Nanofilters%20for%20Clean%20Water - PowerPoint PPT Presentation

View by Category
About This Presentation
Title:

Nanofilters%20for%20Clean%20Water

Description:

Nanofilters for Clean Water. STEM ED/CHM ... Despite the apparent abundance of clean water in most of the US and the ... Coffee filters block the grinds ... – PowerPoint PPT presentation

Number of Views:1973
Avg rating:3.0/5.0
Slides: 53
Provided by: mort163
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Nanofilters%20for%20Clean%20Water


1
Nanofilters for Clean Water
STEM ED/CHM Nanotechnology 2009
2
Todays Agenda
  • The problem adequate clean water
  • Kinds of filters
  • Desalination of salt water
  • Cleaning polluted water
  • Hands on nanofiltration experiment

3
The Problem Adequate Clean Water
  • Despite the apparent abundance of clean water
    in most of the US and the developed world, more
    than 20 of the Earths population lacks clean,
    safe drinking water.

Sources http//www.battelle.org/environment/image
s/water-drop.jpg
http//www.tribuneindia.com/2004/20040718/pb3.jpg
4
How is the Worlds Water Distributed?
  • Less than 3 of Earths water is fresh water
  • Most of it (97) is undrinkable salt water in the
    oceans
  • Of the fresh water, most is in ice caps and
    glaciers, and some is in ground water
  • Less than 1 is in more easily accessible surface
    water (lakes, swamps, rivers, etc.)

Source http//ga.water.usgs.gov/edu/watercyclesum
mary.htmlglobal
5
No Single Cause for the Water Crisis
  • Climate and geography
  • Lack of water systems and infrastructure
  • Depleting aquifers
  • Inadequate sanitation and pollution
  • 2.6 billion people (40 of the worlds
    population) lack access to sanitation systems
    that separate sewage from drinking water
  • Inadequate sanitation and no access to clean
    water have been highly correlated with disease
  • Will worsen with increasing population, affluence

6
How Can We Address the Water Crisis?
  • Use less water
  • More efficient irrigation, like drip irrigation
    cover irrigation ditches
  • Low-flow shower and toilets recycle gray water
  • Use native plants for crops and landscaping no
    lawns in AZ
  • Eat less meat (especially beef)
  • Fix leaky distribution systems (Quabbin
    reservoir)
  • Find new sources of clean water
  • Icebergs? Pump aquifers more and more? Use
    tankers?
  • Treat the undrinkable water that we have
  • Use reverse osmosis to desalinize salt (ocean)
    water
  • Clean polluted water using filters, chemicals,
    and UV light

7
Repairs to the leaky distribution system from the
Quabbin Reservoir located in Western
Massachusetts have reduced the demand for new
supplies for the Boston area.
8
Pollution in Fresh Water
  • Sewage is the most common
  • Pesticides and fertilizers
  • Industrial waste dumping
  • High levels of minerals from natural sources
  • Wells in Bangladesh have dangerous arsenic levels

Sources http//www.marenrecycling.com/polluted_wa
ter.JPG http//mainegov-images.info
rme.org/agriculture/pesticides/drift/mstblow1.gif
9
Water Filtration
  • Systems for cleaning polluted water typically use
    a series of filters to remove smaller and smaller
    particles
  • Seawater desalination facilities also use filters

10
Filters Are Everywhere
Window and door screens are filters they let
air in and keep out insects
11
Filters in the Home
Dryer filters remove lint
Air conditioning and furnace filters remove dust
12
Faucet screens trap small pebbles and other debris
Coffee filters block the grinds
13
Coffee Filter Scanning Electron Microscope Image
http//www.princeton.edu/pccm/outreach/scsp/mixtu
resandsolutions/diatoms/coffee_filter.html
14
Filters in the Car
Air, oil, fuel, and other filters remove harmful
materials
15
Filter Principles
  • Some filters block particles too big to pass
    through holes, like window screens or cell
    membranes

http//en.wikipedia.org/wiki/FileSchematic_size.j
pg
16
Filter Principles
  • Some filters use electrical forces to trap or
    block particles.
  • Electrostatic air cleaners place a charge on
    airborne particles, then collect the charged
    particles.

17
Filter Principles
  • Chemical filters are based on molecular forces
  • Activated carbon is very porous so it has a large
    surface area and can adsorb or react with large
    amount of material in water filtration systems

http//en.wikipedia.org/wiki/Activated_carbon
18
Filter Geometries
  • Some use a single layer such as a screen or a
    membrane with pores to block particles
  • Window screen
  • Others have an extended medium that gradually
    traps particles
  • Sand or gravel beds for water filtration

http//www.worldhungeryear.org/why_speaks/19_files
/image014.gif
19
Membrane Water Filters
  • A membrane is a thin material that has pores
    (holes) of a specific size
  • Membranes trap larger particles that wont fit
    through the pores of the membrane, letting water
    and other smaller substances through to the other
    side

http//www.alting.fr/index.aspx
20
Water Filtration Categories
  • Microfiltration
  • Ultrafiltration
  • Nanofiltration
  • Reverse Osmosis

