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

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 mu m is effectively separated. The initial permeation flux in the penetrants is measured to be 4.31 x 103 and 10.35 x 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 hydro-philicity 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.

Automated summary

In this study, low-cost, hierarchically oriented bauxite membranes were prepared and showed efficient oil-in-water emulsion separation. The membrane exhibited good separation performance, membrane fouling can be mostly recovered, and the degradation and regeneration mechanism was proposed.