The Study On The Degradation Of Simulated Phenol By Iron Oxide Catalytic Ozonation

Catalytic ozonation of phenol in aqueous solution was compared among iron oxides catalyst such as FeOOH, Fe2O3 and Fe3O4 with and without nanosizes. The catalysts were characterized by X-ray diffraction(XRD), The-Brunauer-Emmett-Teller(BET) and scanning electron microscope(SEM). Under the conditons of an initial phenol concentration of 1 mmol/L, a p H of 3.0, a catalyst dose of 1 g/L; O3/O2 flux of 200 ml/min(corresponding to an O3 concentration of 42.38 mg/L in mixed gas), the Fe3O4 NPs catalyst exhibited the highest catalytic activity towards phenol with up to 80.0% of total organic carbon(TOC) after 180 min reaction. It was concluded that greater BET surface resulted in higher reaction rate. Further determination of Fe2+ concentration in reaction solution showed that Fe2+ leached from Fe3O4 NPs, Fe2O3 NPs and Fe3O4 increased gradually as a function of time, and reached 4.49 mg/L, 0.9 mg/L and 0.78 mg/L after 240 min, respectively. In contrast, Fe2+ concentration in reaction solution was very low for the other iron oxides catalyst. Catalytic ozonation degradation of phenol follows a kinetics model of(-d[TOC]/dt=[TOC]t/(a+bt)),which can be simplified a Pseudo-first-order under certain conditions. For example, the TOC decrease using Fe3O4 NPs contained an initial slow induction period(rate constant 3.3×10-3 min-1) and a sequenced rapid degradation period(rate constant 8.82×10-3 min-1). The effect of several operating parameters such as ozone dose, the amount of added Fe3O4 NPs and temperature on the removal of TOC was investigated. The removal rate of TOC was increased following the addition of ozone dose, catalyst dose and temperature, respectively. Experimental results showed that the ozonation process was effective for degradation of phenol, and TOC can be removed up to 80.0% after 180 min treating with O3/O2 flow of 200 ml/min at pH value of 3.0 and temperature of 25℃. On the basis of analyzing the intermediate products by Gas Chromatography-Mass Spectrometer(GC-MS) and the assuming that hydroxyl radicals ·OH are the major reactive species, a possible pathway of phenol degradation was proposed during the catalytic ozonation process using Fe3O4 NPs as iron source.