Design and Performance Evaluation of Hybrid Nanofiltration Membranes Based on Multiwalled Carbon Nanotubes and Polyelectrolyte Multilayers for Larger Ion Rejection and Separation

Abstract

A polyelectrolyte multilayer (PEM) membrane of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS) is deposited on top of a thick-layer micrometer range of multiwalled carbon nanotubes (MWCNTs) assembled on a porous silicon carbide (SiC) tubular membrane support. MWCNTs are assembled "layer-by-layer" alternating oxidized CNTs and poly(allylamine hydrochloride)-modifi ed CNTs. The MWCNTs layer is crosslinked by annealing after the assembly. The MWCNT layer acts as a spacer between the PDADMAC/PSS PEM and the SiC support. The MWCNT support increases water permeability in 42% compared with the PEMs deposited without MWCNTs. Hybrid MWCNT-PEM membranes show high rejection for divalent ions, which increases directly with fl ux. A rejection up to 92% is measured for MgSO 4 and there is up to a 60% rejection difference between MgCl 2 and NaCl, making the hybrid MWCNT-PEMs highly appealing for nanofi ltration and monovalent and divalent ion separations

The Future of Layer-by-Layer Assembly: A Tribute to ACS Nano Associate Editor Helmuth Möhwald

“…Note that multilayer nanocomposites, made by LbL and Langmuir–Blodgett deposition, are extensively used in industry already, albeit produced using closely related, derivative methods. Some representative examples of these multilayer composites are those based on various forms of nanocarbons (graphene, graphene oxides, graphene, nanotubes, nanoribbons, graphene carbon quantum dots, etc . ,,− ) and those based on various forms of ceramic nanoplatelets (clay, metal oxides, MXenes, etc . ,− ). The former are employed in energy technologies, whereas the latter are used in membrane and coating technologies.…”

“…Furthermore, the first polyelectrolyte has to be assembled exclusively on top of the pores and should not penetrate into the pores, as otherwise these would be blocked. The intermediate layers should utilize a design in which the mesh size controls the retention of the analyte and also ensures the removal of specific pollutants . Finally, the outermost layer should reduce the fouling behavior of the membranes by controlling its hydrophilic properties and electrostatic repulsion. − …”

“…The intermediate layers should utilize a design in which the mesh size controls the retention of the analyte and also ensures the removal of specific pollutants. 91 Finally, the outermost layer should reduce the fouling behavior of the membranes by controlling its hydrophilic properties and electrostatic repulsion. 203−205 Introducing Channels in Biological Membranes.…”

Application of Nanofiltration and Reverse Osmosis Membranes for Tannery Wastewater Reuse

“…NF membranes achieved the highest permeate flux and lowest ion rejections in our study. The low salt rejection led to a brine waste stream with lower conductivity compared to RO membranes [26].…”

Nanoparticles in Polyelectrolyte Multilayer Layer-by-Layer (LbL) Films and Capsules—Key Enabling Components of Hybrid Coatings

“…Hybrid materials assembled using carbon nanotubes and polyelectrolytes were shown to operate as effective membranes for the separation and rejection of ions [120]. Furthermore, the high electric conductivity of carbon nanotubes in a polymer framework allowed the development of multi-walled carbon nanotubes-based thin film electrodes transparent in the mid-IR (infrared) range [121].…”