Removal of Azo Dyes Orange II and Reactive Black 5 from Aqueous Solutions by Adsorption on Chitosan Beads Modified with Choline Chloride: Urea Deep Eutectic Solvent and FeO

The removal of the azo dyes Orange II (OII) and Reactive Black 5 (RB5) from aqueous solutions was studied using three types adsorbents derived chitosan: unmodified chitosan beads (un-Ch), tuned with a deep eutectic solvent (DES) composed choline chloride:urea at 1:2 molar ratio (Ch-DES), along FeO nanoparticles added to modified DES (Ch-FeO-DES). Both were effectively removed in 3–4 h when Ch-DES used, dye concentration range 25–50 mg/L. modification improved efficiency achieve increases around 32% for OII 17% RB5. adsorbent dosage initial influenced adsorption process. Isotherm models (Langmuir, Freundlich, Temkin) kinetic (pseudo-first-order, pseudo-second-order, intraparticle diffusion, Elovich models) applied identify behavior. process could be characterized by employing pseudo-second-order model fitting it monolayer Langmuir isotherm. occurred on no interaction among molecules electrostatic forces would determine attaching adsorbent. efficiently desorbed an alkaline solution, while RB5 more strongly attached. recycled, after regeneration acid least reuse cycles still achieving effective removal. Reactivation diluted EDTA solution allowed authors recycle RB5-attached beads, optimum two further uses.