Scanning Electron Microscope-energy Dispersive Spectrometer Research Articles

Innovative dispersant for reducing heterogeneous coagulation of pentlandite and serpentine and new insight for their dispersion

Serpentine is easily muddy and has a high zero electric point of zero charge (PZC), which leads to heterogeneous coagulation with pentlandite, which seriously affects the flotation of pentlandite. To solve this problem, from the new perspective of reducing the heterogeneous coagulation of pentlandite-serpentine and dispersing them, this study explores the influence of sodium tungstate as dispersant on the dispersion between pentlandite and serpentine using flotation tests, zeta potential tests, scanning electron microscope-energy dispersive spectrometer (SEM-EDS) examination, molecular dynamics simulation (MS), and calculations of extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory. The results show that −20 μm fine serpentine seriously deteriorates the flotation of pentlandite, while adding sodium tungstate can significantly promote the flotation separation of pentlandite and serpentine. MS simulation results showed that sodium tungstate could be chemisorbed with iron ions on the surface of pentlandite and mainly physisorbed with serpentine. EDLVO theoretical calculations show that after adsorption of sodium tungstate, the interaction between the two changed from attraction to repulsion at pH less than 10, and the mutual attraction was weakened at pH more significant than 10, thus weakening the heterogeneous coagulation between pentlandite and serpentine and causing serpentine to desorb from the surface of pentlandite, thus restoring the floatability of pentlandite, which SEM-EDS also confirmed. This provides a new insight into the dispersion mechanism of sodium tungstate as the innovative dispersant which is different from other dispersants for reducing heterogeneous coagulation of pentlandite and serpentine.

Influence of microenvironment evolution induced by calcium leaching in concrete under pressurized water conditions on chloride transport

AbstractThe investigation into the influence of microenvironmental evolution, induced by calcium leaching on chloride transport in concrete in pressurized water environments, encompassed analysis of aspects such as the solid phase composition, microstructure characteristics, pH value distribution, free and total chloride concentrations using X‐ray diffraction (XRD), Thermogravimetric (TG), Mercury intrusion porosimetry (MIP), Scanning electron microscopy/Energy dispersive spectrometer (SEM/EDS), and titration tests. The results exhibit a weakening of the diffraction peaks of Ca(OH)2 (CH) in the XRD spectra over time under hydraulic pressure. Throughout the calcium leaching procedure, there was an increase in the proportion of pores with diameters exceeding 100 nm. The pH distribution notably followed a pattern where it initially increased, then decreased, ultimately stabilizing at a distinct level. As exposure progressed from the surface to the interior of the concrete, hydroxide ions accumulated predominantly at 10–20 mm. According to the calcium leaching characteristics under pressurized water conditions, concrete can be sectioned into four zones. Specifically, there is a decrease in calcium ions and pH value in concrete Zone 1 near the exposure surface, indicative of a corresponding decrease in the chloride binding capacity. Concrete Zone 2 shows enrichment of hydroxide ions enhances Friedel's salt stability, while leached calcium amplifies the chloride adsorption of ≡SiOH. These effects collectively trigger an increase in both pH and chloride binding capacity.

Study on the Mechanism and Control of Clogging Growth on the Submerged Entry Nozzle of Q355 Steel

To clarify the formation mechanism of clogging on submerged entry nozzle of Q355 steel, scanning electron microscope‐energy dispersive spectrometer (SEM‐EDS), cathodoluminescence and FactSage7.1 thermodynamic software are used to study the morphology and stratified structure of Q355 steel nozzle. The results show that, clogging on Q355 steel can be divided into decarburized layer, ≈1.5 mm, dense accumulation layer, about 2 mm, and loose accumulation layer, ≈1.5 mm. The phenomenon of CaO·2Al2O3, CaO, Ti2O3, Al2O3, and 2CaO·Ti2O3 inclusions precipitated from the molten steel and deposited in the inner wall of the nozzle during continuous casting is analyzed. The formation mechanism of the clogging is explained by drawing the clogging process diagram and thermodynamic calculation. The range of total Ca content in molten steel which should be controlled between 0.0012% and 0.0016% to reduce clogging at the nozzle is given.

