Dependency on some operating parameters during wet oxidation of phenol by hydrogen peroxide with Fe-ZSM-5 zeolite

Wastewater originating in the chemical process industries contain high conc entrations of organics that must be treated before discharge. Phenol is one of the most important of these pollutants because it is toxic, even at low concentrations. Recently, hydrogen peroxide treatment has emerged as a via ble alternative oxidation technique for treatment. It does not form any har mful or intrusive by-products and it is an ecologically dean and non-toxic chemical; However, the methods for treatment of wastewater with hydrogen pe roxide are based mostly on homogeneous catalysis by metal ions inducing add itional pollution. From this,it was anticipated that the use of heterogeneo us catalysis would be a good alternative thus opening up a new field of inv estigation. Previous studies, based on screening tests, evidenced the catal ytic activity of an MFI zeolite Fe-ZSM-5 for phenol elimination by H2O2. Th e oxidation tests are carried out in a batch mode, using a stirred glass re ader. The influence of pH, temperature and H2O2 stoichiometric ratio on the phenol oxidation rate with Fe-ZSM-5 is studied. The temperature is below 1 00 degrees C in order to avoid pressurization of the treatment reactor. Usi ng a H2O2 stoichiometric ratio equal to 1.5 avoids accumulation of any quin one-like by-products;Under these conditions, the catalytic system H2O2/Fe-Z SM-5 allows a total elimination of phenol and a significant TOC removal (50 %) without leaching-off more than 1 ppm of Fe (III) ions. At the end of the reaction period, only carboxylic adds (maleic, fumaric, oxalic, acetic, ac cumulate. These latter should not be considered as a drawback of this proce ss. The chemical oxidation process would be used only as a detoxification s tep and such compounds could be treated with a biological process, in a sec ond step.