Superhydrophilic Al2O3 Particle Layer for Efficient Separation of Oil-in-Water (O/W) and Water-in-Oil (W/O) Emulsions

The separation of oil–water emulsion using superliquiphobic/philic porous coated materials has attracted considerable attention for dealing with environmental pollution and resource recycling issues. The coatings used may lack adequate surface mechanical and chemical durability. This paper proposes a simple method without other modifications for separating the oil–water emulsion. A porous layer was fabricated by superhydrophilic Al2O3 particles, which could separate oil–water emulsions. The particle layer has the property of underwater superoleophobicity after prewetting. For the oil-in-water (O/W) emulsion separation, a 0.3 μm Al2O3 particle layer was used. This layer had a pore size less than about 1 μm to minimize oil flow and to obtain a purity of oil recovery greater than 99 wt %. For the water-in-oil (W/O) emulsion separation, a 40 μm Al2O3 superhydrophilic particle layer was used. Larger particles were used to provide a more porous surface to facilitate oil flow through the layer, resulting in a purity of water recovery purity greater than 99 wt %.