Efficient removal of Acid Red 18 from aqueous solution by in-situ polymerization of polypyrrole-chitosan composites

Abstract To improve the adsorption ability of polypyrrole(PPy), the cheap and readily available biological resources chitosan (CS) was introduced to synthesize PPy-CS composites that were uesed to remove Acid Red 18 (AR-18). The structure and morphology of PPy-CS (9:3) composites were characterized by scanning electron microscopy (SEM), Zata potential, Brunauer-Emmett-Teller (BET), and Fourier transform infrared (FT-IR). Various factors were investigated to analyze how to affect the removal process. The reaction model between PPy-CS (9:3) and AR-18 was estimated by adsorption isotherm, thermodynamic parameters, and kinetic studies. The results showed that the adsorption was a spontaneous and endothermic process and the maximum adsorption capacity reached 285.71 mg/g. The removal mechanism suggested that electrostatic attractions and hydrogen bonding played essential roles during the adsorption. Additionally, the species and numbers of functional groups of dyes' molecules exerted a certain influence on the removal process. Also, PPy-CS (9:3) composites still exhibited removal efficiency of 70.83% after six regeneration cycles, which will be helpful in the practical application.