The polyelectrolyte titration method has been developed overthe years in order to determine the surface charge ofcellulosic fibers. The conditions have been varied depending onthe author. This work has been aimed at resolving theappropriate conditions for measuring the charge, such aselectrolyte concentration and molecular mass of thepolyelectrolyte. The charge ratio of variously treated pulpswas also investigated. The polyelectrolyte titration technique is based on a 1:1adsorption stoichiometry between fiber and polyelectrolytecharges. Adsorption of polydiallyldimethylammonium chloride(poly-DADMAC) was first performed at various electrolyteconcentrations and then with various molecular masses. ESCA(Electron Spectroscopy for Chemical Analysis) was used toindependently validate the polyelectrolyte titrationmethod. Results showed that stoichiometry prevailsat lowelectrolyte concentrations. Increasing the electrolyteconcentration screens the fiber charges, initially enhancingthe adsorption and causing a deviation from stoichiometry.Further increases in electrolyte concentration eventuallydecrease the adsorption. Deviation from stoichiometry occurredat higher electrolyte concentrations for higher charge densitypulps. ESCA-measurements showed that high and low molecularmass cationic polyelectrolyte adsorb to the same extent on thefiber surface, confirming stoichiometry. There was a goodagreement between the two techniques, hence, thepolyelectrolyte titration technique is a good method to measuresurface charges. Comparing the charge ratio between differentkind of pulps and treatments, it was found that mechanicalpulps have a higher surface charge than chemical pulps. Thecharge ratio of chemical pulps was, however, practicallyunchanged when comparing different types of wood and bleachingsequences. <b>KEYWORDS:</b>Adsorption, electrolyte, polyelectrolyte,polyelectrolyte titration, charge stoichiometry, charge ratio,diffuse electric double layer, Debye length, poly-DADMAC,cellulosic fibers, ESCA. / NR 20140805

Two theories for the mechanism of cation adsorption of base exchange clays were investigated. The Charged Lattice theory proposes that the negative charge causing the base exchange is due to substitution of divalent for trivalent and trivalent for tetravalent ions in the alumino-silicate structure. The Ion-Pair theory proposes that the base exchange is due to hydroxyl ions chemisorbed in the surface of the colloidal particles. It was the purpose of this work to apply these two theories to a kaolinite clay and determine the results to ascertain the mechanism or adsorption of cations on the clay. Samples or dialyzed clay were prepared and measured amounts of base were added to each. pH and base ion activity mesurements were made of each sample after equilibrium had been reached. These measurements were applied to mathematical equations representing each theory and the results interpreted through graphs. Further tests of the two theories were made by applying them to a base exchange resin known to have an inherent negative charge. This resin was prepared and treated in the same manner as the clay. It was concluded that the Ion-Pair theory was a possible mechanism, and that the Charged Lattice theory was not a possible mechanism for the adsorption of cations on the kaolinite clay. Neither theory gave completely satisfactory results with the resin, although the Charged Lattice mechanism appeared to hold at low pH values.

Previous work done at the Brigham Young University by Andelin^1, Roberts^2, and Olsen^3, has established the mechanism by which xanthate collectors are adsorbed on molybdenite ores to produce the hydrophobic surfaces necessary for flotation. This thesis is an attempt to better understand the mechanism by which the silicate minerals, which are found in conjunction with the ores, become hydrophyllic and as a result are not floated when in contact with air bubbles. It has been previously established that silicate minerals do adsorb cations on their surfaces^4. The present study has been undertaken to more fully understand the mechanism by which the cations are adsorbed, since the adsorbed cations are at least partially responsible for the hydrophyllic nature of the aluminum silicates. The present study shall be limited to the clays illite, beidellite, bentonite, and kaolinite, which are a group of the aluminum silicate minerals.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.