Enhanced removal of indigo carmine dye from aqueous solutions using polyaniline modified partially reduced graphene oxide composite

Abstract In this study, graphene oxide (GO) nanosheets were chemically modified by attaching polyaniline (PAN) nanoparticles to their surfaces, creating a polyaniline partially reduced graphene oxide composite (PAN@PRGO). This synthesized PAN@PRGO nanocomposite serves as an innovative and highly effective adsorbent for removing indigo carmine (IC) dye from water. The morphology and chemical composition of PAN@PRGO were analyzed using various techniques, including scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), confirming the successful grafting of PAN onto the GO surface. Batch adsorption tests showed that PAN@PRGO has an outstanding adsorption capacity for indigo carmine (IC) dye, achieving 490.0 mg g −1 at pH 5.0 and 298 K. This is notably higher than the adsorption capacity of GO nanosheets alone (317.25 mg g −1 ) and exceeds that of other materials reported in the literature. Additionally, PAN@PRGO demonstrated 100% removal efficiency for IC dye at concentrations up to 300 mg L −1 . The experimental data closely matched the Langmuir isotherm model and the pseudo-second-order kinetic model, suggesting that electron-sharing interactions between IC dye and PAN@PRGO contribute to the adsorption mechanism. The adsorbed IC dye was recoverable using a 0.1 M NaOH solution, with the composite retaining near-100% efficiency even after five adsorption–desorption cycles. These results indicate that the PAN@PRGO composite is a promising, reusable adsorbent for effective IC dye removal from industrial wastewater.