Fine Pore Structure Research Articles

燃料電池の膨張触媒層の3次元構造のクライオSTEMトモグラフィー

In order to improve the power generation properties of fuel cells, it is important to understand and control the fine pore structure of the fuel cell catalyst layer, which affects the flow of gas and water. It is inferred that the ionomer having a hydrophilic group is in a swollen state when a fuel cell is operating because of the high temperature and high humidity state of the catalyst layer. Therefore, in order to understand the flow of gas and water, information is required not only on the pore structure due to Pt/C aggregates but also on the distribution state of the swollen ionomer. A three-dimensional observation method is needed to obtain the three-dimensional structural information necessary for detailed analysis of the correlation between performance evaluation results, such as electrical characteristics, and electrode structures. Detailed investigation of the fine pore structure of a fuel cell catalyst layer requires electron microscopy techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM) due to the scale involved. However, since a typical electron microscope is a vacuum device, materials containing moisture are observed in a dry state. Furthermore, data are obtained as images, which are basically two-dimensional. Cryo-electron microscopy is a method that allows samples containing water and particles in liquid to be observed while being kept in a wet state without drying them, as the sample is quickly frozen and observed in that condition with an electron microscope. Cryo-electron microscopy has been established mainly in biological fields, and there are many issues to be solved in adapting it to investigations of materials. For example, in biological fields, objects to be observed are basically composed of light elements, while heavy elements are included in the materials field. In addition, the solvents are not only water but also mixed ones of organic solvents, and the freezing conditions and tendency of electron beam irradiation damage during observation are also different, requiring a different approach from that used in biological fields. Electron tomography is a three-dimensional observation method using TEM, in which information on the three-dimensional structure of a sample can be obtained by continuously tilting it and performing Radon-inverse Radon conversion from the obtained transmission image. Since many images are acquired during continuous tilt imaging, it is important to control the electron beam dose to the sample for samples that are susceptible to electron beam irradiation damage. To address these issues, a low-dose scanning transmission electron microscopy (STEM) mode creates a parallel electron beam without converging the beam, which suppresses electron beam irradiation damage and emphasizes scattering contrast, though it has the disadvantage of reducing resolution. It is thus expected that this method will also be effective in distinguishing between ionomers and carbon. Since the catalyst layer contains heavy elements such as precious metals, STEM observation is considered to be even more optimal as it has higher transparency than TEM. In this research, we used cryo-STEM tomography to analyse differences in the pore structure in the swollen ionomer of catalyst layers of samples with different electrical properties, and investigated the correlation between the pore structure and those properties. Three types of catalyst layers samples were fabricated using commercial catalyst powder (TEC10V30E, TKK) and Nafion as the ionomer with different ionomer-to-carbon ratios (I/C:0.1, 0.5, 1.0) for the analyses. Cell performance was investigated on MEAs with the catalyst layers for the cathodes, respectively. The performance at 80°C and 80% was lower for the samples with lower I/C. The performance of the I/C=0.1 sample was especially low, which was primarily attributed to the low catalyst utilization and high proton resistance. In order to understand these phenomena, we investigated in detail the three-dimensional distribution of the ionomer in the porous structure composed of Pt/C aggregates and compared the results found for the samples. This work is partly supported by NEDO FC-Platform project.

Nickel–titanium alloy porous scaffolds based on a dominant cellular structure manufactured by laser powder bed fusion have satisfactory osteogenic efficacy

Nickel–titanium (NiTi) alloy is a widely utilized medical shape memory alloy (SMA) known for its excellent shape memory effect and superelasticity. Here, laser powder bed fusion (LPBF) technology was employed to fabricate a porous NiTi alloy scaffold featuring a topologically optimized dominant cellular structure that demonstrates favorable physical and superior biological properties. Utilizing a porous structure topology optimization method informed by the stress state of human bones, two types of cellular structures—compression and torsion—were designed, and porous scaffolds were produced via LPBF. The physical properties of the porous NiTi alloy scaffolds were evaluated to confirm their biocompatibility, while their osteogenic efficacy was investigated through both in vivo and in vitro experiments, with comparisons made against a traditional octahedral unit cell structure. NiTi alloy porous scaffolds can be nearly net-shaped via LPBF and exhibit favorable physical properties, including a low elastic modulus, high hydrophilicity, a specific linear expansion rate, as well as superelastic and shape memory effects. These scaffolds demonstrate excellent biocompatibility, support in vitro osteogenesis, and possess significant in vivo bone ingrowth capabilities. When compared to titanium alloys, NiTi alloys show comparable osteogenic properties in vitro but superior bone ingrowth properties in vivo. Additionally, among octahedral-type, torsion-type, and topologically optimized compression-type porous scaffolds, the latter demonstrates enhanced bone ingrowth properties. LPBF technology is effective for manufacturing porous NiTi alloy scaffolds with fine pore structures and excellent mechanical properties. The scaffolds based on topologically optimized dominant cellular structures facilitate satisfactory and efficient bone formation.

