Decrease In Permeability Research Articles

Transforming end-of-life SWRO desalination membranes into nanofiltration membranes for the treatment of brackish water and wastewater

In this study, we explore the possibility of reusing end-of-life seawater reverse osmosis (RO) membranes to treat brackish water and industrial effluent. Prior to cleaning the end-of-life RO membranes, we conducted several autopsies in order to assess the extent of degradation. Based on these results, three cleaning protocols were tested and Ultrasil10 and/or chlorine solution were selected for further investigation. The cleaning capacity of the chlorine treatment at 4000 ppm.h was tested but proved inefficient as it leads to a denser cake and a significant decrease in hydraulic permeability. Therefore, we recommend commencing chemical cleaning with Ultrasil10 to remove foulants, thereby reconditioning the end-of-life RO membranes to meet nanofiltration membrane specifications. The cleaned end-of-life RO membranes exhibited enhanced hydraulic permeability (1.97 L·h⁻¹·m⁻²·bar⁻¹) and achieved a salt rejection of 85% for brackish water (6 g/L NaCl). With a molecular weight cutoff of 86 Da, these membranes effectively reduced brackish water conductivity to below 1000 µS/cm at 10 bars, complying with Tunisian drinking water standards (300–2500 µS/cm). Additionally, they demonstrated high efficiency in treating industrial effluents, achieving turbidity levels below 2 NTU and conductivity of 180 µS/cm. Operating at lower pressures, these membranes provided cost-effective, sustainable solutions and performed comparably to commercial new NF membranes, validating their potential for reuse in brackish water and wastewater treatment applications.

Effect of pore throats on the reservoir quality of tight sandstone: A case study of the Yanchang Formation in the Zhidan area, Ordos Basin

Abstract Due to the tight sandstone widespread development of nanoscale pore-throat systems, the microscopic pore-throat characteristics of tight reservoirs are the focus of research. Taking the main tight oil production province of the Ordos Basin in China as a case study, nuclear magnetic resonance (NMR), pressure-controlled mercury injection (PMI), scanning electron microscopy, and micro-computed tomography (μCT) are used to analyze the characteristics of four types of tight sandstones with different pore throats. Furthermore, the effects of pore throats on movable fluid, connectivity, and reservoir physical properties are analyzed. The results show that the pore throats of the four types of tight sandstones are obviously different, but they are all dominated by nanoscale pore-throat systems. From types I to IV, the pore types of the tight sandstone change from residual intergranular pores to the coexistence of feldspar dissolved pores and residual intergranular pores and then to the coexistence of residual intergranular pores and intergranular micropores. The T 2 NMR spectrum changes from a double peak to a single peak, the pore-throat connectivity revealed by μCT decreases from 83.8% for type I to 13.1% for type IV, the pore-throat volume ratio revealed by PMI decreases from 2.09 to 0.43, and the NMR movable fluid saturation decreases from 38.91 to 12.39%. Tight sandstone with larger pores and a uniform distribution has high movable fluid saturation and good pore-throat connectivity. Although the tight sandstone with dissolved pores and intergranular pores may have a medium porosity, the pore–throat connectivity deteriorates compared with high porosity sandstone. Large pore throats, which account for less than 15% of all pore throats, contribute more than 90% of the permeability, while pore throats less than 0.8 μm in diameter are major contributors to the reservoir space, and both the porosity and permeability decrease as the pore-throat diameter decreases.

P-441. Gut Permeability Response to Inulin Supplementation in Well-Controlled HIV Patients with Metabolic Syndrome

