Abstract <p>Polylactic acid has shown great potential as a substitute for traditional petroleum-based polymers. Such an environmentally friendly polymer has promising application prospects in high-value-added environmental protection applications, including wastewater treatment and membrane separation. This research presents a novel type of polylactic acid composite fibrous membrane designed to address this issue. A hydrophilic layer with a hydrogen bond cross-linked structure was formed via electrospinning PLA/PEG fibers. Subsequently, the silicone-modified carbon nanotubes were dispersed in a pure PLA solution. This composite spinning solution was electrospun onto the prepared PEG/PLA fibrous layer to construct a hydrophobic layer, forming a composite fibrous membrane. The introduction of silicone-modified carbon nanotubes had enhanced the membrane’s hydrophobicity, so that the wetting behavior of the outer surface followed the Cassie–Baxter model. The water contact angles of the hydrophobic layer of the composite fibrous membrane reached 123.5° (in air) and 162.7° (under oil), respectively. The oil absorption capacity of the prepared fibrous membrane reached 66.2 g/g. The prepared fibrous membrane could absorb oil on the water surface, underwater, or in emulsions. The hydrophilic layer constructed by PEG/PLA fibers in the composite fibrous membrane effectively prevented the destruction of the composite fibrous membrane due to oil swelling. Therefore, the prepared dual-layer structure polylactic acid electrospun composite fibrous membrane can be a good candidate material for treating oily wastewater.</p> Graphical abstract <p></p>