Hybrid nanomaterials for efficient hexavalent chromium removal from waste water: activated charcoal sheet modification through polypyrrole and silver nanoparticles

The main aim of this research is to develop a new hybrid nanomaterial using activated charcoal sheet (AC), silver nanoparticles (AgNPs), and polypyrrole (PPY), called PPY-AgNPs@AC conducting polymer nanocomposite hybrid nanomaterials (CPNHNs) for effective removal of hexavalent chromium ions (Cr⁶⁺) from water in intermittent mode. The chemical synthesis of CPNHNs was achieved by adopting a two-step methodology; initially, the AC sheet was encapsulated with AgNPs by in-situ reduction method and then AgNPs@AC sheet so obtained was capped with PPY using in-situ oxidative suspension polymerization. The synthesized CPNHNs were thoroughly characterized using high-resolution field emission scanning electron microscopy (HR-FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDS). The hybrid nanomaterials were evaluated for adsorption of Cr⁶⁺ ions from water. The hybrid nanomaterial produced excellent results with adsorption efficiency (Ad%) of 99.8% and adsorption capacity (qe) of 380 mg/g for Cr⁶⁺ ions. Furthermore, various parameters such as pH, adsorbent dosage, initial Cr⁶⁺ ion concentration, temperature and contact time were extensively evaluated to understand their effect on Ad% and qe. In particular, we studied the recycling potential of PPY-AgNPs@AC CPNHN, which showed improved recycling performance, maintaining its effectiveness over five consecutive cycles without significant reduction. Our results demonstrate that PPY-AgNPs@AC CPNHN is not only highly effective in removing Cr⁶⁺ ions but also is a cost-effective and environmentally friendly option. In summary, the new PPY-AgNPs@AC CPNHN is expected to become an efficient and environmentally friendly material for removing Cr⁶⁺ ions from wastewater in water treatment processes.