Acid Red 73 Removal By Chitosan/Ferrous Oxide Nanocomposite: Adsorption Behavior and Physicochemical Properties

This study investigates the efficacy of a chitosan/ferrous oxide nanocomposite (CFON) for the elimination of the dye Acid Red-73 (AR73) from aqueous solutions. Physicochemical characterization via Fourier transform infrared spectroscopy confirmed the presence of critical functional groups (e.g., O-H/N-H stretch at ~3419 cm⁻¹, C-N stretch at ~1399 cm⁻¹, and Fe-O bond at ~642 cm⁻¹) integral to dye binding. Scanning electron microscopy revealed an uneven, irregular surface morphology with constituent nanoparticles in the 16–19.8 nm range, providing a substantial surface area for adsorption, while energy dispersive X-ray spectroscopy validated the elemental composition, notably carbon (39.76%), oxygen (38.13%), nitrogen (2.87%), and iron (0.54%). Batch adsorption experiments demonstrated exceptional CFON performance, achieving over 99% AR73 removal under optimized conditions (pH, adsorbent dose [0.02–0.04 g], contact time [120–240 min], and initial dye concentration [20–60 mg/L]). The adsorption equilibrium data were best described by the Freundlich isotherm model (R² = 0.958; KF = 1.048; 1/n = 6.234), indicating favorable multilayer adsorption onto a heterogeneous surface. Response surface methodology (RSM) with a central composite design identified the quadratic effect of contact time and the interaction between contact time and solution pH as the most statistically significant factors (p < 0.05 based on Pareto chart analysis). KEYWORDS Industrial pigments, multilayer adsorption, nanocomposite, removal efficiency, surface methodology, water pollution