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 E G ), and the corresponding monomer, methyl N -tetradecyl nicotinate bromide (E S ), were synthesized and utilized to modify sodium bentonite (Na-Bt). E G -Bt and E S -Bt, the surfactant modified bentonites, were then used for methyl orange (MO) removal from the dye solution. E G was more effective than E S at expanding the interlayer space of Na-Bt. The adsorption of E G, E S 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 E G was more spontaneous than that of E S, and E G replaced more small particles, such as Na + and water, than E S 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 E G -Bt than on E S -Bt. When the dosage of the surfactants used goes beyond a certain amount, the uptake of MO by E G -Bt/E S -Bt decreases slowly owing to desorption of the surfactants. E G and E S formed a complex with MO on the modified bentonite as evidenced by UV–vis spectra, and E G exhibited the stronger interaction with MO.