Chitosan–poly(vinyl alcohol)–ionic liquid-grafted hydrogel for treating wastewater

Abstract

A chitosan–poly(vinyl alcohol)–ionic liquid-grafted hydrogel was prepared for water purification. The hydrogel was characterized using various techniques, including nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The swelling properties of the hydrogels were optimized by varying the solvent, pH, time, and temperature. The maximum swelling of the hydrogel was 330%. The hydrogel absorbed dye, nitrite, and Pb²⁺, with removal rates of up to 97% for dye and 88% for Pb²⁺. The hydrogel could effectively recover oil from an oil–water mixture, where the removal mechanism was predominantly attributed to electrostatic interactions between the cationic hydrogel and the dye, Pb²⁺, and nitrite anions. The hydrogel was biodegradable, making it environmentally friendly.