Solar Water Purification
source: http://www.economist.com/science-technology/technology-monitor/displayStory.cfm?story_id=155...
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The trick the researchers use to boost the cleansing action of ultraviolet is to add a light-activated catalyst to the effluent. They have come up with two sorts, one for heavily polluted water and one for water that is only lightly polluted.
For water containing serious industrial contaminants, like that at Lampoldshausen, they use iron sulphate as the catalyst and add a small amount of hydrogen peroxide and sulfuric acid to assist the process. Thus treated, the water is pumped through arrays of transparent glass tubes in a 49 meter-long solar reactor. In a complex series of reactions, one of which is promoted by ultraviolet light, the iron reacts with both the hydrogen peroxide and some of the water itself to produce powerful oxidizing agents known as hydroxyl radicals. These destroy the polluting molecules. Once the water has been cleaned, the acid is neutralized, causing the iron to become insoluble. It precipitates out as iron oxide and can then be recovered and recycled, leaving water pure enough to discharge into a river.
For less heavily polluted water, similar equipment is used, except that the glass tubes are coated with titanium dioxide. This substance is a semiconductor, meaning that when electrons (which are negatively charged) are knocked free from its crystal structure, the result is a positively charged “hole” that can move around inside the crystal. This hole is also a powerful oxidizer. One of the ways a hole can be created is for the electron to be displaced by ultraviolet light. A titanium-dioxide system, which is still in development, could purify water to the point where it was suitable not merely for discharge, but for drinking.
http://www.economist.com/science-technology/technology-monitor/displayStory.cfm?...
For water containing serious industrial contaminants, like that at Lampoldshausen, they use iron sulphate as the catalyst and add a small amount of hydrogen peroxide and sulfuric acid to assist the process. Thus treated, the water is pumped through arrays of transparent glass tubes in a 49 meter-long solar reactor. In a complex series of reactions, one of which is promoted by ultraviolet light, the iron reacts with both the hydrogen peroxide and some of the water itself to produce powerful oxidizing agents known as hydroxyl radicals. These destroy the polluting molecules. Once the water has been cleaned, the acid is neutralized, causing the iron to become insoluble. It precipitates out as iron oxide and can then be recovered and recycled, leaving water pure enough to discharge into a river.
For less heavily polluted water, similar equipment is used, except that the glass tubes are coated with titanium dioxide. This substance is a semiconductor, meaning that when electrons (which are negatively charged) are knocked free from its crystal structure, the result is a positively charged “hole” that can move around inside the crystal. This hole is also a powerful oxidizer. One of the ways a hole can be created is for the electron to be displaced by ultraviolet light. A titanium-dioxide system, which is still in development, could purify water to the point where it was suitable not merely for discharge, but for drinking.
http://www.economist.com/science-technology/technology-monitor/displayStory.cfm?...
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- groups:
- Co-Evolution
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- tags:
- Solar, Water purification, solar research
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artemis6
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This could be great in many parts of the world .
- 2 years ago
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artemis6
