This document provides an overview of nanotechnology applications in water treatment. It discusses how nanomaterials have properties like high surface area to volume ratio that allow them to be used to detect and remove contaminants from water. Some mechanisms by which nanomaterials can treat water include nanofiltration membranes that remove particles down to 0.001 microns, magnetic nanoparticles that can be easily separated from water, and ferritin which can transform toxic metals and chlorocarbons. The document examines how these nanotechnology approaches can provide lower cost and more effective alternatives to traditional water treatment methods.

1. [1]
Essay On
ENVIRONMENTAL APPLICATIONS OF
NANOTECHNOLOGY IN WATER
TREATMENT
Prepared by
Khaled Abdul-Khaliq M.Elkoomy
For B.Sc. degree of Science
(Environmental Sciences)
Level four
2016 - 2017

2. [2]
CONTENTS
PageSubjects
3Acknowledgements
4Introduction
6Properties of Nanomaterials
7Water Treatment
8Role of Nanomaterials in Water Treatment
9Mechanisms of water remediation
19Remove of Nanoparticles After water Treatment
20Environmental Risks
22References
30English Summary
31Arabic Summary

3. [3]
First of all, praise is due to almighty ALLAH
with His compassion and mercifulness to allow
me finalizing this project.
I would like to express my sincere gratitude to
my advisor Dr. Heba Allah M.Elbaghdady,
lecturer of Ecology, Zoology Department, Faculty
of Sciences, Mansoura University for the
continuous support of my research, for her
patience, motivation, profitable discussions and
immense knowledge. Her guidance helped me in
all the time of research and writing of this
manuscript.
I wish to thank Prof. Dr. Amoura Abou El-
Naga. Head of Zoology Department, Faculty of
Sciences, Mansoura University for her invaluable
help.
My sincere thanks also go to my parents,
brothers, sisters and class mates for their
invaluable help and encouragement.
Acknowledgements

4. [4]
Introduction
Nanotechnology is science, engineering, and technology conducted at the nanoscale, which
is about 1 to 100 nanometers. The ideas and concepts behind nanoscience and nanotechnology
started with a talk entitled “There‟s Plenty of Room at the Bottom” by physicist Richard
Feynman at an American Physical Society meeting at the California Institute of Technology
(CalTech) on December 29, 1959, long before the term nanotechnology was used. In his talk,
Feynman described a process in which scientists would be able to manipulate and control
individual atoms and molecules. Over a decade later, in his explorations of ultraprecision
machining, Professor Norio Taniguchi coined the term nanotechnology. It wasn't until 1981,
with the development of the scanning tunneling microscope that could "see" individual atoms,
that modern nanotechnology began [1].
„Nanotechnology‟ as a field has emerged in 1980s through convergence of K.E. Drexler‟s
theoretical and public work has now gained a worldwide attention among both the scientific
and public community [2]. Nanotechnology literally means any technology on a nanoscale
that has applications in the real world [3]. Nanotechnology refers most broadly to the use of
materials with nanoscale (1nm = 10-9
m) dimensions [4].Nanotechnology is defined as „„the
understanding and control of matter at dimensions between 1 and 100 nm, where unique
phenomena enable novel applications‟‟ [2]. Nanotechnology is usually defined as research,
development, manipulation, control or use of materials at that level [5-8].Nanotechnology
offers the ability to control matter at the nanoscale and create materials that have specific
properties with a specific function [9].
Nanotechnology and its products “nanomaterials” are being widely used across fields as
healthcare, industrial, electronics, cosmetics, pharmacology, bioclinical, biomedical fields and
other areas. Nanomaterials often differ from those of bulk materials in their physical and
chemical properties, so they call for specialized risk assessment [10-11].
In today‟s world where industries have been modernized and advanced, our environment is
filled with various types of pollutants emitted from human activities or industrial processes.
Examples of these pollutants are carbon monoxide (CO), chlorofluorocarbons (CFCs), heavy
metals (arsenic, chromium, lead, cadmium, mercury and zinc), hydrocarbons, nitrogen oxides,
organic compounds and sulfur dioxide. Human activities, such as oil, coal and gas
combustion, have significant potential to change emissions from natural sources [12]. In
addition to air pollution, there is also water pollution caused by various factors, including
waste disposal, oil spills and leakage of fertilizers, herbicides and pesticides, by-products of
industrial processes and combustion and extraction of fossil fuels [13]. Contaminants are

