Oil/water separation membranes with stable ultra-high flux based on the self-assembly of heterogeneous carbon nanotubes

Abstract Due to the problem of membrane fouling, the preparation of oil/water separation membranes with stable ultra-high flux is still a challenge. At present, ultra-hydrophilicity is the main antifouling strategy, which indeed renders ultra-high base flux and high flux recovery rate. However, the flux usually declines to a low level during the real oil/water separation. With the assist of low surface energy (LSE) strategy, the flux stability can be remarkably enhanced, but at the cost of the reduced base flux. In order to combine the advantages of hydrophilic and LSE strategies, and avoid the undesired side effects of the LSE strategy, the distribution of hydrophilic and LSE microdomains on membrane surfaces is rationally designed and accurately manipulated in this study. Membranes are prepared by the vacuum-assisted self-assembly of heterogeneous carbon nanotubes (HCNTs), which consist of fluorinated multi-walled carbon nanotubes (FMCNTs), amino multi-walled carbon nanotubes (AMCNTs) and carboxylic single-walled carbon nanotubes (CSCNTs). AMCNTs and CSCNTs form great-area continuous and high porous hydrophilic microdomains through membranes, providing high base flux. FMCNTs form discrete linear LSE microdomains, providing good flux stability via LSE antifouling strategy. Except for the ultra-hydrophilic strategy, this study provides a reasonably and accurately manipulated LSE strategy in the energy-efficient membrane water treatment.