Functionalized cross-linked chitosan with ionic liquid and highly efficient removal of azo dyes from aqueous solution

In this study, a new ionic liquid functionalized cross-linked chitosan (IL-CCS) was prepared and utilized as an adsorbent for removing sunset yellow FCF (SY) from aqueous solutions. The physicochemical properties of the adsorbent were characterized using infrared spectroscopy (IR), scanning electron microscope (SEM), nitrogen adsorption-desorption isotherms and thermogravimetric analysis (TG). The effects of the experimental parameters such as initial pH, the adsorbent dose and contact time on the absorption process of SY on IL-CCS were investigated in detail. The results showed that the adsorption capacity of IL-CCS for SY had no significant differences when pH of the solution changed from 2.0 to 10.0, and the maximum adsorption capacity of IL-CCS was 300.28 mg/g, obviously higher than that of CCS (36.08 mg/g). In addition, the results of adsorption isotherm, kinetic and thermodynamics showed that the adsorption process could fit with Langmuir model, pseudo-second order model, separately. The exothermic nature of the reaction was revealed through thermodynamic parameters. From the above, IL-CCS has a good prospect for treatment of wastewater containing anionic dyes due to high efficiency adsorption during a broad pH range.