Single and binary adsorption of azo blue and mordant black 17 with vermiculites functionalized by amphoteric gemini surfactants: Performance and mechanism

Abstract

Incorporation of amphoteric gemini surfactants into vermiculite (Vt) is a valuable task in developing clay application. Hereby amphoteric gemini surfactants with hydrophobic alkyl chains, dual N⁺ head groups and anionic functional groups are introduced to prepare organo-Vts as dye adsorbents. The adsorbents are labeled as TAES-Vt with sulfonic acid group and TABS-Vt with benzenesulfonic acid groups, respectively. Both single and binary adsorption towards azo blue (AB) and mordant black 17 (MB17) have been investigated. The max uptake amounts in single dye system are 189/177 mg/g for AB and 278/406 mg/g for MB17 by TAES-Vt/TABS-Vt, respectively. Furthermore, the presence of AB is favorable for the removal of MB17 in binary dye system, with adsorption capacities increasing to 449/469 mg/g by TAES-Vt/TABS-Vt. However, MB17 exhibits an antagonistic effect on adsorption of AB, thus resulting lower AB removal capacities in binary dye system. The adsorption mechanisms are elucidated via adsorption, characterization and calculation. (i) Hydrophobic interaction, electrostatic interaction, H-bond, and electron donor effect all support the adsorption for AB/MB17. (ii) Compared to TABS-Vt, TAES-Vt has a slightly higher adsorption capacity for large-sized AB due to its larger interlayer spacing. However, TABS-Vt is better at adsorbing small-sized MB17 than TAES-Vt by vitue of additional benzene ring that can provide π-π interaction. (iii) In view of adsorbates, the difference of molecular size and structural property in AB and MB17 also affect adsorption. This work provides ideas for the multi functionalization of Vt, reviving the adsorption advantages of clay based materials.