Fe3O4 nanoparticles loaded with citrus pomace extract: a magnetic sustainable nanoadsorbent for enhanced removal of Reactive Yellow 145 from textile effluents.

This study reports the green synthesis of magnetic iron oxide nanoparticles (Fe₃O₄@CP-NPs) using citrus pomace extract as a natural stabilizing and coating agent. Structural and surface characterizations (FE-SEM, XRD, EDX, UV-Vis, FTIR, and VSM) confirmed the successful formation of Fe₃O₄ nanoparticles with functional groups from the extract bound to their surface. Adsorption performance was evaluated using Reactive Yellow 145 (RY145), a representative azo dye pollutant. Batch experiments examined the effects of dye concentration, adsorbent dosage, pH, contact time, and temperature. Under optimal conditions (3.6 g/L dosage, pH 5, 250 mg/L dye), Fe₃O₄@CP-NPs achieved a maximum adsorption capacity of 192.49 mg/g. Equilibrium data were best fitted by the Toth isotherm (R² = 0.999), while adsorption kinetics followed a pseudo-second-order model. Thermodynamic parameters confirmed a spontaneous, exothermic process. Regeneration with NaOH enabled 99.12% dye desorption, with high reusability over several cycles. Notably, a preliminary cost estimation showed that large-scale synthesis could be achieved at ∼0.036 US$/g, underscoring its economic competitiveness compared with conventional adsorbents. This is the first report on the valorization of citrus pomace for producing high-performance magnetic nanoadsorbents for azo (-N = N-) dye removal, highlighting both scientific novelty and environmental relevance.