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Nano for Air, Water and Land 

Pollution

Environment Nanotechnology

Liquid Phase

Solid Phase

Gas Phase

Soil RemediationImproving Air Quality

Water Treatment

The Good, the Bad & the Ugly

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The Ugly The Bad

• Nature of nanoparticles themselves

• Characteristics of the products made

• Manufacturing processes involved.

• As nano‐xyz is manufactured, what materials are used? 

• What waste is produced? • Are toxic substances used in the manufacturing of nano‐xyz? 

• What happens when nano‐xyzgets into the air, soil, water, or biota?  

The Good Nanotechnology has the potential to substantially benefit environmental quality and sustainability through

•Pollution prevention

•Treatment

•Remediation

•Information

Air

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Treatment and Remediation

• There are three major ways in which nanotechnology is being used to treat and reduce the different air pollutants; 

1. adsorption by nano‐absorptive materials,2. degradation by nanocatalysis, and3. filteration/separation by nanofilters.

1. Adsorption by nano‐adsorptive materials• Carbon nanostructures

• average pore diameter, pore volume, and surface area making them significant for industrial application as nanoadsorbents with high selectivity, affinity, and capacity. 

• Highly  reactive surface sites or structures bonds can also play an important role in the adsorption (attaching useful molecules

2. Degradation by Nanocatalysts

• Can use semiconductor materials photocatalytic properties

• Reaction occurs at surface, nano large surface areas

• TiO2 nanoparticles (self cleaning coatings• are capable to depollution atmospheric contaminants such as 

• nitrogen oxides, • VOCs and other pollutants into less toxic species

(Shen et al., 2015).

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CNT’s & Graphene

• Widely used for increasing the photocatalytic efficiency of TiO2 

• Composite of TiO2‐CNTs the electrons can be easily transferred through the CNTs and retard the electron‐hole recombination (Low et al., 2017). 

• The conduction band of CNTs lies at a more positive level compared to that of TiO2, hence the electrons can be moved from TiO2 to CNTs (Figure)

Bismuth  oxybromide (BiOBr)  nanoplate  microspheres  catalyst

(a) SEM images at low magnification, (b) high magnification of the BiOBrnanocatalyst and (c) the decrease in NO concentration by BiOBrnanocatalyst under UV-visible light irradiation (Source: Ai et al., 2015)

Metal oxide nanocatalysts

• Nanofibres of silver, iron, gold and manganese oxide are some of the recently used nanoscale metals and metal oxides can be used in environmental control to remove several volatile organic compounds from industrial smokestacks

Other examples

• Nanogold can eliminate carbon monoxide from indoor air at room temperature. 

• Au‐Pt co‐catalyst was found to be 100 times more active than that made of a conventional material for trichloroethylene (TCE) decomposition.

• As a concept, ZnO photocatalyst is currently being developed and is expected to have two functions to detect and reduce contaminants (Yadavet al., 2017)

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3. Filtration/separation by Nanofilters 

• Photos and SEM images of the MOFilter (metal‐organic) before and after PM capture

• The MOFilters show high removal efficiencies for PM2.5 and PM10

• (Source:Zhanget al., 2016)

Nanofibre‐coated filter media 

• air filtration (e.g. dust removal) at industrial plants• for filtration of the inlet air for gas turbines (Muralikrishnanet al., 2014).

• In particulate, nano‐structured membranes are suitable for several VOCs vapors (Scholtenet al., 2011).

Others:

• Silver nanoparticles and copper nanoparticles filters are widely used in the air filtration technology as antimicrobial materials to remove bioaerosols through air conditional processes. 

• One of the most environmental challenges is the removing of particulate matter (PM) which causes serious harm to public health. Metal−organic frameworks (MOFs) are crystalline materials with high porosity, tunable pore size, and rich functionalities, holding the promise for contaminant capture (Zhanget al., 2016). 

• Here, nanocrystals of four unique MOF structures are processed into nanofibrous filters. These MOFilters can also be effective and selective to adsorb toxic gases such as SO2when exposed in a stream of SO2/N2mixture.

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Soil Possibilities

• nanoscale iron is in use in full‐scale projects with encouraging success. 

• particles such as self‐assembled monolayers on mesoporous supports (SAMMS™), 

• dendrimers, • carbon nanotubes, and • metalloporphyrinogens. 

