Oil-water mixtures can be passed through 2D-LCB membranes modified by superwettable materials to achieve complete oily wastewater treatment. The separation efficiency, flux, stability, cost, and sustainability of LCB membranes are the key parameters for assessing whether they can be applied in practice. Therefore, establishing simple preparation processes, low-cost raw materials, excellent separation efficiency, and high membrane strength, requires the further exploration of materials such as LCB composites for use in filter membranes. Yu
et al. prepared a corn straw powder-nylon 6, 6 membrane (CSPNM) using the phase-inversion method, achieving superhydrophilicity and underwater superoleophobicity [
88]. After 20 separation cycles, the oil rejection rate remained > 99.50%, with a flux of 1561.09 L m
-2 h
-1, indicating that the CSPNM possessed good reuse capability and environmental stability. A similar nylon membrane coated with a superhydrophilic/underwater superoleophobic cellulose-starch-silica (CSS) composite was designed by Zhang
et al., exhibiting a WCA and underwater OCA of 0° and 159.5°, respectively [
89]. The membrane possessed a mixture flux of 31,847 L
-1 m
-2 h
-1 bar
-1 and after 100 cycles, the separation efficiency remained above 97%, with the membrane able to be maintained for at least 24 h under extreme environmental conditions (pH 4–10), exhibiting high removal flux, good stability, and reusability. The separation of two-phase oil-water mixtures under laboratory conditions is idealized, while three-phase or more complex light oil/water/heavy oil mixtures are more representative of real wastewater conditions. Using the strategy of continuous gravity separation of three-phase oil-water mixtures, a dually prewetted LCB membrane with underwater superoleophobicity and underoil superhydrophobicity, has been shown to possess superior oil-water separation capabilities [
90]. A superamphiphilic waste corn straw powder (CSP)-coated fabric (CSPF) was designed by spraying CSP and polyurethane (PU) solutions onto cotton fabrics. The CSPF was dually prewetted using water and oil (DCSPF) to form a water-containing region (WCR) and an oil-containing region (OCR), respectively, in which the oil and water were selectively passed through the WCR or OCR to separate the three-phase oil-water mixtures. The average fluxes of water, light oil, and heavy oil in the DCSPF were ~3.8, ~8.9 and ~13.3 L m
-2 s
-1, respectively, with a three-phase mixture separation efficiency of over 97% maintained after 50 separation cycles. The Janus membrane with asymmetric surface properties was also found to perform very well in oily wastewater treatment. Utilizing cellulose and Ag nanoparticles, a double-sided Janus composite membrane (JCM) was fabricated by Lv
et al., with both superhydrophilic and superhydrophobic properties [
91]. The separation fluxes of oil-in-water and water-in-oil emulsions in the JCM were 640 L m
-2 h
-1 and 323.04 L m
-2 h
-1, respectively, with the separation efficiency exceeding 96%. At present, the trend in development of 2D-LCB materials for oily wastewater treatment has shifted from single- to multi-functional modifications and from single emulsion to multiphase emulsion treatments, supporting the development of low-cost, readily available, environmentally friendly, and sustainable materials. Therefore, further studies are required in order to transition from laboratory research to industrial applications.