The preparation of organo-bentonite by a new gemini and its monomer surfactants and the application in MO removal: A comparative study

Solid-state UV–vis spectra of the samples employed in this study. [Display omitted] ► NG is more effective than NS in expanding basal space and in removing MO. ► NS mainly stays in interlayer, however NG on the clay surface due to its big head. ► MO removal by NG-Bt/NS-Bt is pH dependent. ► The complex of MO–NG-Bt/MO–NS-Bt forms during MO removal. Gemini surfactant, 1,1′-(butane-1,4-diyl)-bis(3-(tetradecyloxycarbonyl)pyridinium) dibromide (designated as NG), and the corresponding monomer, 1-ethyl-3-(tetradecyloxycarbonyl)pyridinium bromide (NS), were prepared and utilized to modify sodium bentonite (Na-Bt). The surfactant modified bentonites (NG-Bt for the gemini modified bentonite and NS-Bt for the monomer modified one) were then used for methyl orange (MO) removal from the wastewater. The results indicated that the gemini surfactant NG was more effective than the monomer NS at expanding the interlayer space of Na-Bt and in removing MO from wastewater. The maximum basal spacing of NG-Bt (4.02nm) was almost twice as that of NS-Bt (2.63nm). MO removal efficiency was 9.68% for 4.0NS-Bt and 99.88% for 4.0NG-Bt at a dosage of 0.06g, respectively. NS easily intercalated into the interlayer of Na-Bt, however more NG mainly stayed on the solid surface owing to its bigger head. The adsorption of both NG and NS on Na-Bt obeyed the pseudo-second-order kinetic model and Langmuir isotherms. The solid-state UV–vis spectrometry evidenced the formed complex of NG/NS with MO on Na-Bt, and the stronger interaction of NG-Bt with MO.