Study on 3D printing a fine quality bone-mimetic porous structure with minimized shape error in pore size: a parametric work on key laser parameters in SLM

Study on 3D printing a fine quality bone-mimetic porous structure with minimized shape error in pore size: a parametric work on key laser parameters in SLM

Impact of freeze-thaw cycles on the remobilization behaviors of microplastics in natural soils

Freeze-thaw (FT) cycle would greatly influence the fate of plastic particles (one of emerging contaminants with great concerns) in soils, yet its impacts and mechanisms remain unclear. The vertical migration/release behaviors of plastic particles (with diameters of 0.2 μm and 1 μm) in two natural soils and one model soil (i.e. quartz sand) without/with FT treatments (1 and 3 cycles) were examined. Owing to the presence of Fe/Al oxide minerals, finer pore structure, and uneven surfaces of natural soils, the breakthrough ratio of plastics in two natural soils was over 25% lower than in quartz sand. However, regardless of porous media type, FT processes (increasing cycles) significantly promoted the remobilization of plastics initially retained in three media during the subsequent water flushing processes. Via theoretical calculation, tracer experiments, and visible chamber experiments, the mechanisms driving plastics release from natural soils subjected to FT treatments during the water elution processes were determined to be different from those from pure quartz sand. The change of sand local configuration (the rearrangement of local sand pore spaces) during FT process mainly drove to plastics released from quartz sand columns. While the alteration in local soil configuration, the formation of preferential pathways, and increased release of soil particles contributed to plastics remobilization from soil columns subjected to FT. Clearly, FT processes significantly increased the vertical migration of plastics in soils potentially to groundwater, enhancing environmental risks of plastics.

MOF-based photothermal Janus membrane with robust anti-fouling performance for enhanced membrane distillation

As a promising desalination technology, photothermal membrane distillation (PMD) is confronted with challenges such as low freshwater yield and membrane fouling. Herein, we have introduced a copper-based metal-organic framework (Cu-CAT) into a hydrophilic/superhydrophobic polyvinylidene fluoride (PVDF) Janus tree-like nanofiber membrane (TLNMs) to construct photothermal Janus TLNMs (P-Janus TLNMs) for enhanced PMD. Given the exceptional photothermal properties of the hydrophilic Cu-CAT layer, coupled with the fine pore structure and elevated porosity characteristics of the superhydrophobic PVDF TLNMs, P-Janus TLNMs have demonstrated outstanding performance when integrated into a PMD system. Upon exposure to solar illumination of 1 kW·m−2, the P-Janus TLNMs achieved a remarkable surface temperature of 88 °C, yielding a permeation flux of 1.46 L m−2 h−1, a salt rejection rate exceeding 99.99 %, and an energy utilization rate of 81 %. Furthermore, after 20 days of continuous operation with simulated seawater containing oil and surfactant, the P-Janus TLNMs presented a salt rejection of 99.9 % and a stable permeation flux of 1.71 L m−2 h−1 at the feed/permeate temperatures of 24/20 °C. This work introduces a novel membrane with immense potential for boosting permeation flux and enhancing anti-fouling properties in PMD, thereby advancing the frontier of sustainable seawater desalination.

