SORPTION ISOTHERMS AND MODELING STUDIES OF HDTMA FOR ADSORPTION ONTO VERMICULITE, PERLITE AND ZEOLITE CLAYS

In this study, as being a cationic surfactant, hexadecyltrimethylammonium bromide '(HDTMA-Br) sorption on vermiculite, perlite and zeolite was investigated. Because of using cationic surfactant as softener in the last rinsing, it is discharged as household waste to environmental media at high concentrations. Therefore, removal of cationic surfactants from environmental media is important. Sorption characteristics were searched in terms of sorption capacities and Langmuir, Freundlich, Temkin and Dubinin-Redushkevich isotherm models using batch method. After changing surface of adsorbents to their homoinonic forms by using NaCl, surfaces were become suitable for sorption of positively charged surfactant molecules. HDTMA sorption on vermiculite was best described by Freundlich isotherm model, while Langmuir model was fitted well for perlite and zeolite. Also, experimental and theoretical qe values were compared and found that they were fitted well with each other. As a result of experiments, it was found that retained HDTMA by adsorbents were 99%, 75% and 96.5% for vermiculite, perlite and zeolite, respectively. It is assumed that the major mechanisms for the sorption of HDTMA on adsorbent are ion exchange between Na ions and HDTMA molecules, electrostatic interaction between negatively charged surface and positively charged surfactant molecules, and also hydrophobic interactions between hydrophobic sides of HDTMA molecules.