A STUDY OF THE EFFECT OF SHEAR, WATER CONTENT, AND HYPOCHLORITE ADSORPTION ON THE CHEMICAL AND PHYSICAL PROPERTIES OF ALUMINUM - HYDROXYCARBONATE SUSPENSION. PART I: THE EFFECT OF SHEAR ON PARTICLE INTERACTIONS IN ALUMINUM - HYDROXYCARBONATE SUSPENSION. PART II: THE ROLE OF WATER IN THE AGING OF ALUMINUM - HYDROXYCARBONATE SUSPENSION. PART III: THE ADSORPTION OF HYPOCHLORITE BY ALUMINUM - HYDROXYCARBONATE SUSPENSION
Abstract
Part I. The Effect of Shear on Particle Interactions in Aluminum Hydroxycarbonate Suspension. Shear produced changes in the apparent viscosity of aluminum hydroxycarbonate suspensions. The viscosity changes were attributed to changes in the aggregation state of the suspension. The variations in aggregation state were a result of a shear-induced pH change which altered the pH-ZPC relationship. The pH of the suspension was shifted towards the ZPC after shear. Carbonate loss was proposed as a mechanism for the shear-induced pH change. Shear produced no permanent particle dispersal. The pH change induced by selected processing equipment was evaluated. Fiber optic Doppler anemometry was used to determine the critical volume fraction of aluminum hydroxycarbonate suspensions. The critical volume fraction was representative of the gelation point of the suspension. Part II. The Role of Water in the Aging of Aluminum Hydroxycarbonate. Water was found to participate in the aging of aluminum hydroxycarbonate through a physical and a chemical aging process. When all water in the system exists as bound water, aging occurred solely through the physical aging mechanism and the aging was reversible by dehydration or sonication. Particle aggregation was proposed as a mechanism for the physical aging which occurred. When free water was present both chemical and physical aging occurred. A method for determining the proportion of the loss in acid reactivity which can be attributed to physical aging and the portion attributable to chemical aging was proposed. Part III. The Adsorption of Hypochlorite by Aluminum Hydroxycarbonate. Hypochlorite was specifically adsorbed by aluminum hydroxycarbonate and by boehmite. Specific adsorption was indicated because: (1) adsorption was independent of surface charge; (2) the zero point of charge decreased following adsorption; and (3) the fraction of hypochlorite bound was proportional to the surface area.
Degree
Ph.D.
Subject Area
Pharmaceuticals
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