Water Permeability Properties Research Articles

Utilization of wollastonite, jarosite, and their blends for the sustainable development of concrete paver block mixes containing reclaimed asphalt pavement aggregates.

While several research studies considered the utilization of reclaimed asphalt pavement (RAP) aggregates for asphalt and concrete pavements, very few attempted its possible utilization for precast concrete applications like concrete paver blocks (CPBs). Moreover, few attempts made in the recent past to improve the strength properties of RAP inclusive concrete mixes by incorporating certain supplementary cementitious materials (SCMs) have reported an insignificant or marginal effect. The present study attempts to comprehensively investigate the utilization potential of some locally and abundantly available materials having suitable physicochemical properties to improve the performance of a zero-slump CPB mix containing 50% RAP aggregates. The studied filler materials, namely, wollastonite (naturally occurring calcium metasilicate mineral) and jarosite (hazardous zinc industry waste), were used to replace 5-15% and 10-20% by volume of Portland cement in the 50% RAP CPB mix. Apart from their individual effects, the efficacy of wollastonite-jarosite blends was also investigated. Considering the lack of indoor storage facilities and economic aspects of CPBs, the influence of water spray curing regime on the performance of the RAP CPB mixes was studied and compared to that of continuous water curing regime. Inclusion of the considered fillers was found to statistically and significantly enhance the flexural strength, tensile splitting strength, and abrasion resistance of the 50% RAP CPB mix; however, the compressive strength (in most cases), permeable voids, water absorption, and water permeability properties showed an insignificant improvement. Results of thermogravimetric analysis confirmed the occurrence of pozzolanic reactivity, and microstructure analysis revealed improvements in packing of concrete matrix and ITZ with filler inclusion qualitatively substantiating the improvements in strength and durability characteristics. The toxicity characteristics of heavy metals that may leach from the hazardous jarosite-based RAP CPB mixes were found to be within permissible limits. Based on the performance requirements specified by IS, IRC, and ASTM standards, all the RAP CPB mixes with filler inclusions fulfilled the acceptance criteria for heavy traffic applications, and water spray curing can enact as an alternate method for curing these mixes. However, to avail maximum performance benefits, it is recommended to use 5% wollastonite, 15% jarosite, and a combination of 10% wollastonite and 10% jarosite as a Portland cement substitute to produce sustainable eco-friendly RAP CPB mixes.

Control of mechanical and hydrophobic properties of silylated chitosan-starch films by cross-linking using carboxylic acids

We prepared polysaccharide films from silylated chitosan cross-linked with starch using six kinds of carboxylic acids (oxalic, maleic, citric, succinic, azelaic and sebacic acids) to explore the effects of molecular structures of cross-linkers on the mechanical, hydrophobic and water vapor permeability properties of these hydrophobicity-enhanced films. The films were analyzed by FT-IR, SEM, mechanical tests (stress versus strain, tensile strength and elongation at break curves) as well as the measurements of water contact angle, water solubility and water vapor permeability rate. We observed that the cross-linkers with a long chain provide a large mechanical strength; the tensile strength increases from 6 to 27 MPa with the chain length of dicarboxylates. The hydrophobicity, evaluated by the contact angle (ranging 80° ∼ 120°), increased with the chain length of the cross-linkers and was correlated well with the decreases of the solubility (94 ∼ 17%) and vapor permeability rate of water (14.5 ∼ 1.5 × 10−12 g s−1 m−1 Pa−1). We demonstrate that these mechanical, hydrophobic and water permeability properties are varied considerably only by the choice of the cross-linking acid also in the hydrophobicity-enhanced film by pre-silylation, which may widen the range of potential applications of polysaccharide film such as food packaging.

