Scanning Electron Microscope-energy Dispersive Spectrometer Research Articles

Dissolution behavior of chromite mineral impurities in raw materials of glass production using scanning electron microscopy-energy dispersive spectrometer, X-ray fluorescence spectroscopy and Raman spectroscopy methods

Silica sand is an essential raw material for glass production. The specification of silica sand for each type of glass is the most important point, such as chemical purity, grain size, grain shape, and their impurities. Some of the impurities in the sand can be eliminated by processing yet some cannot be avoided. This paper indicates that as an impurity in the sand, chromite minerals dissolve in glass. 0.200 mm and 0.250 mm grain size chromite minerals were observed grain size change at 1350 °C − 1400 °C − 1450 °C. With increasing in temperature, the rate of size change in the grain diameter increased. Because of the chemical composition of chromite mineral, with increasing temperature, first of all, aluminum and magnesium content start to dissolve in soda lime silicate glass. Then, chromium content transforms into chromium oxide. The transformation rate depends on the mineral composition as well as the temperature and the residence time in the furnace. This paper concerns the chemical composition of the chromite by scanning electron microscopy equipped with energy dispersive spectrometer, the compositions of the raw material analyzed with X-ray fluorescence spectroscopy, inductively coupled plasma optical emission spectrometer and chromite characteristics analyzed by Raman Spectroscopy methods.

Activation of periodate by biocarbon-supported multiple modified nanoscale iron for the degradation of bisphenol A in high-temperature aqueous solution.

As reported, the persistent toxic and harmful pollutant bisphenol A (BPA) from industrial emissions has been consistently found in aquatic environments inhabited by humans. Periodate (PI)-based advanced oxidation processes (AOPs) have been employed to degrade BPA, although activating PI proves more challenging compared to other oxidants. A novel nano iron metal catalyst, sulfided nanoscale iron-nickel bimetallic nanoparticle supported on biocarbon (S-(nFe0-Ni)/BC) was synthesized and utilized to activate PI for the removal of BPA. The morphology, structure, and composition of S-(nFe0-Ni)/BC were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), and fourier-transform infrared spectrum (FTIR). The catalyst demonstrates an excellent ability to activate PI, achieving a BPA removal efficacy of 86.4%, accompanied by a 33% reduction in total organic carbon (TOC) in the {S-(nFe0-Ni)/BC}/PI system. BPA degradation exhibited a significant change at the 5-min mark. In the first stage (0-5min), nonlinear dynamic fitting research, combined with scavenging experiments, unveiled the competitive degradation of pollutants primarily driven by iodate radical ( ), singlet oxygen , and hydroxyl radical ( ). The competitive dynamics aligned with the ExpAssoc model. The contribution rates of different active species during the second stage (5-120min) were calculated. The contributions of main species to BPA removal follow the order of > > throughout the entire process. The influence of various parameters, such as the dosage of S-(nFe0-Ni)/BC, initial PI concentration, BPA concentration, pH, temperature, and the presence of coexisting anions, was also examined. Finally, a plausible reaction mechanism in the system is proposed, suggesting that the {S-(nFe0-Ni)/BC}/PI system involves a heterogeneous synergistic reaction occurring primarily on the surface of S-(nFe0-Ni)/BC. Therefore, this study proposes a promising approach for PI-based AOPs to degrade organic pollutants, aiming to mitigate the irreversible harm caused by such pollutants to organisms and the environment.

Study on the Degradation Effect of Carbonaceous Shale under the Coupling Effect of Chemical Erosion and High Temperature.

