The Adsorption of Four Pesticides in Wastewater by Cetyltrimethylammonium Bromide (CTMAB)Modified Bentonites

The modifying bentonites with Cetyltrimethylammonium Bromide(CTMAB) have been done and the properties and optical absorbed conditions for CTMAB-bentonites to adsorb carbaryl, parathion methyl, carbofuran,and carbendazim in wastewater have been investigated. The results indicate that the adsorptive capacity of CTMAB-bentonites is significant and revalent to the real exchange volumes of CTMAB in the bentonites.The more contents of CTMAB exist in the bentonites, the stronger adsorptive capacity they have. As CTMAB concentrations are beyond 4%, the adsorptive capacity of organic clays becames maximum and keeps unchangeable. Adsorption isotherms are linear, indicating that partition model may be predomindant. Adsorption of four pesticides is very rapid,with the bulk of the adsorption occuring within the first 10 mintues of contact. The pH variation has different effects on adsorption capacity, which depend on the characters of pesticides. The research has shown that low pH decreases the adsorption capacity of CTMAB-bentonites. While adsorption rate of these four pesticides is stable in the pH range of 4～10. High pH results in increase of carbendazim adsorption and alkali hydrolysis of carbaryl, parathion methyl, carbofuran