Microstructure, water permeability and micromechanical properties of alkali activated slag subjected to accelerated leaching

This study investigated the leaching resistance of alkali activated slag mortars (AAS) under immersion in a 6 M NH4NO3 solution for a duration of up to 28 days, taking into consideration the effect of water-to-binder (w/b) ratio. SEM-EDS analysis revealed decalcification, desodiumization, and dealumination in AASs during leaching, leading to changes in the microstructure and micro-mechanical properties of the materials. A combination of N2-adsorption and MIP analysis demonstrated that there was a coarsening of the structure and an increase in porosity along the depth of degradation in the leached AAS. The predominant pore framework in the leached materials was found to be capillary pores. Furthermore, the elastic modulus and micro-hardness of AAS decreased after 28 days of leaching, as evidenced by micro-indentation. The water permeability of AASs exhibited an exponential rise with the increase in porosity, both before and after leaching, as a consequence of the changes in microstructure. Notably, the w/b ratio significantly influenced the leaching rate, microstructure, and water permeability of the AAS.

Understanding Charge, Mass, and Heat Transfer in Fuel Cells for Transport Applications – Insights from the Camelot Project

Proton Exchange Membrane Fuel Cells (PEMFCs) are a promising solution for zero-emission vehicle propulsion owing to their high energy density, low operating temperature, and high efficiency. The overall aim of the CAMELOT project is to improve the power density of fuel cells by understanding the limitations on the performance of state-of-the-art (SoA) and beyond SoA PEMFC membrane electrode assemblies (MEAs). To achieve this, the CAMELOT project has diagnosed the fundamental transport properties that limit performance of these MEAs and materials. Not only has the CAMELOT project produced MEAs with features that have the potential to enable disruptive performance increases but have further developed leading open-source models to enable accurate simulations validated through experimental work. In-depth parametrisation of fuel cell components through extensive ex-situ and in-situ characterisation has been performed to provide input to the modelling activities. The two major modelling advances achieved by the CAMELOT project are i) the improvement of water uptake and transport models, especially concerning ultra-thin PEMs, and ii) extending a leading open-source model (FAST-FC) to enable accurate simulation of beyond SoA fuel cell performance and voltage loss breakdown. CAMELOT has developed a series of beyond-SoA fuel cell components to ensure that the modelling inputs are representative of SoA component properties. A series of membranes with varying thicknesses were prepared and a range of ex-situ experiments were carried out to gather water uptake and permeability properties for the water transport models. Additional in-situ electrochemical characterisation was carried out on a series of catalyst coated membranes (CCMs) to extract important properties of the catalyst and membrane components as inputs to improve the physics-based fuel cell performance model.Significant results from the project to be highlighted in this presentation include the development of a water transport model with improved description of water uptake and transport in thin ionomeric layers, the development of a predictive modelling framework from which we can identify the most important material parameters to tune to reach our MEA performance targets of 2.7 A/cm2 at >0.67 V with total catalyst loadings <0.08 mgPt/cm2, the development of ultrathin (< 10 µm) proton exchange membranes and ultra-low loading cathode catalyst loadings (0.08 mgPt/cm2), the development of catalyst coated membranes (CCMs) with in-plane catalyst and ionomer gradients, and extensive in-situ fuel cell characterization of the SoA CAMELOT CCMs/MEAs.The CAMELOT project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under grant agreement No 875155. This Joint Undertaking receives support from the European Union’s Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research.

Prototype of alveolar gypsum blocks with plastic waste addition for partition walls: Physico-mechanical, water-resistance and life cycle assessment

The development of eco-friendlier building products incorporating waste as an alternative to raw materials has become increasingly relevant within the construction industry. With this in mind, this study presents a prototype of an alveolar gypsum block for partition walls, wherein partial replacement of the binder (i.e. gypsum or cement) was made using two types of plastic waste (i.e. polypropylene- and nylon-based). Two plastic waste-containing composites, with contents considered as optimum in previous studies (AGB/PP/7.5–7.5 wt% polypropylene content; AGB/PA6/2.5–2.5 wt% nylon content), were produced and extensively analysed in comparison to a reference block. Physico-mechanical (bulk density, surface hardness, flexural and compressive strength), water permeability and thermal properties were evaluated and compared to commercially available counterparts. In addition, the prototypes’ environmental impact was determined by conducting a simplified life cycle assessment primarily based on the “Global Warming Potential” and “Embodied Energy” categories. The results showed a widespread improvement in the mechanical performance of plastic-containing blocks and more so for those reinforced with nylon fibres when compared to the reference product. Furthermore, notable reductions in thermal conductivity and water permeability were observed on the blocks due to the addition of plastic waste. Both types of blocks presented a slight environmental impact decrease because of the reduction of raw materials (i.e. gypsum). These findings are encouraging from a practical application point of view and may create a notable opportunity for replacing more frequently gypsum with polypropylene- or nylon-based wastes for alveolar blocks for building partition walls.

