Efficient separation of oil-in-water emulsion using (MgCoNiCuZn)O high-entropy ceramic membrane

Abstract

In this study, we have successfully prepared (MgCoNiCuZn)O high-entropy ceramic membrane by the combination of diffusion-induced phase transformation and high temperature sintering. The membrane was used to separate oil/water emulsions. The results showed that the phase transformation between solvent DMAc and non-solvent H2O resulted in the formation of asymmetric pore structure including finger-like pores and sponge-like pores. After calcination, the porous structure was remained, and the transformation of high-entropy phase was completed. As the calcination temperature increased, the porosity decreased, resulting in densification of the membrane. However, the nanopore with the pore size of 3.433 nm was obtained after calcination at 850 ℃. The membrane exhibited good hydrophilicity in air and underwater oleophobicity, yielding the high pure water flux and separation efficiency simultaneously. After the calcination was performed at 900 ℃, a pure water flux of 6333 L/(m2⋅h) was obtained, and the separation efficiency of oil-in-water emulsion reached 99.87 %. The long-term stability of high-entropy ceramic membrane was studied. A flux of 520 L/(m2⋅h) was achieved even though the separation operation was performed for 10 h. After 10 h, the rejection rate consistently remained above 99 %, which proved that the membrane has excellent long-term stability.