Alleviation of Reverse Salt Leakage across Nanofiber Supported Thin-Film Composite Forward Osmosis Membrane via Heat-Curing in Hot Water

Abstract

Electrospun nanofiber with interconnected porous structure has been studied as a promising support layer of polyamide (PA) thin-film composite (TFC) forward osmosis (FO) membrane. However, its rough surface with irregular pores is prone to the formation of a defective PA active layer after interfacial polymerization, which shows high reverse salt leakage in FO desalination. Heat-curing is beneficial for crosslinking and stabilization of the PA layer. In this work, a nanofiber-supported PA TFC membrane was conceived to be cured on a hot water surface with preserved phase interface for potential “defect repair”, which could be realized by supplementary interfacial polymerization of residual monomers during heat-curing. The resultant hot-water-curing FO membrane with a more uniform superhydrophilic and highly crosslinked PA layer exhibited much lower reverse salt flux (FO: 0.3 gMH, PRO: 0.8 gMH) than that of oven-curing FO membrane (FO: 2.3 gMH, PRO: 2.2 gMH) and achieved ∼4 times higher separation efficiency. It showed superior stability owing to mitigated reverse salt leakage and osmotic pressure loss, with its water flux decline lower than a quarter that of the oven-curing membrane. This study could provide new insight into the fine-tuning of nanofiber-supported TFC FO membrane for high-quality desalination via a proper selection of heat-curing methods.

Novel Thin Film Nanocomposite Forward Osmosis Membranes Prepared by Organic Phase Controlled Interfacial Polymerization with Functional Multi-Walled Carbon Nanotubes

“…In order to mitigate the water crisis, scientists have focused on using membrane separation technology to desalination recently [3][4][5][6][7]. Among various membrane desalination technologies, the osmotic pressure driven forward osmosis (FO) technology has attracted extensive attention [8,9]. Different from reverse osmosis (RO) with external pressure driven, osmotic pressure is the driving force of FO process, in which the pure water of the low osmotic pressure solution is spontaneously diffused to the high osmotic pressure solution.…”

Evaluating Post-Treatment Effects on Electrospun Nanofiber as a Support for Polyamide Thin-Film Formation

“…A higher -COOH/-CONH (I 1446 /I 1541 ) ratio indicates that more acyl chloride was hydrolyzed with water molecules, forming a more linear form of the PA film. This can affect the separation performance of the membranes [ 59 ]. The results disclosed that the stronger the alkaline hydrolysis, the higher the ratio of -COOH/-CONH in the PA layer.…”

Estado del arte. Métodos de desalinización de agua

“…Consiste en poner el agua de mar, a través de una membrana semipermeable, en contacto con una solución que tenga una presión osmótica mucho mayor, por lo que las moléculas de agua pasan a través de la membrana hacia esta solución, de la cual posteriormente se separan soluto y solvente, dejando el agua desalinizada por una parte y el soluto en una solución de mayor concentración en la otra [12,69,70,71]. Se han propuesto solutos como dióxido de azufre, alcohol alifático, sulfato de aluminio, glucosa, fructosa, nitrato de potasio, amoníaco-dióxido de carbono [72] y bicarbonato de amonio.…”