ADSORPTION OF DEXTRIN AT MINERAL WATER INTERFACE/

The adsorption mechanism of dextrin on aqueous minerals such as fluori te, apatite, galena, magnetite, gamma-alumina, and graphite was studie d by adsorption experiments, zeta potential measurements, and FT-IR st udies. Depending on the nature of the mineral surface, dextrin was fou nd to interact in three different ways viz. by chemisorption, physisor ption, or hydrophobic-hydrophobic interaction. The adsorption density of dextrin was found to be pH dependent. Maximum adsorption of dextrin was obtained around the pH at which the mineral surface is highly hyd roxylated. The mechanism of dextrin interaction with the surface metal hydroxy sites, (=MeOH), was found to proceed via chemical complexatio n. A linear relationship was observed between the adsorption density o f dextrin and the pH of maximum surface hydroxylation. Zeta potential measurements have indicated the possibility of dextrin adsorption by e lectrostatic interaction under the conditions where mineral surface an d dextrin are oppositely charged. Furthermore dextrin was found to ads orb on hydrophobic minerals such as graphite by hydrophobic-hydrophobi c interaction. However, the magnitude of adsorption by electrostatic a nd hydrophobic interaction was found to be very marginal compared to t hat of chemical complexation. (C) 1997 Academic Press.