Evaluation of Microplastic Particle Size Distribution: A Study of the Buoyancy Weighing Bar Method with Variations in Weighing Bar Shape and Suspension Concentration

The buoyancy weighing-bar method (BWM) is an innovative method used to estimate the size distribution of floating particles, particularly microplastics. Apart from its easy operation, the BWM is capable of generating precise results when determining the particle size distribution. This research aims to investigate the efficiency of the BWM in determining the particle size distribution of Glass Bubbles Series iM16K, which possess a comparable particle size to microplastics (approximately 20 μm). The study explored different shapes of rods and initial concentrations of the suspension. There are two main shapes that were used in the experiment, rectangular and cylindrical rod. The cylindrical rod exhibited better particle size distribution compared to the rectangle rod due to its smaller surface area. It was observed that when the separation distance decreases, the drag force on the following particle reduces due to its smaller surface area. The variation carried out included modifying the initial concentration of the suspension to 0.001 to 0.05 m3-solid/m3-suspension. The BWM accurately determined the particle size distribution of suspension concentrations from 0.001 m3-solid/m3-suspension to 0.01 m3-solid/m3-suspension, indicating that the initial concentration falls within the lower and upper standard deviation, which due to the boycott effect. Based on the results obtained, the BWM could be used as an alternative method for particle size distribution.