Preparation of nanofiber microspheres and investigation of coalescence performance enhanced by the coupled swirling flow field

Droplet coalescence is widely applied in industrial production processes. Based on the theory of fiber coalescence, a novel method for enhance coalescence performance by nanofiber microspheres coupled with swirling flow field was proposed in this paper. The preparation process of gelatin/PLA nanofiber microspheres was systematically studied, and the key factors influencing their morphology and particle size were explored. The nanofiber microspheres were comprehensively characterized using SEM, ATR-FTIR, DSC, and contact angle measurements, and the effects of different operating parameters on coalescence performance were analyzed. The results showed that by optimizing the crosslinking temperature and electrospraying parameters, the morphology and particle size of gelatin/PLA nanofiber microspheres can be effectively controlled. Thermal crosslinking altered the intermolecular interactions and chemical group distribution of the microspheres, and the mass ratio of gelatin to PLA significantly affected their thermal properties and wettability. As the crosslinking temperature increased, the water contact angle gradually increased, reaching a maximum of 160° at 190 °C. When the gelatin content reached 75 %, the underwater superoleophobicity enhanced (oil contact angle was 168°). Coalescence performance experiments demonstrated that the introduction of nanofiber microspheres significantly enhanced the coalescence effect of oil droplets in the swirling flow field, and the Volume average diameter of oil droplets increased from 21.52 μm to 47.88 μm, which increased by 2.2 times. The findings provide important guidance for revealing the coalescence mechanism in the swirling flow field and designing efficient coalescence-enhanced swirl separation devices.