Solute Flux Research Articles

Investigating novel thin-film nanocomposite membranes for sustainable water recovery using fertilizer-driven forward osmosis – Experimental and machine learning approaches

Water recovery from municipal wastewater can augment freshwater resources to meet increasing demand. An osmotic-driven membrane separation process- forward osmosis (FO) is currently being explored as a sustainable technology. This work proposes to address the challenges associated with FO namely (i) robust membrane and (ii) draw solute (DS) recovery. Robust thin-film nanocomposite membranes incorporating a) nickel ferrite or b) nitrogen-enriched nanoporous polytriazine (NENP-1) covalent organic framework were fabricated with enhanced hydrophilicity, surface roughness and anti-fouling properties. The optimum membranes M2 and C2 displayed a pure water flux of 4.86 ± 0.11 and 5.4 ± 0.2 L/m2h respectively and a specific reverse solute flux (SRSF) <<1 when using 1 M NaCl solution as the DS (feed solution – DI water). Fertilizer-driven FO (FDFO) was proposed as the diluted DS need not be recovered but could be used directly for irrigation. The pure water flux for both M2 and C2 membranes were in the following order for the fertilizers used as DS (1 M) - (NH4)2SO4 + (NH₄)₂HPO₄ > (NH4)2SO4 > (NH₄)₂HPO₄ which indicates that the mixed ions in the DS enhanced the water permeance. In all cases, the SRSF was < 1 g/L indicating the feasibility of the process. The membranes exhibited a TOC removal of > 90 % from synthetic municipal wastewater containing persistent organic pollutants and personal & pharmaceutical care products and the membranes could be regenerated after washing with a 10 mM solution of SDS for 5 cycles of operation. Further, ANN was used to develop a predictive model for water flux in FO membranes and the optimized architecture of 7–5–50–40–1 displayed a remarkable overall R2 value of 0.98 (MSE= 0.027). The FDFO process using the fabricated thin-film nanocomposite membranes holds enormous potential to be investigated in larger-scale studies.

Contrasting physical erosion rates in cratonic catchments: The Ogooué and Mbei rivers, Western Central Africa

We measured the long-term physical denudation of the Ogooué River catchment using 10Be produced in situ by cosmic rays. These measurements are averaged over 25–200 ka (average 40 ka), depending on the physical denudation rate. The denudation rate of the Ogooué River catchment is slow (38 t/km2/a, 15 m/Ma), slightly higher than in Equatorial West Africa (from Senegal to Angola, 26 t/km2/a, 10 m/Ma). Physical denudation and chemical weathering fall within the same order of magnitude. Thus, although low, there is substantial chemical weathering compared to physical denudation, that likely contributes over 30 % of the total denudation.Denudation rates are spatially variable (from 10 to 60 t/km2/a) within the large Ogooué River catchment. Over the long term, physical denudation and chemical weathering roughly match, except in the Batéké Plateaux area, because the plateaus are made up of already weathered detrital material and therefore their modern flux of solutes is very low (∼9.5 t/km2/a). The spatial distribution is similar to the one described in the work of Moquet et al. (2021) on the basis of solute fluxes, i.e. the southern part of the catchment is denuding twice as fast as the northern part. We show here that the whole picture did not vary much since 100 ka, as shown by both methods which give consistent results. Faster denudation in the southern part of the catchment may be related to more uplift than in the northern part caused by the southern African “superswell”.

Hydrochemical characterization and pCO2 dynamics in the surface waters of Himalayan River: A case study of river Alaknanda.

Chemical weathering processes are becoming increasingly important in studies on carbon cycling because they are responsible for increased solute fluxes in the proglacial zone, can effectively sequester atmospheric CO2 and raise carbon budgets for lateral transport via rivers. Here, we examined the hydrochemical and hydrogeochemical processes, solute sources and factors controlling riverine pCO2 of the Alaknanda River and its tributaries for three sampling seasons, viz. pre-monsoon (May 2021), post-monsoon (October 2021) and winter (January 2022). The surface water is enriched with Ca2+ and Mg2+ as the dominant cations, while HCO3- and SO42- were the major anions. Gibbs's plot confirmed rock weathering as the leading mechanism in controlling the hydrochemistry of the basin. The chemical composition of river water was mainly regulated by the weathering of carbonate end members: dolomite, limestone and feldspar along with small inputs from silicate weathering. The mean pCO2 values in the mainstream (1702.7 µatm), Pindar (2267.9 µatm) and Mandakini (1136.1 µatm) revealed the streams were oversaturated with CO2 having a higher rate of exporting excess CO2 gas to the atmosphere. The study showed the persistence of high pCO2 closed system characteristics associated with increased suspended sediment concentration resulting from carbonate weathering, dominance of HCO3- over SO42- and thereby results in high values of C ratio. Principal component analysis of the water chemistry suggests that weathering contributes about 41%, while humans contribute about 13% of the ionic load to the river. This study is one of its kind to understand the system characteristics of Alaknanda River water.

