Wastewater Treatment
Clean water is a crucial commodity. However, the availability of clean water is in the increasing jeopardy with the progression of industrialization (especially in the developing countries) and the effective wastewater remediation becomes more and more essential. The problem is enhanced by the fact that many chemical or pharmaceutical plants produce more and more chemicals which are not only toxic and should not be dumped into the global water resources, but they are also chemically stubborn and resistant to typical wastewater treatments. The main problem of these pollutants is their resistance to oxidative reactions i.e their high reduction potential. Degradation of these chemicals (such as aromatic compounds, phenols, benzene, toluene, azo-molecules etc.) requires oxidative agents having a very high oxidation potential in order to be effective. An extreme example of such toxic and difficult to degrade wastewater types are the hydrraulic fracking liquids and their leachate.
The oxidation potentials of various oxidation agents are listed in the table. The list shows a wide range of potential values for common oxidizers. Hydroxyl radical is at the top of the list, surpassing by far the atomic oxygen species, ozone and other common agents. It is clear from the table that for example ozone is not capable of oxidizing molecules that have their potential higher than 2.07 V, such as aromatic rings, e.g. benzene or toluene, for which Eo values in a solvent equal respectively to 2.48 and 2.26 V [ref.source]. For this reason, such aromatic rings can actually only quench ozone and they cannot undergo remediation by ozonation methods. By contrast, these aromatic rings are accessible for oxidation by the hydroxyl radical.
In practice, there are myriads of stubborn pollutants in the wastewater that fall into the gap between the hydroxyl radical potential and the rest of the oxidative agents, especially from the difficult pharmaceutical or chemical industries, including antibiotics, pesticides, herbicides, leachates. For such cases, Advanced Oxidation with the use of hydroxyl radicals is the only available remedy.
Hydrogen peroxide is an ideal tool for water purification, because it does not introduce any harmful chemicals such as bleach or chlorine and decomposes into water and oxygen, according to the reaction:
2 H2O2 → 2 H2O + O2
While hydrogen peroxide is a useful oxidant - as shown in the table of oxidation potential - the introduction of a specialized catalyst (OXYCATALYST) moves the reaction to the top of the table, because the catalyzed reaction produces Hydroxyl Radicals as the oxidative species. Hydroxyl radicals are therefore much more powerful than the hydrogen peroxide alone.
Catalytic decomposition of hydrogen peroxide can be also evaluated with Methylene Blue, which is the known indicator of hydroxyl radicals. In the presence of hydroxyl radicals Methylene Blue undergoes decoloration, even in hydrogen peroxide environment which is not a reducing agent. The decoloration of Methylene Blue is instant and fully accomplished within minutes when treated by catalyzed hydrogen peroxide.
Catalyzed decomposition of H2O2 results in the abundant formation of hydroxyl radicals which are extremely powerful in oxidation reactions. The hydroxyl radicals are fast and efficient in elimination of all types of pollutants: organic matter, toxic chemicals, pharmaceutical waste, agricultural waste, fertilizers, herbicides, antibiotics, dyes (including azo dyes), fracking waste and so on. Wastewater treatment reduces COD (Chemical Oxygen Demand) and BOD (Biological Oxygen Demand). COD is a measure of organic pollution in water and BOD is a measure of the oxygen used by microorganisms to decompose this waste.
The Catalytic Advanced Oxidation process cleans and disinfects water without introducing any harsh chemicals and does not affect solution pH (unlike Fenton reagents). The catalyst is heterogeneous, which means that it will not be dissolved in water and can be removed and reused. Hydroxyl radicals are very short-lived (of the order of nanoseconds) and therefore they do not remain in the effluent after treatment - their excess is annihilated as oxygen gas generation. Catalytic Advanced Oxidation reduces organic pollutants and toxic chemicals, eliminates odors and colors, sterilizes and disinfects effluents by attacking pathogenic microorganisms and bacteria.