Effect of Exchangeable Cations on the Flocculation of Bentonite Suspension with Typical Polymer Flocculants

Abstract

Flocculation behavior of homoionic bentonite (Na-, K-, Mg-, Ca-, and Ba-bentonites) particles in aqueous suspension (1.08%) in the presence of cationic, anionic, or nonionic polymer flocculants (1-100 ppm) has been studied.
Cationic polymer (polyethylene imine) flocculated any ion forms of bentonite suspensions. On the contrary, none of the ion forms were flocculated by anionic polymers (sodium polyacrylate and sodium salt of partially hydrolyzed polyacrylamide) except the alkaline-earth metal ion forms for which slight flocculation was observed with sodium polyacrylate (Table 2). Nonionic polymers showed a very powerful flocculating effect toward the alkaline-earth metal ion forms of bentonite suspensions. On the other hand, the alkali metal ion forms were not flocculated by polyacylamide and flocculated only slightly by polyethylene oxide (Table 3).
The roles of typical polymer flocculants for the flocculation of various ion forms of bentonite suspensions are discussed on the basis of the results obtained.