5. [5]
mostly found mixed in the air, water and soil. Thus, we need a technology that is able to
monitor, detect and, if possible, clean the contaminants from the air, water and soil.
Nanotechnology offers a wide range of capabilities and technologies to improve the
quality of existing environment. Nanomaterial is very small and the ratio of surface area to
volume ratio is high so that it can be used to detect very sensitive contaminants [14].
Environmental nanotechnology is considered to play a key role in the shaping of current
environmental engineering and science. Looking at the nanoscale has stimulated the
development and use of novel and cost-effective technologies for remediation, pollution
detection, catalysis and others [4]. Like the term „„nanotechnology‟‟ itself, „„environmental
nanotechnology‟‟ refers to a disconnected, broad, at times contradictory, set of technologies.
The advantage gained by adding „„environmental‟‟ to „„nanotechnology‟‟ is to narrow the
field down to those technologies that affect the conditions or the surroundings within which
we live.
For most people this would include the effects of the technology on species other than
humans. The field of environmental nanotechnology does not include cosmetic
nanotechnology, human health nanotechnology, computer technology, instrument and
apparatus technology, or the kinds of nanotechnology that improve manufacturing in ways not
connected to the environment [15]. There is the huge hope that nanotechnological applications
and products will lead to a cleaner and healthier environment [16].
The starting point for any discussion on the applications of nanotechnologies to the
environment is the ability of nanoscience to create new nanostructured materials with specific
properties to serve specific functions [17].
We will focus on environmental nanotechnology applications in water treatment.

6. [6]
Properties of Nanomaterials
Nanotechnology involves designing and producing substances or structures at a very small
or nano scale, 100 nanometres (100 millionth of a millimetre) or less to form nanomaterials.
Nanomaterials are one of the important products of nanotechnologies such as nano-scale
particles, tubes, rods, fibres etc. Nanoparticles are normally defined as being smaller than 100
nanometres in at least one dimension. Important features of nanomaterials include the average
size of the particle, size of the individual particles, surface area, structure etc. Nanomaterials
have manifold possible commercial and technological applications [18-19].
Specific important features of nanomaterials include the following:
PHYSICAL PROPERITIES:
1) Size, shape and ratio of width and height
2) Specific surface area
3) Property to stick together (agglomeration process)
4) Nature of the surface (smooth or rough)
5) Structure of the nanomaterial (crystal structure and any crystal defects)
6) Solubility.
CHEMICAL PROPERITIES:
1) Structure of the nanomaterial (molecular)
2) Composition of the nanomaterial, including purity, additives and known
impurities.
3) Physical state (solid, liquid or gas).
4) Surface chemistry of the nanomaterial.
5) Molecular interaction of the nanomaterial with different solvents [20-23].

7. [7]
Water Treatment
Water is a mythical substance whose material existence is secondary compared to the
symbolic value as it is manifested in our mind as the symbol of life. Sustainable supplies of
clean water are vital to the world‟s health, environment and economy. Currently the human
society is facing a tremendous crunch in meeting rising demands of potable water as the
available supplies of freshwater are decreasing due to extended droughts, population growth,
decline in water quality particularly of groundwater due to increasing groundwater and
surface water pollution, unabated flooding and increasing demands from a variety of
competing users. Water being a prime natural resource, a basic human need and a precious
national asset, its use needs appropriate planning, development and management.
Increasing population coupled with overexploitation of surface and groundwater over the
past few decades has resulted in water scarcity in various parts of the world. Wastewater is
increasing significantly and in the absence of proper measures for treatment and management,
the existing freshwater reserves are being polluted. Increased urbanization is driving an
increase in per capita water consumption in towns and cities. Hence there is a need to
recognize the requirement to manage existing water reserves in order to avoid future water
strain.
Today availability of safe drinking water is a concern. For almost all the water needs of the
country, groundwater is by far the most important water resource. Worldwide, according to a
United Nations Environment Programme (UNEP) study over 2 billion people depend on
aquifers for their drinking water.40 percent of the world‟s food is produced by irrigated
agriculture that relies largely on groundwater [24]. Groundwater constitutes about 95 per cent
of the freshwater on our planet (discounting that locked in the polar ice caps), making it
fundamental to human life and economic development. However the ever increasing scarcity
of groundwater coupled with diminishing water quality has posed a serious threat to the
population especially the rural community and has forced everyone to look at treatment of
groundwater because clean water is fast becoming an endangered commodity. The unabated
use has taken a serious toll on the availability of groundwater resources and as such the world
is facing a severe crunch in the availability of groundwater. So we have no other option to
move from “groundwater development” to “groundwater management” which means that we
have to move towards optimal usage of groundwater which would be sustainable in the long
run.
Today the onus is on everybody to provide safe drinking water and for that water treatment
processes need to be developed that are easy to implement, cost effective and sustainable in
the long run. Unsustainable uses of resources and indiscriminate applications of pesticides,