The southwest region of China has abundant groundwater and high-temperature geothermal energy. Carbonaceous shale, as one of the typical surrounding rocks in this region, often suffers from deterioration effects due to the coupled action of groundwater chemical erosion and high temperature, which affects the long-term stability of tunnel engineering. In order to investigate the deterioration effects of carbonaceous shale under the coupled action of chemical erosion and high temperature, carbonaceous shale from a tunnel of Lixiang Railway in Yunnan Province was taken as the research object. The microstructure and mineral composition of the samples before and after chemical erosion were obtained with a scanning electron microscope-energy dispersive spectrometer and an X-ray diffraction test. Then, triaxial compression tests were conducted on the samples under different time points and different temperature effects of chemical erosion, and the stress-strain curves and the deterioration laws under a single factor were obtained. An improved numerical simulation method based on the parallel bond model was developed, which can account for the coupled effects of chemical erosion and high temperature on the rock. By simulating the triaxial compression test of carbonaceous shale, the deterioration law of carbonaceous shale under the coupled action was discussed. The results show that chemical erosion has a significant deterioration effect on the triaxial compressive strength of carbonaceous shale, and the degree of deterioration is related to the erosion time. In the first 30 days of erosion, the triaxial compressive strength of carbonaceous shale decreased by 11.38%, which was the largest deterioration range. With the increase in erosion time, the deterioration rate gradually decreased; temperature had a significant threshold effect on the strength of carbonaceous shale, and a clear turning point appeared at about 200 °C. By simulating the deterioration effects of carbonaceous shale under the coupled action of chemical erosion and high temperature, it was found that the longer the duration of chemical erosion, the stronger the temperature sensitivity of carbonaceous shale, and the more serious the loss of compressive strength during the heating process. When the temperature was low, the strength of carbonaceous shale changed little, and some samples even showed an increase in strength; when the temperature was high, the strength of carbonaceous shale decreased significantly, showing deterioration characteristics. The numerical simulation method was compared and verified with the indoor test results, and it was found that the numerical calculation had a good agreement with the test results.

Efficient reduction of hexavalent chromium by Fe-Mn bimetallic nanoparticles: Performance and role of manganese

Modification of zero-valent iron by manganese doping is a potential way to improve the properties of zero-valent iron, but the role of manganese in Fe/Mn bimetallic nanoparticles during the reduction process of hexavalent chromium is not yet fully recognised. Nano-Fe/Mn bimetals (NFMB) was synthesized through one-step chemical reduction method and characterized by Transmission Electron Microscope (TEM), Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS) and X-ray Photoelectron Spectroscopy (XPS). The results showed that dispersed particles owned a rough surface and six functional groups, namely, C-O, C=O, O-H, and -COOH, Fe-O, Mn-O. XPS analysis results showed that four elements in NFMB: Fe, Mn, C, and O, along with Fe0, Mn0, Fe2O3, and FeOOH were confirmed. The composition analysis indicated an approximate content of Fe (16.74 %) and Mn (12.59 %), with the detection of Cr (1.51 %) after the reaction. The batch experiments revealed a significant enhancement of reduction efficiency of Cr (VI) at a lower pH level and higher temperature, with a consistent removal rate of around 99.9 % within the pH range of 3-9, showcasing the adaptability of NFMB across a wide pH range. The maximum removal capacity of Cr (VI) by NFMB was determined to be 35.54 mg·g−1. The removal process involved the adsorption of Cr (VI) to the surface of NFMB, followed by a series of chemical reduction and precipitation processes, and the final removal from the aqueous solution. Therefore, the Fe/Mn bimetallic nanocomposites was proved to be promising for the removal of Cr (VI) from aqueous environments.

Fabrication of a novel MoB/BiOCl photocatalyst for losartan and Escherichia coli removal

