Water Transport Pathways Research Articles

Water exchange and transport pathways in estuary-shelf region of Pearl River Estuary under multiple forcings

Using the Pearl River Estuary (PRE) as an example, the exposure time (θ‾) was calculated to investigate the dominant processes of three-dimensional water exchanges in the estuarine-shelf system and explore the underlying transport pathway. The θ‾, which quantifies the time of water stayed in a defined region, shows clear seasonality under the joint controls from river discharge, tides and wind forcing. It has the lowest domain-average value (∼6 days) in the early summer, then along with weakening of river discharge, it increases to the peak (∼13 days) at the beginning of the fall and remains relatively high during following fall and winter. In contrast, the vertical difference of θ‾ in the water column shows the opposite temporal variability. Spatially, θ‾ increased from the lower to the upper estuary, and in response to the gravitational circulation of surface seaward transport and the bottom intrusion, a larger θ‾ appeared in the bottom layer of water column. Numerical experiments show river discharge predominantly determined the θ‾ compared to the modulation from tides and wind. Based on the water exchange timescale in different subdomains, the transport pathway inside the estuary is controlled by river discharge and tides, which impose a net effect on weakening onshore transport. Outsides the estuary, the wind-driven shelf current modulates the remote influences from the regions far away from the PRE. The spatial structure and temporal variabilities of water exchange identified in this study help to utilize the water exchange capability and realize substance renewal in estuary-shelf regions.

Coordination of hydraulic and leaf-level gas exchange traits during water-deficit acclimation in apple rootstocks.

Water deficit episodes impact apple (Malus domestica) productivity through challenging the trees' water status, the influence of extreme high temperature climate has become increasingly prominent in recent years. Rootstocks can bestow specific properties on the fruit trees such as the resistance to drought stress. However, the related hydraulic mechanisms in response to water deficit have not been fully understood. Herein, five rootstocks (SH6, GM256, M9, M26, and MM106) were examined under water limitation. The hydraulic conductance of root (Kroot), shoots (Kshoot), and stems (Kstem-shoot) in the five rootstocks reduced slightly during drought stress. Whereas the leaf water potential and photosynthesis of five rootstocks decreased dramatically when they were exposed to drought stress. Additionally, the Kshoot and Kstem-shoot were strongly correlated with the total plant leaf area. Aquaporins (AQPs) involved in the symplastic water transport pathway, the PIP2:1, TIP1:1, and TIP2:2 mRNA levels of all genotypic rootstocks showed significant regulation under drought stress. We examined the relationships among photosynthesis, apoplastic, and symplastic water movement pathways to achieve a comprehensive understanding of rootstocks' hydraulic strategy for improving drought adaptation. The PIP2:1 and TIP2:1 in leaves were more sensitive to root hydraulic conductance in response to drought stress. Furthermore, the coordinated relationship existed in leaf-specific conductance of shoot (Kl -shoot) and transpiration rate (Tr) under drought stress in the rootstocks. Overall, the drought resistance in the five dwarfing rootstocks is associated with the rapid re-establishment of water-related traits, and the effect of the canopy on the drought resistance in apple rootstocks merits much more attention.

Buoyancy forcing: a key driver of northern North Atlantic sea surface temperature variability across multiple timescales