8. [8]
fertilizers, industrial pollutants are continuously disturbing the status of purity of
groundwater. Shallow aquifers generally suffer from agrochemicals, domestic and industrial
waste pollution.
Major water pollutants include microbes (like intestinal pathogens and viruses), nutrients
(like phosphates and nitrates), heavy metals, organic chemicals, oil, sediments and heat.
Virtually all industrial and goods-producing activities generate pollutants as unwanted by-
products. Heavy metals can contaminate the aquifer and subsequently can bioaccumulate in
the tissues of humans and other organisms [25]. Pollutants can take years to reach the
aquifers, but, once it reaches the water source, it is very difficult and costly to remove the
pollutants. More than 80% of sewage in developing countries is discharged without proper
treatment which can pollute the river systems, lakes and coastal water bodies [26]. Clean
water is a requirement for all properly functioning societies worldwide, but is often limited.
New approaches are continually being examined to supplement traditional water treatment
methods. These need to be lower in cost and more effective than current techniques for the
removal of contaminants from water. In this context also nanotechnological approaches are
considered. In this section the following application areas will be covered: nanoparticles used
as potent adsorbents, in some cases combined with magnetic particles to ease particle
separation; nanoparticles used as catalysts for chemical or photochemical destruction of
contaminants; nanosized zerovalent iron used for the removal of metals and organic
compounds from water; and nanofiltration membranes [27].
Role of Nanomaterials in Water Treatment
Nanomaterials are fast emerging as potent candidates for water treatment in place of
conventional technologies which, notwithstanding their efficacy, are often very expensive and
time consuming. This would be in particular, immensely beneficial for developing nations
where cost of implementation of any new removal process could become an important
criterion in determining its success. Qualitatively speaking nanomaterials can be substituted
for conventional materials that require more raw materials, are more energy intensive to
produce or are known to be environmentally harmful. Employing green chemistry principles
for the production of nanoparticles can lead to a great reduction in waste generation, less
hazardous chemical syntheses, and an inherently safer chemistry in general. However, to
substantiate these claims more quantitative data is required and whether replacing traditional
materials with nanoparticles does indeed result in lower energy and material consumption and
prevention of unwanted or unanticipated side effects is still open to debate. There is also a
wide debate about the safety of nanoparticles and their potential impact on the environment.

9. [9]
There is fervent hope that nanotechnology can play a significant role in providing clean water
to the developing countries in an efficient, cheap and sustainable way.
On the other hand, the potential adverse effects of nanoparticles cannot be overlooked
either. For instance the catalytic activity of a nanoparticle can be advantageous when used for
the degradation of pollutants, but can trigger a toxic response when taken up by a cell. So this
Janus face of nanotechnology can prove to be a hurdle in its widespread adoption. However as
mentioned before nanotechnology can step in a big way in lowering the cost and hence
become more effective than current techniques for the removal of contaminants from water in
the long run. In this perspective nanoparticles can be used as potent sorbents as separation
media, as catalysts for photochemical destruction of contaminants; nanosized zerovalent iron
used for the removal of metals and organic compounds from water and nanofiltration
membranes [28].
Mechanisms of Water Treatment
1. Nanofiltration
Membrane processes such as nanofiltration (NF) are emerging as key contributors to water
purification [29].Nanofiltration membranes (NF membranes) are widely used in water
treatment for drinking water or wastewater treatment. It is a low pressure membrane process
that separates materials in the 0.001-0.1 micrometer size. NF membranes are pressure-driven
membranes with properties between those of reverse osmosis and ultrafiltration membranes
and have pore sizes between 0.2 and 4 nm. NF membranes have been shown to remove
turbidity, microorganisms and inorganic ions such as Ca and Na. They are used for softening
of groundwater (reduction in water hardness), for removal of dissolved organic matter and
trace pollutants from surface water, for wastewater treatment (removal of organic and
inorganic pollutants and organic carbon) and for pretreatment in seawater desalination.
Bruggen & Vandercasteele (2003) have studied the use of nanofiltration to remove cations,
natural organic matter, biological contaminants, organic pollutants, nitrates and arsenic from
groundwater and surface water [30].
Carbon nanotubes filters are also gaining prominence in water treatment processes.
Srivastava et al. (2004) recently reported the successful fabrication of carbon nanotube filters
[31]. These new filtration membranes consist of hollow cylinders with radially aligned carbon
nanotube walls. They showed that the filters were effective at removing bacteria (Escherichia
coli and Staphylococus aureus) from contaminated water. The carbon nanotube filters are
readily cleaned by ultrasonication and autoclaving [32].

