Targeted adsorption of phenol on organo vermiculites with spacer-tunable gemini surfactant containing amide groups

The design of effective phenol adsorbents remains an important issue in industrial wastewater treatment. This study develops amide-containing gemini surfactants to modify vermiculite (G8-NE-VT, G8-OL-VT and G12-NE-VT) for phenol adsorption. Guided by “functional connector” strategy, longer alkyl chains in G12-NE-VT contribute to looser surfactant packing and greater hydrophobicity, while functional groups in the spacer of G8-OL-VT improve interaction density and adsorption performance. The adsorption of phenol follow the order of: G8-OL-VT (160.78 mg/g) > G12-NE-VT (111.06 mg/g) > G8-NE-VT (80.82 mg/g). The highest adsorption amounts are obtained on G8-OL-VT (274.23 mg/g). All the adsorption processes are fitted well by pseudo-second-order kinetic model and Redlich-Peterson isotherm. Exothermic adsorption character involves hydrophobic interactions, hydrogen bonding, π-π stacking, and electrostatic interactions between phenol and organo-VT. Shorter alkyl chains enhance the role of additional interactions for phenol retention. Moreover, the applicability of G8-OL-VT is demonstrated by reliable regeneration and high selectivity. Results in this work focus on achieving high adsorption capacity and advancing material design for pollutant treatment, as well as overcome the challenges associated with phenol’s intrinsic polarity and hydrophilia, resulting in superior adsorption performance compared to conventional adsorbents.