ninth highly electronegative and reactive element in the periodic table. It mostly
occurs in water in combination with sodium fluoride and hydrogen fluoride
(Premathilaka and Liyanagedera 2019). Eighty-five million tons of accumulated F
in the earth’s crust is non-biodegradable which is toxic to humans, animals and
plants (Singh et al. 2014). F accumulated in plant causes leaf necrosis and inhibits
photosynthesis and critical to plant growth enzyme activity. More than 260 million
people suffer from fluorosis in 25 countries worldwide and 66 million in India
(Chakraborti et al. 2016).
Increasing F contamination in groundwater and soil through anthropogenic and
geogenic activities, groundwater contamination is becoming a global problem as it is
common and uncontrollable. F geographical belts occur and India is one of them,
extending from Turkey through Iran, Iraq, Afghanistan to Japan and China
(Saravanan et al. 2008). F-endemic states are Andhra Pradesh, Gujarat Tamil
Nadu, Haryana, Punjab and all 33 districts of Rajasthan which are completely and
partially affected by F contamination due to the presence of F-rich rocks which are
basalts, mica, granites, etc. (Singh et al. 2018). Black and McKay studied first time
dental fluorosis in human, the brown patch called mottled enamel. The WHO
guideline for F in drinking water is 1.5 mg/L; above that guideline is unsafe for
human health (WHO 2004).
Drinking water is a major way of fluoride intake in the human body. The health
issue of eliminating high concentration F from water is very important for the
environment and for the public (Mohapatra et al. 2004). There are several methods
for removal of fluoride from water, such as chemical precipitation, ion exchange and
electrochemistry (Mohapatra et al. 2009). None of the method is easy and costly to
use for water purification to solve the groundwater pollution problem. Membrane
separation is based on two principles which are adsorption and filtration. Membrane
filters water at a lower cost, less energy consumption and reduces environmental
impact. Membrane has high efficiency in separation with easy maintenance, compact
modular structure and low effluent from chemical sludge. Membrane distinguishes
the metal ion on the basis of size and shape of the ion. Membrane performance
depends upon several factors like material used, pore size, structure, shape (design)
and fabrication methods. Membrane manufacturing using a variety of processes,
such as phase inversion, interfacial, polymerization, stretching, electrospinning,
pyrolysis, layer by layer deposition, slip casting and sol-gel. Different types of
membrane (organic, inorganic, hybrid) used in membrane technology as needed.
Different membrane technology are used in defluoridation of water on the basis of
pore size, types is reverse osmosis (RO), nanofiltration (NF), microfiltration (MF),
ultrafiltration (UF) and dialysis and electro dialysis processes. RO removes the
solutes from the stream through semipermeable membrane. Semipermeable
membranes serve as salt ion barriers. In Reverse osmosis process pressure exerted
to transfer molecules from one side to other side of semipermeable membrane.
Membrane commonly used in the RO system is made of polyamide and cellulose
acetate. But these membranes are not having a good outcome. Recently these
material composites are used with advanced modification like polyamide ultra-thin
membrane. RO membrane pores (0.0001–0.001μm) are small as opposed to MF and
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Vijaylaxmi and S. Khan
occurs in water in combination with sodium fluoride and hydrogen fluoride
(Premathilaka and Liyanagedera 2019). Eighty-five million tons of accumulated F
in the earth’s crust is non-biodegradable which is toxic to humans, animals and
plants (Singh et al. 2014). F accumulated in plant causes leaf necrosis and inhibits
photosynthesis and critical to plant growth enzyme activity. More than 260 million
people suffer from fluorosis in 25 countries worldwide and 66 million in India
(Chakraborti et al. 2016).
Increasing F contamination in groundwater and soil through anthropogenic and
geogenic activities, groundwater contamination is becoming a global problem as it is
common and uncontrollable. F geographical belts occur and India is one of them,
extending from Turkey through Iran, Iraq, Afghanistan to Japan and China
(Saravanan et al. 2008). F-endemic states are Andhra Pradesh, Gujarat Tamil
Nadu, Haryana, Punjab and all 33 districts of Rajasthan which are completely and
partially affected by F contamination due to the presence of F-rich rocks which are
basalts, mica, granites, etc. (Singh et al. 2018). Black and McKay studied first time
dental fluorosis in human, the brown patch called mottled enamel. The WHO
guideline for F in drinking water is 1.5 mg/L; above that guideline is unsafe for
human health (WHO 2004).
Drinking water is a major way of fluoride intake in the human body. The health
issue of eliminating high concentration F from water is very important for the
environment and for the public (Mohapatra et al. 2004). There are several methods
for removal of fluoride from water, such as chemical precipitation, ion exchange and
electrochemistry (Mohapatra et al. 2009). None of the method is easy and costly to
use for water purification to solve the groundwater pollution problem. Membrane
separation is based on two principles which are adsorption and filtration. Membrane
filters water at a lower cost, less energy consumption and reduces environmental
impact. Membrane has high efficiency in separation with easy maintenance, compact
modular structure and low effluent from chemical sludge. Membrane distinguishes
the metal ion on the basis of size and shape of the ion. Membrane performance
depends upon several factors like material used, pore size, structure, shape (design)
and fabrication methods. Membrane manufacturing using a variety of processes,
such as phase inversion, interfacial, polymerization, stretching, electrospinning,
pyrolysis, layer by layer deposition, slip casting and sol-gel. Different types of
membrane (organic, inorganic, hybrid) used in membrane technology as needed.
Different membrane technology are used in defluoridation of water on the basis of
pore size, types is reverse osmosis (RO), nanofiltration (NF), microfiltration (MF),
ultrafiltration (UF) and dialysis and electro dialysis processes. RO removes the
solutes from the stream through semipermeable membrane. Semipermeable
membranes serve as salt ion barriers. In Reverse osmosis process pressure exerted
to transfer molecules from one side to other side of semipermeable membrane.
Membrane commonly used in the RO system is made of polyamide and cellulose
acetate. But these membranes are not having a good outcome. Recently these
material composites are used with advanced modification like polyamide ultra-thin
membrane. RO membrane pores (0.0001–0.001μm) are small as opposed to MF and
176
Vijaylaxmi and S. Khan