Reduced Water Permeability Research Articles

Integral and Surface Treatment Method of Waterproofing: A Review and Comparative Analysis

Water seepage into concrete can cause deterioration and other aesthetic issues that limit the life of concrete constructions. This paper examines and contrasts the various kinds of waterproofing techniques. There are essentially two types: surface treatment method and integral method. Water repellents, crystalline admixtures, and densifiers are examples of integral methods. Surface treatment methods encompass pore-blocking, hydrophobic impregnation, surface coating, and multifunctional surface treatment. The processes of various approaches are examined in this article, followed by a comparison of their durability and mechanical properties. We discuss several properties, such as sulfate attack, chloride penetration, carbonation, reinforcement corrosion, water absorption and permeability, compressive, flexural, and tensile strength. The findings indicate that each has merits and demerits of their own. The inclusion of an integral admixture to concrete offers a number of advantages over surface protection, including convenience of application, the removal of the need for ongoing maintenance, and minimal to no deterioration over time. While surface treatment methods significantly reduce water permeability and porosity. In conclusion, we give a succinct summary of certain issues regarding the present state of research and future directions for the hydrophobic modification of concrete.

MICP treated sand: insights into the impact of particle size on mechanical parameters and pore network after biocementation

Microbiologically Induced Calcium Carbonate Precipitation (MICP) is a technology for improving soil characteristics, especially strength, that has been gaining increasing interest in literature during the last few years. Although a lot of influencing factors on the result of MICP are known, particle size and shape of the particles remain poorly understood. While destructive measuring of compressive strength or calcium carbonate content are important for the characterization of samples these methods give no insight into the internal structures and pore networks of the samples. X-ray microcomputed tomography (micro-CT) is a technique that is used to characterize the internals of rocks and to a certain degree MICP-treated soils. However, the impact of filtering and image processing of micro-CT Data depending on the type of MICP sample is poorly described in the literature. In this study, single fractions of local quarry were treated with MICP through the ureolytic microorganism Sporosarcina pasteurii to investigate the influence of particle size distribution on calcium carbonate content, unconfined compressive strength and the reduction of water permeability. Additionally, micro-CT was conducted to obtain insights into the resulting pore system. The impact of the Gauss filter und Non-local means filter on the resulting images and data on the pore network are discussed. The results show that particle size has a significant impact on the result of all tested parameters of biosandstone with lower particle size leading to higher strength and generally higher calcium carbonate content. Micro-CT data showed that the technology is feasible to gain valuable insights into the internal structures of biosandstone but the resolution and signal-to-noise ratio remain challenging, especially for samples with particle sizes smaller than 125 µm.

Preparation and Characterization of Preformed Polyelectrolyte and Polyampholyte Gel Particles for Plugging of High-Permeability Porous Media.

Excessive reservoir water poses significant challenges in the oil and gas industry by diminishing hydrocarbon recovery efficiency and generating environmental and economic complications. Conventional polymer flooding techniques, although beneficial, often prove inadequate under conditions of elevated temperature and salinity, highlighting the need for more resilient materials. In this research, two types of acrylamide-based preformed particle gels (PPGs) were synthesized, as follows: polyelectrolyte and polyampholyte. These PPGs were engineered to improve plugging efficiency and endure extreme reservoir environments. The polyelectrolyte gels were synthesized using acrylamide (AAm) and sodium acrylate (SA), while the polyampholyte gels incorporated AAm, AMPS, and APTAC, with crosslinking achieved through MBAA. The swelling properties, modulated by temperature, salinity, and pH, were evaluated using the Ritger-Peppas and Yavari-Azizian models. The mechanical characteristics and surface morphology of the gels were analyzed using SEM and BET techniques. In sand pack experiments designed to mimic high-permeability reservoirs, the inclusion of 0.5 wt.% of fine PPGs substantially reduced water permeability, outperforming traditional hydrogels. Notably, the polyampholyte PPGs demonstrated superior resilience and efficacy in plugging. However, the experiments were limited by the low test temperature (25 °C) and brine salinity (26.6 g/L). Future investigations will aim to apply these PPGs in high-temperature, fractured carbonate reservoirs.

