COMPETITIVE ADSORPTION OF CATIONIC SURFACTANT AND PESTICIDE ON LAPONITE

Simultaneous adsorption of quaternary ammonium surfactants (mono-, di- and tri-) and 1,1'-dimethyl-4,4'-bipyridinium dichloride (paraquat) o n laponite was studied under a constant feed concentration of paraquat where an amount adsorbed of paraquat in the absence of surfactants co rresponded to about 10% of cationic exchange capacity of the laponite. The adsorbed amount of paraquat decreased with increasing adsorbed am ount of the surfactant, indicating a competitive adsorption between pa raquat and the surfactant. In addition, the replacement of paraquat wi th the adsorption of cationic surfactant was very similar for the thre e surfactants. The interlayer space with the adsorption of paraquat in creased with increasing adsorbed amount of the surfactant. (C) 1998 El sevier Science B.V.