Abstract Background HIV infection is known to cause abnormally increased gut permeability resulting in chronic inflammation. Serum levels of Zonulin protein are elevated in persons with increased gut permeability. The objective of this study is to assess whether Inulin (fiber) supplementation will result in a decrease in gut permeability in well-controlled HIV patients with metabolic disorder as measured by baseline and post-intervention Zonulin levels. Statistical Results There was a statistically significant increase in median Zonulin levels from baseline to post-intervention (p=0.002) Methods 10 subjects were selected from patients enrolled in care at the Center for AIDS Research and Treatment (CART) based at North Shore University Hospital. Eligibility criteria included well-controlled HIV patients with evidence of metabolic syndrome. The duration of the study was 6 weeks and the intervention was Inulin supplement use. Bloodwork drawn pre- and post-intervention included Zonulin levels, A1c, Fructosamine, Cholesterol, Triglycerides, HDL, LDL, and non-HDL levels. BMI was also checked. Patients were provided with organic Inulin powder and instructed to take 1 tablespoon once a day for the first week and advance to twice a day for the rest of the study. Every week patients were contacted via telephone to assess compliance and side effects. The primary endpoint was the assessment of baseline and post-intervention Zonulin levels, with the secondary endpoint including baseline and post-intervention BMI, A1c, Fructosamine and Lipids. Descriptive statistics were computed and significance was determined via Wilcoxon signed-rank test. Pre and Post Intervention Zonulin levels in all 10 subjects Results Among the patients enrolled 80% were male, 60% were White, 80% were not Hispanic or Latino, and the median age was 60.5. Flatulence and bloating were the most frequent side effects of inulin reported. The median Zonulin levels at baseline were 177.9µg/mL, and post-intervention were 532.4µg/mL. There was a statistically significant increase in Zonulin levels from baseline to post-intervention (p=0.002). There was no significant difference between baseline and post-intervention for any of the other parameters in the dataset. Conclusion Inulin supplementation resulted in a statistically significant increase in Zonulin levels, which goes against our hypothesis. Whether this is due to underlying worsening of pre-existing gut dysbiosis or other factors needs further study. Disclosures All Authors: No reported disclosures

Experimental study on the influencing factors and pore production law of CO2 huff-and-puff in tight sandstone reservoirs

In order to determine the influence of different factors on the CO2 huff-and-puff displacement effect, a CO2 huff-and-puff experiment was carried out with Chang 6 tight sandstone samples in Ordos Basin as the research object. Combined with nuclear magnetic resonance technology, the influences of injection pressure, cycle numbers and soaking time on the CO2 huff-and-puff effect were evaluated, and the optimal CO2 huff-and-puff parameters were optimized. The microscopic degree of crude oil production in different scale pores was quantitatively characterized. The results show that the injection pressure and the cycle numbers have a significant influence on the effect of CO2 huff-and-puff. With the increase of injection pressure, huff-and-puff cycle numbers and soaking time, the recovery efficiency increases, but the growth range decreases. When the injection pressure is increased from 6 to 12MPa, the degree of pore mobilization in the oil in macro and medium pores (≥ 10ms) increases by 13.0%-22.63%. The recovery efficiency of a single round gradually decreased with the increase of huff-and-puff rounds. The first cycle of CO2 huff-and-puff was the main contribution of crude oil recovery. However, the production effect of micro and small pores (< 10ms) was significantly improved after multiple cycle numbers of CO2 huff-and-puff. When the soaking time increases from 6 to 24h, the recovery efficiency increases by 11.47%-14.93%. After that, the influence of prolonged soaking time on the porosity production degree of cores with different permeability decreases. It is found that medium pores and macro pores are the main contributors to pore mobilization during multiple cycles of CO2 huff-and-puff.

Effect and mechanism of the moisture content on the kinetic retardation of LNAPL pollutant migration by the capillary zone.

Light nonaqueous-phase liquids (LNAPLs) are the main source of organic pollution in soil and groundwater environments. The capillary zone, with varying moisture contents, is the last barrier against the infiltration of LNAPL pollutants into groundwater and plays an important role in their migration and transformation. However, the effect and mechanism of the moisture content in the capillary zone on LNAPL pollutant migration are still unclear. Herein, to explore the effect of the moisture content on LNAPL pollutant migration, a series of sandbox migration experiments were simulated using diesel oil as a typical LNAPL pollutant and the capillary zones of fine and silty sand as research objects. Several numerical models were constructed based on the recorded migration process of LNAPL pollution fronts in the capillary zones of different media during experiments. The mechanism by which the moisture content in the capillary zone retarded LNAPL pollutant infiltration was revealed using a combination of the construction method of microstructural pores and the theory of multiphase flow. These findings unequivocally indicate that an increase in the moisture content leads to a decrease in the relative permeability of the NAPL phase in unsaturated media, which is the fundamental reason for the retarded kinetic migration of LNAPL pollutants. The results of this study lay a solid foundation for designing comprehensive and effective remediation strategies for LNAPL contamination in soil and groundwater.