Abstract. Analyses of observational data (from year 1870 AD) show that sea surface temperature (SST) anomalies along the pathway of Atlantic Water transport in the North Atlantic, the Norwegian Sea and the Iceland Sea are spatially coherent at multidecadal timescales. Spatially coherent SST anomalies are also observed over hundreds of thousands of years during parts of the Pliocene (5.23–5.03, 4.63–4.43, and 4.33–4.03 Ma). However, when investigating CMIP6 (Coupled Model Intercomparison Project 6) SSP126 (Shared Socioeconomic Pathway) future scenario runs (next century) and other Pliocene time intervals, the following three additional SST relations emerge: (1) the Norwegian Sea SST anomaly is dissimilar to the North Atlantic and the Iceland Sea SST anomalies (Pliocene; 4.93–4.73 and 3.93–3.63 Ma), (2) the Iceland Sea SST anomaly is dissimilar to the North Atlantic and the Norwegian Sea SST anomalies (Pliocene; 3.43–3.23 Ma), and (3) the North Atlantic SST anomaly is dissimilar to the SST anomalies of the Norwegian and Iceland seas (future trend). Hence, spatially non-coherent SST anomalies may occur in equilibrium climates (Pliocene), as well as in response to transient forcing (CMIP6 SSP126 low-emission future scenario). Since buoyancy is a key forcing for the inflow of Atlantic Water to the Norwegian Sea, we investigate the impacts of buoyancy forcing on spatial relations between SST anomalies seen in the North Atlantic and the Norwegian and Iceland seas. This is done by performing a range of idealized experiments using the Massachusetts Institute of Technology general circulation model (MITgcm). Through these idealized experiments we can reproduce three out of four of the documented SST anomaly relations: being spatially coherent under weak to intermediate freshwater forcing over the Nordic Seas, the Iceland Sea being dissimilar to the North Atlantic and the Norwegian Sea under weak atmospheric warming over the Nordic Seas, and the North Atlantic being dissimilar to the Norwegian and Iceland seas under strong atmospheric warming over the Nordic Seas. We suggest that the unexplained SST anomaly relation, when the Norwegian Sea is dissimilar to the North Atlantic and the Iceland Sea, may reflect a response to a weakened Norwegian Atlantic Current compensated for by a strong Irminger Current or an expanded East Greenland Current.

Pore-Scale Modeling of Liquid Water Transport in Compressed Gas Diffusion Layer of Proton Exchange Membrane Fuel Cells Considering Fiber Anisotropy.

Water management of the gas diffusion layer (GDL) is crucial to the performance of proton exchange membrane fuel cells (PEMFCs). Appropriate water management ensures efficient transport of reactive gases and maintains wetting of the proton exchange membrane to enhance proton conduction. In this paper, a two-dimensional pseudo-potential multiphase lattice Boltzmann model is developed to study liquid water transport within the GDL. Liquid water transport from the GDL to the gas channel is the focus, and the effect of fiber anisotropy and compression on water management is evaluated. The results show that the fiber distribution approximately perpendicular to the rib reduces liquid water saturation within the GDL. Compression significantly changes the microstructure of the GDL under the ribs, which facilitates the formation of liquid water transport pathways under the gas channel, and the increase in the compression ratio leads to a decrease in liquid water saturation. The performed microstructure analysis and the pore-scale two-phase behavior simulation study comprise a promising technique for optimizing liquid water transport within the GDL.

Characteristics of the soil macropore and root architecture of alpine meadows during the seasonal freezing-thawing process and their impact on water transport in the Qinghai Lake watershed, northeastern Qinghai–Tibet Plateau

Low temperatures, freezing-thawing cycles, and short growing seasons characterize alpine soils. The mattic epipedon, a special diagnostic surface horizon with an intensive root network, is widely distributed in alpine ecosystems. Studies on the soil macropores and roots of the mattic epipedon layer in response to seasonal freezing-thawing processes on the Qinghai–Tibet Plateau are lacking. This study characterized the soil macropores and roots of alpine meadows during the seasonal freezing-thawing process using X-ray computed tomography and revealed the influence of soil macropores and roots structure on water transport in the mattic epipedon layer of the alpine meadows. The results showed that the soil pore distribution was more uniform during the unstable freezing stage (UFP) and the unstable thawing stage (UTP), whereas there was a clear mattic epipedon layer during the completely thawed stage (TP) and the completely frozen stage (FP). Soils in the TP stage had a higher total surface area density (0.1898 mm² mm⁻³), length density (225.28 mm mm⁻³), node density (1,592 no. mm⁻³), and connectivity (0.3144) of soil macropores than those in the UFP, UTP, and FP stages. In the TP stages, the density, surface area density, branch density, length density, and node density of roots had significant correlations with the macroporosity, surface area density, length density, node density, and tortuosity of soil macropores. In the FP stage, there were no correlations between the root and soil macropore characteristics. Vertical water is expected to move more readily through the mattic epipedon in the TP stage than in the UFP and UTP stages. Roots were the preferential pathways for water transport into the soil layer of the alpine meadow. Therefore, the mattic epipedon is a key layer for water and nutrient storage and plays an important role in the water-holding function of the Tibetan Plateau due to its greater root development.

