Journal of Membrane Science最新文献

The management of hypersaline brine is a critical challenge to achieving a circular water economy. Traditional brine treatment technologies mainly rely on thermal evaporation, which requires intensive energy, cost, and/or areal footprint. Electrodialytic crystallization (EDC) has been recently developed as a novel process that enables brine crystallization without evaporation. However, the potential effects of mineral scaling and organic fouling on the performance of EDC have not been revealed. In this study, we systematically investigated mineral scaling and organic fouling in EDC. We demonstrate that the ion transport and crystallization efficiencies of EDC are generally unaffected by a variety of mineral scalants and organic foulants, despite an increase of energy consumption in the presence of humic acid. Further, EDC is shown to be less susceptible to gypsum scaling than RO, mainly due to the difference in concentration polarization between these two membrane processes. To mitigate gypsum scaling in an assumptive EDC-RO treatment train towards zero liquid discharge (ZLD), polyacrylic acid (PAA) is employed as an antiscalant that prevents gypsum scaling in RO while not adversely affecting EDC performance at relatively low concentration. Our study unravels the behaviors of EDC when treating feedwater with high scaling and fouling potentials, providing valuable insights for understanding mineral scaling and organic fouling when applying an ED-based technology for hypersaline brine treatment towards ZLD.

Metal organic framework (MOF)-polymer composite solid electrolyte membrane with novel microstructure is expected to show attractive prospect for solid state lithium metal batteries. But the reported MOF were usually regarded as an entirety in composite solid electrolyte resulting in tradeoff between ionic conductivity and lithium dendrite inhibition ability. Herein, MOF-polymer composite membrane with vertically aligned channels and ultrathin MOF layer is proposed to decrease lithium ion transportation resistance obtained by simple phase inversion and in situ coordinated growth methods. The vertically aligned highways can decrease tortuous pathways and intensify ion conduction. The embedded ultrathin MOF layer on membrane surface leads to homogeneous plating/stripping of lithium. This novel structured MOF-polymer composite solid electrolyte exhibits improved ionic conductivity of 0.55 mS cm⁻¹ at 22 ° C and lithium ion transference number of 0.87. Furthermore, the Li/Li symmetrical cell shows stable lithium plating/stripping performance for 1100 h at 0.1 mA cm⁻² and 0.1 mA h cm⁻². LiFePO₄/MOF-polymer/Li coin battery demonstrates good rate capability and cycling performance with capacity retention of 82 % after 100 cycles at 0.2C and the pouch cell can light up the “DLUT” blue light lamp under folding and cutting states. This work encourages a new avenue to develop composite solid electrolytes with ion transportation highways and uniform distribution plane for solid lithium metal batteries.

There is an increasing demand for advanced membranes that exhibit both high perm-selectivity and good stability in organic solvents, particularly for organic solvent nanofiltration (OSN). Traditional methods of synthesizing thin films using conventional interfacial polymerization (CIP) have been limited by the use of water-soluble monomers, which has hindered the development of high-performance membranes. To address this issue, a new method called organic-organic interfacial polymerization (OOIP) has been proposed. This method allows for the use of aromatic amines that are not water-soluble in the fabrication of ultrathin polyamide (PA) (<40 nm) thin film composite (TFC) membranes. By investigating five different organic solvents (tetrahydrofuran, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide) with varying water content as the organic phase for a water-insoluble benzidine monomer, two diffusion models of monomers were identified that resulted in different membrane structures and degrees of network crosslinking. The ultrathin PA membranes produced using tetrahydrofuran-H₂O and N,N-dimethylformamide-H₂O, along with solvent activation, demonstrated high methanol permeances of 11.4 L m⁻² h⁻¹ bar⁻¹ and 6.0 L m⁻² h⁻¹ bar⁻¹, respectively, while maintaining exceptional rejections of over 99.0 % for small molecules with molecular weights greater than 452 g mol⁻¹. The OOIP method is scalable and reproducible, making it suitable for large-scale membrane production. This innovative approach shows great potential for advancing OSN technology and providing efficient and cost-effective separation solutions for various industries.