Modern legal problems of restoration of lands damaged as a result of military operations

Military actions have had a global negative impact on the land and soil of Ukraine as a whole, causing widespread contamination and degradation. Daily airstrikes and shelling leave deep craters, heavy metals from shells and military equipment penetrate the soil and groundwater, soil permeability decreases, oxygen is displaced, biochemical and microbiological processes are disrupted, vast areas are scorched by fires, and the risk of toxic waste emissions from industrial enterprises in temporarily occupied territories of Ukraine increases. Additionally, there is massive flooding of closed and war-damaged mines. Furthermore, Ukraine is the most mined country in the world. Unfortunately, this list is not exhaustive. The restoration of Ukrainian land and soil is one of the priority tasks in the post-war period, as it affects not only the ecological safety of the state but also its economic stability and development. Given the scale of the problems facing Ukraine, a comprehensive approach is needed, including legal, technological, and organizational support for land restoration. Important stages in this process are the assessment of the degree of damage, the development of an effective methodology for damage compensation, the implementation of modern technologies, the development and implementation of new regulations governing land restoration procedures, and the establishment of clear standards for soil quality. Ukraine also needs to take into account the experience of other countries in land restoration after military conflicts, particularly those that have applied innovative approaches and modern technologies for soil rehabilitation. This will help implement the best practices and restoration methods, ensuring effective and rapid land recovery. International cooperation and support will play a crucial role in this process, as the issue of restoring land and soil damaged by war is not only a domestic matter for Ukraine but also a challenge for the entire global community. Successful examples of land restoration in other countries demonstrate Ukraine’s readiness and ability to cope with the consequences of war and ensure sustainable development in the future, which is a priority task on which Ukraine’s future depends. Considering environmental, economic, and social aspects in the restoration process will allow not only to restore soil fertility but also to create conditions for sustainable development and prosperity of the country.

Experimental Study on Permeation of Composite Grout with Multi-Particle-Size Distribution: Comparative Analysis with Nano-Silica Sol and Cement Grout

The low injectability and strong permeation of micro-fractures in argillaceous rock masses significantly impair the impermeabilization and reinforcement performance of conventional cement-based grouting materials. This study first develops a highly injectable and high-strength nano-silica sol-based composite grout. Then, the characteristics of silica sol, cement grout, and composite grout in argillaceous fractured rock masses are analyzed and compared. The permeation mechanism of the composite-grout grouting in these rock masses is preliminarily elucidated, and the grouting process is described in detail, showing its application prospects. The research results indicate the following: (1) The electrical conductivity and stone-formation rate of granular pulp can reflect the characteristics of pulp filtration. Silica sol is a grouting material with nanometer particles, and the stone rate and gel strength are weakly affected by rock mass infiltration. (2) A large amount of water cannot be combined into the gel network and separated during the cement slurry percolation process, resulting in a significant reduction in the stone rate and compressive strength of deep rock mass. The minimum stone rate decreased to 45.19%, and the minimum compressive strength decreased to 2.29 MPa. This reduces the sealing and reinforcement effect of cement grouting on deep rock masses. (3) Rock permeation primarily affects the compressive strength of the formed stones, with minimal impact on the stability and stone-formation rate of the composite grout. As permeability decreases, the position of rock permeation shifts closer to the rock surface, while the sealing of deeper rock masses is less affected, enabling the composite grout to achieve dual functions of superficial reinforcement and deep sealing. This study provides theoretical support for the practical application of composite-grout grouting in reinforcing argillaceous rock masses.

Cellular Senescence Contributes to the Dysfunction of Tight Junctions in Submandibular Glands of Aging Mice.

The current mechanism by which aging reduces salivary secretion is unknown. This study investigates the mechanism of aging-related submandibular (SMG) dysfunction and evaluates the therapeutic potential of dental pulp stem cell-derived exosomes (DPSC-exos). We found that the stimulated salivary flow rate was significantly reduced in naturally aging and D-galactose-induced aging mice (D-gal mice) compared to control mice. Acinar atrophy and periductal fibrosis in SMGs and parotid glands (PGs) were observed in naturally aging and D-gal mice, whereas sublingual glands (SLGs) had no notable alterations. We observed the accumulation of senescent cells in the SMGs, along with a decrease in claudin-3 (Cldn-3) expression and alterations in the distribution of Cldn1 and Cldn3. Additionally, after D-gal-induced senescence of SMG-C6 cells, there was a decrease in paracellular pathway permeability, reduced expression of Cldn3 and occludin, and changes in the distribution of Cldn1, 3, 4, and 7. Furthermore, injecting DPSC-exos into the SMGs of D-gal mice improved stimulated salivary flow rate, reduced acinar atrophy, and decreased SA-β-gal activity. Our study identified that increased senescence of SMGs in aging mice can cause a decrease in salivary secretion by disrupting the expression and distribution of tight junction molecules, and injection of DPSC-exos ameliorates SMG secretory dysfunction. These findings may provide new clues to novel therapeutic targets for aging-related dysfunction of SMGs.

