Adsorption of polysaccharide onto talc

Abstract

The interaction of polysaccharide with talc has been investigated through adsorption, flotation, and electrokinetic measurements. The adsorption densities are independent of pH and the isotherms exhibit Langmuirian behavior. The order of adsorption density of several polysaccharides investigated in the paper onto talc is CMC > CMS > dextrin. Pretreatment of talc with EDTA (ethylenediaminetetraacetic acid), leaching and calcinations result in a decrease in the adsorption density, highlighting the importance of metallic magnesium sites for the adsorption process. An increase in the surface face-to-edge ratio leads to increase in adsorption density. The flotation recoveries are independent of pH. CMC exhibit best depressant ability, followed by CMS and then dextrin among the three depressants, complementing the adsorption results. However, polysaccharide depressant ability is reduced in the case of leached and calcined talc sample in comparison to that on talc. Electrokinetic measurements portray conformational rearrangements of macromolecules with the loading, resulting in the shift of the shear plane, further away from the interface. The adsorption process is governed by hydrogen bonding as well as chemical interaction between the polysaccharides and the surface metal hydroxide groups of talc. The best depressant activity of CMC may be attributed to its more favorable carboxyl groups as opposed to the hydroxyl groups of dextrin, apart from its higher molecular weight.