Mesoporous chitosan/activated charcoal powder and bead modified in 1-butyl-3-methylimidazolium acetate for the adsorption of acid blue 25 from an aqueous solution

BACKGROUND A green synthesis approach involving 1-butyl-3-methyl imidazolium acetate (BmimA) medium was utilised to prepare mesoporous chitosan/activated charcoal composite powder (ChA) and bead (ChB) for the removal of acid blue 25 (AB25) dye from aqueous solution. The composite's characteristics were examined using Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis, X-ray diffraction and Brunauer-Emmett-Teller (BET) analysis. The influence of initial concentration of the dye, pH, contact time and adsorbent dosage on the adsorption and the composite's stability in acidic and basic solutions was also examined. RESULTS FTIR revealed that chitosan and activated charcoal were connected through O -H, N - H, C-O and CO, while AB25 adhered to ChA and ChB through the hydroxyl and amino functional groups. SEM images of ChA and ChB revealed rough-like surfaces with randomly distributed pores. BET analysis revealed that ChA and ChB are mesoporous, with pore sizes of 2.18 and 2.26 nm. The composites were stable in acidic and basic solutions, and adsorption of AB25 onto the adsorbents was more effective at pH 2. Regeneration of the adsorbents was also influential in NaOH solution. The amount of BmimA used in the composite's preparation has limited influence on the effectiveness of ChA and ChB for AB25 uptake. The adsorption is best described by Langmuir isotherm in both ChA and ChB with q(max) of 3030.3 and 3703.7 mg g(-1) respectively, although ChB also conforms to the Freundlich isotherm. The adsorption kinetics fitted well into the pseudo-second-order model. CONCLUSION The prepared modified chitosan/activated charcoal powder and bead were able to adsorb the AB25 dye better than other chitosan-based materials. (c) 2022 Society of Chemical Industry (SCI).