Scanning Electron Microscopy Equipped With Energy Dispersive X-ray Spectroscopy Research Articles

Experimental investigation and thermodynamic calculation of the Cu–Cr–Ti ternary system

The phase equilibria of the Cu–Cr–Ti ternary system were investigated based on key experiments coupled with thermodynamic modeling. Eighteen ternary alloys were prepared to determine the isothermal sections of the Cu–Cr–Ti system at 600 and 800 °C by means of X-ray diffraction (XRD) and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDS). Seven three-phase regions have been determined. A ternary compound τ1 was confirmed. The solubilities of Cr in the Cu–Ti binary compounds and Cu in the Cr–Ti binary compounds were measured. The substitutional and sublattice models were used to describe the solution phases and intermediate phases, respectively. Based on the thermodynamic descriptions of three binary systems as well as the experimental phase equilibria data available from the literature and the present work, thermodynamic assessment of the Cu–Cr–Ti system was carried out using the CALPHAD (CALculation of PHAse Diagrams) approach. A set of thermodynamic parameters was obtained and the isothermal sections and the liquidus projection of the Cu–Cr–Ti system were calculated. The calculated results agree well with the experimental data.

Using alkali-activated dredge sludge ash-bentonite for low permeability cutoff walls: The engineering properties and micromechanism

Although vertical cutoff walls can effectively contain groundwater pollution, vertical barriers constructed using conventional cement-bentonite-soil (CBS) mixtures exhibit poor permeability and produce considerable CO2 during cement production. The dredged sludge ash (DSA) has potential to be used as an eco-friendly source for vertical barriers building because of the remarkable pozzolonicity. In this study, a mixture consisting of MgO-activated dredged sludge ash (DSA) and bentonite was used to develop a low permeable MgO-activated DSA-bentonite-sand (MDBS) barrier material for application to vertical cutoff walls. The mechanical properties of MDBS and CBS mixtures were investigated and the hydration products and microstructure were examined using scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP). The results showed that the MDBS mixture exhibited excellent impermeability: the hydraulic conductivity of MDBS cured for 60 d reached the minimum (1.83 × 10−8 cm/s), and considerably superior to the common requirement (lower than 10−7 cm/s) for cutoff walls. The unconfined compressive strength of the MDBS cured for 60 d increased by approximately 112% compared to the samples cured for only 7 d. The hydration products in MDBS were mainly magnesium silicate hydrate and hydrotalcite, which filled the material pores more effectively than the hydration products of CBS (calcium silicate hydrate calcium hydroxide and ettringite). The hydration products, bentonite swelling, and pore size distribution determined the MDBS mechanical properties and permeability. It is verified that activated dredge sludge ash can be used as an ideal cutoff walls material instead of cement.

Removal of Congo red dye from aqueous environment by zinc terephthalate metal organic framework decorated on silver nanoparticles-loaded biochar: Mechanistic insights of adsorption

In this study, zinc terephthalate-metal-organic framework decorated on the surface of poultry manure-derived biochar (ZT-MOF@Ag@C) was successfully fabricated and employed as nano-adsorbent material for Congo Red (CR)-treated aqueous solution. The physical characteristics of the developed ZT-MOF@Ag@C adsorbent were analyzed by the Brunauer–Emmett–Teller (BET) theory, Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) Scanning Electron Microscopy equipped with Energy-Dispersive X-Ray Spectroscopy (SEM/EDS), and X-Ray Photoelectron Spectrometer (XPS). The characterization analysis revealed that biochar modification with ZT-MOF and AgNPs greatly enhanced the surface area. The mesopores ZT-MOF@Ag@C BET surface area of 1028 m2/g showed a maximum adsorption capacity of 416.6 mg/g. The Langmuir isotherm and pseudo-second order kinetic models best described the adsorption process of CR onto ZT-MOF@Ag@C. The thermodynamic studies revealed that the adsorption of CR on the ZT-MOF@Ag@C was spontaneous and exothermic. The as-fabricated ZT-MOF@Ag@C was observed to be stable after sixth adsorption-desorption cycles. ZT-MOF@Ag@C composite exhibited excellent potential for the treatment of CR dye from the aqueous solution. The point of zero charge, BET, XRD, XPS, SEM, and FTIR analyses confirmed that the adsorption of CR onto ZT-MOF@Ag@C nanocomposite is majorly dominated by the following mechanisms: π-π interaction, pore adsorption, electrostatic interaction, and hydrogen bonding. The biochar-derived adsorbent's performance was significantly improved through modification, thereby suggesting an effective strategy for boosting the sorbent activity.

