DESULFURIZATION & DENITRIFICATION

Desulfurization or desulphurisation is a chemical process for the removal of sulfur from a material. This involves either the removal of sulfur from a molecule (e.g. A=S → A:) or the removal of sulfur compounds from a mixture such as oil refinery streams. These processes are of great industrial and environmental importance as they provide the bulk of sulfur used in industry (Claus process and Contact process), sulfur-free compounds that could otherwise not be used in a great number of catalytic processes, and also reduce the release of harmful sulfur compounds into the environment, particularly sulfur dioxide (SO₂) which leads to acid rain. Processes used for desulfurization include hydrodesulfurization, the SNOX process and the wet sulfuric acid process (WSA process).

Denitrification is a microbially facilitated process where nitrate (NO₃^?) is reduced and ultimately produces molecular nitrogen (N₂) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitrification as a type of respiration that reduces oxidized forms of nitrogen in response to the oxidation of an electron donor such as organic matter. The preferred nitrogen electron acceptors in order of most to least thermodynamically favorable include nitrate (NO₃^?), nitrite (NO₂^?), nitric oxide (NO), nitrous oxide (N₂O) finally resulting in the production of dinitrogen (N₂) completing the nitrogen cycle. Denitrifying microbes require a very low oxygen concentration of less than 10%, as well as organic C for energy. Since denitrification can remove NO₃^?, reducing its leaching to groundwater, it can be strategically used to treat sewage or animal residues of high nitrogen content. Denitrification can leak N₂O, which is an ozone-depleting substance and a greenhouse gas that can have a considerable influence on global warming.

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