Methylene Blue Cationic Dyes Adsorptively Removed Using Polyaniline Doped with Tannic Acid

Introduction: This paper describes the adsorption efficiency of tannic aciddoped polyaniline (TPAni) to remove methylene blue (Mb) dye from its water-based solution. Ammonium persulfate (APS) was used as an oxidant in the polymerization process to prepare TPAni. Tannic acid-doped polyaniline was characterized using FTIR, FE-SEM, TEM, BET, and ZETA potential conductivity techniques. Methods: The Langmuir capacity isotherm was found to be 42.3 mg/g. Additionally, the effects of temperature, pH, contact time, and initial concentration of Mb were examined and optimized to 35°C, 8.50 minutes, 8 mg/L, respectively. Results: Temperature affects the Gibbs free energy, which is -3.356, -3.562, and -3.615 kJ/mol at 290, 300, and 305 K, respectively. Discussion: This shift in Gibbs's free energy implies that tannic acid-doped polyaniline has the ability to spontaneously and practically remove methylene blue dye. The measured change in enthalpy of 1.13 kJ/mol indicated the presence of physical contact between the adsorbent and the dye molecules. Conclusion: It can be concluded from this study that the heterogeneous surface of TPAni was involved in the adsorptive elimination of the Mb and that a multilayer formed during the adsorption experiment. The study also examined the impacts of several parameters: contact time, initial dye concentration, adsorbent dose, and pH of the solution. The optimum values of these parameters were found to be 50 minutes, 8 mgL⁻¹, 0.004 g, and 8, respectively. The effect of temperature was also investigated, and found that higher adsorption occurs at high temperature. It is clear from this study that tannic acid-doped polyaniline (TPAni) with a greater number of negative sites on its surface is a very useful and new adsorbent for removing cationic dyes from wastewater.