Efficient oil-in-water emulsion separation in the low-cost bauxite ceramic membranes with hierarchically oriented straight pores

Abstract

Oil/water emulsion separation via the membrane technology attracts increasing attention because of the severe fresh water shortage. In this work, low-cost, hierarchically oriented bauxite membranes with straight pores have been successfully prepared by the combined phase inversion tape casting and screen-printing technique for low-cost, efficient oil-in-water emulsion separation. An oil-in-water emulsion with an average oil diameter around 1.90 μm is effectively separated. The initial permeation flux in the penetrants is measured to be 4.31 × 10³ and 10.35 × 10³ L/h m⁻² when feeding with the petroleum ether-in-water emulsion and n-hexane-in-water emulsion, respectively, and the corresponding rejection rate can reach up to nearly 100 %, demonstrating good oil-in-water emulsion separation performance via the bauxite membrane, which can be explained by the excellent hydrophilicity and good oleophobicity as well as the high pure water flux. In addition, the membrane fouling generated during the oil-in-water emulsion separation can be mostly recovered by sequentially backwashing with water and ethanol. In the end, the degradation and regeneration mechanism of the oil-in-water emulsion separation is proposed according to the evolution of wetting properties of the membrane during the degradation-regeneration cycle. These results indicate the hierarchically oriented bauxite membrane with straight pores is a promising low-cost membrane alternative candidate for efficient oil-in-water emulsion membrane separation.