Nanotechnologies for drinking water purification

Transcription

1 Nanotechnologies for drinking water purification T. Pradeep O pm O 2 nm H H

2 Gas hydrates to ozone chemistry

3 Water - prosperity, health, serenity, beauty, artistry, purity.. Claude Monet, Waterlilies, 1906 Oil on Canvas, The Art Institute of Chicago

4 Water - the vehicle of nature" ("vetturale di natura ) Leonardo Da Vinci Subject: Leonardo, Old Man with Water Studies, c Leonardo Old Man with Water Studies, c Leonardo Machine for raising water

5 Water and civilizations Mohenjodaro - well Aqueducts - The Assyrians - the first structure to carry water from one place to another - 7th century BC Archimedes screw and 212 BC - in the Netherlands Zoetermeer Mohenjodaro the great bath

6 Nitrates Fluoride Asbestos Microbes Heavy metals Chemicals, pesticides Water filtration: various media hof.povray.org/river.html

7 Permissible contamination molecules Time Contamination reaches molecular limits

8 An object for the nanotechnology - nanomaterials.

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10 USEPA has played a key role in determining the regulations for many toxic species found in drinking water Regulatory coverage of USEPA for safe drinking water has increased over 4 times since its inception, with revisions in regulations of many old contaminants

11 Classification of USEPA regulated contaminants It is very much clear from the regulations of USEPA, that halogenated organics are going to dominate the future regulative activity

12 Nanotechnology holds the future for effectively removing many drinking water contaminants - Number of contaminants present in extremely low concentration range (< molecules per glass of water) are quite significant - Many of those contaminants contain C-Cl bond or metallic in nature

13 Going into the future, a few trends are clearly visible RDX Acetochlor Prometon Metolachlor Terbacil Diazinon - Continued focus of USEPA regulatory activities on various other halogenated organics found in drinking water - Many of these organics are extremely stable in environment, and hence chemistry of novel materials is the need - Continuing with the history, the concentration limits for these organics is expected to be in sub-ppb range

14 Novel processes Drinking water purification Microbial Heavy metals Anions Organics Detection of contaminants in water Waste water purification Colour removal

15 Organics Pesticides Tansel and Nagarajan, Advances in Environmental Research 8, 2004, Traditional methods (activated carbon, membranes) Nanomaterials Metals, oxides, clays, dendrimers Plakas, Karabelas, Wintgens and Melin, Journal of Membrane Science 284, 2006,

16 5 nm 20 nm 2 nm A B Height (nm) C Distance (nm)

17 Absorbance I II III D nm 200 nm Wavelength (nm)

18 Nanocatalysis STM image of MoS 2 nanoflakes. From, Nanotechnology 14, pp (2003)

19 Reactions with halocarbons Nanoparticles of silver disappear in a chemical reaction.

20 Transmission Electron Microscopy Images of Nano-Particles 200 nm 100 nm Silver nano-particles ~70 nm Gold nanoparticles ~15-20 nm

21 The chemistry of halocarbons on metal surfaces was studied using CCl 4 as a model compound. 1.6 a b Plasmon excitation 0.25 Shift in plasmon Absorbance o p Wavelength (nm) Time interval was 20 minutes between the spectra. Spectrum a is due to the parent nanoparticle solution. The plasmon resonance shift is due to halocarbon binding (Ref: Fig 2). Reduction in the plasmon intensity due to Ag n AgCl is seen. Corresponding color changes are shown in the inset. Left: parent nanoparticle solution, right: after the reaction. Subsequent spectroscopy techniques showed complete halocarbons degradation on the metal nano-particle surfaces to form amorphous carbon and metal halides. Absorbance Wavelength (nm) Fig 1: Silver nano-particle based halocarbon degradation Fig 2: Gold nano-particle based halocarbon degradation

22 Other advanced scientific techniques confirm complete conversion of a number of halocarbons to metal chlorides. Fig 1: Benzylchloride adsorbed Fig 2: XRD of reaction product on Au nano surface confirming the presence of AgCl 4 For benzylchloride, we show that the molecule sits on the metal surface using mass spectrometry (ref: Fig 1). X-ray powder diffraction of the residue showed that we get AgCl for Ag nanoparticles. (ref: Fig 2). a and b are the data of the material formed in the reaction and the standard, respectively.

