Separation of stable oil–water emulsion by the hydrophilic nano-sized ZrO2 modified Al2O3 microfiltration membrane

Membrane fouling weakens seriously the membrane's separating performance, which can be reduced by the membrane surface modification. Commercial Al2O3 microfiltration membranes were modified by the nano-sized ZrO2 coating to reduce the membrane fouling by oil droplets and to keep the unique character of the inorganic membrane. The nano-sized ZrO2 coating is prepared by in situ hydrolysis of ZrCl4. The results show that the nano-coating does not form a separating layer, and just makes the ceramic membrane more hydrophilic. Using the stable 1 g/L 20# engine oil–water emulsion as feed, the steady flux of the modified membrane is obtained in a very short time. The steady flux keeps 88% of the initial flux and the oil rejection is above 97.8%. The hydrophilic nano-sized coating, the backflushing and the appropriate cross-flow velocity contribute to reducing the membrane fouling by oil droplets. The modified membrane has the good performance in the oil–water separation of stable emulsions.

The SEM image of the cross-section of the modified Al2O3 membrane with nano-zirconia coating shows several Al2O3 particles in the support. The alumina particles’ surfaces can be divided into two regions: fresh Al2O3 cross-section area generated in the sample preparation process for SEM observation, and the surface covered with nano-sized ZrO2 coating.Figure optionsDownload as PowerPoint slideResearch highlights▶ Al2O3 microfiltration membrane was modified by the nano-sized ZrO2 coating. ▶ The nano coating distributes on the surface of alumina grains. ▶ The modified membrane becomes more hydrophilic. ▶ The steady flux is obtained in a very short time which is 88% of the initial flux. ▶ The oil rejection is above 97.8% using the stable 1 g/L oil-water emulsion as feed.