A multiphasic model for determination of mouse ascending thoracic aorta mass transport properties with and without aneurysm.

Thoracic aortic aneurysms (TAAs) are associated with aortic wall remodeling that affects transmural transport or the movement of fluid and solute across the wall. In previous work, we used a Fbln4E57K/E57K (MU) mouse model to investigate transmural transport changes as a function of aneurysm severity. We compared wild-type (WT), MU with no aneurysm (MU-NA), MU with aneurysm (MU-A), and MU with an additional genetic mutation that led to increased aneurysm penetrance (MU-XA). We found that all aneurysmal aortas (MU-A and MU-XA) had lower fluid flux compared to WT. Non-aneurysmal aortas (MU-NA) had higher 4kDa FITC-dextran solute flux than WT, but aneurysmal MU-A and MU-XA aortas had solute fluxes similar to WT. Our experimental results could not isolate competing factors, such as changes in aortic geometry and solid material properties among these mouse models, to determine how intrinsic transport properties change with aneurysm severity. The objective of this study is to use biphasic and multiphasic models to identify changes in transport material properties. Our biphasic model indicates that hydraulic permeability is significantly decreased in the severe aneurysm model (MU-XA) compared to non-aneurysmal aortas (MU-NA). Our multiphasic model shows that effective solute diffusivity is increased in MU-NA aortas compared to all others. Our findings reveal changes in intrinsic transport properties that depend on aneurysm severity and are important for understanding the movement of fluids and solutes that may play a role in the diagnosis, progression, or treatment of TAA.

Phosphate pre-concentration from wastewater by a continuous flow bench-scale forward osmosis membrane: A circular economy approach on nutrient recovery

Phosphate is a vital element necessary for the growth and development of plants, making it a crucial element in agricultural fertilizers. Extracting phosphate from wastewater for recovery aligns with the principles of a circular economy by closing the loop on nutrient cycles. Instead of viewing wastewater as a waste product, treating it as a resource for recovering valuable nutrients like phosphate promotes a more sustainable and efficient use of resources. In this study, the phosphate from synthetic wastewater was pre-concentrated by a continuous flow forward osmosis membrane system to facilitate effective precipitation. The pre-concentration feasibility of forward osmosis was studied by changing the draw concentration, feed concentration, feed pH, and flow rate of the feed solution. With the optimum operational parameters in batch mode such as pH of 7, the draw solute concentration of 0.4 M MgSO4, the feed and draw flowrate of 0.7 L/min and 0.3 L/min, the phosphate concentration was increased from 30 mg/L to 525 mg/L after 60 min, the average osmotic flux and reverse solute flux was 2.7 L/m2/h and 0.43 g/m2/h, respectively. As operated with continuous mode, the final phosphate concentration was increased four times, the average osmotic flux was higher with 8.1 L/m2/h and the reverse solute flux was 0.86 g/m2/h, which could improve the efficiency of calcium phosphate crystallization in precipitation/ crystallization reactors. This integrated system, which includes forward osmosis as a pretreatment method followed by a precipitation process, is technically possible for application on a larger scale as a circular economy approach.

Growing Macrophages Regulate High Rates of Solute Flux by Pinocytosis.

Murine macrophages growing in response to colony-stimulating factor-1 (CSF1) require pinocytosis. High rates of solute influx and accumulation by pinocytosis are regulated by CSF1 and leucine. Low molecular weight products of protein hydrolysis in lysosomes recycle efficiently from the cells.