Advantages of nanoparticles

• Highly reactive due to large surface area to volume ratio, providing a greater number of reactive sites

• This allows for increased contact with contaminants, thereby resulting in rapid reduction of contaminant concentrations. 

• Nanoparticles may pervade very small spaces in the subsurface and remain suspended in groundwater, which would allow the particles to travel farther than macro‐sized particles and achieve wider distribution.

• However, bare iron nanoparticle may not travel very far from injection site. 

Bimetallic Nanoparticles (BNP’s)

• Good for contaminants in soil and groundwater. 

• BNPs consist of particles of elemental iron or other metals in conjunction with a metal catalyst, such as platinum (Pt), gold (Au), nickel (Ni), and palladium.

• combination of metals increases the kinetics of the oxidation‐reduction (redox) reaction, thereby catalyzing the reaction. Palladium and iron BNPs are commercially available and currently the most common. 

• In bench‐scale tests, BNPs of iron combined with palladium showed contaminant degradation two orders of magnitude greater than microscale iron particles alone (Zhang, 2006b). These particles were 99.9 percent iron and less than 0.1 percent palladium. 

Schematic of Pd/Au BNPs idealized as clusters, with a 4-nm Au core and variable Pd surface coverage from 0 to 100 percent (with corresponding Pd content). (Nutt, 2006)

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eZVI(zero valent iron)

• Remediation of chlorinated hydrocarbons• The product consists of ZVI surrounded by an oil‐liquid membrane that facilitates the treatment of chlorinated hydrocarbons.

• eZVI is made from food‐grade surfactant, biodegradable oil, water

• Outer layer is hydrophobic, as are the contaminants

Structure of an eZVI particle (modified from O’Hara, 2006)

Zero‐valent, or elemental, iron (ZVI) • In the presence of an oxidizing agent, Fe0 becomes oxidized to ferrous ions (Fe2+ ), and the two released electrons become available to reduce other compounds. 

• aerobic conditions, • 2Fe0 + 4H+ + O2 2Fe2+ + 2H2O OR  • 2Fe0 + 2H2O → 2Fe2+ + H2 + 2OH‐

• In addition to the above reactions, ZVI can also react with contaminants. 

• The figure illustrates a reaction that shows the reducing ability of elemental iron with a chlorinated hydrocarbon:

• The Fe0 (in the form of a BNP) transforms TCE to ethane, releasing Fe2+ ions and chloride ions. 

Nanosized titanium dioxide • Photocatalysis to mineralize a variety of 

herbicides, insecticides, and pesticides via photocatalysis and can convert other contaminants to less toxic compounds (Konstantinou, 2003). 

• When aqueous titanium dioxide suspensions are irradiated with light energy greater than 3.2 eV, electrons are generated according to the equation below: 

TiO2 + hν → e‐ + h+

• The electrons can reduce specific contaminants directly. 

• May also react with dissolved oxygen or the oxygen adsorbed on the surface of the titanium dioxide, reducing it to a superoxide radical anion that can oxidize specific contaminants. 

Scanning electron microscope image of titanium dioxide nanotubes (Chen, 2005)

SAMMS ‐ Self Assembled Monolayers on mesoporous supports

• Nanoporous ceramic substrate coated with a monolayer of functional groups tailored to preferentially bind to the target contaminant. 

• The functional molecules covalently bond to the silica surface, leaving the other end group available to bind to a variety of contaminants 

• Can be cleaned and re‐used• Contaminants successfully sorbed to SAMMS™ particles include radionuclides, mercury, chromate, arsenate, pertechnetate, and selenite Schematic of functionalized nano-sized pore within a

SAMMS™ particle (modified from Mattigod, 2004)

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Nano for soil

Agricultural Nanobiotechnology: Modern Agriculture for a Sustainable Futureedited by Fernando López‐Valdez, Fabián Fernández‐Luqueño

• From Table 7.1 it can be seen the removal of metal ions is one of the most common problems addressed using nanomaterials ( particularly nanoparticles)

• Zerovalent iron (ZVI) on if the most frequently cited• used in different forms in permeable barriers or treatment in situ of  soil for removal of a wide variety of contaminants

End-of-pipe management and cleanup of pollution

Treatment & Remediation

Iron Treatment Walls… Used in groundwater treatment for many years. Iron chemically reduces organic and inorganic environmental contaminants. Currently involves granular or “microscale” iron ( 50 m or 50,000 nm).

and NanotechnologyNanosized iron enhances the reaction. Enhanced further by coupling with other metals (Fe/Pd)* on the nanoscale. Nano Fe0 is more reactive and effective than the microscale. Smaller size makes it more flexible --penetrates difficult to access areas.