10. [10]
Nanoceramic filters are a mixture of nanoalumina fiber and micro glass with high positive
charge and can retain negatively charged particles. Nanoceramic filters have high efficiency
for removing virus and bacteria. They have high capacity for particulates and less clogging
and can chemisorb dissolved heavy metals [32].
2. Magnetic Nanoparticles
Magnetic nanoparticles offer advantages over non-magnetic nanoparticles because they
can easily be separated from water using a magnetic field. Separation using magnetic
gradients, the so-called high magnetic gradient separation (HGMS), is a process widely used
in medicine and ore processing [33]. This technique allows one to design processes where the
particles not only remove compounds from water but also can easily be removed again and
then be recycled or regenerated. This approach has been proposed with magnetite (Fe3O4),
maghemite (g-Fe2O3) and jacobsite (MnFe2O4) nanoparticles for removal of chromium(VI)
from wastewater [34-36]. Water-soluble CNTs have been functionalized with magnetic iron
nanoparticles for removal of aromatic compounds from water and easy separation from water
for re-use [37].
3. Ferritin
Ferritin is an iron-containing protein that is able of controlling the formation of
mineralized structures. Ferritin can be found in animals and plants and its function is to store
iron. Ferritin is formed when 24 polypeptides that are structurally similar to each other form a
cage-like protein structure [38]. Once the cage is formed, the iron molecules can enter the
cavity through the protein shell, where the mineralization process transforms iron molecules
into ferrihydrite nanoparticles.
Researchers have discovered the ability of ferritin to remediate toxic metals and
chlorocarbon under visible light or solar radiation [39]. The advantages of ferritin over
ordinary iron catalyst are: (1) ferritin does not react under photoreduction; and (2) it is also
more stable.
One obvious application of ferritin which has been proven in the laboratory is to change
chromium Cr (VI) into Cr (III) [40]. Cr (VI) is carcinogenic pollutant that is generally
contained in the industrial waste, while Cr (III) is formed naturally as a Cr compound, which
is less poisonous and insoluble in water [41].
4. Polymer Nanoparticles
Polymer nanoparticles have various uses, including water treatment and sunscreen. Using a
similar principle as surfactant micelles, polymeric nanoparticles have amphiphilic properties,
where each molecule has hydrophobic and hydrophilic parts. When water is available, the

11. [11]
polymer will form a polymer cell with a diameter of several nanometers inside the
hydrophobic part, while the hydrophilic part is outside. On polymer nanoparticles, crosslink
occurs prior to the aggregation of particles so that their stability is maintained [42].
In the application, polymeric nanoparticles offer a solution for commonly used
conventional surfactants to enhance remediation of hydrophobic organic contaminants using a
pump and treat system. These contaminants are usually classified into nonaqueous-phase
liquid which sticks very firmly to the ground so that it is difficult to cleanse, leading the
remediation process to be less and less effective. Therefore, a surfactant is needed to clean up
these contaminants. To date, the use of polymeric nanoparticles is still in the research phase
[43]. Several things that need to be studied before these ideas are applied include material
suitability for the soil type, recovery and recycling processes of the particles.
5. Bioactive Nanoparticles for Water Disinfection
Nanotechnology provides an alternative solution to clean germs in water, a problem that
has been getting worse due to the population explosion, growing need for clean water and
emergence of additional pollutants. One of the alternatives offered is antimicrobial
nanotechnology [44-45]. Li et al.[44] stated that several nanomaterials showed strong
antimicrobial properties through diverse mechanisms, such as (1) photocatalytic production of
reactive oxygen species that damage cell components and viruses (e.g. TiO2, ZnO and
fullerol),(2) compromising the bacterial cell envelope (e.g. peptides, chitosan,
carboxyfullerene, CNTs, ZnO and silver nanoparticles),(3) interruption of energy transduction
(e.g. Ag and aqueous fullerene nanoparticles) and (4) inhibition of enzyme activity and DNA
synthesis (e.g. chitosan).
Among all materials, TiO2 has been proposed to be the best candidate as it is stable in
water, nontoxic when ingested and low cost [46].
6. Aerogels and Solid Absorbants
The problem of oil spills in seawater is of great concern and has detrimental environmental
consequences. Currently, there are numerous bioremediation strategies that use microbial
cultures, enzyme additives or nutrient additives to clean up oil spills. The purpose of these
additives is to boost the natural nanotechnology of the microbial community to decompose
the oil material. Another method gaining acceptance is the use of aerogels (a nanomaterial)
modified with hydrophobic molecules to enhance the interaction with the oil. These aerogels
have very large surface areas so they can absorb 16 times their weight of oil. They act as a
sponge: once the oil has been absorbed, the „oil-soaked sponge‟ can be removed easily. The
problem is that these materials are expensive, so alternatives are under study [17].

