Physicochemical regularities of the sorption of amino acids on the surface of brushite

Abstract

Calcium phosphates are part of biogenicand pathogenic mineral formations. Brushite occurs mainly in conjunction with other calcium phosphates in the composition of pathogenic mineral formations in the body of animals and humans. There are a number of assumptions, according to which the basis of the processes of mineralization is the adsorption interaction of free amino acids and associated protein molecules with inorganic components of biological liquids. However, the mechanism of their interaction is not fully understood. In this paper the adsorption of amino acids was studied on the surface of brushite. Brushite was synthesized in the system of Ca(NO3)2:(NН4)2HPO4 with equal concentrations. According to the results of XRD and IR spectroscopy it was established that precipitation was represented by the phase of brushite. It was implemented dynamic dissolution of the solid phase of brushite when the pH was varying. Equations of the kinetic graphs were obtained. It was investigated the adsorption of amino acids in a wide range of variation in their concentrations and the pH of the solution. It was considered the effect of pH on the maximum adsorption of amino acids on brushite. The results of IR spectroscopy confirmed adsorption. The solid phase of brushite was determined by the sign of the surface charge. The values of the sign of the surface charge of brushite were found to be positive. The values of the Gibbs free energy were calculated. There was revealed that the interaction of amino acids with the surface of the brushite was characterized by physical adsorption.