Oily matrices, such as membranes, mesh, filter paper,

Oily
waste water and frequent oil disruption due to heavy discharge are responsible
for the natural water environment and environmental pollution, as well as large
losses in energy 1, 2. Oil contaminated water toxic chemicals that affect the
environment through food chain and also adversely affect human health 3 especially
in oil production, oil analysis, etc. in the industrial factory. Oil pollution
with water soluble organic pollutants has turned into one of the widespread
environmental issues. Traditionally, there is a tendency to absorb water for
the removal or collection of oil by mixing oil / water using drying materials.
4 Recently, inspired by effective interface materials with conventional
folding behavior, various researchers have tried to build superhydrophobic and
superoleophilic materials for oil / water separation, which
can cause water to run off the surface while allowing oil to permeate through.
So a simple, cost-effective and effective method for oil separation and
collection is needed. A great way to separate oil water mixture has been
improved. Among them, the filtration method has proved an effective method for
oil / water separation, due to its high separation efficiency, relative low
operation costs and excellent recycling performance 6-7. Generally, oil and
water are separated by filtration using matrices, such as membranes, mesh,
filter paper, ceramic and nanofilament 8, 9. Recently construction of hydrophobic materials with water contact angle (WCA) higher
than 1500 through the formation of micro/ nano hierarchical
structures with low surface energy of the surfaces have stimulated much
attention in the field of oil–water separation 10-12. Among the variety of materials cotton have received
considerable interest owing to their easy handling, high flexibility,
environment friendly nature, biodegradability and high efficiency 13-15.  Besides this advantages cotton also has a
difficulty. Cotton originally consists of cellulosic enamel containing hydroxyl
group in chemical composition. The disadvantages of water adsorption behavior
such as hydrophilicity cotton fabric. Multiple techniques including chemical
steam depositing method, layer technology, electrospinning technique and dip
coating, layer by layer, have been developed for hydrophobic (contact angle of
more than 90) and superhydrophobic (over 150 water contact angle) coatings on
the surface 16 -18 . Hoefnagels et al
19 made superhydrophobic cotton cloth by growing tiny silica particles on
cotton fibers for the production of a dual-shaped surface roughness. From fundamental and practical aspects view point
wettability and repellency are important character of solid surfaces. These
important properties of solid surfaces are controlled by surface geometry and
chemical composition (surface roughness) and hydrophobicity deals with lowering
the surface free energy with increasing the surface roughness 20. With the increase of industrial oily waste water and oil
spill accidents, the improvement of superhydrophobic materials for careful
absorption or direct separation of oil from water is greatly preferred, due to
their high efficiency of separation and secure recyclability 21. Very recently, the oil–water separation efficiency and
self-cleaning properties were intensively investigated by polydopamine coated
superhydrophobic cotton fabric using silver (Ag) nanoparticles with
1H,1H,2H,2H-perfluorodecanethiol 22. Superhydrophobic fabric for oil-water
separation with the ability to self-cleaning by applying organically modified
silica aerogels and polydimethyl-siloxane has been reported 23.

            Among all of them
fluorochemicals coating dominate the water repellence behavior
to fabrics by sufficiently lowering surface energy although it has high cost. Fluorocarbon compounds are the suitable candidates due to
their unique properties, such as high thermal stability, excellent chemical resistance, low friction coefficient, superior
weatherability, oil and water repellence, low flammability, low dielectric
constant, etc.23–26. Application of perfluorochemicals can be
performed in a variety of ways such as pulsed plasma polymerization of monomers
with long perfluoroalkyl chains 27, chemical vapour deposition involving
polymerization of perfluoromethylmethacrylate 28 to obtain a hydrophobic
coating. In a very different approach direct fluorination of twaron fiber
changed the nature of the fiber surface 29. Surfaces
with regularly aligned and closely packed CF3 groups have been
reported to exhibit surface energy of 6.7 mJ 
m2, which is well below the 18– 20 mJ 
m2 value for polytetrafluoroethylene (PTFE) 30.

            Recently a new method of hydrophobic as well as oleophobic
finishing has been utilized as a guide for modifying the surface by forming on
to it water insoluble continuous ultrathin polymeric film which is links to
solid surface material by polar bonds. This method has termed admicellar
polymerization (AP) 31. This is a surfactant-assisted
polymerization to the coat fabric with the structure of a thin layer of at
least 10 nm 32 and does not change the clarity characteristics of cotton
cloth such as softness, breathability etc.
A molecular structure of surfactants constitutes hydrophilic head group and
hydrophobic tail group and can form stable nanoscale
aggregates between both solutions and interfaces. This aggregation is
called admicell. When a common organic monomer
solution is embedded, it will partition in to the admicell core in a process called adsolubilization, in the
presence of an initiator this monomer undergoes polymerization reaction to form
a polymeric layer on the substrate of the surface (Fig:1). After the
polymerization surfactant in the upper layer may be removed by washing to
expose the polymeric layer on the substrate surface.
CMC plays an important role for the fluorosurfactant aggregation. Lower
CMC means low concentration and also less surfactant will be required for
adsorption at solid/liquid interface for admicellar polymerization with lower
cost. To get successful result by using little amount of chemicals is also an
important criteria in industry. Admicellar
polymerization has been successfully used to coat a polymeric thin film on
different substrate such as polystyrene over alumina 33, polystyrene on
cotton 34, polmethylmethacrylate on alumina pigment 35, polypyrrole on mica
36. Admicellar polymerizations have superior advantages over the above
process for its simplicity with low energy consumption when used on textile
fabrics. Beside this, AP process has unique advantages because it is completely
water based to coat individual fibers.

In the current study, we used the admicellar polymerization
process to insert a thin fluorocarbon film coat on cotton surface at both sides
to provide hydrophobic character by adsorption of small amounts of fluorosurfactant
and adsolubilization of fluoromethracrylates. A
valuable coating was obtained on the textile that repels water completely while
allowing the penetration of oil. Since
the water was completely placed on the textile surface, the oil could be
successfully separated from the mixture. The
prepared fabric maintained high separation efficiency and
stable recyclability by repeating experiments.
Details about the polymerization process, characterization and features of fluoropolymer
based the cotton fabric material are described here.