Determination method and application of variable T2 cutoff value in nuclear magnetic logging

Abstract Nuclear magnetic resonance logging (NMR) is a new logging technology. By inversion of relaxation time T2 spectrum, pore characteristics can be directly measured, independent of the influence of rock skeleton minerals, and parameters such as effective porosity, movable fluid porosity, bound water porosity, pore size distribution and permeability can be calculated. The key parameter for calculating fine pore structure is the critical relaxation time of bound water and mobile fluid, namely the T2 cutoff value. The current T2 cutoff value is a fixed value based on the T2 mean value corresponding to the flowable porosity (permeability contribution porosity) in the mercury injection experimental data. However, according to the analysis of mercury injection data, there are differences in the flowable porosity of cores with the same porosity and permeability under the same pressure difference. Based on the synchronous data of nuclear magnetic logging and core mercury injection experiment, this paper establishes a variable T2 cutoff value determination method, which significantly improves the interpretation accuracy of nuclear magnetic logging and lays a foundation for the important application of nuclear magnetic logging in reservoir fine description.

Foam Stabilization Process for Nano-Al2O3 and Its Effect on Mechanical Properties of Foamed Concrete.

Foamed concrete is increasingly utilized in engineering due to its light weight, excellent thermal insulation, fire resistance, etc. However, its low strength has always been the most crucial factor limiting its large-scale application. This study introduced an innovative method to enhance the strength of foamed concrete by using nano-Al2O3 (NA) as a foam stabilizer. NA was introduced into a foaming agent containing sodium dodecyl sulfate (SDS) and hydroxypropyl methylcellulose (HPMC) to prepare a highly stable foam. This approach significantly improved the foam stability and the strength of foamed concrete. Its drainage volume, settlement distance, microstructure, and stabilizing action were investigated, along with the strength, microstructure, and hydration products of foamed concrete. The presence of NA effectively reduced the drainage volume and settlement distance of the foam. NA is distributed at the gas-liquid interface and within the liquid film to play a hindering role, increasing the thickness of the liquid film, delaying the liquid discharge rate from the liquid film, and hindering bubble aggregation, thereby enhancing foam stability. Additionally, due to the stabilizing effect of NA on the foam, the precast foam forms a fine and uniform pore structure in the hardened foamed concrete. At 28 d, the compressive strength of FC0 (0% NAs in foam) is 2.18 MPa, while that of FC3 (0.18% NAs in foam) is 3.90 MPa, increased by 79%. The reason for this is that NA promotes the formation of AFt, and its secondary hydration leads to the continuous consumption of Ca(OH)2, resulting in a more complete hydration reaction. This study presents a novel method for significantly improving the performance of foamed concrete by incorporating NA.

Tailoring texture and functionality of vegetable protein meat analogues through 3D printed porous structures

This study presents a comprehensive 3D printing process for plant-based meat alternatives, covering ink formulation, printing, and final product characterization. Traditionally, achieving desired food properties requires extensive exploration of ink components. Here, we demonstrate the potential of manipulating processing parameters instead of ink composition. Two structures were printed, differing only in extrusion temperature. The printed structures exhibited a dimensional accuracy slightly below 100%. We investigated their behavior through simulated food production cycles, including freezing, thawing, dehydration, and rehydration. Rheological measurements revealed that protein denaturation caused a 20% increase in viscosity. Temperature-induced protein denaturation allowed to produce 3D printed samples with a fine porous structure, with pore sizes ranging from 50 to 450 μm. Mechanical characterization showed that a single printing parameter (extrusion temperature) significantly impacts the final product mechanical properties, with an increase of about 50% in the maximum stress for denatured samples after rehydration. This novel approach simplifies 3D-printed protein-based food production, establishing a link between processing parameters and the final product mechanical behavior.

Development of binders based on the СаО–Fe2O3 system

The object of research is the processes of structure formation and modeling of the properties of a specialized binder. The development of new binding materials based on production waste with high early strength indicators could make it possible to speed up construction period and is one of the urgent tasks at present. This study focused on the creation of binders based on the СаО–Fe2O3 system. The developed binder of the СаО–Fe2O3 system has the following composition: limestone – 26 %; red slime – 74 %, which has a dense fine-porous structure and high early strength indicators – 22.5 MPa with a density of 1960 kg/m3. There is also an increase in the average density of samples annealed at a temperature of 1200 ℃ for 60 minutes, ground and mixed with water, in comparison with samples fired at 1100 ℃ for 60 minutes, by 500 kg/m3, due to new formations. The prospect of using modified composite binders with special functional properties has been substantiated. The use of production waste based on the СаО-Fe2O3 system could make it possible to obtain materials with high physical and mechanical properties, which makes them promising for application in various areas of the construction industry. The development of such binders will help reduce the environmental impact of the construction industry, owing to the use of affordable and effective components. This approach will not only contribute to the improvement of the quality of building materials but also help reduce the ecological burden on the environment by using alternative resources and industrial waste. The developed binder could be used for the development of solutions for 3d printing, as well as repair of concrete coatings

