Preparation, Characterization, and Adsorption Performance of an Interlayer-Expanded PPy/Maghnite–Cu2+ Nanocomposite for Methylene Blue Removal

The development of efficient and low-cost adsorbents for dye-contaminated wastewater remains an important challenge in environmental remediation. In this study, an interlayer-expanded polypyrrole/maghnite–Cu2+ nanocomposite (PPy/Mag–Cu2+) was successfully synthesized through purification of raw maghnite, sodium activation, Cu2+ ion exchange, and in situ oxidative polymerization of pyrrole. The obtained hybrid was characterized by X-ray fluorescence, X-ray diffraction, Fourier-transform infrared spectroscopy, UV–Vis spectroscopy, scanning electron microscopy, and cyclic voltammetry. The results confirmed the successful incorporation of Cu2+ and polypyrrole while preserving the layered aluminosilicate framework. XRD analysis revealed a progressive increase in basal spacing from 17.49 Å for raw maghnite to 25.95 Å for the final nanocomposite, indicating effective intercalation and formation of an expanded hybrid structure. The adsorption performance of PPy/Mag–Cu2+ was evaluated for methylene blue removal under batch conditions. Adsorption was strongly influenced by contact time, pH, and initial dye concentration, with equilibrium reached after approximately 80 min and optimum removal at pH 9. Equilibrium data were best fitted by the Langmuir model, with a maximum monolayer adsorption capacity of 43.66 mg g−1, while kinetic data followed the pseudo-second-order model. These findings demonstrate that PPy/Mag–Cu2+ is a promising and cost-effective hybrid adsorbent for cationic dye removal from aqueous media.