Clean Up the Water with Nanotechnology

Nanotechnology can help clean water using several methods, including injecting nanoparticles underground to clean contaminates out of groundwater and using silver nanowires and carbon nanotubes to kill bacteria in drinking water.

Industrial solvents in groundwater, such as a liquid cleaning solvent called trichloroethylene (TCE), can damage our health.

According to the Agency for Toxic Substances and Disease Registry, a department of the U.S. Department of Health and Human Services, “Drinking or breathing high levels of trichloroethylene may cause nervous system effects, liver and lung damage, abnormal heartbeat, coma, and possibly death. Trichloroethylene has been found in at least 852 of the 1,200+ National Priorities List sites identified by the Environmental Protection Agency (EPA).”

One challenge in cleaning groundwater is the removal of industrial water pollution, such as TCE. Researchers have shown that iron nanoparticles can rapidly degrade chlorinated hydrocarbons, such as TCE, to make a harmless mix of byproducts.

When you inject iron nanoparticles into a groundwater system such as an aquifer (permeable rock that contains groundwater), a reaction occurs between the iron atoms, the solvent, and hydrogen ions. In this reaction, iron atoms from the nanoparticle give up two electrons (iron atoms can easily give up electrons and are quite stable as positive ions in water) to the chlorine atoms.

As a result, hydrogen ions (occurring naturally in water) combine with the carbon atoms. This leaves you with a common, ordinary organic molecule in which the carbon atoms are surrounded by hydrogen atoms (like methane or ethane), positive iron ions, and negative chlorine ions (commonly present in saltwater). Because nanoparticles can remain suspended in the groundwater for a long time, they can permeate large areas of groundwater.

The iron used in these nanoparticles is often referred to as zero-valent iron (ZVI). That’s just a fancy way for chemists to say that the iron hasn’t reacted with any other material yet and therefore still has all its electrons.

Using iron nanoparticles in this way to treat groundwater is much less expensive than pumping the water out of the ground for treatment.

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Lehigh Nanotech is a company that is using iron nanoparticles to clean contaminates. The intriguing techniques they are using were developed through research at Lehigh University.

Metallic contaminates in groundwater, such as mercury, are also a concern. Researchers at Pacific Northwestern Laboratory have developed a material to remove mercury from groundwater. The material is called SAMMS, which is short for Self-Assembled Monolayers on Mesoporous Supports.

This material consists of ceramic particles whose surface has many nanosize pores. These pores are lined with molecules that have sulfur atoms on one end, leaving a hole in the center that is also lined with sulfur atoms. Scientists line the nanopores with molecules containing sulfur because it bonds to mercury, so mercury atoms bond to the sulfur and are trapped in the nanopores.

The researchers are developing SAMMS that contain other molecules in the nanopores to remove other metal contaminates from groundwater.

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