Porous Al2O3 ceramics with directional gradient pore structure modified by cobweb-bridged WO3 nanowires for oil/water emulsions separation

A novel Al2O3 ceramic membrane modified by cobweb-bridged WO3 nanowires was successfully fabricated for oil/water emulsions separation. Freeze-casting was employed to obtain directional gradient Al2O3 porous ceramics at first. Then, the cobweb-bridged WO3 nanowires were successfully introduced into the separation layer by in-situ hydrothermal synthesis to construct the WO3 nanowires/Al2O3 membrane. Results showed that WO3 nanowires increased the surface roughness from 45.9 nm to 54.8 nm, the instantaneous water contact angle (WCA) and underwater oil contact angle (UOCA) reached the optimum values of 8.5 and 157.8, respectively. Construction of cobweb-bridged WO3 nanowires not only achieved a high separating efficiency of oil/water emulsions up to 92.35%, but also maintained high permeation fluxes at around 1600 L/m(2).h.bar. After 10 cycles, the separation efficiency of the membrane remained above 90%. Moreover, the WO(3 )nanowires/Al2O3 membrane still maintained underwater superoleophobicity after being immersed in strongly acidic, alkaline, and saline solutions, showing a high UOCA above 150 for all tested oil. The WO3 nanowires/Al2O3 membrane is promising in oil/water emulsions separation application for its high separation efficiency, durability, and excellent chemical stability.

Automated summary

A novel Al2O3 ceramic membrane modified by cobweb-bridged WO3 nanowires was successfully fabricated for the separation of oil/water emulsions. The modified membrane exhibited high separation efficiency, high permeation fluxes, and excellent chemical stability.