Synchrotron radiation study on Thai reddish glass

It is well-known that red glass has been used as a decorative glass in Thailand for hundred years. Pieces of reddish decorative glasses (Ancient Burmese Glass: ABG, Ancient Thai Glass: ATG, and Modern Imported Glass: MIG) have been collected from different areas in Thailand. The elemental composition and morphology of these samples have been examined using scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS) and proton-induced X-ray emission spectroscopy (PIXE). The binding components have been analyzed using infrared spectroscopy based on synchrotron radiation (SR IR). PIXE results indicate a presence of trace elements which is beyond the limit of detection of EDS. It has been found that ABG and MIG are soda-silicate glass, while ATG is lead-based glass. The red coloration in ABG, ATG, and MIG is affected by the contents of Cu, Cd, and Se. It is also found that ABG and MIG have been produced using crucible vessel and glass-making furnace, respectively, while ATG has been produced using either crucible vessel or glass-making furnace. With the high brightness of the synchrotron source, SR IR can analyze the sample with a high spatial resolution of 20 × 20 µm2. SR IR results confirm the presence of inorganic and organic functional groups in glass samples which exhibit distinctive peaks for different types of glass.

Influence of Starch on the Structure-Properties Relationship in Polyethylene Glycol/Polycaprolactone Diol Polyurethanes.

Improvements in the antithrombogenicity activity of biomaterials for cardiovascular applications are necessary to meet the demand for vascular grafts in the world. Zwitterionic compounds tend to be used due to their anti-fouling properties, which reduce platelet adhesions and protein absorptions. Therefore, in this research, potato starch (AL-N) and zwitterionic starch (AL-Z) (obtained by Williamson etherification) were included as fillers in polyurethane (PU) matrices from polycaprolactone diol (PCL), polyethylene glycol (PEG), pentaerythritol (PE) and isophorone diisocyanate (IPDI) in order to study their effect in terms of their physicochemical, mechanical and thermal properties. We conducted our evaluation using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), contact angle analysis, swelling behavior, thermogravimetric analysis (TGA), tensile/strain analysis, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS), dynamic mechanic analysis (DMA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The results showed that AL-N and AL-Z modified these properties, where AL-N improved tensile strength, and AL-Z increased the hydrophilicity of polyurethanes matrices; additionally, AL-N had interactions with the soft segments, and AL-Z had interactions with the hard segments. Finally, both fillers reduced the degree of crystallinity and did not affect the thermal stability of polyurethanes.

Effects of Induction-Furnace Slag on Strength Properties of Self-Compacting Concrete

