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October – December 2011 RJPBCS Volume 2 Issue 4 Page No. 585
Research Journal of Pharmaceutical, Biological and Chemical
Sciences
Monitoring and Assessment of Fluoride Contamination in Industrial
Environment [South India] and Removal of Fluoride
Sundar S 1*, Alagumuthu G2, Annadurai G1, Nandagopal S.1
1Sri Paramakal yani Centre for Excellence in Environmental Sciences, Manonmania m Sundara nar University,
Alwarkurichi - 627412, Tamil Nadu, India
2 Department of Chemistry, Sri Paramakal yani College, Alwarkurichi - 627412,Tamil Nadu, India
ABSTRACT
In the present work detailed studies were carried out to understand the effect of adsorbent dose [Ball
clay], temperature on kinetics, and competing anion concentrations. Characteriza tion s tudies on the a dsorbent by
XRD, SE M a nd FT-IR analysis before and after fl uoride ads orption were carried out to unders tand the adsorption
mechani sm. XRD and FT-IR s tudies revealed signi ficant changes after fluoride adsorpti on and showed formation of
new co mpl exes on a dsorbent surface. Appl icability of di fferent s orpti on kinetic models was studi ed. The surface
sites are heterogeneous in na ture and followed heterogeneous site bindi ng model. The presence of phosphate,
sulphate and arsenate showed adverse effect on fluoride remova l efficiency of ball clay adsorbent. The effi ci ency
of material towards ground water samples treatment was tested with and wi thout adjus ting pH, a nd the results
are discussed.
Key words: Adsorpti on; Effec ts of Fl uoride; Fluoride contamination; Fluoride removal; Kinetics; South India.
*Corresponding author
Email: sundarstreco@gmail.com
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INTRODUCTION
Water is one of the abundant available substances in nature. Although earth is a blue
planet and 4/5th of its surface is covered by water, the hard fact of life is that about 97% of it is
locked in the oceans which is too saline so it cat be used for drinking and agricultural purposes.
Of what is left, about 80% is trapped in polar ice caps and giant glaciers. Another 10% of it is
locked in rock crevices lying deep as 800 m below the earth’s surface which is very expensive to
pump out. This leaves only about 0.3% of the worl d’s water resources that man can tap for
domestic, agricultural and industrial use [1, 2]. Water is an essential ingredient of all animals,
plants and human beings. So it is also called ELIXIR. The water requireme nt of a community may
be grouped under the following categories. Domestic purpose, commercial and industrial
purpose, civil and public purpose, and loss and waste. The quantity of water required for
domestic purpose viz., drinking, cooking, bathing, washing, sanitary purposes, private
gardening, domestic animals etc. This demand depends upon the living conditions of the
community. Also, essential for commercial and industrial purpose includes manufacturing
plants, hotels, dairies, offices, business centres, stores, refineries, breweries etc [3, 4]. The
requi rement depends upon the character of the town or city, used for civic or public purpose
includes sprinkling street, fountains, ornamental displays, swimming pools, lawns etc. los s and
waste includes the careless use of water, leakage in mains, valves, other fitti ngs etc. The
requi rement of water is also essential for the growth of crops. Water is very important in
aquaculture systems. Water plays an important role in the manufacture of electric power.