* Elliot and Zhang ES&T 2001, 35, 4922-4926

Many other examples:• Using gold nanoparticles embedded in a porous manganese oxide as a room temperature catalyst to breakdown volatile organic compounds in air.

• Using crystals containing nano sized pores to trap carbon dioxide.• Using a to remove nitrogen oxide from smokestacksnanocatalystcontaining cobalt and platinum

• Reducing the amount of platinum used in catalytic converters.• Converting carbon dioxide to methanol; which can be used to power fuel‐cells.

• Reducing emissions from power plants by converting carbon dioxide into nanotubes.

• Removal of carbon dioxide from industrial smoke stacks using:• Carbon nanotube based membranes• Nanostructured membranes• Genetically engineered enzymes

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Non‐ ZVI particles

Magnetic nanoparticles

• Magnetic nanoparticles have large surface areas relative to their volume and can easily bind with chemicals.

• Surface modified,  they can be used to bind with contaminants — such as arsenic or oil — and then be removed using a magnet.

Mat of potassium manganese nanowires. 

• A group of researchers at the Massachusetts Institute of Technology (MIT) have developed a “paper towel” for oil spills that is comprised of this membrane

• The nanowire membrane selectively absorbs oil with high efficiency. 

• Former sponges absorb water as well

• Cannot be heated to high temps to remove oil

• The oil can be recovered by heating the mat, which can then be reused. 

• My note: where does the burnt hydrocarbons go?

nZVI, bi‐metallic nanoscale particle (BNemulsified zero‐valent iron (eZVI) • May chemically reduce the following contaminants effectively: 

• perchloroethylene (PCE)• TCE, ci1, 2‐dichloroethylene (c‐DCE),• vinyl chloride (VC), and • 1‐1‐1‐tetrachloroethane (TCA), along with,• polychlorinated biphenyls (PCBs), halogenated aromatics, nitroaromatics, and metals such as arsenic or chromium. 

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Getting them in there• Usually site‐specific, dependent on the geology found and the form in which the nanoparticles will be injected. 

• Direct route of injection• existing monitoring wells, piezometers, or injection wells. 

• Recirculation involving injecting nanoparticles in upgradient wells while downgradient wells extract groundwater. 

• The extracted groundwater is mixed with additional nanoparticles and reinjected in the injection well.

• The wells keep the water in the aquifer in contact with the nZVI, and also prevent the larger agglomerated iron particles from settling out, allowing continuous contact with the contaminant. 

• Additional methods • direct push, pressure‐pulse technology, liquid atomization injection, pneumatic 

fracturing, and hydraulic fracturing. The direct push method involves driving direct‐push rods, similar to small drilling augers, progressively deeper into the ground. 

Schematic of two methods of groundwater remediation using nano‐iron

Water

Many of the techniques mentioned can be used for water treatment as welle.g. ZVI, membranes etc.

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• Slide of nanotec water purifier

Made of carbon nanotubes. Pore size: 0.0001‐0.001μm. Can remove virus, bacteria, 

suspended solids, large multivalent ions, dissolved organics, herbiscides, pesticides etc.

Greater efficiency compared to microfilters and ultrafilters.

Energy usage – Low.Nanofilter.

Developed by Argonne National Laboratory [3]

1. Nanofilters:

2. Nanosorbents:

Used majorly in water remediation. For removing inorganic and organic pollutants, from contaminated water.Nanoparticles used as sorbents.Nanoparticles can be functionalized with various chemical groups to increase their affinity towards target compounds.Nanocrystalline zeolites can remediate water containing cationic species such as ammonium and heavy metals. As well chemicals like 137Cs and 90Sr. [5].Magnetic nanoparticles bind with contaminants , such as oil and arsenic and removed using a magnet.

3. Nanocatalysts & redox active nanoparticles:Nanoparticles serve as catalysts.

Chemically degrade pollutants.

Scientists from IISc, Bangalore‐India are evaluating immobilized nano 

titanium‐dioxide particles for degrading organic as well inorganic  

pollutants.[6]

Nanoscale zerovalent Fe0 & bimetallic Fe0 detoxify organic & inorganic 

pollutants in aqueous solutions.