Mechanical and durability properties of structural grade heavy weight concrete with fly ash and slag

The paper investigates the fundamental mechanical and durability properties of a M50 strength grade heavy weight concrete (HWC), with replacement of cement by fly ash at 15 %, 25 % and 35 % levels and slag at 40 %, 50 % and 60 % levels. The mechanical properties studied include compressive strength, elastic modulus, flexural and split tensile strengths, and the durability properties include water permeability, drying shrinkage and carbonation behavior. Although extended curing improves mechanical strength and water permeability properties of fly ash and slag blended HWCs, fly ash replacement reduces the modulus of elasticity of HWC to some extent. A simple relationship was used to estimate the elastic modulus of fly ash and slag based HWCs from their density and compressive strength, and the estimated values agreed well with the experimental results. Experimental investigation shows that the long term drying shrinkage strain for all fly ash based HWCs (15 %–35 %) is lesser than that for the 100 % ordinary portland cement (OPC) and all slag based HWCs. The resultant hardened density variations of fly ash and slag blended concretes exposed to long term controlled environment discussed in this paper can be used for estimating shielding thickness of HWC members against ionizing radiations. The carbonation resistance of fly ash and slag HWCs exposed to 3 % CO2 condition for 146 days is also evaluated. Accelerated carbonation coefficients (kacc) estimated for all types of HWCs show that the carbonation resistance of HWC prepared with 15 % fly ash and 40 % slag is comparable. The rate of accelerated carbonation of HWCs increases for the increase in replacement level of fly ash and slag. In addition to the higher rate of carbonation, increase in calcium carbonate content estimated through micro analytical studies also suggest that a higher level of slag replacement reduces the carbonation resistance of HWC significantly.

Antifouling and antibacterial bioactive metabolites of marine fungus (terrein)/polyamide thin-film composite reverse osmosis membranes for desalination applications

Marine fungi-derived (+)-terrein is grafted onto a reverse osmosis polyamide membrane using glutaraldehyde, forming a thin film composite (Terrein-PA) membrane. This membrane exhibits improved water permeability, antifouling and antibacterial properties. Compared to conventional reverse osmosis membranes, Terrein-PA membrane shows a 51.0 % increase in permeability (7.4 L/m2·h·bar) due to its beneficial hydroxyl groups. It also effectively inhibits the growth of gram-positive and gram-negative bacteria, achieving antibacterial rates of 98.0 % and 94.9 %, respectively. This reduces microorganism adhesion, extending the membrane's service life. The use of natural (+)-terrein is safer for human health than chlorine treatments. Furthermore, when contaminated with bovine serum albumin, Terrein-PA membrane achieves a flux recovery rate of 90.9 % and a total contamination rate of 12.3 %. This study introduces an innovative approach to produce secure antibacterial reverse osmosis membranes with prolonged lifespan.

Evaluation of thermal and freeze-thaw resistances of the concretes with the silica fume addition at different water-cement ratio

The preparation of concrete with improved durability is an essential subject in the development of building and construction materials. This study presents the preparation and characterization of a high-strength concrete by activating ordinary 42.5 grade Portland cement (OPC) with silica fume (SF). The effect of the SF addition and water-cement (W/C) ratio on concrete durability including freeze-thaw, water permeability, mechanical and thermal resistance properties have been determined. When the water-cement ratio (W/C) in the SF added concrete is appropriately designed, for example, W/C 0.23, the compressive strength was 92.85 MPa, water absorption 0.7 %, 420 freeze-thaw cycles and water impermeability is W20. Residual strength of this concrete after thermal explosion at 600 °C for 2 h was 82 % of the original plain concrete, indicating that the obtained value is the true dense concrete. It also shows the concrete slump flow of 630 mm, which indicates its self-compacting behavior. The concrete prepared with W/C 0.29 achieved 365 freeze-thaw cycles, had 65.1 MPa compressive strength, W14 water impermeability, 1.8 % water absorption and 69 % residual strength after the thermal explosion at 600 °C. Concrete with washed aggregates has higher mechanical properties than concrete with unwashed aggregates. Freeze-thaw resistance has a direct relationship with the percentage of residual strength after explosion at 600 °C in all W/C ratios tested. Better durability and high resistance to temperature explosion was caused by the beneficial formation of the calcium silicate hydrate phase (C-S-H) in the silica fume added concrete.

