Molecular weight effects in interactions of guar gum with talc

• Systematic flotation and aggregation data as a function of molecular weight
• Lack of significant effect of molecular weight on adsorption
• Demonstrated a correlation between depression and flocculation
• Good correlation between molecular weight and talc flocculation/dispersion

Interactions between talc and four non-ionic guar gum samples of different molecular weights (from 160,000 to 1.40 million) were evaluated through adsorption, flotation, and stability measurements. It was found that the effect of molecular weight on adsorption was insignificant and all four guar gums produced similar adsorption densities on the talc particles. Turbidity data also showed that all four polymers were strong flocculants of fine talc particles. However, higher molecular weight samples were more powerful than lower molecular weight samples. Higher doses of the polymers led to steric re-dispersion of talc, and lower molecular weight polymers were more efficient in dispersing talc than higher molecular weight polymers. Finally, all four polymers were equally effective as depressants of talc flotation. Most interestingly, it was found that the strongest depression of talc flotation was accompanied by very strong flocculation of the fine talc particles. Implications of these phenomena to the entrainment of fine talc during the froth flotation process were also discussed.