Fenton Pretreatment in the Catalytic Wet Oxidation of Phenol

Catalytic wet oxidation (CWO) of 1000 mg/L of phenol (PhOH) aqueous solutions has been carried out using a commercial activated carbon as catalyst, placed in a continuous three-phase reactor at 16 bar, and temperature was changed in the interval 127-160 degrees C. Pure oxygen was fed as gaseous phase. Pollutant conversion, mineralization, intermediate distribution, and toxicity were measured at the reactor exit. The catalyst weight (W) to liquid flow rate (Q(L)) ratio was varied from 0.3 to 17.5 g(AC)min/mL. Fenton reagent (FR) has been applied to the same phenolic aqueous samples using different amounts of H2O2 (between 10 and 100% of the stoichiometric dose) and 10 mg/L of Fe2+, in a batch way at 50 degrees C. An integrated process has been proposed that combines FR as pretreatment of the CWO process. In the FR step, 10% of H2O2, 10 mg/L of Fe2+, and reaction times shorter than 40 min are used. Efluent from FR step is fed to the CWO reactor at 127 degrees C. High mineralization (80-90%) and total detoxification of the effluent was obtained at the reactor exit using W/Q(L) values lower than 10 g.min/mL. Therefore, the FR pretreatment enhances remarkably the efficiency of the CWO at moderate temperature conditions.