In this work, various MoB/BiOCl (0.5–2.0% wt. MoB) photocatalysts were fabricated, characterized using X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) and chronoamperometry, and their photocatalytic activity was assessed for the degradation of the persistent contaminant losartan (LOS) in aqueous solutions under simulated solar irradiation. The 0.5MoB/BiOCl catalyst exhibited the highest efficiency, achieving complete degradation of 500 μg/L LOS in less than 10 min. Interestingly, the 0.5MoB/BiOCl sample also showed remarkable efficiency under visible irradiation (>420 nm), achieving 80% removal in 30 min. The decomposition kinetics followed pseudo-first-order, while the efficiency significantly decreased under alkaline conditions. According to the scavenging experiments, both h+, O2•− and 1O2 participate in the decomposition of LOS, while the role of •OH is minor. A slight increase in degradation was observed in the presence of NaCl, and a small retardation occurred in the presence of humic acid. On the contrary, the presence of bicarbonates significantly delayed the reaction. Although significant inhibition was observed for secondary effluent, the system was capable of completely degrading LOS in less than 15 min when pH was adjusted to 3.8. The process demonstrated promising results for the simultaneous removal of E. coli and micropollutants, achieving complete LOS removal in 15 min and 99.999% inactivation of E. coli after 180 min.

The Transfer and Change of Paints in a Hit-and-run Motor Vehicle Accident

Abstract This work investigated transfer and change of paint evidences in a case of hit-and-run. Two kinds of attachments were found on the clothes of the victim and they were initially considered paint fragments from the vehicle causing the accident. Infrared spectroscopy (IR), scanning electron microscope–energy dispersive spectrometer, and Microspectrophotometry were applied for examination of paints and clothing fibers. Polyester was detected in one of the attachments and in the clothing fibers of the victim by IR. A traffic accident simulation experiment was designed and conducted to research whether the polyester attachments come from suspected vehicle paints or victim’s clothing fibers. The results showed that a melt mixture of transferred paints and clothing fiber was formed after a violent collision. Because the amount of transferred paints was too low to be detectable in the mixture, the components detected by IR were mainly from clothing fibers. Thereby, we inferred that only one kind of attachment and paint fragments existed on the clothes of the victim, and the polyester attachments cannot be used to indicate the composition of suspected vehicle paint. Clothing fibers and paints are both common trace evidence in traffic accident cases, and more attention should be paid to the examination of transferred paints on clothing fibers.

A rapid one-step synthesis of silver and copper coordinated chlorine functionalized fullerene nanoparticles with enhanced antibacterial activity.

Nanoparticle modification demonstrates a remarkable synergetic effect in combating bacteria, particularly resistant bacteria, enhancing their efficacy by simultaneously targeting multiple cellular pathways. This approach positions them as a potent solution against the growing challenge of antimicrobial-resistant (AMR) strains. This research presents an investigation into the synthesis, characterization, and antibacterial evaluation of silver-coordinated chloro-fullerenes nanoparticles (Ag-C60-Cl) and copper-coordinated chloro-fullerenes nanoparticles (Cu-C60-Cl). Utilizing an innovative, rapid one-step synthesis approach, the nanoparticles were rigorously characterized using X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometer (SEM-EDS), High-Resolution Transmission Electron Microscopy (HR-TEM), Fourier-Transform Infrared Spectroscopy (FTIR), and Raman spectroscopy. In conjunction with the analytical techniques, a computational approach was utilized to corroborate the findings from Raman spectroscopy as well as the surface potential of these nanoparticles. Moreover, the antibacterial activities of the synthesized nanoparticles were assessed against Escherichia coli (E. coli) and Methicillin-Resistant Staphylococcus aureus (MRSA). These findings demonstrated that the synthesized Ag-C60-Cl and Cu-C60-Cl nanoparticles exhibited minimum inhibitory concentrations (MIC) of 3.9 μg mL-1 and 125 μg mL-1, respectively. Reactive oxygen species (ROS) quantification, catalase assay, and efflux pump inhibition results revealed promising broad-spectrum antibacterial effects.