Transparent Cellulose Aerogels from Concentrated Salt Solutions: Synthesis and Characterization

AbstractIn this work, nanostructured and transparent cellulose aerogels are synthesized via a purely salt induced approach from non‐modified microcrystalline cellulose type II. The production process requires in contrast to state of the art methods no pretreatment of cellulose or use of expensive cellulose‐solvents: it consists of hydrogel formation via cross‐linking of cellulose with calcium ions, a solvent exchange and a supercritical drying step. A systematic multiparameter study reveals that a high level of structural control is achievable: ratios of macro‐ to mesoporosity and the size of mesopores can be tailored by adjustment of the calcium ion content, while keeping a high overall porosity in the range of 92% – 96 %. The build‐up of homogeneous, fine pore structures results in a significant increase of the specific surface area as compared to conventional calcium‐free aerogels (684 vs. 300 m2 g−1). Remarkably, the Ca2+‐cross‐linking renders aerogels transparent, with Rayleigh scattering being the dominant scattering mechanism. Additional ion exchange to Ca2+ in the hydrogel‐state leads to further reduction of the pore size and to products with optimized optical properties, e.g., light transmission of 91% at an incidents light wavelength of 800 nm and a substrate thickness of 1.5 mm.

Magnesium sulphate resistance of fly ash one-part geopolymers: Influence of solid alkali activators on physical, mechanical and chemical performance

The commitment to promoting circular economy and durable construction materials has led to the advocacy for one-part geopolymer (OPG), as an eco-friendly substitute for traditional ordinary Portland cement (OPC). Solid alkali activator is the fundamental component of OPG and significantly influences the sulphate resistance. To identify the types of solid alkali activators best suited for the development of sulphate-resistant OPGs, OPGs activated with Na2SiO3 (M-OPG), Na2SiO3+Na2CO3 (MC-OPG), Na2SiO3+NaOH (MH-OPG) and Na2SiO3+NaAlO2 (MA-OPG) were exposed to 5 % and 10 % of MgSO4 solutions for 28 days. The fine pore structures of MH-OPG and MC-OPG mitigated deterioration from the more concentrated MgSO4 solution, resulting in higher residual compressive strengths after exposure to the 10 % MgSO4 compared to the 5 %. Exposure to the 5 % MgSO4 solution resulted in strength deterioration for M-OPG, MH-OPG and MC-OPG due to the discontinuity of the aluminosilicate structure, as evidenced by the diminished Q4(3Al) sites. Conversely, the MA-OPG exhibited a 24.1 % increase in compressive strength, accompanied by the emergence of sodium magnesium aluminium silicate hydrate ((N,M)-A-S-H) gel. Hence, Na2SiO3+NaAlO2 should be acknowledged as the primary candidate for solid alkali activators in the development of sulphate-resistant OPGs.

Electrospun nonwoven fabric of poly(ε-caprolactone)/n-phosphonium chitosan for antiviral applications: Fabrication, characterization, and potential efficacy

This work reports the virucidal properties of nonwoven fibers developed via electrospinning with polycaprolactone (PCL) and chitosan quaternized with phosphonium salt (NPCS), emphasizing the influence of NPCS concentration on the structure of fibers and their performance against the MHV-3 coronavirus. The addition of NPCS enhances solutions conductivity and viscosity, leading to fibers containing a finer porous structure with a more hydrophilic and smoother surface, thereby making them a potent barrier against respiratory particles, which is a key factor for protective face masks. In terms of degradation, NPCS paced-up the process, suggesting potential environmental benefits. PCL/NPCS (90/10) fibers exhibit a 99 % coronavirus inhibition within a five-minute exposure without cellular toxicity, while also meeting breathability standards for medical masks. These findings suggest the use of NPCS as a promising strategy to design materials with remarkable virucidal performance and physical characteristics that reinforce their use in the field of biomaterials engineering.

