Nano-Remediation: Application of Nanotechnology to Clean Up Environment
Authors: Nilimesh Mridha1, Pragati Pramanik1, Anirban Mukherjee2, AniruddhaMaity3, and Kumari Shubha4, Vikas Rai5

1,2, 3ICAR-Indian Agricultural Research Institute, New Delhi; 3ICAR-Indian Grassland and Fodder Research Institute, Jhansi 4 ;ICAR-National Bureau of Plant Genetic Resources, New Delhi


Environmental remediation accomplishes the exclusion of pollutants or contaminants from different environments like soil, surface and/or ground water and sediment, for the safety of human health and environment. For drinking fresh water, breathing clean air and using good quality water for agriculture and industry, clean and pollution free environment is extremely required. Regrettably, many important natural resources like surface and groundwater, air, soil etc are uninterruptedly vulnerable to many natural and anthropogenic contaminants. Nano remediation is the use of nano particles for environmental remediation. Nano particles with their small size (1-100 nm) and the large surface area opens up possibilities for valuable and effective energy management and pollution control techniques. The basic idea for controlling pollution at nano level is segregating specific elements and molecules from a mixture of pollutants through nanofabrication, thermal partitioning or nano structuring (1). Nanotechnology is creating important developments in technologies for shielding the environment through enhanced sensing, treating and remediating environmental contaminants using nano scale devices. Conversely, the distinct characteristics of nanotechnology may also result to the unexpected environmental problems for which we should be very careful. All the recent developments in nano remediation techniques to combat environmental pollution like air and water pollution, cleaning up of oil spills are discussed briefly throughout the article.

Nanosensors and the environment

Scientists created a low-cost, highly-selective Functionalized Nanoporous Thin Films (FNTF) which is capable of sensing heavy metals present in aqueous environments at Pacific Northwest National Laboratory (PNNL),in collaboration with PANalytical B.V. It can detect nearly every heavy metal that poses serious threat to human health and the environment with thousand times more sensitivity than the previous capability(2). Researchers at the PNNL developed a new methodology called nano-DESI for faster and easier measurements of aerosolized sample using a high-resolution mass spectrometer. Superparamagnetic nanoparticles capable of absorbing heavy metal ions were developed through joint ventures of University of Washington, PNNL andOregon Health & Science University.

Air Pollution

The nano-catalysts can combat air pollution due to having enlarged surface area for reactions of different gases. Catalysts convert detrimental vapors coming out from different sources like cars, industrial plants etc to harmless gases by enhancing efficacy of chemical reactions with it. Currently, nano fiber catalysts made of manganese oxide are particularly used to eliminate volatile organic components from industrial vents. A different approach utilizes nano structured membranes with extremely small pores to isolate methane or carbon dioxide from exhaust. Use of Carbon Nano Tubes (CNT) makes nano remediation to trap gaseous molecules hundred times faster and efficient than other methods that and segregates gigantic volumes of gas successfully. The filtered waste still poses a serious problem for disposal, as after filtrating from the air and again to return back to the ground yields no beneficial results. Thus it needs recycling. The diesel soot is used to synthesize the single-walled CNT filter through laser vaporization by Japanese researchers in 2006 which means basically the filtered waste becomes the filter. There are several other methods that are still in development.

Water Pollution and cleaning of oil spills

Conventional systems of water purification use semi-permeable membranes for electrodialysis or reverse osmosis but the nanotechnology has made the water purification techniques much easy because inserting nano particles into underground water is much cheaper and efficient than pumping water for treatment. The cheaper and energy efficient method of deionization techniques is the use of nano- fibers as electrodes. Lessening the pore size of the membrane to the nanometer scale would improve the selectivity of the molecules to pass through. Membranes for filtering out viruses are at the present available.

Ion exchange resins are widely used in separation, water softening, purification, and decontamination of water. Ion exchange resins are organic polymer compound with nano-sized pores on the surface. These nano sized pores trapped and exchanged ions for other ions like poisonous elements like heavy metals are replaced by sodium or potassium and water purification. . On the other hand, ion exchange resins are easily spoiled or polluted by iron, organic matter, bacteria, and chlorine.

Dispersing agents, gelling agents, and biological agents are mainly used for cleaning up oil spills. still, Oil lost can not be recovered by any of the above methods. Researchers at Massachusettes Institute of Technology (MIT) developed a nano wires mat made up potassium manganese oxide which can absorb oil up to 20 times its weight. As potassium manganese oxide has very high stability even at high temperatures, the oil can be recovered from the nano wires and both the oil and nano wires can furthered be reused. The Interface Science Corporation effectively launched a new nanowire based oil remediation and recovery techniques, which is used to clean up the oil spilled by damaged oil platforms and refineries. Now a days nano catalyst are also used in oil refining which is more efficient and better for the environment.

Conclusion

Nanoremediation techniques has the potential to reduce the costs of cleaning up large contaminated sites ,cleanup time, get rid of the need for treatment and removal of polluted soil, decrease some contaminant concentrations to near zero in situ. For appropriate assessment of nano-remediation techniques, wide studies on different environments are required to avoid any possible undesirable environmental affects. New nano materials and their manufacturing approaches are required to pose negligible damage to human wellbeing or environment.

References
1.S. L. Gillett, Nanotechnology: Clean Energy and Resources for the Future (2002). Available at http://www.foresight.org/impact/whitepaper_illos_rev3.PDF
2."Coating helps increase water testing sensitivity by one thousand times ," PNNL,http://www.pnl.gov/business/stories.aspx#story21
3. T. Uchida et al., Japanese Journal of Applied Physics 45, 80278029(2006).


About Author / Additional Info:
Currently doing Ph.D. at IARI