Investigating Correlations and the Validation of SMAP-Sentinel L2 and In Situ Soil Moisture in Thailand.

Soil moisture plays a crucial role in various hydrological processes and energy partitioning of the global surface. The Soil Moisture Active Passive-Sentinel (SMAP-Sentinel) remote-sensing technology has demonstrated great potential for monitoring soil moisture with a maximum spatial resolution of 1 km. This capability can be applied to improve the weather forecast accuracy, enhance water management for agriculture, and managing climate-related disasters. Despite the techniques being increasingly used worldwide, their accuracy still requires field validation in specific regions like Thailand. In this paper, we report on the extensive in situ monitoring of soil moisture (from surface up to 1 m depth) at 10 stations across Thailand, spanning the years 2021 to 2023. The aim was to validate the SMAP surface-soil moisture (SSM) Level 2 product over a period of two years. Using a one-month averaging approach, the study revealed linear relationships between the two measurement types, with the coefficient of determination (R-squared) varying from 0.13 to 0.58. Notably, areas with more uniform land use and topography such as croplands tended to have a better coefficient of determination. We also conducted detailed soil core characterization, including soil-water retention curves, permeability, porosity, and other physical properties. The basic soil properties were used for estimating the correlation constants between SMAP and in situ soil moistures using multiple linear regression. The results produced R-squared values between 0.933 and 0.847. An upscaling approach to SMAP was proposed that showed promising results when a 3-month average of all measurements in cropland was used together. The finding also suggests that the SMAP-Sentinel remote-sensing technology exhibits significant potential for soil-moisture monitoring in certain applications. Further validation efforts and research, particularly in terms of root-zone depths and area-based assessments, especially in the agricultural sector, can greatly improve the technology's effectiveness and usefulness in the region.

Highly permeable PA@GO loose nanofiltration membranes enabled by hierarchical transport channels for efficient dye removal

Graphene oxide (GO) membranes exhibit ultrafast water permeation properties, which have been employed in various membrane-based separations including nanofiltration for dye removal from textile wastewater. However, it’s still a great challenge to achieve precise control over the microstructure of GO membranes and obtain ultrathin GO membranes with exceptional separation efficiency and robust membrane structure. Herein, in-situ confined interfacial polymerization (IP) is proposed for fabricating loose polyamide (PA)@GO hybrid membranes with high permeance and dye rejection as well as robust membrane stability. A new diamine of sulfadiazine (SA) with intrinsic hydrophilic and conjugated sulfonamide groups is employed as cross-linker of GO membranes and monomer of PA in IP process, simultaneously. PA is in-situ synthesized in confined GO interlayer via IP process and intercalated into GO interlayer, which enlarges the interlayer spacing of GO membranes gradiently. The combination of hydrophilic PA nanofiltration layer on GO membrane surface and the PA intercalated GO membrane with varying interlayer spacing creates hierarchical transport channels for water molecules, which contributes to the high water permeance. Moreover, the less reactive SA monomer endows PA@GO selective layer with appropriate negative charge and loose transport channels, which contributes to both of high permeance and dye rejection due to Donnon effect and size exclusion effect. The PA@GO hybrid membrane exhibits high permeance of 75.5 L/(m2·h·bar) with TB dye rejection of 99.8 %, and exhibits low NaCl rejection of 11.6 %. Moreover, PA@GO hybrid membrane shows good fouling resistance and long-term stability as well as stable separation performance under harsh conditions. Both of high permeance and dye rejection of PA@GO hybrid membrane suggests that the integration of PA nanofiltration layer and GO membrane via in-situ confined interfacial polymerization can achieve the delicate control over the interlayer channel structure and the physicochemical properties of the membrane surface of GO membranes, which offers a promising method to break through the trade-off effect between permeability and selectivity of GO membranes.

