A Comparison of New Gemini Surfactant Modified Clay with its Monomer Modified One: Characterization and Application in Methyl Orange Removal

Abstract

New gemini surfactant, glycol bis-N-tetradecyl nicotinate dibromide (designated EG), and the corresponding monomer, methyl N-tetradecyl nicotinate bromide (ES), were synthesized and utilized to modify sodium bentonite (Na-Bt). EG-Bt and ES-Bt, the surfactant modified bentonites, were then used for methyl orange (MO) removal from the dye solution. EG was more effective than ES at expanding the interlayer space of Na-Bt. The adsorption of EG, ES and MO obeyed well the pseudo-second-order kinetic model and Langmuir isotherms on Na-Bt or on the modified bentonite. However, the adsorption of EG was more spontaneous than that of ES, and EG replaced more small particles, such as Na+ and water, than ES did during the adsorption on Na-Bt. The elevated temperature impairs the adsorption of the surfactants, but enhances that of MO. MO absorbed more easily on EG-Bt than on ES-Bt. When the dosage of the surfactants used goes beyond a certain amount, the uptake of MO by EG-Bt/ES-Bt decreases slowly owing to desorption of the surfactants. EG and ES formed a complex with MO on the modified bentonite as evidenced by UV–vis spectra, and EG exhibited the stronger interaction with MO.