Entropy production of quantum reset models

We analyze the entropy production of Quantum Reset Models (QRMs) corresponding to quantum dynamical semigroups driven by Lindbladians motivated by a probabilistic description of dissipation in an external environment. We investigate the strict positivity of entropy production for Lindbladians given as sums of QRMs, when the Hamiltonian of the total Lindbladian is split as an affine combination of Hamiltonians of the individual QRMs. In this setup, we derive conditions on the coefficients of the combination and on the reset states ensuring either positive or zero entropy production. Second, we deal with a tri-partite system subject at its ends to two independent QRMs and a weak coupling Hamiltonian. The latter is split as an affine combination of individual Hamiltonians, and we provide necessary and sufficient conditions ensuring strict positivity of the entropy production to leading order, with the possible exception of one affine combination. We apply these results to a physically motivated model and exhibit explicit expressions for the leading orders steady-state solution, entropy production and entropy fluxes. Moreover, these approximations are numerically shown to hold beyond the expected regimes.

COSMO-RS screening of organic mixtures for membrane extraction of aromatic amines: TOPO-based mixtures as promising solvents

Aromatic amines are crucial in pharmaceuticals, but their synthesis is challenging due to unfavorable reaction equilibria and the use of costly, environmentally unfriendly methods. This study presents a membrane extraction (ME) process for in situ product removal (ISPR) of aromatic amines. Using a supported liquid membrane (SLM), -methylbenzylamine (MBA) and 1-methyl-3-phenylpropylamine (MPPA) were separated from isopropyl amine (IPA). COSMO-RS was employed to screen over 200 organic mixtures, identifying twelve mixtures based on trioctylphosphine oxide (TOPO), lidocaine, and menthol as solvent candidates, due to their hydrophobicity. These mixtures were analysed for critical solvent properties including density, viscosity, hydrophobicity, and hydrogen bonding interactions. ME tests showed TOPO-thymol had the highest solvent residual and selectivity. Moreover, TOPO-thymol demonstrated solute fluxes of 9.0±3.0 g/(m2 h) for MBA, 16.5±5.4 g/(m2 h) for MPPA, and 0.7±0.3 g/(m2 h) for IPA, with selectivity values of 12.4±0.8 for MBA/IPA and 22.8±1.4 for MPPA/IPA. Compared to undecane, which had lower selectivity values of 6.9±0.8 for MBA/IPA and 10.1±1.3 for MPPA/IPA, TOPO-thymol showed superior selectivity, indicating its promise as an extractant for ME applications.

Green power generation from the Tigris River using pressure retarded osmosis process

Sustainability including renewable energy and green power, is one of the important feature in recent years due to environmental constraints and the emission of CO2 from fossil fuel. Pressure retarded osmosis (PRO) process is considered one of the effective technology for power generation. This study assessed the application of pressure retarded osmosis to produce power from Tigris River water in Baghdad City, Iraq. Spiral wound TFC membrane was tested in the PRO process with different variables. The effect of different types of draw solutions (MgCl2, NaCl, Sodium Formate, KCl, Sodium Acetate), applied pressure (0 – 7 bar), and draw solution concentration (0.08 and 0.4 M) were tested in this work. The flux, recovery, and power density for the five draw solution in the order MgCl2 >NaCl>sodium formate>KCl>sodium acetate, while the reverse solute flux in the order MgCl2 <sodium acetate<KCl<sodium formate<NaCl. Experimentally the membrane pure water permeability (A) was found to be 4.87 L/m2.h.bar. The result revealed that the reverse solute flux and the solute permeability coefficient for MgCl2 was 0.55 g/m2.h and 8.78 × 10−8 m/s. The flux, recovery, and power density for MgCl2 with a concentration of 0.4 M and applied pressure of 7 bar was 1.69 LMH, 19 %, and 0.33 W/m2, respectively.

Molecular Dynamics Simulation of Membrane Distillation for Different Salt Solutions in Nanopores.

Nanoporous membranes offer significant advantages in direct contact membrane distillation applications due to their high flux and strong resistance to wetting. This study employs molecular dynamics simulations to explore the performance of membrane distillation in a single nanopore, mainly focusing on wetting behavior, liquid entry pressure, and membrane flux variations across different concentrations and types of salt solutions. The findings indicate that increasing the NaCl concentration enhances the wetting of membrane pores, thereby decreasing the entry pressure of the solution. However, at the same salt concentration, the differences in wetting and liquid entry pressure among various salts, including CaCl2, KCl, NaCl, and LiCl, are minimal. The presence of hydrated ions significantly reduces membrane flux. As the concentration of NaCl solutions increases, the number of hydrated ions rises, thereby lowering the membrane flux of the salt solution. Furthermore, the type of salt has a pronounced effect on the structure of hydrated ions. Solutions with Ca2+ and Li+ exhibit the smallest first-layer radius of hydrated ions. Under the same salt concentration, KCl solutions demonstrate the highest membrane distillation flux, while CaCl2 solutions show the lowest flux.