Thus water can be considered as the most important raw material of civilization because
of the fact that without water, human being cannot live and industry cannot thrive. With ever
growing population and industrial developme nts, the demand for water is also increasing day
by day and hence every country has to take necessary action to make use of the available water
resources. The water resources are certainly inexhaustible gift of nature. But to ensure their
services for all the time to come, it becomes necessary to maintain, conserve and use the water
resources very carefully. It is an established fact that prope r maintenance, conservation and
wise use of water resources will definitely avoid the chance of water famine for future
generation for an indefinite period. Natural waters may be broadly divided into the following
categories. Surface waters: Flowing waters e.g. streams and rivers; Still waters e.g. ponds, lakes,
and reservoirs; underground water supplies: Water form shallows and deep springs and wells;
Water form lower measures of coal mines: Rain water; Estuarine and sea water. Fluoride is an
essential micronutrient for human health [5]. However, excessive body intake of fluoride leads
to dental fluorosis and crippling skeletal. High groundwater fluoride concentrations associated
with igneous and metamorphic rocks which have been reported from India, Pakistan, West
Africa, Thailand, China, Sri Lanka, and Southern Africa. The maximum permissible level of
fluoride in drinking water as regulated by the World Health Organization is 1.5 mg/L. Excellent
technologies are available for defluoridation. These technologies are not always applicable in
rural area due to cost and technology requirements [6]. The adsorbents derived from natural
minerals and by-product from industrial activities such as clay minerals and bleaching powder
has been developed for defluoridation. Many researchers used adsorbents in a powder form
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for adsorption study. Excess intake of fluoride is responsible for dental caries, bone fluorosis,
and lesions of the thyroid, endocrine glands, and brain. Fluoride is a naturally occurring element
in minerals, geochemical deposits, and natural water systems and enters food chains through
either drinking water or eating plants and cereals. High fluoride levels in groundwater are a
worl dwide problem, including various regions in Africa and Asia, as well as China. Many parts in
India have been reported fluoride concentrations in water above the permissible limits. The
material properties before and after fluoride adsorption were studied by following XRD, FT-IR
and SEM techniques. Effects of experimental paramete rs like different particle size of ball clay
and temperature on fluoride removal were studied to understand its applicability in treating
water samples.
MATERIALS AND METHODS
History of collection of adsorbent:
The adsorbent is collected at Neyveli Thermal Power Station, Neyveli. Lignite and coal is
used as raw material for producing power in the thermal power station. When the process is
completed the clay substance is obtained as effluent. Such clay substance is called as ball clay.
This substance is used as adsorbent material in our studies. The physico-chemical properties of
the three materials are studied. The clay substance has high amount of aluminium, magnesium
and calcium. Such metals are present in the form of silicates. In addition to this, some other
metal species are present in trace quantities. Analar grade chemicals are used in this study.
Batch adsorption method is carried out of the removal of fluoride from drinking water [7]. For
prepa ring artificial fluoride solution NaF sample [BDH 99% pure] is used. The required amount
of sodium fluoride is weighed accurately for preparing the concentration of fluoride as 100
ppm per litre. From this stock solution, the fluoride concentration of 3 ppm is prepared freshly.
Take 100 ml of 3 ppm solution is taken with 5mg of adsorbent into the numbered 250 ml iodine
flasks. The experiments are carried out at different time intervals, viz., 10, 20, 30, 40, 50, 60, 80
and 90 min.
The size of the adsorbent particles is separated by using molecular sieves. This is
available at Department of Rural Technology, Gandhigram Rural University, Gandhigram. 3 gm
of adsorbent is weighed accurately and taken in to the Iodine flasks. Now, all the iodine flasks
are put in the regulator attached mechanical shaker. The flasks are shaken vigorously. The
rotation of the flask is 150 rounds per min. After the completion of the experiment at different
time intervals, the flasks are taken out and filtrate of the content is collected in a 100 ml
beaker. The water quality parameters of this filtrate are noted. The detailed procedures are
given below.
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Determination of pH:
Preparation of buffer solution: a] pH: 4.0 and b] pH: 9.2
Buffer solution of pH 4.0 is prepare d by dissolving the buffer tablet 4.0 [s.d. Fine –
Chem. Ltd.,] is dissolved in a 100 ml beaker with minimum amount of double distilled water.
This solution is quantitatively transferred into a 100 ml SMF. The content is made upto the
mark by adding double distilled water. Buffer tablet 9.2 dissolved in a 100 ml beaker with
minimum amount of double distilled water. Then this solution is quantitatively transferred into
a 100 ml SMF. The content is made upto the mark by adding double distilled water.
The pH measureme nts of the water samples were carried out suing an analog pH meter,
systronics make. The pH meter was calibrated first with buffer solution of pH 4 and gain cross
checked with another buffer solution pH 9.
