Comparative Study of Cationic Surfactant CTAC Tailoring

Abstract

Cationic surfactant cetyltrimethylammonium chloride (CTAC) was employed to tailor-activated carbon, granular ferric hydroxide (GFH), chitosan, zeolite, and bentonite so as to investigate the effect of CTAC tailoring on perchlorate adsorption. Surfactant loading varied with adsorbent. Surface porosity and ion exchange capacity all contributed to surfactant loading. In particular, bentonite and activated carbon showed the highest loading of surfactant. In comparison, chitosan was able to contain only a negligible amount of CTAC. One direct effect of CTAC tailoring was the increase of adsorbent’s surface point of zero charge pHpzc. However, the extent of pHpzc change differed with adsorbents, and this is attributed to the differences in interactions between surfaces and CTAC. The CTAC loading on activated carbon is more likely attributable to hydrophobic-hydrophobic interaction, whereas CTAC’s was anchored onzeolite and bentonite by interaction between the hydrophilic head of CTAC and surface. Also, CTAC tailoring greatly enhanced activated carbon and GFH’s adsorption of perchlorate, and most of the adsorption was through ion exchange. In contrast, CTAC-tailored bentonite actually saw a decrease in its perchlorate adsorption capacity.