Charged Micropollutant Removal With Hollow Fiber Nanofiltration Membranes Based On Polycation/Polyzwitterion/Polyanion Multilayers

Abstract

Hollow fiber nanofiltration membranes can withstand much higher foulant concentrations than their spiral wound counterparts and can be used in water purification without pretreatment. Still, the preparation of hollow fiber nanofiltration membranes is much less established. In this work, we demonstrate the design of a hollow fiber nanofiltration membrane with excellent rejection properties by alternatively coating a porous ultrafiltration membrane with a polycation, a polyzwitterion, and a polyanion. On model surfaces, we show, for the first time, that the polyzwitterion poly N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine (PSBMA) can be incorporated into traditional polyelectrolyte multilayers based on poly(styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC). Furthermore, work on model surfaces allows a good characterization of, and insight into, the layer build-up and helps to establish the optimal membrane coating conditions. Membranes coated with these multilayers have high salt rejection of up to 42% NaCl, 72% CaCl2, and 98% Na2SO4 with permeabilities of 3.7-4.5 l·m(-2)·h(-1)·bar(-1). In addition to the salt rejections, the rejection of six distinctively different micropollutants, with molecular weights between 215 and 362 g·mol(-1), was investigated. Depending on the terminating layer, the incorporation of the polyzwitterion in the multilayer results in nanofiltration membranes that show excellent retentions for both positively and negatively charged micropollutants, a behavior that is attributed to dielectric exclusion of the solutes. Our approach of combining model surfaces with membrane performance measurements provides unique insights into the properties of polyzwitterion-containing multilayers and their applications.

Sustainable Membrane Production through Polyelectrolyte Complexation Induced Aqueous Phase Separation

“…Furthermore, polyelectrolyte complexation can lead to well defined thin films, polyelectrolyte multilayers, as demonstrated by Decher and Hong by alternate deposition of polycations and polyanions . This approach has gained widespread attention with thin multilayers being prepared in layer‐by‐layer fashion for several membrane applications such as nanofiltration, reverse osmosis, and gas separation . Polyelectrolyte multilayer based membranes have excellent separation properties, demonstrating that polyelectrolyte based materials hold great promise for separation, yet they still require a membrane support that was prepared by NIPS.…”

Nanofiltration membranes with dually charged composite layer exhibiting super-high multivalent-salt rejection

“…Previous studies have demonstrated that the dramatic change of rejection order always attributes to the reversal of membrane charge property [45,46]. The separation performance change after TMC treated can be explained as follows.…”

Preparation of multifunctional hollow fiber nanofiltration membranes by dynamic assembly of weak polyelectrolyte multilayers

“…So, it would be very beneficial to develop hollow fiber NF membranes at a lower MWCO, and for that the surface modification of a UF support using LbL assembly of PEMs is a very promising method. This approach was shown to successfully produce hollow fiber NF membranes with precise control over separation performance [30][31][32][33][34]. In these studies, LbL deposition is performed by dip coating (static coating) by immersing the hollow fibers into the solutions of PEs followed by intermittent rinsing steps.…”