Flocculation and coagulation of Ca- and K-saturated montmorillonite in thepresence of polyethylene oxide

The objective of this work is to study the flocculation of Ca- and K-montmo rillonite in the presence of some coagulant (CaCl2 and KCl) and mixtures of coagulants and polyethylene oxide (600,000 mol wt) through measuring the z eta potential. The action of Ca2+ was more effective than K+ in decreasing the zeta potential of Ca-montmorillonite; consequently, the electrical doub le layer of the clay particles has been reduced. On the other hand, the act ion of K+ was more pronounced than Ca2+ in decreasing the zeta potential of K-montmorillonite. This contradicting result was attributed to the change of the partial molal volume of Ca- and K-montmorillonite. The flocculation of Ca- and K-montmorillonite by polyethylene oxide was enhanced when the cl ay was initially treated with electrolyte. This electrolyte reduces the thi ckness of the electrical double layer. Under this condition, the polymer se gments collapse on the clay surfaces, leaving polymer loops and tails avail able for contacting adjacent clay particles. (C) 1999 John Wiley & Sons, In c.