Removal of Heavy Metals From Water
Content
TEC
HNI
QU
ES
OF
RE
MO
VAL
OF
HEA
VY
MET
ALS
FRO
M
WA
TER
The
Univ
ersit
y of
Akro
n
Sub
mitte
d To:
Jiahu
a
Jack
Zhu,
Ph.D.
Assis
tant
Profe
ssor
Depa
rtme
nt of
Che
Contents
Abstract:................................................................................................................... 2
Abbreviations:......................................................................................................... 2
Introduction:............................................................................................................ 2
Techniques:.............................................................................................................. 3
Conventional Processes:..................................................................................... 3
Adsorption:........................................................................................................... 3
Membrane Filtration:.......................................................................................... 4
Electro Dialysis:................................................................................................... 4
Photo Catalysis:................................................................................................... 4
Conclusion:............................................................................................................... 4
References:.............................................................................................................. 5
Abstract:
Water is a life source and it can be contaminated with heavy metals. Heavy
metals can cause serious health problems once they enter the human body beyond
the permitted quantity. It is most important to remove heavy metals from
contaminated water. Different techniques are employed to remove heavy metals
from water in the market. This paper gives a basic idea about different techniques
and their significance. Initial metal concentration, pH, environmental impact, capital
investment and operational cost plays an important role in selecting the particular
technique. Adsorption and membrane filtration are commonly used techniques to
remove heavy metals from water in present days.
Abbreviations:
As- Arsenic
Cu- Copper
Cd- Cadmium
Pb- Lead
Cr- Chromium
Ni- Nickel
Hg- Mercury
Zn- Zinc
PH- Power of Hydrogen
Tio2- Titanium Dioxide
ZnO- Zinc Oxide
CdS- Cadmium Sulfide
CeO2- Cerium (IV) Oxide
ZnS- Zinc Sulfide
M2+- Dissolved Metal Ions
2(OH)- - Hydroxide Ions (Precipitant)
M (OH)2 - Insoluble Metal Hydroxide
Introduction:
The metals with atomic weights between 63.5 and 200.6 and a density higher
than 5 g per cubic meter are considered as heavy metals (Aba et al., 2013). They
are noted for their potential toxicity. Heavy metals in a polluted environment include
As, Cu, Cd, Pb, Cr, Ni, Hg and Zn. Heavy metals are highly soluble in the aquatic
environment and can cause serious health problems once they enter the human
body (Duruibe et al., 2007). If the concentration of the carcinogenic heavy metals in
the human body goes beyond the permitted, they cause serious health problems
like reduced growth, cancer, organ damage, kidney disease, nervous system
disorder, vomiting, hemorrhage, etc. (Babel and Kurniawan, 2004). The
contamination sources of heavy metals to water are mining and industrial wastes,
vehicle emissions, lead-acid batteries, fertilizers, paints, treated woods, etc. (Aba et
al., 2013). It is most important to remove heavy metals from water, with the help of
different techniques.
Techniques:
According to (Barakat, 2011), different techniques that are used to remove
heavy metals from water are:
Conventional Processes
Adsorption
Membrane Filtration
Electro Dialysis
Photo Catalysis
Conventional Processes:
It includes many processes like chemical precipitation, flotation, ion exchange
and electrochemical treatment. Chemical precipitation is the most commonly used
conventional process to remove heavy metals from inorganic effluent (Abas et al.,
2013). It is the process where dissolved metal ions are converted to the insoluble
solid phase by adjusting the pH with the help of precipitant agent like lime
(Benefield and Morgan, 1999). Typically, the metals are precipitated in the form of
hydroxide from the solution (Dean et al., 1972). The process of heavy metal removal
by chemical precipitation method is shown in the following equation (Wang et al.,
2004).
−¿ → M OH 2 ↓
2+¿+2 OH ¿
M¿
Chemical precipitation produces sludge that requires further treatment and
can turn out to be a costly method. Flotation is used to remove heavy metals from a
liquid phase using a bubble attachment, originated in mineral processing (Fu and
Wang, 2010). The main flotation processes for the removal of the heavy metal ions
are dissolved air flotation (DAF), ion flotation and precipitation flotation. The process
of plating out metal ions on a cathode surface and recovering the metals in
elemental state is known as the electrochemical treatment method. Electrochemical
treatment is not widely used because of the large capital investment and the ample
supply of electricity.
Adsorption:
Adsorption is a process where a substance is transferred from the liquid
phase to the surface of solid and gets bounded by physical or chemical interactions.
