Scanning Electron Microscope And Energy Dispersive Spectrometer Research Articles

The effect of bacteria on uranium sequestration stability by different forms of phosphorus

ABSTRACT Immobilisation of uranium (U (VI)) by direct precipitation of uranyl phosphate (U-P) exhibits a great potential application in the remediation of U (VI)-contaminated environments. However, phosphorus, vital element of bacteria’s decomposition, absorption and transformationmay affect the stability of U (VI) with ageing time. The main purpose of this work is to study the effect of bacteria on uranium sequestration mechanism and stability by different forms of phosphorus in a water sedimentary system. The results showed that phosphate effectively enhanced the removal of U (VI), with 99.84%. X-Ray Diffraction (XRD), Scanning Electron Microscopy and Energy Dispersive Spectrometer (SEM-EDS), and X-ray Photoelectron Spectroscopy (XPS) analyses imply that U (VI) and U (IV) co-exist on the surface of the samples. Combined with BCR results, it demonstrated that bacteria and phosphorus have a synergistic effect on the removal of U (VI), realising the immobilisation of U (VI) from a transferable phase to a stable phase. However, from a long-term perspective, the redissolution and release of uranium immobilisation of U (VI) by pure bacteria with ageing time are worthy of attention, especially in uranium mining environments rich in sensitive substances. This observation implies that the stability of the uranium may be impacted by the prevailing environmental conditions. The novel findings could provide theoretical evidence for U (VI) bio-immobilisation in U (VI)-contaminated environments.

Harnessing chemical functionality of xylan hemicellulose towards carbohydrate polymer-based pH/magnetic dual-responsive nanocomposite hydrogel for drug delivery

This study reports a pH/magnetic dual-responsive hemicellulose-based nanocomposite hydrogel with nearly 100 % carbohydrate polymer-based and biodegradable polymer compositions for drug delivery. We synthesized pure Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) using a co-precipitation method, then engineering xylan hemicellulose (XH), acrylic acid, poly(ethylene glycol) diacrylate, and Fe3O4 to synthesize the pH/magnetic dual-responsive hydrogel (Fe3O4@XH-Gel), through graft polymerization on XH with in-situ doping Fe3O4 MNPs initiated by the ammonium persulfate/tetramethylethylenediamine redox system. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H NMR), X-ray diffractometry (XRD), scanning electron microscopy and energy dispersive spectrometer (SEM-EDS), high-resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET), swelling gravimetric analysis, vibrating sample magnetometer (VSM) were employed to analyze the hydrogel's chemical structures, morphologies, pH-responsive behaviors, and magnetic responsiveness characteristics, mechanical and rheological properties, as well as cytotoxicity and biodegradability. The results indicate that the Fe3O4@XH-Gel exhibited excellent dual responsiveness to pH and magnetism. Furthermore, an emphasis was placed on the in-depth analysis of the pH response mechanism. Finally, we utilized this cutting-edge hydrogel to investigate the controlled-release behavior of two model drugs, Acetylsalicylic acid and Theophylline. The hydrogel demonstrated exceptional controlled release attributes, positioning it as a potential carrier for targeted drug delivery, particularly to the gastrointestinal conditions.

