minerals like apatite, fluorite and barite, (ii) selective floc-The adsorption mechanism of dextrin on aqueous minerals such culation and flotation separation of hematite from silica, (iii) as fluorite, apatite, galena, magnetite, g-alumina, and graphite differential flotation of sulfide minerals especially in the sepwas studied by adsorption experiments, zeta potential measurearation of galena from chalcopyrite, molybdenite from chalments, and FT-IR studies. Depending on the nature of the mineral copyrite and pyrite, and (iv) depression of coal from pyritic surface, dextrin was found to interact in three different ways viz.
gangue. In recent years, much attention has been paid on by chemisorption, physisorption, or hydrophobic-hydrophobic instarch and its derivatives as an alternative depressant for teraction. The adsorption density of dextrin was found to be pH conventional depressants such as dichromates, cyanides, and dependent. Maximum adsorption of dextrin was obtained around the pH at which the mineral surface is highly hydroxylated. The ferrocyanides, as these chemicals are environmentally highly mechanism of dextrin interaction with the surface metal hydroxy hazardous. Starches derived from different sources were sites, (GMeOH), was found to proceed via chemical complexused as depressants for inherently hydrophobic minerals ation. A linear relationship was observed between the adsorption such as graphite, muscovite, biotite, talc, and coal (2-7).
density of dextrin and the pH of maximum surface hydroxylation.
Despite its widespead application, very few investigators
Zeta potential measurements have indicated the possibility of dexhave paid attention to the mechanism of adsorption. Deprestrin adsorption by electrostatic interaction under the conditions sion of molybdenite by dextrin was studied by Wie and where mineral surface and dextrin are oppositely charged. Fur-Fuerstenau (2). A hydrophobic binding mechanism was prothermore dextrin was found to adsorb on hydrophobic minerals posed based on the free energy of adsorption. A similar such as graphite by hydrophobic-hydrophobic interaction. Howhydrophobic binding mechanism was suggested by Miller et ever, the magnitude of adsorption by electrostatic and hydrophobic interaction was found to be very marginal compared to that of al. (6) in the case of pyrite separation from coal. Some chemical complexation. α§ 1997 Academic Press researchers have suggested that dextrin interacts with min-Key Words: dextrin; fluorite; apatite; galena; magnetite; g-alueral surfaces through nonselective hydrogen bonding. The mina; adsorption models. adsorption of starch pertaining to flotation and flocculation of iron ores was interpreted in terms of electrostatic and hydrogen bonding forces and by interparticle bridging (8).