Material Characteristics of Lime Plaster in Goguryeo Mural Tombs (I): Focusing on Lime Plaster Excavated from Anak Tomb No.3

Physical and chemical investigations were conducted on lime sample from Anak Tomb No.3 to determine the properties of the plaster material. The morphological and physical characteristics of the specimens were analyzed using both a microscope and a polarizing microscope. The constituent materials were identified through X-ray diffraction and scanning electron microscope-energy dispersive spectrometer, and the qualities of the mixed material were established through thermal analysis. Additionally, micro-computed tomography was used to non-destructively confirm the internal structure and density characteristics. The lime sample was recognized as a lime plaster material with two unique layers. Each layer shows variations in material properties. It is speculated that this lime specimen was used to finish the edges of the authentic wall within Anak Tomb No.3. Through the synthesis of various morphological attributes and physical properties; the whiteness, durability, thinness, and repetition of the layers, as well as smoothness of the lime plaster used for Anak Tomb No. 3 indicate that a high level of lime wall plastering technique was used in Goguryeo Tomb. It was possible to evaluate the refined level of lime wall manufacturing technology in the Goguryeo era.

Insights into factors influencing coal gangue-filled backfill cemented by self-consolidating alkali-activated slag grouts

The cemented backfilling is an effective measure to mitigate surface subsidence caused by mine goaf and to consume solid waste generated from mining activities. In this study, sodium hydroxide (SH) and sodium silicate (SS) were used as activators to respectively prepare self-consolidating alkali-activated slag grout (AASG) and alkali-activated fly ash-slag grout (AAFSG) for disposal of iron tailings (TS) and coal gangue (CG). These grouts were casted into a pre-placed CG skeleton to obtain coal gangue-filled backfill (CGFB). The factors influencing the mechanical properties of CGFB were investigated through fresh property tests (rheological properties, bleeding and segregation, setting time, and filling ability) and mechanical property tests of AASGs and AAFSGs. The micro-mechanical properties of the interfacial transition zone (ITZ) between grouts and CG aggregates were investigated by microhardness test. The microstructure of AASGs and AAFSGs was characterized using scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and thermogravimetric analysis (TGA). The results showed that the filling ability of fresh AASGs and AAFSGs was dependent on the flowability and increased with the modulus (SiO2/Na2O molar ratio). The compressive strength of CGFBs was shown to be influenced by the filling index and mechanical strength of AASGs and AAFSGs, which were also related to the modulus of activators. The microhardness gradually increased with distance from ITZ and then tended to be stable, higher modulus led to enhanced microhardness around ITZ, which benefited the mechanical properties of CGFB by strengthening the weak ITZ.

Preparation and strength formation mechanism of alkali-stimulated spontaneous combustion gangue-granulated blast furnace slag backfill.

Spontaneous combustion gangue (SCG) is often used as aggregate in traditional cemented paste backfill (CPB) for mine backfill, but the activation of SCG is insufficient. To stimulate the activity of SCG for the preparation of spontaneous combustion gangue-granulated blast furnace slag backfill (SGB), a new CPB was prepared by activating SCG via a mechanochemical composite activation method and adding ground granulated blast furnace slag (GGBS) to improve its activity. The mixing ratio was optimized by the response surface method and satisfaction function, and the strength formation mechanism was analyzed by scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR). The results showed that SCG had a certain pozzolanic activity, and the optimal grinding time was 30 min. The optimal mix ratio was 82.58% mass concentration, 2.93% alkali content, 30% GGBS content, and 52.92% fine gangue rate. Calcium silicate hydrate (C-S-H) gel and calcium aluminate sulfate hydrate (C-A-S-H) gel were the main reaction products of backfill, and with increasing curing age, C-S-H gel in the reaction system was gradually converted into C-A-S-H gel. FTIR analysis results showed that there were H-O-H, Si-O, and Si-O-T (T was Si or Al) bonds in the product, indicating that C-S-H gel and C-A-S-H gel were formed in the product. A new damage constitutive model was developed. The damage constitutive model could completely describe the backfill stress-strain curve. The study verified the feasibility of preparing cemented paste backfill with SCG and GGBS, which was beneficial to clean coal mine production and environmental protection.

