Preparation of Layer-by-Layer Nanofiltration Membranes by Dynamic Deposition and Crosslinking

Abstract

In recent decades, the advancements in layer-by-layer (LBL) assembly technology have provoked increasing interest in the preparation of multilayer polyelectrolyte membranes with excellent performance. In the current study, a novel nanofiltration (NF) membrane was prepared by pressure-driven layer-by-layer (LBL) assembly of polyethylenimine (PEI) and polyacrylicacid (PAA) on a porous substrate with chemical crosslinking. The effect of deposition pressure on separation performance of the prepared membranes was studied. The surface morphology, hydrophilicity and the charge property of the dynamically-deposited membranes were compared with those prepared by static adsorption. The characterization results showed that dynamic deposition process resulted in a smoother membrane surface with improved hydrophilicity. The mechanism of water-path formation was proposed to interpret the effect of pressure on the membrane performance. Glutaraldehyde (GA) was used as a crosslinker to reduce the number of polyelectrolyte bilayers for obtaining good separation performance. The rejections of different inorganic salts of the dynamically-deposited NF membrane were also investigated.

Modification Approaches of Polyphenylene Oxide Membranes to Enhance Nanofiltration Performance

“…This may be due to the low charge density of this PEL pair ( Table 1 ), the highest surface roughness and hydrophilicity for this membrane among surface-modified membranes (confirmed by AFM and contact angle data, presented below). Ethanol can pass through the membrane with a more effective surface area (due to high surface roughness) under pressure, forming special pathways for the transport of molecules through the relatively soft PEI/PAA layer (due to the low charge density of the PEL pair), resulting in the improved permeability [ 43 ]. The deposition of five PEL bilayers onto the PPO membrane led to the increased dye rejection coefficients ( Figure 4 b), attributed to the upper negatively charged PAA layer and its functional carboxylic acid groups [ 44 ].…”

Advances in surface modification and functionalization for tailoring the characteristics of thin films and membranes via chemical vapor deposition techniques

“…52 As a sub-category of dip coating, the layer-by-layer (LbL) assembly of membrane has received lots of attention. 53,54 Membrane with high water flux and salt rejection values were prepared by this method for desalination applications. For example, polyelectrolyte membranes were prepared by repeated dip coating of polycation and polyanion solutions 55 and graphene oxide (GO) membranes were prepared by dip coating of negatively charged GO on a positively charged membrane surface.…”

“…As a sub‐category of dip coating, the layer‐by‐layer (LbL) assembly of membrane has received lots of attention 53,54 . Membrane with high water flux and salt rejection values were prepared by this method for desalination applications.…”

Construction of Loose Positively Charged NF Membrane by Layer-by-Layer Grafting of Polyphenol and Polyethyleneimine on the PES/Fe Substrate for Dye/Salt Separation

“…Among them, nanofiltration (NF), addressing pore sizes in the range of 0.5-2 nm, can effectively separate monovalent/multivalent ions and retain organic dye molecules, which have been widely used in dyeing wastewater treatment [13,14]. However, traditional commercial NF membranes contain a dense separation layer that have high rejection rates for high-valent salts and dye molecules, and low permeation flux [15][16][17].…”