Enhancement of UV-assisted TiO₂ degradation of ibuprofen using Fenton hybrid process at circumneutral pH

A synergistic UV/TiO₂/Fenton (PCF) process is investigated for the degradation of ibuprofen (IBP) at circumneutral pH. The IBP decay in the PCF process is much faster than that with the conventional UV, UV/H₂O₂, Fenton, photo-Fenton, and photocatalysis processes. The kinetics analysis showed that the IBP decay follows a two-stage pseudo-first order profile, that is, a fast IBP decay (k₁) followed by a slow decay (k₂). The effects of various parameters, including initial pH level, dosage of Fenton's reagent and TiO₂, wavelength of UV irradiation, and initial IBP concentration, are evaluated. The optimum pH level, [Fe²⁺]₀, [Fe²⁺]₀/[H₂O₂]₀ molar ratio, and [TiO₂]₀ are determined to be approximately 4.22, 0.20 mmol/L, 1/40, and 1.0 g/L, respectively. The IBP decay at circumneutral pH (i.e., 6.0-8.0 for wastewater) shows the same IBP decay efficiency as that at the optimum pH of 4.22 after 30 min, which suggests that the PCF process is applicable for the treatment of wastewater in the circumneutral pH range. The lnk₁ and lnk₂ are observed to be linearly correlated to 1/pH₀, [IBP]₀, [H₂O₂]₀, [H₂O₂]₀/[Fe²⁺]₀ and ln[TiO₂]₀. Mathematical models are therefore derived to predict the IBP decay.