Water Permeability Measurements Research Articles

Establishment of the deuterium oxide dilution method as a new possibility for determining the transendothelial water permeability

Increase in transendothelial water permeability is an essential etiological factor in a variety of diseases like edema and shock. Despite the high clinical relevance, there has been no precise method to detect transendothelial water flow until now. The deuterium oxide (D2O) dilution method, already established for measuring transepithelial water transport, was used to precisely determine the transendothelial water permeability. It detected appropriate transendothelial water flow induced by different hydrostatic forces. This was shown in four different endothelial cell types. The general experimental setup was verified by gravimetry and absorbance spectroscopy. Determination of transendothelial electrical resistance (TEER) and immunocytochemical staining for proteins of the cell-cell contacts were performed to ensure that no damage to the endothelium occurred because of the measurements. Furthermore, endothelial barrier function was modulated. Measurement of transendothelial water flux was verified by measuring the TEER, the apparent permeability coefficient and the electrical capacity. The barrier-promoting substances cyclic adenosine monophosphate and iloprost reduced TEER and electrical capacity and increased permeability. This was accompanied by a reduced transendothelial water flux. In contrast, the barrier-damaging substances thrombin, histamine and bradykinin reduced TEER and electrical capacity, but increased permeability. Here, an increased water flow was shown. This newly established in vitro method for direct measurement of transendothelial water permeability was verified as a highly precise technique in various assays. The use of patient-specific endothelial cells enables individualized precision medicine in the context of basic edema research, for example regarding the development of barrier-protective pharmaceuticals.

Filling of Chitosan Film with Wax/Halloysite Microparticles for Absorption of Hydrocarbon Vapors

AbstractThe effect of the preparation protocol of chitosan (CHI) based films filled with wax microparticles stabilized by halloysite nanotubes (HNTs) in Pickering emulsions (PE) is investigated. The obtained results show that the addition of acetic acid (before or after the preparation of wax/HNT microspheres) affects the properties of the composite films as well as the colloidal stability of PE. The colloidal behavior of CHI/HNT/wax PE by optical microscopy and sedimentation tests are studied. On the other hand, the corresponding composite films (prepared by solvent casting method) are characterized through several techniques, including Scanning Electron Microscopy, UV–vis spectrometer, water permeability, and contact angle measurements. Dynamic Mechanical Analysis allows this to estimate the effect of wax microparticles on the tensile performances of CHI‐based films. As a general consideration, the filling of the CHI matrix with wax/HNT improves the physicochemical properties of the films. Finally, the efficacy of the films as adsorbents of n‐dodecane vapors is explored. Due to the presence of hydrophobic domains (wax embedded in CHI), the composite films possess higher adsorption efficiencies compared to pristine CHI. Accordingly, it can be stated that the combination of CHI with wax/HNT microparticles is promising to obtain biocompatible composite films useful for remediation purposes.