Justification for the use of modified concrete for foundations of overpass supports

Introduction. The article discusses the possibilities and prospects of using modified concrete for the foundations of overpass supports. The aim is to study the effect of various additives on the sulfate resistance of the foundations of bridge supports and overpasses. Materials and methods. To achieve this goal, tests of reinforced concrete samples were carried out with the introduction of various additives into the concrete mixture. As part of the study, a MasterLife® WP 3760 modifying additive was selected. Using this additive, experiments were conducted with an accelerated assessment of the effect on the sulfate resistance of concrete based on general-purpose Portland cement. In accelerated tests, the sulfate resistance of concretes with the studied additive was performed in comparison with concretes of the same composition prepared on sulfate-resistant and general-purpose Portland cement without additional additives. The water-cement ratio in all tested formulations remained constant. Results. Samples made of general construction cement with the addition of MasterLife® WP 3760 after performing the specified test cycles in a sulfate medium showed a decrease in compressive strength by 3 % from their initial values. The residual strength of concrete samples with MasterLife® WP 3760 additive was 97 %, which exceeds the resistance of concrete to sulfate-resistant cement, the remaining strength of which is 94 %. The MasterLife® WP 3760 additive is a substance that significantly reduces the permeability of concrete due to "blockage" by particles of the substance or neoplasms of pores and capillaries of concrete, these substances due to physical and chemical processes lead to homologation, a decrease in the permeability of concrete, and, as a result, an increase in frost resistance and corrosion resistance. Conclusion. As a result of the action of the MasterLife® WP 3760 additive, the corrosion resistance of concretes and mortars increases, including resistance to sulfate aggression, by reducing water permeability. Thus, it becomes possible to eliminate cracks in concrete with an opening width of up to 0.4 mm and extend the durability of concrete.

Geological analysis of the hydro-mechanical responses of Opalinus claystone to excavation-induced damage via engineering

In the realm of engineering geology, specifically concerning the containment of high-level radioactive waste, this study examines the excavation-induced damage zone (EDZ) in underground drifts and its evolution, which is critical for the effectiveness of underground repositories. The focus is on the self-sealing capability of the EDZ in Opalinus claystone (OPA) under mechanical compression and hydration induced by a bentonite core sealing component post-nuclear waste emplacement. This core applies a swelling pressure of 5 MPa to the drift walls during resaturation, affecting repository integrity. Using numerical modeling, this study pioneers the simulation of real-time self-sealing mechanisms in OPA, a crucial geological barrier in nuclear waste containment. The approach integrates a plastic damage model with an auxiliary deformation model and Biot’s model to accurately depict moisture-dependent OPA deformation. This modeling is essential for understanding claystone geomechanics in nuclear waste repositories. Detailed post-analysis of crack features and unsaturated fractured OPA permeability, following fracture energy regularization principles and the cubic law, provides insights into the geotechnical properties of the EDZ, enhancing the accuracy of geological forecasts in nuclear waste management. The model’s reliability is confirmed through various numerical simulations, including triaxial compression tests, observations of swelling deformations due to moisture variations, and comprehensive water permeability tests assessing the self-sealing efficiency of fractured OPA during water injection. In situ experiments at the Mont Terri Rock Laboratory support these findings, particularly regarding EDZ self-sealing under combined mechanical and hydration conditions. Comparative analysis of numerical results and experimental data validates the model’s ability to replicate fractured OPA self-sealing behavior, crucial for assessing nuclear waste repository safety and effectiveness. Effective self-sealing is underscored by reduced water permeability in the EDZ during resaturation, affirming the model’s relevance in evaluating nuclear waste containment strategies. Moreover, insights from this model extend to assessing CO2 migration, given claystones’ role as caprocks in CO2 geological sequestration schemes, thereby enhancing its importance in long-term environmental safety evaluations for both nuclear waste and CO2 storage scenarios.