21
Water Filtration Systems
  • Pebbles, sand, charcoal filter out large
    particles
  • Membranes filter out smaller particles
  • It is cost efficient to use a series of membranes
    to filter increasingly smaller particles and
    microorganisms

http//www.alting.fr/images/cross_flow_details.gif
22
Membrane Filter Technology
http//www.netl.doe.gov/technologies/pwmis/techdes
c/membrane/
23
Microfiltration
  • Typical pore size 0.1 microns (100 nm)
  • Very low pressure
  • Removes clay, suspended materials, bacteria,
    large viruses
  • Does not filter
  • small viruses, protein molecules, sugar, and salts

Microfiltration water plant, Petrolia, PA
A microfilter membrane
Sources http//www.waterworksmw.com/rack20120
202b.jpg http//www.imc.cas.cz/sympo/41micros/Ima
ge126.gif
24
Ultrafiltration
  • Typical pore size 0.01 microns (10 nm)
  • Moderately low pressure
  • Removes viruses, protein, and other organic
    molecules
  • Does not filter ionic particles like
  • lead, iron, chloride ions nitrates, nitrites
    other charged particles

An ultrafiltration plant in Jachenhausen, Germany
Source http//www.inge.ag/bilder/presse/bildmater
ial/referenzen/jachenhausen.jpg
25
Nanofiltration
  • Typical pore size 0.001 micron (1 nm)
  • Low to moderate pressure
  • Removes toxic or unwanted bivalent ions (ions
    with 2 or more charges), such as
  • Lead
  • Iron
  • Nickel
  • Mercury (II)

Nanofiltration water cleaning serving
Mery-sur-Oise, a suburb of Paris, France
Source http//www.wateronline.com/crlive/files/Im
ages/10899070-E891-11D3-8C1F-009027DE0829/newwater
1.gif
26
The Problem With Salt Water
  • People and most land plants and animals cannot
    use salt water
  • Seawater is much saltier than your body fluids or
    cells. When it enters the stomach, water from
    cells in that area comes rushing out to try to
    equalize the concentrations. Many cells may die
    due to sudden dehydration.

27
The Problem With Salt Water
  • Also, when your stomach fills rapidly with water
    from the cells, it causes you to throw up, so you
    lose almost twice as much water as the amount you
    originally drank.
  • Finally, human kidneys can only make urine about
    1/4 as salty as sea water. Therefore, to get rid
    of all the excess salt taken in by drinking salt
    water, you have to urinate more water than you
    drank, so you die of dehydration!

28
Desalination 2 Methods
  • Distillation use heat to evaporate salt water
    and condense water vapor
  • Expensive requires a lot of thermal energy
  • Sometimes uses the waste heat from a nuclear or
    other electric power plant to reduce costs
    (cogeneration)
  • Some pesticides and fertilizers have lower
    boiling points than water and are not removed
  • Some salts may migrate into distillate along
    walls
  • Water is tasteless and lacks minerals unless
    further treated
  • Used in Saudi Arabia, elsewhere

29
Desalination by Distillation
http//www.millipore.com/labwater/lw3/purification
techniques
30
Seawater Distillation Plants
Saudi Arabia www.water-technology.net/projects/shu
aiba/shuaiba5.html
Abu Dhabi Emirate
desalination.com
31
On the International Space Station
Water is recovered from urine by distillation in
a system installed in 2008 to reduce the amount
of water that needs to be launched.
http//www.water-technology.net/projects/iss_water
_recovery/
32
Desalination 2 Methods
  • Reverse osmosis Membrane with 0.1 nm holes, high
    pressure
  • A practical large scale desalination method, less
    expensive than distillation without cogeneration
  • Semipermeable membrane allows water to pass but
    not ions or other larger molecules

33
About Osmosis
  • Osmosis is a process that requires a
    semipermeable membrane
  • It is permeable to water, allowing water
    molecules to pass freely through its pores
  • It is impermeable to certain other molecules,
    which cannot pass through it
  • Youtube video

34
More water molecules strike the membrane on the
pure water side (left), causing a net diffusion
of water across the membrane. The water level
rises until equal numbers of water molecules
travel in each direction.
http//hyperphysics.phy-astr.gsu.edu/hbase/kinetic
/ospcal.html
35
How Osmosis Works
  • More molecules strike the membrane on the pure
    water side (a), causing a net diffusion of water
    across the membrane, raising the water level
    until there is equilibrium (b).
  • This explains the rise of sap in sugar maples
  • Could theoretically be a power source (river
    meets sea)

Solution
Kane and Sternheim General Physics
36
Reverse Osmosis
  • Equilibrium occurs when the pressure due to the
    water molecules is equal on both sides of the
    membrane (not equal concentrations)
  • The rate at which water molecules hit the
    membrane is determined by their partial pressure
  • Osmotic pressure is the pressure that must be
    applied to stop the flow of water across the
    membrane
  • Reverse Osmosis occurs when enough pressure is
    applied on the solution side to reverse the flow.
  • Youtube demo (reverse osmosis desalination)

