Sorption of Cr (VI) from aqueous solutions on Erionite, Cowlesite and Willhendersonite modified with hexadecyltrimethyl ammonium bromide (HDTMAB). Experiments were carried out as a function of solution pH, solute concentration and temperature (15oC- 35oC). Modified zeolites were investigated by X-ray diffraction and Fourier transforms infrared analysis. The HDTMA modified zeolites showed significant sorption for chromate ions in aqueous solution. Sorption data for each anion was well described by Langmuir isotherm equation. The thermodynamic parameters (
Ho,
Go and
So) for Cr (VI) sorption on the modified zeolites were also determined from the temperature dependence. FTIR analysis showed that sorbed SMZ forms an ad-micelle surfactant surface coverage, which is responsible for Cr (VI) sorption.