Химия и химические технологии/ Фундаментальные проблемы создания новых материалов и технологий

GHANNAM H.E.1 and TALAB A.S2

1,2 The National Institute of Oceanography and Fisheries, Cairo, Egypt.

NANOTECHNOLOGY IN WASTEWATER TREATMENT

ABSTRACT:

Nanotechnologies offer an affordable, effective, efficient and durable ways of achieving the target of water purification- specifically because using nanoparticles for water treatment will allow manufacturing that is less polluting than traditional methods and requires less labour, capital, land and energy. Some locations in Egypt now have highly polluted water and is not suitable for drinking purpose. It has been determined that these nano-based filters are able to achieve 99.95 percent efficiency, when compared to conventional technologies. The objective of this work is to provide a clearer picture on the application of nanotechnology in wastewater treatments.

INTRODUCTION:

          Nanotechnology is an emerging discipline, its application in water treatment has just begun, but the emerging trends. It can be predicted, that nanotechnology water treatment technology will be developed in the 21st century, and solve global water shortages and water pollution problems [4].

Water is the most essential substance for all life on earth and a precious resource for human civilization. Reliable access to clean and affordable water is considered one of the most basic humanitarian goals, and remains a major global challenge for the 21st century [7].

Water contamination is one of the major problems which the world is facing today, it is not only effect environment and human health, but it has also impacts on economic and social costs. There are various ways used commercially and non- commercially to fight this problem which is advancing day by day due to technological progress [6].

Water treatment is a requirement for all properly functioning societies worldwide, but is often limited. New approaches are continually being examined to supplement traditional water treatment methods. These need to be lower in cost and more effective than current techniques for the removal of contaminants from water. In this context also nanotechnological approaches are considered [1].

Since water treatment by using nanoparticles has high technology demand, its usage cost should be managed according to existing competition in market. There are various recent advances on different nanomaterials (nanostructured catalytic membranes, nanosorbents, nanocatalysts, bioactive nanoparticles, biomimetic membrane and molecularly imprinted polymers (MIPs) for removing toxic metal ions, disease causing microbes, organic and inorganic solutes from water [5,6].

Nanosorbents have very high and specific sorption capacity having wide application in water purification, remediation and treatment process. Sorbents are widely used in water treatment and purification to remove organic and inorganic contaminants. Examples are activated carbon and ion-exchange resins. The use of nanoparticles may have advantages over conventional materials due to the much larger surface area of nanoparticles on a mass basis. In addition, the unique structure and electronic properties of some nanoparticles can make them especially powerful adsorbents. Many materials have properties that are dependent on size [1, 6].

Magnetic nanoparticles offer advantages over non-magnetic nanoparticles because they can easily be separated from water using a magnetic field. Separation using magnetic gradients, the so-called high magnetic gradient separation is a process widely used in medicine and ore processing. This technique allows one to design processes where the particles not only remove compounds from water but also can easily be removed again and then be recycled or regenerated [1,3].

Nanofiltration membranes are pressure-driven membranes with properties between those of reverse osmosis and ultrafiltration membranes and have pore sizes between 0.2 and 4 nm. Nanofiltration membranes have been shown to remove turbidity, microorganisms and inorganic ions such as Ca and Na. They are used for softening of groundwater (reduction in water hardness), for removal of dissolved organic matter and trace pollutants from surface water, for wastewater treatment (removal of organic and inorganic pollutants and organic carbon) and for pretreatment in seawater desalination [1,9].

Nanocatalysts are also widely used in water treatment as it increases the catalytic activity at the surface due its special characteristics of having higher surface area with shape dependent properties. It enhances the reactivity and degradation of contaminants. The commonly used catalytic nanoparticles are semiconductor materials, zero-valence metal and bimetallic nanoparticles for degradation of environmental contaminants such as PCBs (polychlorinated biphenyls), azo dyes, halogenated aliphatic, organochlorine pesticides, halogenated herbicides, and nitro aromatics. The catalytic activity has been proved on laboratory scale for various contaminants. Since hydrogen is used in making active catalyst in large scale by redox reactions, there is need in reducing its consumption and maintain hydrogen economy by directly making catalysts in metallic form [2].

Nanostructured catalytic membranes are widely used for water contamination treatment. It offers several advantages like high uniformity of catalytic sites, capability of optimization, limiting contact time of catalyst, allowing sequential reactions and ease in industrial scale up [6].

Molecularly imprinted polymers have recently emerged as one of very fine techniques for various biological, pharmaceutical and environmental applications. Molecular imprinting is basically a process of free radical polymerization of a functional monomer and a cross linker. It works very selectively and has great potential to act as absorbents. It has been used for detection and treatment of water pollutants even at very low concentrations [6, 2].

Molecularly imprinted materials can be also used in combination with catalysts forming novel composite adsorbent or catalyst systems. The use of MIPs is advantageous over commonly used sorbents due to nature of being or performing selective extraction .MIP nanoparticles are encapsulated in nanofibres using electrospinning method that can be used for various pollution control applications including water treatment [8].

CONCLUSION:

Nanotechnology has also proved to be one of the finest and advance ways for waste water treatment. There are various reasons behind the success of nanotechnology and scientists are still working on further enhancement of its usage. Nanoparticles have very high absorbing, interacting and reacting capabilities due to its small size with high proportion of atoms at surface. It can even be mixed with aqueous suspensions and thus can behave as colloid. Nanoparticles can achieve energy conservation due to its small size which can ultimately lead to cost savings. Nanoparticles have great advantage of treating water in depths and any location which is generally left out by other conventional technologies.

REFERENCES

1.  Crane R. A., Scott T. B., (2012). Nanoscale zero-valent iron: Future prospects for an emerging water treatment technology. J Hazard Mater, pp 211-212.

2.  Hilal N., H. Al-Zoubi, N. A. Darwish, A. W. Mohammad, M. Abu Arabi ( 2004) Desalination, 170, 281.

3.  Ngomsik A. F., A. Bee, M. Draye, G. Cote, V. Cabuil, C. R. Chim. (2005). 8, 963.

4.  Nowack, B. (2008). Pollution prevention and treatment using nanotechnology. In: Nanotechnology, Volume 2 „Environmental aspects“. H. Krug, (Ed.). Wiley-VCH Verlag, Weinheim. pp. 1-15.

5.  Pandey J., Khare R., Kamboj M., Khare S. and Singh R. (2011). Potential of Nanotechnology For The Treatment of Waste Water. Asian Journal of Biochemical and Pharmaceutical Research Issue 2 (Vol. 1).p 272-282.

6.  Prachi, Pranjali Gautam, Deepa Madathil, A. N. Brijesh Nair. (2013). Nanotechnology in Waste Water Treatment: A ReviewInternational Journal of ChemTech ResearchVol.5, No.5, pp 2303-2308.

7.  Professsor Costas Kiparissides, (2010). Nanotechnology Meets Water Treatment, Dissemination Workshop of the Nano4water Cluster.

8.  Xiaolei Qu, Pedro J.J. Alvarez, Qilin Li (2013). Applications of nanotechnology in water and wastewater treatment. Water Research 47, 3931-3946.

9.  Xin Zhaoa,b, Lu Lva,b, Bingcai Pana,b, Weiming Zhanga,b, Shujuan Zhanga, Quanxing Zhanga,b., (2011). Polymer-supported nanocomposites for environmental application: A review, Chemical Engineering Journal, 170 ( 2–3), pp 381–394.