12. [12]
7. Nanofibres and Nanobiocides
Nanofibres and nanobiocides provide a possibility to improve the quality of water filtration
membranes. For membrane fouling caused by bacteria in the water which reduce the quality
of water, inhibition of these bacteria can be caused by the surface-modified nanofibres. Based
on du Plessis‟ result, both polyvinyl alcohol (PVA) and polyacrylonitrile (PAN) nanofibres
containing silver nanoparticles have excellent antimicrobial activity, with PVA nanofibres
reducing between 91% and 99% of bacteria in a contaminated water sample and PAN
nanofibres killing 100%. Neither PVA nor PAN nanofibres leached silver into the water, as it
was concluded that PVA is a nontoxic and biodegradable synthetic polymer and PVA–silver
nanofibres have excellent antimicrobial activity [46].
8. Nanosemiconductors
Semiconducting nanoparticles made of TiO2 and ZnO are used in photocatalytic
remediation. Being semiconductors, these materials produce an electron-hole pair when
irradiated with a light having energy in the order of the material band gap. Both TiO2 and
ZnO are capable of transferring the charge to organic pollutants (such as halogenated
hydrocarbons) and induce their oxidation to less harmful by-products, such as CO2, H2O and
other species. Since TiO2 and ZnO are readily available and inexpensive, their use for
remediation has been studied for many years. Recently, nano-sized TiO2 and ZnO have been
considered, as these have more active surface given the same volume of material. The vision
is to create solar photocatalysis remediation systems where TiO2 or ZnO are used to convert
toxic contaminants, such as chlorinated detergents, into benign products using the radiation.
There is evidence that these semiconductors can photodegrade numerous toxic compounds,
but the technology requires improvements in term of efficiency, since TiO2 or ZnO only
absorb UV light which represents only 5 % of the solar spectrum. In this context,
nanotechnology could bring an improvement in two ways.
1. When noble metals like gold and platinum are chemisorbed to the TiO2 and ZnO
nanoparticles, the photocatalytic activity is accelerated. The reason is that the presence
of the metal helps to keep the electrons and holes from recombining in the
semiconductor and thereby increases the efficiency of the photocatalysis.
2. To increase the photoresponse window of TiO2 and ZnO from UV to visible light, the
nanoparticles can be modified with organic or inorganic dyes. This is an area of intensive
research [17].

13. [13]
9. Nanoscale Zerovalent Iron (nZVI)
Iron nanoparticles are quite useful component for nanoremediation. Iron at the nanoscale
was synthesized from Fe (II) and Fe (III), using borohydride as the reductant. The size of the
nanoscale zero-valent ironparticles are 10-100 nm. in diameter. They have a typical core shell
structure. The core consists primarily of zero-valent or metallic iron whereas the mixed valent
[i.e., Fe (II) and Fe (III)] oxide shell is formed as a result of oxidation of the metallic iron.
Nanoscale Zerovalent Iron (nZVI) is generally preferred for nanoremediation because of large
surface area of nanoparticles and more number of reactive sites than microsized particles and
it possess dual properties of adsorption and reduction [47]. The use of Nanoscale Zerovalent
Iron (nZVI) for groundwater purification has been the most widely investigated
environmental nanotechnological technique. It has been established that nanoscale metallic
iron is very effective in destroying a wide variety of common contaminants such as
chlorinated methanes, brominated methanes, trihalomethanes, chlorinated ethenes, chlorinated
benzenes, other polychlorinated hydrocarbons, pesticides and dyes[48]. The basis for the
reaction is the corrosion of zerovalent iron in the environment:
2Fe0 +4H+
+O2 →2Fe++
+2H2O
Fe0 +2H2O →Fe++
+H2 +2OH-
Typically, nZVI can be prepared by using sodium borohydride as the principle reductant
[49]. Some industries have started using an „iron powder‟ to clean up their new industrial
wastes. However, the „iron powder‟ (i.e. granular zero-valent iron with dimensions in the
micron range) is not effective for decontaminating old wastes that have already soaked into
the soil and water. Moreover, bioremediation using granular iron powder is often incomplete:
some chlorinated compounds are only partially treated and toxic by-products (such as DCE)
are still found after treatment. This effect is due to the low reactivity of iron powders. Another
matter of concern is the decrease in reactivity of iron powders over time, possibly due to the
formation of passivation layers over their surface.
Nanotechnology has offered a solution to this remediation technology in the form of iron
nanoparticles. These nanoparticles are 10 to 1 000 times more reactive than commonly used
iron powders. They have a larger surface area available for reacting with the organic
contaminant and their small size (1–100 nm) allows them to be much more mobile, so they
can be transported effectively by the flow of groundwater. The nanoparticles are not changed
by soil acidity, temperature or nutrient levels, so they can remain in suspension maintaining
their properties for extended periods of time to establish an in situ treatment zone [17]. The
reaction rates for nZVI are several times faster and also the sorption capacity is much higher
compared to normal granular iron. nZVI is also capable in removing dissolved metals from