The difference in the functional water flow network between the stem and current-year root cross-sectional surfaces in Salix gracilistyla stem xylem.

The dye injection method has been applied to many species to analyze the xylem water transport pathway in trees. However, traditional dye injection methods introduced dye tracers from the surface of cut stems, including several annual rings. Furthermore, the traditional dye injection method did not evaluate radial water movement from the outermost annual rings to the inner annual rings. In this study, we assessed the difference in radial water movement visualized by an injected dye, between stem base cut and current-year root cut samples of Salix gracilistyla Miq., with current-year roots grown hydroponically. The results showed that the number of stained annual rings in the root cut samples was smaller than that in the stem cut samples, and the percentage of stained vessels in the root cut samples was significantly smaller than that in the stem base cut samples in the second and third annual rings. In the current-year root cut samples, water transport mainly occurred in the outermost rings from the current-year roots to leaves. In addition, the theoretical hydraulic conductivity of stained vessels in the stem cut samples was higher in the current-year root cut samples in the second and third annual rings. These findings indicate that the previously reported dye injection method using stem cut samples overestimated the water transport pathway in the inner part of the stems. Moreover, previous hydraulic conductivity measurement methods might not have considered the effects of radial resistance through the annual ring boundary, and they might have overestimated the hydraulic conductivity in the inner annual rings.

Fabrication of novel thin-film nanocomposite polyamide membrane by the interlayer approach: A review

Thin-film nanocomposite (TFN) membrane based on polyamide (PA) chemistry was widely applied for water purification and desalination process due to the improved water permeance. It remains a great challenge to significantly enhance rejection because of the non-selective defects caused by the aggregation of nanomaterials in the PA layer. Novel interlayer-based TFN (iTFN) membrane containing nanomaterial interlayer between the porous substrate and PA layer is the promising candidate to improve PA integrity and thus overcome the ubiquitous trade-off between permeability and selectivity. The nanomaterial interlayer not only promotes the subsequent interfacial polymerization (IP) but also provides improved pathways for water transport, which leads to simultaneous improvement in membrane permeability and selectivity. This review systematically categorizes nanomaterial interlayers into three types according to construction methods, namely, direct deposition, in situ growth and functional group-anchored in situ assembly (FAISA). The mechanism of interlayer modulating IP process and PA structure, as well as the effects on water transport, are comprehensively analyzed. Encouraging results reveal that using MOFs interlayer prepared by FAISA is the most promising way to break the trade-off in manufacturing reverse osmosis membranes. Finally, challenges and future efforts are presented for advancing iTFN membranes.

Does Surface Roughness Necessarily Increase the Fouling Propensity of Polyamide Reverse Osmosis Membranes by Humic Acid?

