Organic solvent nanofiltration (OSN) is gradually expanding from academic research to industrial implementation. The need for membranes with low and sharp molecular weight cutoffs that are able to operate under aggressive OSN conditions is increasing. However, the lack of comparable and uniform performance data frustrates the screening and membrane selection for processes. Here, a collaboration is presented between several academic and industrial partners analyzing the separation performance of 10 different membranes using three model process mixtures. Membrane materials range from classic polymeric and thin film composites (TFCs) to hybrid ceramic types. The model solutions were chosen to mimic cases relevant to today's industrial use: relatively low molar mass solutes (330–550 Da) in n-heptane, toluene, and anisole.

The development of controlled polymerization techniques in the last decade has enabled polymer brushes to be grown from inorganic substrates with precision. Less studied are brushes grown from concave geometries of high curvature, such as mesopores, despite their application potential in the separation sciences. The method used here, surface-initiated, activators-regenerated-by-electron-transfer, atom-transfer radical polymerization (SI-ARGET-ATRP), is used to grow a polystyrene brush grown from aluminum oxide pores of 5 nm diameter, to-date the most confined geometry in which ATRP has been conducted. The brush is characterized by TGA, AFM, and FTIR, the latter two methods applied specifically to the external brush. Additionally, permporometry as well as permeability and retention measurements are used to characterize the graft within the mesopores. We show that the brush length is tunable, that the brush length is solvent-dependent, and we also demonstrate the application potential of this hybrid material as an organic solvent nanofiltration membrane. This new class of membranes shows excellent performance: a toluene permeability of 2.0 L m⁻² h⁻¹ bar⁻¹ accompanied by a 90% rejection of diphenylanthracene (MW 330 g mol⁻¹).

Here, we report the covalent coupling of poly (styrene-co-maleic anhydride) onto γ-alumina to develop high-performance organic solvent nanofiltration (OSN) membranes. A high molecular weight (M _w ) alternating copolymer of maleic anhydride (MA) and styrene (St) was synthesized and directly grafted to the γ-alumina membrane, while commercially available low M _w random copolymers of St and MA were also investigated. We show that solute rejection and membrane permeability strongly depend on the nature of the applied copolymer. In particular, the M _w of the copolymer applied is potentially the key for improving the membrane performance. When a high M _w copolymer was applied, the grafted layer covered the surface of the membrane. This results in membranes with significantly improved rejection, while maintaining a high permeability. In contrast, we observed pore grafting by applying low M _w copolymers, which resulted in membranes with slightly higher rejection and dramatically lower permeability compared to unmodified membrane. The best results were obtained by grafting γ-alumina with a high M _w alternating copolymer. These membranes showed a solute rejection of 98% for Sudan Black B (457 g mol ⁻¹ ) in toluene, while the permeability remained high at 2.9 L m ⁻² h ⁻¹ bar ⁻¹ .

Microporous polymer frameworks have attracted considerable attention to make novel separation layers owing to their highly porous structure, high permeability, and excellent molecular separation. This study concerns the fabrication and properties of thin melamine-based microporous polymer networks with a layer thickness of around 400 nm, supported on an α-alumina support and their potential use in organic solvent nanofiltration. The modified membranes show excellent solvent purification performances, such as n-heptane permeability as high as 9.2 L m⁻² h⁻¹ bar ⁻¹ in combination with a very high rejection of approximately 99 % for organic dyes with molecular weight of ≥457 Da. These values are higher than for the majority of the state-of-the-art membranes. The membranes further exhibit outstanding long-term operation stability. This work significantly expands the possibilities of using ceramic membranes in organic solvent nanofiltration.

To the best of our knowledge, for the first time MIL-53(Al) and NH ₂ -MIL-53(Al) modified α-alumina membranes are investigated for the adsorption of organic dyes from organic solvents. These new, modified membranes show excellent adsorption of high concentrations of Rose Bengal dye in methanol and isopropanol solutions.

In this study we describe a novel and simple method to couple covalently poly (maleic anhydride-alt-1-alkenes) to γ-alumina nanofiltration membranes for the first time. The 1-alkenes varied from 1-hexene, 1-decene, 1-hexadecane to 1-octadecene. The grafting reaction was between the reactive anhydride moieties of the polymer and surface hydroxyl groups, resulting in highly stable bonds. The modified membranes were investigated for their permeation and rejection performance of Sudan Black (SB, M_w 457 Da) in either toluene or ethyl acetate (EA) solution, and very high rejections (> 90%) and high permeation flux were observed compared to unmodified membranes. Initially, the SB in toluene solution was found to bind strongly to the surface hydroxyl groups of the unmodified membranes, an effect not observed in EA solution.