Electrical Conductivity
The conductance of fluoride treated sample is measured with the help of EQUIP –
TRONICS, digital conductive meter model No EQ-660. The measurements are made at room
temperature and the values are tabulated.
Determination of total alkalinity
10ml of the sample was taken in a conical flask. Added 2 to 3 drops pf Methyl orange
indicator and the contents of the conical flask were titrated against hydrochloric acid taken in
the burette. The end point of the titration was shown by a sharp colour change from yellow to
red. The total Alkalinity values for all the samples were calculated using the following formula.
TA as Calcium carbonate [mg / L] = B x Normality of HCl x 1000 x 50
ml of sample
Where, B = ml of total HCl used with methyl orange.
Determination of total hardness – EDTA method
10ml of the water sample was taken in a conical flask. 2 to 3 drops of buffer solution
were added to this sample. The contents in the conical flask were titrated against EDTA
solution taken in the burette using EBT as indicator. The end point of the titration is shown by a
sharp colour change from red to blue. Total hardness of the samples was determined using the
following formula.
Hardness [mg/L] = ml of EDTA x 1000
10
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Determination of Fluoride by Electrode method
The amount of fluoride present in the solution was measured using expandable ion
analyzer EA 940, the fluoride ion sensitive electrode 9409 and the reference electrode [all
Orion, USA make]. The fluori de electrode is a selective ion sensor. The key element in the
fluoride electrode is the laser type doped lanthanum fluoride crystal across which a potential is
established by fluoride solutions of different concentrations. The crystal is in contact with the
sample solution at one face and an internal reference solution at the other.
Reference Electrode
The fluoride electrode can be used with a standard calomel reference electrode and almost any
modern pH meters having and expanded millivolt scale. The fluoride electrode measures the ion
activity of fluoride in solution rather than the concentration. Fluoride ion activity depends on the total
ionic strength of the solutions pH and on fluoride complexity species.
Interference
Fluori de forms complexes with several polyvalent cations, notably aluminium and iron.
The extent to which the complexation takes place depends on the solution pH and relative
levels of fluoride and complexion species. In acidic medium [pH<=5.5] fluoride ion forms a
poorly ionized HF. The LaF3 based electrode is unresponsive to HF. In alkaline medium [pH>5.5]
hydroxyl ion also can interfere with electrode response to fluoride ion, whenever the hydroxyl
ion concentration is greater than one tenth of the concentration of fluoride ion.
Remedy
Adding an appropriate amount of buffer solution to the sample. Provide a uniform ionic
strength background. Maintain the pH between 5 and 5.5. 1, 2 - cyclohexylene dinitrilo tetra
acetic acid [CDTA], one of the components of the buffer preferentially complexes with the
interfering cations and releases free fluoride ions.
Detection Limits
Upper detection limit: 100 mg/L; Lower detection limit: 0.002 mg/L
Prepara tion of standard Sodium fluoride solution:
A stock solution of sodium fluoride containing 100 mg F-/L was prepare d using analog
sodium fluoride and fluoride free double distilled water. The procedure is given below.
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Total ionic strength Adjustment Buffer – [TISAB-III]:
About 500 ml of fluoride free double distilled water was taken in a one litre beaker. To
this 211 ml of concentrated hydrochloric acid was added, followed by 383 ml. of ammonium
acetate and 19.8 g of 1, 2-cyclohexylene dinitrilo te tra acetic acid [CDTA]. A calibrated pH
electrode was immersed into the solution and the pH was adjusted between 5 and 5.5 by adding
the required amount of sodium hydroxide solution. The beaker was kept in a water bath for
cooling. The contents of the beaker were transferred into a one litre standa rd measuring flask
and the solution was made up to the mark using fluoride free double distilled water.
Measurement of fluoride
Direct measurement is an easy procedure for analyzing large number samples. The
method involves the calibration of the meter with two standards of known concentrations
selected in such a way that the unknown has a concentration in between these two standards
can be ten times. Concentrations of unknown samples were read directly from the meter.