Modelling in the frame of hydro-mechanical infiltration column experi-ment to study the behaviour of binary mixtures of bentonite MX80

Binary mixtures of high-density MX80 bentonite pellets (80% mass ratio at a dry density of 2.0 Mg/m3) and powder (dry density of 1.1 Mg/m3) at hygroscopic water contents are studied by the French Institute of Radiation Protection and Nuclear Safety (IRSN) as an alternative in engineered barrier systems for the long-term disposal of radioactive wastes. The MX80 bentonite was studied by many authors [1–4] with this aim. These mixtures show a dry density around 1.49 Mg/m3 on pouring into infiltration column experiment tests.&#x0D; An infiltration column cell (100 mm in diameter and 350 mm high) has been developed at a reduced scale of 1/100 of the VSS (i.e., at 1/10 of the in situ VSEAL test) to reproduce asymmetric hydration using independent top (fast injection) and radial (slow injection) water pressure systems, which will undergo fast hydration from the calcareous Oxfordian formation at the top and a slower one by water reaching radially through the Callovo-Oxfordian formation. It also allows performing gas injections at different locations of the core of the bentonite mixture (top and bottom boundaries) and under various hydraulic states. The infiltration column is composed of four transparent cylinders, made of Perspex to visualise processes occurring at the interface during the hydration and gas injection phases (Figure 1a). This cell has been assembled with three stainless-steel injection rings that ensure slow radial water injection through three independent automatic pressure/volume controllers. These stainless-steel injection rings also hold the different lateral transducers (six total stress cells and three water pressure transducers embedded in the soil and three relative humidity probes installed in small dismountable chambers) (Figure 1a). The assembled cell is inserted into a rigid frame composed of two stainless steel disks on the two sides of the cylinder connected by four metallic rods.&#x0D; A numerical model has been developed to better understand the coupled hydro-mechanical response of this multi-porosity mixture and particularly of its constitiuents upon hydration.The characterisation of pellet and powder components have been focused on their water retention properties, water permeability, compressibility on loading and on suction changes, as well as on their swelling pressure response and the progressive changes of their pore size distribution on wetting. This information at component scale has allowed the upscaling into a 2D plane-strain numerical model based on the discretisation of pellets and inter-pellet powder using Code_Bright FEM [5]. This plane-strain model captures the pellet shape effect without changing the geometry of the pellets.The geometry used in the simulations corresponds to an infiltration column at constant volume mimicking the actual asymmetric hydraulic conditions of the VSS. Figure 2b presents the geometry of the model used at constant volume based on the discretisation of pellets and powder (252 pellets of 8 mm diameter and surrounded by powder filling the entire inter-pellet volume).The generated numerical mixture has a mass-basis proportion of 77.6% pellets and 22.5% powder, which is close to the mixture proportion. Figure 1b shows the three lateral slow-rate hydration boundaries, as well as the fast-rate hydration boundary at the top. The modelling has focused on analysing the global and particularly the local responses: water mass transfer between powder and pellets, evolution of local degrees of saturation and porosities (inside pellets and powder), and mean stress evolution in the pellet and powder domains. Water retention and permeability properties of the components are dependent on porosity and the degree of saturation.&#x0D; A non-linear elastic model has been considered for the components, in which volumetric deformations are induced by net mean stress and suction changes. Therefore, the pellets and powder have different hydraulic and mechanical properties as a consequence of the different initial properties, but they share the same constitutive relationship of a single structured material. Figure 1c presents the time evolution of porosities (inside the pellets and powder), showing that the mixture tends towards a more homogeneous distribution of porosity as the pellets expand and compress the highly deformable clay powder. During the transient hydration stage, the expansion of pellets at the top of the column evolves faster due to the proximity of the hydration front. Figure 1d shows the water retention curves of the pellets and powder at the initial state and after hydration as predicted by the model, compared to experimental data [6,7]. The predicted water retention curves of the pellets and powder adequately follow the trend of the data reported by [7] and also seem to reproduce the mixture model data suggesting a homogenisation of the retention properties of the material after hydration.

