Insertion of the rationally designed new cationic polymer in the polyamide membrane for efficient separation applications in water desalination Zeeshan Arshad 1 , Nadeem Baig 2 *, Shaikh A Ali 1,3 * 1Chemistry Department, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia. 2Interdisciplinary Research Center for Membranes and Water Security, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia 3Interdisciplinary Research Center for Advanced Materials, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia To improve the separation efficiency of the reverse osmosis (RO) polyamide membranes in desalination, the modification of the active layer can contribute efficiently, resulting in better anti-fouling properties and high flux 1 . A new cationic copolymer was synthesized and characterized as having monomer diallyl dimethylammonium chloride (DADMAC) and an amine-containing handle monomer to link with the active layer of the RO polyamide membrane. All the monomers are synthesized and then polymerized via free radical polymerization i.e Butler’s cyclopolymerization 2,3 with excellent yield. The synthesized copolymer was in situ incorporated in the membrane using the attaching points presented in the copolymer. The active layer containing the parts of the polymer was achieved. The AFM confirms the modified membrane surface that leads to better membrane flux. The cations present in the water were efficiently repelled by the grafted copolymer due to the cationic nature of the copolymer. The rejection of 98 %, 97 %, and 96 % has been shown for MgSO4 , MgCl2 , and CaCl 2 respectively by the modified RO membrane while it was 93 %, 90 %, and 89 % for the pristine RO polyamide membrane. The high flux and anti-fouling behavior were achieved by grafted RO membrane compared to the pristine RO membrane. The in situ grafting of cationic copolymers in the active layer of the RO membrane is a possible option for desalination applications to improve the overall efficiency of the system. References 1. W.D. Mulhearn, C.M. Stafford, Effects of Polyamide Chemistry on Solution Permeance in Molecular Layer-By-Layer Desalination Membranes, ACS Appl Polym Mater. (2021). https://doi.org/10.1021/ACSAPM.1C01529/ASSET/IMAGES/ LARGE/AP1C01529_0007.JPEG. 2. Butler, G. B. Cyclopolymerization and Cyclocopolymerization ; CRC Press, 2020. https://doi.org/10.1201/9781003066828. 3. Butler, G. B. Cyclopolymerization. J Polym Sci A Polym Chem 2000 , 38 (19), 3451–3461. https://doi.org/https://doi. org/10.1002/1099-0518(20001001)38:19<3451::AID-POLA10>3.0.CO;2-N
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