First two solutions of sodium fluoride with fluoride concentration of 0.5 mg/L and 5 mg/L
respectively were used for calibrating the instrument. 25 ml of the standard sodium fluoride
sample with concentration of 0.5 mg/L was mixed with 2.5 ml of TISAB -III buffer solution. The
electrodes were then i mmersed in this solution. After calibra ting the meter with this standard
fluoride solution and again the calibration was done.
Take 25 ml of water sample and 2.5 ml of buffe r solutions were mixed and the mixture
was stirred for about five minutes. After stirring the electrodes were immersed in the solution.
The fluoride ion concentration of the sample was read directly from the meter.
Evaluation of Defluoridation Capacity
Defluoridation ex periments were carried out by the Batch equilibration method. 3 gm. of
the adsorbe nt material was added to 100 ml. of water sample at a fluoride concentration of 3.00
mg. F/L. The contents were shaken thoroughly using a shaker rotating at a speed of 120 rpm.
The solution was then filtered through Whatmann 42 filter paper and the filtrate was analyzed
for fluoride. The deflouridation capacity of the adsorbent was calculated as follows.
Defluoridation capacity = mg of fluoride removed x 1000
Amount of the adsorbent taken in grams [mg F/kg]
RESULTS AND DISCUSSION
The samples are collected in the villages of Vellarkulam, Thallarkulam and Elanthaikulam
of Mukkudal block, Tirunelveli district. The examinations are carried out on water samples, cow
milk children’s urine and adult’s urine. The water samples are obtained from tube wells and
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wells of the above villages. The physico-chemicals characters of the water samples are analyzed
and given in table 1. The pH of the water samples is almost neutral. The other parameters viz.,
EC, TH and TA are in the permissible limit. The value of fluoride is somewhat above the
tolerance level. In the Elanthaikulam village, the concentration of fluoride of the tube well is
1.982 ppm. Comparison with W.H.O. the value is greater than the permissible limit [1 ppm]. In
the Vellarkulam village, the value is 1.32 / ppm. From this analysis, the above two villages are
fluoride endemic areas of the block, where the pupils are affected by fluoride toxicity [1, 2].
Thallarkulam village has lesser fluoride concentration value, ie. 0.923 ppm. This is less than the
permissible limit. So, the toxicity due to fluoride in the drinking water is very minimum level.
Similarly, the level of fluoride in cow milk, urine of children and urine of adult were also
determined. Among the three villages, Elanthaikulam village has a greater amount of fluoride
concentration in cow’s milk and urine of 0.157 and 3.31 ppm respectively. This data reveals
that, the above village is the highest fluoride endemic area of the block. The other villages have
minimum values of fluoride ion concentration. The data are given in table 2.
Table .1. Physico-Chemical Parameters
Name of Village
Source
pH
Electrical
conductivity
(mho)
Total Alkalinity
Total Hardness
Chloride
Fluoride (ppm)
TDS (ppm)
Vellarkulam
Well
7.3
2.500
700
30
4260
-
120
Hand
Pump
7.4
6.11
550
780
4970
1.34
280
River
Water
7.8
0.205
250
80
5325
-
10
Thallarkulam
Well
7.2
1.248
1450
250
4260
-
60
Hand
Pump
7.3
0.144
750
150
2485
0.93
100
River
Water
7.4
0.176
450
120
7455
-
10
Elanthaikulam
Well
6.9
2.710
1250
120
4260
-
130
Hand
Pump
7.5
2.460
600
860
5680
194
120
River
Water
7.5
0.200
150
130
5325
-
10
Table.2.Fluoride analysis
S.No.
