Adsorption of dyes from aqueous solutions using chitosan-based materials functionalized with ionic liquids: Acid...

A novel dye adsorbent, ILCS-CS-Glu, was developed by grafting the ionic liquid [C₈MIMBr]Br onto a chitosan (CS) matrix, blending it with unmodified CS, and crosslinked with glutaraldehyde. The resulting composite material combines the structural advantages of biopolymer CS and the permanent charged and functionality of IL moieties. ILCS-CS-Glu exhibited a high maximum adsorption capacity of 292 mg g^-1 for the anionic dye Acid Orange 7 (AO7). It maintained high adsorption efficiency (>90%) across a wide pH range (3-9) and demonstrated excellent tolerance ionic strength variations (up to 1.0 M NaCl), outperforming neat CS and other CS-based absorbents (CS-TPP and CS-PIL). Kinetics studies showed that adsorption followed a first-order model (k = 0.022 min^-1) with an equilibrium time of approximately 140 min. Isotherm analysis indicated Langmuir-type behavior, and desorption experiments confirmed dye recovery using NaOH solutions. Regeneration tests demonstrated that ILCS-CS-Glu retained significant adsorption capacity over multiple adsorption-desorption cycles, exhibiting strong operational stability even under neutral pH and high salinity conditions. Importantly, application tests using textile industrial effluent validated the adsorption performance of ILCS-CS-Glu, achieving dye removal efficiencies of up to 83%. These results highlight the potential of ILCS-CS-Glu as a sustainable, pH-independent, and scalable adsorbent for effective dye removal in textile wastewater applications.