Fe0, Fe0/Pt0, Fe0/Pd0, Fe0/Ag0, Fe0/Ni0, Fe0/Co0 can reduce chlorinated 

alkanes, alkenes, chlorinated benzenes, pesticides, organic dyes, nitro 

aromatics, nitrates to less toxic and recalcitrant byproducts.[7]

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4. Bioactive nanoparticles:

Being evaluated to decrease use of chemical reagents used 

for disinfection.

MgO nanoparticles effective against Gram‐positive and 

Gram‐negative bacteria.[8]

Silver nanoparticles found effective against both Gram 

positive and negative. Especially, Staphylococcus aureus, 

E.coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. 

Nano Ag

Product How it works Importance Developers

Nanorust to remove

arscenic

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

poisoning of wells.

Rice University,

United States.

Desalination

membrane

A combination of

polymers and

nanoparticles that

draws in water ions

and repels dissolved

salts.

Already in the

market, this

membrane enables

desalination with

lower energy costs

than reverse osmosis.

University of

California, Los

Angeles and

NanoH2O

[9]Product How it works Importance Developers

Nanofiltration

Membrane

Membrane made up of

polymers with a pore

size ranging from 0.1-

10nm

Field tested to treat

drinking water in China

and desalinate water in

Iran. Using this membrane

requires less enrgy than

reverse osmosis.

Sachen Industries,

Korea.

Nanomesh waterstick A straw like filtration

device that uses carbon

nanotubes plaed on a

flexible, porous

material.

The waterstick cleans the

water as it is drunk.

Doctors in Africa are using

a prototype and the final

product is said to be

available at an affordable

cost in developing

countries.

Seldon Laboratories

, United States.

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Product How it works Importance Developers

World Filter Filter using a

nanofibre layer, made

up of polymers,

resins, ceramics and

other materials that

remove contaminants.

Designed specifically for

the household or

community level use in

developing countries. The

filters are effective, easy to

use and require no

maintenance.

KX Industries, US

Pesticide Filter Filter using

nanosilver to adsorb

and then degrade

three pesticides

commonly found in

the Indian water

supplies.

Pesticides are often found in

the developing countries

water supply. This pesticide

filter can provide a typical

Indian household with 6000

liters of clean water in one

year.

Indian Institute of

Technology,

Chennai, India and

Eureka Forbes

Limited, India.

Nanotec

• After the 2011 BKK floods

• 6 filtration steps one of which is the antimicrobial nanocoating ceramic filtration unit.

• Long lasting and no traces of silver particles are detected in the drinking water.

• Can be setup and operated using solar energy within 10‐15 minutes

Detection

• Nanotechnology can also detect water‐borne

• Contaminants like heavy metals.

• A new type of nanomaterial called nanostructured silica has been found to detect heavy metals

• It has large surface area and regular pores, has the capability of being able to extract heavy metals from wastewaters.

• Electrodes are separated with a small atomic gap so a few ions can be detect. Used for

• Process control, compliance and ecosystem monitoring, and data/information interfaces.

Sensors• Molecules adsorb on surface of nano

or micro cantilever, causes a change in surface stress, cantilever bends.

IBM--Berger et al., Science 1997 June 27; 276: 2021-2024

Single Molecule Detection

• Used to detect chemicals using either a specific reaction between analyte and sensor layer or chem/physisorption processes.

• Applications to bio-toxins as well.

Need to be • Low cost, rapid, precise, and ultra sensitive.• Operated remotely and continuously, in situ, and in real time.

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Kamat, P.V, et al. J.Phys.Chem. B 2002, 106,788-794.

Nanosized zinc oxide (ZnO) “senses” organic pollutants indicated by change in visible emission signal.

Sensing capability means that the energy-consuming oxidation stage only occurs when the pollutants present.

“Sense and Shoot” Approach to Pollution

Treatment

The ZnO “shoots” the pollutants via photocatalytic oxidation to form more environmentally benign compounds.

Multifunctionality and “smartness” is highly desirable for environmental applications.

Dual role of ZnO semicondouctor film as a sensor and photocatalyst

>300 nm

UV

Potential health and environmental risks.Integration of nanomaterials into existing water purification systems.Availability and cost.

Nanotechnology – a cautionary note

• Risk – toxicity and exposure• Nanoexposure studies – only on inhalation• Aquatic environment ?• Time‐lag (see also DDT history)• Safe particles 

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