Study of increasing the flow rate of acoustic separation in a circular tube for microplastics collection

In recent years, microplastic pollution in the environment has been considered a problem. Neuston nets are widely used to collect microplastics, but the mesh size is approximately 300 μm, making it difficult to collect microplastics smaller than the mesh size. We have investigated the applicability of acoustic focusing for microplastic collection and demonstrated the collection of 10 μm particles. However, the flow rates in our previous studies were 1 mL/min, which was not sufficient for environmental distribution studies. Circular tubes are known to provide two-dimensional focusing and can increase particle collection efficiency. We experimentally investigated the performance of acoustic focusing in a circular tube with an inner diameter of 0.8 mm. The suspensions of 2, 6, 15, 200, and 300 μm particles were prepared and sent to the circular tube. We evaluated the focusing performance of the circular tube by measuring the focusing width. The experimental results showed that the acoustic separation in the circular tube could collect microplastics at a flow rate of 10 mL/min.