Surface roughness has crucial influence on the fouling propensity of thin film composite (TFC) polyamide reverse osmosis (RO) membranes. A common wisdom is that rougher membranes tend to experience more severe fouling. In this study, we compared the fouling behaviors of a smooth polyamide membrane (RO-s) and a nanovoid-containing rough polyamide membrane (RO-r). Contrary to the traditional belief, we observed more severe fouling for RO-s, which can be ascribed to its uneven flux distribution caused by the "funnel effect". Additional tracer filtration tests using gold nanoparticles revealed a more patchlike particle deposition pattern, confirming the adverse impact of "funnel effect" on membrane water transport. In contrast, the experimentally observed lower fouling propensity of the nanovoid-containing rough membrane can be explained by: (1) the weakened "funnel effect" thanks to the presence of nanovoids, which can regulate the water transport pathway through the membrane and (2) the decreased average localized flux over the membrane surface due to the increased effective filtration area for the nanovoid-induced roughness features. The current study provides fundamental insights into the critical role of surface roughness in membrane fouling, which may have important implications for the future development of high-performance antifouling membranes.

Emerging Materials for Interfacial Solar‐Driven Water Purification

AbstractSolar‐driven water purification is considered as an effective and sustainable technology for water treatment using green solar energy. One major goal for practical applications is to improve the solar evaporation performance by the design of novel photothermal materials, with optimized heat localization and water transport pathways to achieve reduced energy consumption for water vaporization. Recently, some emerging materials like polymers, metal‐organic frameworks (MOFs), covalent organic frameworks (COFs) and also single molecules were employed to construct novel solar evaporation systems. In this minireview, we present an overview of the recent efforts on materials development for water purification systems. The state‐of‐the‐art applications of these emerging materials for solar‐driven water treatment, including desalination, wastewater purification, sterilization and energy production, are also summarized.

Emerging Materials for Interfacial Solar-Driven Water Purification.

Solar-driven water purification is considered as an effective and sustainable technology for water treatment using green solar energy. One major goal for practical applications is to improve the solar evaporation performance by the design of novel photothermal materials, with optimized heat localization and water transport pathways to achieve reduced energy consumption for water vaporization. Recently, some emerging materials like polymers, metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and also single molecules were employed to construct novel solar evaporation systems. In this minireview, we present an overview of the recent efforts on materials development for water purification systems. The state-of-the-art applications of these emerging materials for solar-driven water treatment, including desalination, wastewater purification, sterilization and energy production, are also summarized.

Electrostatic deposition of TiO2 nanoparticles on porous wood veneer for improved membrane filtration performance and antifouling properties

Wood has been a promising water purifier material on account of its abundant natural transport channels, easy processing, and renewability, which is mainly focused on its utilization in growth direction for effective separation.Wood veneer manufacured from raw wood block has a reversed-tree pore structure, and possesses advantages of low cost, easy fabrication, material saving, and abundant sources. To realize its functionalization and practicable application for membrane separation, modification of wood veneer is prerequisite. Herein, thin wood veneer with disparate utilization direction of wood was developed to design filter membrane loading TiO2 nanoparticles for treatment of dye wastewater. Wood veneer with reversed-tree transport pathways exhibits unique porous structure, and filtering direction and wood growth direction is almost orthogonal generated numerous sinuous channels. Thereout, sufficient area for loading TiO2 nanoparticles and contacting pollutants as well as appropriate water transport pathways at significantly shrinking thickness of wood (the thickness of 0.2 mm) can be provide by these sinuous channels. TiO2 nanoparticles was first modified by (3-Aminopropyl)triethoxysilane with high positive charge, and immobilized on negatively charged wood surface through atmospheric impregnation via strong electrostatic attractive interaction. Vast quantities of exposed TiO2 nanoparticles on wood cell lumens significantly enhance the adsorption ability for dye contaminants, resulting in a high membrane separation performance. The flux of TiO2/wood veneer membrane can achieve high level of 636.94 L/(m2h) with considerable methylene blue removal of 99.9% at 0.01 MPa. Meanwhile, it shows good cycling stability as well as decent flexibility and excellent mechanical strength. Moreover, the designed membrane with photocatalytic function of TiO2 also displays impressive decontaminated and recycling ability. The flux can recover its pre-recession level after 10 h light irradiation. The designed TiO2/wood veneer with simple preparation process and excellent water treatment capacity exhibits promising results for practical wastewater treatment.

