Self-assembled materials are attractive for next-generation membranes. However, the need to align self-assembled nanostructures (e.g. cylinders, lamellae) and the narrow stability windows for ordered bicontinuous systems present serious challenges. We propose and demonstrate a novel approach that circumvents these challenges by exploiting size-selective transport in the water-continuous medium of a nanostructured polymer templated from a self-assembled lyotropic H1 mesophase. Optimization of the mesophase composition enables high-fidelity retention of the H1 structure on photoinduced cross-linking. The resulting material is a mechanically robust nanostructured polymer possessing internally and externally cross-linked nanofibrils surrounded by a continuous aqueous medium. Fabricated membranes show size selectivity at the 1- to 2-nm length scale and water permeabilities of ~10 liters m−2 hour−1 bar−1 μm. Moreover, the membranes display excellent antimicrobial properties due to the quaternary ammonium groups on the nanofibril surfaces. These results represent a breakthrough for the potential use of polymerized lyotropic mesophase membranes in practical water purification applications.

Nanostructured materials with precisely defined and water-bicontinuous 1-nm-scale pores are highly sought after as advanced materials for next-generation nanofiltration membranes. While several self-assembled systems appear to satisfy this need, straightforward fabrication of such materials as submicron films with high-fidelity retention of their ordered nanostructure represents a nontrivial challenge. We report the development of a lyotropic liquid crystal mesophase that addresses the aforementioned issue. Films as thin as ∼200 nm are prepared on conventional support membranes using solution-based methods. Within these films, the system is composed of a hexagonally ordered array of ∼3 nm diameter cylinders of cross-linked polymer, embedded in an aqueous medium. The cylinders are uniformly oriented in the plane of the film, providing a transport-limiting dimension of ∼1 nm, associated with the space between the outer surfaces of nearest-neighbor cylinders. These membranes exhibit molecular weight cutoffs of ∼300 Da for organic solutes and are effective in rejecting dissolved salts, and in particular, divalent species, while exhibiting water permeabilities that rival or exceed current state-of-the-art commercial nanofiltration membranes. These materials have the ability to address a broad range of nanofiltration applications, while structure–property considerations suggest several avenues for potential performance improvements.

Lyotropic liquid crystals (LLCs) have drawn attention in numerous technical fields as they feature a variety of nanometer-scale structures, processability, and diverse chemical functionality. However, they suffer from poor mechanical...

A single-head/single-tail surfactant with a polymerizable group at each end is presented as a new simplified motif for intrinsically cross-linkable, gyroid-phase lyotropic mesogens. The resulting nanoporous polymer networks exhibit excellent...

Thin films of functional materials occur in a myriad of situations where control of their nanostructure and thickness are critically important for an underlying application. Examples can be found in fields ranging from photovoltaics, [1,2] photonics, [3] microelectronics, [4] sensing, [5] and membranes to name a few. [6] Membranes occupy a rapidly increasing share of research in separation and filtration technologies. In particular, nanoporous membranes are finding increasing mindshare in research and technology development for industrial-scale purification of wastewater, [7] pharmaceuticals, [8] and food products. [9] They are also considered promising as barrier components for nextgeneration batteries and fuel cells, and as adsorbents for separation and capture technologies. [10-12] Advances over the current state of the art in membrane science calls for the fabrication of thin films with a precisely defined nanostructure (feature size and orientation) and well-controlled thickness in the sub-1-µm regime. [13] Polymerizable liquid-crystalline (LC) mesophases of small molecules are of significant interest in this regard as they permit access to monodisperse features in the challenging 1-2 nm range by self-assembly. [14] Beyond the spontaneous formation of monodisperse, transport-regulating features, the orientation of the features must be suitably controlled in films of minimal thickness to yield optimized selective layers for membrane applications. [15] Films with larger-length-scale porosity are typically used as structural supports for the selective layer. The resulting thin-film composite (TFC) membrane displays sufficient mechanical integrity to prevent failure of the selective layer when pressure is applied to induce filtration across the membrane. [16] However, the TFC membrane form-factor imposes severe challenges for the fabrication of next-generation nanofiltration (NF) membranes based on self-assembled materials due to the convolution of nanostructure orientation and film thickness control during fabrication. Prior efforts in the field highlight the constraints associated with the above challenge. Studies on columnar LC mesophases typically either use compression with physical spacers (>1 µm) to control film thickness or use spin-coating to create sub-micrometer thin films. [17,18] Mechanical compression (with or without physical spacers) generally cannot reliably reduce the film thickness to the sub-micron regime. [19] In the context The preparation of thin films of nanostructured functional materials is a critical step in a diverse array of applications ranging from photonics to separation science. New thin-film fabrication methods are sought to harness the emerging potential of self-assembled nanostructured materials as nextgeneration membranes. Here, the authors show that nanometer-scale control over the thickness of self-assembled mesophases can be enacted by directional photopolymerization in the presence of highly photo-attenuating molecular species. Metrology reveals average film growth rates ...

Seven homologues of an amphiphilic gemini monomer were synthesized; and four of them (highlighted in red in the table) were found to form a bicontinuous cubic (Q) phase with glycerol or water and could be radically cross-linked with phase retention.

Chemical coagulants were immobilized into bead form using sodium alginate to treat tannery wastewater samples. The used chemical coagulants were ammonium aluminium sulphate (NH4Al(SO4)2), aluminium sulphate (Al2(SO4)2, calcium carbonate (CaCO3), sodium citrate (Na3C6HsO7). The effect of the chemical coagulant dose and tannery wastewater pH was studied on wastewater electrical conductance (EC), total dissolved solids (TDS), sulphates, chlorides, phenolphthalein alkalinity, total alkalinity and chemical oxygen demand (COD). The quantity of various pollutants present in waste water was reduced after treatment. The optimized dose and pH for maximum decrease in EC and TDS were 5g/L and 7, respectively. The maximum reduction in the amount of sulphates and chlorides present in tannery wastewater was observed at dosage of 0.5g/L and pH 7. A dosage of 5g/L and pH 7 was also found most favorable for maximum reduction in values of COD, phenolphtalein and total alkalinity. The chromium concentrations in tannery wastewater before and after treatment were determined by atomic absorption spectrophotometer. A reduction in chromium concentration was observed after  treatment. The promising results of the present study demonstrate that immobilization of chemical coagulants can make them more effective for wastewater treatment.

Membrane biofilm development was evaluated to improve treatment of domestic wastewater in low-temperature anaerobic membrane bioreactor (AnMBR). Three levels of membrane fouling were compared based on transmembrane pressure (TMP) in a bench-scale system with replicate membrane housings, separate permeate collection, and independent biogas sparging control. Permeate chemical oxygen demand (COD) was reduced by over 50 mg/L under high fouling conditions. However, permeate dissolved methane concentration was 2-3 times the predicted concentration by Henry's Law at saturation. Increasing biogas sparging to restore fouled membranes to neutral TMP did not negatively impact biofilm treatment performance. This suggests that the biologically active biofilm was tightly adhered to the membrane surface and could remain active without an appreciable impact on TMP. In the absence of high TMP, dissolved methane oversaturation persisted implying that methanogenesis in the biofilm was the primary driving force in methane oversaturation, not high TMP. RNA-based 16S rRNA sequencing, reverse transcription quantitative PCR (RT-qPCR) targeting the methyl coenzyme-M reductase (mcrA) gene, and performance observations indicated that the biofilm was comprised of a specialized microbial community enriched in highly active methanogens and syntrophic bacteria. The results describe a potentially attractive strategy to reduce effluent COD of low-temperature AnMBR by supporting syntrophy and methanogenesis in the membrane biofilm.