Development of β-Cyclodextrin-Cellulose/Hemicellulose-Based Hydrogels for the Removal of Cd(II) and Ni(II): Synthesis, Kinetics, and Adsorption Aspects

Carboxymethyl cellulose (CMC), microcrystalline cellulose (MCC), and xylan are cross-linked with beta-cyclodextrin (beta CD) using ethylene glycol diglycidyl ether cross-linker to produce hydrogels, namely, beta CD-CMC, beta CD-MCC, and beta CD-xylan, in alkaline medium at 1:1 mole ratio. Additionally pure beta CD gel is also prepared in alkaline medium. The synthesized hydrogels are characterized by Fourier transform infrared spectroscopy, and the swelling ratio, gel fraction, and the morphologies are observed by a microscope. The hydrogels are used to adsorb cadmium (Cd(II)) and nickel (Ni(II)) ions from aqueous solution. The adsorption studies are carried out by varying adsorbent dosage from 80 to 500 mg, concentration from 5 to 500 mg L-1, pH from 2 to 8, and temperature from 25 to 55 degrees C. The equilibrium adsorption data closely follow the Langmuir model, suggesting the monolayer adsorption of metal ions by the hydrogels. The adsorption kinetics are found to closely follow the pseudo-second-order model.