Analyzing multicomponent permeation and coupling effects in pervaporation of Acetone-Butanol-Ethanol solutions using Maxwell-Stefan based modeling

The state-of-the-art research in pervaporation lacks a comprehensive understanding of the selective membrane permeation in real and multicomponent mixtures, a factor critical for its widespread commercial adoption. This work elucidates the contribution of various interaction effects, known as coupling phenomena, on the pervaporation of multicomponent Acetone-Butanol-Ethanol (ABE) solutions through a commercial PDMS membrane. Maxwell-Stefan (MS) diffusion formulations, combined with the UNIQUAC thermodynamic model, mostly restricted in literature to binary solutions permeating through a polymer membrane, are extended to multicomponent feed solutions. The thermodynamic correction factor [Γ] and correlation [B]−1 matrices are analyzed to resolve coupling into its thermodynamic and kinetic (diffusive) constituents.A generalized and explicit analytical derivation for calculation of [Γ] by UNIQUAC model is proposed, allowing estimation for any number of permeants. Subsequently, a significant inhibitory coupling of the component fluxes to the driving forces of its accompanying penetrants is revealed. In addition to the non-ideality arising from diagonal elements Γii, the substantial negative off-diagonal elements Γij in the thermodynamic correction matrices anticipate a decline in effective driving forces, butanol fluxes and permeation selectivity as we transition from binary butanol-water to multicomponent ABE mixtures.Following this, a detailed hit-and-trial based strategy is implemented to evaluate the relevance of membrane plasticization, cluster formation and interspecies frictional interactions towards the MS self and cross diffusivities within the [B]−1 matrix. Existing semi-empirical expressions for self-diffusivities in binary alcohol-water systems incorporating plasticization and clustering constants are reformulated and compared for their ability to accurately describe fluxes in binary and ternary ABE solutions. Furthermore, the optimal model fit was found to be insensitive to variation in MS cross-diffusivities. This suggests that the contribution of correlation effects may be neglected altogether, provided the expressions for self-diffusivities are adequately tailored for membrane plasticization and clustering. Notably, while only butanol clustering suffices for binary mixtures, additional aggregates involving butanol-water, water-water, and butanol-acetone/ethanol are suggested to play a crucial role in steering diffusivities in ternary solutions.Consequently, the proposed models exhibit exceptional agreement with experimental data, achieving R2 values of approximately 0.96, 0.95, and 0.98 for butanol flux in binary butanol-water and ternary solutions containing acetone and ethanol, respectively. Besides providing a more cohesive fit to the overall experimental permeation data, the usefulness of this approach lies in significantly simplifying model computations, thus easing the potential modeling of even more complex mixtures.

Forest catchment structure mediates shallow subsurface flow and soil base cation fluxes

Hydrologic behavior and soil properties across forested landscapes with complex topography exhibit high variability. The interaction of groundwater with spatially distinct soils produces and transports solutes across catchments, however, the spatiotemporal relationships between groundwater dynamics and soil solute fluxes are difficult to directly evaluate. While whole-catchment export of solutes by shallow subsurface flow represents an integration of soil environments and conditions but many studies compartmentalize soil solute fluxes as hillslope vs. riparian, deep vs. shallow, or as individual soil horizon contributions. This potentially obscures and underestimates the hillslope variation and magnitude of solute fluxes and soil development across the landscape. This study determined the spatial variation and of shallow soil base cation fluxes associated with weathering reactions (Ca, Mg, and Na), soil elemental depletion, and soil saturation dynamics in upland soils within a small, forested watershed at the Hubbard Brook Experimental Forest, NH. Base cation fluxes were calculated using a combination of ion-exchange resins placed in shallow groundwater wells (0.3 – 1 m depth) located across hillslope transects (ridges to lower backslopes) and measurements of groundwater levels. Groundwater levels were also used to create metrics of annual soil saturation. Base cation fluxes were positively correlated with soil saturation frequency and were greatest in soil profiles where primary minerals were most depleted of base cations (i.e., highly weathered). Spatial differences in soil saturation across the catchment were strongly related to topographic properties of the upslope drainage area and are interpreted to result from spatial variations in transient groundwater dynamics. Results from this work suggest that the structure of a catchment defines the spatial architecture of base cation fluxes, likely reflecting the mediation of subsurface stormflow dynamics on soil development. Furthermore, this work highlights the importance of further compartmentalizing solute fluxes along hillslopes, where certain areas may disproportionately contribute solutes to the whole catchment. Refining catchment controls on base cation generation and transport could be an important tool for opening the black box of catchment elemental cycling.