Gas breaktrough behavior of the Spanish reference bentonite


 The Spanish concept for the geological disposal of radioactive waste implies the use of pre-compacted bentonite, as a main component of the engineering barrier system. The reference bentonite, called FEBEX bentonite, is composed mainly of montmorillonite, has a maximum grain size of 5 mm and a hygroscopic water content of ~14.5%. The aim of this work was to determine the gas breakthrough (BT) pressure on saturated samples of this buffer material.
 Samples (20 mm length, 38/50 mm diameter) were uniaxially compacted at 1.5 and 1.6 g·cm-3 dry densities (DD), directly in the test cell. Their water content were from hygroscopic to around 26% (full saturation at 1.6 DD), most of them on the wet side of optimum. Compaction pressures ranged between 7 and 1.4 MPa, depending on target DD, water content and granulometry of the bentonite. To check the effect of the as-compacted macrostructure, we tested three grain size distributions (full <5 mm, 1.18<x<2.0 mm, and 2.83<x<4.7 mm) with similar water content (hygroscopic); and the full grain size distribution with different water contents (around 18, 22 and 26%). Mercury intrusion porosimetry (MIP) on small compacted samples (for different DD and granulometric fractions) showed that the main differences between them were macrostructural, with minor effect on mesostructure.
 A series of long-term gas injection tests were carried out to determine, by constant pressure steps, the BT pressure. Some improvements were introduced in the experimental gas breaktrough (BT) setup and the testing protocol described in [1], including different configurations of gas up and downstream volumes (~150, 75 and 50 cm3), where actual pressure (inlet or outlet) is measured (Fig. 1a). A measurement of gas permeability (on the as-compacted sample) and two injection phases (on the fully saturated sample) configure the BT protocol. Each injection phase consists of a water permeability measurement and a long-term gas injection at increasing/decreasing pressures. The gas injection is intended to elicit at least two BT events (Fig 1b). The cells kept the samples in isochoric conditions during the test: after the saturation phase, the swelling pressure is expected to prevent preferential gas flows between the sample and the cell body. Once the gas injection starts no more water was supplied.
 Gas permeability was measured on as-compacted samples with the high-pressure steady-state setup described in [2, 3]. The measurements of gas outflow and other variables, including RH/Temperature, permit to calculate the gas permeability and to estimate the sample drying induced by gas flow during the test. In these samples, there was a linear relationship of gas flow with the difference of square pressures for all dry densities tested. From these measurements, intrinsic permeability ranged from 10-14 m2 to 10-17 m2 (for 1.5 DD and 1.6 DD).
 The water permeability measurement before the first gas injection phase allows to obtain a base-line value; the one after gas injection allows to determine if the sealing capacity was compromised by the previous BT events. Average values were in the range (0.7 – 2.0)·10-18 m2.
 After [1], the air entry pressure for the FEBEX compacted bentonite is around 25 MPa (for DD 1.6). BT pressures determined in this work were much lower than this value and close to the upper range of the expected swelling pressure, that controls the gas entry and the breakthrough events. Local variations in the swelling pressure due to several factors (material heterogeneity, change in suction, temperature, stress) can direct the high-pressure gas through preferential local paths.
 The BT events on pressure-time curves showed a consistent and systematic repetition of BT values (Fig 1b); they had different shapes depending on whether the injection pressure was greater than, close to or just less than the actual BT pressure; and changes in the slope of the curves could indicate different types of flow and the underlying physical concept (from microfracturing, in the case of the instantaneous episodes, to microscopic pathway dilation for the gradual ones).
 BT pressures increased with increasing dry density and water content (initial saturation degree) at compaction (considered as initial microstructural state); and the geometry of the sample (decreasing L/D ratio). The BT behavior is considered as a characteristic of a given liquid-solid system (sample): related to the initial state after compaction and the preservation of their structure during the test, at a specified temperature. Changes affecting the structure will affect the BT pressure.
 Gas migration in saturated FEBEX bentonite at DD<1.6 was interpreted to occur by the formation and propagation of dilatant pathways.

Evaluating the accuracy of liquid permeability measurements in shale and tight rocks using transient flow method and comparison with gas permeability

The transient flow method for measuring permeability to liquid is a useful technique for shale and tight rocks; however, it is not as popular as the steady-state method in these rocks. One of the issues is the lack of clarity on a key term of compressibility of the fluid and rock system. Various forms of compressibility have been used in literature, which can lead to inconsistent results of liquid permeability. Using gas for the permeability measurement is more common in shale, and the Klinkenberg corrected permeability is often used to represent liquid permeability; however, how the Klinkenberg permeability is compared to liquid permeability in shale or tight rocks is not adequately addressed. This paper presents a study using the transient flow method for water and oil permeability measurement in three Eagle Ford Shale samples. Gas permeability was also measured for these samples. Different forms of the total compressibility of the fluid-rock system (Ct) are summarized from literature, and a new form of Ct is proposed. The accuracy of the calculations based on different forms of Ct is evaluated through the comparison between water and oil permeabilities and the comparison with gas permeability. The results are also compared with oil permeability obtained from the steady-state method. The new form of Ct provided the most accurate results, whereas the other forms of Ct led to errors. However, for samples with bulk compressibility of less than 1 × 10−7 psi−1, the error using those forms of Ct was negligible. The study also found that the Klinkenberg permeability obtained from the linear extrapolation is larger than the oil permeability for two samples by 12% and 37%, respectively, whereas it is smaller than the oil permeability for the other sample. This comparison suggests that a nonlinear gas slippage effect may exist in the high pressure range (>2000 psi) for shale or tight rock samples.