Dual-activation interfacial polymerization based anionic covalent organic framework nanofiltration membrane for high-flux dye separation

Covalent organic frameworks (COFs) hold great promise in constructing a new-generation of molecular separation membranes. Significantly, ionic COF membranes endow novel functions distinct from those of neutral membranes. However, ionic COF membranes generally suffer from extremely slow reaction rates and low yields, limiting their widespread application. In this work, a self-standing anionic COF membrane was prepared by a dual-activation interfacial polymerization strategy. And the obtained anionic COF membrane possessed a unique ordered pore structure, superhydrophilicity, as well as good chemical stability. Meanwhile, the as-prepared membrane provided the high-efficiency water transport pathways with effective rejection for dye molecules. As expected, the anionic COF membrane exhibited an excellent water permeability of about 270 L m−2 h−1 bar−1, which was much higher than those of commercial nanofiltration membranes, and also approximately 2–15 times significantly higher than those reported for polymer- or neutral COF-based nanofiltration membranes with similar rejection. Owing to the electrostatic attraction between positively charged dyes and anionic COF channels, the rejection rates of cationic dyes were above 96 %. In addition, the size-exclusion effect dominated rejection efficiency of dyes with molecular sizes larger than COF channels. These findings provided a new candidate membrane for efficient dye wastewater treatment.

Combined calcium pretreatment and ultrasonic/microwave drying to dehydrate black chokeberry: Novel mass transfer modeling and metabolic pathways of polyphenols

In this study, black chokeberries were dehydrated by sequential calcium pretreatment and ultrasonic/microwave drying. The investigation focused on exploring the mechanisms of water transport and metabolic pathways of polyphenols. A diffusional model was modified by considering the factors such as shrinkage, porosity and temperature-dependent water diffusivity to simulate the moisture transport. Accordingly, the Spatio-temporal evolutions of cytoplasm water, extracellular water and total water content in black chokeberry throughout drying were successfully revealed. On the other hand, the quality attributes involved in the metabolic pathways of polyphenols, i.e., free/bound phenolics, cell wall pectin, polyphenol oxidase (PPO) or peroxidase (POD), and viscoelastic properties under these drying treatments were intensively analysed. Through correlation analysis, it was found that CaCl2 pretreatment strengthened the oxidation of free procyanidin B2 by PPO. In contrast, both ultrasound and microwave drying weakened the negative influence of PPO on the stability of free rutin. Besides, temperature rise promoted the loss of free polyphenols and the degradation of cell wall pectin, weakening the attachment of bounded-caffeic acid on the cell wall. This investigation provides new physical and chemical understandings about fruit drying and reveals the potential benefits of hybrid drying technologies.

Hydrological and sediment connectivity under freeze–thaw meltwater compound erosion conditions on a loessal slope

Freeze-thaw processes can influence hydrology, soil erosion, and morphological development by altering the connectivity between active pathways of water and sediment transport. Concentrated flow experiments were conducted involving frozen, shallow thawed, and unfrozen soil slopes under 1, 2, and 4 L/min runoff rates at a temperature of approximately 5 °C. In this study, hydrological connectivity was analysed via the simplified hydrological curve and relative surface connection function. Sediment connectivity was analysed via the sediment structure connectivity and sediment functional connectivity. Results indicated that hydrological connectivity was greatest on frozen slopes (FS), followed by shallow thawed slopes (STS), and unfrozen slopes (UFS) given a constant flow rate. Hydrological connectivity increased with increasing runoff rate for each freeze-thaw condition. Freezing condition and runoff rate exhibited a positive response to the hydrological connectivity. Sediment structure connectivity increased with increasing runoff rate for each slope condition. The ordering of sediment structure connectivity across freeze-thaw condition was that FS was greater than STS while STS was greater than UFS independent of flow rate. Sediment functional connectivity included longitudinal, lateral, and vertical connectivity components. Sediment longitudinal and vertical connectivity indicated a trend of first increasing and then decreasing under the different runoff rates and freeze–thaw conditions. For a given runoff rate, the ordering of sediment longitudinal and vertical connectivity across freeze-thaw condition was that FS was greater than STS while STS was greater than UFS. Sediment lateral connectivity exhibited a trend of first decreasing and then stabilizing. The ordering of sediment lateral connectivity across freeze-thaw condition was that UFS was greater than STS while STS was greater than FS. FS could more easily reach longitudinal and vertical penetration. Sediment longitudinal and vertical connectivity rates demonstrated increasing trends with increasing runoff rate after runoff generation stabilization and gradually approached unity. This research further improves our understanding of the hydrological and erosional mechanisms of meltwater and the generation of flooding in frozen soil conditions.

