COMPETITIVE ADSORPTION OF POLYMER AND SURFACTANTS ON SOLID SUBSTRATES

Polymer and surfactant adsorption on substrates has important applicat ions in a variety of fields such as solid-solid separations, dispersio n and flocculation of particulate suspensions, and controlled drug del ivery systems. In pharmaceutical applications coating of different mol ecules in controlled amounts on a given carrier substrate may be desir ed to achieve the necessary efficacy of the drug molecules. On the oth er hand, the concept of different substrates (e.g., minerals) competin g for a given polymer/surfactant molecule is governing phenomena for p hysicochemical separation processes such as selective flocculation and flotation. Selective flocculation process involves selective adsorpti on of flocculant (high molecular weight polymer) on the flocculating c omponent of the mixture. Modifications in the substrate properties (e. g., charge density, wettability), polymer characteristics (e.g., molec ular weight, charge density, wettability) and solvent properties (e.g. , pH, ionic strength, temp.) may all be employed to achieve the floccu lant adsorption only on the desired component of the particulate mixtu re. Confining the adsorption of a flocculant to the desired complement of the particulate mixture using site blocking agents (SBAs - low mol ecular weight polymers) is discussed. (C) 1998 Elsevier Science B.V.