(Kurniawan and Babel, 2003). Activated Carbon has been frequently used as an
adsorbent, but it remains an expensive material since higher the quality of
activated carbon, the greater it costs (Huang et al., 1995). Agricultural waste is one
of the rich sources of low-cost adsorbents besides industrial by-product and natural
material (Abas et al., 2013). Agricultural and industrial wastes like rice husk, fly ash,
waste iron, iron slags, hydrous titanium oxide after chemical modification can be
used as adsorbents for the removal of heavy metals. (Lee et al., 2004). Thermally
converted carbon nanocomposites of micro/mesoporous nanocomposites from
decorated nanostructures on biomaterials (cotton fabric, cellulose fiber, sponge and
etc.) are being studied at Dr. Jiahua Zhu’s intelligent Composites Lab to remove
carcinogenic heavy metals from water. “The objective of this project is to reduce the
heavy metal level well below the EPA requirement with a much faster process of a
few minutes than conventional processes requires hours even days of operation”,
Dr. Zhu. It is fundamental process today because it provides with basic operating
conditions having wide pH range. The disadvantage of this process is low selectivity
and production of wastes.
Membrane Filtration:
Membranes only allow the materials of a certain size, shape or character.
Ultrafiltration, Reverse Osmosis, Nano filtration and Micro filtration methods use
membrane filtration process to remove heavy metals from contaminated water.
Ultrafiltration works at low transmembrane pressures for the removal of dissolved
and colloidal material (Landaburu et al., 2009). Reverse Osmosis uses a semipermeable membrane that allows the purified fluid (Shahalam et al., 2002). The
intermediate process between Reverse Osmosis and Ultrafiltration is known as Nano
filtration. Nano filtration is the promising technology for the removal of the heavy
metal ions such as nickel (Murthy and Chaudhari, 2008). These are cross flow,
pressure-driven membrane separation processes. Membranes are manufactured in
different configurations like tubular shapes, hollow fiber, and spiral. They all have
varying degrees of separation. (KOCH Membrane Systems). It needs small space for
installation, and it does have a high separation selectivity but because of
membrane fouling, it has a high operational cost.
Electro Dialysis:
Ionized species in the solution are passed through an ion exchange
membrane by applying an electric potential. Membranes either have anionic or
cationic characteristics. Anions move towards anode and cations move towards
cathode crossing the anionic or cationic membrane. Electro Dialysis is a promising
method for heavy metals removal from water. Drinking and process water is
produced from brackish and seawater with the help of Electro Dialysis process
(Sadrzadeha et al., 2009). It does provide high separation selectivity, but it has
high operational cost due to membrane fouling and energy consumption.
(Rockstraw and Scamehorn).
Photo Catalysis:
The metal ion is reduced with the help of various semiconductors like Tio 2,
ZnO, CdS, CeO2, ZnS, etc. as the photocatalyst. Electron holes are created by the
incident light that can oxidize organic contaminants and the electrodes released are
used to reduce the metal ions in the same waste stream. (Zhang and Itoh, 2006). It
removes organic pollutants and metals simultaneously with less harmful byproducts. The main drawback is that it needs a long time and has limited
applications.
Conclusion:
The removal of heavy metals from water depends on the concentration of the
heavy metals. The high concentrated metals can be precipitated and removed by
varying the pH, but it produces sludge and requires further treatment. Adsorbents
and membrane filtration are the most used technologies for removal of heavy
metals from waste water. Activated carbon is frequently used as an adsorbent, but it
remains an expensive material. The research and production of low-cost adsorbents
have gathered an attention in present life which will lead to safer and economical
method for the elimination of heavy metals from water. Membrane filtration is a
widely used method but it has a high operational cost due to membrane fouling.
Initial metal concentration, pH, environmental impact, capital investment and
operational cost should be considered before selecting the particular technique.
References:
S. Babel, T.A. Kurniawan. “Cr (VI) removal from synthetic wastewater using coconut
shell charcoal and commercial activated carbon modified with oxidizing agents
and/or chitosan.” Chemosphere, 54 (7) (2004): 951–967.
M.A. Barakat. “New trends in removing heavy metals from industrial wastewater.”
