1,2-bis(triethoxysilyl)methane (BTESM) is a bridged-type organoalkoxysilane, which was utilized for organic–inorganic membranes preparation via a sol–gel method to achieve high permselectivity, thus are promising for dehydration and purification of organic solvents. However, the particle size of the derived sol is crucial for membrane preparation during sol–gel processing, significantly influencing the membrane’s performance. Herein, we reported a novel strategy of controlling the sol particle size by adjusting the pH during the preparation process. BTESM-derived membranes were prepared by BTESM-H + sol and BTESM-swing sol, which were subsequently employed for the dehydration of isopropanol (IPA) through pervaporation (PV). Compared with the BTESM-H + sol, the particle size of the BTESM-swing sol prepared by the pH-swing method was increased from 1.3 nm to 32.7 nm. The larger particle size could hinder the permeation into the intermediate layer. Meanwhile, the dense arrangement of silica particles could efficiently retain IPA molecules, thereby substantially enhancing the rejection rate of IPA. The average particle size of the BTESM-swing sol was 18.7 nm at an acid-base ratio of 1.2 and acid-silicon ratio of 0.55, resulting a permeate flux of 1.04 kg·m −2 ·h −1 and separation factor of 521, while IPA rejection rate was 97.84 %. This work has shown that adjusting the pH during the process is a useful strategy of controlling the sol size for the preparation of organic–inorganic membranes. Hence, the control of sol particle size to achieve a high-performing membrane layer offers a novel approach to producing diverse membrane materials.
Inorganic membranes are prime candidates for organic solvent recovery in the pharmaceutical industry due to their excellent solvent resistance, mechanical strength and durability. However, constructing high-performance inorganic separation layers is still the most challenging aspect in the fabrication of inorganic membranes for organic solvent nanofiltration (OSN). Prussian blue analogues (PBAs) exhibit high chemical stability for their rigid cubic framework with strong covalent metal-cyanide coordination bonds. Inspired by the interfacial polymerization (IP) strategy, this study proposes a simple synthesis method for prussian blue analog thin films (PBA TFs) on porous ceramic substrates, using coordination reactions between K 3 [Fe(CN) 6 ] and acetylacetonate (e.g. Cu(acac) 2 , Mn(acac) 3 or Co(acac) 2 ). The Mn-Fe PBA membrane exhibits high solvent permeance (e.g., 176.4 L·m −2 ·h −1 ·bar −1 for ethyl acetate) and demonstrates a molecular weight cut-off ranging from 665 to 760 Da across six tested solvents. To evaluate the industrial potential of Mn-Fe PBA membranes, solvent recovery experiments were conducted in a twin-stage OSN system using seven active pharmaceutical ingredient (API)/solvent systems. In the tylosin/dimethyl sulfoxide system, the Mn-Fe PBA membrane achieved over 80 % total API retention, maintaining stable performance across multiple cycles. The formation process of PBA TFs was analyzed by adjusting monomer diffusion conditions. Furthermore, molecular dynamics simulations elucidated the film formation mechanism. The self-limiting nature of the IP strategy not only inhibits the formation of PBA large crystals, but also induces the self-assembly of PBA nanocrystals along the n-hexane/water interface, resulting in a complete PBA TF. This IP strategy blazes a new trail for fabrication of high-performance inorganic OSN membranes.
A flexible SiO2 porous fiber membrane (SF) is prepared by electrospinning followed by calcination in this work. Compared with an organic substrate separator, the SF used as a separator will be an absolute guarantee of the battery thermal safety. The porosity of the SF is 88.6%, which is more than twice that of a regular PP separator. Hydrophilic SF shows better electrolyte wetting ability and its high porosity enables the SF to absorb 633% liquid electrolyte on average, while the lithium-ion conductivity reaches 1.53 mS cm−1. The linear sweep voltammogram testing of PP and SF suggested that SF, with great electrochemical stability, can meet the requirements of lithium-ion batteries. The cyclic and rate performances of batteries prepared with SF are improved significantly. Such advantages of the SF, together with its potential in mass production, make the SF a promising membrane for practical applications in secondary lithium-ion batteries.
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