Novel Efficient Method to Continuously Collect Microplastics from Seawater via a Two-Phase System

Marine microplastic (MP) pollution has aroused growing public concern. Reliable analytical techniques are required to assess the extent of MP pollution. However, the detection of MPs is hindered by the challenge of separating them from complex environmental substrates. Herein, a simple and quick method to collect MPs from flowing seawater was proposed using a two-phase (tributyl phosphate (TBP)–water) system. The method can be used to efficiently and continuously separate multiple sizes of MPs at different depths. Due to the hydrophobicity of MPs, most of them would be collected at the two-phase interface. At the same time, due to the formation of MP–oil aggregates and the effect of buoyancy, very few MP–oil aggregates that enter the water phase return to the two-phase interface. Results from laboratory experiments revealed that the average recovery rate of the seven types of MPs (polypropylene, polyethylene terephthalate, polyvinyl chloride, polyamide 66, polycarbonate, polystyrene, and polyethylene) reached 95.67% ± 0.47%. Furthermore, this method was successfully employed to collect MPs from different seawater depths in Zhanjiang Bay, demonstrating its efficiency under real-world conditions. This method offers a novel approach for efficiently collecting MPs from flowing water with a high enrichment efficiency.