Synthesis and characterization of polyaniline, sucrose octaacetate and chitosan blend for removal of remazol black by adsorption: Equilibrium, kinetics, and regeneration

In this work, a polymeric blend of polyaniline (PAni) and chitosan (Chi), modified with Sucrose Octaacetate (SOA), was synthesized and characterized using different techniques. The blend was used as an adsorbent to remove Remazol Black (RB) dye from aqueous solutions. The blend was synthesized using the chemical oxidation method with ammonium persulfate as the oxidizing agent. Characterization was carried out using SEM, FT-IR, UV-Vis, BET, TGA, Conductivity, and PZc techniques. The blend structure appeared as clusters, providing a favorable surface area for adsorption. The results showed that SOA improved the conductivity of the blend without altering the structure and oxidative state of PAni. The study investigated the adsorption of RB, considering the influence of adsorbent dosage, initial dye concentration, pH, and temperature. Kinetic and equilibrium studies, thermodynamic analysis, synthetic effluent testing, and adsorbent reuse tests were conducted. The optimal adsorption conditions, within the studied range, were adsorbent dosage of 0.25 g L^-1, dye concentration of 60 mg L^-1, pH range of 2 to 7, and temperature of 30 °C. Equilibrium results indicated that the Langmuir model was the most representative, with a maximum adsorption capacity of q_max = 285.23 mg g^-1 and R_L = 0.01, indicating favorable adsorption. The kinetic study revealed an equilibrium constant of K_eq = 0.421 L mg^-1 and a process order 0.63. The adsorption process followed a pseudo-first-order kinetics, demonstrating rapid adsorption on the adsorbent surface. The adsorption was physical, endothermic, and spontaneous, showing increased randomness with temperature. RB removal from synthetic effluent was effective within the pH range of 2-7, with the dye removal efficiency from the aqueous phase remaining above 74 % for up to 4 cycles of adsorption-desorption. The results support the hypothesis that the PAni-SOA@Chi blend is a promising alternative for removing this dye from the waste.