Design and fabrication of high-performance ultrafiltration membranes for low-temperature conditions

The influence of cold weather conditions on ultrafiltration (UF) membrane performance is noteworthy. Investigating alterations in UF membrane fouling behavior under low-temperature conditions and developing strategies to enhance their performance holds significant importance for advancing membrane separation technology in cold regions. We initiate an exploration into how low-temperature conditions impact the permeation and separation capabilities of unmodified PES UF membranes, concurrently scrutinizing the associated influencing mechanisms. Employing molecular design, we strategically incorporate hydrophilic carboxyl-functionalized groups into the molecular structure of poly (aryl ether sulfone) materials. This method facilitates the development of a series of PAES-modified UF membranes (LTM-x%), exhibiting exceptional performance in low-temperature conditions, grounded in the principles of the hydration layer theory. In a low-temperature condition (5±1 °C), the BSA solution flux and SA solution flux of the LTM-80 membrane surpass the pristine PES membrane flux by 187.38 % and 171.82 %, respectively. Notably, compared to the solution flux at room temperature (22±1 °C), the LTM-80 membrane shows only a slight decrease in the 5±1 °C temperature (flux decline rates of 18.52 % for BSA solution and 15.12 % for SA solution), in contrast to the pronounced decline observed in the pristine PES membrane (49.24 % for BSA and 47.67 % for SA). This investigation unveils an effective and viable strategy for designing and developing high-performance UF membranes suitable for cold regions.

Practical Osmotic Agent for High-Degree Pharmaceutical Pre-Concentration by Organic Solvent Forward Osmosis.

Pre-concentration can reduce the total production costs in the pharmaceutical industry. Organic solvent forward osmosis (OSFO) is a suitable pre-concentration method because of its nonthermal nature, low capital cost, and potential for achieving high-degree concentrations. In a previous study, we first demonstrated a high-degree OSFO concentration. Sucrose octaacetate (SoA) in MeOH was concentrated to 52 wt% using polyethylene glycol (PEG)-400 as the osmotic agent, but the concentrated solution had a concentration of 17% PEG-400 because of the reverse solute flux. This result does not meet the typical purity standards required for pharmaceutical production, indicating the need to determine a suitable osmotic agent that can be used for practical purposes. This study proposes a practical osmotic agent for OSFO pre-concentration. First, osmotic agents were screened from a practical perspective. Polypropylene glycol (PPG)-400 was selected, owing to its low toxicity, good solubility, and low viscosity. Subsequently, the OSFO concentration was demonstrated using PPG-400 as the osmotic agent. SoA in MeOH was concentrated from 9.4 wt% to 48 wt%. The final feed solution contained only 0.04 wt% PPG-400. This result is the first demonstration of successful pharmaceutical pre-concentration using OSFO that satisfies the typical purity requirement in pharmaceutical production.

Convective Instability Driven by Diffusiophoresis of Colloids in Binary Liquid Mixtures.

In a binary fluid mixture, the concentration gradient of a heavier molecular solute leads to a diffusive flux of solvent and solute to achieve thermodynamic equilibrium. If the solute concentration decreases with height, the system is always in a condition of stable mechanical equilibrium against gravity. We show experimentally that this mechanical equilibrium becomes unstable in case colloidal particles are dispersed uniformly within the mixture and that the resulting colloidal suspension undergoes a transient convective instability with the onset of convection patterns. By means of a numerical analysis, we clarify the microscopic mechanism from which the observed destabilization process originates. The solute concentration gradient drives an upward diffusiophoretic migration of colloids, in turn causing the development of a mechanically unstable layer within the sample, where the density of the suspension increases with height. Convective motions arise to minimize this localized rise in gravitational potential energy.