14. [14]
solution, e.g. Pb and Ni. The metals are either reduced to zerovalent metals or lower oxidation
states [50].
Permeable Reactive Barrier (PRB) technology is a novel groundwater remediation method
which enables physical, chemical or biological in situ treatment of contaminated groundwater
by means of reactive materials [51]. Granular ZVI in the form of reactive barriers has been
used for many years at numerous sites all over the world for the remediation of organic and
inorganic contaminants in groundwater [52]. In recent years nZVI have gained ground as
attractive candidates using this technology. The reactive materials are placed in underground
trenches downstream of the contamination zone forcing it to flow through them and by doing
so, the contaminants are treated without water excavation. Generally, this cost-effective
removal technology causes less environmental harm than other methods [53].
Figure (1) Three approaches to application of ZVI forgroundwater remediation: (a)
conventional reactive barrier using granular ZVI; (b) injection of nZVI to form an
immobile reaction zone; (c) injection of mobile nZVI [54].
(a) Conventional reactive barrier using granular ZVI

15. [15]
(b) Injection of nZVI to form an immobile reaction zone
(c) Injection of mobile nZVI

16. [16]
Bimetallic iron nanoparticles, such as iron/palladium, have been shown to be even more
active and stable than zero-valent iron nanoparticles, thus further improving this remediation
technology. Finally, iron or bimetallic nanoparticles could be anchored on solid supports such
as activated carbon or silica for the ex situ treatment of contaminated water and industrial
wastes [17].
10. Porous Graphene Material
Wastewater remediation, the process of removing the contaminants from water, becomes a
critical issue. It is drawing much attention in developing functional materials that are able to
effectively adsorb, remove, and transfer contamination, such as oil spills, heavy metal ions,
and organic contaminants, from the water [55-76]. Generally, the performance of materials for
water remediation is associated with their specifi c surface area and surface behaviors, which
are mainly a function of geometrical structure and/or chemical composition. In addition, water
remediation requires that functional materials can be collected easily after usage, even
properly recycled and thus reused. Graphene, a monolayer of carbon atoms with closepacked
conjugated hexagonal lattices ( Figure 2 a), has the emerging properties with large theoretical
specifi c surface area (2630 m 2
g −1
) [77]. chemically enabled manipulating the amount of
oxygen containing groups and defects in graphene sheets (Figure 2 b and c) allows tuning
their hydrophilic-lipophilic balance [78-86].
Figure 2. Structural models of (a) graphene, (b) graphene oxide (GO) and (c) reduced
graphene oxide (rGO). Reproduced with permission[87] Copyright 2010, Elsevier.
Because of these, individual graphene sheets and their functionalized derivatives have been
used to remove metal ions and organic pollutants from water [88-104]. Although these
graphene- based nanomaterials show quite high adsorption performance as adsorbents, the
additional cost on the removal of these adsorbent materials and the secondary environmental
pollution were usually caused because such tiny materials are diffi cult to be collected

17. [17]
completely after usage. Therefore, it would be of scientifi c and technological importance to
assemble individual sheets into three-dimensional (3D) macroscopic structures which would
preserve the unique properties of individual graphene sheets, and offer easy collecting and
recycling after water remediationHerein, we would like to emphasize the recent development
of building bulky graphene materials with porous architectures for the water remediation. In
particularly, we will focus on the rational design and application of such bulky graphene
materials in cleanup of oil, removal of heavy metal ions, and elimination of water-soluble
organic pollutants (Figure 3). Finally, the future prospects of bulky grapheme materials for
environmental remediation are suggested.
Figure 3. Schematic illustration of graphene sheets assembled into bulky porous
architectures for water remediation.

18. [18]
Cleanup of Oil
Cleanup of oil from wastewater is a worldwide challenge and urgent issue due to the
increasing oily wastewater as well as the frequent oil spill accidents [105,106]. Currently,
many methods, such as skimming, adsorption, burning and biodegradation, have been used
for oil cleanup [104]. In general, there are two different kinds of adsorbents, i.e., natural
products and micro porous polymers. [104, 107-113] However, natural adsorbents, such as
wool fiber, activated carbon and expanded perlite often show low oil loading and adsorption
of water together with the oil, also cause other types of pollution during cleanup
[104].Furthermore, their capacity for cleanup of oil is hard to restore after usage. Compared to
natural adsorbents, micro porous polymers exhibit higher adsorption ability (5–25 g g −1
).
However, complex preparation procedures, high cost, and difficulties of scaling the
fabrication process limit their extensive application in the oil cleanup field [108].
Alternatively, bulky porous materials based on graphene and its derivatives exhibit highly
selective adsorption ability of oil from aqueous solution due to their high specific surface area
and superhydrophobic-oleophilic surface [108,114–128]. Furthermore, they can be easily
utilized during the oil cleanup process and collected after usage. In addition to easy
manipulation, they show excellent recycling ability. The uptake capacities of rGO foams are
up to about 37 times of its weight for a collection of motor oil and up to about 26 times for
organic solvents. Furthermore, the rGO foams still keep their original paper-like morphology
and high selective adsorption capability after more than 10 cycles [118] Superhydrophilicity
and high specific surface area make them an excellent candidate to adsorb oils and nonpolar
organic solvents without the suctioning of water [108,115–117].

