A facile impregnation-pyrolysis method to construct gradual-transition wettability gradient wood-derived carbon membrane for use in oil-water separation and membrane extraction

Carbon membranes with gradual-transition wettability gradient were prepared from wood. • FeCl 3 as catalyst and hydrophilic modifier in the impregnation-pyrolysis method. • HGWCM with wettability gradual-transition from superhydrophilic to superhydrophobic. • HGWCM is an excellent support membrane for membrane extraction. • High average mass flux for 2,4-DCP and 260 h stability in membrane extraction. Gradient wettability materials show great potential for controlling fluid behavior. However, their fabrication methods are generally intricate, requiring expensive feedstocks. Achieving compatibility between hydrophilic and hydrophobic regions is also a critical challenge. Here, we report a method to prepare wood-based carbon membrane (GWCM) with gradual-transition gradient wettability by creating carbonization gradient and constructing Fe 3 O 4 hierarchical micro/nanostructures on the GWCM surface. In this method, FeCl 3 adsorbed onto the wood blocks is the decisive factor in creating gradient wettability, functioning as both a catalyst for wood carbonization and a hydrophilic modifier. Cutting GWCM1 yields two 0.5 cm-thick membranes, designated HGWCM, which exhibit a gradual-transition wettability gradient ranging from superhydrophilic to superhydrophobic. The obtained HGWCM demonstrates outstanding performance as a support membrane in membrane extraction. Even at a thickness of up to 0.5 cm, HGWCM containing 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF 6 ]) achieved an average mass flux of up to 3610 mg m −2  h −1 for 2,4-dichlorophenol (2,4-DCP), and the removal efficiency of 2,4-DCP remained unchanged after 260 h of continuous extraction. The oil-water separation performance of the HGWCM was also demonstrated. This work offers a facile, scalable and general method for preparing gradient-wetted materials and explores their application in membrane extraction. Download: Download high-res image (314KB) Download: Download full-size image