PubMed · 5965573
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B H Brady, D H Napper, B M Smythe. 1966-10-01. Dissolution kinetics of hydroxyapatite.. https://doi.org/10.1038/212077a0
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The capacity of hydroxyapatite (HAp) to remove lead from aqueous solution was investigated under different conditions, namely initial metal ion concentration and reaction time. The sorption of lead from solutions containing initial concentrations from 0 to 8000 mg/L was studied for three different HAp powders. Soluble Pb and Ca monitoring during the experiment allows characterizing the mechanism of lead uptake. Dissolution of calcium is followed by the formation of a solid solution, Pb(x)Ca(10-x)(PO4)6(OH)2, with a Ca/P ratio decreasing continuously. Langmuir-Freundlich classical adsorption isotherms modeled adsorption data. The adsorption capacities calculated from this equation vary from 330 to 450 mg Pb/g HAp for the different solids. Modeling of the sorption process allows to determine theoretical saturation times and residual lead concentrations at equilibrium.
This work reports on the effect of the amount (0, 10, and 30 wt %) and type of HA powder incorporated into an acrylic bone cement on the tensile properties, compression properties, and fracture toughness. The three different types of HA powders used were synthesized in the laboratory and coated with a silane agent prior to incorporation into the cement powder, and differed in particle size, water content, surface area, and crystallinity. It was found that the inclusion of any type of HA powder led to an increase in the tensile modulus (ET), but all the other mechanical properties of the cement decreased (relative to the values of the unfilled cement). The increase in ET is attributed to the good adhesion between the filler and the cement matrix, which is due to the silane coating agent. The decrease in the other mechanical properties may be a consequence of HA powder agglomeration and porosity. Hydroxyapatite morphology and crack-growth mechanisms were analyzed by scanning electronic microscopy (SEM).
Hydroxyapatite (OHAp) has been obtained by using a precipitation method. Thermal stability of the precipitated powder has been checked to define an appropriate working range to process ceramic bodies without the appearance of odd phases. Pellets of hydroxyapatite have been manufactured by means of uniaxial pressing and convenient thermal treatments have been investigated to achieve high density OHAp bodies. Finally, factors that could affect the ultimate mechanical properties of the sintered bodies prepared by uniaxial pressing have been discussed.