Dyes are widely used in many fields as textiles, papers, plastics
and leather therefore; more attention has been gained for the recovery of these
dyes from aqueous solutions due to their toxic, mutagenic and carcinogenic
effect. There are many processes for separation of dyes from aqueous solutions,
such as coagulation and flocculation, membrane separation, oxidation or
ozonation, electro-coagulation and adsorption 1-4. The
most suitable method among all these methods is adsorption due to low cost,
simply operating and high efficiency. Recently biosorbents such as lignin5 and
Chitosan(CS), the linear cationic amino polysaccharide composed of                        ?-D-glucosamine, 4 attracted strong interest due to environmental and cost effective.
CS is extensively used in many fields such as biomedicals 6, drug delivery 7, adsorbents 8 and environmental protection 9 due to its hydrophilic, anti-bacterial activity, biocompatibility
and non-toxicity properties. However, the solubility of CS in acidic media
limited some applications. To avoid this limitation, crosslinking of CS was
made between the functional groups and different kinds of crosslinking such as
epichlorohydrin 10, vanillin11, gluteraldhyde 12 and tripolyphosphate 13, however this crosslinking leads to decrease the efficiency of CS
as adsorbent due to the consumption of functional groups in crosslinking 14, 15 Conducting polymer hydrogels consisting of polypyrrole (PPY) and
CS was prepared by polymerization of pyrrole using methyl orange as dopant and
ferric sulphate as the oxidant in CS solution 16. This hydrogel exhibits good electrical conductivity, excellent
swelling/de-swelling behaviors due to participation of one dimensional PPY
blocks in the hydrogel network 12. Recently, polypyrrole chitosan composite 13 was prepared by using potentiostat at constant voltage. In PPY/CS
composite hydrogel 17, the participation of one dimensional PPY blocks in the formation
of the hydrogel network avoids a possible migration of PPY from the hydrogel, this
pH-sensitive composite showed good water absorbencies in distilled water and
saline solution .

Graphene nanosheets, two-dimensional carbon nanomaterials, have
received significant attention due to the unique electronic, mechanical
properties, large surface areas 16 (theoretical value of 2600 m2/g) 18, excellent electronic conductivity, high chemical stability
and low manufacturing cost 19. Graphene displays high ?-conjugation and hydrophilic properties
however the functionalization of graphene is a requirement to improve the
chemical affinity for specific guest molecules and facilitate the dispersion in
aqueous media 20. Graphene oxide (GO)  has gained considerable attention as a significant
biosorbent (which is similar to carbon nanotube) due to presence of plenty
oxygen atom on the backbone in the form of epoxy, carboxyl and hydroxyl groups
protruding from its layers that can bind to dyes through electrostatic
interaction in addition to the high surface area 17. However, the surface of GO sheets are highly negatively charged
when dispersed in water due to the ionization of carboxylic acid and hydroxyl
groups on the GO sheets. This negative charge limit their application on the
adsorption of negatively charged dyes. Graphene oxide, glutaraldhyde,
crosslinked chitosan and CS/GO showed enhanced adsorption capacity for Au(??)
and pd(?), 21. A three
dimensional Chitosan/vacuum-stripped (VSG) grapheme/polypyrrole interface was
fabricated for dopamine detection. The sensor exhibits good selectivity, high
sensitivity, low detection limit and good sensing performance in human serum
samples 21, 22. A hierarchical
porous CS/VSG/PPY scaffold was prepared via a two-step strategy involving
freeze-casting and electro chemical polymerization techniques. To the best of
our knowledge, there is no reported study on the synthesis of PPC/GO
nanocomposite by chemical method, the performance of the nanocomposite still
not reported as adsorbent. With the purpose of developing low cost, with high
quality composite pushing us in the present work to synthesize PPC/GO
nanocomposite via insitu polymerization of PY in CS/GO dispersion.
Characterization of the composite has been carried out using fourier
transformed infrared spectra (FTIR), scanning electron microscope (SEM),
transmission electron microscope (TEM) and X ray diffraction pattern techniques
(XRD). The adsorption of ponceau 4R (as a model) into the nanocomposite was
studied. The kinetics and isotherm of the adsorption have been discussed. The
difference between CS/GO, GO and the PPC/GO nanocomposite toward the adsorption
of ponceau 4R was considered. Various parameters such as initial concentration
of dye, amount of adsorbent, contact time, temperature, pH, adsorption
isotherms and kinetics were studied, Also desorption process was tested to study
the reusability of sorbents. 

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