23 Results of other standard scientific methods Fig 1: IR and Raman Spectroscopy results Fig 2: ph and conductivity during the course of the reaction IR and Raman (Fig 1 inset) of the reaction products confirm the presence of carbon. a for the reaction product and b for CCl 4. Note the complete absence of C-Cl stretch in a. Fig 2 shows that halocarbon chemistry is complex.

24 The halocarbon chemistry can be used for other applications. For example, removing the metal cores from core-shell nanoparticles produces oxide-nanobubbles. 2 a Absorbance 1 b c 0 k Wavelength (nm) Time-dependent UV-visible spectra showing the reaction of CCl 4 with Ag@ZrO 2 core-shell nanoparticles. The progressive decrease in the absorbance is due to the time-dependent removal of Ag by CCl 4. TEM image of the oxide nanobubbles formed by the CCl 4 reaction. Inset shows a TEM image of a Ag@ZrO 2 coreshell nanoparticle. J. Mat. Chem. 2003

25 Chemistry with core-shell nanoparticles

26 Bacterial tests

27 (A) (B) 6 nm TEM images of ciprofloxacin@sio 2. Figure A is a large area image showing several particles and B is a close-up on one particle.

28 10µm Fluorescence image of E. coli DH 5 treated with FITC@SiO 2 Optical image Langmuir 2006

29 Reactions with pesticides Example Color of gold nanoparticles with endosulfan Endosulfan Pesticide removal Indian Patent granted International patent filed Technology commercialized Endosulfan concentration in ppm 2 Color changes with pesticide concentration Good response at lower concentrations Down to 0.1 ppm Adsorbed pesticides can be removed from solution 0 J. Environ. Monitoring. 2003

30 Some of the pesticides contain halocarbons whereas others have P or S, which can bind metal nanoparticles which is used for pesticide detection and extraction. Endosulfan Chlorpyrifos Malathion Absorbance a b c d e c Endosulfan Chlorpyrifos Malathion Absorbance a b t Wavelength(nm) Wavelength (nm) UV-visible spectra of gold nanoparticles showing the detection of endosulfan at different concentrations (b.2, c.10, d.100 and e. 250 ppm). Inset (A-D): Color changes of the solutions corresponding to traces a, b, c and d, respectively. Time dependent adsorption of endosulfan on gold nanoparticles and the corresponding spectral changes (a-t). The shifts in the plasmon band are due to the binding of the pesticide on the nanoparticle surface.

31 Supported Nanoparticles for Pesticide Removal Activated alumina globules (A) and gold (B) and silver (C) nanoparticles coated on the same. Silver nanoparticles coated on activated alumina (neutral) powder These can be made in ton quantities. 4 cm

32 Nanoparticle loaded alumina can remove pesticides. Absorbance b c r a Absorbance Time (minutes) Absorbance a b p q c Absorbance Time (minutes) s Wavelength (nm) Wavelength (nm) Absorption spectra showing the time dependent removal of 1 ppm chlorpyrifos (left) and malathion (right) by supported nanoparticles. The reduction in the absorbance feature with time is due to the adsorption of the pesticides on the nanosurface. Inset shows reduction in absorbance with time. Time interval between spectra was 20 minutes.

33 Other scientific tests conducted confirm the complete removal of commonly occurring pesticides from water Absorbance a b-e Wavelength (nm) % Transmittance (Arb.Units) % Transmittance (Arb.Units) A B b a b a W avenum ber ( cm -1 ) Absorption spectra showing the complete removal of pesticides when contaminated water was passed through a column of the nanomaterial. Trace a is the spectrum of the parent pesticide solution, b-e after passing through the nanoparticle-loaded column, in repeated experiments. Infrared spectra of the free pesticides (a) and that adsorbed on the nanoparticle surfaces (b) chlorpyrifos (A) and malathion (B).

34 Inauguration

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36 Pesticide removal from drinking water A B Time (minutes) Time (minutes) Product is marketed now A pesticide test kit has been developed > 25 ppb

37 Pollutants Harmless products TiO 2 CO 2 HCs

38 Polluted water Purified water

39 As adsorption Magnetic Fe 3 O 4 nanopartilcles Purification by circulation

40 Magnetic separation Magnetic clays for oil cleanup Antibody tagging Magnetic hyperthermia

41 E. F. Schumacher Pure water can be affordable..

42 Confocal Raman Microscope MALDI TOF MS Transmission Electron Microscope QTrap MS Nanoscience and Nanotechnology Initiative of the DST Ultramicrotome

43 Thank you all IIT Madras

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