Enhancing oil-water separation in hydrocyclones using superhydrophobic/superoleophilic fiber microspheres

To overcome the separation scale limit of conventional hydrocyclones for microfine oil droplets, multiphase/multi-field coupling has emerged as a frontier in enhancing oil-water separation. In this paper, a novel modified fiber microsphere-coupled hydrocyclone (MFMCHC) for enhanced separation was proposed. The modified fiber microspheres with superhydrophobic and superoleophilic properties were successfully fabricated via electrospinning, electrospraying, and a one-step solvent immersion. The microspheres were systematically characterized. The effects of reaction time, dopamine, and octadecylamine concentration on surface wettability were investigated, along with the influence of operating parameters on separation efficiency. Results showed that after modification, the microspheres changed from milky white to black, with the formation of micro-nano rough structures on the surface and enhanced thermal stability. Wettability tests revealed a maximum water contact angle of 166° in air and an underwater oil contact angle of 0°, with complete oil spreading achieved in 1.9 s under optimal conditions. The modified microspheres also showed good stability under high-speed shear and prolonged water immersion. Separation experiments demonstrated that the modified microspheres significantly promoted oil droplet coalescence and growth, increasing the volume average diameter at the oil outlet from 35.63 μm to 50.60 μm. The coupled separator improved separation efficiency by 10.0%-23.1% over the conventional hydrocyclone. The separation efficiency increased with the overflow split ratio and inlet oil concentration, and the modified coupled separation system exhibited superior performance compared with the unmodified one across different inlet flow rates. This work offers theoretical and technical guidance for multiphase-coupled hydrocyclone design in oily wastewater treatment.