Experimental and modeling analyses of COD removal from industrial wastewater using the TiO₂-chitosan nanocomposites

In the present study, titanium oxide (TiO₂) nanoparticles, chitosan, and several nanocomposites containing different mass dosages of TiO₂ and chitosan have been applied as the adsorbent for COD removal from the industrial wastewater (Bouali Sina Petrochemical Company, Iran). The FESEM, XRD, and FTIR tests have been employed to characterize TiO₂ nanoparticles, chitosan, and fabricated nanocomposites. Then, the effect of adsorption parameters, including TiO₂-chitosan mass ratio (1:1, 1:2, and 2:1), adsorbent content (0.25-2.5 g), temperature (20-50 °C), pH (3-11), solution volume (100-500 mL), and contact time (30-180 min) on the COD reduction has also been monitored both experimentally and numerically. The Box-Behnken design of the experiment approves that TiO₂-chitosan (1:1), adsorbent content of 2.5 g, temperature = 20 °C, pH 7.4, solution volume of 100 mL, and contact time = 180 min are the condition that maximizes the COD removal (i.e., 94.5%). Moreover, the Redlich-Peterson and Pseudo-second order models are the best isotherm and kinetic scenarios to describe COD removal's transient and equilibrium behaviors. The maximum monolayer COD adsorption capacity of the TiO₂-chitosan nanocomposite is 89.5 mg g^-1. The results revealed that the industrial wastewater COD is better to remove using the TiO₂-chitosan (1:1) at temperature = 20 °C.