19. [19]
Remove of Nanoparticles After Water Treatment
The use of nanoparticles in environmental applications will invariably lead to the
release of nanoparticles into the environment. Assessing their potential risks in the
environment requires an understanding of their mobility, bioavailability, toxicity and
persistence. Little is known about the possible exposure of aquatic and terrestrial life to
nanoparticles in water and soil. The rapidly growing use of engineered nanoparticles in a
variety of industrial scenarios and their potential for wastewater purification and drinking
water treatment raise the inevitable question how these nanoparticles can be removed in
the urban water cycle. Traditional methods for the removal of particulate matter during
wastewater treatment that have been in vogue include sedimentation and filtration.
However, due to the small sizes of nanoparticles the sedimentation velocities are
relatively low and significant sedimentation will not occur as long as there is no formation
of larger aggregates [53]. Common technologies such as flocculation might be
inappropriate to remove nanoparticles from water, which points to the need of finding new
solutions to the problem. Till now, membrane filtration (e.g. nanofiltration and reverse
osmosis) has been already applied for the removal of pathogens from water [129]
Hence, this technique can also be used for the removal of nanoparticles. Most
nanoparticles in technical applications today are functionalized in nature and therefore
studies using virgin nanoparticles may not be relevant for assessing the behaviour of the
actually used particles. Functionalization is often used to decrease agglomeration and
therefore increase mobility of particles. Unfortunately little is known to date about the
influence of functionalization on the behaviour of nanoparticles in the environment.

20. [20]
Environmental Risks
Exposure
Generally, the source of human and animal exposure to nanoparticles will be through the
food supply, through the air and water supply, and from medical application [7].The routes of
exposure for nonparticles include inhalation, dermal absorption, ingestion, and injection [5].
Environmental exposure to nanoparticles will come from several sources: intentional release,
for environmental remediation and unintentional release, and spillage or disposal of consumer
products. As with human and animal routes of exposure, there is a likelihood that soils, plants,
water, and the atmosphere will uptake nanoparticles through various pathways [130].
There is already evidence of occupational and environmental exposures to engineered
nanoparticles [5]. Occupational exposure to nanoparticles usually comes from inhalation of
airborne nanoparticles, though there is evidence that dermal exposure may be a significant
route as well [5,131]. Research is lacking on the current exposure levels of workers to
engineered nanoparticles, though much exists on their exposure to ultra-fine particles (which
include nanoparticles). Similarly, there only exists exposure data of non-engineered particles
to the general public. Though it is difficult to predict the amounts, researchers predict there
will eventually be measurable quantities in the environment.
Exposure to engineered nanoparticles is very difficult to measure. Even when the structure,
size and properties (morphology and composition) of the particles are known their interaction
with the environment varies greatly. As well, the traditional dose–response relationship does
not apply. Once taken up into the body, nanoparticles act differently from larger particles of
the same type [132].Though there is some variation, it seems that most current research
shows that surface area of the particles will be much more important to dose response than
mass concentration. What this means for exposure will vary by particle. The characteristics of
the particular nanoparticle in question will be much more important for exposure estimation
than has been the case in the past.
Nanoparticles in the environment are able to be transported rapidly through the air, water
and soil. This transportation is most important for exposure measurements that are relevant to
the general public. Transportation in each of these media will depend very much on
characteristics of the particles, such as size, charge, solubility, agglomeration diffusion,
deposition and gravitational settling. These characteristics will vary greatly from particle to
particle [133].
Once transported into the environment, nanoparticles have been shown to biodegrade and
to be bioavailable [5,133]. It has been shown that some fullerenes will biodegrade. Filley et
al. showed that wood decay fungi could metabolize C60 and C70 fullerenes [5]. Nano sized

