A hybrid polyaniline/dolomite–palygorskite framework for environmental remediation: experimental design and molecular-level adsorption interpretation

Abstract

Textile and dyestuff manufacturing industries are recognized as the largest source of water contamination. This study explores the effectiveness of the polyaniline@dolomite–palygorskite clay (PANi@DPC) hybrid composite for removing orange G (OG) dye from polluted water through adsorption. The PANi@DPC composite was analyzed by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The main findings prove the successful incorporation of PANi on the palygorskite surface. The PANi@DPC composite exhibited an open morphology richly decorated with nitrogen/oxygen-containing functionalities (e.g., –NH, NH and –OH), which boosts the diffusion and adsorption of OG dye. The OG dye adsorption experiments were conducted to assess the effect of the operational parameters. The PANi@DPC composite exhibited an impressive removal performance (>97.75%) for OG dye over a broad pH range of 2.6–8.4. Kinetics and isotherm data were adequately simulated by the pseudo-second order (R² = 0.997) and Freundlich (R² = 0.991) models. The PANi@DPC composite was effortlessly regenerated and efficiently reused for OG removal. FTIR analysis suggested that the adsorption mechanism is predominantly mediated by H-bonds and π–π stacking. Applying a response surface methodology, the highest OG removal performance of 99.54% was achieved under the optimal conditions of pH 6.0, 1.0 g L⁻¹ PANi@DPC dose, 20 mg L⁻¹ initial OG concentration, 120 min contact time and 25 °C. Advanced statistical physics simulation revealed that the OG adsorption follows multi-anchorage and multi-molecular binding mechanisms. Overall, the PANi@DPC hybrid composite can serve as a prospective binder material for cleaning up the OG dye-containing wastewater.