Abstract Indiscriminate waste disposal poses a severe environmental challenge globally. Recycling of industrial wastes for concrete production is currently the utmost effective way of managing wastes for a cleaner environment and sustainable products. This study investigates the strength characteristics of self-compacting concrete (SCC) containing induction furnace slag (IFS) as a supplementary cementitious material (SCM). The materials utilized include 42.5R Portland cement, induction furnace slag as an SCM ranging from 0 to 50 % by cement weight at 10 % interval, river sand, granite, water and superplasticizer. The fresh properties were tested for filling ability, passing ability and segregation resistance, the strength characteristics measured include compressive strength, splitting tensile strength, flexural strength and Schmidt/rebound number. The oxide compositions and microstructural analysis of SCC were investigated using x-ray fluorescence analyser (XRF) and scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy (SEM-EDS), respectively. Empirical correlations were statistically analyzed using MS-Excel tool. The filling ability characteristic was determined via both the slump flow test and the T50cm slump flow time test. Moreover, the passing ability characteristic was determined using L-Box test. The segregation resistance characteristic was determined using V-funnel at T5minutes test. The results of the fresh properties showed a reduction in the slump flow with increasing IFS content. On the other hand, the T50cm slump flow increased with increasing IFS content. Furthermore, the L-Box decreased with higher IFS content. On the contrary, the V-funnel at T5minutes increased considerably with greater IFS content. The strength test results revealed that the strength properties increased to 20 % IFS, with a value of 66.79 N/mm2 compressive strength at 56 days, giving a rise of 12.61 % over the control. The SCC microstructural examinations revealed the amorphous and better interface structures with increasing IFS content in the mix. The empirical correlations revealed that linear relationships exist among the measured responses (fresh and strength properties). Ultimately, IFS could be utilized as a sustainable material in producing self-compacting concrete.

Efficient Adsorption of Deoxynivalenol by Porous Carbon Prepared from Soybean Dreg.

A novel porous carbon adsorbent for the removal of deoxynivalenol was prepared from soybean dreg (SD). The new material was characterized by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) analysis, N2 adsorption/desorption measurement techniques, X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The specific surface area of the SDB-6-KOH was found to be 3655.95 m2 g−1, the pore volume was 1.936 cm3 g−1 and the average pore size was 2.125 nm. The high specific surface area and effective functional groups of the carbon material promoted the adsorption of deoxynivalenol. By comparing the adsorption effect of SDB-6-X prepared with different activators (X: KOH, K2CO3, KHCO3), SDB-6-KOH had the highest adsorption capacity. The maximum adsorption capacity of SDB-6-KOH to deoxynivalenol was 52.9877 µg mg−1, and the removal efficiency reached 88.31% at 318 K. The adsorption kinetic and isotherm data were suitable for pseudo-second-order and Langmuir equations, and the results of this study show that the novel carbon material has excellent adsorptive ability and, thus, offers effective practical application potential for the removal of deoxynivalenol.

Efficient Removal of Methylene Blue from Aqueous Solutions Using a High Specific Surface Area Porous Carbon Derived from Soybean Dreg.

Porous carbon material with high specific surface area was prepared from soybean dreg by a simple and effective two-step method (high temperature pyrolysis and activation). The structural characteristics of the synthesized carbon were evaluated by Brunauer–Emmett–Teller (BET), N2 adsorption/desorption measurements/techniques, an elemental analyzer (EA), scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), an X-ray diffractometer (XRD), Raman spectroscopy (Raman), a Fourier transform infrared spectrometer (FTIR), and X-ray photoelectron spectroscopy (XPS). The specific surface area of SDB-6-K was 2786 m2 g−1, the pore volume was 2.316 cm3 g−1, and the average pore size was 3.326 nm. The high specific surface area and effective functional groups of carbon material promoted the adsorption of methylene blue. The maximum adsorption capacity of SDB-6-K to methylene blue was 2636 mg g−1 at 318 K. The adsorption kinetic and isotherm data were most suitable for pseudo-second-order and Langmuir equations. The results showed that the adsorbent had excellent adsorptive ability and had good practical application potential in the field of dye wastewater treatment in the future.

