A Study of Kinetics, Thermodynamics, and Adsorption Isotherms of Food and Textile Dyes Removal with SBA-15 Supported Polyaniline Nanocomposite

Developing of solid adsorbent for the removal of food and textile dyes in industrial effluents still remains as a high level research interest. In the present study, SBA-15/polyaniline nanocomposite was synthesized, characterized, and used as an adsorbent for the removal of food dyes (sunset yellow and indigo carmine) and textile dyes (titan yellow and orange G) is in water. The effect of pH, adsorbent dose, time, concentration, and temperature on the removal efficiency (%) of the adsorbent for the different dyes was separately studied. The adsorption kinetics (pseudo-first order and pseudo-second order), isotherms (Langmuir, Freundlich, and Temkin), and thermodynamics (Delta G degrees,Delta S degrees, and Delta H degrees) were also studied. The Langmuir adsorption isotherm showed a linear correlation coefficient (R-2) equal to about 1 for all the dyes, indicating that the adsorption occurred as a monolayer. The adsorption kinetics followed the pseudo-second order model with a rate constant, -k2, equal to 0.0002-0.0005 g/mg min, and the adsorption capacity, (q(e))(cal), for sunset yellow was equal to 149.25 mg/g, for indigo carmine 135.13 mg/g, for titan yellow 204.08 mg/g, and for orange G 151.55 mg/g. The adsorption proceeds with the decrease in free energy, negative enthalpy and decrease in entropy at 25 degrees C. The adsorbent was verified by recyclable for three cycles without loss in removal efficiency (%). Hence, SBA-15/polyaniline nanocomposite can be successfully employed for the commercial removal of food and textile dyes from aqueous solutions.