21. [21]
particles are taken up by aquatic and marine filter feeders. As well, bacteria and cells can take
up nanosized particles. Depending on the characteristics of the particular particle, there is the
potential for bioaccumulation and exposure to nanoparticles once they have been transported
and deposited into the environment [134].
Risk of Nanotechnology
Although nanotechnology offers a broad range of potential uses and rapid advances,
this technology may also have unintended effects on human health and the environment.
Materials that are harmless in bulk forms can become highly toxic at the nanoscale, for
example, if they enter and build up in drinking water supplies and the food chain, and do not
biodegrade. The inhalation of airborne nanoparticles and the impact upon lung disease is a
specific concern, with recent studies showing a similar response by the human body to some
forms of CNTs as to asbestos particles, if inhaled in sufficient quantities [135]. These
concerns are exacerbated by the current poor understanding of the fate and behaviour of
nanoparticles in humans and the environment. However, it is very early in the development of
this technology, and the amount of testing has been relatively limited. Currently many
international organizations, such as the Royal Commission on Environmental Pollution
(RCEP) [136] and European Union [137], are aware that laboratory tests on some
nanomaterials suggest that they have properties which could cause concern. The
understanding of toxicity and potential health risks associated with nanomaterials is extremely
limited [138]. Nanotechnology risk assessment research for establishing the potential impacts
of nanoparticles on human health and the environment is crucial to aid in balancing the
technology‟s benefits and potential unintended consequences [139,140]. Scientific authorities
acknowledge this as a massive challenge, since monitoring the huge volume of diverse
nanoparticles being produced and used and their consequent impact is very difficult to track.
This strengthens our case for an increase in the amount and type of testing to assess whether
these theoretical risks are real, and to monitor their behaviour in the environment.

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English Summery
Nanotechnology is defined as „„the understanding and control of matter at dimensions
between 1 and 100 nm‟‟. Nanomaterils are very small & the ratio surface area to volume is
high, so that it can be used to detect very sensitive contaminants. Environmental
nanotechnology refers to the use of nanotechnology to solve environmental issues or
problems.
Water is essential source for life on our planet, but become polluted due to human
activities, urbanization, increasing populations…etc. Magnetic particles and
nanosemiconductors are some of mechanisms that used for water treatment.
Also the environmental fate and toxicity of a material are areas of concern in material
selection and design for water purification. Not much is known about the environmental fate,
transport and toxicity of nanomaterials. Thus it should be borne in mind that nanotechnology
can become a double edged sword and each positive and desired property of nanomaterials
could pose a risk to the environment.

31. [31]
‫العربي‬ ‫الملخص‬
‫تترواوح‬ ‫ابعاد‬ ‫علي‬ ‫المادة‬ ‫في‬ ‫والتحكم‬ ‫الفهم‬ ‫عن‬ ‫عبارة‬ ‫بأنها‬ ‫النانو‬ ‫تقنية‬ ‫تعرف‬‫من‬1‫الي‬111
‫النانو‬ ‫المواد‬ . ‫نانومتر‬‫لتحديد‬ ‫استخدامها‬ ‫يمكن‬ ‫لذلك‬ ‫كبيرة‬ ‫حجمها‬ ‫الي‬ ‫سطحها‬ ‫مساحة‬ ‫نسبة‬ ‫و‬ ‫صغيرة‬ ‫نية‬
‫او‬ ‫القضايا‬ ‫لحل‬ ‫النانو‬ ‫تكنولوجيا‬ ‫استخدام‬ ‫الي‬ ‫تشير‬ ‫بيئية‬ ‫النانو‬ ‫التكنولوجية‬ .‫الحساسية‬ ‫فائقة‬ ‫الملوثات‬
.‫البيئية‬ ‫المشكالت‬
‫الماء‬‫هو‬‫مصدر‬‫أساسي‬‫للحياة‬‫على‬،‫كوكبنا‬‫ولكن‬‫االنسان‬ ‫أنشطة‬ ‫بسبب‬ ‫ملوثا‬ ‫صار‬ ‫ه‬‫والتمدن‬
.‫السكانية..الخ‬ ‫والزيادة‬‫من‬ ‫النانونية‬ ‫الموصالت‬ ‫شبه‬ ‫و‬ ‫المغناطيسية‬ ‫الجزيئات‬‫التي‬ ‫الطرق‬ ‫بعض‬
‫المياه‬ ‫لمعالجة‬ ‫تستخدم‬.
‫أيضا‬‫ال‬‫مصير‬‫البيئي‬‫وسمية‬‫المواد‬‫المواد‬ ‫وتصميم‬ ‫اختبار‬ ‫في‬ ‫االهتمام‬ ‫محل‬ ‫في‬‫لتنقية‬‫المياه‬.‫ال‬
‫يعرف‬‫الكثير‬‫عن‬‫ال‬‫مصير‬‫البيئ‬‫ي‬‫والنقل‬‫وسمية‬‫المواد‬‫النانوية‬.‫وبالتالي‬‫فإنه‬‫ينبغي‬‫أن‬‫يوضع‬‫في‬‫االعتبار‬
‫أن‬‫تكنولوجيا‬‫النانو‬‫يمكن‬‫أن‬‫تصبح‬‫سالحا‬‫ذا‬‫حدين‬‫وكل‬‫ال‬‫خصائص‬‫اإليجابية‬‫والمرجوة‬‫من‬‫المواد‬
‫متناهية‬‫الصغر‬‫يمكن‬‫أن‬‫تشكل‬‫خطرا‬‫على‬‫البيئة‬.