Facile Modification of NF Membrane by Multi-Layer Deposition of Polyelectrolytes for Enhanced Fouling Resistance

Abstract

Fouling not only deteriorates the membrane structure but also compromises the quality of the permeate and has deleterious consequences on the membrane operation. In the current study, a commercial thin film composite nanofiltration membrane (NF90) was modified by sequentially depositing oppositely charged polycation (poly(allylamine hydrochloride)) and polyanion (poly(acrylic acid)) polyelectrolytes using the layer-by-layer assembly method. The water contact angle was decreased by ~10° after the coating process, indicating increased hydrophilicity. The surface roughness of the prepared membranes decreased from 380 nm (M-0) to 306 nm (M-10) and 366 nm (M-20). M-10 membrane showed the highest permeate flux of 120 L m−2 h−1 with a salt rejection of >98% for MgSO4 and NaCl. The fabricated membranes M-20 and M-30 showed 15% improvement in fouling resistance and maintained the initial permeate flux longer than the pristine membrane.

Fabrication of Nanocomposite Membrane with Nanomaterial Filler for Desalination

“…This RO membrane delivers a flux of 128.6 L/m 2 h and 98.3% salt rejection at 15.5 bar, opening an avenue for a leap over the water permeability at the rejection level that has been pegged at 5 L/bar m 2 h over the past ten years. Formation of a thin PA layer by a modified preparation method and ultrahigh porosity of VACNT support membrane are the main factors for the high-performance RO membrane [112].…”

Recycling End-of-Life RO Membranes for NF Membranes via Layer-by-Layer Assembly and Interfacial Polymerization

“…26−29 As a simple and convenient surface modification method, LbL self-assembly is used to improve the substrate surface charge and wettability, modify the layer thickness, and modify the type of functional groups on the surface of the substrate by adjusting the coating parameters of LbL self-assembly. 30,31 DA was added to the cationic polyelectrolyte polyethyleneimine (PEI) solution as an additive so that, on the one hand, the adhesion of dopamine could improve the stability of the LbL self-assembled repair layer and, on the other hand, the stability of the coating is improved because PDA and PEI form covalent bonds via Michael addition or Schiff base reaction; in addition, the existence of a large number of amine groups in the coating improves the interface firmness of the repair layer and the PA layer. 29,32−34 PDA deposition initiated by oxygen in the air is generally a time-consuming process and tends to result in an uneven and unstable coating; thus, we performed rapid deposition of PDA using CuSO 4 /H 2 O 2 as a trigger.…”

“…The layer-by-layer (LbL) self-assembly method and the poly­(dopamine) (PDA) coating method are selected as the surface repair strategies for the regenerated ultrafiltration membrane. PDA generated after oxidative polymerization of dopamine (DA) has various functional groups such as phenolic hydroxyl, amine, and quinone, which endow these PDA coatings with versatile functionalities and properties, such as surface hydrophilicity and biocompatibility for materials; they also act as an intermediate layer for the postfunctionalization of material surfaces by subsequent reactions. − As a simple and convenient surface modification method, LbL self-assembly is used to improve the substrate surface charge and wettability, modify the layer thickness, and modify the type of functional groups on the surface of the substrate by adjusting the coating parameters of LbL self-assembly. , DA was added to the cationic polyelectrolyte polyethyleneimine (PEI) solution as an additive so that, on the one hand, the adhesion of dopamine could improve the stability of the LbL self-assembled repair layer and, on the other hand, the stability of the coating is improved because PDA and PEI form covalent bonds via Michael addition or Schiff base reaction; in addition, the existence of a large number of amine groups in the coating improves the interface firmness of the repair layer and the PA layer. ,− PDA deposition initiated by oxygen in the air is generally a time-consuming process and tends to result in an uneven and unstable coating; thus, we performed rapid deposition of PDA using CuSO 4 /H 2 O 2 as a trigger . After that, the regenerated UF membrane completed the surface repair work, and piperazine (PIP) was adsorbed on the surface of the repair membrane as the aqueous phase and reacted with trimesoyl chloride (TMC)/ n -hexane solution to form a PA layer.…”