Fenitrothion adsorption – desorption on organo – minerals

Abstract The adsorption–desorption of the pesticide fenitrothion on organo-montmorillonite, organo-clinoptilolite and organo-sepiolite was studied at different loadings of stearyl- dimethylbenzylammonium cations (SDBA). The SDBA retained by ion exchange mostly remained on the surface of the minerals after washing with an ethanol/water solution. The hydrophobic character of the organo-minerals with monolayer coverage of the surface was confirmed by adsorption of water vapor. The adsorption of organo-montmorillonite, organo-sepiolite and organo-clinoptilolite for fenitrothion increased with the surfactant loading up to the value of the cation exchange capacity (CEC) for montmorillonite and sepiolite and of the external cation exchange capacity (ECEC) for clinoptilolite. The adsorption of the most hydrophobic samples (M80, C7.5 and S15), at a concentration of the pesticide of 10 mg/dm 3 in solution, was 99%, 89% and 95%, respectively. The maximal amounts of pesticide adsorbed on the organo-montmorillonite, organo-clinoptilolite and organo-sepiolite were 300 μmol/g, 150 μmol/g and 130 μmol/g. The amounts of fenitrothion, released from organo-montmorillonite, organo-clinoptilolite and organo-sepiolite pesticide complexes into 0.005 M diethylenediamine-pentacetic acid, 0.1 M CaCl 2 and 0.1 M triethanolamine solution after ten cycles were 20%, 40% and 50%, respectively.