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Coagulation of negatively-charged colloids by anionic polyelectrolytes and metal ions

1973; Elsevier BV; Volume: 43; Issue: 2 Linguagem: Inglês

10.1016/0021-9797(73)90383-4

1095-7103

N. Sarkar, Arthur S. Teot,

Electrostatics and Colloid Interactions

Abstract Coagulation of well-characterized monodisperse anionic lyophobic colloids (polystyrene latexes) in the presence of sodium polystyrene sulfonate (SPSS) and metal ions has been correlated with the adsorption of SPSS and metal ions, SPSS-metal ion interactions, and electrokinetic properties. Sensitization of latex particles by SPSS occurs only in the presence of multivalent metal ions. Adsorption of metal ions alone on latex could not be detected. Adsorption of SPSS on latex was a function of the type and concentration of the metal ions. An approximately stoichiometric amount of La 3+ was adsorbed with the SPSS. A solution of SPSS formed a colloidal sol of insoluble lanthanum polystyrene sulfonate [La(SS) 3 ] in the presence of La 3+ in excess of the equivalent concentration of SPSS. Coagulation of these La(SS) 3 sols occurred at higher La 3+ concentrations. Coagulation concentrations of La 3+ for the La(SS) 3 sols were the same as that for the latex containing an equal amount of SPSS. Electrophoretic mobility of the La(SS) 3 at the critical coagulation concentration of La 3+ was zero, and there was no charge reversal. The initial rate of coagulation of latex was independent of SPSS molecular weight, but settling rate and floc size increased with increasing molecular weight. The mechanism of coagulation has been interpreted as either a particle-particle interaction between neutral La(SS) 3 and latex, or effective charge reduction of latex.