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solution
Nanotechnology
KING FAHD UNIVERSITY OF PETEROLEUMS AND MINERALS DHARAN
KSA
Special Topics in Chemical Engineering
Authored by: KAMAL SIDDIQUE
Presented by : Kamal Siddique
G201207340
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ABSTRACT
Iron oxide, titanium oxide, silver oxide and zinc oxide coated carbon nanotubes were used toremove Pb(II) from aqueous solution. Carbon nanotubes (CTNs) show exceptional adsorptioncapability and high adsorption efficiency for lead removal from water .Adsorption is a methodfor removing lead from wastewater. The adsorption of lead on new adsorbent different types ofcarbon nanotubes has been investigated using a series of batch adsorption experiments. To asignificant extent, pH influenced the extraction of lead from aqueous solutions. The leadremoval efficiency was checked by varying pH value and contact hours. The adsorption capacityof lead calculated at different dosage of lead and similarly by varying the runs per hour. Ourresults suggest that CNTs can be good Pb
2absorbers and have great potential applications in
environmental protection
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TABLE OF CONTENTS
Introduction .................................................................................................................................................................. 3
SAFETY MEASURES WHILE HANDLING LEAD AND NANO PARTICLES ............................................................................ 4
1. Inductively Coupled Plasma Mass Spectrometry or ICP-MS: .............................................................................. 5
2. Method ................................................................................................................................................................. 8
2.1 Experiment: ............................................................................................................................................... 10
3. Effect of different parameters ........................................................................................................................... 10
a. Effect of contact time .................................................................................................................................... 10
b. Effect of CNT dose .......................................................................................................................................... 11
c. Effect of solution pH ...................................................................................................................................... 11
d. Effect of agitation .......................................................................................................................................... 12
4. Optimum conditions for removal of lead .......................................................................................................... 12
5. Comparative analysis of various cnts ............................................................................................................... 12
6. Conclusions ......................................................................................................................................................... 15
Acknowledgment......................................................................................................................................................... 16
References ................................................................................................................................................................... 17
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INTRODUCTION
The effects of heavy metals such as lead, mercury, copper, zinc and cadmium on human health
have been studied extensively. Excessive ingestion of them can causes accumulative poisoning,
cancer, nervous system damage. Lead is ubiquitous in the environment and is hazardous at highlevels. It is a general metabolic poison and enzyme inhibitor and can accumulate in bones,
brain, kidney and muscles. Long-term drinking water containing high level of lead can cause
serious disorders, such as anemia, kidney disease and mental retardation.
Lead in wastewater comes mainly from battery manufacturing, printing, painting, dying and
other industries. Unlike organic compounds, lead is non-biodegradable and, therefore, must be
removed from water. Various methods of lead removal from wastewater have been developed
and ad-sorption with activated carbon is a common used method. Increasingly stringent
standard on the quality of drinking water has stimulated a growing effort on the exploiter of
new high efficient ad-sorbents.Out of the wastewater treatment methods involving lead, precipitation, coagulation
sedimentation, reverse osmosis, ion exchange, cementation, and adsorption onto activated
carbon, adsorption is considered quite attractive in terms of its efficiency of removal from
dilute solutions, economics, and handling . Various adsorbents such as activated carbon, iron
oxides, filamentous fungal biomass and natural condensed tannin have
been explored . EPA drinking water standards for lead are 0.05 mg/l, but a level of 0.02 mg/l
has been proposed and is under review. Increasingly stringent standard on the quality of
drinking water has stimulated a growing effort on the exploiter of new high efficient
adsorbents. So the necessity to exploit new high efficient adsorbents is great.
Carbon nanotubes (CNTs), a novel kind of carbon, were first reported by Iijima in 1991. CNTs
can be thought of as cylindrical hollow micro-crystals of graphite. Because of relatively largespecific area, CNTs have attracted researchers interest as a new type of adsorbent and offer an
attractive option for the removal of metals, fluoride, organic pollutants. CNTs can also be used
as supports for adsorption materials. Zinc, silver. Titanium and iron oxide-coated CNTs for
metal removal have been proved successful for the enhancement of treatment capacity
Carbon nanotubes (CNTs), a new form of carbon, are attracting researchers great interest due
to their exceptional absorption properties, mechanical properties and unique electrical
property.
