nbt lecture 30

8/12/2019 NBT Lecture 30

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NANOTECHNOLOGY APPLICATIONS

MBT 413 Nano Biotechnology Lecture 30


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Applications of nanotechnology in environment

Nanotechnology and water treatment

treatment and remediation

nanotechnology has the potential to contribute to long-term water quality,availability, and viability of water resources, such as through the use of

advanced filtration materials that enable greater water reuse, recycling,

and desalinization

sensing and detection

development of new and enhanced sensors to detect biological and

chemical contaminants at very low concentration levels in the

environment, including water

pollution prevention


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884 million people lack access to safe water supplies

approximately one in eight people

6 kilometres is the average distance African and Asian

women walk to fetch water

3.6 million people die each year from water-related

diseases

98 per cent of water-related deaths occur in the developing

world

84 per cent of water-related deaths are in children ages 0

14

43 per cent of water-related deaths are due to diarrhoea

65 million People are at risk of arsenic poisoning in the

Bangladesh, India and Nepal area


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Treatment and remediation

Nanotechnology

novel and effective in situ treatment technologies for groundwater

contaminant source zones

creation of novel nanoparticles with unique and tunable physical and

chemical properties

Their properties can be adjusted to make them highly reactive withcommon organic pollutants, and to minimize the formation of unwanted

toxic by-products.


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Nano-based products relevant to developing countries seeking to

improve water supplies

Product How it works Importance Developer

Nanosponge for rainwater

harvesting

A combination of polymers

and glass nanoparticles that

can be printed onto

surfaces like fabrics to soak

up water

Rainwater harvesting is

increasingly important to

countries like China, Nepal

and Thailand. The

nanosponge is much more

efficient than traditional mist-

catching nets

Massachusetts

Institute of

Technology, United

States

Nanorust to remove arsenic Magnetic nanoparticles of

iron oxide suspended in

water bind arsenic, which is

then removed with a

magnet

India, Bangladesh and other

developing countries suffer

thousands of cases of arsenic

poisoning each year, linked to

poisoned wells

Rice University,

United States

Desalination membrane A combination of polymers

and nanoparticles that

draws in water ions and

repels dissolved salts

Already on the market, this

membrane enables

desalination with lower energy

costs than reverse osmosis

University of

California, Los

Angeles and

NanoH2O
http://web.mit.edu/http://web.mit.edu/http://web.mit.edu/http://media.rice.edu/media/NewsBot.asp?MODE=VIEW&ID=9032http://newsroom.ucla.edu/portal/ucla/Today-s-Seawater-Is-Tomorrow-s-7410.aspx?RelNum=7410http://newsroom.ucla.edu/portal/ucla/Today-s-Seawater-Is-Tomorrow-s-7410.aspx?RelNum=7410http://newsroom.ucla.edu/portal/ucla/Today-s-Seawater-Is-Tomorrow-s-7410.aspx?RelNum=7410http://newsroom.ucla.edu/portal/ucla/Today-s-Seawater-Is-Tomorrow-s-7410.aspx?RelNum=7410http://newsroom.ucla.edu/portal/ucla/Today-s-Seawater-Is-Tomorrow-s-7410.aspx?RelNum=7410http://newsroom.ucla.edu/portal/ucla/Today-s-Seawater-Is-Tomorrow-s-7410.aspx?RelNum=7410http://media.rice.edu/media/NewsBot.asp?MODE=VIEW&ID=9032http://web.mit.edu/http://web.mit.edu/http://web.mit.edu/


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Nano-based products relevant to developing countries seeking to

improve water suppliesNanofiltration membrane Membrane made up of

polymers with a pore size

ranging from 0.1 to 10nm

Field tested to treat drinking

water in China and desalinate

water in Iran, using this

membrane requires less

energy than reverse osmosis

Saehan Industries,

Korea

Nanomesh waterstick A straw-like filtration device

that uses carbon nanotubes

placed on a flexible, porous,

material

The waterstick cleans as you

drink. Doctors in Africa are

using a prototype and the final

product will be made available

at an affordable cost in

developing countries

Seldon

Laboratories,

United States

World filter Filter using a nanofibre

layer, made up of polymers,resins, ceramic and other

materials, that removes

contaminants

Designed specifically for

household or community-leveluse in developing countries.

The filters are effective, easy

to use and require no

maintenance

KX Industries,

United States

Pesticide filter Filter using nanosilver to

adsorb and then degrade

three pesticides commonly

found in Indian watersupplies

Pesticides are often found in

developing country water

supplies. This pesticide filter

could provide a typical Indianhousehold with 6000 litres of

clean water over one year

Indian Institute of

Technology in

Chennai, India, and

Eureka ForbesLimited, India
http://www.saehan.com/http://www.seldontechnologies.com/http://www.seldontechnologies.com/http://www.iitm.ac.in/http://www.iitm.ac.in/http://www.iitm.ac.in/http://www.eurekaforbes.com/http://www.eurekaforbes.com/http://www.eurekaforbes.com/http://www.eurekaforbes.com/http://www.iitm.ac.in/http://www.iitm.ac.in/http://www.iitm.ac.in/http://www.seldontechnologies.com/http://www.seldontechnologies.com/http://www.saehan.com/


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Highly reactive nanoparticles such as-

1.nanoscale zerovalent iron (nanoiron or NZVI)

2.nanocatalysts (e.g., Au/Pd bimetallic nanoparticles

3.nanosized sorbents

to remediate contamination by organic and inorganic contaminants.

their small size (10500 nm) also provides an opportunity to deliver these

remedial agents to subsurface contaminants in situ, and provides access

to contamination trapped in the smallest pores in an aquifer matrix.