Single-layer encapsulation film with CaO absorbent by solution process

A method for preparing a single-layer encapsulation film using an organic-inorganic hybrid precursor solution processing was investigated. The film was created using a commodity epoxy and graphene oxide to ensure cost-effectiveness. Fast curing and annealing techniques, including microwave and intense pulsed light exposure, were employed. Calcium oxide nanoparticles were incorporated as a special moisture absorbent to improve the film's barrier properties. The barrier performance of the single layer encapsulation film was considerably enhanced by post-treatment of these nanoparticles. The characterization of the calcium oxide nanoparticles after post-treatment was performed using transmission electron microscopy with energy-dispersive X-ray spectroscopy, FT-IR, Brunauer-Emmett-Teller test. The composite epoxy encapsulation film, incorporating graphene oxide and post-treated calcium oxide nanoparticles, reduced water permeability approximately 400 times compared to the neat epoxy encapsulation film. This substantial improvement makes it suitable for use in flexible disposable electronics. The enhanced water vapor blocking efficiency is attributed to the combined effect of pathway block by graphene oxide and moisture absorption by calcium oxide.

Artificial Ground Freezing—On the Soil Deformations during Freeze–Thaw Cycles

Artificial ground freezing (AGF) has emerged as a prominent treatment method due to its ability to mechanically strengthen the soil while reducing its permeability. However, its implementation has raised concerns about its impact, particularly with respect to frost heave and subsequent thaw-induced displacements. These soil movements can cause subsidence and pose a significant threat to the integrity of surface structures. Overburden pressure plays a crucial role in AGF and determines the amount of heave generated. This paper presents an analysis of the existing literature about soil freezing and thawing. The aim is to offer an understanding of these processes, specifically with regard to their application in AGF. This paper explains the behavior of soil during freezing, with particular emphasis on the influence of overburden pressure. It also investigates frozen soils’ thawing and freeze–thaw (FT) cycles’ long-term effects on soil properties. AGF offers improved soil strength and reduced water permeability, enhancing construction project stability. However, the interplay between the temperature, soil composition, and initial ground conditions during freezing is complex. This thermo-hydro-chemo-mechanical process strengthens the soil and reduces its permeability, but it can also induce frost heave due to water expansion and ice lens formation. Overburden pressure from the overlying soil limits ice lens growth. FT cycles significantly impact soil properties. In fine-grained soils, FT cycles can lead to over-consolidation, while rapid thawing can generate high pore pressures and compromise stability. Importantly, FT acts as a weathering mechanism, influencing soil properties at both the microscopic and macroscopic scales. These cycles can loosen over-consolidated soil, densify normally consolidated soil, and increase overall hydraulic conductivity due to structural changes. They can also weaken the soil’s structure and deteriorate its mechanical performance.

Wellbore salt-deposition risk prediction of underground gas storage combining numerical modeling and machine learning methodology

Strengthening the construction of underground gas storage (UGS) is significant for securing national energy and achieving carbon neutrality. However, salt deposition occurs in the wellbore affecting the safety of UGS seriously. How to predict the salt-deposition risk in UGS wells accurately and quickly is still challenging. This work aims at establishing a fast and convenient framework of wellbore salt-deposition risk prediction in UGS wells. Firstly, the influence of the production parameters on wellbore salt-deposition is analyzed by an in-house simulator. Further, an intelligent diagnostic model of salt-deposition risk is proposed based on the machine learning algorithm. The effect of salt deposition on reservoir is analyzed by reservoir salt-deposition simulation model. Finally, downhole video survey is used to validate the modeling accuracy of diagnostic model. Results indicate that the contribution ratio of daily gas production and water-gas-ratio to wellbore salt deposition is 3:2. After the salt deposition, the reduction in water saturation and the permeability of near wellbore areas are 77.14 % and 98.91 %. The modeling accuracy of diagnostic model is 97 %, which is applied in the Y UGS successfully. The proposed framework can predict the salt-deposition risk of UGS wells in real time to help engineers control salt clogging issues.

Frequency-Dependent Dielectric Permittivity and Water Permeability in Ordered Mesoporous Silica-Grafted Fluorinated Polyimides.

