Removal of ionizable aromatic pollutants from contaminated water using nano γ-Fe2O3 based magnetic cationic hydrogel: Sorptive performance, magnetic separation and reusability

Acid dyes found in textile industrial effluents are hazardous aromatic pollutants which ionize in aqueous environments. Owing to their non-biodegradability, conventional wastewater treatment processes are not able to remove them and sorptive treatment systems can alternatively be employed. In this study, a nano γ-Fe2O3 based magnetic cationic hydrogel, synthesized through a facile method, was applied for the removal of two acid dyes (Acid Red 27 and Acid Orange 52). The sorption performance (e.g., capacity and kinetics) and solution matrix effects (e.g., pH and competing anions) were investigated. Furthermore, different regeneration conditions (e.g., composition, strength and amount) were tested to develop a suitable regeneration strategy, based on which, reusability of the material was investigated for 30 consecutive sorption-desorption cycles. The material exhibited a rapid sorption rate (99% dye removal within 5 min) and sorption isotherm data agreed well with the Langmuir model with an estimated maximum capacity of 833 mg/g and 1430 mg/g for Acid Red 27 and Acid Orange 52, respectively. The high sorptive performance persisted not only over a wide pH range but also over 30 consecutive rounds of sorption-desorption. Moreover, the impregnated γ-Fe2O3 nanoparticles rendered the hydrogel superparamagnetic allowing its convenient magnetic separation.