Adsorption of Anionic Dye by Cross-Linked Chitosan–Polyaniline Composites

Chitosan is one of the promising natural polymers with characteristics such as biodegradability, chemical inertness, biocompatibility, high mechanical strength, good film-forming properties, and low cost. In addition, chitosan is a nontoxic cellulose-like polyelectrolyte polymer hydrogel that is suitable for the fabrication of artificial muscles, as this material undergoes a large volume change in response to changes in pH, temperature, or solvent composition. Chitosan is used in a wide range of applications such as wastewater treatement and biosensors. However, in sensor applications, the poor electrical conductivity of hydrogels results in a poor response time and a high operational voltage limits its applicability in devices. Hence, composites have been attempted by incorporating a rigid conducting polymer (such as PANI) into a flexible matrix (such as chitosan) to combine the good processability of the matrix and the electrical conductivity of the conductive polymer. In the present study, the eco-friendly polymer/bio-polymer composite (polyaniline/chitosan) was used as adsorbent and was investigated for its ability to remove Erionyl Yellow from an aqueous solution. Scanning electron microscopy showed that the surface of the composite is rough with pleats, providing a good possibility for dye adsorption. Characterization of the composite was done by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The thermal properties of chitosan–polyaniline were studied by thermogravimetric and differentiel differential scanning calorimetry. Various experiments were carried out as a function of contact time, initial dye concentration (100 mg/L), and adsorbent dose. The equilibrium data were fitted to Langmuir, Freundlich and Tempkin isotherm models. The Langmuir model showed a satisfactory fit to the equilibrium adsorption data of the polyaniline/chitosan composite with an observed maximum dye adsorption of 854.70 mg/g.