The high reactivity, and the potential for facile delivery directly to the

contaminant source, suggests that nanoparticles can accelerate the

degradation rate of contaminants in the source zone, and decrease the

time and cost of remediation relative to traditional treatment technologies

that address the plume.


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Nanoscale zerovalent iron and bimetallics (e.g., Fe0/Pd)

for the rapidin situ degradation of chlorinated organic compounds and

reduction of heavy metals in contaminant source zones

Nanoparticles can sequester groundwater contaminants (via adsorption

or complexation), making them immobile, or can degrade or transform

them to innocuous compounds.


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Reactive nanoparticles

TCE dechlorination by nanoiron.

Fe0 oxidation provides electrons

for the reduction of TCE. The Fe0 coreshrinks while the Fe3O4 oxide shell

grows. The particles are no longer

active once all of the Fe0 is oxidized.

Contaminant transformations by nanoiron, which is a strong reductant,

are typically redox reactions. When the oxidant or reductant is the

nanoparticle itself, it is considered a reactive nanoparticle.


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Catalytic nanoparticles

Nanoparticles that catalyze redox reactions but are not themselves

transformed are catalytic nanoparticles, which requires an additional

reagent that serves as the reductant or oxidante.g., Pd nanoparticles require H2 as a reductant

TCE dechlorination by catalytic Pd

particles. H2 is supplied as the

reductant for TCE dechlorination. In

principle, the Pd catalyst is not altered

by the reaction and can remain active

as long as H2 is supplied. In practice,

catalyst deactivation occurs and the

particle lifetime is finite. Catalyst

regeneration may extend the life of thearticle.


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Adsorbent nanoparticlesSome nanomaterials are engineered to strongly sequester contaminants.

The high affinity for the contaminant allows the nanoparticle to significantly

lower the aqueous phase concentrationsand serves to concentrate the

contaminants onto the particles.

Once concentrated onto the nanoparticles, the contaminants can be

removed along with the nanoparticles. This can be highly effective for

hydrophobic organic contaminants such as PCBs (polychlorinated

biphenyls) and PAHs(polyaromatic hydrocarbon) and for heavy metals.


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Factors affecting in si turemediation

remediation with any type of nanoparticle, it is important to know which

groundwater contaminants will respond to the treatment and which will

not.

It is also important to know how long the reactive or catalytic particles

will remain active as this will determine important operation decisions

such as how much to inject and when reinjection may be necessary.


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Reduction of chlorinated organic compounds (COC) or heavy metals

using Fe nanoparticles

Degradation of halogenated hydrocarbons, particularly chlorinated

solvents,occurs via a reductive process.

The Fe0 in the nanoiron is oxidized by the chlorinated solvent, which is

subsequently reduced. For chlorinated hydrocarbons, the reduction

typically results in the replacement of a chlorine atom with a hydrogen

atom.

For heavy metals, the metal, such as Pb(II) or Cr(VI), is reduced to its

zerovalent form on the nanoiron surface, or forms mixed (Fe-Metal)

precipitates that are highly insoluble.


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general half-reactions for the oxidation of iron and the reduction of

chlorinated organic compounds (COC) or heavy metals are given in Eqs.

1 to 3, where Me is a metal ion of charge a.


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In the case of nanoiron, or Fe0-based bimetallics, the reduction of the

contaminant is surface-mediated, and the particle itself is the reductant.

nanoiron particles have a high surface to-volume ratio and therefore have

high reactivity with the target contaminants.

The following generalizations can be made about the reactivity and

lifetime of all nanoparticulate remedial agents that are themselves the

reactive

Any process that affects the surface properties of the particles (e.g.,formation of an Fe-oxide on the surface) can affect theirreactivity.


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Any oxidant (e.g., O2 or NO3 ) competing with the target contaminant

will utilize electrons and may lower the rate and efficiency of the nanoiron

treatment for the target contaminants.

Reactive nanoparticles that serve as a reactant rather than a catalyst

will have a finite lifetime, the length of which depends on theconcentration of the target contaminant, the presence of competing

oxidants, and the selectivity of the particles for the desired reaction.


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Fe3O4 magnetic nanoparticles with humic acid can 1) greatly enhance the

stability of dispersed nanoparticles by preventing their aggregation; 2)

maintain the saturation magnetization by avoiding their oxidation; and 3)

enlarge the adsorption capacity for some heavy metals by making use of

the abundant carboxylic acid and phenolic hydroxyl functional groups of

humic acid to complex with heavy metal ions.

nbt lecture 30

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