Utilization of recycled coral sand and aluminum scraps in foam concrete: Preparation, insulation of environmental noise and heat, and pore structure

The utilization of industrial and marine wastes in building materials can significantly mitigate resource consumption and environmental hazards. In this study, the waste aluminum scraps and coral sand were utilized as foaming agent and fillers for foam concrete (FC) to address application challenges associated with industrial and marine wastes. Simultaneously, their impact on the mechanical property, heat and noise insulation properties, as well as pore structure of FC were investigated. The response surface methodology was used to optimize the mix design of FC. Heat and noise insulation characteristics of FC were tested by a visible infrared thermometer and a self-manufactured soundproof device, while the pore characteristic was analyzed by digital image processing technique. Additionally, the effect of foaming agents and coral sand on the internal pore structure of FC was studied by means of microscopic analysis(FTIR, XRD, SEM). The results show that foam content significantly influenced the performance of FC. As the foam content reached 15%, the compressive strength was the worst (ranging from 1.26 to 1.59MPa). Additionally, foam and coral sand inhibited the expansion of sulfoaluminate cement. At 15% foam content and 30% coral sand content, the thermal conductivity decreased to 0.082 W/(m·℃), representing a reduction of 52.5% compared to the control group. Regarding noise reduction performance, a foam content of 10% yields optimal results. The heat and noise insulation properties were both improved due to the enhanced porous structure of coral sand. However, excessive admixtures, such as 50 % content of coral sand, could weaken the strength by destroying the fine pore structure. Microscopic analysis further revealed that foaming agents could affect the hydration of cement with little impact on macro performance. Moreover, they also enhanced the toughness of bubbles and changed the surface structure of pore walls to ensure the integrity of the pore structure of FC.

Influence of sodium hydrogen carbonate, ammonium dihydrogen phosphate, and lignin-based explosion inhibitors on the sensitivity of coal dust explosion

In order to prevent coal dust explosions, this study developed a targeted environmentally friendly and efficient lignin-based explosion inhibitor. The effects of NaHCO3, NH4H2PO4, and lignin-based explosion inhibitors on the sensitivity parameters of coal dust explosions were investigated using a 20 L spherical vessel and a Hartmann tube for comparison. Furthermore, the explosion inhibition mechanisms of the three inhibitors were elucidated through SEM, conductivity, In Situ FTIR, TGA-DTG/DSC, and other testing methods. The results indicate that from the perspective of explosion sensitivity, ZA-L-NP exhibits better explosion inhibition effects than NaHCO3 and NH4H2PO4. The zeolite carrier of the composite explosion inhibitor has a fine porous structure, with some materials filling the pores of the zeolite, resulting in a rough surface of ZA-L-NP. The use of ZA-L-NP for explosion suppression has a minimal impact on the turbulent combustion rate of coal dust. Its poor conductivity provides an advantage in inhibiting coal dust explosions. All three inhibitors exhibit significant inhibitory effects on the OH functional groups in coal dust, with inhibition effects decreasing in the order of ZA-L-NP, NH4H2PO4, and NaHCO3. Using classical kinetic models, the activation energy (E) and pre-exponential factor (A) of coal dust with and without added explosion inhibitors were calculated. Analysis was conducted from the perspective of kinetic parameters such as mass residual, maximum burning rate, average burning rate, flammability discrimination index, and comprehensive combustion characteristic index. It was found that the zeolite and modified lignin (L-NP) in ZA-L-NP synergistically increased the activation energy of coal dust. The research results can provide theoretical basis for the effective prevention of coal dust explosions.

Basic magnesium carbonate template assisted co-carbonization of potassium citrate toward hierarchical porous carbon for supercapacitors

Hierarchical porous carbon (HPC) as the ideal host material for supercapacitors has received extensive attention. However, traditional methods of fabricating HPC often rely on organic macromolecules and complex procedures. Herein, a simple and straightforward approach is developed for the synthesis of HPC through basic magnesium carbonate template assisted co-carbonization of potassium citrate. Potassium citrate can be effectively embedded and encapsulated with basic magnesium carbonate due to the large bulk density difference between them. In the pyrolysis process, the carbon-containing small molecules produced by the pyrolysis of potassium citrate are deposited on the surface of MgO surface obtained from the decomposition of basic magnesium carbonate, and the etching reaction of potassium salt, CO2 and primary carbon structure occurs. The competitive rate of carbon deposition reaction and etching reaction can be easily controlled by changing the ratio of potassium citrate and basic magnesium carbonate. The obtained carbon materials show the morphology changes of nanoparticle accumulations, discontinuous carbon frames and carbon planar blocks, and the hierarchical porous structure of carbon materials can also be controlled in a wide range. HPC-2 exhibits the morphology of nanoparticle accumulation and generates abundant meso-macropores, which accelerates the rapid transport of electrolytic ions. The micropores inside the nanoparticles provide an accessible room for ionic adsorption. Benefited from this unique microstructural framework, HPC-2 shares a high capacitance of 305.5 F g−1 at 0.5 A g−1 and 173.1 F g−1 at 50 A g−1. Furthermore, the assembled symmetric supercapacitors exhibit a high energy density and power density than YP-50 F throughout the test range. The versatility of this synthetic strategy provides an insight into directional tailoring fine pore structure and micro-morphology of carbon materials based on small molecule deposition.

