Reviving the Potential of Vermiculite-Based Adsorbents: Exceptional Ibuprofen Removal on Novel Amide-Containing Gemini Surfactants

In this study, we introduce a novel series of gemini surfactants with amide groups (HDAB, HDAHD, and HDAPX) and use these surfactants to decorate sodium vermiculite (Na-Vt) for the adsorption of Ibuprofen (IBP) from wastewater. Exceptional IBP uptake on organo-vermiculites (organo-Vts) is obtained, with maximum adsorption capacities reaching 249.87, 342.21, and 460.15 mg/g for HDAB-Vt, HDAHD-Vt, and HDAPX-Vt (C0 = 500 mg/L, modifier dosage = 0.2 CEC), respectively. The adsorption of IBP is well fitted by pseudo-second-order, intraparticle diffusion, and Freundlich isotherm models, verifying chemical adsorption processes with multilayer arrangement of IBP in organo-Vts. Thermodynamically, the removal of IBP on HDAHD-Vt is exothermic, while the endothermic nature aptly describes the adsorption process of HDAB-Vt and HDAPX-Vt. Moreover, organo-Vts can be stably regenerated in three cycles. Outstanding adsorption performance of organo-Vts is attributed to synergistic effects of the partition process and functional interaction, which are influenced by the steric hindrance and chain configuration of the modifier. A combined evaluation of adsorption tests and fitting calculations is employed to reveal the adsorption mechanism: (i) the incorporation of amides into the alkyl chain significantly enhances the utilization of the interlayer space in organo-Vts. (ii) Smaller steric hindrance and higher rigidity of the modifier spacer contribute to improved adsorption performance. The findings in this study rekindle interest in Vt-based adsorbents, which demonstrate comparable potential to other emerging adsorbents that are yet to be fully explored.