Increasing the success rate of interfacial polymerization on hollow fibers by the single-step addition of an intermediate layer

Abstract

In this paper, we introduce a single-step process that incorporates an intermediate layer on a hollow fiber to enhance the final membrane performance after interfacial polymerization (IP). This intermediate layer is applied during hollow-fiber spinning by complexation of two oppositely charged polyelectrolytes. Specifically, in this study, we consider the IP coating process an experimental success for a membrane sample with a NaCl rejection > 85%. The IP success rate is defined as the percentage of the samples with a NaCl rejection of > 85% within a studied group. The purpose of the intermediate layer is to increase the success rate of IP on the inner surface of the hollow fibers, typically a challenging task due to the cylindrical shape of the fibers. After the application of IP, the pure water permeance and NaCl rejection of the nascent membranes were tested to determine the success rate of IP. The IP success rate was 86-100% for the hollow fibers (HF) with intermediate layer, significantly higher than the 29% success rate achieved for IP on the support without intermediate layer. This surface modification approach is simple, time-efficient, and effective without any need for post-IP optimization that opens up new avenues for further developments for IP based dense hollow fiber membranes.

Modification of Polysulfone Ultrafiltration Membranes via Addition of Anionic Polyelectrolyte Based on Acrylamide and Sodium Acrylate to the Coagulation Bath to Improve Antifouling Performance in Water Treatment

“…Modification by polyelectrolyte is a promising approach for development of antifouling membranes due to polyelectrolyte’s high hydration ability, possibility to tune surface charge and versatility of chemistry, structure and modification techniques which can be implemented [ 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ]. Moreover, modification by polyelectrolytes is a flexible instrument for design of thin film composite membranes for microfiltration [ 29 ], ultrafiltration (UF) [ 30 , 31 , 32 , 33 , 34 , 35 , 36 ], nanofiltration (NF) [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ,…”

Forward Osmosis Membranes: The Significant Roles of Selective Layer

“…There are two main types of intermediate layers: nanomaterial layers and non-nanomaterial layers, according to the materials and construction methods. Nanomaterial intermediate layer made of MOF [ 79 ], GO-based materials [ 15 , 106 , 107 , 108 ], MoS 2 [ 109 ], oxidized-CNTs mixed layer [ 110 , 111 ], titanium dioxide (TiO 2 ) and nanotubes [ 104 , 112 ] have been successfully constructed in previous studies using methods such as vacuum filtration. Though the initial focus was mainly to increase the water flux by providing additional channels for water molecule transport, this intermediate layer will also serve as a surface modifier to provide a favorable surface for polyamide synthesis.…”

Effect of the Addition of Polyacrylic Acid of Different Molecular Weights to Coagulation Bath on the Structure and Performance of Polysulfone Ultrafiltration Membranes

“…This technique can contribute to surface modification due to the embedding of hydrophilic polymers or polyelectrolytes into the selective layer, which yields changes in the hydrophilicity, roughness, charge and chemical composition of the membranes. This approach was developed and studied in [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ].…”

“…Polyacrylic acid (PAA) [ 48 , 49 , 53 ], polyethylene imine (PEI) [ 37 , 41 , 43 ], copolymers Praestol 859 [ 47 , 51 ] and Praestol 2540 [ 50 ], poly (diallyldimethylammonium chloride) [ 41 ], chitosan [ 55 ], zwitterionic copolymers [ 56 ], poly (sodium 4-styrenesulfonate) (PSS) [ 40 ], PVP [ 52 ] and PVA [ 54 ] were applied as additives to the coagulant for preparation of flat-sheet and hollow fiber membranes. There are different purposes which can be achieved by the addition of hydrophilic polymers and polyelectrolytes to precipitation medium: Increase in membrane antifouling performance [ 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 56 ]; Formation of a separation layer after subsequent cross-linking [ 37 , 38 ] or reaction with oppositely charged polyelectrolyte [ 37 , 40 , 41 , 42 , 45 , 46 ]; Creating an intermediate layer for preparation of the composite membrane via interfacial polymerization (IP) technique [ 44 ]; Tailoring membrane surface charge for enhanced separation of charged molecules [ 39 ]. …”