37
Reverse osmosis plant for Bahrain (under
construction)
http//www.water-technology.net/projects/durrat-de
salination/
38
Tuos reverse osmosis plant provides 10 of
Singapores water
http//www.water-technology.net/projects/tuas/
39
Racks of elements containing reverse osmosis
membranes (Israel). This plant produces 13 of
the countrys domestic water supply. http//www.wa
ter-technology.net/projects/israel/
40
Nanofilters
  • Used to purify polluted water
  • Used as pre-filter for reverse osmosis in
    desalination systems
  • Lower pressure required
  • Lower operating costs
  • And special properties of nanosized particles can
    be exploited!
  • We can design new nanofilters that catch
    particles smaller than they would catch based on
    size alone
  • Scientists are exploring a variety of methods to
    build new nanomembranes with unique properties to
    filter in new and different ways

41
New Nanofilters are Unique!
  • Nanomembranes can be uniquely designed in layers
    with a particular chemistry and specific purpose
  • Insert particles toxic to bacteria
  • Embed tubes that pull water through and keep
    everything else out
  • Signal to self-clean

Image of a nanomembrane
Source http//sciencematters.berkeley.edu/archive
s/volume2/issue10/images/story2-2.jpg
42
New Nanomembranes I
  • Imagine having layers of membranes into which
    specialized substances are placed to do specific
    jobs
  • You can put a chemical in the filter that will
    kill bacteria upon contact!

Chemicals toxic to bacteria could be implanted in
nanomembranes
Source Unknown
43
New Nanomembranes II
  • Embed tubes composed of a type of chemical that
    strongly attracts (loves) water
  • Weave into the membrane a type of molecule that
    can conduct electricity and repel oppositely
    charged particles, but let water through

Water-loving tubes
Electricity moving through a membrane
44
1 nm Sized Nanopores Repel Electronegative Objects
  • 1-2 nm sized pores create an electric field over
    the opening
  • Repels negatively charged particles dissolved in
    water
  • Most pollutants from agriculture, industry, and
    rivers are negatively charged
  • But water can get through!

45
NanoCeram Filters
  • The active ingredient of the filter media is a
    nano alumina fiber, only 2 nm in diameter. The
    nano fibers are highly electropositive.
  • Separate particles by charge, not size pores are
    large (2 microns)
  • The filter retains all types of particles by
    electroadsorption, including silica, natural
    organic matter, metals, bacteria, DNA and virus.

http//www.argonide.com/publications/product_overv
iew.pdf
46
Making the Filter
  • The nano fibers are first dispersed and adhered
    to glass fibers. The nano alumina is seen as a
    fuzz on the two glass fibers.
  • Other fibers are added and the mixture is
    processed at a paper mill to produce a non-woven
    filter.
  • Because the nano alumina is dispersed, particles
    have easy access to the charged surface

47
Manufactured Like Paper (Low Cost)
  • Much like a standard filter, the NanoCeram
    electropositive fibrous filter media mechanically
    sieves particles larger than its average pore
    size.
  • However, the NanoCeram also adsorbs smaller
    particles throughout its entire fibrous
    structure,
  • Used as prefilter in reverse osmosis instead of
    ultrafilters.

48
Nanofilter Biotech Applications
  • Removal of contaminants from incoming water
  • Prefiltering for reverse osmosis filters instead
    of ultrafilters
  • Filtering endotoxins, bacteria and virus
    endotoxins
  • Filtering hazardous pharmaceutical waste before
    disposal
  • Separation of proteins

49
Nanofiltration Summary
  • At the nanoscale, filters can be constructed to
    have properties designed to serve a particular
    purpose
  • Scientists and engineers are now experimenting to
    create membranes that are low-cost yet very
    effective for filtering water to make it
    drinkable!
  • These inventions may help to solve the global
    water shortage

50
NanoSense Hands on Experiment I
  • Cleaning river water
  • Made from distilled water, salt, crushed leaves,
    dirt, sand, copper sulfate pentahydrate, iron
  • Filter with gravel, sand, activated charcoal,
    nanofilter
  • Use test strips for ions iron, copper,
    chlorine, nitrates, nitrites after each step

51
NanoSense Hands on Experiment II
  • Comparing ultrafiltration (25 nm pores) with
    nanofiltration (2000 nm pores, 2 nm fibers)
  • Use diluted ink with 2 nm particles
  • Compare clarity of filtered water, color of
    filter afterwards
  • Compare pressure required

52
References
  • www.millipore.com/labwater/lw3/purificationtechniq
    ues Maker of Millipore filters
  • nanosense.org/activities/finefilters/index.html
  • www.argonide.com/publications/product_overview.pdf
    Maker of argonide nanofilters
  • http//www.drinking-water.org/flash/splash.html
    National Academy of Sciences Kirkland Museum
  • http//www.understandingnano.com/water.html
  • http//www.brianlaks.com/nanofilters.htm
  • http//www.water-technology.net/
About PowerShow.com