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Oxidation of benzoic acid was studied via Fenton-like reaction using an innovative supported 3,-FeOOH catalyst. The decomposition kinetics of hydrogen peroxide was investigated first. Oxidation of benzoic acid by hydrogen peroxide was performed to understand the effects of initial pH and hydrogen peroxide dosage. The treatment efficiency of benzoic acid at an initial pH of 3.2 was higher than at initial pHs of 6.0 and 10.0; this can be partly explained by reductive dissolution of ~,-FeOOH. Therefore, the extent of heterogeneous catalysis was evaluated. We found that the majority of oxidation occurred on the catalyst surface, with some occurred in the solution due to iron dissolution of the catalyst,

Oxidation of benzoic acid (BA) by H2O2 was performed with a novel supported gamma-FeOOH catalyst in a circulating fluidized-bed reactor (CFBR). This study focused mainly on determining the proportions of homogeneous catalysis and heterogeneous catalysis in this CFBR. Also studied herein was how pH, H2O2 concentration, and BA concentration affect the oxidation of BA. Experimental results indicate that the decomposition rate of H2O2 was proportional to its concentration and that the oxidation rate of BA depended on both H2O2 and BA concentrations. The change in the rate constant of heterogeneous catalysis by pH was described in terms of ionization fractions of surface hydroxyl group. From the mathematical deduction, we can infer thatthe reaction rate associated with ...Fe(III)OH2+ is markedly higher than that with ...Fe(III)OH. Conclusively, although heterogeneous catalysis contributes primarily to the oxidation of BA at pH 4.4-7.0, the homogeneous catalysis is of increasing importance below pH 4.4 because of the reductive dissolution of gamma-FeOOH.

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This study applied a novel electrochemical process called the Fered-Fenton method to treat a highly concentrated wastewater. By combining electrochemical reduction and chemical oxidation, the process can remove organic compounds and heavy metals in a batch reactor. A PVC-stabilizer processing wastewater was treated in this investigation owing to its high heavy metal concentration (Pb = 7,500 mg/l) and high organic concentration (COD = 11,000 mg/l). The major organic component was acetate. Direct anodic oxidation showed no effect on COD removal. Fenton's method only removed 36% of COD using 4,000 mg-Fe2+/l and 28,000 mg-H2O2/l dosage. In the Fered-Fenton process, about 89% of COD was removed with 2,000 mg-Fe3+/l and 28,000 mg-H2O2/l. Furthermore, the COD removal attained an efficiency of about 98% for 56,000 mg-H2O2/l used. Results presented herein demonstrate that the Fered-Fenton method is superior to direct anodic oxidation and Fenton's method in this case. Furthermore, the changes of the intermediate compounds including acetate, oxadate, and formate during the reaction were analyzed, which provided us with the information to propose degradation reactions of the wastewater in this system.

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The electro-Fenton method, in which ferrous ion is produced at the anode and used as a catalyst of H2O2, was applied for treating the bioeffluent of petrochemical manufacturing wastewater. The major pollutant in the bioeffluent was identified as hexamine, which was nonbiodegradable and contributed 65% of COD. The goal of this study was to treat the biotreatment effluent with more than 50% of COD removal efficiency. Oxidants that involved ozone, ozone/H2O2, sodium hypochlorite, and Fenton's reagent were employed to treat this effluent by jar tests. However, none could meet the goal in the range of operating conditions used. On the other hand, more than 80% of COD was removed with the electro-Fenton process. These screening tests indicated that only the electro-Fenton process was compatible with the goal.