Optimization, kinetic, equilibrium and thermodynamics parameters for congo red adsorption from aqueous phase by untreated chicken feathers

The study of the adsorption of Congo red dye, a diazo carcinogenic compound, onto untreated chicken feathers was conducted in batch conditions. The optimization of the adsorption was evaluated using a Box-Behnken experimental design with three independent variables. It was observed that the best adsorption conditions were at pH 5, 30°C and using a semi-ground size of chicken feathers. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models were used to analyze the experimental data, the adsorption equilibrium was well described by the Temkin isotherm adsorption model and the maximum adsorption capacity of chicken feathers obtained by the Langmuir model was 97.8 mg g^–1 at 30°C. The results of the thermodynamic parameters showed the spontaneous nature, the feasibility of adsorption and the exothermic process due to the negative Gibbs energy value and the enthalpy value. FT-IR analysis confirmed the adsorption of Congo red on chicken feathers, showing that carboxyl and amino protonated groups from adsorbent were involved in the adsorption process.