Structural evolution of iron components and their action behavior on lignite combustion

Spontaneous combustion of lignite is closely related to the inherent minerals it contains, and the iron component has a remarkable influence on the combustion property of lignite. It is very important to study the influence of iron component on the combustion reaction property of lignite to reveal autoignition mechanism of lignite and reduce autoignition of lignite. In this research, FeCl3 and Fe2O3 were doped into demineralised lignite (SL+) by impregnation to research the effects of iron salts and iron oxides on the combustion properties of lignite. Based on the above, the effects of post-treatment method of the FeCl3-doped coal samples, iron-salt hydrolysis products and heat-treated temperatures on the combustion property of lignite were researched, and the microstructures of the coal samples were characterised and analysed using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results demonstrate that doping with FeCl3 increases the combustion performance of lignite, thereby reducing the ignition temperature of lignite by approximately 112 °C. In contrast, doping with Fe2O3 has a weaker combustion-promoting effect. XRD and XPS characterisation indicates that iron species in the coal samples doped with iron salts are highly dispersed and exhibit the FeOOH structure, whereas iron species in the coal samples doped with Fe2O3 exhibit the crystal form of α-Fe2O3. Doping of lignite with FeCl3 and its hydrolysis product β-FeOOH reduces the ignition temperature of the coal samples. Iron species in the FeCl3-doped coal samples after heat treatment at 300 °C-500 °C increase the combustion property of the coal samples, whereas iron species after heat treatment at 600 °C-900 °C have a much weaker or non-existent promoting effect on the combustion performance of the coal samples. The characterisation show a change in iron species in the coal samples with the rise in the heat treatment temperature. This change progresses from highly dispersed β-FeOOH below 300 °C to Fe3O4 above 400 °C. Fe3O4 is gradually reduced, with part of it further reduced to elementary iron at the same time as grain growth. It is believed that the gradual agglomeration of Fe3O4 and the appearance of elementary iron are the main reasons for the weakening or disappearance of the promoting effect on coal combustion.

Study on the difference of composition between traditional and modern lime used in the restoration of Qufu San Kong Ancient Architectural

In recent years, a decline in the binding strength and frost resistance of lime binder used in the restoration of the Qufu San Kong ancient architectural complex in Shandong Province has been observed, which has significantly affected the quality of restoration. In this study, lime binder samples were collected from the Kuiwen Pavilion roof, limestone samples in the vicinity of the Confucius Temple, and modern industrial quicklime from various provinces in China. Analytical methods including X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy were employed. Results indicate that the local limestone in Qufu contains impurities such as Si or Mg. XRD patterns reveal that the main phase of the Kuiwen Pavilion roof lime binder samples is calcite. Using FTIR and Scanning Electron Microscope- Energy Dispersive Spectrometer (SEM-EDS), the presence of hydrated calcium silicate (C-S-H) gel is identified in the samples. This suggests that the traditional quicklime-production process in Qufu yields a multiphase composite system. Modern industrial quicklime, aged for two months, showed no presence of C-S-H gel in the FTIR spectra and SEM-EDS results, indicating that it is a comparatively pure system primarily comprising CaO. The study suggests that traditional quicklime-production processes typically involve burning limestone with higher Si content, leading to the generation of a significant amount of dicalcium silicate. Additionally, the use of high-ash coal as fuel introduces reactive silicon dioxide into the quicklime product. These factors contribute to the formation of C-S-H gel in hydrated lime. The presence of C-S-H gel enhances lime binder properties such as binding strength and frost resistance. Modern quicklime production, which selects limestone with lower Si content and employs low-ash coal as fuel, aims to minimize or avoid the formation of C-S-H gel in hydrated lime. High-purity CaO quicklime products align with the principles of modern fine processing; however, they compromise the binding strength and durability of lime binder required for traditional architectural restoration.