Dynamics change of coal methane adsorption/desorption and permeability under temperature and stress conditions

Methane adsorption/desorption and permeability measurements are critical for evaluating reserves and production potential in coalbed methane (CBM) extraction. The varying temperature and stress in CBM wells have an impact on these characteristics. To understand these effects, take the Wenjiaba mining area and the Qinglong mining area in Guizhou, China, as the research objects, which are called WJB and QL for short. Characterizing the coal's surface area and pore structure using low-field nuclear magnetic resonance and low-temperature nitrogen adsorption is essential for methane flow and storage. The coal's adsorptive capacity under in situ conditions was revealed by isothermal methane adsorption tests conducted at pressures ranging from 0 to 18 MPa at different temperatures. Triaxial stress-controlled adsorption experiments simulated the impact of effective stress on methane adsorption. Stress-permeability tests evaluated the stress sensitivity and its effect on the coal's methane transmission ability, a key factor in CBM well producibility. The results showed that increased temperature reduced adsorption capacity for WJB and QL coals by 14.2% and 16.3%, respectively, while desorption rates and diffusion coefficients increased, suggesting that higher temperatures enhance desorption and diffusion. However, higher coal ranks can hinder desorption. Effective stress application led to over a 90% decrease in both adsorption capacity and permeability, emphasizing the need for stress management in CBM extraction. These insights provide a theoretical framework for the interplay between coal's pore structure, adsorption/desorption properties, and permeability under different stress and temperature conditions, guiding the optimization of CBM extraction strategies for efficient and sustainable methane recovery.

Hydrogel film synthesis for biowrapping via a single-cycle freeze-thaw process untilizing carboxymethyl cellulose/microcrystalline cellulose and citric acid as crosslinker

Crosslinking will be critical in producing the desired hydrogel with good absorption and high mechanical strength properties. Despite chemical crosslinking, the physical technique of freeze-thaw has reduced chemical use. This research determined the appropriate formulation of CMC/MCC and citric acid concentration using the freeze-thaw method of one cycle and drying to produce hydrogel with high water absorption and mechanical strength. The research findings showed that the hydrogel film created for biowrapping must have high absorption capacity and mechanical strength. This was achieved using a CMC/MCC ratio of 90:10 and a 5% citric acid crosslinker concentration. The hydrogel film showed a swelling capacity of 322.72%±9.32 at pH 7, a gel fraction of 9.87%±0.26, and a dry gel rehydration ability of 466.96%±30.41. The tensile strength for the CMC/MCC 90:10 ratio was 0.303±0.001 MPa, and the strain at F max was 48.74%±2.42. The water vapor permeability level was also measured at 3.688x10-5 g/m.Pa.24h. Increasing the MCC to CMC ratio to 50:50 led to a decrease in the water vapor permeability of the hydrogel film.

Determining the Starting Time of CO2 Injection and Its Implications for the CO2-ECBM Process.

Determining the starting time of the CO2 injection is the key factor affecting the effect of CO2 injection and CH4 production. This study uses the Panyidong mine in the Huainan mining area as an example. First, fully coupled mathematical models are established. Second, the evolution law of the reservoir parameters under different starting times of CO2 injection is visualized. Then, the starting time of the CO2 injection is determined, and the transformation process of CH4 displaced by CO2 is discussed. Finally, the connotation of the continuous fluid process during the CO2-ECBM process is analyzed, and constructive suggestions for CO2 injection are presented. The results show that during the CO2-ECBM process, the reservoir pressure and gas content greatly change near the CO2 injection well, and gradually decrease near the CH4 production well. The competitive adsorption of the gas is exothermic, and the reservoir temperature gradually increases. The competitive adsorption of gas causes matrix expansion, which results in a decrease in permeability. The CH4 production rate can be increased by about 2 times, and the evolution law of the CO2 injection rate shows little difference. If the purpose of CO2 injection is to store CO2, the start time of CO2 injection may be set as the 2000th day. The CO2-ECBM process can be divided into three stages to characterize the importance of displacement and replacement effects in each stage. Determining the starting time of CO2 injection and giving more desorption time to CH4 is conducive to the expansion of pore and fracture spaces, and then gives more competitive adsorption time to gas. This study can promote the engineering implementation of the CO2-ECBM technology.