The different impacts of g‐C3N4 nanosheets on PVDF and PSF ultrafiltration membranes for Remazol black 5 dye rejection

AbstractMembranes combined with nanoparticles are an excellent combination capable of successfully removing various contaminants, such as dyes from wastewater while using very little energy and decreasing pollution. The present study reports an efficient approach for Remazol Black 5 (RB5) dye removal using composite graphitic carbon nitride nanosheets (g‐C3N4), polysulfone (PSF), and polyvinylidene fluoride (PVDF) membranes. The membranes were prepared using the phase inversion method, with varying quantities of g‐C3N4 nanosheets ranging from 0.1%, 0.2% to 0.3%. The prepared g‐C3N4 nanosheets were characterized by FTIR, SEM analyses, and zeta potential measurements. FTIR and SEM studies, contact angle, water permeability, COD, and dye rejection measurements were used to characterize the g‐C3N4 nanosheets embedded in PSF and PVDF membranes. After the addition of 0.3 wt% g‐C3N4, the water flux of the 0.3 wt% g‐C3N4 embedded PSF membrane was the highest, whereas the water flux of the 0.3 wt% g‐C3N4 embedded PVDF membrane was the lowest. The ultrafiltration (UF) membrane's performance with g‐C3N4 embedded showed an RB5 rejection rate of more than 80% and a COD removal efficiency of more than 45%. The results of the experimental filtration showed that RB5 rejection reached maximum values of 91.3% for 0.1 wt% g‐C3N4/PSF, and 85.6% for 0.3 wt% g‐C3N4/PVDF.

Entropic barrier of water permeation through single-file channels

Facilitated water permeation through narrow biological channels is fundamental for all forms of life. Despite its significance in health and disease as well as for biotechnological applications, the energetics of water permeation are still elusive. Gibbs free energy of activation is composed of an enthalpic and an entropic component. Whereas the enthalpic contribution is readily accessible via temperature dependent water permeability measurements, estimation of the entropic contribution requires information on the temperature dependence of the rate of water permeation. Here, we estimate, by means of accurate activation energy measurements of water permeation through Aquaporin-1 and by determining the accurate single channel permeability, the entropic barrier of water permeation through a narrow biological channel. Thereby the calculated value for triangle {S}^{{{ddagger}} } = 2.01 ± 0.82 J/(mol·K) links the activation energy of 3.75 ± 0.16 kcal/mol with its efficient water conduction rate of ~1010 water molecules/second. This is a first step in understanding the energetic contributions in various biological and artificial channels exhibiting vastly different pore geometries.

Thermo‐Responsive Ultrafiltration Block Copolymer Membranes Based on Polystyrene‐block‐poly(diethyl acrylamide)

AbstractWithin the present work, a thermo‐responsive ultrafiltration membrane is manufactured based on a polystyrene‐block‐poly(diethyl acrylamide) block copolymer (BCP). The poly(diethyl acrylamide) block segment features a lower critical solution temperature (LCST) in water, similar to the well‐known poly(N‐isopropylacrylamide), but having increased biocompatibility and without exhibiting a hysteresis of the thermally induced switching behavior. The BCP is synthesized via sequential “living” anionic polymerization protocols and analyzed by 1H‐NMR spectroscopy, size exclusion chromatography, and differential scanning calorimetry. The resulting morphology in the bulk state is investigated by transmission electron microscopy (TEM) and small‐angle X‐ray scattering (SAXS) revealing the intended hexagonal cylindrical morphology. The BCPs form micelles in a binary mixture of tetrahydrofuran and dimethylformamide, where BCP composition and solvent affinities are discussed in light of the expected structure of these micelles and the resulting BCP membrane formation. The membranes are manufactured using the non‐solvent induced phase separation (NIPS) process and are characterized via scanning electron microscopy (SEM) and water permeation measurements. The latter are carried out at room temperature and at 50 °C revealing up to a 23‐fold increase of the permeance, when crossing the LCST of the poly(diethyl acrylamide) block segment in water.

