The adsorption of a polysaccharide at the talc aqueous solution interface

An investigation of the mechanism of adsorption of guar, a natural nonionic polysaccharide, at the talc-aqueous solution interface has been performed. Hydrophobic interactions were found to dominate the adsorption process, leading to adsorption of the guar onto hydrophobic sites, i.e. the talc "face". Hydrogen bonding made only a small contribution to the adsorption, whilst chemical interactions were completely absent. In the case of ionically modified guars, the electrostatic contribution to the overall thermodynamics of adsorption was weak. Both unmodified and modified guars were found to adsorb in a very flat conformation with in er,cess of 75% of the constituent segments present in the form of "trains" at the talc-aqueous solution interface. Determinations of adsorbed layer thickness, calculated from microelectrophoresis measurements, supported this finding. The mannose backbone of the guar chain adsorbed to the talc surface, leaving the pendant galactose groups protruding into the bulk solution. (C) 1998 Elsevier Science B.V. All rights reserved.