Photo-catalytic oxidation for pyridine in circumneutral aqueous solution by magnetic Fe-Cu materials activated H2O2

Magnetic Fe-Cu materials were prepared by the sol-gel method and characterized by X-ray Diffraction (XRD), Brunauer–Emmett–Teller (BET), Scanning Electron Microscopy equipped with Energy-Dispersive X-ray spectroscopy (SEM-EDS) and Vibrating Sample Magnetometer (VSM). These materials were applied for the removal of pyridine under the ultraviolet (UV) irradiation in the Fenton-like system. The influences of different parameters, such as the molar ratio of Fe and Cu, catalyst dosages, H2O2 dosages, initial pH value and initial pyridine concentration have been investigated. Analysis of variance (ANOVA) was applied to analyze the impacts of the key factors on the removal efficiency of TOC. The mechanism of the UV/H2O2/M-40% system was explored. The co-doped Fe-Cu catalyst showed high activity, good stability and easy recovery for the degradation of pyridine when the M-40% dosage was 0.90gL−1, H2O2 dosage was 832.50mgL−1, initial pH value was 7 and initial pyridine concentration was 100.00mgL−1. The degradation efficiency of pyridine was more than 99% within 30min and the removal efficiency of TOC was 97.36±1.10% within 50min. Therefore, the catalyst M-40% was a potential wastewater treatment material that could widen the action range of pH values, facilitating recycling and reuse.

Competitive Surface Colonization of Antibacterial and Bioactive Materials Doped with Strontium and/or Silver Ions.

Nowadays, there is a large amount of research aimed at improving the multifunctional behavior of the biomaterials for bone contact, including the concomitant ability to induce apatite formation (bioactivity), fast and effective osteoblasts colonization, and antibacterial activity. The aim of this study is to develop antibacterial and bioactive surfaces (Ti6Al4V alloy and a silica-based bioactive glass) by chemical doping with strontium and/or silver ions. The surfaces were characterized by Scanning Electron Microscopy equipped with Energy Dispersive X ray Spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM). To better focus on the cells–bacteria competition for the implant surface, in addition to the standard assays for the evaluation of the bacteria adhesion (ISO22196) and for single-cell cultures or biofilm formation, an innovative set of co-cultures of cells and bacteria is here proposed to simulate a competitive surface colonization. The results suggest that all the bioactive tested materials were cytocompatible toward the bone progenitor cells representative for the self-healing process, and that the doped ones were effective in reducing the surface colonization from a pathogenic drug-resistant strain of Staphylococcus aureus. The co-cultures experiments demonstrated that the doped surfaces were able to protect the adhered osteoblasts from the bacteria colonization as well as prevent the infection prior to the surface colonization by the osteoblasts.

Synthesis of Pure and High Surface Area Sodalite Catalyst from Waste Industrial Brine and Coal Fly Ash for Conversion of Waste Cooking Oil (WCO) to Biodiesel

The ravaging environmental menace of coal utilization in power generation and high cost of biodiesel production had recently resulted to global energy discourse. Non-waste-derived heterogeneous catalysts prepared from waste materials could reduce production cost of biodiesel and thus make it economical and environmentally sustainable. In this preliminary study, coal fly ash and industrial waste brine of South African origin were beneficiated for synthesis of waste-derived solid Hydroxy Sodalite (HSOD) catalyst. Non-waste-derived catalysts are not economical and environmentally sustainable. However, hydrothermal synthesis technique was employed to synthesize the catalysts used to produce biodiesel in a batch reactor. The physicochemical properties of the catalysts were studied using Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), Scanning electron microscopy equipped with Energy-dispersive X-ray spectroscopy (SEM-EDS). Textural property of the catalyst was obtained via nitrogen physisorption at 77 K. The catalyst was tested for producing biodiesel from waste cooking oil using these conditions: methanol-to-waste cooking oil ratio of 15:1, 3 wt % of catalysts, and agitation speed of 300-500 rpm, 8 h reaction time and temperature of 60 o C. The biodiesel yield for waste-derived catalyst and non-waste-derived catalyst were 89.4 and 85.0 % respectively, at a maximum waste cooking oil conversion of 97.0 %. Results of the BET analysis reveal that the surface areas of waste-derived and non-waste derived catalysts were 33.05 m 2 g -1 and 0.1645 m 2 g -1 , respectively.