Polymers with a low dielectric constant (Dk) are promising materials for high-speed communication networks, which demand exceptional thermal stability, ultralow Dk and dissipation factor, and minimum moisture absorption. In this paper, we prepared a series of novel low-Dk polyimide films containing an MCM-41-type amino-functionalized mesoporous silica (AMS) via in situ polymerization and subsequent thermal imidization and investigated their morphologies, thermal properties, frequency-dependent dielectric behaviors, and water permeabilities. Incorporating 6 wt.% AMS reduced the Dk at 1 MHz from 2.91 of the pristine fluorinated polyimide (FPI) to 2.67 of the AMS-grafted FPI (FPI-g-AMS), attributed to the free volume and low polarizability of fluorine moieties in the backbone and the incorporation of air voids within the mesoporous AMS particles. The FPI-g-AMS films presented a stable dissipation factor across a wide frequency range. Introducing a silane coupling agent increased the hydrophobicity of AMS surfaces, which inhibited the approaching of the water molecules, avoiding the hydrolysis of Si-O-Si bonds of the AMS pore walls. The increased tortuosity caused by the AMS particles also reduced water permeability. All the FPI-g-AMS films displayed excellent thermooxidative/thermomechanical stability, including a high 5% weight loss temperature (>531 °C), char residue at 800 °C (>51%), and glass transition temperature (>300 °C).

Biocomposite Films of Amylose Reinforced with Polylactic Acid by Solvent Casting Method Using a Pickering Emulsion Approach

Binary and ternary blends of amylose (AM), polylactic acid (PLA), and glycerol were prepared using a Pickering emulsion approach. Various formulations of AM/PLA with low PLA contents ranging from 3% to 12% were mixed with AM matrix and reinforced with 25% cellulose nanofibers (CNF), and PLA-grafted cellulose nanofibers (g-CNF), the latter to enhance miscibility. Polymeric films were fabricated through solvent casting and characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Wide-Angle X-ray Scattering (WAXS), and the evaluations of physical, mechanical properties, and wettability were performed using contact angle measurements. The binary blends of AM and PLA produced films suitable for packaging, pharmaceutical, or biomedical applications with excellent water barrier properties. The ternary blends of AM/CNF/PLA and AM/g-CNF/PLA nanocomposite films demonstrated enhanced tensile strength and reduced water permeability compared to AM/PLA films. Adding g-CNF resulted in better homogeneity and increased relative crystallinity from 33% to 35% compared to unmodified CNF. The application of Pickering emulsion in creating AM-based CNF/ PLA composites resulted in a notable enhancement in tensile strength by 47%. This study presents an effective approach for producing biodegradable and reinforced PLA-based nanocomposite films, which show promise as bio-nanocomposite materials for food packaging applications.

A middle school investigation into developing environmentally friendly packaging

This STEM research project asks middle school or high school students to work towards creating ecologically friendly packaging. Packaging that can be composted instead of thrown away and collected in landfills and oceans like plastics. This inquiry uses nanocellulose and focuses on water permeability. The fibers of nanocellulose can be dried to make a rather strong and thin film, but due to the spaces between the fibers the film is too water permeable and therefore makes poor packaging materials on its own. Students will create nanocellulose composite films with other biodegradable materials, in an attempt to fill the inter-fiber microscopic spaces and create a new film that can be easily tested for water permeability. Students set up a straightforward science experiment with films, water, and mason jars. They will collect and graph data to determine if their nanocellulose composite films reduce water permeability compared to plain nanocellulose and how close they are to the present standard, plastic. This research is an amalgam of disciplinary core ideas like properties and states of matter, as well as a combination of science and engineering practices. It ignites students’ curiosity, provides an organic path to science fair extensions, while also helping to cultivate future scientists, engineers, and environmental activists.

