Phytic Acid Doped Polyaniline Nanofibers for Enhanced Aqueous Copper(II) Adsorption Capability

This study demonstrates the enhanced Cu²⁺ adsorption capability of polyaniline nanofibers (PAni NFs) by doping of phytic acid. The PAni NFs were synthesized by radical polymerization process using acidic solutions of hydrochloric and phytic acid, yielding chlorinated (Cl-) and phytic acid-doped (Ph-) PAni NFs. The Ph-PAni NFs showed remarkably higher Cu²⁺-adsorption efficiency than Cl-PAni NFs, presumably owing to high capacity and/or high ionic affinity of the doped phytic acid in Ph-PAni NFs. The pH-dependent adsorption capability exhibited increasing Cu²⁺ adsorption trend as increasing aqueous pH because of spontaneous deprotonation of the doped phytic acid in a basic environment. Furthermore, Ph-PAni NFs showed stable, high Cu²⁺ adsorption capability, irrespective of Co²⁺ concentration in the bimetallic Cu and Co aqueous solution. Surface morphologies of PAni NFs were investigated using electron microscopy, and molecular structures were identified using X-ray photoemission and Fourier transform infrared spectroscopies. The ability of PAni NFs to capture aqueous Cu²⁺ is discussed in terms of surface functional groups doped to NFs. Surface modification and/or doping to enhance the adsorption capability of Cu(II) introduced in this study will provide a great venue for expanding the use of many other polymeric nanostructures for reclamation in metal mining as well as the conventional environmental applications such as water purification.