Study on activation of fluorogypsum by sodium sulfate and sodium nitrite

Given the issues related to poor hydration activity, long setting time and low early strength of industrial by-product fluorogypsum (FG), the composite modifiers (Na2SO4 and NaNO2) were utilized to enhance its reactivity. The investigation of the mechanism involved the utilization of contemporary analytical methods, including X-ray diffraction (XRD), 1H low-field nuclear magnetic resonance (NMR), and Scanning electron microscope and Energy Dispersive Spectrometer (SEM-EDS). The results demonstrated that the incorporation of modifiers significantly enhanced both the hydration rate and activity of fluorogypsum. The optimum concentration of the composite modifier was found to be 1.5 wt% Na2SO4 and 0.5 wt% NaNO2. The addition of modifiers (1.5 wt% Na2SO4 and 0.5 wt% NaNO2) significantly shortens the setting time of FG paste, reducing it by approximately 500 min compared to the control sample. After 28 days of curing, the flexural strength and compressive strength of the fluorogypsum sample containing modifiers (1.5 wt% Na2SO4 and 0.5 wt% NaNO2) increased by 55.5 % (reaching 4.2 MPa) and 31.5 % (reaching 37.6 MPa), respectively. The modifiers facilitate the transformation from anhydrite (CaSO4, AH) to dihydrate gypsum (CaSO4·2H2O, DH). Both NaNO2 and Na2SO4 alter the growth rates of different crystal axes during DH crystal growth, transforming them into prismatic and needle-shaped DH. The prismatic and needle-shaped DH crystals were arranged in layers, resulting in a compact structure with low hole content and few pores, which led to increased density of the hardened paste and higher strength. The current study provides evidence that the inclusion of composite modifiers greatly improves the activity of FG, making it more efficient in the field of building materials.

Preparation of Lanthanum-Modified Tea Waste Biochar and Its Adsorption Performance on Fluoride in Water.

In this study, tea waste was used as a raw material, and TBC (tea waste biochar) was prepared by pyrolysis at 700 °C. La(NO3)3·6H2O was used as the modifier to optimize one-way modification; the orthogonal experiment was undertaken to determine the optimal preparation conditions; and La-TBC (lanthanum-modified biochar) was obtained. The key factors for the adsorption of fluoride by La-TBC were investigated by means of batch adsorption experiments, and kinetics and isothermal adsorption experiments were carried out on the adsorption of fluoride in geothermal hot spring water. The adsorption mechanism of fluoride by La-TBC was analyzed via characterization methods such as SEM-EDS (Scanning Electron Microscope and Energy Dispersive Spectrometer), BET (Brunauer-Emmett-Teller), FTIR (Fourier transform infrared), XRD (X-ray diffraction), and so on. The results show that La-TBC had the best adsorption effect on fluoride at pH 7. The process of adsorption of fluoride follows the pseudo-second-order kinetics and Langmuir isothermal model, and the maximum theoretical adsorption quantity was 47.47 mg/g at 80 °C, while the removal rate of fluoride from the actual geothermal hot spring water reached more than 95%. The adsorption process was dominated by the monolayer adsorption of chemicals, and the mechanisms mainly include pore filling, ion exchange, and electrostatic interaction.

Improvement of Microstructure and Mechanical Properties of Hot‐Formed Steel with Ce Addition

In this article, the effect of Ce element on the microstructure and mechanical properties was studied by Ce addition to the hot‐formed steel. Scanning electron microscope and energy dispersive spectrometer (SEM‐EDS) was used to analyze the improvement effect of Ce on inclusions and the effect of inclusions on fracture behavior; Electron back scattering diffractometer (EBSD) was used to analyze the refinement and strengthening effect of Ce on martensitic grains; transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM) was used to analyze the microstructure strengthening effect and microalloying effect of solid solution Ce in hot‐formed steel. Through a systematic analysis of mechanical properties and microstructure, the mechanism of Ce enhances the strength and elongation of hot‐formed steel was clarified. Besides, this work provides a research basis for further improving the safety and machinability of hot‐formed steel.

