthanum (III)-modified calcium fluor- and hydroxyapatite

“…Previous studies on Ru-modified apatites [13] have demonstrated that (i) Ru 3+ ions do not exchange Ca 2+ and (ii) they are mainly located in a new amorphous or crystalline phase (depending on the starting apatite). Taking this into consideration, the Hydroxy-and fluorapatites were synthesized using a standard procedure according to previous work [24].…”

“…The binding of metal ions with apatite in aqueous solutions is mainly explained by ion-exchange reactions [9,10]. Moreover, the binding of three valent cations due to the precipitation of their phosphates (LaPO 4 , AlPO 4 ) [11], the binding of hydro-complexes (Ru, Cr) [12][13][14], and an introduction into the apatite structure by compensation with mono-valent cations take place [11].…”

“…Ru 3+ -containing hydroxyapatites have been found to be effective and selective catalysts for oxidative reactions [12,13,15,16]. In comparison with other supported Ru-catalysts, these modified apatites present several advantages, e.g., a simple usage, no leaching of Ru ions, and an easy recovery of the catalyst by filtration after the reaction.…”