Heterogeneous Fenton-like oxidative desulfurization of fuel using iron-modified lignin/S-g-C₃N₄ nanocomposite:...

Oxidative desulfurization (ODS) is an effective technology for achieving ultra-low sulfur levels in fuels to meet stringent environmental regulations. This study evaluates the effectiveness of an Fe@KL/S-g-C₃N₄ (Fe-doped Kraft lignin coupled with S-g-C₃N₄) nanocomposite for the oxidative desulfurization of dibenzothiophene (DBT) from model fuel. The synthesis and electronic structure of the composite were confirmed using FTIR, Raman spectroscopy, PL, UV-visible spectroscopy, XRD, FE-SEM, EDX, and XPS analyses, which confirmed that Fe-modified lignin was successfully coordinated with the S-g-C₃N₄ framework. The incorporation of iron and lignin improved Fe³⁺ redox cycling and •OH generation, increased active site accessibility, and lowered the optical band gap to 1.85 eV, which enhanced Fenton-like radical generation. The Box-Behnken Design (BBD) optimization identified the optimum reaction conditions as 0.3 g of catalyst, 32.5 min reaction time, and 60 °C. With H₂O₂ used as a green oxidant, a maximum sulfur removal of 98.37% was achieved. This study demonstrates that Fe@KL/S-g-C₃N₄ is a high-performance, economical and sustainable heterogeneous catalyst for ultra-low sulfur fuel production, while exhibiting high structural stability and reusability over multiple cycles.