Release of Silicon and Aluminum from Montmorillonite Surfaces in Aqueous Systems

The release of silicon and aluminum from purified Na-montmorillonite surfaces in aqueous systems was investigated in dependence of pH at 25 °C. This study has shown that the dissolution of montmorillonite solid involves several parallel and sequential physico-chemical processes. The initial fast exchange of surface cations by hydrogen ions is followed by the release of aluminum and silicon. The dissolution rate of Si is higher than that of Al and influenced by the relative ratios of basal siloxane and edge surfaces. It is quantitatively described by the dissolution rate constants depending on pH. These results are in agreement with the heterogeneity of montmorillonite surfaces and the dominant presence of the siloxane basal surface. The shift of pH to more basic values by the ion exchange processes, and the hydrolysis of dissolved species, induces the formation of secondary amorphous solids, which may serve as precursors for the formation of amorphous aluminosilicates

INTERACTIONS AT INORGANIC/ORGANIC INTERFACES - FROM BIOMINERALIZATION TO HARD TISSUE IMPLANT MATERIALS

Osnova većine prirodnih procesa taloženja jesu međudjelovanja na međupovršini organsko/anorgansko. Kosti i bubrežni kamenci su dvije vrste tkiva koja privlače veliku pažnju zbog medicinskih problema vezanih uz njih. U ovom radu, kroz prikaz istraživanja međudjelovanja organskih molekula s kristalima kalcijevih fosfata u našoj grupi, pokazat ćemo kako se spoznaje dobivene i opisane u istraživanjima pojednostavljenih modelnih sustava mogu primijeniti na osmišljavanje i priptavu novih biomimetičkih presvlaka za metalne implante.Interactions at organic/inoiganic interfaces underly many natural precipitation processes. Bones and urinary stones are two types of mineralized tissue in human organism that attract special attention due to the medical problems connected with them. In this paper, through the review of the investigations of interactions between organic additives and calcium phosphate crystalls performed in our group, it is shown how results obtained in these model systems can be applied in design and preparation of novel biomimetic coatings for bone metal implants

Interactions at inorganic/organic interfaces - from biomineralization to hard tissue implant materials

Osnova većine prirodnih procesa taloženja jesu međudjelovanja na međupovršini organsko/anorgansko. Kosti i bubrežni kamenci su dvije vrste tkiva koja privlače veliku pažnju zbog medicinskih problema vezanih uz njih. U ovom radu, kroz prikaz istraživanja međudjelovanja organskih molekula s kristalima kalcijevih fosfata u našoj grupi, pokazat ćemo kako se spoznaje dobivene i opisane u istraživanjima pojednostavljenih modelnih sustava mogu primijeniti na osmišljavanje i priptavu novih biomimetičkih presvlaka za metalne implante.Interactions at organic/inoiganic interfaces underly many natural precipitation processes. Bones and urinary stones are two types of mineralized tissue in human organism that attract special attention due to the medical problems connected with them. In this paper, through the review of the investigations of interactions between organic additives and calcium phosphate crystalls performed in our group, it is shown how results obtained in these model systems can be applied in design and preparation of novel biomimetic coatings for bone metal implants

Interactions of Sodium Dodecylbenzenesulfonate and Calcite in 0.55 M NaCl Solution

Complex mutual interactions of calcite and sodium dodecylbenzene sulfonate (NaDBS) were studied in 0.55 M NaCl solution, using several complementary techniques. Adsorption of NaDBS on calcite could be resolved from other processes such as adsorption onto the reaction vessel and/or formation of solid crystalline phase, when a special a.c. voltammetric procedure was used below the critical micelle concentration (c.m.c. = = 9 x 10-5 mol/L). A two-plateau type isotherm was obtained. Initial adsorption of NaDBS occurs at Ca2+ ions on the calcite/solution interface through electrostatic interactions. The second stage of adsorption was described as hydrophobic interaction between hydrocarbon chains from bulk solution and those electrostatically adsorbed on calcite, forming surface aggregates. The results of adsorption were analyzed by a two-step adsorption model. The equilibrium constants and &2 for the first and second adsorption step, the surface aggregation number, re, the amount of adsorbed monomer, the saturated adsorption, rm and the standard free energy of surface aggregate formation for one mole of surfactant, AG^m, were calculated