Effect of tween 80 on removal of chromate using ultrafiltration enhanced by cetylpyridinium chloride

In this paper, the effect of a nonionic surfactant, Tween 80 (TW80), on the removal of chromate (CrO42-) by micellar enhanced ultrafiltration (MEUF) using cetylpyridinium chloride (CPC), together with the micellization of mixed CPC:TW80, as well as the effects of chromate ion concentration, co-existing (Cl) ion concentration and operating pressure on ultrafiltration using mixed CPC:TW80, were investigated. The addition of TW80 decreased the critical micellar concentration (CMC) of surfactant and the zeta potential of micelles. The chromate rejections increased and then leveled off with the concentrations of CPC and CPC:TW80. However, given the total surfactant concentration, the addition of TW80 led to obvious reduction in chromate rejection, where the rejection efficiencies of chromate ions were negatively related to the mass fractions of TW80 in mixed CPC:TW80. Correspondingly, the permeate fluxes decreased with the surfactant concentrations and the extents of flux reduction were positively related to the TW80 fraction. However, the CPC rejections were much enhanced by the addition of TW80. Taking the mixed CPC:TW80 at 5:5 mass ratio, for example, the initial chromate concentration, co-existing ion (Cl-) concentration and operating pressure exhibited various effects on the removal of chromate ions. The results illustrated the effect of a nonionic surfactant on removal of anionic heavy metal ions using a cationic surfactant in MEUF.