Recovery of iron and alumina from iron–aluminum symbiotic ore via low–calcium carbothermal reduction

The iron-aluminum symbiotic ore, as an important strategic resource, has not been utilized due to the complex relationship between iron-aluminum minerals. In this work, a low-calcium carbothermal reduction method was proposed to treat the iron-aluminum symbiotic ore, and its performance and reaction mechanism were studied based on the Fe2O3-Al2O3-SiO2-CaO-Na2O system using XRF (X-ray fluorescence), XRD (X-ray diffractometer), SEM-EDS (scanning electron microscopy and energy dispersive spectrometer), VSM (vibrating sample magnetometer) and XPS (X-ray photoelectron spectroscopy), while the practical application on the iron–aluminum symbiotic ore was verified. The silicon is in the form of sodium calcium silicate compound during the low–calcium carbothermal reduction process, and the formation sequence of this compounds is Na2Ca3Si2O8 → Na2Ca2Si2O7 → Na2CaSiO4 with the increase of Na2CO3 amount. The iron- and aluminum-bearing phases in the reduction product are Fe, NaAlO2 and a small amount of ferrous and ferric compounds, NaAl11O17 and NaAlSiO4. Fe can be aggregated in the iron concentrate via magnetic separation and NaAlO2 can be recovered by leaching process. The main minerals in the reduction product from the iron-aluminum symbiotic ore obtained by the low-calcium reduction process are Fe, NaAlO2, Na2CaSiO4 and NaAlSiO4, and the iron metallization efficiency, the leaching efficiency of Al2O3 and the content of iron in the concentrate are 84.24%, 86.07% and 75.70% respectively under the optimal reduction conditions.

Efficient flotation separation of picromerite and halite by a novel collector of sodium dodecyl benzene sulfonate

Common reverse flotation is difficult to separate efficiently picromerite with a high halite content. This work employed direct flotation to separate picromerite and halite, using sodium dodecyl benzene sulfonate (SDBS) as a novel picromerite collector. The flotation performances were evaluated by single and real ore flotation tests, with results indicating that K+ recovery was 95.89%, while Na+ content was less than 2% in the concentrate at an SDBS dosage of 200 g/t, which suggested SDBS was an effective picromerite collector with excellent separation performance. The interaction mechanism was investigated by adsorption experiment, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope and Energy Dispersive Spectrometer (SEM-EDS), and X-ray Photoelectron Spectroscopy (XPS) analysis. The adsorption experiments demonstrated that picromerite had a stronger affinity to SDBS than halite, confirming that SDBS exhibited good selectivity in the flotation of picromerite and halite. FTIR and SEM-EDS analysis revealed that SDBS adsorbed on the picromerite surface. XPS results further unveiled that SDBS chemisorbed on the picromerite surface through the strong complexation between sulfonic acid groups and Mg atoms on the picromerite surface, forming O-Mg bonds. This study provides a new perspective on the efficient separation of picromerite and halite, facilitating a high production efficiency of picromerite.

Study on the effect of M/P ratio of magnesium phosphate cement coatings on reducing urban heat absorption

Using reflective coatings to enhance the reflective ability of urban underlying surface can effectively reduce building energy consumption and alleviate urban heat island effect. Magnesium phosphate cement (MPC), which consists of high near-infrared reflectivity magnesium oxide (MgO) and phosphate as the main raw materials, is a potential reflective coating. This paper studied the reflection characteristics and mechanisms of MPC with different mass ratios of MgO to phosphate (M/P). The reflectivity test results indicated that the reflectivity of MPC increased with the increase of M/P ratio, with a near-infrared reflectance of 71.74% at an M/P of 10. This was mainly related to its surface chromaticity and micromorphology. In the matter of color characteristic, it was found that the increase of M/P ratio improved the brightness and weakened the performance of other colors, which was conducive to improving the reflective effect. In the matter of micromorphology, scanning electron microscopy and energy dispersive spectrometer (SEM-EDS) analysis confirmed that there were more unreacted MgO particles and less hydration products on the MPC surface with high M/P ratio, which resulted in higher reflectivity and lower bonding strength. Finally, indoor irradiation experiments were conducted to verify the heat reduction effect of MPC coating on asphalt pavement. The results indicated that the surface temperature of the specimen coated with MPC decreased by 15.3 ℃ compared to the control specimen. Therefore, it could be concluded that MPC is a promising reflective coating that can be used to reduce urban heat absorption.

