Polypyrrole modified granular activated carbon nanocomposite for treatment of wastewater containing highly toxic hexavalent chromium

Abstract

This study explored the fabrication of Polypyrrole (PPy) and Granular Activated Carbon (GAC) composites (PPy-GAC) for effective removal of toxic hexavalent chromium (Cr(VI)) from aqueous solutions. Two synthesis methods are employed: (1) electrostatic deposition of PPy onto pre-charged GAC paper and (2) in-situ chemical polymerization of pyrrole monomer with GAC particles. Batch adsorption experiments investigated the impact of various operational parameters on Cr(VI) removal. Compared to pristine GAC (54.64 mg g−1), the PPy-GAC composite exhibited a remarkable 3-fold increase in equilibrium adsorption capacity, reaching 175.44 mg g−1. Pseudo-second-order kinetic model (R2 > 0.999) accurately described the adsorption kinetics, while the Langmuir isotherm model (R2 > 0.99) provided a good fit for the equilibrium data. Maximum adsorption capacity (qmax) increased with temperature, reaching 204.08, 243.90, and 270.27 mg g−1 at 298, 308, and 318 K, respectively. Furthermore, a fixed-bed column experiment examined the composite’s effectiveness in continuous Cr(VI) removal, demonstrating its suitability for practical applications. Notably, the PPy-GAC composite successfully removed Cr(VI) from a real wastewater sample containing 68 μg L−1 Cr(VI) obtained from a ferrochrome industry, highlighting its potential for real-world remediation.