Aging of PS/PVC by UV-Fenton reaction and their potential photodegradation driven in the goethite/haematite constructed wetlands

As the wetland ecosystem is a potential sink of plastics pieces, the photodegradation of microplastics could be boosted by iron(hydr) oxides, which considered as the Fenton or Fenton-like reactions induced. However, the pathways and internal mechanisms by which iron(hydr) oxides enhanced the ultraviolet degradation of plastics in the wetlands remain unclear. Therefore, the degradation of polystyrene (PS) and polyvinyl chloride (PVC) under ultraviolet light (365 nm) was studied in the UV Fenton and simulated micro wetlands. Results showed that UV irradiation caused notable changes in the surface morphology of plastics. Fenton reaction led to more significant, and generated oxygen-containing functional groups such as C = O. The weight loss rate of PS reached 28.3 ± 6.64%, while PVC reached 35.6 ± 1.52%, significantly surpassing the individual conditions of UV light at 20.3 ± 1.66% and 20.98 ± 8.48%, respectively. The mechanism of •OH in the process of plastic degradation was elucidated, while analysis of the degradation products was conducted. The potential risks for the UV degradation of PS and PVC were explored in constructed wetlands by detecting the changes of microbes. After preliminary aging, microbial activity associated with the degradation of polycyclic aromatic hydrocarbon compounds produced during plastic degradation is enhanced. Therefore, there may exist microbial communities in wetland ecosystems that are capable of degrading plastic. This study supported a hypothesis that the goethite/haematite Microcosm Constructed Wetlands (MCWs) would be efficiency for the degradation of plastic. It would be proved further and the organic carbon releasing during the plastic degradation should also be focused on.