Electrochemical characteristic analysis for surface passivation layer of galena and chalcopyrite in acid corrosion

The surface passivation layer of galena and chalcopyrite after sulfuric acid corrosion can enlarge the difference in their floatability. The floatability test shows that sulfuric acid corrosion strongly inhibits galena’s floatability but has no effect on chalcopyrite. Scanning electron microscope and energy dispersive spectrometer (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and Eh-pH diagram analysis showed that the galena surface was oxidized to form a coarse passivation layer of PbSO4, while the chalcopyrite surface dissolved only a small amount of Fe2+ ions and formed a dense sulfide layer (Cu(1-x)Fe(1-y)S2). Open circuit potential (OCP), polarization curve, and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical characteristics of the surface passivation layer on galena and chalcopyrite after sulfuric acid corrosion. The electrochemical analysis results showed that the electrostatic potential increased and the electrochemical activity decreased on the galena and chalcopyrite surface due to corrosion action; the current density of corroded galena was stable around 17.41 μA·cm−2 and the surface oxidation reaction can be further carried out, while the current density of corroded chalcopyrite was reduced from 17.91μA·cm−2 to 9.01 μA·cm−2, and the surface reaction was gradually inhibited; the double electric layer resistance (Rt) and the resistance (Rp) for the passivation layer of corroded galena both decreased significantly, and the passivation layer could be further generated from the surface to the interior, while the Rt and Rp of corroded chalcopyrite increased significantly and prevented the dissolution of internal components. The electrochemical analysis results were consistent with each other and confirmed by SEM-EDS and XPS conclusion. In addition, the corrosion-flotation process has been used to achieve high-efficiency separation of the galena-chalcopyrite mixture.

Chloride binding of AFm in the presence of Na+, Ca2+ and Ba2+

AFm (Ca4Al2(SO4)(OH)12·6H2O) played a significant role in chloride binding by exchanging its interlayer anion (SO42-) with Cl- to form FS (Ca4Al2Cl2(OH)12·4H2O) or KS (Ca4Al2(SO4)0.5Cl(OH)12·6H2O) in cement paste. Different cations including Na+, Ca2+ and Ba2+ might have different effects on the reaction among AFm, KS and FS. To explore the influence mechanism of the cation type on chloride binding of AFm, the effect of Na+, Ca2+ and Ba2+ on chloride binding of AFm was comparatively analyzed. AFm was added into NaCl, CaCl2 and BaCl2 solutions with different chloride concentrations including 0.1 mol/L, 0.3 mol/L, 0.5 mol/L and 1.0 mol/L. The chloride binding capacity was determined by Mohr method. X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope and energy dispersive spectrometer (SEM-EDS) were used to investigate the phase compositions of AFm samples. Gibbs free energy minimization software (GEMS) could predict the final phase compositions in thermodynamic equilibrium. The results demonstrated that chloride binding capacity of AFm in NaCl, CaCl2 and BaCl2 solutions was declined in order: BaCl2 > CaCl2 > NaCl. The mechanism behind was that: AFm could produce KS and FS in NaCl, CaCl2 and BaCl2 solutions. Different from AFm in NaCl solution, gypsum was generated in CaCl2 solution and BaSO4 was formed in BaCl2 solution, which was attributed to Ca2+ and Ba2+ participating in the phase transformation reaction of AFm.

Phase Equilibria of CaO-SiO2-La2O3-Nb2O5 System in Reducing Atmosphere

In the current work, the phase equilibria of CaO-SiO2-La2O3-Nb2O5 system at 1200 °C in reducing atmosphere (PO2 = 10−15 atm) was investigated according to the melting separation process for extracting lanthanum and niobium resources from Bayan Obo tailing. High temperature equilibrium experiment, scanning electron microscope, and energy dispersive spectrometer (SEM-EDS) were used to determine the compositions of equilibrium phases. According to the experiment results, the phase equilibria of the CaO-SiO2-La2O3-Nb2O5 system in reducing atmosphere were ascertained and the 1200 °C isothermal phase diagram of CaO-SiO2-La2O3-Nb2O5 system in reducing atmosphere was constructed. The research results not only play an important role in guiding the development of the lanthanum and niobium extraction process, but also enrich the thermodynamic data of relevant silicate slag systems.

