The Electrical Double Layer at the Hydroxyapatite/NaClO4 Solution Interface

Physicochemical properties of hydroxyapatite [Ca10(OH)2(PO4)6] samples surface were studied and physicochemical quantities characterizing the electrical double layer of the hydroxyapatite/NaClO4 solution interface were determined. The investigated samples were synthesized by two methods. Hydroxyapatite (HAP) was investigated using X-ray diffraction (XRD), X-ray fluorescence (XRF), adsorption-desorption of nitrogen (ASAP), photon correlation spectroscopy (PCS), infrared spectroscopy (IR), and AFM microscope. The surface area, the average volume of pores and the size of particles of hydroxyapatite of the samples were determined. The surface charge density and the potential were studied as a function of pH and the point of zero charge and the isoelectirc point of samples were determined. On the basis of potentiometric titrations the values of surface ionization and complexation constants were calculated.