A shared mechanism of multidrug resistance in laboratory-evolved uropathogenic Escherichia coli

ABSTRACT The emergence of multidrug-resistant bacteria poses a significant threat to human health, necessitating a comprehensive understanding of their underlying mechanisms. Uropathogenic Escherichia coli (UPEC), the primary causative agent of urinary tract infections, is frequently associated with multidrug resistance and recurrent infections. To elucidate the mechanism of resistance of UPEC to beta-lactam antibiotics, we generated ampicillin-resistant UPEC strains through continuous exposure to low and high levels of ampicillin in the laboratory, referred to as Low AmpR and High AmpR, respectively. Whole-genome sequencing revealed that both Low and High AmpR strains contained mutations in the marR, acrR, and envZ genes. The High AmpR strain exhibited a single additional mutation in the nlpD gene. Using protein modeling and qRT-PCR analyses, we validated the contributions of each mutation in the identified genes to antibiotic resistance in the AmpR strains, including a decrease in membrane permeability, increased expression of multidrug efflux pump, and inhibition of cell lysis. Furthermore, the AmpR strain does not decrease the bacterial burden in the mouse bladder even after continuous antibiotic treatment in vivo, implicating the increasing difficulty in treating host infections caused by the AmpR strain. Interestingly, ampicillin-induced mutations also result in multidrug resistance in UPEC, suggesting a common mechanism by which bacteria acquire cross-resistance to other classes of antibiotics.

Vacancy-Mediated Increases in Brine-Salt Surface Energies.

Salt formations have been explored for the permanent isolation of spent nuclear fuel based on their high thermal conductivity, self-healing nature, and low hydraulic permeability to brine flow. Vacancy defect concentrations in salt complicate fracture mechanics not driven by dislocation dynamics and can influence the resulting surface structure. Classical molecular dynamic simulations were used to simulate tensile testing of salt crystals (halite) with vacancy defect concentrations of up to 0.5 defects/nm3. Increasing defect concentrations resulted in a decrease in ultimate tensile strength and fracture surface energies, driven by increased surface roughness rather than changes in the amount of surface area. Brine-salt surface energies of the fractured surfaces were 0.22 to 0.26 J/m2, significantly higher than values reported for atomically flat (100) surfaces at the same brine composition. This change in surface energy increased the brine-salt dihedral angle by ∼27°. The dihedral angle threshold for percolation in salt is 60°, and a 27° increase due to rough fracture surfaces identifies a reduction in porosity percolation and a decrease in salt permeability. Therefore, bedded salt and salt domes may be even more stable than those previously predicted from dihedral angle calculations.

Wellhead Stability during Development Process of Hydrate Reservoir in the Northern South China Sea: Evolution and Mechanism

Natural gas hydrates represent a promising clean energy source with vast reserves. Their efficient development is crucial for ensuring the sustainable advancement of human society. However, wellhead instability occurred in the long-term development, which poses a significant challenge that impacts its commercial development. In the present work, the properties of hydrate-bearing sediments were experimentally investigated. It was found that the elastic modulus, cohesion, and internal friction angle of hydrate-bearing sediments exhibit an increase with the effective stress. As an example, when the effective stress increases from 0 MPa to 25 MPa, the normalized elastic modulus exhibits a rise from 1.00 to 1.36. Conversely, the Poisson’s ratio, permeability, and porosity demonstrate a decline in accordance with this trend. As an example, both normalized porosity and permeability decrease to values below 0.40 as the effective stress increases to 25 MPa. Based on the experimental results and previous work, a comprehensive model for describing the effect of both hydrate saturation and effective stress on physical parameters was obtained. Subsequently, a multi-field coupled investigation methodology was developed to evaluate wellhead stability during the long-term development of hydrate-bearing sediments, and the evolution characteristics and mechanisms of wellhead instability were numerically explored. It reveals that development operation using the vertical wellbore decomposes hydrates in the surrounding sediments only within a radius of 19.52 m, which significantly undermines the wellhead stability. Moreover, the wellhead system not only sinks with sediment subsidence but also experiences additional sinking due to the failure of bonding between the wellhead system and sediments. Furthermore, the latter accounts for a significant portion, amounting to approximately 68.15% of the total sinking under the research conditions. This study can provide methodological prerequisites for exploring the impact of various factors on wellhead stability during the long-term hydrate development process.

