Fluoride occurs naturally in most water supplies. Main sources of fluoride in groundwater- The weathering and leaching of fluorinated minerals. Industrial wastewater discharges . With increased human industrial activities, high fluoride-content water has become a widespread problem in the world. WHO has given a guideline limitation of less than 1.5 mg/L of fluoride in drinking water. Various industries such as glass and ceramic production, fertilizer and semiconductor manufacturing contribute to fluoride pollution to a large extent. The effluents of these industries may reach to thousands of mg per L, which is higher than natural water.Depending on the concentration and water temperature, the effect of fluoride in drinking water can be beneficial or harmful to mankind. The presence of small quantities of fluoride in ingested water is often considered to have a beneficial effect on human health and helps in the normal mineralization of bones and dental formation. On the contrary, excessive intake of fluoride leads to osteoporosis, Alzheimers syndrome, skeletal fluorosis, dental fluorosis, cancer, infertility, and thyroid disorder.

1. Nano-adsorbent for fluoride
removal from drinking water
PRESENTED BY
PRANJAL SAHEB (21WM60R04)
WATER ENGINEERING AND MANAGEMENT
SCHOOL OF WATER RESOURCE
INDIAN INSTITUTE OF TECHNOLOGY KHARAGPUR
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2. Introduction
• Fluoride occurs naturally in most water supplies.
• Main sources of fluoride in groundwater-
 The weathering and leaching of fluorinated minerals.
 Industrial wastewater discharges .
• With increased human industrial activities, high fluoride-content water
has become a widespread problem in the world.
• WHO has given a guideline limitation of less than 1.5 mg/L of fluoride in
drinking water.
• Various industries such as glass and ceramic production, fertilizer and
semiconductor manufacturing contribute to fluoride pollution to a large
extent. The effluents of these industries may reach to thousands of mg
per L, which is higher than natural water.
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3.  Depending on the concentration and water temperature, the effect of
fluoride in drinking water can be beneficial or harmful to mankind.
The presence of small quantities of fluoride in ingested water is often
considered to have a beneficial effect on human health and helps in
the normal mineralization of bones and dental formation.
 On the contrary, excessive intake of fluoride leads to osteoporosis,
Alzheimers syndrome, skeletal fluorosis, dental fluorosis, cancer,
infertility, and thyroid disorder.
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Image source : Google image

4. • The de-fluoridation techniques can be mainly classified into
three categories-
• Membrane process (verse osmosis, nano-filtration, dialysis and
electro-dialysis)
• Chemical process
Adsorption techniques.
• Amongst all, adsorption method is cheaper and simple to use
and rest of the method are highly costly, toxic products,
producing excess sludge, shortcomings, and complex method.
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5. Permissible limits of fluoride
concentration in drinking water
S.No Name of Organization Permissible Limit
1 Bureau of Indian Standard
(BIS)
0.6-1.2 mg/l
2 World Health Organization
(WHO)
1-1.5 mg/l
3 Indian Council Of Medical
Research (ICMR)
1mg/l
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6. Adsorption Theory
 Adsorption is the process by which ions, atoms or molecules adhere to the surface of a
solid material. It is often described as surface phenomenon where particles are attached
to the top layer of material.
Adsorption Isotherm
• An adsorption isotherm is a graph that represents the variation in the amount of
adsorbate(x) adsorbed on the surface of the adsorbent with the change in pressure at a
constant temperature.
• From graph, we observe that after attaining
saturation pressure (Ps),the variation in the amount
of adsorbent adhering to the adsorbate becomes
zero. This happens because the surface area available
for adsorption is limited and as all the sites are
occupied , a further increase in pressure does not
cause any difference.
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7. Freundlich Adsorption Isotherm
Freundlich Adsorption gives the variation in
the quantity of gas adsorbed by a unit mass of
solid adsorbent with the change in the
pressure of the system for a given
temperature.
x = kp^(1/n)
m
or log(x/m) = logk + 1/n logP
x= mass of gas adsorbed, m = mass of the
adsorbent
P= pressure, n= constant(depend on
nature of adsorbent and gas)
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8. Langmuir Adsorption Isotherms
The Langmuir adsorption isotherms predict linear adsorption at low
adsorption densities and a maximum surface coverage at higher solute
metal concentrations.
Ɵ=fraction of surface covered by adsorbed molecule.
K=equilibrium constant
p=equilibrium pressure
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9. Why Nano-adsorbent for fluoride removal
• High selectivity of adsorbents.
• Low cost in installation and maintenance, thus economic.
• Reusability – can be regenerated many times.
• High efficiency, high productivity of fluoride removal and can remove up to 90% of
fluoride.
• Adsorption units are simple in their operation and design.
• Compared with the traditional micron-sized materials used for separation processes,
nano-sized carriers possess a good performance due to the high surface-area-to-
volume ratio and the absence of internal diffusive resistance.
• Nanoparticles have extremely small size, high surface area and good mass transfer
efficiency, providing better kinetics for the adsorption of ions from aqueous solutions.
• Magnetic nanoparticles have a high potential because they can easily be separated in
magnetic field.
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10. Nano-adsorbent
Used
Author Advantage Result
Fe – Ti Oxide Chen et al.
New chemical bond formed between the
two metal elements through an oxygen
atom increased the amount of hydroxyl
groups on the adsorbent surface and
adsorption capacity of the adsorbents.
Langmuir adsorption
capacity of 47 mg/g of
adsorbent much higher
than pure Fe and Ti
Iron–silver
Oxide Azari et al.
Iron oxides have high affinities toward
inorganic pollutant, high selectivity in
sorption processes, low-cost and
environmental friendliness.
The results showed
maximum removal
occurred at pH 3.
Adsorption capacity
= 22.883 mg /g
Silica nano
adsorbent
modified by
rice husk
Pillai et al.
It is abundantly used in India and
waste of rice mill.
RH is cheap and also contain silica which
have high surface area that helps in de-
fluoridation.
Langmuir adsorption
capacity of 12 mg/g,
and decreased with
increasing the
temperature.
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11. Nano-adsorbent
Used
Author Advantage Result
Ce–Zn binary metal
oxide
Dhillon et al.
Fast fluoride removal, and good
mechanical strength, favourable
high-performance large scale real
water samples treatment.
Langmuir adsorption
capacity of 194 mg/g at
pH 7.0
Al(III)-Fe(III)-La(III)
trimetallic oxide Adak et al.
New chemical bond formed
through oxygen increases the
adsorption capacity of the
adsorbent.
Maximum fluoride could
be removed up to 99.8%
at pH-7.0
Mg-doped nano
ferrihydrite Mohapatra et al.
The reason for choosing Mg as a
dopant in ferrihydrite is its non
toxic nature and cost effectiveness.
Maximum adsorption
capacity of 64 mg/g and
the adsorption process is
spontaneous and
endothermic.
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12. CASE STUDY
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13. The printed channel device was compact and easy to handle. The number of channels
printed in a single device can be varied as per the application and requirement. With
the help of 3D printing, the flow rate of contaminated influent can be controlled as
per the design.
Sectional view of loaded nanoparticle in channel
3 D image
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Image source: Patel et al.(2019)

