Adsorptive removal of congo red, a carcinogenic textile dye by chitosan hydrobeads: Binding mechanism, equilibrium and kinetics

Physico-chemical investigation on adsorption of congo red, an anionic azo dye by chitosan hydrobeads has been carried out. Adsorption process has been found to be dependant on temperature with optimum activity at 30 °C. Both ionic interaction as well as physical forces is responsible for binding of congo red with chitosan. Theoretical correlation of the experimental equilibrium adsorption data for congo red–chitosan hydrobeads system would be best explained by linearized form of Langmuir isotherm model. The kinetic results follow pseudo second-order rate equation. pH of the experimental solution influenced congo red adsorption inversely, and ∼20.0% of the dye could be desorbed from the loaded beads by changing the pH of the solution to alkaline range (∼pH 12.0). Both sodium chloride and sodium dodecyl sulfate significantly influenced the adsorption process.