Arabian Journal of Chemistry, Volume 4, Issue 4, October (2011): 361-377
T.A. Kurniawan, G.Y.S. Chan, W.H. Lo, S. Babel. “Physio-chemical treatment
techniques for waste water laden with heavy metals.” Chem. Eng. J., 118 (2006):
83-98
T.Y. Lee, J.W. Park, J.H. Lee. “Waste green sands as a reactive media for the removal
of zinc from water.” Chemosphere, 56 (2004): 571-581
David A. Rockstraw, John F. Scamehorn. “Removal of heavy metals from water by
electrodialysis in the presence of acids and salts.” University of Oklahoma, Norman,
Oklahoma 73019
F.S. Zhang, H. Itoh. “Photocatalytic oxidation and removal of arsenite from water
using slag-iron oxide- TiO2 adsorbent.” Chemosphere, 65 (1) (2006): 125-131
J.O. Duruibe, M.O.C. Ogwuegbu, J.N. Egwurugwu. “Heavy metal pollution and human
biotoxic effects.” International Journal of Physical Sciences Vol. 2 (5) (2007): 112118
John G. Dean, Frank L. Bosqui, Kenneth H. Lanouette. “Removing heavy metals from
waste water.” Environ. Sci. Technol. 6 (6) (1972): 518-522
L.D. Benefield, J.M. Morgan. “Water Quality and Treatment.” R.D. Letterman (Ed.),
McGraw-Hill Inc., NY (1999):10.1–10.57
L.K. Wang, D.A. Vaccari, Y. Li, N.K. Shammas. “Physiochemical Treatment Processes.”
Humana Press, Vol. 3 (2004): 141-198
Chihpin Huang, Ying-Chien chung, Ming-Ren Liou. “Adsorption of Cu (II) and Ni (II) by
pelletized biopolymer.” Institute of Environmental Engineering, National Chiao Tung
University, (75) (1995)
J. Landaburu- Aguirre, V. Garcia, E. Pongracz, R.L. Keiski. “The removal of zinc from
synthetic wastewaters by micellar-enhanced ultrafiltration: statistical design of
experiments.” Desalination, 240 (2009): 262-269
A.M. Shahalam, A. Al-Harthy, A. Al-Zawhry. “Feed water pretreatment in RO systems
in the Middle East.” Desalination, 150 (2002): 235-245
Z.V.P. Murthy, L.B. Chaudhari. “Application of nanofiltration for the rejection of nickel
ions from aqueous solutions and estimation of membrane transport parameters.” J.
Hazard Mater, 160 (2008): 70-77
M. Sadrzadeha, T. Mohammadi, J. Ivakpour, N. Kasiri. “Neural network modelling of
Pb2+ removal from waste water using electrodialysis.” Chem. Eng. Process, 48
(2009): 1371-1381
HNI
QU
ES
OF
RE
MO
VAL
OF
HEA
VY
MET
ALS
FRO
M
WA
TER
The
Univ
ersit
y of
Akro
n
Sub
mitte
d To:
Jiahu
a
Jack
Zhu,
Ph.D.
Assis
tant
Profe
ssor
Depa
rtme
nt of
Che
Contents
Abstract:................................................................................................................... 2
Abbreviations:......................................................................................................... 2
Introduction:............................................................................................................ 2
Techniques:.............................................................................................................. 3
Conventional Processes:..................................................................................... 3
Adsorption:........................................................................................................... 3
Membrane Filtration:.......................................................................................... 4
Electro Dialysis:................................................................................................... 4
Photo Catalysis:................................................................................................... 4
Conclusion:............................................................................................................... 4
References:.............................................................................................................. 5
Abstract:
Water is a life source and it can be contaminated with heavy metals. Heavy
metals can cause serious health problems once they enter the human body beyond
the permitted quantity. It is most important to remove heavy metals from
contaminated water. Different techniques are employed to remove heavy metals
from water in the market. This paper gives a basic idea about different techniques
and their significance. Initial metal concentration, pH, environmental impact, capital
investment and operational cost plays an important role in selecting the particular
technique. Adsorption and membrane filtration are commonly used techniques to
remove heavy metals from water in present days.
Abbreviations:
As- Arsenic
Cu- Copper
Cd- Cadmium
Pb- Lead
Cr- Chromium
Ni- Nickel
Hg- Mercury
Zn- Zinc
PH- Power of Hydrogen
Tio2- Titanium Dioxide
ZnO- Zinc Oxide
CdS- Cadmium Sulfide
CeO2- Cerium (IV) Oxide
ZnS- Zinc Sulfide
M2+- Dissolved Metal Ions
2(OH)- - Hydroxide Ions (Precipitant)
M (OH)2 - Insoluble Metal Hydroxide
Introduction:
The metals with atomic weights between 63.5 and 200.6 and a density higher
than 5 g per cubic meter are considered as heavy metals (Aba et al., 2013). They
are noted for their potential toxicity. Heavy metals in a polluted environment include
As, Cu, Cd, Pb, Cr, Ni, Hg and Zn. Heavy metals are highly soluble in the aquatic
environment and can cause serious health problems once they enter the human
body (Duruibe et al., 2007). If the concentration of the carcinogenic heavy metals in
the human body goes beyond the permitted, they cause serious health problems
like reduced growth, cancer, organ damage, kidney disease, nervous system
disorder, vomiting, hemorrhage, etc. (Babel and Kurniawan, 2004). The
contamination sources of heavy metals to water are mining and industrial wastes,
vehicle emissions, lead-acid batteries, fertilizers, paints, treated woods, etc. (Aba et
al., 2013). It is most important to remove heavy metals from water, with the help of
different techniques.