Effect of industrial wastes on the properties of sustainable ultra-high-performance concrete: Ganite, ceramic, and glass

The creation of ultra-high-performance concrete (UHPC) requires a huge amount of cement. However, the production of cement raises environmental concerns related to non-renewable resources, carbon dioxide emissions, and global warming. To overcome these issues, it was necessary to expand the production of eco-friendly, sustainable ultra-high-performance concrete (SUHPC) by applying procedures to minimize cement use. This research was able to produce SUHPC with compressive strengths ranging from 168 to 233 MPa at 91 d under standard curing by employing industrial wastes such as granite dust, ceramic powder, and glass powder as a partial replacement of cement by about 26% of its weight, in addition to using crushed granite, ceramic, and glass as a 50% and 100% by volume substitute for sand within the concrete mixture. The influence of these industrial wastes on the mechanical and physical characteristics of SUHPC was investigated. Additionally, the temperature studies on the SUHPC containing industrial wastes and the analysis of the microstructure were presented. The study revealed that replacing some of the cement with granite powder and all of the sand with crushed granite in the SUHPC mixture led to the highest compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity. Specifically, the mixture achieved 196.7 MPa compressive strength, 21.9 MPa splitting tensile strength, 30.3 MPa flexural strength, and 61,010 MPa modulus of elasticity after 28 d. Furthermore, the replacement significantly improved the SUHPC's physical properties. For instance, it reduced water permeability by 18.83%. However, adding glass to the SUHPC mixture negatively impacted both its mechanical and physical characteristics.

Concentration-Dependent Effects of Curcumin on Membrane Permeability and Structure.

Growing evidence suggests that many bioactive molecules can nonspecifically modulate the physicochemical properties of membranes and influence the action of embedded membrane proteins. This study investigates the interactions of curcumin with protein-free model membranes consisting of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and DOPC with cholesterol (4/1 mol ratio). The focus is on the capability of curcumin to modify membrane barrier properties such as water permeability assayed through the droplet interface bilayer (DIB) model membrane. For pure DOPC, our findings show a concentration-dependent biphasic effect: a reduction in water permeability is observed at low concentrations (up to 2 mol %), whereas at high concentrations of curcumin, water permeability increases. In the presence of cholesterol, we observed an overall reduction in water permeability. A combination of complementary experimental methods, including phase transition parameters studied by differential scanning calorimetry (DSC) and structural properties measured by attenuated total reflectance (ATR)-FTIR, provides a deeper understanding of concentration-dependent interactions of curcumin with DOPC bilayers in the absence and presence of cholesterol. Our experimental findings align with a molecular mechanism of curcumin's interaction with model membranes, wherein its effect is contingent on its concentration. At low concentrations, curcumin binds to the lipid-water interface through hydrogen bonding with the phosphate headgroup, thereby obstructing the transport of water molecules. Conversely, at high concentrations, curcumin permeates the acyl chain region, inducing packing disorders and demonstrating evidence of phase separation. Enhanced knowledge of the impact of curcumin on membranes, which, in turn, can affect protein function, is likely to be beneficial for the successful translation of curcumin into effective medicine.

Development and characterization of pearl millet (AHB 1200) starch nanoparticle‐based edible films: A paradigm shift in food packaging

AbstractPearl millet, known for its adaptability to challenging agro‐climatic conditions, emerges as a valuable candidate for biopolymer‐based packaging. The AHB 1200 cultivar, distinguished by its high starch content, provides a reliable source for biopolymer extraction. The conversion of pearl millet starch into nanoparticles by acid hydrolysis represents a cutting‐edge method to enhance biopolymeric materials. The inclusion of these nanoparticle concentrations (0.5%, 1%, 5%, and 10%) into the film results in improved mechanical characteristics, reduced water permeability, and increased biodegradability. Furthermore, the lowered water solubility and reduced water vapor transmission rate (WVTR) further underscore their positive contributions. This study comprehensively examines various film properties, encompassing WVTR from 7.23 ± 0.06 to 4.57 ± 0.08 g/m2/s, moisture content, solubility from 35.29 ± 0.51% to 30.09 ± 0.15%, burst strength from 1102.11 ± 0.99 g to 1535.71 ± 0.63 g, thermal stability, and biodegradability from 65.16% to 92.89%. The findings highlight the notable advancements achieved through the integration of starch nanoparticles.Practical applicationsPearl millet (AHB 1200) starch nanoparticle‐based edible films offer a versatile solution for specialized food packaging needs because of their compatibility with various food types, dairy products, fresh produce, and so on. These films act as a protective barrier and maintain product freshness during storage and transit. It also has enhanced mechanical strength and tear resistance and provides vacuum‐sealed packaging, ensuring an extended shelf life. Beyond their functional benefits, these edible films present an opportunity for branding and marketing differentiation. The films made with pearl millet have an earthy, natural appearance that fits with today's customer inclination for sustainable and environmentally friendly goods. This allows manufacturers to leverage the films as a means of conveying their commitment to environmentally friendly practices, enhancing their brand image and consumer loyalty. Furthermore, the biodegradability of these films is preferred over plastic waste. They offer a viable alternative to traditional plastic packaging, aligning with global initiatives to reduce the environmental impact of packaging materials.