Although carbon nanotubes exhibit great potential for the adsorption of heavy metal ions from
aqueous solutions, the removal efficiency, selectivity, and sensitivity remain limited. The
modification of carbon nanotubes is therefore considered to be an important route for theenhancement of removal efficiency, selectivity, and sensitivity of heavy metals. The surfaces of
multi-walled carbon nanotubes (MWCNTs) can be modified in a variety of ways, such as
chemical bond formation between the modifying species and MWCNTs surfaces or physical
adsorption of the modifier to MWC-NTs surface. Many studies have focused on the removal of
heavy metal ions by modified carbon nanotubes, including cadmium , nickel and strontium ,
lead chromium , uranium , copper , and copper, zinc, cadmium, and nickel ions from aqueous
solution
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SAFETYMEASURESWHILEHANDLINGLEADAND NANOPARTICLES
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1. INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY OR ICP-MS:Inductively Coupled Plasma Mass Spectrometry or ICP-MS is an analytical technique used for
elemental determinations. The technique was commercially introduced in 1983 and has gained
general acceptance in many types of laboratories. Geochemical analysis labs were early
adopters of ICP-MS technology because of its superior detection capabilities, particularly for therare-earth elements (REEs). ICP-MS has many advantages over other elemental analysis
techniques such as atomic absorption and optical emission spectrometry, including ICP Atomic
Emission Spectroscopy (ICP-AES), including:
Detection limits for most elements equal to or better than those obtained by GraphiteFurnace Atomic Absorption Spectroscopy (GFAAS)
Higher throughput than GFAAS The ability to handle both simple and complex matrices with a minimum of matrix
interferences due to the high-temperature of the ICP source
Superior detection capability to ICP-AES with the same sample throughput The ability to obtain isotopic information.
An ICP-MS combines a high-temperature ICP (Inductively Coupled Plasma) source with a mass
spectrometer. The ICP source converts the atoms of the elements in the sample to ions. These
ions are then separated and detected by the mass spectrometer.
Figure 1 shows a schematic representation of an ICP source in an ICP-MS. Argon gas flows inside
the concentric channels of the ICP torch. The RF load coil is connected to a radio-frequency (RF)
generator. As power is supplied to the load coil from the generator, oscillating electric and
magnetic fields are established at the end of the torch. When a spark is applied to the argon
flowing through the ICP torch, electrons are stripped off of the argon atoms, forming argon
ions. These ions are caught in the oscillating fields and collide with other argon atoms, forming
an argon discharge or plasma.
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Figure.1
The sample is typically introduced into the ICP plasma as an aerosol, either by aspirating a liquid
or dissolved solid sample into a nebulizer or using a laser to directly convert solid samples into
an aerosol. Once the sample aerosol is introduced into the ICP torch, it is completely desolvated
and the elements in the aerosol are converted first into gaseous atoms and then ionized
towards the end of the plasma.
The most important things to remember about the argon ICP plasma are:
The argon discharge, with a temperature of around 6000-10000K, is an excellent ionsource.
The ions formed by the ICP discharge are typically positive ions, M+
or M+
, therefore,elements that prefer to form negative ions, such as Cl, I, F, etc., are very difficult to
determine via ICP-MS.
The detection capabilities of the technique can vary with the sample introductiontechnique used, as different techniques will allow differing amounts of sample to reach
the ICP plasma.
Detection capabilities will vary with the sample matrix, which may affect the degree ofionization that will occur in the plasma or allow the formation of species that may
interfere with the analyte determination.
Once the elements in the sample are converted into ions, they are then brought into the mass
spectrometer via the interface cones. The interface region in the ICP-MS transmits the ions
traveling in the argon sample stream at atmospheric pressure (1-2 torr) into the low pressure
region of the mass spectrometer (
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Figure 2. The interface region of an ICP-MS.
The sampler and skimmer cones are metal disks with a small hole (1mm) in the center. The
purpose of these cones is to sample the center portion of the ion beam coming from
the ICP torch. A shadow stop (see Figure 2) or similar device blocks the photons coming from
the ICP torch, which is also an intense light source. Due to the small diameters of the orifices inthe sampler and skimmer cones, ICP-MS has some limitations as to the amount of total
dissolved solids in the samples. Generally, it is recommended that samples have no more than
0.2% total dissolved solids (TDS) for best instrument performance and stability. If samples with
very high TDS levels are run, the orifices in the cones will eventually become blocked, causing
decreased sensitivity and detection capability and requiring the system to be shut down for
maintenance. This is why many sample types, including digested soil and rock samples must be
diluted before running on the ICP-MS.
The ions from the ICP source are then focused by the electrostatic lenses in the system.
Remember, the ions coming from the system are positively charged, so the electrostatic lens,which also has a positive charge, serves to collimate the ion beam and focus it into the entrance
aperture or slit of the mass spectrometer. Different types of ICP-MS systems have different
types of lens systems. The simplest employs a single lens, while more complex systems may
contain as many as 12 ion lenses. Each ion optic system is specifically designed to work with the
interface and mass spectrometer design of the instrument.
