<p>Phenol is a toxic and persistent priority pollutant commonly found in industrial effluents. In this study, we developed a functionalized silica aerogel composite reinforced with recycled PET fibers and surface-modified with chitosan and FeCl₃ for the rapid removal of phenol from aqueous solutions. Under optimized conditions (pH 7, 25&#xa0;min contact time, 0.1&#xa0;g adsorbent in 60&#xa0;mL solution), the composite removed 98% of phenol and exhibited a maximum adsorption capacity of 51.02&#xa0;mg&#xa0;g⁻¹. Equilibrium data were best described by the Freundlich isotherm (R² = 0.96), indicating multilayer adsorption on a heterogeneous surface. Kinetic analysis revealed rapid uptake, with intraparticle diffusion plots exhibiting multilinearity and a nonzero intercept (C ≈ 3.64&#xa0;mg·g⁻¹), indicating that both film diffusion and pore diffusion contribute to the rate control. Although both pseudo-first-order and pseudo-second-order models fit the kinetic data well (R² ≈ 0.99), mechanistic evidence supports a physisorption-dominant mechanism with minor electrostatic and hydrogen-bond contributions involving Fe³⁺ and chitosan functional groups, for which the pseudo-second-order model is considered more representative which is confirmed by the Freundlich isotherm (R² = 0.96) and the low Temkin heat (b ≈ 135 J·mol⁻¹). Thermodynamic calculations yielded ΔH° = + 31.76&#xa0;kJ·mol⁻¹ and negative ΔG° values over the studied temperature range, indicating a spontaneous and endothermic adsorption process. The composite’s rapid kinetics, good regeneration performance, and use of recycled PET suggest promise for practical, sustainable phenol remediation applications.</p> Graphical abstract <p></p>