Advanced Membranes最新文献

Both salt rejection and pressure-bearing properties of the conventional thin film composite (TFC) polyamide reverse osmosis (RO) membrane are easily weakened at high temperature. In order to improve the high temperature resistance, in this work, a polyamide TFC RO membrane with covalent organic frameworks (COFs) intermediate layer was prepared. Firstly, the COFs layer was decorated on polyether sulfone (PES) support membrane by a unidirectional diffusion method and further modified for shrinking the micropore via the chemical crosslinking reaction with 1,3-diamino-2-propanol (DAPL) or ethylenediamine (EDA), and then continued the conventional interfacial polymerization of m-phenylene diamine (MPD) and trimesoyl chloride (TMC) on the resultant COFs layer for preparing the RO membrane. Furthermore, the correlationship between the microstructure of COFs layer and the separation performance of modified RO membrane was systematically investigated. Due to the introduction of the COF_TpPa-DAPL intermediate layer with more regular microstructure and specific hydrophilicity, the resultant TFC-COF_TpPa-DAPL RO membrane exhibited improvement in water flux by 30 ​% (reached to 50.5 ​L ​m⁻² ​h⁻¹) and higher salt rejection (>99.5 ​%) as compared with the conventional polyamide RO membrane and other reported temperature resistance RO membranes. Meanwhile, this TFC-COF_TpPa-DAPL membrane showed good long-term separation stability during the RO process for 160 ​h. Especially, its water flux increased to 98.8 ​L ​m⁻² ​h⁻¹ without weakening salt rejection (about 99.4 ​%) at 70 ​°C. This study provides an effective way to fabricate the high temperature resistance TFC polyamide RO membrane with good comprehensive separation performance based on COFs intermediate layer.

The study provides an in-depth study on the gas adsorption and transport behaviors of MOF glass membranes for the first time. Temperature dependance of gas permeability, adsorption coefficients and diffusion coefficients between 298 ​K and 313 ​K for TIF-4 and ZIF-62 glass membrane were evaluated. The CO₂ permeability was dominated by the adsorption process, while CH₄ transport was mainly driven by the activated diffusion. Further, the MOF glass membranes exhibited significant entropic selectivity in adsorption, along with notable enthalpic selectivity in diffusion.

Emerging contaminants, including antibiotics, threaten water safety and public health. To remove these contaminants while retaining beneficial minerals in water, such as calcium (Ca), a novel thin-film composite nanofiltration (NF) membrane was manufactured through polymerization of a barrier layer composed of polypiperazine amide onto polyvinylidene fluoride (PVDF) hollow fiber (HF) substrate. The pore size of the PVDF surface was refined by introducing poly(vinylpyrrolidone) via a thermally induced phase separation method. Then piperazine (PIP) and trimesoyl chloride were selected to synthesize the NF membrane by interfacial polymerization with NaHCO₃ as an additive. The influence of PIP concentration on the membrane morphology and separation performance was investigated. The optimized HF NF membrane (NF3) exhibited high water permeability (8.08 ​L/(m² ​h ​bar)) due to its strong hydrophilicity. It also demonstrated a molecular weight cut-off of 378 ​Da and an enhanced negative surface charge (−43.96 ​mV), which was beneficial for the exclusion of antibiotics and passage of Ca²⁺. The high tetracycline rejection (98.9 ​%) enabled the NF3 membrane to achieve superior Ca²⁺/antibiotic selectivity (37.27) compared with most commercially available NF membranes. This study offers novel insights into tailoring the mineral/micropollutant selectivity of HF NF membranes for drinking water purification.

Developing energy-saving membrane and technology is important for the separation of hydrocarbon isomers to replace the energy-intensive distillation. Silicalite-1 membrane is a promising membrane material but difficult to be scaled up. In this work, separation performance of industrial-scale monolithic silicalite-1 membranes in term of actual butane mixtures has been reported for the first time. Each 61-channel monolithic membrane has effective area and surface-to-volume ratio of 0.2 ​m² and 400 ​m²/m³, which are about 20 and 5.6 times higher than that of the common tubular one with the same length, respectively. Average n-butane/i-butane separation factor (34) of the industrial-scale membranes was even higher than or comparable to that of the reported small-area zeolite membranes. The influences of test parameters on permeances and separation factors of the membranes and the long-term stability were examined. Reynold numbers was used to correlate the concentration polarization (CP) with the reduction of separation performance. A solution was proposed to reduce the effect of CP. It suggests that the industrial-scale and high-performance monolithic silicalite-1 membranes are suitable for actual applications of butane separation.

Membrane technology holds immense potential across multiple industries, offering sustainable solutions for challenging separations by reducing energy demand and transitioning from thermal to electrical energy. The inherent diversity of membrane technology results in various transport scenarios and phenomena, rendering robust process evaluation and optimization challenging. Addressing this problem, we formulate the cascading selectivity principle (CSP), a universal concept applicable across all membrane separation types, including gas, liquid, and particle filtration. Introducing a distinction between primary and secondary permselectivity, the CSP provides a theoretical basis for novel efficiency indices. We also present the first highly versatile selectivity merit descriptors for true membrane cross-comparison. We demonstrate the advantages of the novel descriptors through a series of real-life nanofiltration, ion separation, gas separation, membrane reactor, and ultrafiltration examples. Facilitated by an online calculator tool, this work offers a standardized framework for academic and industrial professionals to implement pioneering membrane separation systems efficiently across the multiple disciplines of membrane technology.

Metal-organic framework (MOF)-based mixed matrix membranes (MMMs) have attracted significant attentions for their distinguished characteristics in pervaporation such as enhanced selectivity, increased permeability and improved mechanical strength through the synergistic integration of polymeric matrices and inorganic fillers. Although many publications have emerged in recent years focusing on MOF-based MMMs, this review specifically emphasizes the improvement of MOF-based pervaporation membranes through the design of dimension of fillers and microstructure. The challenges encountered in MOF-based MMMs for pervaporation and the essential requirements for practical separation applications are addressed. A brief summary of strategies is provided for designing MOF-based MMMs with desired microstructure, macrostructure and multicomponent characteristics by using MOFs as fillers. The latest progresses in novel MOF-based MMMs with specific compositions, controllable pore structure and improved compatibility for recovery of organics are also displayed. The broad application prospects of MOF-based MMMs in pervaporation are introduced, including recovery of ethyl alcohol, butanol and other organics. Moreover, the challenges faced in the practical application of MOF-based MMMs for recovery of organics are presented and the promising future directions are outlined.

Hemodialysis acts as an artificial kidney that selectively removes specific toxins, bio-compounds, or fluid from the main blood stream in a patient with kidney failure. The current process uses ultrafiltration-based membrane technology, where a semi-permeable material selectively extracts chemicals, such as uremic retention products, or remove excess water from blood by retaining certain compounds based on their size. As sugars, fats, proteins, biomolecules, cells, and platelets move into and across the tubular membrane in the hemodialysis process, the surface of the membrane begins to foul, which leads to major operational challenges that include sharp pressure drops with increasing operation times. The design of membranes with enhanced biocompatibility and anti-fouling properties is one avenue to increase the lifespan of the membrane used while facilitating the device operation and limiting the stress and discomfort of patients. This review presents interfacial interactions between blood components and membrane materials used in hemodialysis. The discussion analyzes the impacts of the hemodialyzer module design, membrane material morphology and surface chemistry on the long-term operation and performance of the hemodialyzers. Avenues for the development of next-generation-membrane-materials as well as new strategies to enhance the selective removal of toxic compounds from blood are also discussed.