Flotation separation of molybdenite from talc using carrageenan as depressant

Due to the strong natural floatability of molybdenite and talc, conventional flotation depressants are difficult to separate these two minerals. As a common depressant, starch has a strong inhibitory effect on both minerals (Castro et al., 2016), while sodium carboxymethyl cellulose has a weak inhibitory effect on both minerals (Chen et al., 2024). Therefore, selecting a proper depressant is the key for achieving the efficient flotation separation. This study investigated the flotation separation of talc and molybdenite using carrageenan as the depressant and sodium butyl xanthate (SBX) as the collector. The micro-flotation test results showed that carrageenan exhibited a strong depressing effect on both talc and molybdenite, and even stronger on molybdenite. However, molybdenite could achieve flotation after adding SBX, while talc was still suppressed. In addition, it was observed that the recovery of molybdenite by adding SBX first was higher than that of adding carrageenan first. A concentrate with a molybdenum grade of 50.64% and recovery of 87.1% was obtained in the artificial ore flotation with the initial grade of 28.52%. The adsorption mechanism of carrageenan on the surfaces of molybdenite and talc was studied using contact angle testing, adsorption capacity testing, zeta potential measurement, Scanning Electron Microscopy-Energy Dispersive Spectrometer (SEM-EDS) analysis, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) analysis. It was concluded that carrageenan physically adsorbs on both mineral surfaces, whereas SBX adsorbs selectively on the surface of molybdenite and competes with carrageenan for adsorption.

Investigation of the Electrochemical Methylene Orange Effluent Degradation Using Graphite Battery Waste and Seawater

Electrochemical degradation using seawater and graphite electrodes from waste batteries for methylene orange (MO) dye degradation has been successfully carried out. Electrode characterization, electrolyte calibration, and dye degradation effectiveness with various voltages, pH, kinetics, and degradation reaction mechanisms were observed. Characterization showed a characteristic 2θ peak by X-ray diffractometer (XRD) at 26.5 °, and scanning electron microscopy-energy dispersive X-ray spectrometer (SEM-EDX) showed the morphology of hollow grains with carbon (C) and oxygen (O) composition. In addition, scanning potentiometry showed the initiation of hypochlorite compound formation and MO degradation. Further study of degradation effectiveness showed optimal results at 3 volts and above voltages. Hypochlorous acid (HOCl) and hypochlorite ions (OCl-) from seawater are very effective oxidizing agents in acidic conditions compared to other pH conditions. Pseudo-first-order kinetics regulate the electron attack from the hypochlorite oxidizer (OCl-), the hydroxyl groups (•OH) from the seawater electrolysis mechanism with graphite electrode media on the reactive groups, the ring binding on MO, and the degradation. This indicates that the graphite electrode system used to reuse waste batteries and seawater has the potential to degrade waste dyes in aquatic environments. HIGHLIGHTS Electrochemical system with graphite electrode battery waste and seawater electrolyte. Characterization with XRD, SEM-EDX, spectrometry, and potentiometry. Analysis of the effect of voltage and pH treatment variation. Kinetic and degradation mechanism of methylene orange. GRAPHICAL ABSTRACT

Mechanical properties and engineering applications of low-dosage cement/lime-stabilized loess improved with nano-MgO and nan-SiO2