Facile electrospray fabrication of ultralow biofouling cellulose acetate desalination membrane with nanocellulose/UiO66-NH2 fillers

The inherently high porosity, hydrophilicity, and large surface area of the octahedral UiO66-NH2 nanocrystals were exploited in synergy with cellulose nanocrystals (CNCs) as electrospray coating nanocomposites onto the cellulose acetate (CA) desalination membranes. Optimal loadings of both nanoparticles (0.05% w/v each) enabled the partial embedment of the defective metal-organic framework (MOF) crystals in the dense CA layer, successfully facilitating a faster, low-tortuosity water transport pathway through the active layer. With just one electrospray scan, the CNC/UiO66-NH2-coated CA membrane achieved an almost doubled the water permeability coefficient of 0.24 L m−2 h−1 bar−1 while maintaining a retention efficiency of over 94% in brackish water desalination. Moreover, the electrospray-coated membrane demonstrated healthier flux recovery from continuous E. coli cross-flow filtration exposure, exhibiting great resistance to biofouling. Overall, the CNC/UiO66-NH2-coated CA membrane outperforms many CA-based desalination membranes reported in the literature in terms of water/salt permselectivity and anti-fouling capabilities.

Porous substrate affects fouling propensity of thin-film composite nanofiltration membranes

Fouling is a critical consideration for the design of thin-film composite (TFC) nanofiltration membranes. Traditional wisdom believes that fouling propensity is primarily dictated by membrane surface properties while porous substrates play little role (on the basis on the latter have no effect on the foulant-membrane interaction). Nevertheless, porous substrates can regulate the water transport pathways, resulting in uneven water flux distribution over the membrane surface. For the first time, we experimentally investigated the micro-scale water flux distribution for nanofiltration membranes with different substrate porosities and the impact of such flux distribution pattern on fouling. With gold nanoparticles as tracers, we demonstrated more evenly distributed water flux at increasing substrate porosity. This was found to effectively alleviate membrane fouling by eliminating localized hot spots of high flux. Furthermore, higher substrate porosity also effectively enhanced the membrane water permeance due to the optimized water transport pathways. Our study reveals the fundamental relationship between the micro-scale transport behavior and the membrane fouling propensity, which provides a firm basis for the rational design of TFC membranes toward better separation performance.

(Invited) Effect of Water Management in Membrane and Cathode Catalyst Layers on Suppressing the Performance Hysteresis Phenomenon in Anion-Exchange Membrane Fuel Cells