Microstructure, mechanical properties and interaction mechanism of seawater sea-sand engineered cementitious composite (SS-ECC) with Glass Fiber Reinforced Polymer (GFRP) bar

With increasing demand for sustainable and long-lasting materials, seawater sea-sand engineered cementitious composite (SS-ECC) has emerged as a promising alternative to conventional concrete in near-ocean construction projects. Glass fiber reinforced polymer (GFRP) bar with excellent corrosion resistance is an ideal choice for these applications. This study evaluated the bond performance of GFRP bars embedded in normal-strength ECC with polyvinyl alcohol (PVA) fibers and high-strength ECC with polyethylene (PE) fibers through pull-out tests. Additionally, tests were conducted on GFRP bars in pristine ECC made with freshwater and river sand for comparison. Further investigation explored the structural properties and uncovered load transfer mechanisms. Results indicated that saline content facilitated early cement hydration of normal-strength ECC, resulting in finer pore structure (10.5% lower porosity and 12.5% lower sorptivity), slightly enhanced compressive performance (1.2% higher compressive strength and 8.3% higher elastic modulus), denser microstructure at GFRP-ECC interface (13.7% lower porous transition zone thickness, 19.2% narrower transition zone and 19.7% higher Ca/Si ratio), and superior bond performance (28.3% higher bond strength and 22.6% higher fracture energy). Conversely, saline content imposed a limited impact on the mechanical properties of high-strength ECC, primarily attributed to the ultra-fine microstructure and early strength characteristics exhibited by the silica fume (SF)-based cementitious binder.

Dual‐Wing Ligand Constructed Metal–Organic Framework Membranes with Finely Tuned Apertures for Natural Gas Separation

AbstractMetal–organic framework (MOF) membranes with apparent molecular sieving effects have great potential for gas separation. However, their application in light‐gas separation (e.g., CO2/CH4 and H2/CH4) remains challenging due to their enlarged pore structures under transmembrane pressure. In this work, a series of MOF membranes constructed from dual‐wing (DW) ligands including 2‐chloromethylbenzimidazole, 2‐methylbenzimidazole, 2‐ethylbenzimidazole, and 2‐phenylbenzimidazole are reported, to finely tune apertures and enhance molecule sieving property for small‐size gases. These DW‐ligands provide steric resistance in two directions perpendicular to the coordination bond, leading to a much finer pore structure. The introduction of the DW‐ligands endows the DW/ZIF‐8 membranes with an adjustable bottleneck door for regulating gas diffusion, blocking the transport of large‐sized CH4 while allowing small‐sized H2 and CO2 to permeate. The membranes show significantly improved molecular sieving property with a CO2/CH4 mixed‐gas selectivity of 58.6 in the case of 2‐chloromethylbenzimidazole23/ZIF‐8, which represents the highest value among the reported ZIF membranes. This membrane also exhibits exceptional separation performance for H2/CH4 and H2/C3H8 with separation factors of 430 and 34341, which are the highest values among the reported MOF membranes. This study presents a facile and efficient strategy for regulating MOF aperture and constructing high‐performance membranes for natural gas separation.