Mechanical properties and microstructure evaluation of fly ash - Slag geopolymer foaming materials

The existing fly ash-slag foaming geopolymer materials generally have the shortcomings of low fly ash content and low porosity. It is urgent to develop geopolymer foaming materials with high fly ash content and high porosity. Using fly ash and slag as the main raw materials, geopolymer foaming materials were prepared by alkali activation. The effects of activator content and sodium silicate modulus on the macroscopic mechanical properties, pore structures and microstructures of geopolymer foaming materials were studied. The experimental results showed that when the activator content was 21% (wt.) and the modulus of sodium silicate was 1, the specimen exhibited the best performance. The compressive strength of the specimen reached 2.18 MPa at 28 d, the porosity was 63.07%, and the average pore sizes of macroscopic pores were 920 μm. Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Scanning Electron Microscopy and Energy Dispersive Spectrometer (SEM-EDS) analysis showed that when the content of activator was 21% and the modulus of sodium silicate was 1, the reaction grade of the system was the highest, reached 55.12%, meanwhile the main product Sodium silicate hydrate (N-A-S-H) gel produced the largest amount. The fractal dimension calculations showed that the spatial complexity of a specimen with large pores was greater than that of a specimen with small pores. This study can provide a basis for the design of geopolymer foaming materials with high proportion of fly ash and high porosity.

Roles of CLDHs and TEA on Portland cement mortar/paste: Strength, hydration and chloride binding

In this study, the synergistic effects of calcined Mg-Al layered double hydroxides (CLDHs) and triethanolamine (TEA) on the hydration properties and chloride binding capacity of cement paste were investigated. The roles of incorporation of CLDHs and TEA in the cement pastes were evaluated by bound chloride rate, physical properties, reaction kinetics and microstructure. Experimental results show that the chloride ions are efficiently trapped by CLDHs at early stage, and the addition of TEA provides further stability. The mechanical strengths are decreased and obtained the low values at the 3 wt% and 6 wt% substitution level of CLDHs, and the negative phenomenon is improved with the incorporation of TEA. From the isothermal calorimetry (ICC), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) results, the induction period of C3S process is retarded, but hydration of C3A is accelerated. The enhancement of chloride binding ability is mainly attributed to the recrystallization generation of LDH-Cl and the formation of Friedel’s salt (FS) with the decomposition of calcium hydroxide (CH), which is facilitated by TEA due to the rapid reaction of the aluminum phase. The analyses of scanning electron microscope and energy dispersive spectrometer (SEM-EDS) indicates that the enriched elemental chlorine originated from the immobilization effect of LDHs phase and FS, which is the significant support for the binding properties of chlorides in cementitious materials.

Determination and Analysis of the Content and Distribution of Mineral Elements in Black Rice by SEM-EDS

Black rice has very superior medicinal value. Since ancient times, it has been used as a nourishing and health-care rice for medicine and food. It has powerful functions such as disease prevention, regulation of circadian rhythm, and promotion of physical recovery. It is suitable for long-term consumption. In this paper, optical microscope, scanning electron microscope and energy dispersive spectrometer (SEM-EDS) were used successively to visualize and quantitatively analyze the element distribution in the chalky and non-chalky areas of two indica rice varieties in Southern Henan. The results showed that black rice has rich C and O content, followed by N, P, S content, Mg, K, Ca, Mn, Zn content is less. The content of the O element in the chalky area is higher than that of the non-chalky area, while many elements such as C, N, P, S are significantly higher in the non-chalk areas than in the chalk areas; especially the N and S elements are the best indicators of protein, the content in chalkiness area was lower than that in non-chalky area. It can be inferred that the protein content in non-chalky part was higher than that in chalky part, that is, chalkiness character of black rice would affect the nutritional quality of rice. Therefore, our results showed the distribution of elements and protein in black rice, which is helpful for the cultivation of new high-quality black rice varieties in the future.

