A Comparison of New Gemini Surfactant Modified Clay
with its Monomer Modified One: Characterization and Application in
Methyl Orange Removal
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Abstract
New gemini surfactant, glycol bis-<i>N</i>-tetradecyl
nicotinate dibromide (designated E<sub>G</sub>), and the corresponding
monomer, methyl <i>N</i>-tetradecyl nicotinate bromide (E<sub>S</sub>), were synthesized and utilized to modify sodium bentonite
(Na-Bt). E<sub>G</sub>-Bt and E<sub>S</sub>-Bt, the surfactant modified
bentonites, were then used for methyl orange (MO) removal from the
dye solution. E<sub>G</sub> was more effective than E<sub>S</sub> at
expanding the interlayer space of Na-Bt. The adsorption of E<sub>G</sub>, E<sub>S</sub> 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<sub>G</sub> was more spontaneous than
that of E<sub>S</sub>, and E<sub>G</sub> replaced more small particles,
such as Na<sup>+</sup> and water, than E<sub>S</sub> 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<sub>G</sub>-Bt than on E<sub>S</sub>-Bt. When the dosage of the
surfactants used goes beyond a certain amount, the uptake of MO by
E<sub>G</sub>-Bt/E<sub>S</sub>-Bt decreases slowly owing to desorption
of the surfactants. E<sub>G</sub> and E<sub>S</sub> formed a complex
with MO on the modified bentonite as evidenced by UV–vis spectra,
and E<sub>G</sub> exhibited the stronger interaction with MO
