Harnessing limonene and Fenton's reagent for enhanced micro- and nanoplastic removal from aquatic systems

Micro-nanoplastics (MNPs) are increasingly recognized as persistent and hazardous contaminants in aquatic environments, yet current removal strategies struggle to efficiently capture or degrade these small, hydrophobic particles. This review is driven by the hypothesis that combining limonene a naturally derived hydrophobic terpene with Fenton and photo-Fenton oxidation systems can create a dual-action remediation pathway capable of enhancing both the adsorption and degradation of MNPs. To evaluate this concept, we synthesised findings from recent studies examining limonene-based adsorption processes, advanced oxidation mechanisms, and hybrid treatment systems incorporating UV radiation, sonication, and surfactant interactions. Published data indicate that limonene can increase plastic-surface interactions by up to 40-60% due to its strong hydrophobic affinity, whereas Fenton-based systems can achieve degradation efficiencies ranging from 55% to 95%, depending on the polymer type, pH, and radical availability. When these processes are used together, several studies report significant enhancements in oxidation rates, improved ROS accessibility, and reduced treatment times compared to conventional Fenton systems alone. The review further highlights the emerging role of limonene-functionalized adsorbents and natural-chemical hybrid systems as sustainable alternatives to conventional synthetic materials. Overall, this work provides a comprehensive mechanistic framework that unifies adsorption-driven capture with radical-mediated degradation, offering new insights and practical directions for the development of eco-friendly, high-efficiency technologies for MNP remediation.