Decomposition Rate and Microplastic Residue Formation of Photodegradable Resin-Coated Controlled-Release Fertilizers (CRFs)

This study investigates the decomposition kinetics and microplastic residue formation of the polymer-coated controlled-release fertilizers (CRFs) LN40 and Eco-LN40 under simulated photodegradation conditions. Eco-LN40, containing TiO2 as a photocatalyst, achieved complete decomposition (100 ± 2%) after 60 days of xenon-arc irradiation (p < 0.05), whereas LN40 achieved only 14–31% decomposition. Analytical characterization using TED-GC/MS, FTIR, and Raman spectroscopy confirmed that polyethylene (PE) signals completely disappeared in Eco-LN40 but persisted in LN40, indicating that microplastics did not form and that there was total oxidation into CO2 and H2O. SEM–EDS revealed Ti enrichment and surface fragmentation consistent with photoinduced radical oxidation. This study provides qualitative and mechanistic evidence that TiO-catalyzed photodegradation can eliminate polymer residues, mitigate the risk of microplastic contamination in agricultural soils, and support carbon-neutral fertilizer technologies.