Effect of calcium ions on the adsorption of CMC onto the basal planes of New York talc – A ToF-SIMS study

Talc is a magnesium rich phylosilicate mineral that occurs as a gangue component of many base metal sulfide ore deposits around the world. The basal planes of talc are naturally hydrophobic and therefore talc is highly floatable. In order to reduce talc floatability, polymeric depressants such carboxymethyl cellulose (CMC) are commonly utilised. Typical depressants are natural cellulose based polymers such Depramin®, produced by Akzo Nobel. This paper examines the adsorption characteristics of a charged polymeric depressant (CMC) on the basal planes of New York talc using surface specific ToF-SIMS measurements. The effect of the presence of calcium ions in solution on the adsorption density of charged polymers is also studied. The adsorption density of CMC was measured both in the presence and absence of calcium ions in solution. It was found that the presence of calcium greatly enhanced the adsorption density of the polymer. This was attributed to the increased concentration of CaOH+ ions on the mineral surface, which facilitated polymer adsorption though acid/base interactions. The enhanced adsorption density was also attributed to the increased amount of coiling of the CMC macromolecules due to their reaction with Ca2+ ions.