High-efficient stabilization and solidification of municipal solid waste incineration fly ash by synergy of alkali treatment and supersulfated cement

Municipal solid waste incineration fly ash (IFA) designated as hazardous waste poses risks to environment and human health. This study introduces a novel approach for the stabilization and solidification (S/S) of IFA: a combined approach involving alkali treatment and immobilization in low-carbon supersulfated cement (SSC). The impact of varying temperatures of alkali solution on the chemical and mineralogical compositions, as well as the pozzolanic reactivity of IFA, and the removal efficiency of heavy metals and metallic aluminum (Al) were examined. The physical characteristics, hydration kinetics and effectiveness of SSC in immobilizing IFA were also analyzed. Results showed that alkali treatment at 25 °C effectively eliminated heavy metals like manganese (Mn), barium (Ba), nickel (Ni), and chromium (Cr) to safe levels and totally removed the metallic Al, while enhancing the pozzolanic reactivity of IFA. By incorporating the alkali-treated IFA and filtrate, the density, compressive strength and hydration reaction of SSC were improved, resulting in higher hydration degree, finer pore structure, and denser microstructure compared to untreated IFA. The rich presence of calcium-aluminosilicate-hydrate (C-(A)-S-H) and ettringite (AFt) in SSC facilitated the efficient stabilization and solidification of heavy metals, leading to a significant decrease in their leaching potential. The use of SSC for treating Ca(OH)2- and 25°C-treated IFA could achieve high strength and high-efficient immobilization.

Purifying surface water contaminated with azo dyes using nanofiltration: Interactions between dyes and dissolved organic matter

In this research, the interactions of two azo dyes, Methyl Orange (MO) and Eriochrome Black T (EBT), with dissolved organic matter (DOM) in surface water were studied, emphasizing their removal using nano-filtration membranes (NF-270 and NF-90). High-Performance Size Exclusion Chromatography (HPSEC) findings indicated that the dyes' molecular weight in deionized (DI) water ranged from 500 to 15k Dalton (Da), adjusting peak intensities with Jingmi River (JM) water Beijing. Notably, when dyes were diluted in JM water, ultraviolet (UV533 &466, and UV254), together with total organic carbon (TOC) parameters, revealed color removal rates of 99.49% (EBT), 94.2% (MO), 87.6% DOM removal, and 86% TOC removal for NF-90. The NF-90 membrane demonstrated a 75% flux decline for 50 mL permeate volume due to its finer pore structure and higher rejection effectiveness. In contrast, the NF-270 membrane showed a 60% decline in flux under the same conditions. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) analysis of dye-treated membranes in JM water revealed that the NF-270 showed a CC bond peak at 1660 cm−1 across various samples, while analyzing NF-90, the peaks at 1400 cm−1, 1040 cm−1, 750 cm−1, and 620 cm−1 disappeared for composite sample removal. The hydrophobicity of each membrane is measured by the contact angle (CA), which identified that initial CAs for NF-270 and NF-90 were 460 and 700, respectively, that were rapidly declined but stabilized after a few seconds of processing. Overall, this investigation shows that azo dyes interact with DOM in surface waters and enhance the removal efficiency of NF membranes.

Combined use of mullite and basalt fiber to inhibit the strength decline of oil well cement stone under alternating conditions of temperature rise and fall

During the development process of heavy oil with steam huff and puff, the wellbore undergoes alternating conditions of temperature rise and fall, leading to a significant decline in the strength of the cement sheath. This work studied the inhibition effect and mechanism of the composite material composed of mullite and basalt fiber on the strength decline of cement stone (the hardened body of cement slurry) under simulated wellbore temperature alternating conditions from 80 °C to 260 °C. The pore structure distribution of cement stone was investigated by mercury intrusion porosimetry (MIP), the microstructure and phase composition of cement stone was characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), together with quantitative X-ray diffraction (XRD) analysis. After 4 rounds of curing under alternating temperature conditions, the compressive strength of cement stone containing mullite and basalt fiber composite material was 28.6 MPa at 260 °C, which was only 9.2 % lower than that at 80 °C. However, the compressive strength of the blank cement stone without composite materials decreased to 22.5 MPa at 260 °C, which was 20 % lower than that at 80 °C. After 4 rounds of alternating temperature cured, the harmful pores of the cement stone without composite materials increase, and the xonotlite flakes and stacks together. The cement stone added with mullite has a finer pore structure after 4 rounds of alternating temperature cured because mullite reacts with portlandite to form C-A-S-H gel. The xonotlite remains fibrous, and a small amount of new phase hibschite is formed. Furthermore, basalt fiber can react with C-A-S-H gel at high temperatures, and the two phases are closely combined to further improve the high-temperature resistance of cement stone.