An impedance based microfluidic sensor for evaluation of individual red blood cell solute permeability

—In this paper, we investigate a microfluidic based sensing device for cell membrane permeability measurements in real time with applications in rapid assessment of red blood cell (RBC) quality at the individual cell level. The microfluidic chip was designed with unique abilities to line up the RBCs in the centerline of the microchannel using positive dielectrophoresis (p-DEP) forces, rapid mixing of RBCs with various media (e.g. containing permeating or nonpermeating solutes) injected from different inlets to achieve high mixing efficiency. The chip detects the impedance values of the RBCs within 0.19 s from the start of mixing with other media, at ten electrodes along the length of the channel and enables time series measurements of volume change of individual cell caused by cell osmosis in anisosmotic fluids over a 0.8 s postmixing timespan. This technique enables estimating water permeability of individual cell accurately. Here we first present confirmation of a linear voltage-diameter relationship in polystyrene bead standards. Next, we show that under equilibrium conditions, the voltage-volume relationship in rat red blood cells (RBCs) is linear, corresponding to previously published Boyle van ‘t Hoff plots. Using rat cells as a model for human, we present the first measurement of water permeability in individual red blood cells and confirm that these data align with previously published population level values for human RBC. Finally, we present preliminary evidence for possible application of our device to identify individual RBCs infected with Plasmodium falciparum malaria parasites. Future developments using this device will address the use of whole blood with non-homogenous cell populations, a task currently performed by clinical Coulter counters.

Water Permeability Measurements by Steady-State and Pulse Decay Methods on the Callovo-Oxfordian Claystone and Impact on its Mechanical Properties

Water Permeability Measurements by Steady-State and Pulse Decay Methods on the Callovo-Oxfordian Claystone and Impact on its Mechanical Properties

Evaluation of the original sealant with antibacterial effect for synthetic vascular grafts

Background: Vascular graft infection is a severe cardiovascular complication with high mortality rates. Antibacterial vascular graft coatings are widely used and continue to be improved.Objective: To develop a sealant with antimicrobial effect for Dacron vascular grafts and experimentally test the coating properties.Methods: We used 2 types of vascular grafts: graft No. 1 (plain weave) with initial water permeability of 78.8 ± 2.7 mL/cm2/min and graft No. 2 (2/1 twill + 6/4 satin weave) with water permeability of 549.8 ± 20.7 mL/cm2/min. We developed an original gelatin impregnation technique, tested it using a scanning electron microscopy, and measured water permeability and kink radius. We evaluated the antibacterial activity of vancomycin and gelatin impregnation by the disk diffusion test using media with Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 and measured inhibition zones after 24-hour incubation. We used samples cut out of grafts with vancomycin-containing (experimental group) and no vancomycin-containing (control group) impregnation.Results: The gelatin coating of the samples is visualized as a thin even film and provides zero water permeability. On the negative side, it increased stiffness and the kink radius. Thanks to vancomycin added to the coating, bacterial growth significantly inhibits: the mean diameter of the growth inhibition zone for Staphylococcus aureus and Enterococcus faecalis was 15.60 ± 0.65 and 14.40 ± 0.66 mm, respectively. The grafts untreated with vancomycin showed no growth inhibition zones.Conclusion: Vascular graft treatment with gelatin impregnation and vancomycin solution is a simple measure to prevent the growth of gram-positive bacteria on vascular grafts. Received 14 November 2022. Revised 15 December 2022. Accepted 19 December 2022. Funding: The work was supported by Russian Science Foundation (project No. 22-15-20005). Conflict of interest: The authors declare no conflict of interest. Contribution of the authorsConception and study design: I.Yu. Zhuravleva, A.A. Shadanov, D.A. SirotaData collection and analysis: A.A. Shadanov, L.M. Samoylova, S.V. Vladimirov, T.P. Timchenko, N.E. Luchnikov, E.V. KarpovaStatistical analysis: A.A. ShadanovDrafting the article: A.A. Shadanov, L.M. Samoylova, T.P. Timchenko, A.G. EdemskiyCritical revision of the article: D.A. Sirota, I.Yu. Zhuravleva, A.V. Bogachev-Prokofiev, A.M. ChernyavskiyFinal approval of the version to be published: A.A. Shadanov, I.Yu. Zhuravleva, L.M. Samoylova, T.P. Timchenko, S.V. Vladimirov, E.V. Karpova, N.E. Luchnikov, D.A. Sirota, A.G. Edemskiy, A.V. Bogachev-Prokofiev, A.M. Chernyavskiy

Methods to Measure Water Permeability.

