Synthesis, characterization and applications of silylation based grafted bentonites for the removal of Sudan dyes: Isothermal, kinetic and thermodynamic studies

The potential of synthesized clay grafted with new organochlorosilanes as an inorganic-organic composite sorbent to remove Sudan dyes have been reported. The synthesized grafted bentonite was characterized via XRD, SEM, EDX, TGA, FT-IR, BET and XRF. The results form FTIR, XRD and DTA/TG confirms the grafting of silyl group to surface/interlayer of clays via reaction with the available -OH groups of clay, moreover, the basel spacing of modified clays were also different from pristine clay. The three kinetics models of adsorption, i.e., Pseudo-first order (Lagergren), Pseudo-Second-order and Fithian (diffusion model) were also studied in detail. The Pseudosecond-order kinetic model fits satisfactorily for adsorption of Sudan dyes. The adsorption behavior of dye on grafted silylated bentonite shows the following order: B-TPCS > B-DPDCS > B-PTCS > B-ODTCS > B-OTCS > B-CTMS. B-TPCS shows maximum efficiency (q(e) = 95 mg/g) at optimum conditions and follows Langmuir isotherm model which represents the homogeneity of adsorption sites. The results of thermodynamic studies (Delta G degrees, Delta H degrees and Delta S degrees) showed the spontaneous, endothermic and randomness in adsorption process. The method offers high adsorption capacity, cost effective with ease of preparation for Sudan dyes removal, further the modified clays will be explored for the sorption of other food toxins such as mycotoxin in future.