Microstructural and mechanical properties of a high-strength geopolymer based on coal-based synthetic natural gas slag cured at ambient temperature

In this study, an effort was made to enhance the mechanical properties of coal-based synthetic natural gas slag (CSNGS) geopolymer with curing at ambient temperature by incorporating ground granulated blast furnace slag (GBFS). The effects of GBFS content, activator modulus and alkali content on the compressive strength of CSNGS-GBFS (CG) geopolymers were analyzed, and the microstructural characteristics and the compositional evolution of reaction products were also investigated by X-ray diffraction (XRD), scanning electron microscope-energy dispersive spectrometer (SEM/EDS), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analyzer (TG) tests. It was found that the mechanical properties of CG geopolymers was highly dependent on the of GBFS content. When the GBFS content was 50%, the 1-day and 28-day strengths of the geopolymer were 50.8 MPa and 120.2 MPa, respectively. Increasing alkali content resulted in the strength of geopolymer to increase and then decrease, whereas, the strength of geopolymer increased monotonically with a decrease in activator modulus. The results also showed that with increasing the GBFS contents, the characteristic peaks corresponding to the gels in the XRD patterns became gradually obvious with highly denser microstructures formed by a number of gels in the SEM micrographs, and the Ca/Si ratio and Ca/(Si + Al) ratio of the reaction products were increased, revealing that the gels generated in CG geopolymers was a mixture of N-A-S-H and C-(A)-S-H gels, which corroborated with the observed the stretching vibration of Si–O-T (T = Si or Al) in FT-IR spectrum shifted from 1013 cm−1 to 990 cm−1 and the corresponding temperatures of the mass loss peaks increased form 104 °C–114 °C. In addition, the dissolution of raw materials was promoted owing to the reduction of the activator modulus, but the change of activator modulus had little effect on the thermal stability of the gels. These findings suggest that CSNGS has the potential to prepare high-strength geopolymers at ambient temperature, providing an attractive avenue for reducing the environmental impact of CSNGS and conserving natural resources.

Study on adsorption and dust suppression mechanism of urease-producing bacteria on coal-soil mixed dust

Air pollution prevention and control is the primary problem faced by coal mines, in which coal and soil dust are the most serious pollution. However, different coal-soil ratios inevitably affect the dust suppression efficiency of microbial dust suppressants. In this paper, the adsorption mechanism of Bacillus X4 (B.X4), a urease-producing bacteria, on different coal-soil ratios dust surface was investigated to clarify the impact mechanism on the dust suppression of microbial dust suppressants. Both scanning electron microscopy (SEM) and adsorption isotherms showed that B. X4 could adsorb on dust surface and the adsorption was single-layer adsorption. The adsorption kinetic indicated that the adsorption was chemical adsorption. With the increase of soil dust content, the better the adsorption and consolidation effect, the better the dust suppression effect. Zeta potential, scanning electron microscope, Energy dispersive spectrometer (SEM-EDS), and X-ray diffractometer (XRD) results all demonstrated that CaCO3 was formed in dust treated with microbial dust suppressants, which could effectively cement the dust and suppress its flying.

Study on the mechanism of the effect of biomass ash on the erosion and adhesion behavior of Al2O3 ceramic particles

