Interaction of xanthan gum with suspended solids.

Xanthan gum was adsorbed significantly by magnesium carbonate, aluminum hydroxide, zinc oxide, and calcium carbonate, giving Langmuir-type isotherms. Saturation adsorption was higher from 0.9% NaCl than from water due to reduced mutual repulsion of polymer segments in the presence of the salt. Adsorption resulted from electrostatic attraction between positively charged particles and the negatively charged polymer. zeta-Potential measurements correlated with the adsorption data but were not predictive of the flocculation state. The result indicate that flocculation of magnesium carbonate and aluminum hydroxide by xanthan gum is consistent with a bridging mechanism.