Loess has poor engineering performance and needs to be improved for engineering applications by adding a large amount of lime or cement, which is not consistent with the goal of “carbon peaking and carbon neutrality”. In this study, nano-SiO2 (NS) and nano-MgO (NM) were applied to improve the engineering performance of low-dosage lime/cement- stabilized loess. The improvement mechanisms of each binder on loess were analyzed by X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) tests. The impact of binder dosage and curing time (T) on unconfined compressive strength (UCS), resilient moduli (MR), California bearing ratio (CBR), internal friction angle (φ), cohesion (c), and compression coefficient (a1-2) of each stabilized loess were also explored by conducting a range of laboratory experiments. The results show that the addition of NS did not result in the formation of new substances. However, theformation of MH was noted with the addition of NM. The combination of lime and NS can significantly enhance the UCS, CBR, MR, and c of the stabilized loess, followed by the combination of cement and NS. With the increasing NM content, the above mechanical indices first increased and then decreased for the stabilized loess. Both the binder content and type caused a lesser impact on the φ and a1-2 than on other mechanical indices. Moreover, the mix ratio and feasibility of each stabilized loess applied in various engineering fields were analyzed based on relevant standards and the construction requirements of lime and cement. Finally, estimation models were established for the above mechanical indices of lime-NS stabilized loess, which can provide a reference for engineering design and quality control.

Effect of Rare Earth Ce on Structure and Properties in 7CrSiMnMoV Die Steel Castings

In this study, rare earth (RE) Ce is used to modify the interaction between atoms in 7CrSiMnMoV die steel castings. The tensile properties are performed, and strengthening mechanism are analyzed by investigated fracture surface, and microstructure by optical microscopy (OM) and scanning electron microscope‐energy dispersive spectrometer (SEM‐EDS). And ab initio molecular dynamics (AIMD) is used to simulate the effect of the Ce element on the local atomic structure of the FeCeC system alloy steel. The results indicate the strength can increase from 722.55 to 1074.27 MPa, and the elongation can increase from 24.86% to 44.22% with a RE Ce concentration of 0.009%. It is attributed to that doping of Ce can inhibit the formation of network eutectic cementite, refine the lamellar spacing of pearlite, and even form granular cementite and martensite structures. AIMD simulation results show that C atoms tend to be surrounded by Fe, and the strong chemical bonds of FeC make the Fe‐centered C more stable with an increase in RE Ce concentration. And doping Ce can introduce new local topological and chemical orderings such that the FeCFe triplets predominantly form small and big angles shifting from near 75° and 136° to 47° and 81°, respectively.

Study on the influence parameters and anti‐abrasion performance of steam‐cured hydraulic concrete for prefabricated water conveyance channel

AbstractExcessive sediment concentration in water can cause damage to prefabricated concrete channels. This study evaluates the impact of sediment‐laden water flow on the mass loss of concrete after abrasion, incorporating scanning electron microscope‐energy dispersive spectrometer (SEM‐EDS) and X‐ray diffraction (XRD) analyses to assess the effects of four steam‐curing parameters—delay time, heating rate, constant temperature duration, and steam curing temperature—on the abrasion resistance of concrete used in enterprise prefabricated water conveyance channels. The results indicate that the abrasion resistance of concrete for prefabricated channels improves gradually with increases in delay time and constant temperature duration. When the delay time exceeds 3 h and the constant temperature time exceeds 4 h, the concrete's abrasion resistance can reach more than 5 h(g/cm2)−1. Rapid heating rates and excessively high steam curing temperatures adversely affect the concrete's abrasion resistance. However, when the heating rate is controlled within 20°C/h and the steam curing temperature does not exceed 70°C, the concrete's abrasion resistance can achieve more than 5 h(g/cm2)−1. In compliance with the standard DL/T5201‐2021 requirements, it is recommended that concrete with high demands for abrasion resistance should preferentially select steam‐curing parameters within these ranges.

Study on the adsorption process and kinetic, thermodynamic of bio-based waste cattle hair powder toward acidic complex dye.

