What happens when chitosan meets bentonite under microwave-assisted conditions? Clay-based hybrid nanocomposites for dye adsorption

Abstract

In this study, bionanocomposites were prepared with bentonite and chitosan in proportions of 50, 100, 200, and 300 % of the cation exchange capacity (CEC) of the bentonite using microwave heating at 50 °C for 15 and 30 min. The X-ray diffraction patterns indicated basal spacings in the range of 1.48–2.10 and 1.57–1.98 nm for nanocomposites obtained at 15 and 30 min of heating, respectively, suggesting the intercalation of chitosan in the interlayer space of montmorillonite. Fourier transform infrared spectra confirmed the incorporation of chitosan in bentonite. The results of the elemental analysis suggested a higher chitosan content for the nanocomposites prepared with 200 and 300 % of the CEC after 30 min of irradiation. Chitosan–bentonite nanocomposites obtained after 30 min of heating successfully adsorbed the Reactive Violet 5R dye from aqueous solutions. The influence of several factors such as the pH, adsorbent dosage, contact time, and initial dye concentration was investigated. The optimal adsorption conditions were a pH of 1.0 and a contact time of 20 min. The adsorption capacity reached 98.00, 207.71, 250.00, and 282.01 mg g−1 for nanocomposites prepared with 50, 100, 200, and 300 % of the CEC, respectively. In was demonstrated that the prepared bentonite–chitosan nanocomposites were good dye adsorbents.