What is nanotechnology?
The urgent need for clean water has generated considerable interest in water purification techniques and particularly in nanomaterials and nanomembranes because they represent efficient and environmentally friendly, low-energy and high-volume, water treatment solutions.
With this incredible ability to manipulate materials at such small scale, nanotechnology can radically alter the function of materials and create products with unique abilities. This includes the extraordinary ability to purify water with near total efficiency (over 99.99%). In fact, only nanotechnology can purify water to this degree because the impurities that are the most difficult to separate from water all occur at the nanoscale (between 1 and 100 nanometers). Nanoscience and nanoengineered products therefore offer breakthroughs in water treatment; they not only enable the removal of virtually all contaminants, but they enable it to be done without the need for power or expensive resources.Nanotechnology occurs at infinitely small scales. It has been made possible through use of highly sophisticated techniques such as ‘tunneling electron microscopy’. These techniques enable scientists to view material right down to the atomic-level and enables them to modify and ultimately create novel materials at the near-atomic scale (nanoscale). That is, material none of us can see with the naked eye. Nanoalumina (an active part of some nanomembranes used in water purification) measures just 2 nanometers in diameter (one nanometer measures one billionth of a meter). To put that into perspective, the width of a human hair is 100,000 nanometers. So, in other words, no less than 50,000 nanoalumina sheets could be stacked one on top of the other inside the diameter of an average human hair.
How do nanomembranes work?
Water purifying nanomembranes work by creating strong electropositive charge and can trap things even as small as viruses (as they have negative surface charge). Nanotechnology is a powerful ‘enabler’ and nanomaterials offer unique abilities which do not exist at the macro-scale (with ‘normal’ sized material). Nanoalumina fibers have an ‘enhanced’ purifying capacity because they have a very large surface area of around 350-500m2per gram. To put this enhanced surface area into perspective, 1 gram of aluminum foil might have a surface area of maybe 2cm2, i.e., 0.0002m2which means per gram, the nanoparticles have a surface area that is over 2 million times greater. This unique property considerably increases the adsorbing effect which means electronegative particles such as viruses gets ‘stuck’ to the membrane with ease. Virtually no impurities make it through this matrix material which has 2nm sized pores and mesh-type appearance.
These nanoalumina layers with high electropositive charge can be bonded with microglass fibers and cellulose, then pleated inside a cartridge. Nanotechnology enables the inclusion of other breakthroughs into this type of filtration design. For example, silver nanoparticles can be incorporated, enabling the removal of pollutants such as bromide and chlorine. Further modified silver nanoparticles enable ‘self-cleaning’ of the membrane itself. ‘Powdered activated carbon’ and use of carbon nanotubes can further enhance the efficiency of already highly-effective membrane structures.
Why choose Nano Technology?
Billions of dollars have gone into nanotechnology discovery. The result is the ability to produce material that behaves like no other. Water filtration membranes are therefore able to operate unlike any other. They do not need water to be pressurized and they do not require electricity or the use of chemicals. Because of the large specific surface area and small size of nanoparticles, interface areas (e.g. where nanoparticles meet other materials), and the ‘interaction’ between the two can be exceedingly large so an entire range of novel characteristics emerge which can be harnessed in beneficial ways. In terms of water purification, this involves high-surface-to-volume ratios, increased ‘contact’ efficiency (related to the interfacial areas) and the ability to create material that is designed for a set purpose such as ‘crystallographic’ structures (which are all enabled by nanotechnology).
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