Brick-concrete recycled aggregate/powder synergistic preparation of pervious concrete

In order to improve the resource utilization rate of brick-concrete construction waste (BC-CW) and meet the demand of 'sponge city' construction for pervious concrete, a kind of brick-concrete recycled pervious concrete (BC-RPC) was prepared by brick-concrete recycled aggregate (BC-RA) / powder (BC-RP). The design was carried out from the two levels of cementitious material pastes and aggregate. Firstly, BC-RP was used as the main silicon-aluminum raw material to prepare a brick-concrete recycled powder based geopolymer (BC-RPG) for pervious concrete. It was determined that the content of BC-RP in BC-RPG was 50%, and the alkali content and modulus of the best alkali activator were 12% and 1.2, respectively. Then, the effect of BC-RA gradation and substitution rate on the mechanical properties of BC-RPC was studied by using BC-RPG as cementitious material and BC-RA as aggregate. The method of 'double grain composite substitution' was proposed to control the strength loss rate of BC-RPC. At the same time, the volume structure parameters (design porosity and pastes-aggregate ratio) of BC-RPC were optimized, and the optimum design porosity and pastes-aggregate ratio for BC-RPC preparation were determined to be 27% and 0.39, respectively. Finally, BC-RPC with coordinated mechanical and water permeability properties was prepared.

Fabrication and modification of PVDF membrane by PDA@ZnO for enhancing hydrophilic and antifouling property

There is an urgent need for an antifouling membrane to treat the large volume of dye-containing wastewater generated annually by the dyeing and printing industry. PDA@ZnO/PVDF membranes were synthesized by doping polydopamine (PDA) and zinc oxide (ZnO) nanoparticles into the polyvinylidene fluoride (PVDF) membranes via non-solvent induced phase separation (NIPS) method in which polyvinylpyrrolidone (PVP) and lithium chloride (LiCl) were chosen as the porogens respectively. Their microstructures were characterized, and the membranes were examined for antifouling properties and membrane separation performance. The presence of PDA@ZnO nanoparticles on the PVDF membrane was evidenced by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) measurements. The addition of PDA@ZnO enhanced the mechanical strength and hydrophilicity of the nanocomposite membranes. The PVDF membranes' water permeability and antifouling properties improved following mixing modification, according to the dye filtration test. The pure water flux of PDA@ZnO/PVDF hybrid membranes changed from 260.0 L·m−2·h−1·bar−1 to 1339.2 L·m−2·h−1·bar−1 by varying the concentration of PDA@ZnO nanoparticles from 0 wt% to 1.6 wt%. The retention performance of the modified membranes was shown to be significantly superior to the pure PVDF membrane. The modified membranes with the addition of 2.0 wt% PVP and 1.6 wt% PDA@ZnO nanoparticles had highly disperse blue 79 (DB 79) retentions (88.5%), indicating that the modified membrane possessed the characteristics of a promising membrane for the purification of dye. Tests found that PDA@ZnO significantly improved the membrane's antifouling performance.

Study on the Effect of Fly Ash Admixture on the Performance of Recycled Pervious Concrete

In order to solve the problems of recycling of a large amount of coarse aggregate produced after the crushing of waste concrete and urban flooding, this project prepares the recycled coarse aggregate of 4.75-9.5 mm into 100 mm × 100 mm × 100 mm cubic permeable concrete specimens, and researches the influence law of different fly ash admixture on the pore space, water permeability and mechanical properties of the recycled aggregate permeable concrete, and determines the best design The optimal design ratio was determined. The experimental results show that the permeable concrete specimens prepared with recycled coarse aggregate of 4.75-9.5mm particle size and mixed with fly ash were cured in water, and the longer the curing age, the higher the compressive strength. With the increase of fly ash dosage, the compressive strength first rises and then decreases, and the porosity and permeability coefficient decreases continuously. When the fly ash dosage is 15%, the 28d compressive strength of recycled aggregate pervious concrete is the highest, which is 12.8 MPa. At this time, the porosity is 23.9%, and the permeability coefficient reaches 3 mm/s. Considering the overall situation, the optimum dosage of fly ash for recycled aggregate pervious concrete is recommended to be about 15%.