Green reduction of graphene oxide using Bacillus sphaericus

While chemical methods are often used to convert graphene oxide (GO) to reduced graphene oxide (RGO), chemical reduction is often environmentally unfriendly due to the high toxicity of many chemical reducing agents. To address this limitation, Bacillus sphaericus was used here for the green reduction of GO to RGO. Successful reduction was confirmed by various advanced characterization techniques including Ultraviolet–Visible (UV–vis), X-ray Powder Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscope and Energy Dispersive Spectrometer (SEM-EDS). With a new peak attributable to RGO at 261 nm appearing in UV–vis and XRD spectra of the reduced product also developed a new peak at 2θ = 24.6° characteristic of RGO. Successful reduction was also supported by Raman spectroscopy which showed that the ratio of the intensity band (D band: G band) increased from 0.99 to 1.17. FTIR and XPS both confirmed that specific OH (3399 cm−1), CO (1734 cm−1) and COC (287 eV) bonds were reduced. Cyclic voltammograms (CVs) showed that the produced RGO exhibited good conductivity (changed from 0.8 to 1.1 mW·cm−2). This work developed a green and easy operated method of synthesizing RGO using microorganisms.

Reuse of waste glass powder in alkali-activated metakaolin/fly ash pastes: Physical properties, reaction kinetics and microstructure

To better understand the reaction of waste glass powder (WGP) as precursor in geopolymerization process, the leaching of main active ions (Ca2+, Al3+ and Si4+) from waste glass powder in alkaline solution was evaluated. The roles of replacement of metakaolin (MK) by WGP on the alkali-activated material (AAM) pastes were investigated by physical properties, reaction kinetics and microstructure. Experimental results show that the active ions are efficiently dissolved and leached in sodium hydroxide solution. With the incorporation of WGP, the workability of pastes is improved due to the physical and chemical characteristics of WGP particles. The mechanical performances including strengths and volume density are enhanced and obtained the highest values at the 20 wt% substitution level of MK by WGP. From the isothermal calorimetry (ICC), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) results, the geopolymerization process is accelerated and additional binder gels are formed. These are attributed to the reactive components (especially CaO) in WGP. The analyses of mercury intrusion porosimetry (MIP) and scanning electron microscope and energy dispersive spectrometer (SEM-EDS) indicate that the denser microstructure originated from the enrichment of gels and filling effect of raw materials particles is the significant support for the development of mechanical properties of AAM pastes.

The Distribution of Mineral Elements and Protein in Soft Rice was Determined and Analyzed by SEM-EDS Technology

Soft rice is a kind of high-quality rice between glutinous rice and sticky rice. It has low amylose content, crystal clear grains, sweet taste, soft glutinous, and is suitable for cooking and porridge. Chalkiness in soft rice is a white opaque part formed by loose endosperm. It is an important character that affects the appearance quality, processing, and cooking quality of rice, and also an important limiting factor that restricts the standard rate of high-quality rice in China. The combination of scanning electron microscope and energy dispersive spectrometer (SEM-EDS) can be used for in-depth analysis of rice, visualization, and quantitative analysis of element distribution in rice. The results showed that there were many kinds of mineral elements in soft rice seeds, among which C and O were the most abundant, followed by N and P, and Mg, Al, P, S, K, Ca, Mn, and Zn were less. The contents of C, N, P, and S in the non-chalky area were significantly higher than those in the chalky area. Especially N and S were the best indicators of protein, and the contents in the chalky area were higher than those in the non-chalky area. It means that the protein content in the chalky part of soft rice seed is less than that in the non-chalky part, which affects the nutritional quality of soft rice. Therefore, the results of this study laid a solid foundation for the in-depth analysis of the distribution of mineral elements and protein in soft rice and their effects on the quality of soft rice, which also provided important information for the cultivation of new high-quality rice varieties in the future.