In this paper, cattle hair waste (CHW) was collected and physically milled into different meshes of ultrafine cattle hair powder (UCHP). The reuse of CHW reaches the purpose of treating pollution with waste by using bio-base adsorbent. It was characterized by using scanning electron microscope-energy dispersive spectrometer (SEM-EDS), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), and X-ray diffraction (XRD). The adsorption studies were carried out under different conditions of temperature, time, pH, concentration of dye solution, mesh size, and dosage of cattle hair powder, respectively. The pseudo-first and pseudo-secondary kinetics and intra-particle diffusion models were employed to analyze the adsorption kinetic. The Langmuir, Freundlich, and Temkin adsorption isotherm was used to analyze the adsorption isotherm. The results showed that the adsorption capacity of UCHP for acidic metal complex (Trupoxane Brown R6) dyes increased with the decreasing pH solution. The adsorption capacity of 200 mesh UCHP was 379.5mg.g-1 when the adsorption conditions were as follows: 100mL dye solution with the initial concentration of 1000mg·L-1, the dosage of adsorbent was 0.1g, the pH was 3 for 12h at 40°C. The kinetic model fitting results showed that the adsorption of dyes by UCHP conformed to the pseudo-second-order kinetic model. Adsorption thermodynamics study showed that the Langmuir model has the highest fitting result. The amino group contained on the surface of cattle hair powder and the amide bond contained in the molecular chain of peptide chain have better electrostatic adsorption binding force for acid metal complex dyes, and the binding between them is mainly electrostatic attraction. The experimental results show that the ultrafine powder has better adsorption property, which provides a high-value conversion way for recycling waste cattle hair.

Efficient elimination of 3-monochloropropane-1,2-diol fatty acid ester from palm oil via using activated carbon grafted with Tween80.

In the current study, we attempt to remove 3-monochloropropane-1,2-diol fatty acid ester (3-MCPD ester) from palm oil with developed composite adsorbent (Tween80 modified activated carbon [AC]), and scanning electron microscopy-energy dispersive spectrometer, Fourier transform-infrared spectroscopy, X-ray diffraction, nitrogen content adsorption-desorption and thermogravimetric analysis were used to characterize the modifications. We further examined the adsorption capability of the composite adsorbent for 3-MCPD ester and found that the highest removal efficiency was 87.36% (5.3% of adsorbent dose at 104°C for 29min). This is approximately three times higher than that of pristine AC, implying that the composite can be employed as a novel adsorbent for 3-MCPD ester reduction. Along with the adsorption mechanism of Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin models were also tested. It has been suggested that Freundlich model could best describe the adsorption process. Adsorption was found to be well-fitted by pseudo-second-order kinetics according to the kinetic study. An endothermic and spontaneous adsorption mechanism was demonstrated by the thermodynamic studies.

Evaluation of calcium carbonate production and cementitious characteristics of enzymatically induced carbonate precipitation during environmental adjustment

Enzymatically induced carbonate precipitation (EICP) is an emerging and eco-friendly technology, which is considered a green alternative to traditional cement in soil stabilization. When stabilizing soil use one-phase grouting method, the activity of urease is often adjusted, leads to changes in the composition and cementitious characteristics of CaCO3. Previous studies primarily focused on the mechanical properties of solidified soil samples, while the production and cementitious characteristics of CaCO3 influenced by the control of urease activity is rarely discussed. This study investigated production and cementitious characteristics of CaCO3 under different reaction environment (pH adjustment, temperature adjustment, and addition of inhibitors), during which the urease activity tests, pH tests, CaCO3 production tests and ultrasonic oscillation tests are conducted. Meanwhile, the morphological characteristics and mineral composition of CaCO3 are revealed through Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS) tests and X-ray Diffraction (XRD) test. The results demonstrate that all three one-phase grouting methods can delay the production of CaCO3 at early-stage of EICP, while the pH should be maintained above 4 to prevent significant urease deactivation. The CaCO3 generated in EICP mainly consists of calcite and vaterite, and the size of CaCO3 increases with the urease activity increased. The cementitious characteristics of CaCO3 is mainly determined by the percentage composition of calcite and vaterite, where higher vaterite content results in weaker cementitious characteristics. This study provides insights for evaluating the cementitious characteristics of CaCO3, which is beneficial for guiding the promotion and application of one-phase grouting method.

