Study of adsorption efficiencies of biopolymer-based composites of chitosan with a sulfonic acid functionalized imidazolium ionic liquid for elimination of organic dyes in wastewater†

In the present work, Brønsted acidic ionic liquid 2-methyl-N,N-disulfoimidazolium chloride [Mdsim]Cl impregnated chitosan composites were prepared by mixing chitosan with [Mdsim]Cl in different ratios. The prepared composites were characterized by FT-IR, PXRD, SEM and TGA techniques. The adsorption behaviour of the prepared composites was efficiently investigated for the removal of methylene blue (MB), as a cationic model dye compound from aqueous solution. Various concentrations of aqueous MB dye solutions were used to study the adsorption nature of composites through UV studies. The adsorption kinetics of MB was well described using a pseudo-second-order model and intra-particle diffusion model. The adsorption also followed the Langmuir adsorption isotherm and the maximum adsorption capacity was 2.3 mg g⁻¹ among the prepared composites. The adsorption capacity of the composite was also compared with three other dyes, namely methyl orange, crystal violet and methyl green.