Wear stress mitigation and structural characteristics of highly performing zinc-based induced ZrO2/ZrN composite alloy coating on mild steel

The challenge of residual stress as a result of wear deformation and thermal instability is the motivation behind this study. Nanosized ZrO2/ZrN particles were dispersed into zinc-rich electrolyte using dual anode electrolytic co-deposition (DAECD) route at constant time of deposition and applied current density. The hardness and wear behavior of the coatings were investigated using diamond base microhardness tester and MTR-300 abrasive test rig respectively. The structural properties of the coatings were systematically characterized by X-ray diffractometer (XRD), scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDS), atomic force microscopy, and metallurgical optical microscopy. The stability of the coatings was examined by isothermal furnace at 400 °C. From the results, it is observed that a good adhere coating with significant improvement in mechanical performance was attained. The hardness characteristic value increases from 34 HVN to 172.4 HVN for Zn-ZrO2-ZrN alloy. The plastic deformation was reduced from 0.2 g/min of the as-received sample to 0.0059 g/min for Zn-ZrO2-ZrN matrix. Hence, this establishes that the stability in the coated sample against the working substrate is attributed to the formation of coherent, uniform structural properties, and good strengthening effect from the multifaceted composite materials.

Epitaxial lateral overgrowth of GaxIn1 − xP toward direct GaxIn1 − xP/Si heterojunction

The growth of GaInP by hydride vapor phase epitaxy (HVPE) was studied on planar GaAs, patterned GaAs for epitaxial lateral overgrowth (ELOG), and InP/Si seed templates for corrugated epitaxial lateral overgrowth (CELOG). First results on the growth of direct GaInP/Si heterojunction by CELOG is presented. The properties of GaxIn(1 − x)P layer and their dependence on the process parameters were investigated by X‐ray diffraction, including reciprocal lattice mapping (XRD‐RLM), scanning electron microscopy equipped with energy‐dispersive X‐ray spectroscopy (SEM‐EDS), photoluminescence (PL), and Raman spectroscopy. The fluctuation of Ga composition in the GaxIn(1 − x)P layer was observed on planar substrate, and the strain caused by the composition variation is retained until relaxation occurs. Fully relaxed GaInP layers were obtained by ELOG and CELOG. Raman spectroscopy reveals that there is a certain amount of ordering in all of the layers except those grown at high temperatures. Orientation dependent Ga incorporation in the CELOG, but not in the ELOG GaxIn(1 − x)P layer, and Si incorporation in the vicinity of direct GaxIn(1 − x)P/Si heterojunction from CELOG are observed in the SEM‐EDS analyses. The high optical quality of direct GaInP/Si heterojunction was observed by cross‐sectional micro‐PL mapping and the defect reduction effect of CELOG was revealed by high PL intensity in GaInP above Si.

Seed Germination and Growth of Cucumber (Cucumis sativus): Effect of Nano-Crystalline Sulfur

<p>The present paper is focused on green synthesis of high purity sulfur nanoparticles (SNPs) and its effect on seed germination and seedling growth of cucumber (<em>Cucumis sativus</em>). Synthesized SNPs were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDS). The crystalline size of synthesized SNPs as calculated by Scherer equation was 40 nm. SEM analysis of the SNPs is in spherical shape and with a diameter size between 5-80 nm. In the present study, different concentrations of SNPs were used for the treatment of cucumber seeds to study the effect on bioavailability of seed germination and seedling growth of cucumber. The results of this experiment showed that an increase in concentrations of SNPs had significantly increased seed germination and seedling growth of cucumber.</p>

In Vivo Evaluation of Bulk Metallic Glasses for Osteosynthesis Devices.

