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FUNDAMENTALS OF SPECIFICATION FOR SORBENT IN DEFLUORIDATION OF DRINKING WATER

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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 01, January 2019, pp. 978-983, Article ID: IJMET_10_01_100
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=1
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
Scopus Indexed
FUNDAMENTALS OF SPECIFICATION FOR
SORBENT IN DEFLUORIDATION OF
DRINKING WATER
J. Sunil Kumar, V. Radhika
Department of Chemistry, S R Engineering College, Warangal-506 371, India
N. Srinivas
Department of Chemistry, Kakatiya University, Warangal-506 001, India.
ABSTRACT
Fluoride is a typical component of natural waters and its concentration varies
depending on the water resource. Water may be contaminated by natural sources like
more alkaline ions (CO32-+HCO3->10.4 meq/l water) reacts with halite which comes
from industrial effluents. This is ensuing in fluoride concentrations up to 12.7 mg F–/l
where ground level of water is low. WHO standards and BIS: 105000, 1991 permit only
0.5-1.5 mg/dl as the upper permissible limit for fluoride in drinking water for the Indian
context. Fluoride in excess of the permissible limits in drinking water causes a number
of endemic conditions referred to collectively as “fluorosis”. This paper explores the
sorptive answer of a recently developed adsorbent, Activated alumina finely grinded
with coconut shell powder. The efficiency of the sorption of fluoride ion is affected by
pH, contact time, adsorbent dose, type and size of adsorbents. The adsorption
equilibrium is well correlated by Freundlich and Langmuir models
Keywords: Fluoride ion, adsorption, adsorbents, Langmuir and Freundlich Isotherm,
Activated alumina, Coconut shell powder.
Cite this Article: J. Sunil Kumar, V. Radhika and N. Srinivas, Fundamentals of
Specification for Sorbent in Defluoridation of Drinking Water International Journal of
Mechanical Engineering and Technology, 10(01), 2019, pp. 978-983.
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1. INTRODUCTION
Pure water is scarce and is not easily available to all. Deprived sections of the society drink
unhygienic water and catch illness periodically, often resulting in epidemics. In fluoride
prevalent areas, especially small communities with spread out habitation, defluoridation of
potable water supply is still a problem. Fluoride actually spiked with an impure industrial waste
product (fluosilicic acid), "scrubbed" from Florida phosphate fertilizer smokestacks and natural
reactions in ground water. Most fluoride associated with monovalent cations such as NaF and
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Fundamentals of Specification for Sorbent in Defluoridation of Drinking Water
KF is water soluble, while the one formed with divalent cations such as CaF2 and PbF2 is
generally insoluble. Fluoride is “more toxic than lead and less toxic than arsenic” and is an
accumulative toxin. WHO (World Health Organization) standards and BIS: 105000, 1991
permit only 0.5-1.5 mg/L [1]. It is the upper permissible limit for fluoride in drinking water for
the Indian context [2]. Fluoride in surplus of the permissible confines in drinking water causes
a number of endemic conditions referred to collectively as “fluorosis” (Skeletal fluorosis,
crippling fluorosis and non-skeletal fluorosis). An intake of more than 6 mg of fluorine per day
results in fluorosis [3,4]. A formula has been proposed to calculate “optimum” fluoride
concentration [5].
Defluoridation is the process of removal of fluoride ion in drinking water. The process may
be classified broadly into two categories, namely, i) Additive methods, and ii) Adsorptive
methods. The different methods so far tried for the removal of excess fluoride from water can
be broadly classified into four categories: A) Adsorption methods, B) Ion exchange methods,
C) Precipitation methods, and D) Miscellaneous methods. Some defluoridation techniques
developed to control fluoride content in water are reverse osmosis, adsorption using sunflower
plant dry powder, steam of phytomass, Holly Oke, neem bark powder, activated cotton jute
carbon, bagasse ash, burnt bone powder, phosphate-treated saw dust, bone char, etc. as
adsorbents [6,7], Nalgonda technique, ion exchange process. Each method has its limitations as
well as its merits.
Activated alumina is one of the most popular and cost effective materials used for
defluoridation of water [8, 9]. Latest importance in aluminum toxicity is due to its possible role
in multiple neurological diseases such as Parkinson’s disease, amylotrophic lateral sclerosis and
Alzheimer disease (AD). There are few reports on aluminum levels in treated waters after
defluoridation with activated alumina. In a municipal water supply, aluminum level was around
0.3 mg/l, when treated water was of potable quality with respect to pH and fluoride [10].