Biomass coupled with photothermal gasification technology is a new type of technology using heat carriers to transfer the solar energy to supply heat, and directs the solar energy absorbed by the heat carrier to provide a continuous heat source for biomass gasification. To investigate the erosion and adhesion mechanism of cornstalk ash (CSA) on heat carriers (Al2O3 ceramic spheres) during heat transfer, ash fusion temperature analyzer (AFTA) and FactSage thermodynamics software were used to analyze the effect of alumina addition over CSA sintering from the perspective of melting point, high-temperature heating stage coupled with optical microscope system (HTSOM) was used to observe of the adhesion behavior of CSA on the surface of ceramic spheres, X-ray diffractometry (XRD) and Laser-induced breakdown spectroscopy (LIBS) as well as SEM-EDS (Scanning electron microscope - Energy dispersive spectrometer) were used to detect the mineral evolution from both matter and elements. The results showed that the sintering stage (FT-DT) of CSA extended by adding more than 5 wt% of Al2O3 to CSA. Furthermore, it was found that as the temperature increased, Al-containing minerals such as pyroxene and chalcocite were formed, which indicated the CSA began to erode the heat carrier by mineral evolution on the surface of ceramic spheres. At high temperatures (>1200 ℃), CSA completely melted to form a liquid phase that wrapped around the surface of the ceramic spheres, which played a role in insulation layer during the cooling process to reduce the cooling rate of the surface of the ceramic sphere, resulting in more evident slagging problem. At the same time, the K and Ca element in the CSA was captured by ceramic spheres. The mineral transformation between the ceramic spheres and CSA was simulated by FactSage thermodynamic software, and it was found that the addition of Al2O3 resulted in the increase of the ash melting temperature and the formation of Al-containing mineral matters such as nepheline and augite.

Efficient removal of Cr(VI) by polydopamine-modified lignin from aqueous solution: Batch and XAFS studies

Lignocellulose has the potential to become a bio-based adsorbent due to its biodegradability and renewability. In this study, a novel polydopamine-functionalized-lignin (lignin@PDA), prepared via self-polymerization of dopamine (PDA) on lignin, was used as a bio-based adsorbent for rapid scavenging of hexavalent chromium (Cr(VI)). The morphology, functional groups, crystalline structure, and chemical composition of lignin@PDA were characterized with a scanning electron microscope–energy dispersive spectrometer, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The Cr(VI) adsorption process of lignin@PDA was studied using batch experiments as a function of pH, ionic strength, adsorbent dose, and contact time at room temperature. The adsorption rate of lignin@PDA was five times greater than that of the unmodified lignin, with a maximum adsorption capacity of 102.6 mg/g in an acidic medium. The adsorption of Cr(VI) on lignin@PDA fit the pseudo-second-order equation and the Freundlich model, indicating that the adsorption process was mainly dominated by chemisorption and surface complexation. The thermodynamic parameters showed that adsorption of Cr(VI) on lignin@PDA was an endothermic and spontaneous process. The X-ray absorption fine structure results showed that sorption and reduction of Cr(VI) into Cr(III) occurred simultaneously on lignin. Moreover, PDA coating not only improved the reactivity of lignin but also promoted the complete reduction of Cr(VI) by lignin. According to these results, polydopamine-functionalized-lignin is a promising bio-based adsorbent for immobilization of Cr(VI) from wastewater.

The Vertical Distribution of Ice-Nucleating Particles over the North China Plain: A Case of Cold Front Passage

Ice-nucleating particles (INPs) are crucial for cloud freezing processes in the atmosphere. Given the limited knowledge about the vertical distribution of INPs and its relation to aerosols in China, we present two aircraft observations of INPs over the North China Plain on 23 October 2019 and 25 October 2019, before and after a cold front passage. We used a well-established method to identify the INPs on a silicon wafer and then performed single-particle chemical composition analysis using an environmental scanning electron microscope-energy dispersive spectrometer (ESEM-EDS). The INP concentrations range from 0.1 to 9.2 L−1 within activation temperatures from −20 to −29 °C. INPs are mostly concentrated within the boundary layer, and their concentration shows a decreasing trend with height (0.5~6 km) before the cold front passage. However, the highest INP concentration always appears at higher altitudes (4~5 km) after the cold front passage. The cold front passage also significantly weakens the correlations between the concentrations of INPs and aerosol particles at different sizes. The activated fraction (AF) of total aerosols increases from 10−6 to 10−4 with height from near ground to 6 km, reflecting a better nucleating capacity of the aerosols at higher altitudes. There is no obvious variation in AF after the cold front passage. Chemical analysis reveals that the INPs containing mineral dust components comprise the majority of total INPs during both flights. The proportion of pure mineral dust declines from 52.2% to 43.5% after the cold front passage while the proportion of mixed mineral dust increases from 23.9% to 45.7%, suggesting that an increased probability of aging or coating of INPs is introduced by the cold front during their long-distance transport. In addition, 88% of INPs have a diameter larger than 1 μm. This indicates that larger aerosols (>1 μm) are the major contributors to INPs at high altitudes despite their relatively low abundance. Our results demonstrate a significant impact of transport events on the sources and vertical distribution of INPs in the atmosphere.

