Photodegradation Systems Clause Samples
Photodegradation Systems. By using solar energy to couple hydrogen evolution to the photodegradation of organic pollutants, value is added to the photodegradation process. The use of UV or solar light to destroy organic pollutants in contaminated waters is quite expensive, with treatment costs varying between $1 and $50 per kg of pollutant removed. If hydrogen could be evolved at the same time as organic pollutants are photodegraded, considerable value could be added to the process. This option has not been pursued very much in the literature, but, in my opinion, it deserves to be examined in considerable detail.
Photodegradation Systems. There is another option for solar hydrogen production that does not involve the evolution of oxygen. In this case an organic substrate, which may be a pollutant, is used as the sacrificial donor in a reduction half reaction. There is no net energy storage (indeed most of these reactions are exergonic), but hydrogen is produced at the same time as a surplus or even polluting organic compound is oxidized. For example, the reaction CH3COOH(aq) + O2 ⎯⎯→ 2 CO2 + 2 H2 (7) is exergonic by 392.3 kJ but the fuel value of the H2 produced is 474 kJ. The process involves the conversion of one fuel (CH3COOH, with a fuel value of 866 kJ) into another fuel (2 H2, with a fuel value of 474 kJ). The potential added value is in the destruction of a pollutant. For example, UV light (and also sunlight) is now used to oxidize organic pollutants to CO2 and H2O. It may be possible to modify these processes so that hydrogen would be produced as a byproduct.