Wood meet MOFs: Facile, green, and highly selective adsorbent for textile wastewater

Abstract

Owing to their unique physicochemical features, ionic liquids (ILs) are extensively utilized to dissolve cellulose for the preparation of regenerated cellulose fibers (RCFs) in the textile industry. However, Cu2+ is introduced during the cellulose dissolution process and gradually accumulates, seriously affecting the RCF performance and IL recovery. Herein, to achieve an efficient and selective adsorption of Cu2+ from ILs aqueous solutions, a facile and green method based on the in situ growth of zeolitic imidazolate framework-67 in wood hydrogels (ZIF-67@WH) is presented. The morphology, functional groups, crystallinity, thermal stability, and pore structure of the resulting ZIF-67@WH were investigated using various characterization techniques, and the adsorption selectivity, adsorption thermodynamics, adsorption kinetics, and recoverability were examined in depth by performing batch experiments. The ZIF-67@WH exhibits high adsorption selectivity for Cu2+ and ILs with adsorption ratios of 92.8 % and 2.2 %, respectively. The selective adsorption mechanism was elucidated by means of FT-IR, XPS, DFT, and MD. As the key for the selective adsorption, the N site in ZIF-67 dramatically promotes the coordination with Cu2+, while the adsorption for ILs mainly occurs via hydrogen bonding and van der Waals interactions with adsorption energies of –80.61 and –35.33 kcal/mol, respectively. The results demonstrate that this approach constitutes a feasible technique for the efficient separation of Cu2+ and ILs in the textile industry.