Techniques:
According to (Barakat, 2011), different techniques that are used to remove
heavy metals from water are:
Conventional Processes
Adsorption
Membrane Filtration
Electro Dialysis
Photo Catalysis
Conventional Processes:
It includes many processes like chemical precipitation, flotation, ion exchange
and electrochemical treatment. Chemical precipitation is the most commonly used
conventional process to remove heavy metals from inorganic effluent (Abas et al.,
2013). It is the process where dissolved metal ions are converted to the insoluble
solid phase by adjusting the pH with the help of precipitant agent like lime
(Benefield and Morgan, 1999). Typically, the metals are precipitated in the form of
hydroxide from the solution (Dean et al., 1972). The process of heavy metal removal
by chemical precipitation method is shown in the following equation (Wang et al.,
2004).
−¿ → M OH 2 ↓
2+¿+2 OH ¿
M¿
Chemical precipitation produces sludge that requires further treatment and
can turn out to be a costly method. Flotation is used to remove heavy metals from a
liquid phase using a bubble attachment, originated in mineral processing (Fu and
Wang, 2010). The main flotation processes for the removal of the heavy metal ions
are dissolved air flotation (DAF), ion flotation and precipitation flotation. The process
of plating out metal ions on a cathode surface and recovering the metals in
elemental state is known as the electrochemical treatment method. Electrochemical
treatment is not widely used because of the large capital investment and the ample
supply of electricity.
Adsorption:
Adsorption is a process where a substance is transferred from the liquid
phase to the surface of solid and gets bounded by physical or chemical interactions.
(Kurniawan and Babel, 2003). Activated Carbon has been frequently used as an
adsorbent, but it remains an expensive material since higher the quality of
activated carbon, the greater it costs (Huang et al., 1995). Agricultural waste is one
of the rich sources of low-cost adsorbents besides industrial by-product and natural
material (Abas et al., 2013). Agricultural and industrial wastes like rice husk, fly ash,
waste iron, iron slags, hydrous titanium oxide after chemical modification can be
used as adsorbents for the removal of heavy metals. (Lee et al., 2004). Thermally
converted carbon nanocomposites of micro/mesoporous nanocomposites from
decorated nanostructures on biomaterials (cotton fabric, cellulose fiber, sponge and
etc.) are being studied at Dr. Jiahua Zhu’s intelligent Composites Lab to remove
carcinogenic heavy metals from water. “The objective of this project is to reduce the
heavy metal level well below the EPA requirement with a much faster process of a
few minutes than conventional processes requires hours even days of operation”,
Dr. Zhu. It is fundamental process today because it provides with basic operating
conditions having wide pH range. The disadvantage of this process is low selectivity
and production of wastes.
Membrane Filtration:
Membranes only allow the materials of a certain size, shape or character.
Ultrafiltration, Reverse Osmosis, Nano filtration and Micro filtration methods use
membrane filtration process to remove heavy metals from contaminated water.
Ultrafiltration works at low transmembrane pressures for the removal of dissolved
and colloidal material (Landaburu et al., 2009). Reverse Osmosis uses a semipermeable membrane that allows the purified fluid (Shahalam et al., 2002). The
intermediate process between Reverse Osmosis and Ultrafiltration is known as Nano
filtration. Nano filtration is the promising technology for the removal of the heavy
metal ions such as nickel (Murthy and Chaudhari, 2008). These are cross flow,
pressure-driven membrane separation processes. Membranes are manufactured in
different configurations like tubular shapes, hollow fiber, and spiral. They all have
varying degrees of separation. (KOCH Membrane Systems). It needs small space for
installation, and it does have a high separation selectivity but because of
membrane fouling, it has a high operational cost.
Electro Dialysis:
Ionized species in the solution are passed through an ion exchange
membrane by applying an electric potential. Membranes either have anionic or
cationic characteristics. Anions move towards anode and cations move towards
cathode crossing the anionic or cationic membrane. Electro Dialysis is a promising
method for heavy metals removal from water. Drinking and process water is
produced from brackish and seawater with the help of Electro Dialysis process
(Sadrzadeha et al., 2009). It does provide high separation selectivity, but it has
high operational cost due to membrane fouling and energy consumption.
