The performance of thin film composite (TFCL-LP(R)) membranes that were treated with hydrofluoric acid (HF) improved and their flux increased significantly without any loss in ion-rejection properties. In contrast, DESAL3 membranes do not show any significant change in transport properties after similar treatment with HF. We used scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements to determine why this difference in behavior occurs. The difference in microstructure, as described by the interstitial void model, seems to be responsible for their behavior after being exposed to chemicals like HF. Therefore, we attempt to correlate transport properties with the microstructural changes (smoothing of membrane ridge-valley structure or no change in density of spherulites) observed. This method of treatment seems to be very effective in simultaneously enhancing the flux and rejection of reverse osmosis membranes which have a typical ridge and valley structure.