Adsorption of Azo Dye Eriochrome Blue SE on Al/Fe-Silicate Composite Material

An Al/Fe-silicate composite material is obtained by intercalating Al/Fe polyoxo complexes into the structure of montmorillonite clay with subsequent heating at 350°С. The composite material is studied via energy dispersive analysis, X-ray diffraction, SEM, and low-temperature nitrogen adsorption. It is shown that modifying raises the content of Al and Fe, the pore volume, and the specific surface area, relative to the original clay. The kinetics and equilibrium of adsorption of azo dye Eriochrome Blue SE on an Al/Fe composite material is studied for the first time. The adsorption capacity of the composite material with respect to the dye exceeds that of the clay by as much as 500%. It is established that the main physicochemical parameters influencing the adsorption of the dye are the pH of the dye solution, the content of the sorbent, and the initial concentration of the dye. It is found that the adsorption capacity of the material grows from 5.2 to 26.1 mg/g upon raising the initial concentration of the dye from 15 to 200 mg/L. The efficiency of removing the dye grows along with the content of the material and is 85% at 20 g/L. Raising the pH from 4.0 to 6.5 reduces adsorption through a change in the effective charge of the material’s surface. Results from an analysis using different models of adsorption show that the isotherm of the dye’s adsorption on the composite material is consistent with the Langmuir model (R2 = 0.991, Qmax = 36.1 mg/g). A comparison of kinetic data on adsorption and models of pseudo-first order, pseudo-second order, and intraparticle diffusion shows that the kinetics of adsorption is satisfactorily described by pseudo-second order kinetics.