Once the ions enter the mass spectrometer, they are separated by their mass-to-charge ratio.
The most commonly used type of mass spectrometer is thequadrupole mass filter. In this type,
4 rods (approximately 1 cm in diameter and 15-20 cm long) are arranged as in Figure
fig.3. Schematic of quadrupole mass filter.
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In a quadrupole mass filter, alternating AC and DC voltages are applied to opposite pairs of the
rods. These voltages are then rapidly switched along with an RF-field. The result is that an
electrostatic filter is established that only allows ions of a single mass-to-charge ratio (m/e) pass
through the rods to the detector at a given instant in time. So, the quadrupole mass filter is
really a sequential filter, with the settings being change for each specific m/e at a time.
However, the voltages on the rods can be switched at a very rapid rate. The result is that the
quadrupole mass filter can separate up to 2400 amu (atomic mass units) per second! This speed
is why the quadrupole ICP-MS is often considered to have simultaneous multi-elemental
analysis properties.
Spectrum showing copper isotopes by ICP-MS.The ability to filter ions on their mass-to-charge
ratio allows ICP-MS to supply isotopic information, since different isotopes of the same element
have different masses.
Once the ions have been separated by their mass-to-charge ratio, they must then be detected
or counted by a suitable detector. The fundamental purpose of the detector is to translate the
number of ions striking the detector into an electrical signal that can be measured and relatedto the number of atoms of that element in the sample via the use of calibration standards.
Most detectors use a high negative voltage on the front surface of the detector to attract the
positively charged ions to the detector. Once the ion hits the active surface of the detector, a
number of electrons is released which then strike the next surface of the detector, amplifying
the signal. In the past several years, the channel electron multiplier (CEM), which was used on
earlier ICP-MS instruments, has been replaced with discrete dynode type detectors (see Figure
6). Discrete dynode detectors generally have wider linear dynamic ranges than CEMs, which is
important in ICP-MS as the concentrations analyzed may vary from sub-ppt to high ppm. The
discrete dynode type detector can also be run in two modes, pulse-counting and analog, which
further extends the instrument's linear range and can be used to protect the detector from
excessively high signals
2.METHODAll chemicals and reagents used for experiments were of analytical grades. Stock solutions of 1
ppm Pb(II) were prepared from Pb(NO3)2 in deionized water. The initial PH of the solution was
3.5. One molar buffer solution was prepared from sodium acetate to prepare the various
sample of PH ranging from 4 to 5. Four different types of Carbon Nano tubes were used as an
strong absorbent to remove the lead from the aqueous solution. These are iron oxide coated,
zinc oxide coated, silver oxide coated, titanium oxide coated.
The concentrations of Pb(II) were measured using an ICP-MS . The pH measurements weremade on a pH meter. The final Pb(II) concentrations remaining in solution were analyzed.
The equilibrium metal adsorption capacity was calculated for each sample of Pb(II) by using the
following expression:
q = C1- C2
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Where q is the percentage Oxides/CNTs adsorption capacity ppm , C1 the initial Pb(II)
concentration 1ppm,C2 the final Pb(II) concentration 1ppm.
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2.1EXPERIMENT:All glassware used in this work was rinsed with 10% nitric acid to remove all impurities that
might be present and to prevent further adsorption of heavy metals to the walls of the
glassware. 50 gm. of zinc, silver, iron and titanium coated multiwall carbon nanotubes beenprepared for the experiments. Stock solutions of 1 ppm Pb(II) were prepared from Pb(NO3)2 in
deionized water.
1ppm aqueous lead solutions of PH 4,5,6,7 were prepared to check the effect of these four
carbon nanotubes absorption ability. Each for types of CNTs of mass 25 mg. were dissolved in
4,5,6,7 PH of 25 ml lead aqueous solution. All these samples were stirred at 150 rpm for 3 hr.
but the contact time given to these samples was 24 hr. all these samples than filtered through
filter paper and the final concentration of lead in all these samples were measured in ICP-MS.
The final concentration of lead was compared with the initial 1ppm lead concentration in
aqueous solution and the absorbed percentage of lead is calculation and graphically presented
at the end.
To check the effect of runs per hour 6 PH of lead solution was prepared and these four cnts of
each 25 mg dissolved in 50 ml lead solution. The contact time was 3 hr. All these samples were
run at 50, 100 and 150 rpm. Filtration of these samples carried out. Final concentration of lead
is measured by ICP-MS and compared with the initial concentration and the percent absorbed
lead is calculated.
