Successive Removal of Methylene Blue and Congo Red by Biomass-Based Beads from Aqueous Solutions

In this study, cryogel beads have been successfully prepared, for the first time, from reed stems dissolved in 1-butyl-3-methylimidazolium chloride (BmimCl). Beads diameters were in the 1.8–2 mm range. The adsorption capacity of biomass-based beads was evaluated against cationic (Methylene blue) and anionic (Congo red) dyes. Adsorptive properties of Reed-based beads (BR) were tested as a function of pH (2–10), contact time (30–240 min), adsorbent mass (0.25–1.5 g/L), and initial dye concentrations (50–150 ppm) and characterized with FTIR spectroscopy analyses. The adsorption capacities for Methylene blue and Congo red were 58.3 mg/g and 36.15 mg/g, respectively. The kinetic of successive Methylene blue and Congo red dyes adsorption onto BR was best described by the pseudo-second-order model.