Bulk metallic glasses (BMGs) show higher strength and lower Young’s modulus than Ti-6Al-4V alloy and SUS 316L stainless steel. This study aimed to perform in vivo evaluations of Zr65Al7.5Ni10Cu17.5 BMGs for osteosynthesis devices. In the study for intramedullary implants, osteotomies of the femoral bones were performed in male Wistar rats and were stabilized with Zr65Al7.5Ni10Cu17.5 BMGs, Ti-6Al-4V alloy, or 316L stainless steel intramedullary nails for 12 weeks. In the study for bone surface implants, Zr65Al7.5Ni10Cu17.5 BMGs ribbons were implanted on the femur surface for 6 weeks. Local effects on the surrounding soft tissues of the implanted BMGs were assessed by histological observation. Implanted materials’ surfaces were examined using scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS). In the study for intramedullary implants, bone healing after osteotomy was assessed by peripheral quantitative computed tomography (QCT) and mechanical tests. Histological observation showed no findings of the biological effects. SEM-EDS showed no noticeable change on the surface of BMGs, while Ca and P deposition was seen on the Ti-6Al-4V alloy surface, and irregularities were seen on the 316L stainless steel surface. Mechanical test and peripheral QCT showed that, although there was no significant difference, bone healing of BMGs was more than that of Ti-6Al-4V alloy. The results indicated that Zr-based BMGs can lead to bone healing equal to or greater than Ti-6Al-4V alloy. Zr-based BMGs exhibited the advantage of less bone bonding and easier implant removal compared with Ti-6Al-4V alloy. In conclusion, Zr-based BMGs are promising for osteosynthesis devices that are eventually removed.

Bioflotation: Bacteria-Mineral Interaction for Eco-friendly and Sustainable Mineral Processing

In the current study, the action of two bacteria capable of producing biosurfactants and oxidizing iron (Fe) and sulfur (S), namely Bacillus pumilus SKC-2 and Alicyclobacillus ferrooxydans SKC/SAA-2, was investigated with respect to their ability in possessing dual-function as either bio-collector or depressant for the development of sulfide bioflotation processes. Both bacterial strains were able to produce high amounts of biosurfactants interacted with pyrite that had an important role in their adhesion on the surface of pyrite as well as the change of pyrite surface properties. Over the course of the experiments, the pH of the solutions gradually decreased to ∼3, indicating the active oxidation of pyrite minerals by bacteria. The growth of both bacterial strains resulted in the generation of biosurfactants as represented by the decrease of the surface tension of the solutions and the increase of the contact angle of the pyrite surfaces as a function of time. However, the contact angle of pyrite surfaces gradually decreased after 5 days of incubation until the experiments terminated on 30 days. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS) and Fourier transform Infrared (FTIR) analyses also confirmed the role of both bacterial strains in changing the pyrite surface properties to be more hydrophobic or more hydrophilic depending on the time of incubation. These results indicate that the changes of pyrite surface properties are clearly as the results of bacterial action, likely serving as both bio-collector or bio-frother and depressant that would be very applicable for flotation processes. These results increase our knowledge on the interactions in pyrite-bacteria complexes and could potentially be a very useful result with real exploitable value for those working on sulfide bioflotation processes.

A chrome coating from a trivalent chromium bath containing extremely low concentration of Cr<SUP align="right">3+</SUP> ions

In this study, the effects of saccharine on physical and chemical properties of Cr electrodeposition were investigated using electrochemical methods (linear voltammetry and impedance) and surface analysis methods [scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDS)]. According to voltammetric and EIS measurement results, saccharine shifted Eonset to the negative area, which hinder the evolution of H2 gas and decrease the charge transfer of Cr coating, which increase the efficiency of Cr coating. According to the SEM results, it was found that saccharine increased the number of cracks on the surface. The most important result of this study is that saccharine makes Cr coating possible in the extremely low concentration of Cr3+ ion in a trivalent Cr bath.

