Nanotechnologies for drinking water purification T. Pradeep pradeep@iitm.ac.in O 99.84 pm 104.45 O 2 nm H H
Gas hydrates to ozone chemistry
Water - prosperity, health, serenity, beauty, artistry, purity.. Claude Monet, Waterlilies, 1906 Oil on Canvas, The Art Institute of Chicago
Water - the vehicle of nature" ("vetturale di natura ) Leonardo Da Vinci Subject: Leonardo, Old Man with Water Studies, c. 1513 Leonardo Old Man with Water Studies, c. 1513 Leonardo Machine for raising water
Water and civilizations Mohenjodaro - well http://dspace.rice.edu/bitstream/1911/9176/773/lanma1890_135_a.jpg Aqueducts - The Assyrians - the first structure to carry water from one place to another - 7th century BC Archimedes screw - 287 and 212 BC - in the Netherlands Zoetermeer Mohenjodaro the great bath
Nitrates Fluoride Asbestos Microbes Heavy metals Chemicals, pesticides Water filtration: various media hof.povray.org/river.html
Permissible contamination 10 12 molecules Time Contamination reaches molecular limits
An object for the nanotechnology - nanomaterials.
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
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
Nanotechnology holds the future for effectively removing many drinking water contaminants - Number of contaminants present in extremely low concentration range (< 10 15 molecules per glass of water) are quite significant - Many of those contaminants contain C-Cl bond or metallic in nature
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
Novel processes Drinking water purification Microbial Heavy metals Anions Organics Detection of contaminants in water Waste water purification Colour removal
Organics Pesticides Tansel and Nagarajan, Advances in Environmental Research 8, 2004, 411 415 Traditional methods (activated carbon, membranes) Nanomaterials Metals, oxides, clays, dendrimers Plakas, Karabelas, Wintgens and Melin, Journal of Membrane Science 284, 2006, 291 300
5 nm 20 nm 2 nm A B Height (nm) 20 15 10 5 C 0 0 100 200 300 400 Distance (nm)
Absorbance 0.6 0.4 0.2 0.0 I II III D 100400 nm 200 nm 600 800 1000 Wavelength (nm)
Nanocatalysis STM image of MoS 2 nanoflakes. From, Nanotechnology 14, pp. 385-389 (2003)
Reactions with halocarbons Nanoparticles of silver disappear in a chemical reaction.
Transmission Electron Microscopy Images of Nano-Particles 200 nm 100 nm Silver nano-particles ~70 nm Gold nanoparticles ~15-20 nm
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 1.2 0.20 Absorbance 0.8 0.4 0.0 o p 300 400 500 600 700 800 900 1000 1100 Wavelength (nm) 400 500 600 700 800 900 1000 1100 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 0.15 0.10 0.05 0.00 Wavelength (nm) Fig 1: Silver nano-particle based halocarbon degradation Fig 2: Gold nano-particle based halocarbon degradation
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.
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.
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 400 500 600 700 800 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
Chemistry with core-shell nanoparticles
Bacterial tests
(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.
10µm Fluorescence image of E. coli DH 5 treated with FITC@SiO 2 Optical image Langmuir 2006
Reactions with pesticides Example Color of gold nanoparticles with endosulfan Endosulfan Pesticide removal Indian Patent granted International patent filed Technology commercialized 200 100 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
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 0.5 0.4 0.3 0.2 0.1 a b c d e c Endosulfan Chlorpyrifos Malathion Absorbance 0.4 0.3 0.2 0.1 a b t 0.0 400 500 600 700 800 900 1000 1100 Wavelength(nm) 0.0 400 500 600 700 800 900 1000 1100 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.
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
Nanoparticle loaded alumina can remove pesticides. Absorbance 0.15 0.10 0.05 b c r a Absorbance 0.16 0.12 0.08 0.04 0.00 0 100 200 300 400 500 600 Time (minutes) Absorbance 0.15 0.10 0.05 a b p q c Absorbance 0.12 0.08 0.04 0.00 0 100 200 300 400 500 600 Time (minutes) s 0.00 0.00 300 400 500 600 700 800 Wavelength (nm) 300 400 500 600 700 800 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.
Other scientific tests conducted confirm the complete removal of commonly occurring pesticides from water Absorbance 0.10 0.05 0.00 a b-e 400 600 800 1000 Wavelength (nm) % Transmittance (Arb.Units) % Transmittance (Arb.Units) 100 80 60 40 20 70 60 50 40 30 A B b a 3000 2500 2000 1500 1000 500 b a 3000 2500 2000 1500 1000 500 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).
Inauguration
Pesticide removal from drinking water A B Time (minutes) Time (minutes) Product is marketed now A pesticide test kit has been developed > 25 ppb
Pollutants Harmless products TiO 2 CO 2 HCs
Polluted water Purified water
As adsorption Magnetic Fe 3 O 4 nanopartilcles Purification by circulation
Magnetic separation Magnetic clays for oil cleanup Antibody tagging Magnetic hyperthermia
E. F. Schumacher Pure water can be affordable..
Confocal Raman Microscope MALDI TOF MS Transmission Electron Microscope QTrap MS Nanoscience and Nanotechnology Initiative of the DST Ultramicrotome
Thank you all IIT Madras