Enhancing the degradation of microplastics through combined KMnO₄ oxidation and UV radiation

The pervasive issue of microplastics in aquatic environments presents a formidable challenge to traditional water treatment methodologies, including those utilizing KMnO₄. This study pioneers advanced oxidation processes (AOPs) method aimed at improving the degradation of PE microplastics by employing a dual treatment strategy that combines KMnO₄ oxidation with UV irradiation. Detailed analysis of the surface modifications and chemical functional groups of the treated PE microplastics revealed the establishment of Mn-O-Mn linkages on their surfaces. Weight reductions of 3.9%, 4.9%, and 7.5% were observed for the KMnO₄/UVA, KMnO₄/UVB, and KMnO₄/UVC treatments over seven days, respectively. The emergence of carboxyl and hydroxyl groups played a crucial role in accelerating the degradation process. Notably, the combined application of UVC rays and KMnO₄ resulted in the most effective degradation of PE microplastics observed in our study. The process significantly enhanced the formation of MnO₂ particles from KMnO₄ oxidation, with concentrations ranging from 0.036 to 0.070 mM for KMnO₄/UVA, 0.066-0.097 mM for KMnO₄/UVB, and 0.086-0.180 mM for KMnO₄/UVC. Furthermore, the influence of varying pH levels, KMnO₄ concentrations, and different water sources on the degradation efficacy was investigated. The pivotal role of free radicals and reactive manganese species in promoting the degradation of PE microplastics was identified. A comparative evaluation with treatments solely utilizing KMnO₄ or UV light highlighted the enhanced effectiveness of the combined approach, demonstrating its potential as an efficient solution for reducing microplastic contamination in aquatic systems.