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Understanding the diffusion process of hydrophobic molecules through natural phospholipid (half-)membranes is of great importance, as it occurs within organisms and therefore, offers potential applications in encapsulation in natural carriers. One illustrative case involves oleosomes, lipid droplets found in eukaryotic cells, which possess a phospholipid-protein monolayer facilitating the incorporation of lipophilic compounds into their inner core. Our approach entailed the development of a mathematical model to elucidate the diffusion of a lipophilic molecule, specifically curcumin, into oleosomes. In this model, oleosomes were represented as multilayer spheres with position-dependent diffusion and partition coefficients. We derived the model parameters through experimental techniques and stablished empirical equations. The model showed that 80% of curcumin reached the oil core while 20% stayed within the membrane (phospholipid heads and tails). Beyond its application to oleosomes and curcumin, the model presented herein holds broad application for describing the encapsulation of various lipophilic molecules into carriers featuring phospholipid (half-)membranes.

The advancement of technologies for producing chemicals and materials from non-fossil resources is of critical importance. An illustrative example is the dehydrogenation of glucose, to yield gluconic acid, a specialty chemical. In this study, we propose an innovative production route for gluconic acid while generating H2 as a co-product. Our concept involves a dual-function membrane, serving both as a catalyst for glucose dehydrogenation into gluconic acid and as a means to efficiently remove the produced H2 from the reaction mixture. To achieve this two membranes were developed, one catalytically active and one dense aimed at H2 removal. The catalytic membrane showed significant activity, yielding 16% gluconic acid (t=120 min) with a catalyst selectivity of 93% and stable performance over five consecutive cycles. Incorporating the H2 separating membrane showed the significance of H2 removal in driving the reaction forward. Its inclusion led to a twofold increase in gluconic acid yield, aligning with Le Chatelier's principles. As a future prospect the two layers can be combined into a dual-layer membrane which opens the way for a new production route to simultaneously produce gluconic acid and H2, using high-throughput reactors such as hollow-fiber systems.

This work simulates the production of methyl crotonate from various industrial wastewaters. In the upstream process, wastewater is fermented into volatile fatty acids which are then converted into polyhydroxyalkanoates (PHA) by means of mixed microbial cultures. In the downstream, PHA undergoes a series of thermolysis and esterification reactions to produce methyl crotonate. The origin of the wastewater was found to have a great influence on the composition of the PHA with the effluent of a candy bar factory producing a high polyhydroxybutyrate/polyhydroxyvalerate ratio of 86/14 in favour of methyl crotonate production. It was observed that the use of intracellular polyhydroxybutyrate, instead of purified, significantly lowers the number of separation steps and yet reduces the methyl crotonate recovery by only 20 %. An operating pressure higher than 18 bar led to more transesterification of polyhydroxybutyrate, producing byproducts instead of methyl crotonate. Finally, a 3 h reaction was found sufficient for completion of polyhydroxybutyrate conversion.

Hydrogen has gained renewed and growing interest around the world in the recent decades as a high-quality and renewable energy carrier, owing primarily to advances in fuel cells as well as growing environmental concerns. Steam reforming of fossil-based resources is currently the main route to H2 production. The downside of this process, however, is generation of massive amounts of greenhouse gases including CO2 as the byproduct which in turn must be captured to fully exploit the potential of H2. Membrane separation technology has seen significant growth, breakthroughs, and advancements over the last few decades and could be the key component in achieving inexpensive and highly pure H2. However, only a few numbers of membrane materials can withstand the harsh conditions of H2 production through steam reforming. Polybenzimidazole (PBI)-based membranes show excellent chemical, thermal, and mechanical stabilities as well as high intrinsic H2/CO2 selectivity. The objective of this review is to overview the recent development of structurally modified, cross-linked, mixed matrix, and hollow fiber membranes based on PBI for the development of industrially applicable H2-selective membranes.

Here we present the preparation of a novel positively charged covalent organic polymer (COP) based nanofiltration membrane. The porous COP selective layer grows on top of a polybenzimidazole (PBI) support from coupling reaction of 1,3,5-tris(bromomethyl)benzene and 4,4′−dipyridyl in alkaline conditions. Chemical and morphological analyses confirm the formation of a thin layer of COP (less than 50 nm), which is also evidenced by its high water permeance and salt retentions. Moreover, it is shown that COP membranes can form hydrogen bonds with HNO3, leading to a tighter membrane pore size that increases the NaCl retention from 46% to 75% without significantly losing its permeance. Further, the composite membranes demonstrated exceptional solvent and pH stabilities. The COP membranes showed a molecular weight cut off between 400 and 1000 g mol−1 together with pure solvent permeances of 0.91, 2.4, 3.3, 7.1 and 9.5 Lm−2h−1bar−1 toward dimethylformamide (DMF), ethanol, acetone, methanol an acetonitrile, respectively. The remarkable performance together with the stability in harsh environments make the newly developed COP membranes an attractive candidate for extreme nanofiltration.

Water recycling is one of the most sustainable solutions to growing water scarcity challenges. However, wastewaters usually contain organic pollutants and often are at extreme pH, which complicates the treatment of these streams with conventional membranes. In this work, we report the synthesis of a robust membrane material that can withstand prolonged exposure to extreme pH (of 1 or 13 for 2 months). Polyamine thin film composite (TFC) membranes are prepared in situ by interfacial polymerization between 1,3,5-tris(bromomethyl)benzene (tBrMeB) and p-phenylenediamine (PPD). Contrary to conventional polyamide TFC membranes, enhanced pH stability is achieved by eliminating the carbonyl groups from the polymer network. The membranes showed pure water permeance and molecular weight cutoff (MWCO) of 0.28 ± 0.09 L m-2 h-2 bar-1 and 820 ± 132 g mol-1, respectively. The membrane performance is further enhanced by manipulating the monomer structures and replacing p-phenylenediamine with m-phenylenediamine, resulting in a higher permeance of 1.3 ± 0.3 L m-2 h-1 bar-1 and a lower MWCO of 566 ± 43 g mol-1. Given the ease of fabrication and excellent stability, this chemistry represents a step forward in the fabrication of robust membranes for industrial wastewater recycling.