Fabrication and Characterization of Carbon Nanotube Filled PDMS Hybrid Membranes for Enhanced Ethanol Recovery

Incorporating Mixed-Ligand Zeolitic Imidazolate Framework into Polydimethyldiethoxysilane (PDMDES) Membrane for Enhancing Alcohol Pervaporation Recovery

In the present study, a zeolitic imidazolate framework with mixed ligands, ZIF-8-90, was synthesized and embedded into an ultrathin polydimethyldiethoxysilane (PDMDES) matrix to prepare a ZIF-8-90/PDMDES mixed matrix membrane (MMM) for the enhanced recovery of alcohols from dilute aqueous solutions via pervaporation, using a facile solution coating method. The synthesized ZIF-8-90 particles demonstrated superior hydrophobicity and thermal stability compared to those of both ZIF-8 and ZIF-90 particles. Furthermore, the hydrophobicity, thermal stability, and sorption ability for alcohols of the ZIF-8-90/PDMDES MMM were significantly improved, attributed to the incorporation of mixed-ligand ZIF-8-90. Notably, the MMMs displayed two distinct cross-sectional morphologies: (1) ZIF-8-90 particles enveloped by PDMDES polymer forming filler bulges and (2) an accumulation of ZIF-8-90 particles resembling a brick-wall-like structure. The MMM incorporating 2.5 wt % ZIF-8-90 exhibited the optimal performance among the fabricated MMMs with various ZIF-8-90 loadings, spanning from 0 to 3.2 wt %. The effects of feed concentrations and operation temperatures were systematically investigated. The best pervaporation performance was achieved using the 2.5 wt % ZIF-8-90-filled MMM, effectively separating a 5.0 wt % ethanol/water mixture at 60 °C, yielding a distinguished total flux of 7.70 kg·m-2·h-1, an improved separation factor of 9.96, and an extraordinarily high PSI of 68.99 kg·m-2·h-1. Comparative analyses highlighted the superior pervaporation performance of the ZIF-8-90/PDMDES MMM over ZIF-8/PDMDES MMM, ZIF-90/PDMDES MMM, and other MMMs, underscoring its potential for practical applications in alcohol recovery.

Ultra-small gold nanoparticles embedded cyclodextrin metal-organic framework composite membrane to achieve antibacterial and humidity-responsive functions

Cyclodextrin metal-organic framework (CD-MOF) is an edible and porous material that can serve as a template for synthesizing small-sized metal nanoparticles. However, its highly hydrophilic nature has limited its wider application. Herein, ultra-small gold nanoparticles (U-AuNPs) were loaded into CD-MOF to produce a composite material Au@CD-MOF. The CD-MOF was utilized as a template to control the size of the AuNPs. The synthesized Au@CD-MOF was easily dispersible in aqueous medium and its released U-AuNPs exhibited effective water dispersion stability within 120 days. Additionally, compared to gold nanoparticles prepared using traditional methods (T-AuNPs), the U-AuNPs exhibited superior antibacterial properties. Furthermore, hydrophilic Au@CD-MOF was incorporated into a hydrophobic polydimethylsiloxane (PDMS) matrix (Au@CD-MOF/PDMS) to achieve a humidity-responsive antibacterial function. The composite membrane exhibited remarkable responsiveness to humidity, showing almost no release of U-AuNPs at 0 % humidity. However, it exhibited approximately 89 % release within 1 h, and complete release of U-AuNPs was observed within 4 h under 100 % humidity. These findings highlight the successful preparation of a humidity-responsive antibacterial composite membrane, which has great potential applications in various scenarios, particularly in the field of antibacterial food packaging.

Sandwich-Type Self-Healing Sensor with Multilevel for Motion Detection

Real-time detection of various parts of the human body is crucial in medical monitoring and human-machine technology. However, existing self-healing flexible sensing materials are limited in real-life applications due to the weak stability of conductive networks and difficulty in balancing stretchability and self-healing properties. Therefore, the development of wearable flexible sensors with high sensitivity and fast response with self-healing properties is of great interest. In this paper, a novel multilevel self-healing polydimethylsiloxane (PDMS) material is proposed for enhanced sensing capabilities. The PDMS was designed to have multiple bonding mechanisms including hydrogen bonding, coordination bonding, disulfide bonding, and local covalent bonding. To further enhance its sensing properties, modified carbon nanotubes (CNTs) were embedded within the PDMS matrix using a solvent etching technique. This created a sandwich-type sensing material with improved stability and sensitivity. This self-healing flexible sensing material (self-healing efficiency = 70.1% at 80 °C and 6 h) has good mechanical properties (stretchability ≈413%, tensile strength ≈0.69 MPa), thermal conductivity, and electrical conductivity. It has ultrahigh sensitivity, which makes it possible to be manufactured as a multifunctional flexible sensor.

Surface-modified silicalite-1-filled PDMS membranes for pervaporation dehydration of trichloroethylene

In this study, the impact of silane coupling agents, namely 3-aminopropyltrimethoxysilane (APTMS), trimethylchlorosilane (TMCS), and 1,1,3,3-tetramethyldisilazane (TMDS), on the hydrophobicity of silicalite-1 zeolite was investigated to enhance the pervaporation separation performance of mixed matrix membranes (MMMs) for trichloroethylene (TCE). The hydrophobicity of TMCS@silicalite-1 and TMDS@silicalite-1 particles exhibited significant improvement, as evidenced by the increase in water contact angle from 96.1° to 101.9° and 109.1°, respectively. Conversely, the water contact angle of APTMS@silicalite-1 particles decreased to 85.2°. Silane-modified silicalite-1 particles were incorporated into polydimethylsiloxane (PDMS) to prepare mixed matrix membranes (MMMs), resulting in a significant enhancement in the adsorption selectivity of trichloroethylene (TCE) on membranes containing TMCS@silicalite-1 and TMDS@silicalite-1 particles. The experimental findings demonstrated that the PDMS membrane with a TMDS@silicalite-1 particle loading of 40 wt% exhibited the most favorable pervaporation performance. Under the conditions of a temperature of 30 °C, a flow rate of 100 mL min-1, and a vacuum degree of 30 kPa, the separation factor and total flux of a 3 × 10-7 wt% TCE aqueous solution were found to be 139 and 242 g m-2 h-1, respectively. In comparison to the unmodified silicalite-1/PDMS, the separation factor exhibited a 44% increase, while the TCE flux increased by 16%. Similarly, when compared to the pure PDMS membrane, the separation factor showed an 83% increase, and the TCE flux increased by 20%. These findings provide evidence that the hydrophobic modification of inorganic fillers can significantly enhance the separation performance of PDMS membranes for TCE.