(Rockstraw and Scamehorn).
Photo Catalysis:
The metal ion is reduced with the help of various semiconductors like Tio 2,
ZnO, CdS, CeO2, ZnS, etc. as the photocatalyst. Electron holes are created by the
incident light that can oxidize organic contaminants and the electrodes released are
used to reduce the metal ions in the same waste stream. (Zhang and Itoh, 2006). It
removes organic pollutants and metals simultaneously with less harmful byproducts. The main drawback is that it needs a long time and has limited
applications.
Conclusion:
The removal of heavy metals from water depends on the concentration of the
heavy metals. The high concentrated metals can be precipitated and removed by
varying the pH, but it produces sludge and requires further treatment. Adsorbents
and membrane filtration are the most used technologies for removal of heavy
metals from waste water. Activated carbon is frequently used as an adsorbent, but it
remains an expensive material. The research and production of low-cost adsorbents
have gathered an attention in present life which will lead to safer and economical
method for the elimination of heavy metals from water. Membrane filtration is a
widely used method but it has a high operational cost due to membrane fouling.
Initial metal concentration, pH, environmental impact, capital investment and
operational cost should be considered before selecting the particular technique.
References:
S. Babel, T.A. Kurniawan. “Cr (VI) removal from synthetic wastewater using coconut
shell charcoal and commercial activated carbon modified with oxidizing agents
and/or chitosan.” Chemosphere, 54 (7) (2004): 951–967.
M.A. Barakat. “New trends in removing heavy metals from industrial wastewater.”
Arabian Journal of Chemistry, Volume 4, Issue 4, October (2011): 361-377
T.A. Kurniawan, G.Y.S. Chan, W.H. Lo, S. Babel. “Physio-chemical treatment
techniques for waste water laden with heavy metals.” Chem. Eng. J., 118 (2006):
83-98
T.Y. Lee, J.W. Park, J.H. Lee. “Waste green sands as a reactive media for the removal
of zinc from water.” Chemosphere, 56 (2004): 571-581
David A. Rockstraw, John F. Scamehorn. “Removal of heavy metals from water by
electrodialysis in the presence of acids and salts.” University of Oklahoma, Norman,
Oklahoma 73019
F.S. Zhang, H. Itoh. “Photocatalytic oxidation and removal of arsenite from water
using slag-iron oxide- TiO2 adsorbent.” Chemosphere, 65 (1) (2006): 125-131
J.O. Duruibe, M.O.C. Ogwuegbu, J.N. Egwurugwu. “Heavy metal pollution and human
biotoxic effects.” International Journal of Physical Sciences Vol. 2 (5) (2007): 112118
John G. Dean, Frank L. Bosqui, Kenneth H. Lanouette. “Removing heavy metals from
waste water.” Environ. Sci. Technol. 6 (6) (1972): 518-522
L.D. Benefield, J.M. Morgan. “Water Quality and Treatment.” R.D. Letterman (Ed.),
McGraw-Hill Inc., NY (1999):10.1–10.57
L.K. Wang, D.A. Vaccari, Y. Li, N.K. Shammas. “Physiochemical Treatment Processes.”
Humana Press, Vol. 3 (2004): 141-198
Chihpin Huang, Ying-Chien chung, Ming-Ren Liou. “Adsorption of Cu (II) and Ni (II) by
pelletized biopolymer.” Institute of Environmental Engineering, National Chiao Tung
University, (75) (1995)
J. Landaburu- Aguirre, V. Garcia, E. Pongracz, R.L. Keiski. “The removal of zinc from
synthetic wastewaters by micellar-enhanced ultrafiltration: statistical design of
experiments.” Desalination, 240 (2009): 262-269
A.M. Shahalam, A. Al-Harthy, A. Al-Zawhry. “Feed water pretreatment in RO systems
in the Middle East.” Desalination, 150 (2002): 235-245
Z.V.P. Murthy, L.B. Chaudhari. “Application of nanofiltration for the rejection of nickel
ions from aqueous solutions and estimation of membrane transport parameters.” J.
Hazard Mater, 160 (2008): 70-77
M. Sadrzadeha, T. Mohammadi, J. Ivakpour, N. Kasiri. “Neural network modelling of
Pb2+ removal from waste water using electrodialysis.” Chem. Eng. Process, 48
(2009): 1371-1381
