Effect of electrolyte and pH on the interaction of sodium carboxymethyl cellulose on barium sulphate particles

Abstract
Adsorption isotherms of sodium carboxymethyl cellulose onto barium sulphate have been determined as a function of the degree of carboxylation of the polyelectrolyte, pH and added electrolyte concentration. At pH 6.5, high-affinity isotherms are obtained, the adsorption capacity increasing with decreasing charge density of the polyelectrolyte. The addition of simple electrolyte enhances the adsorption by an amount which depends on the nature of the ions present. At pH 2, the affinity for the surface decreases but the adsorption is enhanced for all charge-density types.These observations are discussed in conjunction with electrophoretic mobility and viscosity measurements, and it is demonstrated that electrostatic contributions largely dominate the adsorption process.

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