1. Use of Nano-scale materials in Water Purification OBASOGIE OYEMA EDOSA Dept. CHEMICAL ENGINEERING Dept. CHEMICAL ENGINEERING I chose this subject because I’m a master chemical engineering student and as such have to use distilled water in order to not poison the catalyst that I use to synthesize my carbon nanotubes. I was curious as to whether or not nanotechnology could provide a cheaper and more viable alternative. These principles could also be applied to providing drinking water from saltwater or contaminated sources. Federal University Of Technology Minna. E-mail add: oyema4sure@yahoo.comoyema4sure@yahoo.com : jamesoyes@yahoo.com Tel. Phone no: 08061562987

2. Water, water everywhere but nary a drop to drink! Over 75% of the Earths surface is covered in water Over 75% of the Earths surface is covered in water 97.5% of this water is salt water, leaving only 2.5% as fresh water 97.5% of this water is salt water, leaving only 2.5% as fresh water Nearly 70% of that fresh water is frozen in the icecaps of Antarctica and Greenland; most of the remainder is present as soil moisture, or lies in deep underground aquifers as groundwater not accessible to human use. Nearly 70% of that fresh water is frozen in the icecaps of Antarctica and Greenland; most of the remainder is present as soil moisture, or lies in deep underground aquifers as groundwater not accessible to human use. < 1% of the world's fresh water (~0.007% of all water on earth) is accessible for direct human uses. This is the water found in lakes, rivers, reservoirs and those underground sources that are shallow enough to be tapped at an affordable cost. < 1% of the world's fresh water (~0.007% of all water on earth) is accessible for direct human uses. This is the water found in lakes, rivers, reservoirs and those underground sources that are shallow enough to be tapped at an affordable cost.

3. Current Purification Methods Chemical –Activated Carbon –Chlorination –UV light Biological Biological –Bacteria to decompose waste –Oxidation of chemicals Mechanical Mechanical Settling Settling Sand or similar screening material Sand or similar screening material This water must of course be first purified to be fit for human consumption The methods used for this are:

4. Advanced types of Mechanical Filtration Some methods of mechanical filtering are actually capable of doing so on the nano-meter scale: Some methods of mechanical filtering are actually capable of doing so on the nano-meter scale: i.e. Diatom filtration Reverse Osmosis Reverse Osmosis

5. Diatom Filtration SEM micrographs of diatoms Diatoms are small single-celled marine algae that use silica to form hard shells. They have small pores that allow the flow of nutrients. a-d Examples of diatom morphologies (scale 10μm) e Valve openings (scale 1μm) Due to their small size and hard shells they can be packed together to form compact filters capable of filtering objects on the micron scale Unfortunately due to the relatively large size of their pores they are incapable of removing chemical impurities

6. Reverse Osmosis Pressure is applied across a membrane, driving pure water across while leaving concentrate behind Drawbacks: Most of the water wasted ~87% High pressures are needed to maintain flow Membrane rapidly loses efficacy

7. Nanotech Solutions Use of nano-tubes as filtering devices Use of nano-tubes as filtering devices Use of nano-particles as treatment agents Use of nano-particles as treatment agents

8. Methodology-Flow Chart 4.24g Fe (NO ₃ ) ₃.9H ₂ O + 3.06g Ni (NO ₃ ) ₂.6H ₂ O 8g CaCO ₃ 35mL Distilled Water Slurry Constant stirring, 1000 -2000 rpm Drying, 120 ⁰ C, 12h. Calcining, 500 ⁰ C, 15h. Catalyst Precursor Catalyst CVD, 700 ⁰ C, Argon 230 sccm, C ₂ H ₂ 180 sccm CNT growth Sieving, 150μm Sieve

9. Methodology Cont’d A known weight (1g) of CNT was subjected to 100ºC refluxed in a concentrated H ₂ SO ₄ /HNO ₃ of 20% by volume and diluted in 80% by volume of distilled water and refluxed for 3hours. The resulting solution was then filtered and washed with distilled water until a pH of 7 was attained. Subsequently followed by drying at a temperature of 120ºC for more than 12h in a muffler size furnace (Gallenkamp) and finally stored in an air-tight sample container. Purified Carbon nanotube sample Calcined Catalyst

10. SEM and TEM Images of The Purified Carbon nanotubes a. SEM micrograph of Purified Carbon nanotubeb. TEM micrograph of Purified Carbon nanotube

11. Views of the Filter 1.SEM picture of filter cartridge a.SEM of wall of cartridge (scale 100µm ) b.Same (scale 10µm) c.Lattice of Carbon Nanotubes can be seen (5µm)

12. How the Filter Works The nano-tubes act as a kind of molecular filter, allowing smaller molecules (such as water) to pass through the tubes, while contaminants are too large to pass through. Due to their electronic configuration smaller ions that would otherwise pass through are also blocked

13. Removal of bacteria using nanotube filter a, The unfiltered water containing E. coli bacteria b, The E. coli bacteria (marked by arrows) grown by the culture of the polluted water c, The filtration experiment d, The water filtered through nanotube filter e, The filtrate after culture showing the absence of the bacterial

14. Advantages Much less pressure required to move water across filter Much less pressure required to move water across filter Much more efficient Much more efficient Filter easily cleaned by back flushing Filter easily cleaned by back flushing Selective adsorption properties of nanotube surfaces Selective adsorption properties of nanotube surfaces Incredibly large surface area Incredibly large surface area Manmade nanotube membranes allow fluid flow 10,000 to 100,000 times faster than conventional fluid flow theory would predict Manmade nanotube membranes allow fluid flow 10,000 to 100,000 times faster than conventional fluid flow theory would predict Problems to Overcome Processes need to be designed to mass produce them Processes need to be designed to mass produce them By using a continuous spray pyrolysis method it has been possible to synthesize hollow carbon cylinders various centimeters in diameter and several centimeters long. Larger cylinders needed if this is to become practical By using a continuous spray pyrolysis method it has been possible to synthesize hollow carbon cylinders various centimeters in diameter and several centimeters long. Larger cylinders needed if this is to become practical

15. Rejection Values Species Sodium Chloride, NaCl99% Sodium Sulfate, Na 2 SO 4 99% Calcium Chloride, CaCl 2 99% Magnesium Sulfate, MgSO 4 >99% Sulfuric Acid, H 2 SO 4 98% Hydrochloric Acid, HCl90% Fructose, MW 180>99% Sucrose, MW 360>99% Humic Acid>99% Viruses99.99% Proteins99.99% Bacteria99.99% Even at the present stage these filters are shown to be very efficient Even better values can be obtained by connecting various filters in series

16. Conclusion Nano-technology could potentially lead to more effective means of filtration that not only remove more impurities than current methods but do so faster, more economically and more selectively Nano-technology could potentially lead to more effective means of filtration that not only remove more impurities than current methods but do so faster, more economically and more selectively