Effect of shape and thickness of asbestos bundles and fibres on EDS microanalysis: A Monte Carlo simulation

Quantitative microanalysis of tiny asbestos mineral fibres by scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDS) still represents a complex analytical issue. This complexity arises from the variable fibre shape and small thickness (< 5 μm) compared with the penetration of the incident electron beam. Here, we present the results of Monte Carlo simulations of chrysotile, crocidolite and amosite fibres (and bundles of fibres) of circular and square section and thicknesses from 0.1 μm to 10 μm, to investigate the effect of shape and thickness on SEM-EDS microanalysis. The influence of shape and thickness on the simulated spectrum was investigated for electron beam energies of 5, 15 and 25 keV, respectively. A strong influence of the asbestos bundles and fibres shape and thickness on the detected EDS X-ray intensity was observed. The X-ray intensity trends as a function of fibre thickness showed a non-linear dependence for all the elements and minerals. In general, the X-ray intensities showed a considerable reduction for thicknesses below about 5 μm at 5 keV, 2 μm at 15 keV, and 5 μm at 25 keV. Correction parameters, k-ratios, for the asbestos fibre thickness effect, are reported.

Magnetic properties, microstructure and mineralogical phases of technogenic magnetic particles (TMPs) in urban soils: Their source identification and environmental implications

Magnetic measurement is an effective method to determine spatial distribution and the degree of heavy metal pollution and to identify various anthropogenic sources of heavy metals. The objectives of this investigation are to characterize the magnetic properties, microstructure and mineralogical phases of technogenic magnetic particles (TMPs) in urban soils and to discuss their potential environmental implications. The TMPs are separated from the urban topsoils of Luoyang city, China. The magnetic properties, morphology, and mineral phase of TMPs are studied using mineral magnetic measurement, scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM/EDS), X-ray diffraction, and synchrotron–radiation-based microprobe. The content of TMPs in urban topsoils ranges from 0.05 to 1.95% (on average 0.32%). The magnetic susceptibility of TMPs ranges from 4559×10−8 to 23,661×10−8m3kg−1 (on average 13,637×10−8m3kg−1). Thermomagnetic and bulk X-ray diffraction analyses indicate that main magnetic minerals of TMPs are magnetite (Fe3O4) and hematite (α-Fe2O3). The morphology of TMPs observed by SEM includes three shape types: spherule, irregular-shaped, and aggregate particles. The size of spherical TMPs ranges from 30 to about 200μm, with the largest percentage of 30–50μm. Synchrotron–radiation-based microprobe (μ-XRF and μ-XRD) indicates that TMPs are enriched with heavy metals Pb, Cd, Zn, Cu, and Cr, which are incorporated into lattice or adsorbed on the surface of magnetite/hematite. The content of TMPs significantly relates with the Tomlinson Pollution Load Index (PLI) (R2=0.467), suggesting that it can be used as proxy indicator of degree of heavy metal contamination in urban soils. The magnetic properties, microstructure and mineralogical phases of TMPs can serve as the identification of pollution sources in urban soils.

Assessment of Surface Properties of Silica-Bacterial Cell Complex: A Potential Application for Silicate Bioflotation Processes

The objective of the present work was to assess the surface properties of silica-cell complexes formed by Bacillus pumilus strain SKC-2 for bioflotation purposes. This bacterial strain was employed in this study because it is a Gram-positive, mixotrophic bacterium whose metal binding capacity extends to many different metals and circumstances as well as a biosurfactant producer. The strain was found to promote the formation of silica-cell complexes due to the generation of surface-active agents (i.e., extracellular polymeric substrances (EPS)) as represented by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS) observation. Surface properties of the complexes was assessed by water contact angle and surface tension measurements, demonstrating that bacterial cells reduced the surface tension of the solutions and increased the contact angle of the silica surfaces, representing a larger hydrophobic property. Therefore, the findings of this study provide clear evidence for the potential application of the bacterium Bacillus pumilus strain SKC-2 for silicate bioflotation processes (i.e., as frother and collector).