Water permeability is a key feature of the cell plasma membranes, and it has seminal importance for several cell functions such as cell volume regulation, cell proliferation, cell migration, and angiogenesis to name a few. The transport of water occurs mainly through plasma membrane water channels, aquaporins. Aquaporins have very important function in physiological and pathophysiological states. Due to the above, the experimental assessment of the water permeability of cells and tissues is necessary. The development of new methodologies of measuring water permeability is a vibrant scientific field that constantly develops during the last three decades along with the advances in imaging mainly. In this chapter we describe and critically assess several methods that have been developed for the measurement of water permeability both in living cells and in tissues with a focus in the first category.

Pengaruh Variasi Campuran Bentonit Terhadap Karakteristik Pasir Cetak Untuk Proses Sand Casting

The casting process is widely used because it has the advantage of being able to make products with small dimensions to very large dimensions, the use of materials is more efficient, the casting products can be directly used. However, in the casting process, the main triggers for the formation of defects are the nature of the mold, low permeability, low molding compressive strength, low sintering point, unsuitable sand grain distribution, so research is needed to obtain the right type of molding sand as a sand mold in metal casting. The only type of additive is bentonite. Bentonite can absorb water and expands between 8-15 times and remains dispersed in water for a certain period of time. This study aims to examine the effect of a mixture of variations of local bentonite and Australian bentonite on the characteristics of the molding sand for the sand casting process. The tests carried out are in the form of size distribution testing, X-Ray Diffraction, water content testing, compressive strength, and permeability measurements. Bentonite was varied into 5 variations of the mixture with a difference of 20% in each mixture. The results of the large size distribution of silica sand grains were 37.6 GFN. The results of XRD testing of local bentonite showed a higher content of calcium compounds and Australian bentonite contained higher sodium compounds. The largest water content test value is 5.825%. The largest compressive strength test value is 2.7 Kgf /cm 2 .

Ni-Zn metal-organic framework based membranes for rejection of Pb(II) ions

The present paper describes a sustainable and affordable supply of clean, and safe water approach to investigate Ni-Zn MOF embedded membrane for rejection of Pb (II) ions in aqueous solution. Ni-Zn MOF powder was prepared by solvo-thermal method, and then the Ni-Zn MOF embedded membranes with various concentrations (0.025 wt%, 0.05 wt% and 0.1 wt%). The membranes were fabricated by a common phase inversion method. Phase solutions of Pb(II) prepared with PVP at different concentrations in aqueous solutions. Water filtration and Pb (II) rejection tests were operated on a batch scale. The prepared Ni-Zn MOF powder characterized by FTIR, SEM-EDX analyses and zeta potential measurements. Ni-Zn MOF membranes were characterized by FTIR, SEM-EDX analysis, contact angle, and water permeability measurements. The effects of important parameters on adsorption including concentration and pH were investigated. The obtained results indicated that the maximum rejection of Pb(II) was 98% for a feed solution containing 80 mg Pb/L at pH 8 and assistance with 2 % PVP for 0.05 wt% Ni-Zn MOF membrane. Additionally, it was detected that blend membranes revealed better Pb(II) rejection than pure PSF membrane.

Treatment of dairy wastewater with tubular ceramic membrane

This work illustrates the fabrication of tubular ceramic membrane with extrusion machine using low cost clay materials such as kaolin, quartz, CaCO3, boric acid, feldspar and carboxymethyl cellulose. The raw membrane was kept at ambient temperature for 24 hrs. It is sintered at 950 °C at a heating rate of 0.5 °C per minutes for 6 hrs in stepwise muffle furnace. The fabricated membrane is characterized with pure water permeability and porosity measurement. The pore size of 1.49 µm and permeability of 5.438 × 10−8 m/s.kPa are obtained from pure water permeability test. The tubular membrane was tested for dairy wastewater at different pressure (13.79–55.16 kPa) on a microfiltration range. With increase in the applied pressure the removal rate of chemical oxygen demand (COD) decreases showing optimum removal of 52.08 % at a low pressure of 13.08 kPa. Along with the COD determination, various parameters of the dairy wastewater were also measured like pH, conductivity and turbidity. The obtained pH, conductivity and turbidity of feed are 7.11, 2 mS/cm and 45 NTU respectively. Moreover, the prepared tubular membrane was examined for the fouling mechanism using four conventional pore blocking models.