Experiment and Improvement Mechanism Analysis on the Mechanical Properties of Improved Chlorine Saline Soil

Chlorine saline soil has adverse engineering geology such as dissolution, collapse, and pulping, the recycling of saline soil in subgrade treatment is of great research significance. First, the unconfined compressive strength (UCS) test was conducted using an orthogonal test design, and the optimal ratios of salt content, cement content, lime content, fiber content, and fiber length were determined. Second, the cyclic loading (CL) test was conducted using an orthogonal test design, and the influence of five factors, including freeze–thaw (FT) times, CL times, stress level (SL), amplitude, and frequency, on peak intensity, peak strain, and cumulative strain under FT cycles and natural air-drying (A-D) conditions were determined. Finally, the improvement mechanism of the above inorganic materials was microscopically analyzed by scanning electron microscope-energy dispersive spectrometer and X-ray diffraction tests. The UCS test results show that the improving effect of the optimal ratio for chlorine saline soil was best when the optimal ratio values were 3% (salt content), 8% (cement content), 12% (lime content), 0.2% (fiber content), and 18 mm (fiber length). CL test results show that with the increase in natural A-D time, it was found that the FT number and SL have significant effects on the strength, the number of FT times and cycle times have significant effects on the deformation, and the frequency and cycle times have significant effects on the cumulative deformation. From the microstructure analysis, the improvement mechanism is mainly the filling of pores and linking particles by water-hard gels and gas rigid gels to make the microstructure dense, effectively reduce pores, and effectively improve the engineering characteristics of chlorine saline soil. The results of this study provide a scientific basis for the engineering design of subgrade in arid areas and the in situ recycling of saline soil.

Cr(VI) reduction by Agrobacterium sp. Cr-1 and Lysinibacillus sp. Cr-2, novel Cr(VI)-reducing strains isolated from chromium plant soil.

The bioremediation of Cr(VI)-contaminated soil is a promising strategy; however, the performance of Cr(VI)-reducing bacteria is limited by the toxicity of Cr(VI). In this study, two novel Cr(VI)-reducing bacteria were isolated from a Cr salt plant and identified as Agrobacterium sp. and Lysinibacillus sp. The Cr(VI) reduction conditions of the two strains were optimized. At a Cr(VI) concentration of 500mg/L, Agrobacterium sp. Cr-1 reduced Cr(VI) with a removal rate of 96.91%, while that for Lysinibacillus sp. Cr-2 was 92.82%. First-order reaction kinetic equations simulated the positive relationship between time and Cr(VI) concentration during Cr(VI) reduction in these two strains. Agrobacterium sp. Cr-1 was further studied, and the effects of different cell components on Cr(VI) reduction were detected. The extracellular extracts of Agrobacterium sp. Cr-1 played a major role in Cr(VI) reduction, followed by intracellular extracts and cell membranes. The scanning electron microscope-energy dispersive spectrometer (SEM-EDS) images show that the precipitation was Cr. The high Cr(VI) reducing ability of Agrobacterium sp. Cr-1 suggests that this strain is promising for the remediation of Cr(VI)-contaminated sites.