Activated alumina G-87 procured from IPCL was used in these filter units [11]. Defluoridation
of Activated alumina is further effected through adsorption of anions selectivity. Generally
Activated alumina more effectively adsorbs Fluoride but in presence of higher pH, more
Hardness conditions SO4-2, HCO3-1 ions competition from this, reduce the efficiency of Fluoride
adsorption up to 25% [12]. In Defluoridation of water by activated alumina, Aluminum is
associated with organic carbon as soluble form in treated water [13].
This communication presents the Increase of efficiency of Activated alumina and decrease
the drawbacks of this single bed filtration an investigation on the use of double bed with the
combination of coconut shell powder along with Activated alumina in the defluoridation of
water.
2. MATERIALS AND METHODS
All the reagents used were of AR grade. Fluoride stock solution was prepared by dissolving
221 mg anhydrous sodium fluoride in 1000 ml distilled water in volumetric flask. Fluoride
Standard solution was prepared by diluting 100 ml stock solution to 1000 ml distilled water in
volumetric flask. This 1 ml solution has 0.1 mg of fluoride.
2.1. Equipment
Fluoride ion was estimated by HI 98402 Fluoride Meter as per standard methods. PH meter, and
Remi shaking machine for agitating the samples for the required period at a pace of 200
strokes/minute were used. The surface area of adsorbent particle and density were measured by
using surface area analyzer and picnometer respectively.
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2.2. Material development
Fresh Activated alumina (Glaxo laboratories India Ltd., Mumbai, India) was used in thePresent
study. This Activated alumina was crushed with activated coconut shell charcoal (seave size
4/8, Delta Exports Tamil Nadu, India). A literature review of the use of coconut shell activated
carbon powder to treat polluted aqueous effluents containing dyes/organics or toxic metal ions
[14].
Successful application of the adsorption technique demands innovation of cheap, nontoxic,
highly efficient material. Mixture of Activated Alumina and Charcoal convene these
requirements. Knowledge of optimal conditions would herald a better design and modeling
process, besides the determination of defluoridation capacity of mixture of activated alumina
and coconut shell charcoal, the effect of the variables such parameters like pH, contact time,
amount and particle size of adsorbent and concentration of fluoride ions of the uptake on
adsorbent materials was investigated from kinetic viewpoint. Adsorption studies were
performed by batch technique to obtain the rate and equilibrium data. Experiments were carried
out by shaking 10 g/l of adsorbent dose with 50 ml of aqueous solution containing known
concentration of fluoride ions and by agitating the samples on Remi shaking machine at a speed
of 200 strokes/min. Samples containing fluoride ions were maintained at a desired pH by adding
0.5 N HNO3 or 0.1 M NaOH. All the experiments were conducted at room temperature (29 ±
0.5°C).
The effect of pH on fluoride removal was found by adjusting the pH of the test solution of
5.0 mg F litre-1 to initial pH value of 9.0±0.10, 8.0±0.10, 7.0±0.10, 6.0±0.10, 5.0±0.10,
4.0±0.10 and 3.0±0.10 using 0.1N HC1 or 0.1N NaOH; a fixed quantity (10 g litre-1) of Mixture
of Sorbent was added and mixed for the equilibrium sorption time, and analyzed for residual
fluoride content.
To study the effect of an increase in the dose of mixture of Sorbent on removal of fluoride,
experiments were conducted by adding varying doses of 2.5, 5.0, 10.0, 15.0 and 20.0 g litre -1
to a test solution containing initial fluoride concentration of 5 mg F litre-1. The samples were
then agitated up to equilibrium time and residual concentration was found. Preliminary study
on the effect of monovalent and divalent anions and cations encountered in water supplies like
chlorides, carbonates, sulphates, sodium, potassium, calcium and magnesium on removal of
fluoride was found by spiking test fluoride solution with different concentrations of monovalent
and divalent anions and cations and investigated for percent removal of fluorides.
To assess the usefulness and practical aspects of fluoride removal by mixture of Activated
Alumina and Coconut shell charcoal Sorbent, down flow column studies were conducted using
10 mm I.D. glass column. Ordinary tap water spiked with a fluoride concentration of 5.0 mg F
litre-1 was used as test solution. The column was first filled with glass wool and overlain with
fine sand to a depth of 2.5 cm. A filter paper was placed over the sand layer and then filled with
Mixture of Activated alumina and Coconut shell charcoal powder sorbent to a depth of 2.5 cm
(weight of 2.7 g). Maintaining constant flow rate, samples were collected at different time
intervals and analyzed for residual fluoride content.
