Preparation of imidazolium-based poly(ionic liquid) and its adsorption performance for acid black 10B dye

An imidazolium-based poly(ionic liquid), [VIm-4VBC][Cl]-EGDMA, was prepared by radical copolymerisation of a divinyl imidazolium ionic-liquid monomer, 1-(4-vinylbenzyl)-3-vinylimidazolium chloride ([VIm-4VBC][Cl]), with ethylene glycol dimethacrylate (EGDMA), and applied to the removal of the anionic azo dye Acid Black 10B from aqueous solution. The material was characterised by 1 H NMR, FT‒IR, SEM‒EDS, XPS, and TG‒DSC. It maintained a removal efficiency of 99.4% over the pH range 3‒9 and showed a maximum adsorption capacity of 1063.4 mg g −1 . The adsorption data were well described by the Langmuir isotherm and pseudo-second-order kinetic models. Combined XPS, FT‒IR, and SEM‒EDS analyses before and after adsorption indicated that the adsorption was driven primarily by electrostatic attraction between the cationic imidazolium framework and the dye sulfonate groups, partially proceeding via anion exchange with framework Cl − , with hydrogen bonding and π‒π stacking making secondary contributions. The adsorbent retained more than 80% of its capacity in the presence of 0.10 mol L −1 NaCl or Na 2 SO 4 . After five adsorption–desorption cycles using 0.10 mol L −1 NaOH as the desorbent, the adsorption capacity decreased from 503.8 to 428.3 mg g −1 (capacity retention of 85%), indicating good reusability.