Oxytetracycline removal and E. Coli inactivation by decomposition of hydrogen peroxide in a continuous fixed bed reactor using heterogeneous catalyst

Abstract

Fenton oxidation with heterogeneous hematite catalyst in a fixed bed reactor was investigated for water disinfection. The granulated hematite catalyst was prepared and tested to decompose H2O2, inactivate bacteria E. coli and degrade oxytetracycline. X-ray diffraction patterns confirmed the stability of the catalyst phase after sintering and after the decomposition of H2O2. Mössbauer spectra of the raw and used catalysts demonstrate the stable values of isomer shift. This fact confirms the chemical stability of the hematite catalyst. The degree of the H2O2 decomposition was found to increase with increasing residence time in the catalytic reactor. The prepared hematite catalyst was tested for the removal of oxytetracycline in a continuous flow mode. The efficiency of oxytetracycline removal increases with the increasing concentration of H2O2. The effect of the inlet concentration of H2O2 on the inactivation of E. coli was also studied. It was found that the outlet bacterial count gradually decreases with the increase of the inlet H2O2 concentration. The larger the inlet bacterial loading, the larger the H2O2 concentration is required to attain an acceptable bacteria count at the reactor outlet. At neutral pH, the surface of the catalyst is positively charged (pHPZC = 8.09) and E.coli bacteria are electrostatically attracted to the hematite surface. This contributes to their accelerated inactivation by hydroxyl radicals formed on the catalyst surface. Thus, the fixed-bed flow-through reactor filled with hematite is promising for the degradation of organic pollutants and water disinfection.