14. Conclusion
 The efficiency of fluoride removal
was examined in 3D printed
microchannel loaded with iron
oxide nanoparticles. The
experimental analysis shown that
the adsorption capacity of 2.5
mg/g was attained using the
proposed system at lower
fluoride concentration (3 mg/L).
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15.  Limitation of Nano-adsorbent
• Activated alumina need frequent regeneration due to low adsorption
capacity at neutral pH and easy dissolution of aluminium in treated water
leads to secondary pollution.
• The use of nanoparticles in water treatment, however, is limited by the
costly separation process.
• Some of adsorbent only work at extreme pH values such as activated
alumina.(pH < 3)
• After some regeneration, they get polluted / deactivated during the
process.
• Their separation from treatment media is difficult using simple methods.
• Poor mechanical strength.
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16. Conclusion-
 Nano-adsorbent - Already showing promishing results.
 It gives high adsorption capacity.
 Cost is of major consideration in developing countries like
India.
 Hence, adsorption process using low cost adsorbents that are
abundant and easily available have been investigated.
 Also, there is a need to explore and study more about the
nano-magnetic adsorbents.
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17.  References
 Ali, I., Alothman, Z.A., Sanagi, M.M., 2015. Green synthesis of iron nano-impregnated adsorbent for
fast removal of fluoride from water. J. Mol. Liq. 211, 457–465.
 Chen, L., He, B. Y., He, S., Wang, T. J., Su, C. L., & Jin, Y. (2012). Fe―Ti oxide nano-adsorbent
synthesized by co-precipitation for fluoride removal from drinking water and its adsorption
mechanism. Powder Technology, 227, 3-8.
 Dhillon, A., Soni, S. K., & Kumar, D. (2017). Enhanced fluoride removal performance by Ce–Zn
binary metal oxide: adsorption characteristics and mechanism. Journal of Fluorine Chemistry, 199,
67-76.
 Mohapatra, M., Hariprasad, D., Mohapatra, L., Anand, S., & Mishra, B. K. (2012). Mg-doped nano
ferrihydrite—A new adsorbent for fluoride removal from aqueous solutions. Applied surface
science, 258(10), 4228-4236.
 Patel, R. K., Chawla, A. K., Loulergue, P., Teychene, B., & Pandey, J. K. (2019). 3D printed
microchannel loaded with hematite nanoadsorbent for fluoride removal from water. Materials
Letters, 254, 190-193.
 Pillai, P., Dharaskar, S., Shah, M., & Sultania, R. (2020). Determination of fluoride removal using
silica nano adsorbent modified by rice husk from water. Groundwater for Sustainable
Development, 11, 100423.
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