Effect of the Heterogeneity of Coal on Its Seepage Anisotropy: A Micro Conceptual Model

Coal is a typical dual-porosity structural material. The injection of CO2 into coal seams has been shown to be an effective method for storing greenhouse gasses and extracting coal bed methane. In light of the theory of dual-porosity media, we investigate the impact of non-homogeneity on seepage anisotropy and examine the influence of CO2 gas injection on the anisotropy of coal and the permeability of fractures. The results demonstrate that under constant pressure conditions, coal rock has the greatest permeability variation in the direction of face cleats and the smallest changes in the direction of vertical bedding. The more pronounced the heterogeneity, the more evident the change in permeability and the less pronounced the decreasing stage of permeability. Additionally, the larger the diffusion coefficient is, the less pronounced the permeability change. The change in permeability is inversely proportional to the size of the adsorption constant and directly proportional to the size of the fracture. As the matrix block size increases, the permeability also increases, whereas the decrease in permeability becomes less pronounced. The findings of this study offer a theoretical basis for further research into methods for enhancing the CO2 sequestration rate.

Improvement of Rheological Properties of Modified Asphalt Treated with Residues of Recycled Rubber from Waste Tires and Oxidized by Air

Asphalt materials loaded with polymer additives have gained particular importance in recent years due to their close association with modification processes and the creation of a clean environment, mainly from plastic wastes in paving and other areas, and they have also caused significant improvement in asphalt properties. It was observed through the research that the rheological properties of the asphalt were improved significantly as added residues of recycled rubber (RRR) from waste tire percentages increased. The observations are apparent from the decrease in permeability of the asphalt and enhance its ductility and elongation. The study focused on modifying the rheological properties of asphalt materials using the residues of the recycled process of rubber (RRR) from waste tires (mainly carbon black, containing residues of rubber extracted from waste tires). The asphalt materials were oxidized in the open system under various conditions of temperature and oxidation time in the presence of a 0.25% (w/w) anhydrous aluminum chloride (AlCl3) catalyst. After determining the optimal conditions for the oxidation process, the added anhydrous AlCl3 catalyst was adjusted to determine its optimal ratio. The modified asphalt samples after oxidation at optimal conditions in the presence of anhydrous AlCl3 catalyst and the recycled rubber (RRR) residues were tested using appropriate measurements. The following measurements of ductility, permeability, softening point, Marshall stability and flow, aging resistance (thin film oven test (TFOT)) and the asphalt content percentages were done, and their results show that the modified asphalt exhibits completely different rheological properties from the original asphalt. The studied N19 and N20 models show availability in paving applications.

Soil behavior near the PVD filter and interpretation of clogging during vacuum preloading

Clogging near the prefabricated vertical drain filter during vacuum preloading reduces the efficiency of ground treatment, and existing research has yet to agree on the cause. This study conducted a small model test to comprehensively examine the soil's water content and particle size distribution at different distances from the filter and tailwater for different preloading durations. The results showed that the particle size distribution of the soil at different selected points exhibited a slightly irregular difference. This indicates that no measurable migration of particles occurs, which was further confirmed by the particle size distribution of the soil after the one-dimensional consolidation test. The application of vacuum pressure did not significantly change the soil particle composition and, thus, its compressibility and permeability properties. The particle size distribution of tailwater revealed that a small number of fine particles with a mean size of 3–4 μm rapidly discharged with tailwater during the initial stage of vacuum preloading, which was much less than the mean size of the slurry and pore size of the filter. The decrease in water content and permeability indicates non-uniform consolidation, and the increase in the permeability coefficient ratio suggests the formation and development of the clogging zone.