Anion exchange membrane fuel cells (AEMFCs) are vulnerable to water management problems, since water is produced at the anode and consumed at the cathode. Previously we found severe voltage losses when increasing the current density in an AEMFC with a commercial Fe–N–Cp cathode catalyst and an in-house-developed anion exchange ionomer (quaternized poly(arylene perfluoroalkylene), i.e., QPAF-4, developed in this laboratory (Figure 1)1,2. In the present work,3 we have clearly identified the problem as being related to water management and developed two approaches to alleviating the problem: i) by use of a thin hydrophilized membrane, the diffusivity of water at the surface was improved, and the severe I–V hysteresis was suppressed, despite the cell using an Fe–N–Cp cathode catalyst with high-water absorption (Figs. 2a and 3a); ii) the voltage loss was also alleviated by the use of a recently developed Fe–N–Cc catalyst with higher hydrophobicity, which decreased the absorption of back-diffusing water into the catalyst layer and increased the amount of water supplied to the reaction sites. These improvements have demonstrated that water transport is the main limitation for the previously reported hysteresis and provide strategies to achieve higher performance AEMFCs through proper water management and formation of water transport pathways (Figs. 2b and 3b). Acknowledgements This project was partly supported by the New Energy and Industrial Technology Development Organization (NEDO) Japan through funds for the “Advanced Research Program for Energy and Environmental Technologies,” by the Japan Society for the Promotion of Science (JSPS) and the the Swiss National Science Foundation (SNSF) under the Joint Research Projects (JRPs) program, and by the Japan Science and Technology (JST) through the Strategic International Collaborative Research Program (SICORP). We are grateful to Pajarito Powder supplying the Fe–N-Cp catalyst. Also, we are deeply grateful to Dr. Weilin Xu and Dr. Ping Song of Changchun Institute of Applied Chemistry and Dr. Shuanjin Wang of Sun Yat-sen University for supplying the Fe–N-Cc catalyst, and to Takahata Precision Co. Ltd. for kindly providing the QPAF-4 membrane and ionomer. References H. Ono, T. Kimura, A. Takano, K. Asazawa, J. Miyake, J. Inukai, K. Miyatake, Robust anion conductive polymers containing perfluoroalkylene and pendant ammonium groups for high performance fuel cells, J. Mater. Chem. A 5 (2017) 24804–24812, https://doi.org/10.1039/c7ta09409d.K. Otsuji, N. Yokota, D. A. Tryk, K. Kakinuma, K. Miyatake, M. Uchida, Performance hysteresis phenomena of anion exchange membrane fuel cells using an Fe–N–C cathode catalyst and an in-house developed polymer electrolyte, J. Power Sources, 487 (2021) 229407, https://doi.org/10.1016/j.jpowsour.2020.229407K. Otsuji, Y. Shirase, T. Asakawa, N. Yokota, K. Nagase, W. Xu, P. Song, S. Wang, D. A. Tryk, K. Kakinuma, J. Inukai, K. Miyatake, M. Uchida, J. Power Sources, 522 (2022) 230997, https://doi.org/10.1016/j.jpowsour.2022.230997 Figure 1

A scalable method to fabricate high-performance biomimetic membranes for seawater desalination: Incorporating pillar[5]arene water nanochannels into the polyamide selective layer

In this work, we explored the practicability of a nanochannel-based biomimetic membrane (NBM) incorporating pillar[5]arene water channels for seawater reverse osmosis (SWRO) desalination. Two classes of peptide-attached biomimetic channels, (pR)-pillar[5]arenes (pRPH) and (pS)-pillar[5]arenes (pSPH) were integrated into the selective layer of SWRO membranes via interfacial polymerization on the top side of a polysulfone (PSf) support membrane. Here, pSPH is a non-identical stereoisomer of pRPH and was used as a negative control to pRPH to elucidate the flux enhancement effect contributed by pRPH. The optimized NBM presented a water permeability of 2.52 L m-2 h-1 bar-1 and 99.5% rejection under SWRO testing conditions of 50 bar applied pressure and 32,000 mg/L NaCl as feed solution. The 62% permeability increment with reference to the control membrane is hypothesized to originate from hybrid polyamide layers that were rougher with more voids (higher effective surface area and lower hydraulic resistance for water transport) as well as the conceivable water transport pathways provided by the pRPH channels. The simulation results from module-scale modelling suggest that the optimized NBM could lead to 7.2% savings in specific energy consumption of the membrane unit stage (or reduce the required membrane area by 25%) with respect to the commercial SWC4-LD membrane. The performance of the optimized NBM was further assessed in a one-week desalination test using an actual seawater feed gathered from an SWRO plant in Singapore. The robust NBM exhibited stable performance and ∼28% higher water flux (42 L m-2 h-1) than SWC4-LD with a comparable rejection of 99.3%, suggesting the feasibility of pillar[5]arene-based biomimetic membranes for seawater desalination.

