Photodegradation of Microplastics: Mechanism, Influencing Factors and Research Progress

Microplastics, as pollutants that are difficult to biodegrade in the environment, are widely distributed in soil, water bodies, and the atmosphere. They form complex pollution by adsorbing heavy metals and hydrophobic organic pollutants. Photodegradation, as an environmentally friendly degradation method, has attracted much attention. Photodegradation of microplastics includes direct photodegradation and indirect photodegradation. In direct photodegradation, photons directly act on the microplastic substrate, such as PE and PP, which absorb energy in the 270-300nm ultraviolet band, causing carbon-carbon bonds to break and form free radicals, which then transform into small molecules. Indirect photodegradation, on the other hand, relies on photosensitizers such as humic acid to produce active species that trigger degradation. The degradation rate of PS in water rich in DOM can increase by 2-3 times.