Discharging untreated oily wastewater into the environment disrupts the ecological balance

which is a global problem that requires urgent solutions. Superhydrophilic and superoleophilic fibrous medium (FM) effectively separated oil-water emulsion as it was hydrophobic underwater. But its separation efficiencies (SEs) first increased to 98.9%

then dropped to 97.6% in 10 min because of oil-fouling. To tackle this problem

FM deposited with 0%-10% silica nanoparticle (NPsFMs)

then coated by fluorocarbon polymer (X-[CH

2

CH

2

O

]

n

CH

2

CH

2

O-Y-NH-COOCH

2

C

4

F

9

) (FCNPsFMs)

was used to enhance its roughness and regulate its initial wettability to improve the anti-fouling property. FCFM and FCNPsFMs were hydrophobic and oleophobic in air and oleophobic underwater. Their water contact angles

oil contact angles and oil contact angles were 115.3°-121.1°

128.8°-136.5°

and 131.6°-136.7°

respectively

meeting the requirement of 90°-140° for coalescence separation. FCNPsFM-5 had the best separation performance with a constant value of 99.8% in 10 min

while that of FCNPsFM-10 sligh

tly decreased to 99.5%. Theoretical released droplet (TRD) diameter

calculated by the square root of the product of pore radius and fiber diameter

was used for the evaluation of coalescence performance. Analyzed by two ideal models

TRD diameter and fiber diameter showed a parabola type relationship

proving that the separation efficiency was a collaborative work of wettability

pore size and fiber diameter. Also

it explained the SEs reduction from FCNPsFM-5 to FCNPsFM-10 was revelent to the three parameters. Moreover

FCNPsFMs effectively separated emulsions stabilized by cationic surfactant CTAB (SEs:97.3%-98.4%) and anionic surfactant SDBS (SEs:91.3%-93.4%). But they had an adverse effect on nonionic surfactant Tween-80 emulsion separation (SEs:94.0%-71.76%). Emulsions made by diverse oils can be effectively separated:octane (SEs:99.4%-100%)

rapeseed oil (SEs:97.3%-98.8%)

and diesel (SEs:95.2%-97.0%). These findings provide new insights for designing novel materials for oil-water separation by coalescence mechanism.