Influence of Mesoscale Interactions on Proton, Water, and Electrokinetic Transport in Solvent-Filled Membranes: Theory and Simulation.

Transport of protons and water through water-filled, phase-separated cation-exchange membranes occurs through a network of interconnected nanoscale hydrophilic aqueous domains. This paper uses numerical simulations and theory to explore the role of the mesoscale network on water, proton, and electrokinetic transport in perfluorinated sulfonic acid (PFSA) membranes, pertinent to electrochemical energy-conversion devices. Concentrated-solution theory describes microscale transport. Network simulations model mesoscale effects and ascertain macroscopic properties. An experimentally consistent 3D Voronoi-network topology characterizes the interconnected channels in the membrane. Measured water, proton, and electrokinetic transport properties from literature validate calculations of macroscopic properties from network simulations and from effective-medium theory. The results demonstrate that the hydrophilic domain size affects the various microscale, domain-level transport modes dissimilarly, resulting in different distributions of microscale coefficients for each mode of transport. As a result, the network mediates the transport of species nonuniformly with dissimilar calculated tortuosities for water, proton, and electrokinetic transport coefficients (i.e., 4.7, 3.0, and 6.1, respectively, at a water content of 8 H2O molecules per polymer charge equivalent). The dominant water-transport pathways across the membrane are different than those taken by the proton cation. Finally, the distribution of transport properties across the network induces local electrokinetic flows that couple water and proton transport; specifically, local electrokinetic transport induces water chemical-potential gradients that decrease macroscopic conductivity by up to a factor of 3. Macroscopic proton, water, and electrokinetic transport coefficients depend on the collective microscale transport properties of all modes of transport and their distribution across the hydrophilic domain network.

Modeling Preferential Water Flow and Pesticide Leaching to Drainpipes: The Effect of Drain‐Connecting and Matrix‐Terminating Biopores

AbstractBiopores and cracks in soils act as fast transport pathways for water and solute, potentially leading to pesticide leaching shortly after application. The biopore module in the agrohydrological model Daisy was developed to simulate preferential water flow directly to drainpipes, in drain‐connecting biopores, and to deeper soil layers, in matrix‐terminating biopores. We tested the biopore module in Daisy against field measurements of water flow and transport of bentazone and imidacloprid after application to a cracking clay field. We generated two model concepts, drain‐connecting biopores (DCB) with drain‐connecting biopores and drain‐connecting and matrix‐terminating biopore (DCMTB) with both drain‐connecting and matrix‐terminating biopores. Parameters describing the biopores were estimated by inverse modeling of observations of water flow and pesticide concentrations in drains. After calibration, both models satisfactorily simulated water flow and pesticide leaching to drains (root‐mean‐square error (RMSE)‐observations standard deviation ratio (RSR) < 0.1). Particularly, the results showed that the models were able to describe the high concentration of bentazone in drain water shortly after application. Thus, the simpler DCB model preformed just as well or better than the more complex DCMTB model (ΔAIC = 4.68 [AIC, Akaike information criteria]). Discrepancies between observations and simulations in the beginning of the drainage season were attributed to the limitations that arise when simulating dynamic DCB flow paths with a static biopore model. The pesticide distribution in the field over time was well represented, especially by the DCMTB model. We therefore conclude that Daisy can simulate fast breakthrough of pesticides in drain water and describe very well pesticide concentration in drain water throughout the drainage season.