THE EFFECT OF POLYMER GEL ON THE OIL AND WATER PERMEABILITY DAMAGE IN A MICROFLUIDIC DEVICE

Microfluidics, a rapidly advancing field, finds wide applications in various domains, including enhanced oil recovery. This study delineates the methodology for fabricating a microchip with channels having a width of 50 μm, designed to simulate and visualize fluid flow in porous media. The microfluidic device was constructed using NOA81, a UV-curable polymer. Upon curing, it forms a robust and transparent microchip structure suitable for precise fluid control and analysis in microfluidic applications. Flood experiments conducted on the microchip revealed that the introduction of a 0.5 wt% polymer gel into the model's channels resulted in a reduction of water permeability by a factor of 106 and 25 at the shock front and after injection pressure stabilized, respectively. In contrast, oil permeability was reduced by at least 40 times.

Mulch and efficient microorganisms: effects on the management of soil salinity in banana

Mulch consists of covering the surface layer of the soil with plant or organic residues, preventing moisture loss, reducing weeds, and increasing microbiological activity. Efficient microorganisms work by breaking down organic matter to store carbon, together with biochar, retaining nutrients and improving its biological capacity. The high presence of salts harms and degrades the soil structure, reducing water permeability, and causing severe issues in the root system and foliage of the plant. In this case, the research objective is to evaluate the effects of mulch and efficient microorganisms on salinity management in banana cultivation. Three treatments were performed: T1 (mulch, 10g biochar, 10g silicon); T2 (mulch, 10g biochar, 10g silicon, 10g microorganisms, 35g rooting agent); T3 (mulch, 10g biochar, 10g silicon, 10g microorganisms, 35g rooting agent, 70ml physiological regulator). T2 and T3 significantly lowered soil electrical conductivity, improving nutrient availability and percentages of functional roots in the banana crop, which has a positive impact on plant growth and development. These results highlight the importance of considering these agricultural practices to optimize banana production.

Reduction in Water Permeability of a Penetrating-Sealer-Incorporated Liquid Deicer

Various efforts have been made to minimize the corrosion damage of deicer. However, due to the nature of the deicer that needs to lower the freezing point, the concrete damage due to the repeated freeze-thaw cycle caused by the penetration of the deicer solution into the pores of the concrete could not be fundamentally suppressed. Therefore, a basic study was conducted to minimize the deterioration of concrete by suppressing the water permeability of the concrete surface with penetrating sealer incorporated deicer. Dynamic light scattering and zeta-potential analyses were performed to evaluate the mean diameter and degree of dispersion of the suspension in the aqueous solution of the prepared liquid deicer. Experiments confirmed the water permeability to be 44%–58% that of the untreated control group, and the mass of certain concrete specimens after freeze–thaw cycling tests tended to increase. In addition to the reduction in water permeability, in this study, an increase in the mass of the specimen in repeated freeze thaw cycle was confirmed, which is Liquid deicers with penetrating sealers have the potential to improve the durability and reduce the deterioration of concrete.

