Adsorption of Congo red from aqueous solutions using cationic surfactant modified wheat straw in batch mode: Kinetic and equilibrium study

• Wheat straw was modified using CTAB.
• MWS was effective to adsorb Congo red (anionic dye) from solution.
• Adsorption equilibrium data can be fitted by Langmuir model.
• Pseudo-first-order kinetic model can predict the kinetic process.
• The process was spontaneous and exothermic.

An agricultural by-product, wheat straw, was treated using cetyltrimethyl ammonium bromide (CTAB) to improve adsorption capacity for the removal of Congo red dye (CR, anionic dye) from aqueous solutions in batch mode. The effect of contact time, CR concentration and temperature on adsorption was presented. The results showed that it was in favor of adsorption at pH 4–5 and lower temperature. Adsorption capacity of MWS for CR is 665 mg/g at 303 K. Three kinetic models, pseudo-first-order kinetic model, pseudo-second-order kinetic model and Elovich model, were selected to fit the kinetic data and pseudo-first-order kinetic model was best. Three adsorption isotherm models, Langmuir, Freundlich and Temkin, were used to fit the experimental data and Langmuir model was better available. The process was exothermic and spontaneous according to thermodynamic parameters. It was concluded that MWS be promising to adsorb anionic dye from solution.