FTIR study of water clusters in water–triethylamine solutions

Unraveling the interplay of temperature with molecular aggregation and miscibility in TEA-water mixtures

In the phase diagram of binary liquid mixtures, a miscibility gap is found with the concomitant liquid-liquid phase separation, wherein temperature is a key parameter in modulating the phase behavior. This includes critical temperatures such as the lower critical solution temperature (LCST) and upper critical solution temperature (UCST). Using a comprehensive approach including molecular dynamics (MD) simulation, graph theoretical analysis and spatial inhomogeneity measurement in an LCST-type mixture, we attempt to establish the relationship between the molecular aggregation pattern and phase behavior in TEA-water mixtures. At lower temperatures of binary liquid mixtures, TEA molecules tend to aggregate while simultaneously interacting with water forming a homogeneous solution. As the temperature increases, these TEA aggregates tend to self-associate by minimizing the interaction with water, which facilitates formation of two distinct liquid phases in the binary liquid. The spatial distribution analysis also reveals that the TEA aggregates compatible with water promote uniform distribution of water molecules, maintaining a homogeneous solution, while the water-incompatible ones generate isolation of water H-bond aggregates, leading to liquid-liquid phase separation in the binary system. This current study on temperature-induced molecular aggregation behavior is anticipated to contribute to a critical understanding of the phase behavior in binary liquid mixtures, including UCST, LCST, and reentrant phase behavior.

Hydrogen Solubility in Confined Water

Confined water has demonstrated distinct structural and dynamic properties compared to bulk water. Although many studies have explored the water structure within simple geometries using materials such as carbon and silica, studies on gas solubility in confined water and the underlying physics of water structure-solubility remain limited. Recent research has illuminated the concept of "oversolubility", wherein gases display increased solubility within liquids confined in small pores compared to their bulk form. This study focuses on zeolites, naturally abundant materials with versatile applications, to study the hydrogen solubility within confined water through careful experimentation. Our findings underscore the relationship between the pore dimension and gas solubility enhancement within confined water. Hydrogen solubility is closely associated with the rearrangement of water molecules within the porous framework of the zeolite. Our research shows that a 2 nm pore size results in the greatest increase in hydrogen solubility in the water trapped inside the zeolite framework. The double donor-double acceptor (DDAA) bonds play a critical role in hydrogen solubility. Our research provides fundamental insight into the role of the molecular bonding type on hydrogen solubility in water, paving the way for potential applications in hydrogen storage and utilization.

Evolution of Transient Luminescent Assemblies Regulated by Trace Water in Organic Solvents

Trace water in organic solvents can play a crucial role in the construction of supramolecular assemblies, which has not gained enough attention until very recent years. Herein, we demonstrate that residual water in organic solvents plays a decisive role in the regulation of the evolution of assembled structures and their functionality. By adding Mg(ClO₄)₂ into a multi-component organic solution containing terpyridine-based ligand 3Tpy and monodentate imidazole-based ligand M2, the system underwent an unexpected kinetic evolution. Metallo-supramolecular polymers (MSP) formed first by the coordination of 3Tpy and Mg²⁺, but they subsequently decomposed due to the interference of M2, resulting in a transient MSP system. Further investigation revealed that this occurred because residual water in the solvent and M2 cooperatively coordinated with Mg²⁺. This allowed M2 to capture Mg²⁺ from MSP, which led to depolymerization. However, owing to the slow reaction between trace water/M2/Mg²⁺, the formation of MSP still occurred first. Therefore, water regulated both the thermodynamics and kinetics of the system and was the key factor for constructing the transient MSP. Fine-tuning the water content and other assembly motifs regulated the assembly evolution pathway, tuned the MSP lifetime, and made the luminescent color of the system undergo intriguing transition processes over time.

Under-oil superhydrophilic wetted PVDF electrospun modified membrane for continuous gravitational oil/water separation with outstanding flux

Water in the world is becoming an increasingly scarce commodity and the membrane technology is a most effective strategy to address this issue. However, the fouling and low flux of the polymeric membrane remains the big challenges. Novel modified Polyvinylidene fluoride (PVDF) membrane was introduced, in this work, using a novel treatment technique for an electrospun polymeric PVDF membrane to be used in oil/water separation systems. The Characterizations of the modified and pristine membranes showed distinct changes in the phase and crystal structure of the membrane material as well as the wettability. The modification process altered the surface morphology and structure of the membrane by forming hydrophilic microspheres on the membrane surface. Therefore, the proposed treatment converts the membrane from highly hydrophobic to be a superhydrophilic under-oil when wetted with water. Accordingly, in the separation of oil/water mixtures, the modified membrane can achieve an outstanding flux of 20664 L/m². hr under gravity, which is higher than the pristine membrane by infinite times. Moreover, in the separation of the emulsion, a high flux of 2727 L/m². h was achieved. The results exhibited that the modified membrane can treat a huge amount of oily water with a minimal energy consumption. The corresponding separation efficiencies of both of oil/water mixtures and emulsion are more than 99%. The achieved characteristics for the modified and pristine membranes could be exploited to design a novel continuous system for oil/water separation with an excellent efficiency.

A novel strategy for enhancing the electrospun PVDF support layer of thin-film composite forward osmosis membranes

A simple and novel treatment methodology is introduced to produce PVDF-based thin-film composite forward osmosis (TFC-FO) electrospun membranes for enhanced desalination performance.