Water permeability of dark chestnut soil and agrochemical factors determining chickpea yield

A six-year analysis of changes in soil water permeability according to the basic tillage options is provided. Plowing with a PBS -10 P plow reduced water permeability by 3.1%. An increase in soil density by 6.3% for no-tillage and by 9.8% for minimum tillage reduced water permeability by 13.3 and 41.9%, respectively. Calculation of the multiple regression equation and full correlation analysis showed that the maximum influence on water permeability is exerted by the depth of the main cultivation - 44.92%, soil density determined this indicator by 38.17%, humidity by only 0.91%, the share of unaccounted factors was 16% . The yield of chickpea grain varied from 0.39 - 0.65 t/ha in 2020 (GTCMay - August = 0.20) to 1.54 - 2.12 t/ha in 2023 (GTCMay - August = 0. 64). Over six years of observation, according to factor A (basic tillage for chickpeas), the maximum yield of chickpea grain without the use of agrochemicals was noted on plowing: 1.19 t/ha (PLN-8-35) and 1.20 t/ha (PBS-10 P). Duringnon-moldboard processing (SSD-4 and PChM-4), the yield decreased by 10.9%, with a minimum (PM 7?3) by 22.7%. Foliar feeding with mineral fertilizers and fertilizers based on humic acids during the phases of branching and the beginning of budding of chickpeas of the Zoovit variety increased the yield by 11.9–14.7%.

Insight into polydopamine coating on microfiltration membrane with controlled surface pore size for enhanced membrane rejection

Membrane modification with polydopamine (PDA) is a common practice to enhance membrane selectivity and improve membrane compatibility with nanoparticles or thin films. Depending on the membrane surface properties, dopamine can deposit or penetrate into microporous membranes, leading to alteration in the membrane's physicochemical properties and consequently its performance. In this study, microfiltration (MF) polyethersulfone membranes with varying surface pore sizes were fabricated by manipulating the precasting time (solvent evaporation time of 3s, 15s, 30s and 60s) prior to non-solvent induced phase separation (NIPS) process. Notably, the coating of PDA slightly reduced the membrane's surface pore size and membrane's porosity. M60 membrane which possessed the smallest mean surface pores (∼300 nm), exhibited PDA clusters predominantly formed on top of the membrane surface. With an increase in surface pore size, dopamine can penetrate the porous structure of the MF membrane, leading to the polymerization of dopamine into PDA aggregates on both the membrane surface and inner pores. The M30 membrane had the largest surface pore size (∼500 nm), showing the formation of large PDA globules in the finger-like pores. The membrane (M30P) experienced significant narrowing of the inner pores, resulting in reduced water permeability. Overall, all PDA-coated membranes exhibited improved sucrose rejection (85–95%) compared to the uncoated ones (64–83%). These finding provides insight into the polymerization mechanism of dopamine on porous membranes prior to the incorporation of nanomaterials or thin film coating.

Synergistic effect of graphene oxide/zinc oxide nanocomposites on polylactic acid-based active packaging film: Properties, release kinetics and antimicrobial efficiency

Incorporating two different nanoparticles in nanocomposite films is promising as their synergistic effects could significantly enhance polymer performance. Our previous work conferred the remarkable antimicrobial (AM) properties of the polylactic acid (PLA)-based film using optimal formulations of synergistic graphene oxide (GO)/zinc oxide (ZnO) nanocomposites. This study further explores the release profile of GO/ZnO nanocomposite and their impact on the antimicrobial properties. A fixed 1.11 wt% GO and different ZnO concentrations were well dispersed in the PLA matrix. Increasing ZnO concentrations tended to increase agglomeration, as evident in rougher surfaces. Agglomeration inhibited water penetration, leading to a significant reduction in water permeability (46.3 %), moisture content (31.6 %) but an improvement in Young's Modulus (52.6 %). The overall and specific migration of GO/ZnO nanocomposites was found to be within acceptable limits. It is inferred that the release of Zn2+ ions followed pseudo-Fickian behavior with an initial burst effect. AM film with the highest concentration of ZnO (1.25 wt%) exhibited the highest inhibition rate against Escherichia coli (68.0 %), Bacillus cereus (66.5 %), Saccharomyces cerevisiae (70.9 %). Results suggest that GO/ZnO nanocomposites with optimal ZnO concentrations have the potential to serve as promising antimicrobial food packaging materials, offering enhanced barrier, antimicrobial properties and a controlled release system.