Jerzy Szczypa

Estimation of surface ionization constants from electrokinetic data

A modified double extrapolation technique of surface ionization constants estimation from electrokinetic data for oxides is described. The pKa1int and pKa2int constants determined by the above method for SiO2, Al2O3, TiO2, and FeOOH are compared with those determined by double extrapolation technique using potentiometric titration data.

Effect of n-alcohols on the potentiometric titrations of rutile

Abstract The effect of composition of mixed solvent (aqueous ethanol or 1-butanol) on the potentiometric titrations of rutile suspensions in 0.1, 0.01, and 0.001 M NaCl is studied. The value of limc→0(− d ln σ0/dc)pH,I, where σ0 is the surface charge density, c is the alcohol concentration, and I is the ionic strength, does not depend on pH and slightly decreases when NaCl concentration increases. The value of this coefficient equals 0.4 dm3 mole−1 for EtOH and 1 dm3 mole−1 for BuOH.

Copper ion activation of synthetic sphalerites with various iron contents

Abstract The adsorption of copper ions on synthetic sphalerites of various iron contents was measured using a radiotracer technique. The correlation of Cu 2+ ions adsorption with the pH of solution, the iron content of the solid and the degree of surface oxidation of synthetic sphalerite were determined. The experiments proved that oxidation of the surface of the sphalerite samples caused a decrease in Cu 2+ ions sorption with the exception of samples of iron containing sphalerite. Acidity of the solution affected the adsorption of Cu 2+ ions by deoxidized sphalerite surfaces, whereas the adsorption on oxidized surfaces did not depend on the pH.

A Comparison of Atmospheric and Electrochemical Oxidation of Vitamin C in SDS Systems

ABSTRACT Ascorbic acid (AA, H2A) can be solubilized up to 60% by weight into a microemulsion formed by water, pentanol, and sodium dodecylsulfate (SDS). Addition of AA to the aqueous solution caused systematic reduction of the microemulsion region in the phase diagrams of the system. Ascorbic anion interacts with dodecylsulfate association structures changing W/O microemulsions towards O/W systems. The polar part of AA is exposed to the aqueous solution and subject to oxidation. The results of kinetic determination of AA decomposition are in accordance with a suggested model. They show enhanced oxidation of AA with increasing pentanol concentration in the system. The system aqueous AA solution/SDS, of concentration in excess of critical micellization concentration (cmc), was found to be more resistant to oxidation in air than aqueous AA solution. This was confirmed by electrochemistry studies of the anodic oxidation of AA on glassy carbon electrode. Sodium dodecylsulfate shifted the AA oxidation potential E pa to more positive values and decreased the peak current I pa . Antioxidation activity of AA was diminished in the presence of SDS micelles.

Effect of surface oxidation and iron contents on xanthate ions adsorption of synthetic sphalerites

Abstract Abstraction of xanthate ions from solution by copper-activated synthetic sphalerites with various iron contents was measured. It was found that raising the iron content in the samples caused a decrease in xanthate ions abstraction. For sphalerite samples characterized by the same percentage of iron deoxidized surfaces took up more xanthate ions than oxidized surfaces. Surface coverage by EtX − ions was determined to be less than one monolayer. These values were compared with copper ion coverage at sphalerite surface. The amount of EtX − ions abstracted from solution was noted to be independent of the pH of the solution in the range from 6 to 10 pH units, above pH =10 a decrease in the abstraction was observed.

Electrical double layer at the α-Fe2O3–mixed electrolyte (ethanol–aqueous) interface

Abstract The adsorption of Na + and Cl − ions from a mixed ethanol–water (1:1) solution of NaCl at the hematite–electrolyte interface was studied. The presence of ethanol in α-Fe 2 O 3 –NaCl solution system has no significant effect on the surface charge density versus pH relationship. On the other hand an influence of ethanol on the zeta potential is greater and provokes the shift of iep from pH=8 in water solution to pH=9 in the mixed system. The adsorption of Cl − ions from ethanol–aqueous solutions is greater and the adsorption of Na + ions is smaller than that from water solutions.

Surface interactions of polymer and surfactant molecules in relation to flotation properties of CaCo3

Abstract Adsorption measurements were carried out to determine the formation mechanism of the polymer-surfactant complex on the solid-solution interface Adsorption was concducted on pure CaCO 3 precipitate as well as on that modulated with a polymer (Polyacrylamide PAA) or surfactant (sodium dodecyl sulfate SDS). The flotation tests carried out on floccubted CaCO 3 confirmed the occurence of interactions between molecules of the polymer and surfactant on the surface of the solid.

Adsorption of cesium on, and desorption from, controlled porous glasses

Cesium contained in aqueous solutions of different composition was adsorbed in columns packed with controlled porous glasses (CPG) and then removed by means of 1M HCl. Recovery of cesium in the eluate was studied as a function of the solution composition and the kind of CPG.

Studies of heterogeneous isotope exchange of Cd(II) between the solution and the surface layer formed on aluminium oxide and activated carbon

Abstract The dependence of the isotope exchange kinetic curves on I∞ I o is studied, where I∞ denotes the equilibrium activity and Io is the initial activity of the solution. Experimental kinetic curves of isotope exchange of Cd (II) ions between the bulk solution and the surface layer formed on aluminium oxide and activated carbon (charcoal) are compared with theoretical calculations.

Adsorption properties of the stearic acid-octadecane particles in aqueous solutions

Abstract The adsorption properties and surface charge creation for the stearic acid and octadecane/aqueous electrolyte solutions are considered. The hairy structure of surface charge for these systems was confirmed on the basis of potentiometric titration, ion adsorption and electrophoretic measurement data. For the system with stearic acid the reaction of ionization and complexation of carboxyl groups of stearic acid molecules from subsurface layer are responsible for the creation of surface charge and adsorption properties. The surface charge at octadecane particle is probably the results in adsorption and orientation of water molecules at the interface.