Design and fabrication of continuous flow fixed-bed photoreactor to photocatalytic degradation of oil-well produced water using conductive photocatalytic fibers

Abstract

Fixed-bed photocatalytic reactors with both batch and continuous flow designs were developed for the efficient treatment of oil-well produced water (OWPW). A novel three-part composite photocatalyst, MIL-101(Cr)/Fe3O4-SiO2/nano-rod-GCN, was synthesized with a high surface area (653 m2/g), a narrow visible light band gap (1.6 eV), and effective charge separation through a Z-scheme mechanism, enabling strong generation of active radicals for pollutant degradation. The photocatalytic nanoparticles were immobilized on conductive electrospun polystyrene/polyaniline fibers at various weight loadings (20, 35, 55, and 70 %). In the batch system, the fluidized three-part composite achieved a COD removal efficiency of 94.4%, while the bare polystyrene/polyaniline fibers showed only 35.7% COD adsorption under the same conditions. Immobilizing the nanoparticles onto the fibers enhanced the COD removal to 97.6%, due to the synergistic effects of hydrophobic adsorption and in-situ photocatalytic degradation. In the fixed-bed continuous flow system, under optimized conditions (solution pH 4.5, flow rate 2 mL/min, light intensity 18 W/m2, and initial COD of 700 mg/L), the stabilized photocatalyst achieved a COD removal efficiency of 92.5 %. The innovative fixed-bed continuous flow photoreactor demonstrated high and consistent performance in both adsorption and degradation, demonstrating promising applicability for real-world treatment of produced water. © 2025 Elsevier B.V.