Phytic acid doped polyaniline nanofibers: An advanced adsorbent for methylene blue dye

Abstract In this paper, the boosted methylene blue (MB) dye adsorption efficiency of polyaniline nanofibers doped with phytic acid (DPANI) is premeditated. DPANI was prepared by simple radical polymerization method using phytic acid (PA) solution. The synthesized doped nanofibers were characterized by different techniques to investigate the surface morphology (SEM), atomic scale structure (HRTEM), crystalline or amorphous nature (XRD), functional groups on the surface (FTIR), composition (XPS), surface charge (ZETA Potential) and surface area (BET). DPANI displayed awfully superior adsorption capacity than undoped polyaniline nanofibers. The presence of the six phosphoric groups on the surface of DPANI is responsible for the enhanced interaction between MB and DPANI. The surface area analyser showed greater surface area of DPANI as compare to conventionally synthesized polyaniline due to the in situ nanofiber formation. Kinetic study of adsorption process was explored by fitting the adsorption data into different kinetic models: Pseudo-first order model, Pseudo-second order model and Intraparticle diffusion model. The results of kinetic study revealed that Pseudo-second order model was best fitted to the data and the adsorption occurred through chemisorption. The isotherm studies carried out using Langmuir model and Freundlich model confirmed that the Freundlich isotherm model fitted best to the adsorption data of the process and the isotherm Langmuir capacity was noted to be 43.4 mg/g. The effect of contact time, initial MB concentration, pH and temperature were also investigated and optimized to 60 min, 7 mg/L, 8.5 and 35° C respectively. The Gibb’s free energy changes with temperature (-3.466, -3.625 and -3.699 kJ/mol at temperatures 293 K, 303 K and 308 K, respectively). This change in Gibb’s free energy indicates that the removal of methylene blue dye by phytic acid doped polyaniline is feasible and spontaneous. The change in enthalpy was observed to be 1.1 kJ/mol, which revealed the existence of physical interaction (physosorption) between the dye molecules and the adsorbent. Surface alteration or doping of polyaniline nanofibers provides an alternate and effective modified adsorbent (DPANI) for wastewater remediation.