Improving the chlorine resistance property of polyamide TFC RO membrane by polyethylene glycol diacrylate (PEGDA) coating

This study investigated a new application of polyethylene glycol diacrylate (PEGDA) as a chlorine resistance layer in desalination membrane processes. Suitable chlorine resistance and high salt rejection were achieved through PEGDA coating onto thin film composite reverse osmosis (TFC-RO) membranes. The lab-made RO membranes were modified using in-situ polymerization by an aqueous solution of the PEGDA in various concentrations. The performance of the coated polyamide-RO membranes was investigated by a cross-flow permeation setup before and after exposure to 300, 600 and 1200 ppm hypochlorite sodium (NaOCl) for 1 h to test permeability and chlorine stability. The influence of the PEGDA layer on surface characteristics of TFC-RO membranes was also investigated by ATR-FTIR, SEM, X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The results of performance tests and elemental analyses such as XPS indicated that the coating of PEGDA layer could act as a passive and sacrificial layer against the chlorine attack. The investigation of one of the modified membranes including 30% PEGDA proved that in the same comparison after chlorination, the modified membranes (2.42%) kept less chlorine in their surface structure than the bare ones (4.04%). The permeate flux decrease of the PEGDA coated membranes after chlorination was less than the uncoated membrane. With increasing the polymer percentage of the layer, the chlorine resistance ability and salt rejection could be increased. However, the permeability was reduced. The results of the performance tests and analyses showed a chlorine-resistant membrane could be developed, as well as the maximum salt rejection increase and the minimum water flux recline after modification.