Towards a Microplastic-Free Ocean: Green Photocatalysis for Mitigation of Micro- and Nanoplastic Marine Pollution

The presence of microplastics (MPs) or nanoplastics (NPs) in the ocean is one of our society's most pressing environmental issues. MPs and NPs cause health issues to the biota that consumes them and are being transferred throughout the tropic chain up to humans. Since MPs and NPs are first produced in upstream processes, reducing MPs inputs through management before introducing them to aquatic ecosystems is the best option to protect the ocean. Photocatalysis is a water treatment process that can achieve this goal. In this research, visible light photocatalysis in aqueous medium of polyethylene (PE), polystyrene (PS) and polyethylene terephthalate (PET) MPs and NPs was investigated using N-TiO2, C,N-TiO2 and C,N-TiO2/SiO2. The influence of pH, temperature, MPs' size and the semiconductor's form (powders or films) on the removal process was tested. All the variables influenced degradation and photocatalysis can reach in some cases 70% of MPs removal in 50 h of reaction. This information can guide the design of photocatalytic systems that reduce MPs pollution.