A composite membrane including carbide-derived carbon (CDC) particles deposited onto a surface of an intermediate layer which is supported on a porous polysulfone substrate. The intermediate layer contains reacted units of a polyfunctional acyl halide (e.g. trimesoyl chloride) and polydopamine. Methods of making the composite membrane via techniques such as filtration-assisted deposition of CDC particles and interfacial polymerization are specified. Water flux and oil rejection (e.g. diesel) performances of the composite membrane are evaluated. A method of separating an organic compound, such as hydrocarbons, from an aqueous sample utilizing the membrane is also provided.