Polymer depressants at the talc-water interface: adsorption isotherm, microflotation and electrokinetic studies

The behaviour of polymer depressants at the talc-water interface was investigated as a function of ionic strength and pH. Adsorption isotherms, microflotation and electrokinetic studies were used to examine the surface interactions involved. The polymers examined were carboxymethyl cellulose (CMC) and two synthetic polyacrylamides (PAM-A and PAWN). The adsorption of the two anionic polymers, CMC and PAM-A, on talc, and hence, talc depression, is greatest when electrostatic repulsion is minimized. At high pH values and low ionic strength, the adsorption density of the anionic polymers on talc is low whilst at either high ionic strength or low pH, the adsorption density increases; talc depression is therefore largely influenced by variations in solution conditions. The adsorption of the nonionic polymers, PAWN, on talc is not influenced by ionic strength or pH. The polymers exhibit Langmuir adsorption behaviour with adsorption occurring on the talc face surface and, possibly, the edge surface. The adsorbed polymer layer thicknesses, calculated from electrophoretic mobility measurements, corresponded to a monolayer indicating that adsorption of the polymers onto the talc surface occurs in a flat conformation. (C) 2002 Elsevier Science B.V. All rights reserved.