Water Purification Using Nanoparticles

In our last blog post we covered some applications of hydroxyapatite, especially its use in bone implants. In this blog post we are also going to discuss another very abundant thing within the human body. That would be water, making up to 60% of the human body. We all know that water is essential for the survival of living organisms, yet many Third World countries lack access to clean water with over 780 million people lacking access to clean water. The ocean contains 97% of Earth’s water, but only 1% of our freshwater is easily accessible. Obviously, it is absurd that Earth contains so much water that is not safe to drink. Thus, many scientists are currently trying to create portable water purifiers or a desalination system through the use of nanotechnology

Four vials of composite nanomaterials used in the filter, a sachet containing the materials, a filter cartridge, and a prototype of the water filtration device.

The unique activity of nanomaterials towards recalcitrant contaminants has sparked active research and development for the treatment of water. This is because of their effectivity with contaminants which conventional water treatment systems struggle to treat; this includes bacteria, viruses, and heavy metals. Their efficiency stems from the very high specific surface area of nanomaterials which increases dissolution, reactivity, and sorption of contaminants. At the Indian Institute of Technology Madras, a materials scientist, Thalappil Pradeep, knew that silver ions, when released from the metal in nanoparticle form, worked as a disinfectant found in a number of bacteria and viruses found in contaminated waters, as well as the fact that other inorganic toxins, such as lead, iron, and arsenic, could be collected from contaminated water with materials containing different chemical properties particular to each of those elements. For instance, iron oxyhydroxide nanoparticles can scavenge arsenic, while manganese oxide absorbs lead. Using this knowledge, the researchers were able to use a variety of nanostructured materials to purify a diverse array of contaminants typically found in water.

 One issue was that the contaminants found in the water tended to anchor to nanosilver surfaces, blocking the release of silver ions from them. To overcome this problem, researchers created a unique family of nanocrystalline metal oxyhydroxide-chitosan granular composite materials. This material, which forms a cage-like matrix, strongly bonds to embedded nanoparticles because of hydrogen bonding. The nanoparticles remain within the matrix, which only allows ions to escape at a controlled rate. Those ions then kill microbes found in the water, without releasing nanoparticles.

One way to purify the water is through usage of nanotubes, named ‘Janus nanotubes’ by their founders at the University of Warwick and the University of Sydney. The name is appropriate in that Janus was a two faced god and the nanotubes have a tubular structure with a shell for the end of the tube with two faces. The tube itself is based on the stacking of cyclic peptides, and with its channel of 1nm, it allows small molecules and ions to pass through. The faces themselves, when solid, can serve as a colander, or a sieve, at molecular level. This is applicative when trying to desalinate and purify water. Moreover, these nanotubes can have hydrophobic exterior surface and hydrophilic interior surface. This leads to them being able to serve for drug immobilization and controlled release.

 Water purification and desalination can lead to a dramatic increase in availability of water safe to drink. If successful, the filter using nanoparticle technology can result in inexpensive and portable water purification device at $3 per year and lasting for about a year, or 3,600 liters of water. Some scientists have calculated that this is enough to provide for a family of four. If brought to reality, many of the 780 million people lacking access to clean water maybe be able to desalinate water from ocean.

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