Village
Fluoride concentration ppm
Cow mil k
Urine (Child)
Urine (adult)
1
Elanthaikulam
0.157
1.22
3.31
2
Vellarkulam
0.143
0.157
0.931
3
Thallarkulam
0.098
0.006
0.825
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From the two water bodies, the well water has maximum a mount of fluoride. The
people, who drink well water, are affected by the fluoride toxicity and leads to the disease are
known as “fluorosis”. The main types of dental fluorosis and skeletal fluorosis are occurred is
that areas. This is confirme d by the furthe r analysis of the dental and skeletal of the people. The
status of the dental fluorosis of the above three villages are givens in table 3. The surveys are
made on nearly 110 residents. In Elanthaikulam village, the moderate level of dental fluorosis is
only 55. The parentage of dental fluorosis is 50. The severe attack of dental fluorosis is 27.27%
and acute level of fluorosis is 22.72%. This is evidenced by the presence of high level of fluoride
ion concentration in drinking water of the village. The level of fluoride in the cow’s milk, urine
of children and adults is highly pronounced. Due to prolong ingestion of fluoride, 22.72% of
peoples are affected acute dental fluorosis. Thallarkulam is another fluoride endemic area
where the children, men and wome n were also affected by fluoride pollutant in drinking water.
The percentage of dental fluorosis for moderate, severe and acute cases is 41.17, 31.76 and
27.05 respectively. The values are less than the Elanthaikulam village due to less value of
fluoride concentration in drinking water.
Table.3. Dental Fluorosis status among the Fluoride affected people in different village
S.No.
Name of th e
Village
Status of dental Fl uorosis
1+
moderate
%
2 +
Severe
%
3 + acute
%
1
Elanthaikulam
55
50
30
37.27
25
32.72
2
Thallarkulam
35
41.17
27
31.76
23
27.05
3
Vellarkulam
23
38.33
18
27.0
19
21.66
In addition to drinking water, the fluoride levels in cow’s milk and urine samples are also
noticed. The values are highly supported to the nature of the toxicity in the above villages.
Drinking water is an essential commodity for human and animals. So we concentrated on the
study of fluoride in drinking water and its residual substances like milk and urine. The obtained
information are c omplied and analyzed and further evidenced wi th the help of photo for
children, adult and aged people. The photos for moderate, severe and acute cases for dental
fluorosis and skeletal fluorosis for aged peoples are also shown in this report. We found that
the Elanthaikulam village is the highest endemic area for fluorosis compared to the other
villages. We also made an analysis of distribution of fluorosis in the different age groups of
peoples who are living in Elanthaikulam village. The total numbers of affected person is 110, the
age group from 5 to 90. The data are given in table 4. The fluoride toxicity is mainly affected is
women society than the men. In the case of children the ratio of boys and girls is 1:5 for the age
group between 5 to 10 years. For adults, the ratio is 1: 4. For the age group betweens 40 to 50,
the ratio is 1:6. Above the age group 55, we identified that both dental and skeletal fluorosis of
men and women, while women are higher numbers then men. In the third village Thallarkulam,
where the value of fluoride level is less than the tolerance limit where the toxicity leads to
dental and skeletal fluorosis are very minimum. This indicates that, the dinking water contains
only lesser amount of fluoride, is good for drinking. The defluoridation efficiency of ball clay
was studied under different expe rimental conditions like contact time of the adsorbent for
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maximum defluoridation, particle size of the adsorbent, dose of the adsorbent, effect of pH and
effect of temperature. A similar type of study has been reported on to fire clay
Table 4: Distribution of fluorosis in the different age group of
population living in Elanth aikulam (Tota l No. of affected person 110)
Age
Affected m en
Affected Wo men
5-10
2
10
10-15
1
5
15-20
-
2
20-25
3
2
25-30
-
-
30-35
-
1
35-40
4
3
40-45
5
-
45-50
2
12
50-55
8
11
55-60
3
-
60-65
5
5
65-70
2
3
70-75
-
-
75-80
3
5
80-85
6
10
85-90
-
-
Adsorption Kinetics
Effect of temperature
The sorptive behaviour noticed the three temperatures for systems is shown in figure 1.
The sorption rate inc reased at higher temperatures as the intra particle diffusion is the
governing factor of the adsorption process [12-14]. At higher temperatures mobility of fluoride
ions increased so the complex formation also increased. A similar behaviour has been observed
by other workers also for the adsorption of Hg [II] on to different adsorbents [15-16].