Zwitterionic loose polyamide nanofiltration membrane with good antifouling properties for efficient removal of humic acid and dyes

Loose nanofiltration membrane exhibits significant advantages in removing organic pollutants due to its high selectivity at a lower operating pressure. Herein, a novel zwitterionic loose polyamide separation layer was designed and formed on the modified polyethersulfone substrate to obtain the zwitterionic loose nanofiltration (ZLNF) membrane with high water permeability and good antifouling properties. The BAPP-TMC polyamide layer was fabricated by the interfacial polymerization between 1,4-bis(3-aminopropyl)piperazine (BAPP) and trimesoyl chloride (TMC). Afterward, the BAPP-TMC polyamide layer was grafted with zwitterions by a facile surface modification. Owing to the fabrication of the relatively loose polyamide structure with zwitterions, the prepared ZLNF-0.2 membrane presented an ultra-high pure water permeability of 148.5 L m−2 h−1 bar−1 while maintaining relatively good removal capacities for organic pollutants. The removal rates for humic acid (HA, 100 ppm) and Congo Red (CR, 100 ppm) were 98.1 % and 97.6 %, respectively. Furthermore, the good hydrophilicity and strong surface hydration effect of zwitterions endowed the ZLNF membranes with excellent anti-organic fouling and antibacterial adhesion properties. The good antibacterial abilities of ZLNF membranes were also proved by the fluorescence staining results. Due to the effective separation performance and good antifouling properties, the fabricated ZLNF membranes present great application potential in removing natural organic matter and dyes.

High-performance thermoplastic starch/poly(butylene adipate-co-terephthalate) blends through synergistic plasticization of epoxidized soybean oil and glycerol

Utilizing starch, an abundant polysaccharide, as the renewable filler to blend with poly(butylene adipate-co-terephthalate) (PBAT) is a feasible tactic to construct cost-effective and high-performance biodegradable materials. It's worth noting that the thermal processing properties of starch can be manipulated by its plasticized behavior. Herein, epoxidized soybean oil (ESO) and glycerol were used as the plasticizer for native corn starch and the plasticized starch was integrated with PBAT to manufacture starch-based biodegradable blend films. ESO breaks the hydrogen bonds between starch chains through the fatty chains grafting reaction and increases the distance between starch molecular chains due to the large molecular weight of ESO. Meanwhile, glycerol molecules are incorporated into the starch molecular chains, and fatty chains grafted starch chains, effectively reducing the intermolecular forces of molecular chains. On account of the synergistic plasticization of ESO and glycerol which possess good compatibility with PBAT, the PSG20E10 blend film achieved a tensile strength, an elongation at break of 16.11 MPa and 612.09 %, and the balanced water and oxygen permeability properties.

Effect of hexagonal-boron nitride nanosheets (h-BNNSs) on the structural morphology and performance of polyvinylidene fluoride (PVDF) membranes for water-oil separation

Hexagonal-boron nitride nanosheets/polyvinylidene fluoride (h-BNNSs/PVDF) composite membranes were successfully fabricated through a facile one-step phase inversion process. The amount of h-BNNSs incorporated into the PVDF membranes was varied within the mass percent range of 0–3 %, and the influence of the membranes' structural properties on water-oil separation was investigated. Surface roughness and wettability analyses (water contact angle data) showed that the membranes are hydrophilic, and the average surface roughness measurements reveal that the presence of h-BNNSs enhances the wettability of the composite membranes. In addition, h-BNNSs in composite membranes increased the total porosity which favoured enhanced membrane separation flux. Scanning electron microscopy investigations revealed flat surfaces with porous structures, sponge-like morphology and granular-like porous structures. The performance of the composite membranes for water-oil separation revealed that the addition of h-BNNSs to the membrane polymeric matrix resulted in enhanced selectivity towards water with the highest flux of 384.96 L/m2h, and selectivity efficiency of 99.60 % for a 3 % h-BNNSs/PVDF composite membrane, with no transmembrane pressure applied. The preference for water as a filtrate is attributed to the superior water permeation properties of the h-BNNSs and PVDF interaction. Water permeability was due to the presence of positively charged B atoms which pull the oxygen atoms in the water molecules. The improvement in fluxes of the investigated membranes, upon the addition of h-BNNSs makes them excellent candidates for water-oil emulsion separations.