To find the feasibility of domestic application of Mixture of Activated Alumina and
Coconut shell charcoal Sorbent, studies were conducted employing ceramic candle type
domestic water filters. Inside of the candles were filled with mixture of Activated Alumina and
Coconut shell charcoal Sorbent and plugged with cotton (Figure 1). Test fluoride solution of
tap water containing varying fluoride concentrations (2-20 mg F/L) were passed through the
water filter. Samples were collected at regular time intervals and analyzed for residual fluoride
content.
3. RESULTS AND DISCUSSION
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Fundamentals of Specification for Sorbent in Defluoridation of Drinking Water
Details of studies conducted with mixture of Activated Alumina and Coconut shell charcoal
powder sorbent are presented and discussed below.
3.1. Effect of Contact Time
Figure 2 shows the progression of sorption reaction, the percent removal of fluorides by mixture
of Activated Alumina and Coconut shell charcoal powder sorbent after different contact times.
As the contact time increases, % removal increases rather rapidly, but then gradually
approaches a more or less constant value denoting attainment of equilibrium. The sorption
reaction may be considered to be occurring in three distinct phases. First, the initial rapid phase
in which rate of removal is very rapid and this occurs within initial twenty minutes. This may
be due to direct sorption reaction in which fluoride ions adsorb rapidly onto the surface of
mixture of Activated Alumina and Coconut shell charcoal powder sorbent due to specific
chemical interaction (or affinity) and due to diffusive and other driving forces. In the second
phase, rate of sorptive uptake decreases due to lesser sorption as a result of migration of fluoride
ions from the film / boundary layer to interior pore / capillary surfaces.
3.2. Determination of optimum dosage of mixed bed Activated alumina and
Coconut shell charcoal powder sorbent
Optimum dosage of activated alumina was determined by conducting jar test experiment.
Experiments were conducted for different dosages of mixed sorbent with flash mixing of 20
seconds at 100 rpm and flocculation of 20 minutes at 20rpm and settling time of 20 minutes.
Settled water was filtered through perforations and then analyzed for residual fluoride by ion
selective electrode method. The results are observed that optimum dosage of mixed bed
required to reduce fluoride level to 0.8 mg/L is 4.88g/L.
3.3. Effect of pH
To study the effect of pH electrode by Bench top meter is test experiment was conducted with
initial fluoride concentration of 4.88mg/L. To the water samples 6N NaOH was added for
maintaining different pH and were placed in jar test apparatus and experiment was conducted.
The filtered water samples were analyzed for residual fluoride content. The effect of pH in
fluoride removal is observed that optimum pH range 6 is required to reduce fluoride level to
0.8 mg/L.
3.4. Assessment of influence of interfering ions
Various alkaline concentrations 100-800mg/l was prepared by diluting the standard stock
solution. To this fluoride was added by the addition of fluoride stock solution is observed that
optimum Alkalinity range 4 mg/L is reduce fluoride level to 0.8 mg/L.
CONCLUSIONS
Fluoride removals by mixed bed activated magnisium ion alumina with coconut shell charcoal
powder adsorbent are effective adsorbent for removal of fluoride from water and Fluoride
removal increased with contact time.
ACKNOWLEDGEMENTS
The authors are thankful to the Host Institution S R Engineering College, for providing all
necessary facilities for this work.
LITERATURE CITED
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J. Sunil Kumar, V. Radhika and N. Srinivas
[1]
World Health Organization. Fluorides and human health. WHO Monogragh series No. 59
Geneva, Switzerland, (1970)?
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S. Venkata Mohan, P. Nikhila and S. J. Reddy, “Deter-mination of Fluoride Content
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No. 1-2, 1990, pp. 51-61.
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I. Frankel, E. Juergens, Removal of fluoride from industrial waste water using
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V. Radhika, “Requisites of stipulation for sorbent in defluoridation of drinking water”
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applications International Journal of pure and applied mathematics, 120(6), 2018,
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Y. S. Ho, G. McKay, Pseudo-second order model for sorption processes, J. Process
Biochemistry, 34(5) (1999) 451-465.
FIGURE-1
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Figure.1 Details of House hold filter’s candle filled with Mixture of Activated Magnesium ion
Alumina and Coconut shell charcoal powder
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