Synthetische Membranen für die Wasseraufbereitung: aktueller Stand und Perspektiven

Inorganic-Organic Hybrid Membrane Based on Pillararene-Intercalated MXene Nanosheets for Efficient Water Purification

Discharge of antibiotic-containing wastewater causes environmental pollution and threatens biological and human health. An efficient treatment method for this wastewater is urgently required. We prepared inorganic-organic hybrid MXene-pillararene nanosheets with a large lateral size (5-8 μm). The hybrid nanosheets were stacked on supports via vacuum-assisted filtration to prepare membranes with regular parallel slits and an interlayer spacing of 1.36 nm, which were used to purify antibiotic-containing water. Permeance through the membrane increased 100-fold compared with most polymeric and other two-dimensional nanofiltration membranes with similar rejection. This high permeance and rejection was attributed to the large lateral size of the nanosheets, regular interlayer spacing, and electrostatic interaction between the membrane and antibiotics. These membranes will broaden the applications of lamellar materials for the separation of high-value-added drugs in academia and industry.

Enhanced Desalination Polyamide Membranes Incorporating Pillar[5]arene through in-Situ Aggregation-Interfacial Polymerization-isAGRIP

Membrane-based desalination have an important role in water purification. Inspired by highly performant biological proteins, artificial water channels (AWC) have been proposed as active components to overcome the permeability/selectivity trade-off of desalination processes. Promising performances have been reported with Pillararene crystalline phases revealing impressive molecular-scale separation performances, when used as selective porous materials. Herein, we demonstrate that Pillar[5]arene PA[5] aggregates are in-situ generated and incorporated during the interfacial polymerization, within industrially relevant reverse osmosis polyamide-PA membranes. In particular, we explore the best combination between PA[5] aggregates and m-phenylenediamine (MPD) and trimesoylchloride (TMC) monomers to achieve their seamless incorporation in a defect-free hybrid polyamide PA[5]-PA membranes for enhanced desalination. The performances of the reference and hybrid membranes are evaluated by cross-flow filtration under real reverse osmosis conditions (15.5 bar of applied pressure) by filtration of brackish feed streams. The optimized membranes achieve a ∼40 % improvement, in water permeance of ∼2.76±0.5 L m^-2  h^-1  bar^-1 and high 99.5 % NaCl rejection with respect to the reference TFC membrane and a similar water permeance compared to one of the best commercial BW30 membranes (3.0 L m^-2  h^-1  bar^-1 and 99.5 % NaCl rejection).

Membrane Filtration with Liquids: A Global Approach with Prior Successes, New Developments and Unresolved Challenges

After 70 years, modern pressure-driven polymer membrane processes with liquids are mature and accepted in many industries due to their good performance, ease of scale-up, low energy consumption, modular compact construction, and low operating costs compared with thermal systems. Successful isothermal operation of synthetic membranes with liquids requires consideration of three critical aspects or "legs" in order of relevance: selectivity, capacity (i.e. permeation flow rate per unit area) and transport of mass and momentum comprising concentration polarization (CP) and fouling (F). Major challenges remain with respect to increasing selectivity and controlling mass transport in, to and away from membranes. Thus, prediction and control of membrane morphology and a deep understanding of the mechanism of dissolved and suspended solute transport near and in the membrane (i.e. diffusional and convective mass transport) is essential. Here, we focus on materials development to address the relatively poor selectivity of liquid membrane filtration with polymers and discuss the critical aspects of transport limitations. Machine learning could help optimize membrane structure design and transport conditions for improved membrane filtration performance.

Porous Polyelectrolytes: The Interplay of Charge and Pores for New Functionalities

The past decade has witnessed rapid advances in porous polyelectrolytes and there is tremendous interest in their synthesis as well as their applications in environmental, energy, biomedicine, and catalysis technologies. Research on porous polyelectrolytes is motivated by the flexible choice of functional organic groups and processing technologies as well as the synergy of the charge and pores spanning length scales from individual polyelectrolyte backbones to their nano-/micro-superstructures. This Review surveys recent progress in porous polyelectrolytes including membranes, particles, scaffolds, and high surface area powders/resins as well as their derivatives. The focus is the interplay between surface chemistry, Columbic interaction, and pore confinement that defines new chemistry and physics in such materials for applications in energy conversion, molecular separation, water purification, sensing/actuation, catalysis, tissue engineering, and nanomedicine.

Functional Liquid Crystals towards the Next Generation of Materials

Since the discovery of the liquid-crystalline state in 1888, liquid crystal science has made great advances through fusion with various technologies and disciplines. Recently, new molecular design strategies and new self-assembled structures have been developed as a result of the progress made in synthetic procedures and characterization techniques. Since these liquid crystals exhibit new functions and properties derived from their nanostructures and alignment, a variety of new functions for liquid crystals, such as transport for energy applications, separation for environmental applications, chromism, sensing, electrooptical effects, actuation, and templating have been proposed. This Review presents recent advances of liquid crystals that should contribute to the next generation of materials.

Ultrathin Alginate Coatings as Selective Layers for Nanofiltration Membranes with High Performance

It is highly desirable to develop environmentally friendly processes for fabricating thin-film composite (TFC) nanofiltration membranes (NFMs) from natural materials. However, the nanofiltration performance of such TFC NFMs is not satisfactory for practical applications owing to the lack of efficient methods for constructing ultrathin, uniform, stable coatings as selective layers. In this study, a contra-diffusion strategy is used to fabricate TFC NFMs with ultrathin cross-linked alginate coatings as selective layers without the use of any organic solvents. The as-prepared NFMs show a water permeation flux that is nearly one order of magnitude higher than that of other alginate-based TFC NFMs with similar salt rejection, and represents the best performance among all TFC NFMs from natural materials. These NFMs also demonstrate excellent mono-/divalent ion selectivity, as well as good long-term operation stability and antifouling properties. Furthermore, this strategy maximizes the reactant usage rate, minimizes the waste discharge and provides new insight into environmentally friendly fabrication of TFC NFMs.