Photocatalyst use for environment purification
A promising approach for remediating air quality contaminants is to employ photocatalyst that oxidize these compounds. By definition, photocatalyst is a catalyst that accelerates photoreaction.When photocatalyst is exposed to light in the presence of water vapor, two highly reactive substances are formed: hydroxyl radicals [OH] and a superoxide anion [O2-1]. It allows the oxidation of airborne VOCs and toxic organic matter into carbon dioxide and water at room temperature with UV or near-UV light source. It does not need a special energy and use only clean energy in ordinary life. Specific titanium dioxide has strong photo catalyst reaction. It has strong oxidation and decomposition strength
Photocatalyst has the following advantages over any current air purification technologies
- Real destruction of pollutant rather than a simple transfer on a substrate
- Degradation of pollutant at ambient temperature and pressure
- Build with easily available materials and by mean of well-known techniques
- Economical, cheap and low energy consumption
- Adapted for a large range of pollutant (VOC, bacteria, mold)
Titanium Dioxide
Titanium dioxide, also known as titania, is the naturally occurring oxide of titanium, chemical formula TiO2. Approved by the food testing laboratory of the United States Food and Drug Administration (FDA), Titanium Dioxide is considered a safe substance and harmless to human. It is commonly used in paint, printing ink, plastics, paper, synthetic fibers, rubber, condensers, painting colors and crayons, ceramics, electronic components along with food and cosmetics. Many studies have been published on the use of titanium dioxide as a photocatalyst for the decomposition of organic compounds. After illuminated by light, titanium dioxide produces hydroxyl radicals, which react with the organic matters in the air to form non-toxic inorganic matters.
Titanium Dioxide molecules contain electrons that are confined to relatively narrow energy bands. The band of highest energy that contains electrons is the valence band, while the band lying above the valence band, i.e. the conduction band, has very few electrons. The difference in energies between the highest energy of the valence band and the lowest energy of the conduction band is termed the band gap energy. When a semiconductor absorbs a photon of energy equal to or greater than its band gap, an electron may be promoted from the valence band to the conduction band leaving behind an electron vacancy or “hole” in the valence band. If charge separation is maintained, the electron and the hole may migrate to the catalyst surface where they participate in redox reaction with sorbed species.Nanoteachnology
Nanotechnology, the revolutionary science and art of manipulating matter at the atomic or molecular scale. Nanotechnology is not just about the size of very small things. More important, it is about structure and the ability to work. Research in areas related to nanomaterial is needed to develop manufacturing techniques, in particular, is a synergy of top-down with bottom-up processes.When a matter is as small as 1 to 100 nanometers, many of its features will easily change and form into many different unique conditions both different from macro-matters and single atom due to the quanta effect, regional confinement of matter, and huge surface or interface effects. The final objective of nanometer technology is to produce products of special functions with new physical and chemical features by making atoms, molecules and matters presenting their features directly in the length of a nanometer: t he strength of ten times of iron could be very light, all information in a library could be stored in a chip the size as a piece of square sugar, and tumors the sizes of only several cells can be detected.The US Business Weekly listed nanometer technology as one of the three key areas in the 21st century . From 1999, the US government decided to put the research in nanometer technology into one of the 11 key areas in the first ten years of the new century. In February 2000, US president Bill Clinton announced that the US Federal Government would invest 495 million dollars to set up a work group and put forth a research report on the promotion, saying that it will lead to the next industrial revolution as a top priority.Titanium Dioxide's photocatalytic characteristic is greatly enhanced due to the advent of nanotechnology. At nano-scale, not only the surface area of titanium dioxide particle increases dramatically but also it exhibits other effects on optical properties and size quantization. An increased rate in photocatalytic reaction is observed as the redox potential increase as the size decreases. Energy from any ambient light source can be used effectively as the energy source of photocatalysis instead of UV light.
Technology Comparition
HEPA (High Efficiency Particle Arresting) FilterMost widely known method for purifying air. Depending on the filter size, it can clean up to 99.99% of particulate in the air with proper ventilation. They are not effective on treating mold, mildew, bacteria, and other fungi.Electrostatic FiltrationAnother filtration system with a negatively charged surface is used to attract particulate. In comparison to most HEPA systems it is more effective in trapping smaller micron particulate and effective in clearing smoke from the air. Low levels of ozone may be produced which can neutralize most mold, mildew, bacteria, and other fungi that comes in contact with the filter.IonizationAlso uses a negatively charged surface to produce and expels an abundance of negative ions and cause suspended particles to cling to walls, floors, and other surfaces . Most ionizers are effective in settling dust and particulate out of our breathing space.OzoneOzone is a very powerful oxidizer that will neutralize odors, mold, mildew, bacteria, and other fungi. This technology is commonly used in flood and fire restoration. Ozone is found to be effective because it works on the problem at the source and air does not have to be pulled through the unit for treatment.UV Germicidal LampsCommonly used for disinfecting purposes. This technology is effective in sterilizing air and surfaces that come in contact with the UV light. UV has been proven in both air and water applications to inactivate bacteria and viruses to prevent them from reproducing.PhotocatalysisUsing light to react with a catalyst resulting in oxidation. This is found to be effective in destroying mold, mildew, bacteria, other fungi, dust mites, and many odors. This technology is produced with an Ozone/UV lamp set in a variety of combinations. When this type of photocatalysis is combined with the natural humidity in indoor air it creates hydroxyl radicals and super oxide ions that are effective in combating bacteria, fungi and VOC. This method is also a pro-active approach that goes to the source for treatment.
เขียนโดย pizzakatai
บทความ
ไม่มีความคิดเห็น:
แสดงความคิดเห็น