Photocatalytic degradation of p-chlorophenol by hybrid H2O2 and TiO2 in aqueous suspensions under UV irradiation

• The hybrid H2O2/TiO2/UV process could enhance photodegradation of p-chlorophenol.
• Photodegradation of p-chlorophenol under UV irradiation well followed the L–H model.
• The apparent rate constant nearly double increases compared to the absence of H2O2.
• TiO2 dose should be optimized before selection of other variables in photocatalysis.

In this study, TiO2 particles were used as photocatalysts for the degradation of aqueous p-chlorophenol (p-CP) under UV irradiation. The effect of TiO2 dose (0–3 g/L), initial p-CP concentration, H2O2 concentration (2–45 mM), solution pH (4.6–9.5), and UV light intensity on the degradation of p-CP were examined. Four oxidative degradation processes, which utilized UV alone (direct photolysis), H2O2/UV, TiO2/UV, and H2O2/TiO2/UV, were compared in a batch photoreactor with a 100-W high-pressure mercury lamp. The photodegradation of p-CP could be described by the pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. Moreover, the apparent degradation rate constants increased considerably from 3.5 × 10−3 min−1 (direct photolysis) to 19.9 × 10−3 min−1 (H2O2/TiO2/UV system).