Sunlight driven photo-treatment of polyhydroxybutyrate microplastics mediated by carbon nanodots-doped ZnO mesocrystals: Induced surface changes boost degradation in soil and biofilm formation

Plastics are widely used due to their versatility. However, their accumulation as microplastics and nanoplastics in the environment poses a significant threat for the ecosystems. Although biodegradable polymers, like polyhydroxybutyrate (PHB), offer a sustainable alternative, their degradation could still lead to fragmentation and MP accumulation, hence it is essential to enhance biodegradation rates in order to mitigate environmental impacts. This study investigates the integration of photocatalytic pretreatment with natural biodegradation to accelerate PHB biodegradation. Photoactive ZnO mesocrystals doped with biowaste-derived carbon nanodots, prepared via a wet-chemical approach, are proposed to improve the photocatalytic efficiency under sunlight. ZnO mesocrystals doped with 30 wt% of carbon nanodots exhibited superior photocatalytic properties, thus photodegrading PHB microplastics more efficiently than bare ZnO. Phototreated PHB microplastics exhibit an improved biodegradation in soil when exposed for a controlled irradiation time. Additionally, PHB microplastics photo-treated in the presence of doped mesocrystals showed an enhanced microbial colonization indicating improved biofilm formation. These findings highlight the potential of photocatalytic pretreatment in modifying surface properties to boost degradation in soil, thus offering a promising strategy for reducing microplastic accumulation.