0
100
200
300
400
500
600
700
800
900
020 40 60 80 100
Time (hrs)
Defluoridation Capacity (mg F/Kg)
30 C 40 C 50 C
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Effect of particle size
The defluoridation studies were carried out with three particle sizes viz., 75, 150 and
300 µ as shown in Fig.2. The results indicated that there was a significant increase in
defluoridation capacity with a decrease in particle size of ball clay [18-19]. This is obvious,
because any adsorption process depends upon the number of active surface sites. The particle
size 75 µ has maximum defluoridation capacity [767 mg/Kg] and hence it was used in all
laboratory experiments. This is due to a given mass of ball clay; smaller particle size woul d
increase surface area availability hence the number of sites increased.
0
100
200
300
400
500
600
700
800
900
020 40 60 80 100
Time (hrs)
Defluoridation Capacity (mg F/Kg)
75 Micron 150 Micron 300 Micron
The re moval of fluoride by Ball clay at three temperatures was also determined using
the following first order expression by Lagergren.
log [qe – q] = log qe – [Kad / 2.303] x t [1]
The Lagergren plots of the reactions at the three Ball clay and temperatures are given in
Fig. 3 and 4. The values of Kad at three temperatures were calculated from the slopes of the
respective linear plots and are given in table 5 and 6 along with the thermodyna mic parameters
as shown in Fig 3 and 4. The sorption of fluoride from aqueous solutions plays a significant role
in water pollution control. The naturally occurring ball clay has been identified as potential
defluoridating agents, functioning through ion exchange, adsorption and chemical processes [9
-11]. Detailed investigations under different conditions were carried out to determine the
defluoridation capacity of ball clay and to understand the mechanism of adsorption. The effect
of various factors like contact time, pa rticle size, and temperatures governing the
defluoridation capacity of ball clay has been experimentally studied in the laboratory by batch
equilibration method.
Instrumental Studies
For understanding the nature of fluoride sorption XRD and FTIR studies were perf ormed
using the raw and treated adsorbents. The XRD pattern of pure ball clay and fluoride loaded ball
clay are shown in Fig. 5a and 5b. The crystal dislocation takes place on fluoride adsorbed
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material. This is evidenced by the disappearance of 2θ value at 35o. This shows the strong
adsorption of fluoride on the surface of the adsorbent. FTIR analysis of the sorbent surface
before and after the sorption reaction has provided the information regarding the surface
groups that might have participated and also about the surface sites at which sorption might
have taken place [Fig 6a, 6b]. The shift of stretching frequency, corresponding to the presence
of – OH groups from 3600 to 1100 cm-1 is due to the exchange of - OH group in the aqueous
solution of the adsorbe nt with fluoride ion in the solution.
CONCLUSION
The survey and analysis were made on fluoride e ndemic areas and identified three
villages in the block. Among the villages, Elanthaikulam village had highly pronounced the
fluoride disease. This is due to high level of fluoride content in well water and tube-well waters.
These are the sources for drinking purpose. The dental fluorosis and skeletal fluorosis were
highly noticed in the above village. The data were analyzed and explained. The other two
villages had the diseases only in minimum level. From the analysis made on the above studies,
we concluded and suggested that, the people who are living in the Elathaikulam village should
drink only boiled water and also eat food stuffs containing enriched calcium. The order of
fluorosis in the three villages was Elanthaikulam Vellarkulam Thallarkulam. Defluoridation
experiments were carried out by batch equilibration method and ball clay was used as
adsorbent. The maximum contact time between adso rbate and adsorbent was fixed as 50 min.
The minimum particle size of 75 µ exhibits the maximum efficiency of fluoride removal. This is
due to the greater availability of surface area of the adsorbent. The mechanism of adsorption
process was explained in terms of pH of the medium. At lower pH ranges, the defluoridation
capacity is the maximum in the adsorbent. That is, chemisorption dominates an important role.
At higher ranger, the value decreases, where chemisorption along with physisorption takes
place. In both cases, the adsorption process follows monolayer coverage. This is evidenced by
the linear Lagergren plots. Hence, Ball clay has maximum efficiency of in terms of removal of
fluoride in aqueous solution. The experimental data we re further confirmed with XRD and FTIR
analysis.
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