A Green Approach for the Simultaneous Removal of Organic Dyes and Emerging Contaminants Using PPy/rGO/MOF-Fe₃O₄-Based Nanocomposite

The contamination of water supplies by emerging contaminants (ECs) and industrial dyes has become a significant environmental threat. To remove Methylene Blue (MB) and Diclofenac Sodium (DCF) from wastewater, a novel PPy/rGO/MOF-Fe₃O₄ nanocomposite has been successfully developed. Additionally, the photocatalytic potential of the PPy/rGO/MOF-Fe₃O₄ nanocomposite was also demonstrated, showcasing nearly complete degradation of MB and DCF within 40 min. A range of analytical methods, such as XPS, FTIR, TGA, XRD, UV SEM, TEM, VSM, ICP-OES, and EDX, were utilized to analyze the materials. The Langmuir model, with correlation coefficients of R² = 0.999 for MB and 0.998 for DCF, more accurately represents the adsorption process than the Freundlich model. Furthermore, kinetic investigations demonstrated that chemisorption is the dominant mechanism, as supported by a pseudo-second-order model that showed good agreement with the experimental findings (R² = 0.997 for MB and DCF). In contrast, the pseudo-first-order reaction model showed R² values of 0.898 for MB and 0.872 for DCF, which also aligns well with the data. According to thermodynamic studies, the interactions between dye and emerging contaminants are exothermic, with ΔH^ο values for MB and DCF being − 17.76 and − 29.62 kJ mol^{− 1}, respectively. Additionally, the ΔG^o values for MB and DCF are − 3.977 and − 5.771 kJ mol^{− 1}, respectively, which indicates that these reactions are spontaneous. Significant adsorption capacities were demonstrated by the PPy/rGO/MOF-Fe₃O₄ nanocomposite, which achieved 215 mg/g for MB and 55 mg/g for DCF. Furthermore, the nanocomposite can easily be recovered for up to 8 cycles, enhancing its sustainability and offering a practical solution for industrial dye and other applications.