Assessment of Durability Indicators for Service Life Prediction of Portland Limestone Cementitious Systems Produced with Permeability-Reducing Admixtures

Supplementary cementing materials (SCMs) and the challenges associated with admixture compatibility and durability performance are continuous challenges for the construction industry. Utilizing SCMs has apparent benefits in reducing the carbon footprint and improving the durability performance of concrete structures. This work investigates the performance of mortars composed of Portland limestone cement, calcium carbonate, butyl stearate, and oleic acid. The effort focuses on transport properties using electrical resistivity, chloride migration, porosity, and water permeability measurements. Then, various methods based on the last parameters are compared to assess the changes in the effective chloride diffusion coefficient and the intrinsic liquid water permeability. Measurements for drying shrinkage, thermal expansion, and compressive strength are conducted to verify durability and mechanical performance. The effect of the admixture addition on the service life of a structure fully submerged in marine exposure conditions is then evaluated using Fick’s second law of diffusion and the approach described by FIB model code 34. The results indicate that incorporating calcium carbonate, butyl stearate, and oleic acid in mortar mixtures provides enhanced durability compared to plain Portland limestone cement mortars.

Fabrication of ball clay based low-cost ceramic membrane supports and their characterization for microfiltration application

In this study, the uniaxial pressing method was employed to fabricate low-cost ceramic membrane supports using inexpensive clays for microfiltration applications. The primary precursors used to make different membrane supports (S1–S3) were Ball clay and China clay. Thermogravimetric analysis (TGA), particle size distribution (PSD), contact angle measurements, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were performed in addition to water flux, porosity, water permeability, and average pore size measurements to characterize the membrane. SEM analysis revealed that the surface morphology of the membrane supports varies significantly depending on the raw material composition. The contact angle analysis of the supports revealed that they are hydrophilic, which is suitable for microfiltration applications. The water permeability, average pore size, and porosity of the membrane supports (S1–S3) were 4.31 × 10−6 – 2.77 × 10−6 m3/m2s kPa, 1.18–0.31 μm, 44–41%, respectively. Furthermore, the membranes' high pH and chlorine resistance show their suitability for use in harsh chemical cleaning. The production cost of membranes based on raw materials, pressing, and sintering was estimated to be Rs.1319/m2 ($17.07), Rs. 978/m2 ($12.66) and Rs. 924/m2 ($11.96) for the supports S1, S2, and S3, respectively. Thus, membrane supports with low-cost clay materials are now suggested for microfiltration applications.

Comprehensive evaluation of self-healing of concrete with different admixtures under laboratory and long-term outdoor expositions

This project presents the evaluation of the self-healing of fibre reinforced concretes containing various admixtures (crystalline admixture CA, expansive agent CSA, superabsorbent polymer SAP) and combinations. They were exposed to several laboratory conditions (water immersion, wet/dry cycles ambient air for 3 months, water flow for 1 week) and to a long-term outdoor exposure for 1 year. Self-healing capacity was assessed by water permeability measurements, mechanical recovery, visual observations and microscopic analyses on the same specimen. This paper presents the mechanical behaviour and microstructure of the healing products, and the correlations with the water permeability measures presented in previous research. The results showed that a high healing of cracks based on water permeability did not necessarily lead to a high mechanical recovery. The highest Strength Regains (109% in average) were obtained for specimens exposed outdoor that presented the lowest Healing Ratios (71% in average). The local density of the healing products may govern the Healing Ratio, while the type of healing products and their extent in the crack depth may control the Strength Regain. Finally, the SAP mix showed overall the best self-healing performance, regarding both durability and mechanical properties.

