Treatment of recalcitrant organic silicone wastewater by fluidized-bed Fenton process

• The organic silicone wastewater was treated by FB-Fenton using three kind carriers.
• Quartz sand was chosen as optimum carrier due to its better performance.
• Optimum conditions were obtained to treat wastewater by orthogonal experiments.
• FB-Fenton was better in oxidation and Fe3+ utilization than traditional Fenton.

To achieve an enhanced degradation of recalcitrant organic silicone wastewater in the fluidized-bed Fenton process was attempted using three different carrier substrates [quartz sand, brick particles and granular activated carbon (GAC)]. Quartz sand was determined as the best carrier substrate due to better reactor bed expansion, fluidized state and pollutant removal rate than the brick particles and GAC. The iron oxide components such as FeOOH, FeO, Fe2O3, and Fe3O4 were found on the surface of coated quartz sand using X-ray diffraction (XRD) analysis. The optimal hydraulic retention time (HRT) of 60 min was determined based on COD and TOC removal rate. Further, the optimal operating conditions of pH 3.5, H2O2/COD (mass ratio) 2.6:1, H2O2/Fe2+ (molar ratio) 13.6:1 and quartz sand filling rate of 35% were determined by the orthogonal experiments for the recalcitrant treatment. In the fluidized-bed Fenton process treated effluent COD value was 40 mg/L and TOC value was 20 mg/L, with a removal rate of 95% and 85%, respectively. Compared to the traditional Fenton process the COD and TOC removal rates were found to increase by 20% and 15% respectively. Furthermore, the total iron removal rate was higher than conventional Fenton process, which significantly reduced the iron concentration in effluent.