Nanotechnology can be used for treating and purifying water, such as in the generation of fresh water from seawater, the prevention of environmental contamination and the creation of remediation techniques to reduce water and soil pollution.
Although the applications of engineered nanomaterials in water treatment are currently limited mainly to their use as adsorbents, filters, disinfectants and reactive agents, they are showing increasing promise for full-scale water treatment and environmental remediation.
One example of the potential of nanomaterials in this area is the development of nanoscale zero-valent iron. This material can be used for groundwater and hazardous waste treatment. The use of engineered nanomaterials for environmental clean-up started when researchers discovered that a small amount of nano-sized iron particles can remove groundwater contaminants like polychlorinated biphenyls (PCBs), which are known to be toxic to both humans and the environment and are likely to cause cancer. Iron nanoparticles such as nanoscale zero-valent iron were also found to be effective in the treatment of a variety of water pollutants, such as pesticides, flame retardants, antibiotics, chromium, arsenic and heavy metals.
A nanomaterial such as nanoscale zero-valent iron has many properties that makes it an ideal adsorbent for heavy metals in contaminated water, including:
- a large relative surface area and a small size;
- high reactivity;
- the ability to isolate heavy metals;
- the ability to work rapidly;
- good metal binding capacity; and
- structural characteristics that enable regeneration and reuse of the nanomaterial.
Example: Removal of arsenic from water
Arsenic is a toxic semimetal that has been linked to a number of cancers as well as other health issues. The contamination of groundwater by arsenic is naturally occurring and has been reported in many countries, including Argentina, Bangladesh, Chile, China, India, Taiwan and Thailand as well as some EU countries and the United States. Arsenic can enter groundwater in many different ways, such as through natural deposits, mining, agriculture or industrial activities.
The removal of arsenic and other similar contaminants from water has been of particular concern to the scientific community. The use of nano-adsorbents for arsenic removal from contaminated groundwater has shown very promising results in recent years.