Adsorption behaviour of congo red by cellulose/chitosan hydrogel beads regenerated from ionic liquid

A cellulose/chitosan hydrogel bead was prepared by extruding and regenerating the blends from ionic liquid 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) in ethanol. FT-IR, scanning electron microscopy (SEM) and X-ray powder diffraction techniques were used to prove the successful blending of both natural polymers (cellulose and chitosan). Brunauer–Emmet–Teller surface area and pore diameter analysis showed that the beads were nanoporous with pores measuring from 10 to 20 nm. Batch adsorption experiments demonstrated that the bead had a maximum adsorption capacity of 40 mg/g for congo red (CR) dye removal from aqueous solutions, which was more efficient than the most reported natural biosorbents. The CR adsorption capacity at equilibrium was related to initial CR concentration, dosage of beads and pH values of the CR solution. When the initial concentration of CR was 30 mg/L, and the adsorbent dosage was 2.0 g/L, the equilibrium of adsorption was reached within 115 min with the removal rate of 89.6%. The Langmuir model represented the adsorption isotherm data and the experimental results followed a pseudo-second-order rate model, indicating that intraparticle diffusion dominated the adsorption process. The cellulose/chitosan hydrogel beads can be used as an efficient adsorbent for dye contaminant removal from wastewater.