Catalytic wet air oxidation (CWAO) is a nonconventional wastewater treatment, consisting of oxygen pressure releasing inside a reactor in order to degrade organic compounds dissolved in water, using a solid catalyst in the presence of an activated O 2 species, usually at temperatures ranges of 125-250°C and pressures of 10-50 bar. CWAO can reduce operating costs of conventional treatment due to the use of ideal catalyst that is able to improve reaction conditions at temperatures and pressures as mild as possible, simultaneously setting high catalytic activity and long-term stability of heterogeneous catalysts. Oxygenated fuels are gasoline additives in reformulated gasoline and oxyfuels. In the beginning, they provided an alternative solution of environmental problems, such as greenhouse gas emissions and octane enhancement, caused by fossil fuel use. The oxygenated fuels frequently used are methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). However, there is environmental impact from oxygenated fuel hydrocarbons related to widespread contamination of groundwater and other natural waters. Our research group developed a wide study in order to evaluate several catalysts (Ru, Au, Cu, and Ag supported on Al 2 O 3 , Al 2 O 3 -CeO 2 , and TiO 2 -CeO 2 ) and to obtain the best for the efficiency of the oxidation process.Nonconventional Wastewater Treatment for the Degradation of Fuel Oxygenated… DOI: http://dx.doi.org/10.5772/intechopen.84250 blended in gasoline in some metropolitan areas, heavily polluted by carbon monoxide, and to reduce carbon monoxide and ozone concentrations [14].

Ions of Sm 3+ , Eu 3+ and Gd 3+ were deposited onto the surface of TiO 2 -P25 using an impregnation method, and the catalysts were calcined to 500°C in order to provide thermal stability to the crystalline phases. A sample of pure P25 was processed under the same synthesis conditions. The materials were characterized by physisorption of N 2 , X-ray diffraction and Scanning Electron Microscope and Spectroscopy UV-Vis with diffuse reflectance. It was observed by SEM that P25 had an amorphous surface forming irregular aggregates and deformations in which the studied lanthanide ions were inserted. Due to heat treatment, the P25 suffered modifications that showed a higher photocatalytic activity in the visible region, by the presence of oxygen vacancies generated by the removal of impurities (C and Cl). XRD analyses determined the distribution and crystal size of the crystalline phases presented in the P25 (anatase and rutile). Lanthanide ions possibly demonstrated an effect of superficial coalescing in the rutile phase of the P25. A completely randomized experimental design was used to determine the catalytic evaluation, and sunlight was statistically shown to be the best condition for the degradation and mineralization of diuron. Comparing treatments indicated a better option: using the catalyst with 0.3 wt% Gd under sunlight.

Rare earth doping ions can improve the spectral response of this semiconductor to the visible region. This work evaluated the dopant effect of rare earth ions such as La, Ce, Nd, Pr, Sm, Eu, and Gd in titania for the solar photodegradation of Diuron and methyl parathion. The increase in the content up to 0.5% of dopants decreases photoactivity due to the formation of photo-generated electron-hole pair recombination centers. The catalysts calcined at 500°C presented only the anatase crystalline phase and the samples doped with La and Ce at 0.1 and 0.3% were the most active in diuron solar degradation; however, when the temperature of the thermal treatment increased to 800°C, mixtures of crystalline phases were presented. The catalyst with the highest anatase content showed the best performance. The materials calcined at 500°C with better performance in diuron solar degradation were selected to to treat methyl parathion using solar light. Finally, under these conditions, an affinity was found for the dopant ions in titania and in the functional groups of the contaminating molecules (phenylurea and thiophosphate). Solar photodegradation of diuron was more effective with La and Ce, while for methyl parathion, it was Eu at 0.3%.

No abstract