Sustainable sunlight-driven remediation of PAH-contaminated soil using a green, waste-derived nanocomposite

Polycyclic aromatic hydrocarbons (PAHs) are persistent soil pollutants posing serious environmental and health risks due to their toxicity, carcinogenicity, and resistance to degradation. A key challenge in remediating PAH-contaminated soils is achieving efficient, low-cost, and pollution-free degradation under natural sunlight. This study reports a sustainable Fe3O4/carbon dots/silver iodide (Fe3O4/CD/AgI) nanocomposite, synthesised entirely from waste-derived precursors including industrial iron waste and wheat straw, for the sunlight-driven photocatalytic degradation of PAHs in contaminated soil. Characterisation by FTIR, XRD, SEM, and TGA confirmed the successful formation and favourable structure of the composite. Under optimal conditions (0.2 g catalyst per 4 g soil, 48 h solar exposure), complete degradation of naphthalene and while anthracene and pyrene showed removal efficiencies of approximately 65% and 71%, respectively. The composite exhibited enhanced efficiency, especially when combined with sodium persulphate, due to the synergistic contributions of magnetic recovery by Fe3O4, broad light capture by carbon dots, visible-light responsiveness of AgI, and persulphate-activated generation of reactive oxygen species (•OH, SO4•−, O2•−). This study demonstrates that a fully waste-derived, sunlight-responsive nanocomposite can effectively degrade both low- and high-molecular-weight PAHs, offering a low-cost, environmentally friendly, and scalable strategy for in-situ soil remediation.