Separation of Drugs by Commercial Nanofiltration Membranes and Their Modelling.

Pharmaceutical drugs have recently emerged as one the foremost water pollutants in the environment, triggering a severe threat to living species. With their complex chemical nature and the intricacy involved in the removal process in mind, the present work investigates the performance of commercially available polyamide thin-film composite tubular nanofiltration (NF) membranes (AFC 40 and AFC 80) in removing polluting pharmaceutical drugs, namely caffeine, paracetamol and naproxen. The structural parameters of the NF membranes were estimated by water permeability measurements and retention measurements with aqueous solutions of organic, uncharged (glycerol) solutes. The effect of various operating conditions on the retention of solutes by the AFC 40 and AFC 80 membranes, such as applied transmembrane pressure, tangential feed flow velocity, feed solution concentration and ionic strength, were evaluated. It was found that the rejection of drugs was directly proportional to transmembrane pressure and feed flow rate. Due to the size difference between caffeine (MW = 194.9 g/mol), naproxen (MW = 230.2 g/mol) and paracetamol (MW = 151.16 g/mol), the AFC 40 membrane proved to be efficient for caffeine and naproxen, with rejection efficiencies of 88% and 99%, respectively. In contrast, the AFC 80 membrane proved to be better for paracetamol, with a rejection efficiency of 96% (and rejection efficiency of 100% for caffeine and naproxen). It was also observed that the rejection efficiency of the AFC 80 membrane did not change with changes in external operating conditions compared to the AFC 40 membrane. The membrane performance was predicted using the Spiegler–Kedem model based on irreversible thermodynamics, which was successfully used to explain the transport mechanism of solutes through the AFC 40 and AFC 80 membranes in the NF process.

Preparation of α-alumina/γ-alumina/γ-alumina-titania ceramic composite membrane for chloride ion removal

It is a universally acknowledged truth that ceramic membranes with high heat and chemical resistance play a crucial role in the nanofiltration (NF) process under harsh conditions. Although the ceramic membranes are challenging to use for salt filtration due to pore size and surface charge constraints. In this study, sol-gel and dip-coating techniques are used to make alumina–titania composite ceramic membranes with an γ-alumina interlayer for salt rejection. Then, particle size distribution was determined using dynamic light scattering (DLS), and membrane surface quality and morphology were examined using scanning electron microscopy (SEM). The microstructural properties of the membrane have been investigated using X-Ray Diffraction (XRD). A dead-end module is used to measure water permeability and salt rejection. After calcination at 450 °C, SEM shows the crack-free membrane surfaces. The interlayer and top layer membrane thicknesses were estimated to be 1.5 and 0.5 μm, respectively. In addition, XRD measurements show an alumina crystal structure for the interlayer and anatase, rutile, and alumina phases for the composite membranes. Finally, it was shown that the amount of chlorine rejection was pH-dependent, with the rejection rate increasing from 12.7% to 67% as the pH climbed from 4 to 12. Overall, this research provides a composite ceramic nanofiltration for high-pressure desalination, and it is shown that the membrane's surface does not alter after five cycles, which allows for a long-term chemical process and it could be a promising candidate in the wastewater treatment field.

Self-healing of concrete containing different admixtures under laboratory and long-term real outdoor expositions based on water permeability test

This work assessed the self-healing capacity of fibre reinforced concretes containing different admixtures (crystalline admixture CA, expansive agent CSA and superabsorbent polymer SAP) and submitted to different exposure conditions in laboratory (water immersion, wet/dry cycles and ambient air for 3 months, water flow for 1 week) as well as a long-term real outdoor exposition (1 year in Montreal climate). Self-healing was assessed by water permeability measurements performed on prisms presenting a realistic flexural macrocrack. The results, presented in Healing Ratio and equivalent crack width, showed different self-healing kinetics and efficiency according to the mix composition, but especially to the exposition. The average final Healing Ratios reached 84% in water, 93% in wet/dry cycles and 71% in water flow and in real outdoor exposure. The SAP and CA mixes presented the best healing performance in real outdoor condition. No synergetic effect was found when combining CA+CSA and CA+SAP. Additional microscopic analyses showed different healing products according to the exposition.