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Toxic solvents like n,n-dimethylformamide (DMF), n,n-dimethylethanamide (DMAc), and 1-methyl-2-pyrrolidone (NMP) are commonly used to fabricate polymer support membranes. Replacing these toxic solvents with green solvents such as Cyrene™ can imbue sustainability into membrane fabrication, but at the expense of poor membrane separation performances. Here we overcome this limitation by spray coating Cyrene™-based polymer dope solutions to form highly porous asymmetric membranes. The pure water permeance of spray-coated polyethersulfone (PES) membranes reached 68.9 L m−2 h−1 bar−1, 7-fold higher than knife cast membranes. This significant increase in permeance was ascribed to a porous, thin skin layer and macrovoids interconnected with finger-like pores in spray-coated PES films. However, this did not impact on the ability to yield thin film composites (TFCs) with high separation performances. Through interfacial polymerisation, we deposited a polyamide selective layer on to the surface of spray-coated PES films to yield TFCs for desalination of a 2000 ppm NaCl solution. The salt rejection rate and permeance of such TFCs reached 93% and 1.76 L m−2 h−1 bar−1, respectively. This desalination performance was similar to knife cast membranes produced from DMF-, NMP- and DMAc-based polymer dope solutions, but fabricated here in a more sustainable manner. This indicated that spray coating can overcome the trade-off between poor membrane separation performance and sustainability. © 2023 The Royal Society of Chemistry.

Three dipolar aprotic solvents were designed to possess high dipolarity and low toxicity: N,N,N′,N′-tetrabutylsuccindiamide (TBSA), N,N′-diethyl-N,N′-dibutylsuccindiamide (EBSA), and N,N′-dimethyl-N,N′-dibutylsuccindiamide (MBSA). They were synthesized catalytically by using a K60 silica catalyst in a solventless system. Their water immiscibility stands out as an unusual and useful property for dipolar aprotic solvents. They were tested in a model Heck reaction, metal–organic framework syntheses, and a selection of polymer solubility experiments in which their performances were found to be comparable to traditional solvents. Furthermore, MBSA was found to be suitable for the production of an industrially relevant membrane from polyethersulfone. An integrated approach involving in silico analysis based on available experimental information, prediction model outcomes and read across data, as well as a panel of in vitro reporter gene assays covering a broad range of toxicological endpoints was used to assess toxicity. These in silico and in vitro tests suggested no alarming indications of toxicity in the new solvents.

Hesperidin and rutin are two sought-after natural flavonoids, traditionally extracted from abundant natural citrus fruits and tea leaves using large amounts of ethanol or methanol solvents. Recent trends in extractions have focused on minimizing the use of solvents and creating simpler cost-effective processes. This study aims to apply the concept of chemical valorization in the context of a circular economy, by using agro-industrial waste and biobased alternatives to traditional solvents, which are of environmental concern. We use minimum amounts of solvent/sample (5 mL/0.25 or 0.5 g) to extract hesperidin and rutin in a single-stage solid-liquid extraction. Thirty individual solvents and HSPiP were applied to find the best solvents/blends for extraction. The type of solvent, sample preparation, maceration time, and extraction temperature were studied. Results showed that the biobased solvent Cyrene is very effective when mildly heated to 65°C (up to 91) or mixed with water. Adding water to Cyrene forms its geminal diol hydrate, this enhances the solubility and extraction of hesperidin and rutin up to ten times than those of the original pure ketone form. Quantitative sustainability metrics from the CHEM21 Toolkit demonstrated that our extraction methodology is environmentally friendly and offers future potential of isolation of other flavonoids.

This study explores a binary solvent system composed of biobased Cyrene and its derivative Cygnet 0.0 for application in membrane technology and in biocatalytic synthesis of polyesters. Cygnet-Cyrene blends could represent viable replacements for toxic polar aprotic solvents. The use of a 50 wt Cygnet-Cyrene mixture makes a practical difference in the production of flat sheet membranes by nonsolvent-induced phase separation. New polymeric membranes from cellulose acetate, polysulfone, and polyimide are manufactured by using Cyrene, Cygnet 0.0, and their blend. The resultant membranes have different morphology when the solvent/mixture and temperature of the casting solution change. Moreover, Cyrene, Cygnet 0.0, and Cygnet-Cyrene are also explored for substituting diphenyl ether for the biocatalytic synthesis of polyesters. The results indicate that Cygnet 0.0 is a very promising candidate for the enzymatic synthesis of high molecular weight polyesters.

The interest in adsorbing toxic gases nowadays is primarily due to their short- and long-term adverse health effects. It is generally accepted that the pore morphology and the surface nature play key roles in the adsorption mechanism of any molecules. The interactions between the adsorbate and adsorbent are affected by their polarity, where nonpolar surfaces would be attracted to a non-polar adsorbate, while polar surfaces have a higher affinity for polar molecules. The primary issue is access to a controllable set of materials with multiple functionalities that provide both polar and nonpolar surfaces for adsorption, which would present an advantage over single-phase adsorbents. Recently this has become available thanks to a novel class of bio-based carbonaceous materials (Starbon®). The functionality of these materials can be easily controlled by their temperature of preparation. The present work studies the nature of the surface chemistry and porosity of bio-based mesoporous materials Starbon and the role this plays in the adsorption of toxic volatile molecules such as ammonia, as a basic adsorptive and two acidic gasses (hydrogen sulphide and sulphur dioxide) using an InfraSorp optical calorimeter. Both hydrogen sulphide and sulphur dioxide adsorb better onto a hydrophobic surface, while ammonia adsorbs best onto a hydrophilic surface. The results showed that in both cases, Starbon significantly outperformed the industrially available powdered Norit® activated carbon (AC) and reacted chemically with the gasses to some extent.