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The mechanism of dissolution of hydroxyapatite and carbonated apatite in acidic solutions

1988; Elsevier BV; Volume: 91; Issue: 4 Linguagem: Inglês

10.1016/0022-0248(88)90116-9

1873-5002

Jerzy Budz, George H. Nancollas,

Thermal and Kinetic Analysis

As potential models for biological minerals, the dissolution of hydroxyapatite (HAP) and carbonated apatite (CAP) has been extensively studied. In the present work, the constant composition method has been used to investigate these dissolution reactions at constant undersaturation. The rates of dissolution of both HAP and CAP show marked decreases as the reactions proceed despite the constancy of undersaturation. In order to examine the influence of trace impurities, both ultrapure and reagent grade chemicals have been used together with traces of methanehydroxydiphosphonate (MHDP) as an “impurity probe”. Interestingly, MHDP accelerated the reaction at very low concentration (∼5×10-7M) but reduced the rate at higher levels. The results have been analyzed in terms of a polynuclear dissolution mechanism with surface properties expressed in terms of free surface energy which in turn is related to a surface entropy factor characterising the micro-roughness.