Kinetics and thermodynamics of photocatalytic degradation of organic pollutants in petroleum refinery wastewater over nano-TiO2 supported on Fe-ZSM-5

• We report the results of kinetic and thermochemical studies for PRWW photocatalysis.
• Apparent first-order rate of photocatalyst was determined.
• Langmuir–Hinshelwood was used for the kinetics of the degradation reaction of PRWW.
• The Arrhenius and transition state models were fitted to the experimental data.
• Ea, Δ‡Go, Δ‡Ho and Δ‡So values for TiO2/Fe-ZSM-5 were determined.

The photocatalytic degradation of organic pollutants in a real petroleum refinery wastewater (PRWW) by a heterogeneous photocatalytic process using synthesized nano-TiO2 supported on Fe-ZSM-5 zeolite as photocatalyst irradiated with UV light has been studied. The influence of various operational parameters such as photocatalyst concentration, pH and temperature was investigated. The degradation rates of the organic pollutants followed mainly a pseudo-first order kinetic model. Results showed that the maximum photodegradation efficiency was achieved at a photocatalyst concentration of 3 g/l, pH of 4 and temperature of 45 °C under UV irradiation time of 120 min. TiO2 loaded with the existence of oxo-iron ions in the framework of zeolite increased photocatalytic degradation of COD. The kinetics of photodegradation reaction was accelerated by an increase in temperature in the range of 15–45 °C. The activation energy for photocatalytic degradation of organic pollutants in PRWW was 18.76 kJ/mol. Thermodynamic parameters of activation were assessed in the photodegradation process. Kinetics computation using transition state theory (TST) showed that the temperature had a significant effect on the rate constants during the photocatalytic degradation process. Significant photodegradation efficiency of organic pollutants using the synthesized photocatalyst indicates a good potential for this technique as a treatment system for real PRWW.

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