Decrease in the organic content of refinery wastewater by photocatalytic Fenton oxidation using iron-doped zeolite: Catalyst preparation, characterization, and performance

A Fe-exchanged zeolite photocatalyst was synthesized by applying an ion exchange method and used to examine the degradation of effluent from the petroleum industry. The exchanged zeolite catalyst was characterized by X-ray diffraction, X-ray fluorescence, Fourier-transform infrared spectroscopy, Naioatomic force microscopy, Brunauer-Emmett-Teller surface area, and Filed Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometer. Characterization of the catalyst confirmed its composition and phase but also showed a decrease in uniformity and crystallinity. The photocatalyst was tested under ultra-violet lamp irradiation for the removal of pollutants in wastewater from Iraqi petroleum refineries. Experiments were performed using a stirred batch reactor with an initial chemical oxygen demand of 492 mg/L. The exchanged zeolite was used as a catalyst and H2O2 was used as an oxidant. For synthetic wastewater, 99.84 % of organic pollutants were removed in 120 min. Chemical oxygen demand removal values were almost the same (85.29 and 81.67 %, respectively) for real wastewater obtained from the Dora Refinery and North Gas Company. Furthermore, the exchanged zeolite displayed excellent stability and low release of iron ions from the catalyst during the reaction (less than 11 mg/L). The catalyst was recycled five times with power consumption ranging from 691.18 to 826.96 kWh/kg COD.

Synthesis of Mg–K-biochar bimetallic catalyst and its evaluation of glucose isomerization

Highly efficient isomerization of glucose to fructose is essential for valorizing cellulose fraction of biomass to value-added chemicals. This work provided an innovative method for preparing Mg-biochar and Mg–K-biochar catalysts by impregnating either MgCl2 alone or in combination with different K compounds (Ding et al. in Bioresour Technol 341:125835, 2021, https://doi.org/10.1016/j.biortech.2021.125835 and KHCO3) on cellulose-derived biochar, followed by hydrothermal carbonization and pyrolysis. Single active substance MgO existing in the 10Mg–C could give better catalytic effect on glucose isomerization than the synergy of MgO and KCl crystalline material present in 10Mg–KCl–C. But the catalytic effect of 10Mg–C was decreased when the basic site of MgO was overloaded. Compared to other carbon-based metal catalysts, 10Mg–KHCO3–C with 10 wt% MgCl2 loading had excellent catalytic performance, which gave a higher fructose yield (36.7%) and selectivity (74.54%), and catalyzed excellent glucose conversion (53.99%) at 100 °C in 30 min. Scanning electron microscope–energy dispersive spectrometer and X-Ray diffraction revealed that the distribution of Mg2+ and K+ in 10Mg–KHCO3–C was uniform and the catalytic active substances (MgO, KCl and K2CO3) were more than 10Mg–C (only MgO). The synergy effects of MgO and K2CO3 active sites enhanced the pH of reaction system and induced H2O ionization to form considerable OH− ions, thus easily realizing a deprotonation of glucose and effectively catalyzing the isomerization of glucose. In this study, we developed a highly efficient Mg–K-biochar bimetallic catalyst for glucose isomerization and provided an efficient method for cellulose valorization.Graphical

Structural and in vitro biological properties of strontium substituted bio-waste derived wollastonite for bone regeneration

Strontium (Sr) substituted wollastonite bioceramics were prepared by a modified sol-gel technique using bio-wastes such as eggshell as calcium oxide source and rice husk as silica source. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) were used to perform structural analysis. Bioactivity was examined by testing the apatite mineralization ability in vitro by immersing the ceramic pellets in simulated body fluid (SBF) for various time periods. Degradation assay was performed in Tris buffer solutions by following the protocol in ISO 10993-14 standard. Cytocompatibility and cell proliferation were analyzed at different concentrations using osteoblast like MG 63 cells by MTT assay. The results show that the addition of Sr increases the density and mechanical properties of wollastonite but decreases with SrO above 2.5 mol.%. Pure and Sr containing wollastonite possessed excellent apatite formation ability with continuous degradation under physiological conditions. The results of cell culture studies revealed that all prepared ceramics were non-toxic to osteoblast-like cells at different doses (0–1000 μg/mL), and wollastonite ceramics containing Sr also enhanced cell proliferation.