Study on Thermal Cycling Reliability of Epoxy-Enhanced SAC305 Solder Joint.

In this work, epoxy was added into commercial Sn-3.0Ag-0.5Cu (SAC305) solder paste to enhance the thermal cycling reliability of the joint. The microstructure and fracture surface were observed using a scanning electron microscope/energy dispersive spectrometer (SEM/EDS), and a shear test was performed on the thermally cycled joint samples. The results indicated that during the thermal cycling test, the epoxy protective layer on the surface of the epoxy-enhanced SAC305 solder joint could significantly alleviate the thermal stress caused by coefficients of thermal expansion (CTE) mismatch, resulting in fewer structural defects. The interfacial compound of the original SAC305 solder joints gradually coarsened due to the accelerated atomic diffusion, but epoxy-enhanced SAC305 solder joints demonstrated a thinner interfacial layer and a smaller IMC grain size. Due to the reduced stress concentration and the additional mechanical support provided by the cured epoxy layer, epoxy-enhanced SAC305 solder joints displayed superior shear performance compared to the original joint during the thermal cycling test. After 1000 thermal cycles, Cu-Sn IMC regions were observed on the fracture surfaces of the original SAC305 solder joint, exhibiting brittle fracture characteristics. However, the fracture of the SAC305 solder joint with 8 wt.% epoxy remained within the solder bulk and exhibited a ductile fracture mode. This work indicates that epoxy-enhanced SAC305 solder pastes display high thermal cycling reliability and could meet the design needs of advanced packaging technology for high-performance electronic packaging materials.

In Situ Analysis of Binder Degradation during Catalyst-Accelerated Stress Test of Polymer Electrolyte Membrane Fuel Cells.

High-oxygen-permeability ionomers (HOPIs) are being actively developed to enhance the performance and durability of high-power polymer electrolyte membrane fuel cells (PEMFCs). While methods for evaluating binder performance are well-established, techniques for assessing binder durability and measuring its degradation in situ during the AST process remain limited. This study examines the distribution of relaxation times (DRT) and Warburg-like response (WLR) methods as in situ analysis techniques during the catalyst-accelerated stress test (AST) process. We conducted catalyst-ASTs (0.6-0.95 V cycling) for 20,000 cycles, monitoring changes using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). Contrary to expectations, during the catalyst-AST, the ion transport resistance of the binder decreased, indicating no binder degradation. Scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) analysis revealed that the degradation rate of the catalyst and the support was relatively higher than that of the binder, leading to a reduction in catalyst layer thickness and improved binder network formation. By applying the DRT method during the catalyst-AST process, we were able to measure the increase in oxygen reduction reaction (ORR) resistance and the decrease in proton transport resistance in situ. This allowed for the real-time detection of the reduction in catalyst layer thickness and improvements in ionomer networks due to catalyst and support degradation. These findings provide new insights into the complex interplay between catalyst degradation and binder performance, contributing to the development of more durable PEMFC components.

Graphene nanoplatelet reinforced Al-based composites prepared from recycled powders via mechanical alloying and pressureless sintering