Active polyvinyl alcohol films with enhanced strength, antioxidant and antibacterial properties by incorporating nanocellulose and tannin

There is an increasing demand of food packaging materials from sustainable bio- polymers. In this study, tannin-cellulose nanocrystal (TCNCs) fillers were first prepared using dialdehyde cellulose nanocrystal (DACNCs) and tannin through the nucleophilic addition reaction, and then added to PVA matrix as reinforcement fillers to fabricate active food packaging films. FT-IR analysis confirmed the successful reaction between PVA and TCNCs. The incorporation of TCNCs imparted high antibacterial, UV blocking and antioxidant capabilities to the composite films, maximumly achieving a 75 % DPPH free radical scavenging rate while blocking all UV rays. The addition of TCNCs resulted in an increase in water contact angle, alongside decreases in swelling ratio and solubility, indicating the enhanced water resistance. The composite films exhibited a 66.7 % decrease in oxygen permeability (OP) compared to the PVA film, with a slight increase observed in water vapor permeability (WVP). The tensile strength increased from 49.65 MPa to 74.17 MPa by adding 15 % of TCNCs due to the chemical crosslinking between PVA and TCNCs. Wrapping cherry tomatoes with these films prolonged the postharvest life compared to using polyethylene (PE) and pure PVA films. Films derived from sustainable biopolymers show great potential for use in fresh produce packaging.

Synthesis of fluorinated ether free aromatic backbone copolymers containing trifluoromethyl and dimethylamino groups for CO2 separation: Investigation of pure and mixed gas performance under dry and humid conditions

A novel series of linear, high molecular weight aromatic copolymers containing trifluoromethyl and dimethylamino groups was synthesized via facile super-acid catalyzed polyhydroxyalkylation and investigated as CO2 gas separation membrane materials. The molar ratio of the two ketone comonomers used in copolymerization, trifluoroacetophenone (TFAp) and N,N-dimethylamino trifluoroacetophenone (dMATFAp), was systematically varied to produce five copolymers with different dMATFAp contents ranging from 12 to 73 %. The influence of dMATFAp content on physicochemical and mechanical properties as well as pure gas and water vapor separation performance was studied. All synthesized copolymers displayed excellent film forming ability, high thermal stability and high Tg values (Tgs > 380 °C). Pure gas permeability measurements revealed that the increase of dMATFAp molar content from 12 % to 34 % resulted in improved gas permeability, while, on the contrary, further increase of dMATFAp content from 34 to 73 % led to substantial gas permeability decrease ascribed to FFV decrease. In particular, among copolymers, the one with dMATFAp content of 34 % presented the highest CO2 permeability value of 290 Barrer due to its highest CO2 diffusion and CO2 solubility coefficients associated with its higher FFV value. The CO2/CH4 performance of synthesized copolymers fell very close to 2008 upper bound limit and exceeded most of the super-acid catalyzed copolymer membranes reported in the literature and commercial membranes. CO2/CH4 and CO2/N2 selectivity values for the different synthesized copolymers were in the range of 29.9–40 and 22.7–44, respectively. The study of the effect of dMΑTFA on water permeability unveiled that the membrane with the highest dMΑTFAp molar content (73 %) showed the highest water permeability value (23,100 Barrer) as well. This was attributed to the increased concentration of N-methyl substituent of dMΑTFAp which can interact with water molecules thereby increasing solubility. Under process gas stream conditions using a mixture of 3 % H2O-48.5 % CO2-48.5 % CH4, both CH4 and CO2 permeability were significantly reduced (by 35 % and 47 %, respectively) due to the preferential sorption of water vapor over other gases present in the mixture, highlighting the negative effect of water vapor on gas permeability. Accordingly, the CO2/CH4 separation factor was slightly increased from 23.8 to 29. Finally, stability test of the copolymer (BP-TFAp)66-(BP-dMATFAp)34 at 40 °C under humid mixed gas conditions showed that CO2 and CH4 permeability remained unchanged for one month after an initial condition stabilization that is required implying that these copolymer structures are promising materials for CO2 separation.

Comprehensive analysis of gas slippage and Non-Darcy flow in carbonate rock samples under stress conditions

This study examines the influence of stress on gas slippage and non-Darcy flow behavior in carbonate porous media, using core samples from two large carbonate reservoirs in the Middle East. Permeability measurements under varying stress conditions revealed significant increases in both the gas slippage factor and the non-Darcy coefficient with rising stress, indicating a related decrease in permeability. A new mathematical model, incorporating effective tortuosity and slippage radius into the Kozeny-Carman equation, was developed to accurately describe the stress-dependent nature of gas flow. Analysis of key pore attributes—such as porosity, pore size, shape, and tortuosity—underscored the critical role of pore structure, especially pore size and connectivity, in governing fluid flow under stress. These findings highlight the need to account for stress effects in reservoir engineering for improved modeling and management of carbonate reservoirs.