Tiopronin as a novel copper depressant for the selective flotation separation of chalcopyrite and molybdenite

In this work, an environmental-friendly surfactant named tiopronin was tested as a novel copper depressant in copper-molybdenum sulfide separation for the first time. The separation performances were evaluated by micro-flotation and the depression mechanism was revealed by means of Zeta potential, Scanning Electron Microscope and Energy Dispersive Spectrometer (SEM-EDS), X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) measurements. The micro-flotation tests demonstrated that tiopronin exhibited powerful depressing effect on chalcopyrite and it could achieve satisfactory separation results with high selectivity in wide pH range. The novel depressant had promising application prospect due to its high selectivity and low toxicity in compared with conventional one. Zeta potential, SEM-EDS, XPS and ToF-SIMS measurements manifested that tiopronin was chemisorbed on chalcopyrite surface through the strong chemical reaction of copper sites with CO and SH groups in tiopronin molecular to form five-membered chelating rings. In addition, a possible depression model was proposed.

Effect of supercritical CO2 saturation pressures and temperatures on the methane adsorption behaviours of Longmaxi shale

Abstract To investigate the effects of supercritical CO2 (SC–CO2) saturation pressures and temperatures on the methane adsorption capacity of shale, total organic carbon (TOC) analysis, X-ray diffraction (XRD) analysis, scanning electron microscope and energy dispersive spectrometer (SEM/EDS) analysis, low-pressure N2 adsorption (LP-NA), and high-pressure methane adsorption (HP-MA) were conducted on raw and SC–CO2–saturated (8, 12, 16 MPa; 40, 60, 80 °C) shale collected from the Sichuan Basin. Results indicate that the excess adsorption isotherm of shale to methane clearly exhibited excess adsorption characteristics with increasing adsorption pressures. This excess methane adsorption capacity decreased after SC-CO2 saturation and is mainly attributable to decreases in the TOC content, clay minerals and specific surface area (SSA) in the SC–CO2–saturated shale. The density of adsorbed phase methane was considered at different adsorption models, and the results suggest that the Langmuir-Freundlich (LF) and Dubinin-Astakhov (DA) models better describe methane adsorption behaviours than the Langmuir and Ono-kondo models. The methane adsorption capacity of shale is closely related to the solubility of SC-CO2, which decreased significantly with increasing SC-CO2 saturation time and pressure, while the influence of SC-CO2 saturation temperatures was not evident at low-pressure (8 MPa). This study provides a theoretical reference for CO2 enhanced shale gas recovery.

Electrochemical Behavior of U3O8 in LiCl-KCl-NH4cl Under Air Atmosphere

In this work, the dissolution behavior of U3O8 in LiCl-KCl-NH4Cl melt was studied by electrochemical technique. The result of cyclic voltammetry (CV) indicated that the reduction/oxidation peaks of UO2 2+/UO2 + , which meant U3O8 could dissolve in LiCl-KCl melt assisted by NH4Cl. Meanwhile, UO2 2+ was also measured by UV-vis absorption spectra and fluorescence emission spectra. Potentiostatic electrolysis was carried out at -2.4 V and -0.5 V for 2 h in LiCl-KCl-NH4Cl-U3O8 system, and the products were analyzed by scanning electron microscope and energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD). The results showed that U metal and UO2 were obtained on Mo cathode at -2.4 V and -0.5 V, respectively. Acknowledgement The work was financially supported by the National Natural Science foundation of China (11675044, 21790373, 21876034 and 11875116), and the International Exchange Program of Harbin Engineering University for Innovation−oriented Talents Cultivation.