The Influence of Carbonate Ions on the Structure of the Electrical Double Layer at the Interface of Hydroxyapatite/Electrolyte Solution

The aim of the work was to investigate the changes in the double electrical layer at the hydroxyapatite containing different amount of carbonate ions/electrolyte solution. Besides, the main properties of the edl (electrical double layer), i.e. surface charge density and zeta potential were determined by electrophoresis measurements and potentiometer titration, respectively. The synthesized adsorbents were characterized by the following methods: X-ray diffraction, FTIR (Fourier Transform Infrared Spectroscopy), adsorption and desorption of nitrogen and scanning electron microscopy. The analyzed samples had different structures and particle sizes. It was proved that increase in the carbonate groups content is connected with the decrease of apatite grain sizes and crystallinity reduction. The characteristic parameters of the electric double layer were also different: pHpzc (point zero of charge) of hydroxyapatite was 6.5 whereas for carbonate apatite was higher – pHpzc = 8. In both cases determination of precise pHIEP (isoelectric point) was not possible but it is known that its value is lower than 4

Influence of the Modifier Type and its Concentration on Electroosmotic Flow of the Mobile Phase in Pressurized Planar Electrochromatography

The aim of this work was to find a relationship between electroosmotic flow (EOF) velocity of the mobile phase in pressurized planar electrochromatography (PPEC) and physicochemical properties like zeta potential, dielectric constant, and viscosity of the mobile phase as well as its composition. The study included different types of organic modifiers (acetonitrile, methanol, ethanol, acetone, formamide, N-methylformamide and N,N-dimethylformamide) in the full concentration range. In all experiments, chromatographic glass plates HPTLC RP-18 W from Merck (Darmstadt) were used as a stationary phase. During the study we found that there is no linear correlation between EOF velocity of the mobile phase and single variables such as zeta potential or dielectric constant or viscosity. However, there is quite strong linear correlation between EOF velocity of the mobile phase and variable obtained by multiplying zeta potential of the stationary phase–mobile phase interface, by dielectric constant of the mobile phase solution and dividing by viscosity of the mobile phase. Therefore, it could be concluded that the PPEC system fulfilled the Helmholtz–Smoluchowski equation

Adsorption of the Tartrate Ions in the Hydroxyapatite/Aqueous Solution of NaCl System

The research on the interaction of tartrate ions with the surface of hydroskyapatite was presented, including the measurements of the kinetics of tartrate ion adsorption and tartrate ion adsorption as a function of pH. The adsorption of tartrate ions was calculated from the loss of tartrate concentration in the solution as measured by a radioisotope method using C-14 labeled tartaric acid. In order to explain the mechanism of interaction of tartrate ions with hydroxyapatite, supplementary measurements were carried out, i.e., potentiometric measurements of the balance of released/consumed ions in the hydroxyapatite/electrolyte solution system, zeta potential measurements, FTIR spectrophotometric measurements and the hydroxyapatite crystal structure and particle size distribution were characterized. It was found that the adsorption of tartrate ions occurs as a result of the exchange of these ions with hydroxyl, phosphate and carbonate ions. Replacing the ions with the abovementioned tartrate ions leads to the appearance of a negative charge on the surface of the hydroxapatite. On the basis of XRD study and particle size distribution, a decrease in the size of crystallites and the diameter of hydroxyapatite particles in contact with a solution of 0.001 mol/dm3 of tartaric acid was found

Adsorption of divalent cations at the hydroxyapatite/electrolyte solution interface

Functional and composite materials obtained from hydroxyapatite (HAp) are widely used in practice, which results in intensive research of systems containing hydroxyapatite. Doping with divalent ions of hydroxyapatite changes its properties, thus extending its application in material science. Substitution of calcium ions in the surface layer of hydroxyapatite by metal cations is used in the development of new catalysts, sorbents, sensors and materials for other applications. The doping of the surface of the hydroxyapatite with divalent ions may occur as a result of adsorption of metal cations on the surface groups and calcium exchange in the crystal structure of the hydroxyapatite. The paper presents the mechanisms of adsorption of selected bivalent ions Ba2+, Cd2+, Co2+, Fe2+, Sr2+, Zn2+ on hydroxyapatite. The influence of cation adsorption on unit cell parameters, crystallite size and particle size distribution is discussed

Research on deposition of silver nanoparticles at the cellulose/NaNO3 electrolyte interface

Currently the research on silver nanoparticles is of great demand owing to their antibacterial properties. One of the possibilities is the study of the silver deposition on the cellulose fibers, and more specifically of the silver nanoparticles and cellulose particles. The research was aimed at obtaining silver nanostructures by reducing ions with formaldehyde and then stabilizing them with the Pluronic solution. A suspension system containing cellulose fibers and silver nanoparticles was prepared in the basic electrolyte NaNO3. There were analyzed the following makes: pH of solutions, grain distribution and zeta potential ζ. Ag nanoparticles are largely applied in medicine, pharmacy, cosmetology and textile industry. Great interest in the nanostructures allows for developing knowledge about them, and thus creating the possibility of further improvement of their properties for subsequent applications