Polypyrrole Modified Zirconium Phosphate as an Effective Adsorbent for the Removal of Cr(VI)

Abstract

A novel polypyrrole modified α-zirconium phosphate (PPY-ZrPO4) nanocomposite was synthesized by in situ oxidative polymerization method followed by microwave irradiation process and characterized by XRD, FTIR, Raman, XPS, Zeta potential, N2 adsorption–desorption isotherms, and TGA-DTA analysis. Field emission scanning electron microscopy and transmission electron microscopy images revealed the spherical PPY polymer agglomerate with the surface of ZrPO4 nanoparticles. Meanwhile, the incorporation of polypyrrole onto zirconium phosphate nanoparticles provided a plentiful of active adsorption sites to interact with hexavalent chromium ions. Then the material used for removal of Cr(VI) and the various adsorption parameters like adsorbent dosage, concentration, effect of pH, contact time, stirring rate, coexisting ions were optimized by batch adsorption experiments. The Cr(VI) adsorption followed the pseudo-second-order kinetic model and Langmuir isotherm model with a maximum adsorption capacity of 62.5 mg. g -1 at room temperature at lower pH. The adsorption dynamic study demonstrated that the rate-determining step was controlled by surface diffusion, pore diffusion, and film diffusion. XPS spectra confirmed the simultaneous adsorption of Cr(VI) and in situ chemical reduction to Cr(III). Regeneration studies illustrated the efficiency of more than 80%, even after five cycles. Therefore, PPY-ZrPO4 nanocomposite could be a unique alternative to act as a promising adsorbent for the effective treatment of Cr(VI) containing wastewater..