The rare earth metal neodymium (Nd) is widely used in advanced industries such as hybrid cars and aerospace. Therefore, recovering neodymium from wastewater presents valuable opportunities for secondary recycling. The recovery of Nd³⁺ from wastewater using ion imprinting technology (IIT) for efficient selective separation holds significant importance. In this study, hydrophilic Nd(III) ion-imprinted membranes, termed Nd(III)–P/P/TIIM, were synthesized using the IIT technique. Nd(III)–P/P/TIIM exhibited efficient and selective separation capabilities for Nd³⁺ with a remarkable retention rate of 95.68 % and a high water flux reaching up to 636.94 L·m⁻²·h⁻¹. Additionally, its relative selectivity coefficients for interfering ions ($K_{\text{La}}$, $K_{\text{Eu}}$, $K_{\text{Cu}}$) were 3.9, 29.5, and 37.9, respectively. Various analyses, including DFT calculations, HOMO and LUMO calculations, MEP images, and XPS spectroscopy, confirm that the mechanism of selective retention of Nd³⁺ by Nd(III)–P/P/TIIM in solution is due to Coulombic adsorption between the –COO⁻ anion and Nd³⁺ as well as an imprint memory effect. Even after undergoing three water-BSA cycles, the membrane maintained a water flux of 357.96 L·m⁻²·h⁻¹. The antifouling principle of Nd(III)–P/P/TIIM was investigated by XDLVO theory, attributed to the increase of electron donor tension (γ⁻) and Lewis acid-base interactions (${\Delta G}^{\text{AB}}$) at the membrane surface. This work provides an insightful guidance for engineering high-performance membranes and has the potential to provide an alternative method for recycling neodymium.

Preferred orientation control represents a crucial step for performance enhancement of MOF membranes. Nevertheless, their sustainable preparation remains a significant challenge. In this work, we fabricated highly (110)-oriented ZIF-8 membranes through supercritical fluid (SCF)-assisted epitaxial growth of oriented seed layer. Benefiting from unique physicochemical properties and intrinsic chemical inertness of supercritical CO₂, preferential orientation originated from the seed layer could be well maintained during epitaxial SCF processing; moreover, both unreacted ligands and discharged CO₂ could be efficiently recovered, resulting in zero pollutant emission. Our ZIF-8 membrane exhibited ideal C₃H₆/C₃H₈ selectivity of 91.8. To the best of our knowledge, this represented the first report of the preparation of highly oriented ZIF-8 membrane with such high C₃H₆/C₃H₈ selectivity; more importantly, our study demonstrated that SCF processing represented an effective protocol for orientation modulation of MOF membranes towards superior separations.

In recent years, advancements in anion exchange membranes (AEMs) have notably enhanced the overall performance of anion exchange membrane fuel cells (AEMFCs). However, issues like limited alkali stability and low ionic conductivity of AEMs have become apparent. In this study, focusing on molecular design, a series of polycarbazole-based AEMs with flexible side chains, named PCP-n (where ‘n’ denotes the molar ratio of the newly synthesized monomer BHC in carbazole derivatives), were developed. The integration of long flexible side chains fosters chain movement and the clustering of piperidine cations, leading to distinct hydrophilic/hydrophobic nanoscale phase separation within the PCP-n membranes. Moreover, the PCP-n membranes demonstrate effective water management capabilities, with the PCP-90 membrane displaying a 32 % water uptake and an in-plane swelling ratio below 20 % at 80 °C. The introduction of an ether-free main chain based on carbazole derivatives along with the highly stable piperidine cationic group endows the PCP-n membranes with exceptional alkali resistance. Following a 1500-h immersion in 2 M KOH at 80 °C, the PCP-90 membrane successfully retains 79.92 % of its original ionic conductivity. Given its substantial thermal stability and mechanical strength, the PCP-90 membrane underwent testing in membrane electrode assembly and single-cell performance, achieving a notable peak power density of 275.64 mW cm⁻² and an open-circuit voltage of 0.98 V. Overall, the impressive comprehensive performance of the PCP-n membranes suggests a promising future for their application.

Membrane fouling has been a major factor hindering the development of ultrafiltration membranes. Herein, a novel in situ oxidation system was constructed via introducing MnFe₂O₄/MWCNTs into polyvinylidene fluoride (PVDF) membranes, utilizing sunlight to synergistically activate persulfate (PMS) to mitigate ultrafiltration membrane fouling. The mechanism of mitigating membrane fouling in MnFe₂O₄/MWCNTs-PVDF ultrafiltration membranes was systematically explored under four system (single filtration, single sunlight irradiation, single PMS oxidation and sunlight co-activated PMS). The MnFe₂O₄/MWCNTs-PVDF membranes exhibited different fouling characteristics under the four systems, with the sunlight and MnFe₂O₄/MWCNTs membrane co-activated PMS filtration system showing the highest humic acid (HA) removal efficiency of 90.2 %, as well as the lowest Rr (0.2108 × 10¹²m⁻¹) and Rir (0.4525 × 10¹²m⁻¹). To further evaluate the practicality and effectiveness of the sunlight-MnFe₂O₄/MWCNTs-PMS system, the secondary effluent was selected to verify the treatment effect on natural organic matter (NOM) of actual water. By observing the microscopic morphology of the fouled membrane surface, it was evident that, compared with the other three filtration systems, the filter cake layer on the MnFe₂O₄/MWCNTs membrane surface of the sunlight co-activated PMS system was obviously reduced, and the structure of the cake layer was more loose. It can be concluded that the principle behind the synergistically activated system to alleviate the membrane fouling was to accelerate the mineralization rate of HA molecules, oxidize the HA into a smaller particle size that can pass through the membrane pores. The main reactive oxygen species and HA degradation mechanism in the synergistic activation system were further elucidated by electron paramagnetic resonance (EPR) analysis and density functional theory calculations (DFT). The results indicated that the degradation of HA by the synergistically activated PMS system involved a combination of free radicals (·O₂⁻、SO₄^·− and ·OH) and non-free radicals (¹O₂). Overall, the in-situ oxidation system provided an alternative way to alleviate ultrafiltration membrane fouling.

