Electrospun polymeric membranes are currently being developed for various applications due to their unique specifications in comparison with the conventional membranes. As electrospun membranes comprise nanostructures (with 3D structure and inter-connected pores) with dimensions lying within the lateral resolution of the microscope, the interpretation of electrospun membrane features is challenging. In this study, scanning electron microscopy and atomic force microscopy were used for characterization of an electrospun (N1) and two commercial membranes (N2 and N3). A self-supported electrospun nanofibrous nylon membrane was fabricated and characterized for pore size, pore size distribution, thickness, nodule size, and pure water permeation flux as well as rejection and flux decline during coke removal from a typical petrochemical wastewater stream. The obtained results show that the electrospun membrane had smoother surface. All membranes showed same separation performance, about 99% rejection, but higher permeation flux achieved for the electrospun membrane.