use of nano technology in water purification

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INTRODUCTION

Clean water is a necessary requirement today. And in parts of the world, the demand is fast exceeding supply.

While water is plentiful, clean water for human consumption is often limited.

Global consumption of water is doubling every 20 years, more than twice the rate of human population growth.

New approaches are continually being examined and these need to be lower in overall cost, durable and or more effective than current option for the removal of contaminants from water.

It is in this context that nano-enabled technologies are being considered


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SHORTCOMINGS OF CONVENTIONALPURIFICATION METHODS

There are many procedures and processes to treat fluids for consumption, usedisposal, and other needs. Among the most prevalent are-

Sterilization - Adsorption, chemical treatments, ozone disinfection, and UV irradiation are

different technologies available for the sterilization of liquid. each of these technologies has limitations, including overall efficency, initial

& operating cost, byproduct risk, necessary pre- treatment of liquid,hazardous compounds used or produced, and other limitations.

Chlorine - Chlorine, though, carries with it significant risks including the facts that

chlorine residual is toxic to aquatic life, chlorine is corrosive and toxic,chlorine's oxidation of organic matter creates hazardous compounds, andsome parasitic species have shown resistance.


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Ultraviolet radiations -

At low dosages it may not be effective. Organisms can sometimes reverse and repair UV damage. Tubes can foul requiring frequent preventative maintenance. disposal of hazardous UV lamps can be expensive.

Desalination - The amount of electricity required for electro dialysis, and therefore its

operating cost, increases with increasing salinity of feed liquid.


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WHAT IS NANO?

Nanotechnology is the manipulation of individual atoms and molecules tocreate materials and devices with vastly different properties.

Nanomaterials are available today in the form of activated materials likecarbon or alumina.

These materials have high surface areas; however, because of the finepores, not all the water can easily reach the active surfaces and they areeasily plugged.

The small size of nanomaterials creates a major challenge. These fine particles or fibers cannot just be added to drinking water; rather,

they must be incorporated into filtration media in ways that allow for the

contaminants to readily come in contact with the active media.


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NANOTECH SOLUTIONS

Use of nano tubes in filtration Use of nano particles as treatment agents


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A possibility of patterning carbon

nanotube arrays in specific parts of amicro fabricated device allows easyintegration into microfluidic devices andgives this approach a great advantageover more conventional separationmedia.

Nanotube arrays can also be tuned to aparticular application since it is possibleto control nanotube size, density andorientation in the growth process.


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B. Removal of bacteria using nanotube filters Use of the nanotube filters was evaluated for the successful removal of

bacterial contamination from drinking water. A common pollutant of drinking water is the faecal bacterium Escherichia

coli is responsible for many waterborne diseases. Studies have shown that the nanotube filters fabricated could be used

successfully to obtain bacteria-free water for human consumption. Sterile saline water with light bacterial suspension was analysed. The suspension has a light pink and turbid (Fig. a) colour, due to the fact

that the bacteria colonies were scraped from the surface of MacConeyagar, which contains Phenol red as an indicator.


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This bacterial suspension was subjected to a filtration process through the

nanotube filters placed in a geometry similar to that used for endflowgeometry (Fig. c). The product of the filtration process is shown in Fig. d.The filtered fluid is

pure saline water and does not have a pink turbid colour suggesting thatafter filtration E.Coli bacteria have been eliminated.


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USE OF NANO PARTICLES AS TREATMENT DEVICESNano particles have many special properties, such as:

[A] High specific surface area [B] High adsorpability [C] Highly active in reaction

Nano particles in water treatment:Using nano particles in water treatment technology can obtain manyachievements.There are many approaches to use nano particles for water treatment:

Nano particles can be used to catalyze the reactions to remove organiccontaminants.

They can also be used in a emulsion to remove dense non aqueous phaseliquid (DNAPL).

Nano particles are also used as adsorbants or they can combine manyfunctions spontaneously.


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ADVANTAGES

Nanomaterials have a number of key physicochemical propertiesthat make them particularly attractive as separation media for waterpurification.

On a mass basis, they have much large surface areas than bulk particles.

Nanomaterials can also be functionalized with various chemicalgroups to increase their affinity toward a given compound.

Nanomaterials also provide unprecedented opportunities to developmore efficient water-purification catalysts and redox active mediadue their large surface areas and their size and shape-dependentoptical, electronic and catalytic properties.

Nanomaterials are also being used to develop chlorine-free biocidesthrough functionalization with chemical groups that selectivelytarget key biochemical constituents of waterborne bacteria andviruses.


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CONCLUSION

An increasing use of nanomaterials will be seen in thecoming decade because of the significant contaminantremoval potential that exists for improving theeffectiveness of water purification systems.

One approach is to use a porous ceramic mediacontaining the active nanomaterials.

This approach has been shown in the laboratory to beeffective for arsenic, lead and phosphate removal as well

as the breakdown of some organic contaminants. Field trials are needed to observe the long-term

advantages and practical-use applications of thesenanomedia products.


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use of nano technology in water purification

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