Dyes are widely used in manyfields as textiles, papers, plastics, and leather, therefore; more attentionhas been gained for the recovery of these dyes from aqueous solutions due totheir toxic, mutagenic and carcinogenic effect. There are many processes forseparation of dyes from aqueous solutions, such as coagulation andflocculation, membrane separation, oxidation or ozonation, electrocoagulationand adsorption 3-6.
The most suitable method among all these methods is adsorption due to low cost,simply operating and high efficiency. Recently biosorbents such as lignin7 andChitosan(CS), the linear cationic amino polysaccharide composed of ?-D-glucosamine, 6 attracted strong interest due to environmental and cost-effective.CS is extensively used in many fields such as biomedicals 8, drug delivery 9, adsorbents 10 and environmental protection 11 due to its hydrophilic, anti-bacterial activity, biocompatibilityand non-toxicity properties.
However, the solubility of CS in acidic medialimited some applications. To avoid this limitation, crosslinking of CS wasmade between the functional groups and different kinds of crosslinking such asepichlorohydrin 12, vanillin13, gluteraldhyde 14 and tripolyphosphate 15, however this crosslinking leads to decrease the efficiency of CSas adsorbent due to the consumption of functional groups in crosslinking 16, 17 Conducting polymer hydrogels consisting of polypyrrole (PPY) andCS was prepared by polymerization of pyrrole using methyl orange as dopant andferric sulphate as the oxidant in CS solution 18. This hydrogel exhibits good electrical conductivity, excellentswelling/de-swelling behaviors due to the participation of one dimensional PPYblocks in the hydrogel network 14. Recently, polypyrrole chitosan composite 15 was prepared by using potentiostat at a constant voltage.
InPPY/CS composite hydrogel 19, the participation of one dimensional PPY blocks in the formationof the hydrogel network avoids a possible migration of PPY from the hydrogel,this pH-sensitive composite showed good water absorbencies in distilled waterand saline solution.