A two-level factorial design for calcium cobaltite doped scandium/chitosan films composite in pharmaceutical wastewater photocatalytic degradation.

The photocatalytic decomposition of naproxen, a widely used nonsteroidal anti-inflammatory drug, in aqueous wastewater was investigated using Ca₃Co₄O₉ and Sc-doped Ca₃Co₄O₉/chitosan nanocomposite films under visible-light irradiation. Chitosan, extracted from shrimp shells, was employed as a sustainable immobilization matrix for the synthesized photocatalysts. Ca₃Co₄O₉ and Sc-doped Ca₃Co₄O₉ photocatalysts were prepared via the Pechini method. The structural, morphological, and optical properties of the fabricated nanocomposites were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and optical analyses. Naproxen was selected as a representative pharmaceutical contaminant to evaluate the photocatalytic efficiency of the developed nanocomposite films. A naproxen removal efficiency of 95% was achieved using the chitosan/Ca₃Co₃.₉₉Sc₀.₀₁O₉ nanocomposite film, and the photodegradation process followed pseudo-first-order kinetics. To elucidate the photocatalytic degradation mechanism of naproxen under light irradiation, the dominant reactive species involved in the (50/50) chitosan/Ca₃Co₃.₉₉Sc₀.₀₁O₉ nanocomposite film were systematically investigated. This was accomplished by introducing specific scavengers into the degradation system to quench superoxide radicals (O₂•⁻), photo-generated holes (h⁺), and hydroxyl radicals (•OH). In real pharmaceutical wastewater samples, the removal efficiencies of chemical oxygen demand (COD), biological oxygen demand (BOD), and total organic carbon (TOC) exceeded 85%. Furthermore, the nanocomposite film exhibited good reusability, retaining significant photocatalytic activity after five consecutive cycles, with only a 10% reduction in efficiency. A two-level factorial design was applied to evaluate the effects of the selected variables, with model validation and interpretation supported by diagnostic plots such as perturbation plots, analysis of variance (ANOVA), and Pareto charts.