Current solvents used in membrane preparation are often toxic, environmentally unfriendly and prepared from non-sustainable resources. It would be beneficial to replace common solvents, like N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF) and tetrahydrofuran, by “green” solvents. Among these, bio-based solvents were selected for this research, more specifically γ-valerolactone (GVL) and a set of glycerol derivatives. They were screened for their potential use as solvent for membrane preparation by determining solubility of a variety of common membrane polymers and by verifying their applicability in the process of phase inversion to create useful membranes with appropriate pore structures and separation properties. Polymer solubility was rationalized by Hansen solubility parameters. Membrane morphology was characterized by using scanning electron microscopy, while membrane performance was investigated using rose bengal (1017 Da) in water as feed to screen the potential to tune these polymer/solvent systems even toward the nanofiltration range.

γ-Valerolactone (GVL) was selected as a renewable green solvent to prepare membranes via the process of phase inversion. Water and ethanol were screened as sustainable non-solvents to prepare membranes for nanofiltration (NF). Scanning electron microscopy was applied to check the membrane morphology, while aqueous rose Bengal (RB) and magnesium sulphate (MgSO₄) feed solutions were used to screen performance. Cellulose acetate (CA), polyimide (PI), cellulose triacetate (CTA), polyethersulfone (PES) and polysulfone (PSU) membranes were fine-tuned as materials for preparation of NF-membranes, either by selecting a suitable non-solvent for phase inversion or by increasing the polymer concentration in the casting solution. The best membranes were prepared with CTA in GVL using water as non-solvent: with increasing CTA concentration (10 wt% to 17.5 wt%) in the casting solution, permeance decreased from 15.9 to 5.5 L/m²·h·bar while RB rejection remained higher than 94%. The polymer solubilities in GVL were rationalized using Hansen solubility parameters, while membrane performances and morphologies were linked to viscosity measurements and cloudpoint determination of the casting solutions to better understand the kinetic and thermodynamic aspects of the phase inversion process.

Galinsosides A (1) and B (2), new flavanone glucosides together with two known flavanones, 7,3′,4′-trihydroxyflavanone (3) and 3,5,7,3′,4′-pentahydroxyflavanone (4) have been isolated from an ethyl acetate- soluble fraction of Galinsoga parviflora. Their structures were assigned on the basis of spectral studies. Compound 1 showed significant antioxidant and urease inhibitory activity while compound 2 was moderately active. On the other hand, 2 showed inhibitory potential against α-glucosidase.