Molar enthalpies of mixing (H E) were measured for the following deep eutectic solvents (DESs): {choline chloride + glycerol}, {choline chloride + ethylene glycol}, {tetrabutylammonium chloride + glycerol}, and {tetrabutylammonium chloride + ethylene glycol} at 323.15 K and molar ratios of 1:4, 1:3, 1:2 and 1:1. Results show that all systems are endothermic, with H E values ranging from 1.90 to 5.35 kJ·mol–1. Results indicate that the intermolecular interactions between the molecules of the pure components are stronger than those of the DESs complexes. To shed some light on the mutual interactions between the molecules within the mixtures, effects of the hydrogen bond acceptor structure (HBA), hydrogen bond donor structure (HBD), and concentration (HBA:HBD molar ratio) were analyzed. The nature of the HBA salt is the most important: choline chloride-based systems required almost twice as much energy as tetrabutylammonium chloride-based systems in order to form the DES mixture, most likely because of a higher enthalpy of fusion of the choline-based HBA salt. Choline chloride is more stable than tetrabutylammonium chloride because of its hydroxyl group; consequently, more energy is needed to break the choline chloride interactions in order to form DES mixtures with glycerol or ethylene glycol. Other effects suggest a competition in the formation of hydrogen bonds among the pure species (like molecular interactions) and the DES complexes (unlike molecular interactions). Overall, this work reports a systematic evaluation of H E for a series of representative DESs that elucidates the roles of HBD and HBA in the energy penalty required for DES formation, which is critical for assessing their potential in practical applications on an industrial scale.

Biobased organic acids constitute an important group of building block chemicals that can be produced from renewable resources, becoming a sustainable alternative to conventional petrochemical-derived commodities. However, due to the growing number of green solvents emerging as extraction media, the proper solvent selection for biomolecule separation from fermentation broths has become a key challenge in the biorefinery industry. The overall aim of this work is to develop a roadmap to select and design green solvents for sustainable downstream processing of biobased organic acids. To this end, a wide range of neoteric solvents (ionic liquids, eutectic solvents, and biobased solvents) were systematically evaluated for the recovery of relevant bio-organic acids through a combination of experimental and COSMO-RS (conductor-like screening model for real solvents) molecular simulation methods. Comprehensive thermodynamic analyses evaluating the organic acid partition coefficients, excess enthalpy contributions, solvent–water affinity, and process spontaneity were performed to elucidate the main mechanism driving the separation process and to provide essential guidelines for further solvent development. On the basis of these findings, a rational screening approach was established to identify suitable solvents for the recovery of structurally different bio-organic acids. Ultimately, this paper provides a green solvent selection guide to design sustainable separation processes for biobased organic acids to serve as valuable platform chemicals to transition toward a biobased economy.

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Membrane distillation (MD) is constantly acknowledged in the research literature as a promising technology for the future of desalination, with an increasing number of studies reported year after year. However, real MD applications still lag behind with only a few pilot-plant tests worldwide. The lack of technology transfer from academia to industry is caused by important gaps between its fundamental basis and the process design. Herein, we explore critical disconnections by conducting coupled mass and heat transfer modeling and MD simulations; we use well-known MD mass and heat transfer equations to model and simulate flux over a typical MD membrane for different geometries, areas, and operational conditions in direct contact configuration. From the analysis of the results, we propose research guidelines and process development strategies, and construct an MD module performance curve. From this graph, permeate flow rate, thermal energy consumption and outlet temperatures can be determined for given feed inlet conditions (temperature and concentration). Comprehensive tools such as this MD module curve and good communication between membrane developers and process engineers are required to accelerate the process of bringing the MD technology from a still-emerging status to a maturity level.