Enhancing oil-water separation via droplet coalescence regulated by particle self-rotation in swirling fields

Wastewater threatens water resources and human health, making effective treatment critical for ecological security. Hydrocyclones enable rapid oily wastewater separation but suffer from limited performance-dispersed droplets are easily sheared, broken, and escaped during processing. This study proposes a strategy for injecting particles into the hydrocyclone to address this issue. High-speed imaging captured the dynamic adhesion process between droplets and particles in the swirling field. Results show that self-rotating particles significantly shorten droplet coalescence, adhesion, and shedding times, and boost the particle capture efficiency of discrete droplets. Performance experiments demonstrate that injecting particles into the hydrocyclone achieves a separation efficiency of 95.8 %-a 28.1 % improvement over conditions without particle injection. The best separation enhancement was achieved when injecting spherical alumina particles. Compared to other enhanced oil-water hydrocyclonic separation methods (electric fields, air bubbles, and magnetic fields), this work achieves highly efficient separation with low energy consumption. This work provides a novel approach to enhancing hydrocyclone dehydration performance, with substantial research value and application potential for wastewater treatment and resource recovery in industry and energy sectors.