Low flux and membrane fouling are major challenges in membrane distillation (MD) for treating concentrated wastewater. This study compared the performance of GO composite membranes with different interlayer distances, by covalently bonding the terminal amine groups of ethylenediamine (EDA) and 1,12-diaminododecane (DADD) with the carboxyl groups present on the GO sheets. The results indicated that the GO-DADD/PTFE membrane, with longer carbon chain cross-linking, achieved the highest flux and antifouling properties. At 70 °C, the pure water flux reached 68.5 kg/m²·h, and the fluxes for treating NaCl, HA containing NaCl, and BSA containing NaCl were 29.8 %, 37.1 %, and 38.5 % higher than the uncrosslinked GO/PTFE, and 95.7 %, 121.2 %, and 146.9 % higher than the PTFE membrane, respectively. Through mathematical models for mass and heat transfer, the study identified the key to this enhancement as the increased d-spacing within the GO layer due to cross-linking, which weakened the Kelvin effect and enhanced the vapor partial pressure on the hot side. The unique surface structure and electrostatic interactions induced by long-chain cross-linking further boosted the antifouling effect. These modifications not only overcome the typical trade-off between retention rates and flux but also offer a scalable and efficient solution for advanced membrane distillation applications.

In this study, we explore the role of the polysulfone (PSU) support membrane skin-layer and whole-body pore morphology on the physical-chemical properties and separation performance of hand-cast polyamide-PSU (PA-PSU) composite seawater reverse osmosis (SWRO) membranes. We tailor the support membrane pore morphology by varying the PSU concentration and the coagulation bath temperature. In order to isolate the impacts of the PSU support, all of the porous supports are coated using identical m-phenylene diamine (MPD) and trimesoyl chloride (TMC) solution compositions, reaction conditions, and post-treatments. As PSU concentration increases, PSU support membrane pore size, surface and body porosity, water permeability, MPD mass uptake (by the PSU support), and PA-PSU composite membrane water permeability decrease, while MPD and TMC conversion, PA film mass and thickness, crosslinking degree (XD), and PA-PSU composite membrane NaCl rejection increase. As PSU support membrane coagulation bath temperature increases, support membrane pore size, surface and body porosity, MPD uptake, PA film mass, thickness and XD, MPD and TMC conversion, and NaCl rejection increase, while composite PA-PSU membrane water and NaCl permeability decrease. Composite membrane permeabilities were 70–90 percent of the (theoretical) unsupported PA film permeabilities due to the high XD and low PA coating film thickness. Composite PA-PSU membrane water/salt permeabilities both correlate most strongly with PA coating film mass/thickness and XD, which in turn correlate most strongly with TMC conversion. The key to increasing water permeability is lower PA film mass/thickness and XD with higher support membrane surface pore size and porosity. In contrast, the key to increasing NaCl rejection is higher PA film mass/thickness and XD with lower support membrane surface pore size and porosity.

Ultrafiltration membranes have significant potential for application in wastewater treatment. However, membrane fouling seriously affects the separation efficiency and service life of the membrane. The preparation of conductive membranes offers a novel idea for removing membrane fouling. In this work, polyethersulfone (PES) mixed matrix membranes containing epigallocatechin gallate-modified multi-walled carbon nanotubes and silanized MXene were simply prepared by nonsolvent-induced phase inversion. Due to the introduction of a three-dimensional network structure electrostatically assembled with the two nanomaterials, the membranes have a great potential for balancing permeability, separating ability, and electrical conductivity. In addition, due to the presence of two kinds of fillers, the modified membrane also showed excellent electrical conductivity and antimicrobial performance, with a conductivity of up to 6.4 mS/cm, while exhibiting an ultra-high bacterial inhibition rate of close to 100 %. More importantly, through electrochemically assisted cleaning, the membrane fouling was efficaciously removed by nanobubbles and electrostatic force, and the flux recoveries after membrane filtration of CR and BSA reached 93.1 % and 91.7 %, respectively. In summary, the composite membrane has lots of promise for use in the purification of wastewater due to its considerable pollution removal effect and long-term operational performance.