Degradation of 1,2-dichloroethane by photocatalysis using immobilized PAni-TiO₂ nano-photocatalyst

1,2-Dichloroethane is one of the most hazardous environmental pollutants in wastewaters. It is mainly used to produce vinyl chloride monomer, the major precursor for PVC production. It is determined to be a probable human carcinogen and has been listed as a priority pollutant by the United States Environmental Protection Agency. Due to high chemical stability and low biodegradability of 1,2-dichloroethane, heterogeneous photocatalysis was used for degradation of this chlorinated hydrocarbon. PAni-TiO₂ nanocomposite was synthesized by in situ deposition oxidative polymerization method and immobilized on glass beads by a modified dip coating and heat attachment method. The characteristics of synthesized PAni-TiO₂ nanoparticles were confirmed using the results of morphology tests including Fourier-transform infrared spectra, X-ray diffraction patterns, particle size analysis, UV-Visible spectrophotometer, scanning electron microscope, and energy-dispersive X-ray spectroscopy. The performance of photocatalytic degradation of 1,2-dichloroethane using synthesized PAni-TiO₂ nanocomposite in a designed and constructed pilot scale packed bed recirculating photocatalytic reactor under xenon light irradiation was investigated. The response surface methodology based on the central composite design was used to evaluate and optimize the effect of 1,2-dichloroethane concentration, residence time, pH, and coating mass as independent variables on the photocatalytic degradation of 1,2-dichloroethane as the response function. Results showed that actual and predicted results were well fitted with R² of 0.9870, adjusted R² of 0.9718, and predicted R² of 0.9422. The optimum conditions for 1,2-dichloroethane photocatalytic degradation were the 1,2-dichloroethane concentration of 250 mg/L, the residence time of 240 min, pH of 5, and coating mass of 0.5 mg/cm², which resulted in 88.84% photocatalytic degradation. Kinetic of the photocatalytic degradation at optimal condition follows the Langmuir-Hinshelwood first-order reaction with k = 0.0095 min^-1 with R² = 0.9455. Complete photocatalytic degradation of 1,2-DCE was achieved after 360 min.