Adsorption behaviors of acid dye by amphoteric chitosan/gelatin composite microspheres

Abstract

The use of amphoteric chitosan/gelatin composite microspheres (CGMSs) has been studied as an adsorbent for the removal of Acid Red 337 (AR337) from wastewater. The adsorbent was characterized by using several methods such as scanning electron microscopy and atomic force microscope (AFM). The kinetic study was performed based on pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations. It was shown that the adsorption process could be described by the pseudo-second-order equation, suggesting that the adsorption process is presumably a chemisorption. Freundlich, Langmuir, Dubinin–Radushkevich isotherms were used to analyze the adsorption equilibrium and the isotherm constants were evaluated at different temperatures. According to the Langmuir model, CGMS adsorbent exhibited the highest AR337 dye uptake capacities of 748.50 mg/g. The values of equilibrium parameter (0 < RL < 0.08) clearly exhibit that the adsorption of AR337 dye onto CGMSs is very favorable. In addition, various thermodynamic parameters, such as standard Gibbs free energy (Δ G °), standard enthalpy (Δ H °), and standard entropy (Δ S °) have been calculated. The adsorption process of AR337 dye onto CGMSs was found to be spontaneous and endothermic. Furthermore, the data from regeneration efficiencies for six cycles provided evidence of the high reusability of the CGMSs in the treatment of dye wastewater.