Removal of 1-Butyl-3-methylimidazolium bromide from an aqueous solution by using a spongy chitosan-activated carbon composite

This study reports the potential of chitosan-activated carbon composite (CH-AC) on the removal of hydrophilic imidazolium-based ionic liquid from aqueous solution. 1-Butyl-3-methylimidazolium bromide, [BMIM][Br] one of the mostly applied hydrophilic imidazolium-based ILs was selected for this study. The CH-AC was characterised using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR). The effect of adsorption experimental conditions like initial concentration, pH, contact time and adsorbent dosage were examined, and the change in [BMIM][Br] concentration for the uptake process was monitored. The micrograph of CH-AC revealed an irregular shaped stone-like material held on rough surface which differ in surface morphology from the precursor used for preparing the composite. Distinct peaks were observed on XRD pattern of CH-AC at various 2 circle minus suggesting the intercalation of AC into chitosan. The disappearance of characteristic peak of chitosan at 10 degrees on CH-AC was attributed to interruption of the crystalline region. The experimental data analysed using Langmuir and Freundlich isotherms fitted best into Langmuir model. The CH-AC applied on [BMIM][Br] removal give adsorption capacity of 12.17 mg/g (0.056 mmol/g) as calculated from Langmuir model. The adsorption kinetics fitted into pseudo-second order model.