Incorporation of zeolitic imidazolate framework-8 (ZIF-8) in the polyamide and polysulfone layers of forward osmosis membranes for enhancing aquaculture wastewater recovery and PPCPs removal

Wastewater recovery is essential to alleviate water resource shortages, and this can be achieved through a high-energy-efficient forward osmosis (FO) process combined with an emerging material, zeolitic imidazolate framework-8 (ZIF-8). Here, we create thin-film composite FO membranes (TF-CFOMs) by incorporating ZIF-8 into the active polyamide (PA) and/or support polysulfone (PSf) layers to address the challenges of low water flux and loss of draw solutes during operation. Experimental factors included the dosage of ZIF-8 nanoparticles in PA preparation solutions and the dosages of 2-methylimidazole (2-Hmim) and zinc nitrate hexahydrate (ZNH) in n-methyl-2-pyrrolidone (NMP) to fabricate the PSf casting solutions with in-situ formed ZIF-8 nanoparticles. Successful ZIF-8 incorporation on the TF-CFOM surface was confirmed, and the ZIF-8 TF-CFOMs exhibited increased surface hydrophilicity and separation performance. Only modifying the PA layer by adding 0.025 wt% ZIF-8 nanoparticles in trimesoyl chloride (TMC) resulted in the membrane (PA0.025T-PSf0) with water flux 2.3 times higher than the pristine TF-CFOM (4.9 LMH). The pristine and modified TF-CFOMs were further applied for aquaculture wastewater (AWW) recovery and removal of pharmaceuticals and personal care products (PPCPs). Results of water recovery demonstrated that the recovery rate reached 89.1% in 3.5 days when using the dual-layer modified TF-CFOM. Results of PPCP removal indicated that both pristine and modified TF-CFOMs can achieve high PPCP rejection efficiency (>90%), with the modified TF-CFOM (PA0.025T-PSf2.0) performing the best. Overall, the PA0.025T-PSf2.0 TF-CFOM achieved high and stable separation efficiency in long-duration AWW recovery, making it well-suited for practical field applications.

A 5,5’‐Thiobis(thiazol‐2‐amine)‐based dithiocarbamate polymer: Straightforward synthesis and application in PVC membrane modification to enhance cadmium and dye removal

AbstractA novel dithiocarbamate polymer (TTDP) derived from bis(2‐aminothiazole) sulfide was synthesized through a straightforward process. The synthesis involved the initial conversion of 2‐aminothiazole into its bis(sulfide), subsequent reaction with chloroacetyl chloride, and final copolymerization with disodium ethylene bisdithiocarbamate. TTDP boasts a high percentage of functional groups containing sulfur, nitrogen, and oxygen, contributing to its hydrophilicity, strong chelation capacity with metal cations, and compatibility with other polymers. Therefore, it was used as a strong candidate for making membranes in water media. According to this, TTDP was blended in ratios 1, 2, 5, and 10 wt% with polyvinyl chloride (PVC; 15 wt%), 2 wt% of polyethylene glycol 4000 in N,N‐dimethylacetamide as polymeric membranes for water‐based applications. The blended membranes were prepared using the casting and immersion precipitation method. The blended membrane showed high fluxes, up to 1052 L/m2 h for 2 wt% of TTDP (in comparison to the bare membrane's 459 L/m2h). Notably, they demonstrated an excellent protein solution flux of 222–269 L/m2 h at 3 bar with 96%–98% bovine serum albumin rejection. Furthermore, these membranes showed remarkable efficacy in removing cadmium ions (up to 98.96% for 5 and 10 wt% TTDP) and synthetic dye methyl orange (up to 84.03% for 2 wt% TTDP).

Combined nanofiltration and diafiltration for isolation of rare-earth ions

Rare earth elements (REEs) are critical materials due to their utilization in high-flux magnets for wind turbines and electric motors. Purification and recycling of REEs are vital for maintaining their supply. This work explores and models nanofiltration (NF) followed by diafiltration for concentrating La3+ and polishing monovalent ions from the concentrated solution. Highly negative monovalent-ion rejections greatly enhance this polishing step, and proton concentrations decrease 3–4 orders of magnitude in 2.4 cell volumes of diafiltration. Studies with rotating membranes give a controlled, uniform boundary layer above the membrane to enable estimation of salt and ion permeances at various feed compositions. Insertion of these permeances in the solution-diffusion-electromigration model yields trends in ion rejections as a function of composition, solution flux, and boundary layer thickness. Simulated rejections of monovalent ions become much more negative with lower solution fluxes (up to a point) and higher ratios of La3+ to monovalent ions. La3+ rejections are much higher in the rotating membrane than in a stirred cell where the diffusion boundary layer is thicker and nonuniform. The combination of NF and diafiltration provides concentrated La3+ with a molar purity of 99 % when starting with equimolar mixtures of La3+ and Na+. Acid removal from La3+ solutions via diafiltration could prove useful for subsequent separations among REEs or other transition metals.