This study reports on the powder metallurgy preparation and characterization of aluminum-graphene nanoplatelet (Al-GNP) composites synthesized using recycled Al powders. Recycled Al and GNP powders (0.1–1 wt%) were mechanically alloyed (MA'd) for 4 h, followed by cold pressing (at 450 MPa) and pressureless sintering at 590 °C for 2 h. Starting powders were analyzed using an optical emission spectrometer (OES) and a Raman spectrometer. Also, MA'd powders and sintered samples were characterized using an X-ray diffractometer (XRD), a scanning electron microscope/energy dispersive spectrometer (SEM/EDS), and a differential scanning calorimeter (DSC). Particle size analyses, pycnometer, and Archimedes' densities, Vickers microhardness, dry-sliding wear, and compression tests were also conducted. The Al4C3 formation was observed in the XRD patterns of sintered compositions. The highest and lowest relative densities were measured for the 1 wt% and 0.1 wt% GNP reinforced samples as 97 % and 92 %, respectively. The highest hardness value was obtained as approximately 1.31 GPa for 1 wt% GNP reinforced. With the addition of reinforcement GNP, the wear rate developed to approximately 0.00225 mm3/Nm. The compressive strength increased from nearly 70 MPa to 162 MPa.

Lanthanum ferrite modified filling materials and its enhancement for phosphorus and COD removal: Performance and mechanism

Previous studies have developed numerous adsorption composite materials demonstrating substantial removal efficiencies for phosphorus (P) and chemical oxygen demand (COD). However, most of materials targeted single contaminant and were inconvenient to apply in real water bodies owing to size limitation. In the current study, three composite materials‑lanthanum ferrite-modified Quartz balls/Maifan stones/Honeycomb ceramics-were synthesized using one step co-precipitation method. Structural and morphological changes of pre- and post-adsorption were examined through Scanning Electron Microscope - Energy Dispersive Spectrometer (SEM-EDS) and X-ray diffraction (XRD). Kinetics, thermodynamics, and isotherm models were simulated for the analysis of P and COD adsorption. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) were employed to elucidate the adsorption mechanisms. The results demonstrated that these materials achieved P maximal removal rate of 99.56 % and COD maximal removal rate up to 94.82 %. The second-order kinetic model for P adsorption was more excellent than that of the first-order model, and the intra-particle diffusion model more accurately described the COD adsorption. Both the Langmuir and Freundlich were used to fit the adsorption isotherm data for P and COD. XPS and FTIR revealed that the adsorption mechanisms for P were ligand exchange and chemical precipitation. Whereas the adsorption mechanisms for COD were ligand exchange and physical adsorption. The materials in the actual farmland drainage performed excellent and effectively reduced the concentration of P and COD up to 68.58 % and 53.98 %, respectively. The lanthanum ferrite-modified fillers provide accessible, universal and bifunctional option for controlling agricultural non-point source pollution.

Microscopic Mechanism and Road Performance Analysis of MgO Carbonation–Solidification of Dredged Sediment

MgO carbonization is a green and low-carbon soil improvement technology. The use of MgO carbonization to solidify dredged sediment and transform it into road-building materials has significant environmental sustainability advantages. A series of microscopic characterization tests, including X-ray Diffraction (XRD), Scanning Electron Microscope–Energy Dispersive Spectrometer (SEM-EDS), and Mercury-in-Pressure (MIP) tests, were conducted to elucidate the evolution characteristics of mineral composition, microscopic morphology, and pore structure of sediment under carbonation. Based on the results, the mechanism of MgO carbonation–solidification of dredged sediment was explored. In order to verify the improvement of carbonation on the road performance of sediment, comparative tests were carried out on sediment, non-carbonated sediment, and carbonated sediment. The results indicate a significant improvement in the solidification of MgO-treated sediment through carbonation, with enhanced macroscopic strength and densified microscopic structure. This can be attributed to the encapsulation, cementation, and pore-filling effects of the hydration products and carbonation products of MgO on soil particles. The rebound modulus and splitting strength of carbonated sediment were 3.53 times and 2.16 times that of non-carbonated sediment, respectively. Additionally, the carbonated sediment showed improved saturated stability, resistance to salt solution wet–dry cycles, and resistance to freeze–thaw cycles.

