Surface modification of seawater desalination reverse osmosis membranes: Characterization studies & performance evaluation
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AbstractIn this work we report surface modification of commercial reverse osmosis membranes by depositing ultrathin copolymer coatings, which could potentially enhance the biofouling resistance of RO membranes. Hydrophilic monomer hydroxyethyl methacrylate (HEMA) and a hydrophobic monomer, perfluorodecyl acrylate (PFDA) were copolymerized directly on the active layer of commercial aromatic polyamide reverse osmosis (RO) membranes using an initiated Chemical Vapor Deposition (iCVD) technique. Attenuated total reflective Fourier transform infrared spectra (ATR-FTIR) verified the successful modification of the membrane surfaces as a new FTIR adsorption band around 1730cm-1 corresponding to carbonyl groups in the copolymer film appeared after the deposition. X-ray Photoelectron spectroscopy (XPS) analysis also confirmed the presence of the copolymer film on the membrane surface by showing strong fluorine peaks emanating from the fluorinated alkyl side chains of the PFA molecules. Contact angle measurements with deionized water showed the modified membrane surfaces to be initially very hydrophobic but quickly assumed a hydrophilic character within few minutes. Atomic Force Microscopy (AFM) revealed that the deposited films were smooth and conformal as the surface topology of the underlying membrane surface remained virtually unchanged after the deposition. FESEM images of the top surface also showed that the typical ridge-and-valley structure associated with polyamide remained intact after the deposition. Short-term permeation tests using DI water and 2000ppm NaCl water showed that the deposited copolymer coatings had negligible effect on permeate water flux and salt rejection. © 2013 Elsevier B.V.
CitationMatin A, Shafi HZ, Khan Z, Khaled M, Yang R, et al. (2014) Surface modification of seawater desalination reverse osmosis membranes: Characterization studies & performance evaluation. Desalination 343: 128–139. Available: http://dx.doi.org/10.1016/j.desal.2013.10.023.
SponsorsThe authors would like to thank the King Fahd University of Petroleum and Minerals (KFUPM) in Dhahran, Saudi Arabia, for funding through the Center for Clean Water and Clean Energy at MIT and KFUPM under PROJECT NUMBER R5-CW-08. We would also like to thank Faisal Wali and Mohammad Nejib Hedhili of King Abdullah University of Science and Technology (KAUST), Saudi Arabia for the performing the XPS analyses. In addition, the authors would like to thank Owais Badr-uz-Zaman (KFUPM) for his continuous assistance with the permeation tests and Sadaqat and Luqman (KFUPM) for their help with the FESEM.