The trend in the change in roughness as a result of varied membrane composition was the opposite as for the water contact angle (Table 3). The roughness of the PBI/GO membranes monotonously increased from 16.5 nm for the pristine PBI up to 44.2 nm for , due to the accelerated rate of phase inversion by the presence of the hydrophilic GO [48,49] Nonetheless, the roughness decreased at the highest GO loading due to its probable agglomeration. The PDA coating and the replacement of GO with rGO both resulted in a smoother surface. Therefore, the improved hydrophilicity of the PBI/GO membranes can enhance the water permeance [50], because the more hydrophilic surface can adsorb more water and create a hydration layer, preventing oil interaction, which ultimately minimizes any fouling and improves oil-in-water emulsion separation [51].