Ozone/H2O2 process

Ozone is main component in many oxidation processes assembled imder the term ozonation processes. In these processes ozone is applied either alone (O3 process) or with the addition of oxidant, e.g. H2O2 (O3/H2O2 process), UV radiation (explained in above subchapter), catalyst, activated carbon, ultrasoimd etc. Ozone is inorganic molecule constituted by three atoms of oxygen. It is present in nature in upper atmosphere in the form of stratospheric layer aroimd the earth, and it is formed by the photolysis of diatomic oxygen and further recombination of atomic and diatomic oxygen, shown by equations (25) and (26) [35] ... 

The values calculated in literature differ widely. However, it becomes clear that for the removal of MTBE one has to consider EE/0 values between 1 and 9 kWh/m order, both in lab-scale and pilot-scale operation. There is not much difference between the application of ozone/H202 or UV/H2O2 process. Typical EE/0 values for other contaminants range from 0.5-1.3 kWh/m order for BTEX, 2.6-2.7 kWh/m order for atrazine or 0.5-1.6 kWh/m order for 1,4-dioxane. This difference could be expected, since MTBE is much less efficiently eliminable than BTEX. 

Shu, H. and Chang, M. (2005). Pre-ozonation Coupled with UV/H2O2 Process for the Decoloration and Mineralization of Cotton Dyeing Effluent and Synthesized C. I. Direct Black 22 Wastewater, J. Hazardous Materials, 121, pp. 127-133. 

The common oxidants are ozone, hydrogen peroxide, H2O, catalyzed usually with ferrous iron, Fe , and ia some cases chlorine dioxide and uv light. Advanced oxidation systems iaclude H2O2 + uv ozone + uv and H2O2, ozone, and uv. Depending on the appHcation, the oxidation can be complete to end products as in a contaminated groundwater or partial to degradable intermediate products as in a process wastewater. 

Chemical processes include reduction and oxidation. Conventional chemical (coagulation-flocculation) and advanced oxidation processes (AOPs), such as chemical oxidation (ozonation, Fenton oxidation, Fe2+/H202), ultrasonic chemical oxidation, photocatalysis oxidation (UV/H2Q2, UV/O3, and W/O3/H2O2),... 

The main estimation results are values of ratio mineralization extent/process operating costs (ME/POC). Besides costs estimation on the basis of mineralized organic content, the cost for decolorization below visibility limit, <1 mgL that corresponds to decolorization below 1.25 % in our case, are also showed. From the point of view of the most suitable processes for decolorization of RB137 model wastewater below visibility limit, it can be seen that processes combining ozone and UV irradiation, UV/O3 and UV/O3/H2O2, are double cheaper than... 

Figure 6 Scheme of O3/UV/H2O2 oxidation processes. Key 1 From direct ozonation. 2 From direct photolysis. 3 From free radical oxidation. 4 Intermediate pathway if M is inhibitor. 5 Intermediate pathway if M is promoter. 

Groblicki, P.J. Ang, C.C. "Measurement of H2O2 without Ozone Interference", Proceedings of the Symposium on Heterogeneous Processes in Source-Dominated Atmospheres, New York, 1985, 86-88. 

The process is expensive but fast, and can treat organic pollutants at very low concentrations (ppb), at a pH between 7 and 8 the optimal O3/H2O2 molar ratio is = 2 1. It has been suggested that the acceleration of ozonation is due to the fact that H2O2 increases ozone transfer within water [44],... 

Benitez FJ, Beltran-Heredia J, Acero JL, Gonzalez T (1996) Degradation of Proto-catechuic Acid by Two Advanced Oxidation Processes Ozone/UV Radiation and H2O2/UV Radiation, Wat. Res. 30, No. 7 1597-1604. 

This ozone-mediated pathway for the production of OH is about twice as expensive as that using H2O2—it can only compete with the latter when the photolysis of H2O2 becomes inefficient (as in opaque waters). In fact, processes that combine H2O2, O3, and UV are now more commonly used because of their high efficiency. 

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