Green synthesis of pistachio shell-derived carbon nanofibers: synergistic photocatalytic activity in TiO₂ nanocomposites

Nanofibers represent an advanced class of fibrous materials characterized by diameters typically below 500 nm. Nanofibers can be prepared from various natural and synthetic polymers. A common method for fabricating nanofibers is electrospinning. When nanoparticles are present in the polymer solution, the electrospinning product can result in nanocomposite nanofibers. These nanomaterials have numerous industrial applications, particularly as adsorbents and catalysts. In this study, nanofibers were prepared from pistachio shell as the raw material through resinification, preparation of the polymer solution, electrospinning of the polymer solution, thermal stabilization, and carbonization. The effects of various factors, including solution injection rate, applied voltage, carbonization conditions, and polymer solution concentration were investigated. The produced nanofibers were evaluated using FE-SEM, FTIR, and UV-Vis analysis. The effects of polymer solution concentration (12–40 wt%), applied voltage (14–23 kV), and polymer injection rate (0.2–1.2 mL.h^− 1) on the diameter of nanofibers were experimentally examined. In the next step, nanocomposite nanofibers with TiO₂ nanoparticles, were prepared, and their ability to photocatalytically degrade methylene blue was measured. Finally, to evaluate the performance of the prepared nanocomposite, the photocatalytic degradation rate of methylene blue in aqueous solution was used. A removal percentage of 98.02 ± 1.2% (mean ± SD, n = 3) was achieved using 20 mg of nanocomposite, with an initial concentration of methylene blue at 50 mg.L^− 1 and a reaction contact time of 60 min. Kinetic analysis indicated that the reaction followed the pseudo-first-order model.