Competitive adsorption of polymer and surfactants on solid substrates

Polymer and surfactant adsorption on substrates has important applications in a variety of fields such as solid-solid separations, dispersion and flocculation of particulate suspensions, and controlled drug delivery systems. In pharmaceutical applications coating of different molecules in controlled amounts on a given carrier substrate may be desired to achieve the necessary efficacy of the drug molecules. On the other hand, the concept of different substrates (e.g., minerals) competing for a given polymer/surfactant molecule is governing phenomena for physicochemical separation processes such as selective flocculation and flotation. Selective flocculation process involves selective adsorption of flocculant (high molecular weight polymer) on the flocculating component of the mixture. Modifications in the substrate properties (e.g., charge density, wettability), polymer characteristics (e.g., molecular weight, charge density, wettability) and solvent properties (e.g., pH, ionic strength, temp.) may all be employed to achieve the flocculant adsorption only on the desired component of the particulate mixture. Confining the adsorption of a flocculant to the desired complement of the particulate mixture using site blocking agents (SBAs - low molecular weight polymers) is discussed. (C) 1998 Elsevier Science B.V.