Chemically scrubbing CO2 from the air too expensive, says Stanford researcher who offers an alternative plan. Erkki Makkonen / iStock Technology exists today for removing carbon dioxide emissions from coal-fired power plants and is much cheaper than removal from the atmosphere. Someday the world may be in a position to lower the concentration of heat-trapping carbon dioxide in the atmosphere by chemically removing it from the air. But not soon; the process is simply too expensive, say scientists from Stanford and MIT. A study published in the Proceedings of the National Academy of Sciences, co-authored by Stanford energy and environmental researcher Jennifer Wilcox, concludes that if air-capture of carbon dioxide with chemicals is ever used, it will be far in the future. For now, it is much more economically efficient to capture the carbon dioxide that enters the atmosphere from the smokestacks of large centralized sources such as power plants, cement plants, fertilizer plants and refineries.
Jennifer Wilcox "Direct air capture sounds great in theory," Wilcox said. Media Contact 24 Stumble 8516 Share. Peroxide. A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion, O2- 2.[1] The O−O group is called the peroxide group or peroxo group. In contrast to oxide ions, the oxygen atoms in the peroxide ion have an oxidation state of −1.[2] Peroxides have a bleaching effect on organic substances and therefore are added to some detergents and hair colorants. Other large-scale applications include medicine and chemical industry, where peroxides are used in various synthesis reactions or occur as intermediate products. With an annual production of over 2 million tonnes, hydrogen peroxide is the most economically important peroxide. Many peroxides are unstable and hazardous substances; they cannot be stored and therefore are synthesized in situ and used immediately. In biochemistry[edit] Peroxides are usually very reactive and thus occur in nature only in a few forms.
Formation of hydrogen peroxide by superoxide dismutase (SOD) FAD = flavin adenine dinucleotide Applications[edit] Peroxidase. Peroxidases (EC number 1.11.1.x) are a large family of enzymes that typically catalyze a reaction of the form: ROOR' + electron donor (2 e-) + 2H+ → ROH + R'OH The nature of the electron donor is very dependent on the structure of the enzyme. For example, horseradish peroxidase can use a variety of organic compounds as electron donors and acceptors. Horseradish peroxidase has an accessible active site, and many compounds can reach the site of the reaction.Because there is a very closed active site, for an enzyme such as cytochrome c peroxidase, the compounds that donate electrons are very specific.
While the exact mechanisms have yet to be elucidated, peroxidases are known to play a part in increasing a plant's defenses against pathogens.[1] Peroxidases are sometimes used as histological marker. Amyloid beta, when bound to heme, has been shown to have peroxidase activity.[2] A typical group of peroxidases are the haloperoxidases. Applications[edit] See also[edit] References[edit] Redox. The two parts of a redox reaction Redox (portmanteau of reduction and oxidation) reactions include all chemical reactions in which atoms have their oxidation state changed; in general, redox reactions involve the transfer of electrons between species. The term "redox" comes from two concepts involved with electron transfer: reduction and oxidation.[1] It can be explained in simple terms: Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.
Although oxidation reactions are commonly associated with the formation of oxides from oxygen molecules, these are only specific examples of a more general concept of reactions involving electron transfer. Redox reactions, or oxidation-reduction reactions, have a number of similarities to acid–base reactions. Though sufficient for many purposes, these descriptions are not precisely correct. Etymology[edit] [edit] Chemical looping combustion. Chemical looping combustion (CLC) typically employs a dual fluidized bed system (circulating fluidized bed process) where a metal oxide is employed as a bed material providing the oxygen for combustion in the fuel reactor. The reduced metal is then transferred to the second bed (air reactor) and re-oxidized before being reintroduced back to the fuel reactor completing the loop. Isolation of the fuel from air simplifies the number of chemical reactions in combustion.
Employing oxygen without nitrogen and the trace gases found in air eliminates the primary source for the formation of nitrogen oxide (NOx), producing a flue gas composed primarily of carbon dioxide and water vapor; other trace pollutants depend on the fuel selected. Description[edit] Chemical looping combustion (CLC) uses two or more reactions to perform the oxidation of hydrocarbon based fuels.
If (1) and (2) are added together, the reaction set reduces to straight carbon oxidation – the nickel acting as a catalyst only i.e.