Removal of Congo red dye by gemini surfactant C₁₂-4-C₁₂ · 2Br-modified chitosan hydrogel beads

In this paper, chitosan hydrogel beads were modified with gemini surfactant C12-4-C12 · 2Br and then used for the adsorption and removal of Congo red dye. The effects of pH, inorganic salt, temperature, shaking rate, and surfactant concentration were investigated in detail. The gemini surfactant concentration was the main factor, and the maximum adsorption amount was observed at 0.5% C12-4-C12 · 2Br. The Sips isotherm model fit well with the equilibrium experimental data, and the values of the heterogeneity factor (n) indicated heterogeneous adsorption. The adsorption kinetics was found to follow the pseudo-second-order rate model better than the pseudo-first-order rate model.