Hydroxyl-functionalized ionic liquid-based cross-linked polymer as highly efficient adsorbent for anionic azo dyes removal

Hydroxyl-functionalized ionic liquid-based cross-linked polymer is synthesized from 1-hydroxyethyl-3-vinylimidazolium chloride and divinylbenzene. The physicochemical properties of the adsorbent are investigated by scanning electron microscopy, thermogravimetric analysis , and Fourier transform infrared spectroscopy . The adsorption capacity of the novel cross-linked polymer with respect to anionic azo dyes is investigated using a batch adsorption procedure and the kinetics and thermodynamics of the adsorption process are further investigated. It is found that the adsorption kinetics is well fitted by a pseudo-second-order model and the adsorption isotherms agree well with the Langmuir model. The maximum adsorption capacity after 5   h at room temperature (25   °C) could reach 2095.80 and 2100.98   mg/g for orange II and sunset yellow FCF, respectively. The adsorption capacity is much better than most of the previously reported adsorbents. The introduction of hydroxyl-functionalized task-specific ionic liquid moieties into cross-linked polymer constitutes a new and efficient kind of adsorbent.