Similarly to check the effect of dosage of these cnts on adsorption of lead different dosage of
15, 25, 35 mg were dissolved in 50 ml of 1ppm aqueous lead solution. RPM were set to be at
150.And at the end different contact time was given ranging from 1 hr. to 3 hr. for each
different type of cnts (Fe, Ag, Ti Zn coated) and the final concentration was measured by ICP-
MS after filtering the cnts.
3.EFFECT OF DIFFERENT PARAMETERSa. EFFECT OF CONTACT TIME
The time needed for the interaction between the adsorbate and adsorbent is crucial ( i.e., the
faster the removal, the better the adsorbent). Hence, it is important to study the effect of
contact time on the removal of the target heavy metals with all four types of cnts (Fe, Ti, Ag, Zn)
shows the effect of contact time on the adsorption of Pb(II) on to cnts. In general, the %adsorption of metals ions increased significantly within the first 10 min. Pb(II) absorbed for the
silver coated ct increased linearly with time up to 3 hr in the experiment. The maximum
removal of lead by silver coated cnt observed to be 58%. The removal of Pb(II) by iron coated
cnt increased linearly with time and the maximum removal was 85.5%. Similarly for the other
two the adsorption increases with time.
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b. EFFECT OF CNT DOSEThe effect of the coated cnts dosage on the percentage of metal ions adsorbed from aqueous
solutions was studied using metal ion concentrations of lead 1ppm .The experimental results
revealed that the removal efficiencies of metal ions increased gradually with increasing
amounts of CNTs. Increasing the masses of CNTs from 15 mg to 25 mg increased the %
adsorption of Pb(II) from 89% to 98%. This increase in % adsorption might have been attributed
to the fact that increasing the adsorbent dose provided a greater surface area or more
adsorption sites for the metal ions. Additional increases in the amount of CNTs used from 25
mg to 35 mg did not significantly affect the removal percentage of metal ions.
c. EFFECT OF SOLUTION PHSolution pH is one of the main influences on the adsorption process, especially for heavy
metal ions, such as Cu(II), Pb(II), Cd(II) and Zn(II), as they exist in different species depending on
the pH. The effects of solution pH on the adsorption of Pb(II) by coated CNTs were studied in
the pH range of 4.07.0, and the results are presented in graph . In general, the removal of
metal ions by CNTs was highly dependent on the pH of the solution. For all metals, the %
adsorption increased gradually with increasing pH.
The minimum adsorption observed at low pH values might have been due to the fact that
the higher concentration and mobility of hydrogen ions (H+
) present at lower pH favored the
preferential adsorption of hydrogen ions than metal ions. In addition, at low pH values the
surfaces of the MWCNTs are predominantly covered by H+
, which prevents metal ions from
approaching the binding sites. This was also in agreement with the surface complex formation
(SCF) theory, which states that an increase in the pH decreases the competition for adsorption
sites between protons and metal species but up to specific range. Moreover, lower positive
surface charge leads to less Columbic repulsion of the metal ions.
Further increases in the solution pH were shown to exhibit different effects on the adsorption
process, especially approaching the basic region up to 6 PH the adsorption found to be
maximum. But going to basic region again decrease the adsorption due to OH ion surround the
surface of the the cnts and form strong attraction.
When the pH of the solution increased from 6.0 % absorption of lead ions decreased and
decreased with CNTs. This decrease in the % adsorption at pH values higher than 6.0 couldpotentially be due to precipitation in the form of Pb(OH) 2 . It is commonly agreed that the
absorption of metal ions increases with increasing pH because the metal ionic species become
less stable in solution. However, at higher pH values (i.e., pH 6.010.0), the adsorption capacity
decreased, which may have been due to the precipitation of lead. The exact and
experimentally observed removal of lead by all four types of coated cnts is graphically and
numerically attached here.
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d. EFFECT OF AGITATION
In the previous parameters the RPM were kept constant at 150. So see the effect of differentrpm the experiments were run at three different RPM from 50 to 150.the general trend
observed was, by increasing the rpm the absorption of lead increases due to increased
turbulence and mixing of the solution except for the silver. At 150 rpm the maximum
adsorption for zinc oxide coated carbon nanotube was observed and similarly for titanium was
97% and for iron was 93%.
4. OPTIMUM CONDITIONS FOR REMOVAL OF LEAD
The highest predictive percentage removal is 99% . The parameters that contribute to theseoptimal conditions are PH 6, dosage 25mg, rpm 150, contact time 2 hr. and using the solution
volume of 50 ml. the control of carbon surface chemistry through the exclusive introduction of
certain surface group is a natural goal for the lead removal using carbon structures. It is highly
challenging as most method gives a surface covered with a mixture of acidic and basic groups.
