Post-treatment of real oil refinery effluent with high concentrations of phenols using photo-ferrioxalate and Fenton's reactions with membrane process step

Post-treatment using photo-ferrioxalate and Fenton's reaction from a real oil refinery effluent with high concentrations of phenols (200 mg/L) were evaluated as alternative processes to simultaneously reduce the chemical oxygen demand (COD), phenols, and others pollutants contained in petroleum refinery wastewater. An ultrafiltration hollow fiber membrane was used to treat the effluent from advanced oxidation processes (AOPs). The effect on COD and phenol removal caused by the concentration of oxalate, Fe2+, H2O2, and pH was evaluated. For photo-ferrioxalate reaction, the higher removals of COD (84%) and phenol (100%) were obtained with concentrations of 200 mg/L of oxalate, 20 mg/L Fe2+, and 500 mg/L of H2O2, and a pH 5. A 55% removal of COD and a 100% removal of phenol were generated by Fenton's reaction with concentrations of H2O2 and Fe2+ of 300 and 20 mg/L, respectively, and a pH 4. The reaction time in both AOPs was 120 min. The reaction rate (k) during photo-ferrioxalate reaction was 0.021 for COD and 0.040 min−1 for phenol. Fenton's reaction k for COD was 0.0001 L/mg min and phenol was 0.22 min−1. After the treatment with photo-ferrioxalate reaction, the treated wastewater was transferred to an ultrafiltration hollow fiber module, which pressure rate was between 8.8 and 18.5 psi (8.8 and 38 mL/min). Removal efficiencies of 66.3% for COD and >99% for TSS were obtained during the ultrafiltration membrane test. The final concentrations of COD, phenol, sulfides, TSS, turbidity, and color, after a photo-ferrioxalate-ultrafiltration membrane treatment, were 22 mg/L (total removal 94%), <0.5 mg/L, <0.2 mg/L, <1 mg/L, 2 NTU and 254 Pt-Co, respectively.