Abstract: Zeolite was modified to a varying extent with cation surfactant CTAB(hexadecyltrimethylammonium bromide) added at different rates and amount of CTAB adsorbed by different modified zeolites was determined.Then comparison was made between these modified zeolites in chromate adsorption capacity and in relationship between chromate adsorption on modified zeolites and Zeta potential in its suspension system,to explore mechanism of chromate adsorption by zeolite,and adsorption capacity of renewed zeolites.Results show that with the rising CTAB application rate,both CTAB adsorption on zeolite and chromate adsorption capacity of the modified zeolite increased obviously.And so did the Zeta potential of zeolite,turning from negative into positive after modification by cation surfactant.It is hence clearly indicated that the adsorption of cation surfactant on zeolite induced a change in its surface charge properties.Chromate absorption by the modified zeolites decreased with the increase in ionic strength,and most of the chromate adsorbed on modified zeolites can be desorbed by neutral salt,which suggested that the electrostatic interaction between the modified zeolite and chromate was the major mechanism for the enhanced adsorption of chromate.If addition of CTAB is controlled in the range from 0.15 to 0.30 mol·kg^-1,the used modified zeolite can be renewed for use again as absorbent for chromate.

Key words: hexadecyltrimethylammonium bromide(CTAB), surfactant-modified zeolite, chromate, adsorption-desorption