Photocatalytic Degradation of Microplastics by Heterostructured TiO₂/g-C₃N₄ Nanotubes under Solar Irradiation

Abstract

Microplastic pollution in aquatic environments has emerged as a global crisis, with an estimated 14 million tonnes entering the oceans annually. Current removal methods (filtration, coagulation) capture particles but generate secondary waste. We report heterostructured TiO₂/g-C₃N₄ nanotubes (TCN-NTs) that photocatalytically mineralize polyethylene (PE) and polystyrene (PS) microplastics under simulated solar irradiation. TCN-NTs achieve 94% PE mass loss and 89% PS mass loss within 72 hours, with CO₂ and H₂O as the primary products confirmed by isotope-labeled ¹³C tracing. The S-scheme heterojunction mechanism generates hydroxyl radicals (•OH) with an oxidation potential sufficient to cleave C-C backbone bonds. Pilot-scale testing in a 500 L solar reactor demonstrates 78% microplastic removal from real wastewater effluent.