Increased activity of epithelial Cdc42 Rho GTPase and tight junction permeability in the Cftr knockout intestine.

Increased intestinal permeability is a manifestation of cystic fibrosis (CF) in people with CF (pwCF) and in CF mouse models. CF transmembrane conductance regulator knockout (Cftr KO) mouse intestine exhibits increased proliferation and Wnt/β-catenin signaling relative to wild-type mice (WT). Since the Rho GTPase Cdc42 plays a central role in intestinal epithelial proliferation and tight junction remodeling, we hypothesized that Cdc42 may be altered in the Cftr KO crypts. Immunofluorescence showed distinct tight junction localization of Cdc42 in Cftr KO fresh crypts and enteroids, the latter indicating an epithelial-autonomous feature. Quantitative PCR and immunoblots revealed similar expression of Cdc42 in the Cftr KO crypts/enteroids relative to WT, whereas pulldown assays showed increased GTP-bound (active) Cdc42 in proportion to total Cdc42 in Cftr KO enteroids. Cdc42 activity in the Cftr KO and WT enteroids could be reduced by inhibition of the Wnt transducer Disheveled. With the use of a dye permeability assay, Cftr KO enteroids exhibited increased paracellular permeability to 3 kDa dextran relative to WT. Leak permeability and Cdc42 tight junction localization were reduced to a greater extent by inhibition of Wnt/β-catenin signaling with endo-IWR1 in Cftr KO relative to WT enteroids. Increased proliferation or inhibition of Cdc42 activity with ML141 in WT enteroids had no effect on permeability. In contrast, inhibition of Cdc42 with ML141 increased permeability to both 3 kDa dextran and tight junction impermeant 500 kDa dextran in Cftr KO enteroids. These data suggest that increased constitutive Cdc42 activity may alter the stability of paracellular permeability in Cftr KO crypt epithelium.NEW & NOTEWORTHY Increased tight junction localization and GTP-bound activity of the Rho GTPase Cdc42 was identified in small intestinal crypts and enteroids of cystic fibrosis (CF) transmembrane conductance regulator knockout (Cftr KO) mice. The increase in epithelial Cdc42 activity was associated with increased Wnt signaling. Paracellular flux of an uncharged solute (3 kDa dextran) in Cftr KO enteroids indicated a moderate leak permeability under basal conditions that was strongly exacerbated by Cdc42 inhibition. These findings suggest increased activity of Cdc42 in the Cftr KO intestine underlies alterations in intestinal permeability.

Trends of water composition and discharge in the Ramganga River, Ganga Basin over the last 40 years signal enhanced nitrate flux

Studying long-term trends in river water chemistry is critical to assessing the impacts of human activities and climate change on water resources. This is of particular importance in the Indian subcontinent such as the Ganga River Basin – home to nearly 500 million people. As previous studies are mostly focused on seasonal to annual scale variabilities, the long-term riverine changes in the hydrochemistry of the rivers draining the Ganga Basin remain poorly constrained. Here we present the river chemistry and discharge data of Ramganga Basin, a major sub-catchment of Ganga River, for three hydrological stations between 1981 and 2020. Our results indicate that the total concentration of dissolved solids (TDS) within the Ramganga basin varies from 123 to 1170 mg/L and does not show a systematic spatiotemporal trend. However, we found that the fluxes of certain dissolved inorganic constituents from Ramganga Basin have significantly increased in the last 40 years with NO3– having the highest trend followed by Ca2+, Cl−, K+, SiO2, F−, and PO43−. The concentration-discharge (C–Q) analysis suggests a dominant dilution behaviour for most of the major solutes in the basin at longer timescales. We find that the cations and anions riverine loads are primarily dominated by Ca2+ and HCO3– ions, respectively, controlled by rock weathering processes, whereas the fluxes of NO3–, PO43−, and SO42− are controlled by anthropogenic processes. In summary, the long-term dataset for the Ramganga River revealed significant variability in river water chemistry, solute fluxes, and C–Q relationships over the last 40 years controlled by natural and anthropogenic processes.