Preparation and evaluation of GCD-1 lunar regolith simulant based geopolymer activated by solid sodium silicate

In this study, a new lunar regolith simulant, named "GCD-1", was formulated by combining various minerals, such as anorthite, albite, pyroxene, ilmenite, slag, and fly ash. Through X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD) analysis, it was verified that the main mineral composition of GCD-1 was basically the same as that of the lunar soil at the Apollo 14 landing site, in which the deviation in the main compound (i.e., SiO2 and Al2O3) was within 0.5%. Furthermore, GCD-1 based geopolymer was prepared by the one-part method, which was a mixture of solid GCD-1 precursor, solid sodium silicate (SS) activator, and water. The average daytime temperature at the lunar equator, which was calculated to be 60°C, was set as the curing temperature for the GCD-1 based geopolymer. The strength development of the GCD-1 based geopolymer was then characterized by unconfined compressive strength (UCS) for 3, 7, and 12 curing days to consider the effectiveness of the factors (solid SS to lunar regolith simulant [S/L] and water to binder ratio [W/B]). The micro-analysis tests including scanning electron microscope-energy dispersive spectrometer (SEM-EDS), mercury intrusion porosimetry (MIP), and brunner-emmet-teller (BET), were further conducted to investigate the microstructural development of the GCD-1 based geopolymer. Results showed that the increase of the W/B ratio in the GCD-1 based geopolymer tended to increase the total porosity of the sample, thereby inducing a lower UCS. At the same time, for a fixed W/B ratio, the higher S/L ratio had a certain inhibition effect on the hydration reaction, which caused the reduction in the UCS of the sample. The highest UCS of the GCD-1 based geopolymer reaching 30.54 MPa, was achieved under the simulated lunar equatorial daytime temperature for 12 days with W/B and S/L ratios set at 0.25 and 0.18, respectively. Microstructure and mineralogy analyses indicated that the hydrated sodium aluminosilicate (N-A-S-H) gels contributed to reducing the sample's porosity, thereby enhancing the UCS. The relationship between the UCS and total porosity of GCD-1 based geopolymer was then derived. The results of the current study are crucial for lunar base construction with in-situ resources.

Hydration, strength, and microstructure evolution of Portland cement-calcium sulphoaluminate cement-CSH seeds ultra-early strength cementitious system

Improving the very early age strength of precast concrete components at ambient temperature and ensuring the development of later strength is of significant engineering importance. This objective was successfully achieved by incorporating a specific percentage of 0–3% CSH seeds (CSHs) and 5%-20% calcium sulphoaluminate cement (CSA) into Portland cement (PC). The hydration, strength and microstructure evolution of Portland cement-calcium sulphoaluminate cement-CSH seeds cementitious system were investigated. Hydration heat tests reveal that CSHs effectively accelerated the early hydration of the slurry within the first 12 h without affecting its later hydration. CSHs and CSA acted synergistically to enhance hydration kinetics. However, it is crucial to control the proportion of CSA within the range of 5%-10%; exceeding this ratio can severely inhibit the hydration of silicates. Strength tests indicate that the addition of CSHs and CSA can increase the compressive and flexural strengths of mortar within the first 12 h by 282% and 208%, respectively, without impacting the development of its later-age strength. Together, they synergistically provide favorable support for the strength and toughness of matrix. Based on linear regression analysis and nitrogen adsorption and desorption tests, it was concluded that CSHs enhance the hydration dependence of matrix strength, while CSA diminishes this characteristic. This is because CSHs refine the pore size distribution of the paste, increasing the proportion of micropores, whereas CSA promotes the formation of more mesopores and macropores, leading to coarser pores; however, 5% CSA is beneficial for further refining the pore structure. The microcosmic phase evolution of the early-strength cementitious system was analyzed through X-ray diffraction and scanning electron microscope-energy dispersive spectrometer experiments. Results demonstrate that low proportions of CSA and CSHs promote the co-growth of ettringite and C-S-H gel, ensuring a more rapid formation of a dense hydration network in the early stages, thereby accelerating strength development. These findings provide a reference for the design and preparation of precast concrete.