Term Prorject Nano Report

7/30/2019 Term Prorject Nano Report

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Removal of lead from aqueous

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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Removal of lead from aqueous solution


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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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