Preparation, Properties and Application of Homogeneous Polypropylene Cation Exchange Membrane

Electrodeionisation (EDI) is one of the most important methods for the separation and purification of heavy metal ions from wastewaters. Acrylic acid (AA) and butyl acrylate (BA) were grafted onto polypropylene nonwoven to prepare cation exchange membranes, which were used for EDI treatment of simulated Cu(II) wastewater. The effects of the ratio of two monomers, initiator and crosslinker on the microstructure, mechanical and electrochemical properties of the resultant homogeneous polypropylene membranes were investigated. The experimental results show that at the conditions of AA: BA = 2:1, BPO 3.75%, and PETA 7%, a grafting rate of over 240% is achieved with high IEC, low water permeability and good mechanical properties. However, too much crosslinking makes area resistance high. Compared to commercially available heterogeneous membrane, the resultant membranes have better Cu(II) separation, longer service life but lower current efficiency.

Study on Influencing Factors of Paste Coating Thickness of Pervious Concrete

Pervious concrete (PC) is a multifunctional material with good water permeability, noise reduction, and heat absorption properties. The most critical performance indicators of the PC are permeability and strength, which are mainly affected by the cement paste coating thickness (PCT) on the aggregate surface. The experiment was carried out to study the influence of the water–cement ratio, superplasticizer dosage, aggregate roughness, and aggregate size on PCT, and a new normalization method was proposed for grey correlation analysis to determine the influence degree of the above factors on PCT. Finally, fitting models for predicting the PCT were established based on experimental data. The experimental results indicate that the influence of the water–cement ratio on PCT can be divided into two stages, whereby the PCT shows a slow decline and then a rapid decline with the increase in water–cement ratio; with the increase in superplasticizer dosage, the PCT represents an exponentially decreasing trend; the PCT increases with the aggregate size and aggregate roughness. Based on the grey correlation analysis, the superplasticizer dosage exerts the greatest influence on PCT, followed by the water–cement ratio, aggregate size, and aggregate roughness. The results of this study revealed the change law of PCT under the action of the above factors, which established the premise of controlling the strength and permeability of PC from the perspective of the PCT and provided a reference for the mixture proportion design.

One-pot preparation of a carboxylated nanocrystalline cellulose from oil palm fronds as hydrophilic additive for enhancement of membrane permeability and anti-fouling properties

Most polymeric membranes, including polyethersulfone (PES), are limited in their application due to their low water flux and high fouling characteristic. In this study, carboxylated nanocrystalline cellulose (C-NCC) embedded PES membrane was fabricated using the non-solvent induced phase inversion (NIPS) method to enhance the water permeability and anti-fouling properties of the PES membrane. Herein, we synthesized our C-NCC from oil palm fronds (OPFs) using a simple and time-efficient one-pot mixed acid hydrolysis method. The as-prepared C-NCCOPF exhibited a rod-like structure with dimensions of 121.03 ± 65.30 nm and 15.64 ± 5.42 nm in length and width, respectively. The degree of oxidation value of 0.21 was obtained, comparable to those C-NCC synthesized using the classical TEMPO or APS oxidation procedures. By incorporating C-NCCOPF nanorods into the PES matrix, the hydrophilicity, pore structure, mean pore size, porosity, and pure water flux of the modified membrane were significantly enhanced. The Hermia model and Bolton's combined fouling model were applied to investigate the anti-fouling properties of the fabricated membrane during the HA filtration at 1 bar operating pressure. The results demonstrated that the pristine PES membrane was susceptible to fouling which is likely related to the hydrophobic nature of the PES polymer. In contrast, it was discovered that incorporating the C-NCCOPF into the PES membrane could significantly reduce fouling and enhance membrane performance.