Therefore the deposition of metal particles is usually achieved through multistep and time-
consuming procedures.
5. COMPARATIVE ANALYSIS OF VARIOUS CNTSIn comparison with the adsorption kinetics of various adsorbents it was concluded that most
of the removal process occurred with in the first 10 min. it can be concluded that theadsorption capability of the adsorbent is highly dependent on many factors such as surface
functional group, the specific surface area and the solution components. Cnts coated with zinc
oxide and titanium oxide shows the maximum removal of lead while the silver shows the
minimum in comparison to these. Iron oxide cnt also show the good absorption capability.
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0
20
40
60
80
50 100 150
concabso
rbedppm
rpm
Silver coated cnt
80
85
90
95
50 100 150
concabso
rbedppm
rpm
Iron coated cnt
90
92
94
96
98
100
50 100 150
concab
sorbedppm
rpm
Titanium coated cnt
88
90
92
94
96
98
100
50 100 150
concabsorbedppm
rpm
Zinc coated cnt
0
20
40
60
80
100
120
4 5 6 7
concabsorbedppm
PH
silver coated cnt
0
20
40
60
80
100
120
4 5 6 7
concabsorbedppm
PH
Iron coated CNT
92
94
96
98
100
4 5 6 7
concabsorbedppm
PH
Titanium coated CNT
0
20
4060
80
100
120
4 5 6 7
concabsorbedppm
PH
Zinc coated CNT
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0
20
40
60
80
100
15 25 35
concabsorbedppm
dosage mg
Ag coated cnt
92
94
96
98
100
15 25 35
concabso
rbedppm
dosage mg
Ti coated cnt
96.5
97
97.5
98
98.5
15 25 35concabsorbe
dppm
dosage mg
Zn coated cnt
88
90
92
94
96
15 25 35concabsorbedppm
dosage mg
Fe coated cnt
0
10
2030
40
50
60
1 2 3
concabso
rbedppm
time hr
Ag coated cnt
78
80
82
84
86
1 2 3
concabsorbedppm
time hr
Fe coated cnt
80
85
90
95
100
105
1 2 3
concabsorb
edppm
time hr
Ti coated cnt
85
90
95
100
1 2 3
concabsorbe
dppm
time hr
Zn coated cnt
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6. CONCLUSIONSThe optimum PH is 6 which give the maximum result for the removal of lead from the aqueous
solution. The percentage uptake increased with an increase of the agitation speed in which 150
rpm give the maximum result. The percentage removal of lead was observed to be optimal for
the intermediate dosage of 25 mg. the effect of contact time experiment indicated the higherfraction of the lead migrates from the bulk solution through the adsorbent boundary layer onto
the active sites of the active sites of the adsorbent.
The results obtained from these analyses proved that this method of adsorption of lead using
CNTs are the promising for the further development of water and waste water treatment.
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ACKNOWLEDGMENT
I am very thankful to Dr. Mautaz Ali Atieh and KFUPM for giving me an opportunity to work in a
professional environment to perform the project on the laboratory scale. I learnt alot during
the supervision of Dr. in my analytical and technical skills to understand the nanotechology
work, principle and its industrial application
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REFERENCES
Nassereldeen, AK,Mautaz A A , Abdullah A.M, Mohamed E S migrhami, MD Z Alam ,Noorahayu
Yahhya, 2008, kinetic adsorption of carbon nanotubes for lead removal from aqueous solution.Journal of Environmental Science 21(2009)539-544.
Reed BE, Arunachalam S. Use of granular activated carbon columns for lead removal. J Environ
EngASCE 1994;120:41636
Li YH, Wang SG, Wei JQ, Zhang XF, Xu CL, Luan ZK, Wu DH, Wei BQ. Lead adsorption on carbon
nanotubes. Chem Phys Lett 2002;357:2636
Shu-Guang Wang
, Wen-Xin Gong, Xian-Wei Liu,Ya-Wei Yao, Bao-Yu Gao,Qin-Yan Yue. Removal of lead(II) from aqueous solution by adsorption onto
manganese oxide-coated carbon nanotubes, School of Environmental Science and
Engineering,, 58 (2007) 1723
Y.H. Li, Z.C. Di, J. Ding, D.H. Wu, Z.K. Luan, Y.Q. Zhu, Adsorption ther-modynamic, kinetic anddesorption studies of Pb
2+on carbon nanotubes, Water Res. 39 (2005) 605609.
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