High-efficiency and chemical-free microplastic recovery from laundry effluent using parallel and series acoustic focusing systems

• Acoustic focusing enables chemical-free microplastic fiber separation from water. • Compact device achieves 100 mL/min flow rate and 1000-fold microplastic enrichment. • Over 90% recovery efficiency demonstrated in real laundry wastewater samples. • Continuous microplastic fiber removal achieved without chemicals or coagulation. • Scalable design suitable for decentralized or household wastewater treatment. Microplastic fibers (MPFs) released from synthetic textiles during laundering are recognized as a dominant contributor to microplastic (MP) pollution in aquatic environments. Conventional wastewater treatment systems are not designed to capture low-density, fiber-shaped MPs, leading to their widespread environmental release. This study introduces a compact and scalable MP recovery system based on acoustic focusing, designed for chemical-free, continuous, and high-throughput separation. The system integrates a 10-tube parallel separation unit with a three-stage serial concentration module. This configuration achieves a flow rate of 100 mL/min and over 1000-fold enrichment of MP particles. Acoustic radiation forces focus MPs to the centerline of each stainless steel tube, enabling selective extraction without the need for filters, coagulants, or surfactants. Experiments using polystyrene and polyethylene particles, synthetic fibers, and actual laundry effluent confirmed the robustness and versatility of the system. Recovery efficiencies exceeded 90 % across a wide range of particle sizes (13–100 µm), including flexible fibrous MPs. The compact footprint of the device—approximately half the size of an A4 sheet and 2 cm thick—facilitates modular integration and on-site deployment. Compared to existing MP removal methods, this approach offers low maintenance, continuous operation, and high compatibility with domestic wastewater. Overall, this work demonstrates the technical feasibility of acoustic focusing for MP recovery and provides a practical platform for decentralized or household-scale wastewater treatment applications. These results suggest that the developed system could serve as an effective solution for mitigating MP pollution, thereby contributing to sustainable water treatment technologies at both household and industrial scales.