Photocatalytic Degradation of Polyethylene, Polypropylene, and Sulfathiazole Using a UV/TiO2/Oxidant System

Abstract

Photocatalysis is widely acknowledged as an efficient technique for degrading a variety of pollutants, such as antibiotics, pesticides, herbicides, and microplastics. In this study, the micro-sized TiO₂ photocatalyst with the oxidizing agents (H₂O₂, periodate, and oxone) was investigated for the degradation of polyethylene (PE), polypropylene (PP), and sulfathiazole (STZ). Firstly, the photocatalytic activity of synthesized TiO₂ was evaluated by the decomposition of STZ (~ 94% within 30 min), and then the microplastic degradation experiments were conducted. The changes before and after the experiment were characterized using SEM, FTIR, and XPS. The weight loss for PE under the different combinations of experiments was UV (0%), UV/TiO₂ (∼5.7%), UV/TiO₂/H₂O₂ (∼17%), UV/TiO₂/Periodate (∼16%), and UV/TiO₂/Oxone (∼13.4%). The PP globules (~ 4 mm) did not have a significant impact on weight loss due to their large particle size and high rigidity. Meanwhile, PE showed improved weight loss due to a smaller particle size of ~ 20–100 µm. SEM images confirmed the degradation of the PE was significant while only a few surface modifications can be observed for PP. FTIR analysis revealed changes in carbonyl groups of PE and PP, including ketones (1720 cm⁻¹), acids (1718 cm⁻¹), esters (1735 cm⁻¹), and vinyl groups (1650 cm⁻¹). The synergy between the oxidants and the photocatalyst unquestionably enhanced the oxidation of the microplastics.