Scanning Electron Microscopy-energy Dispersive X-ray Spectroscopy Research Articles

Resin-modified glass ionomer enriched with BIOGLASS: Ion-release, bioactivity and antibacterial effect.

Developing dental materials for the prevention of remineralization or demineralization is important for high-risk caries patients. This study aimed to evaluate the physicochemical and microbiological effects of adding 45S5 bioglass to resin-modified glass ionomer cement (RMGIC). Samples belonged to the following groups: GIC: conventional glass ionomer cement (Vitro Fil), RMGIC: resin-modified GIC (Vitro Fil LC), and RMGIC/45S5: RMGIC with 10% (wt%) of 45S5. Changes in pH and release of fluoride, calcium, and phosphorus ions under acidic (pH4) and neutral (pH7) pH conditions were evaluated. Antibacterial activity was verified based on colony-forming units. Material sorption and solubility were analyzed after bacterial exposure. After 28 days, the bioactivity of the materials was evaluated using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Analysis of variance, post hoc Scheffe, and Tukey (α=0.05) tests were employed for statistical analysis. RMGIC/45S5 showed higher alkalization activity, calcium release at pH4 and 7, and sorption than GIC and RMGIC (p < .05). Release of phosphorus and fluoride at pH4 and 7 was higher for GIC than that for RMGIC and RMGIC/45S5 (p < .05). RMGIC/45S5 showed higher values than RMGIC (p < .05). However, antibacterial activity did not differ among the groups. Precipitates of calcium and phosphorus were visualized in RMGIC/45S5 samples via SEM/EDS. These results indicate that the RMGIC/45S5 promotes alkalization and increases the release of calcium, phosphorus, and fluoride ions, resulting in precipitate deposition rich in calcium and phosphorus, thereby being a promising option to improve the bioactivity of RMGIC.

Selective extraction and separation of REEs from NdFeB magnets scrap using co-chlorination and water leaching

An approach of co-chlorination followed by water leaching to achieve the selective extraction of rare earth elements (REEs) from NdFeB magnets scrap (scrap) was studied. Co-chlorination refers to the synergistic effect of direct and indirect chlorination reactions. The feasibility of direct and indirect chlorination was explored from both theoretical and practical standpoints. The transformation between NdCl3 and NdOCl during the chlorination roasting process was discovered by X-ray diffraction (XRD) analysis combined with Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS) as well as chemical analysis. The formation of NdOCl was prevented by regulating FeCl3·6H2O dosage, chlorination temperature and chlorination time, then the negative impact from the hydrolysis of NdOCl was avoided. As a result, the complete chlorination of REEs was successfully achieved by using co-chlorination and water leaching. The results showed that 96.51% REEs and 64.29% Co can be synchronously extracted into the leaching solution under appropriate conditions. After the separation of REEs and iron, 92 wt% iron oxide was obtained. This work offers an effective method for recovering REEs from NdFeB magnets scrap.

Physical Properties of Fast-Growing Wood-Polymer Nano Composite Synthesized through TiO2 Nanoparticle Impregnation.

Mangium (Acacia mangium Willd.) is a fast-growing wood that is widely grown in Indonesia. The impregnation method is needed to improve the qualities of the wood. In this study, TiO2 nanoparticle (79.17 nm) was produced using the hydrothermal method. The purpose of this study was to analyze the effect of TiO2 nanoparticle impregnation on the density and dimensional stability of mangium and the effectiveness of the presence of TiO2 nanoparticle in wood in degrading pollutants. The mangium samples (2 cm × 2 cm × 2 cm) were placed inside impregnation tube. The impregnation solutions included water (untreated), 1% TiO2 nanoparticle, and 5% TiO2 nanoparticles. The samples were analyzed for density, weight percent gain (WPG) dan bulking effect (BE). Samples were also analyzed by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). TiO2 nanoparticle resulted in an increase in density, WPG, and BE-treated mangium. Based on XRD and FTIR results, TiO2 nanoparticle was successfully impregnated into mangium wood. Scanning electron microscopy–energy-dispersive X-ray spectroscopy analysis indicated that TiO2 nanoparticle covered the surface of the wood cells. The TiO2-impregnated mangium wood has a higher photocatalyst activity than untreated, indicating better protection from UV radiation and pollutants.

Comprehensive Analysis of Two H13-Type Starting Materials Used for Laser Cladding and Aerosol Particles Formed in This Process.

Laser cladding with H13 steel powders was performed and the related material transformations were studied for the particles emitted during this process. Fractions of various sizes of the aerosol particles formed during the laser cladding were collected on a cascade impactor, while the electromobility and the aerodynamic size of the particles were measured using a scanning mobility particle spectrometer and an aerodynamic particle sizer, respectively. The aerosol particles deposited onto the impactor plates were analyzed using scanning electron microscopy–energy-dispersive X-ray spectroscopy, as well as total-reflection X-ray fluorescence and X-ray absorption near-edge structure spectroscopy. Both the concentration and mean oxidation state of the major components were correlated with the aerosol particle size. The ultrafine aerosol particles (with a diameter less than about 100 nm) were predominantly oxidized and formed as the result of an evaporation–oxidation–condensation process sequence. The larger particles (>200 nm in geometric diameter) were primarily the residues of the original metal powder and exhibited a composition change as compared to the as-received metal powder. Correlations between the changes in the concentration ratio of the components were detected and explained.

Physico-chemical characterization of detrital sillimanite and garnet: Insights into REE elements, crystal structure and morphology

The Varkala–Kovalam coastal stretch of Southern Kerala, India, is enriched with economically significant heavy mineral deposits. In the present study, two such minerals like sillimanite, and garnet were recovered from the beach sands and subjected to detailed characterization studies related to their crystal structure, chemical composition, surface chemistry, and surface morphological changes. Advanced characterization studies involve Raman spectroscopy, X-ray photoelectron spectroscopy, ultraviolet–visible–near infrared spectroscopy, energy dispersive X-ray fluorescence, high resolution inductively coupled plasma mass spectrometry, and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). The Raman spectra strictly discriminate sillimanite from other A12SiO5 polymorphs and almandine from other silicate garnets. The average total rare earth elements present in sillimanite is 222 ppm and garnet is 1094 ppm with a maximum for Ce. The surface morphological changes induced by solution activity of chemicals and mechanical impacts during sediment movement and deposition were easily analyzed by SEM images. The study provides a vivid dataset of physico-chemical characteristics of these minerals, which could facilitate determining their grade and industrial applications.

Construction of a Stimuli-Responsive DNAzyme-Braked DNA Nanomachine for the Amplified Imaging of miRNAs in Living Cells and Mice

Construction of a Stimuli-Responsive DNAzyme-Braked DNA Nanomachine for the Amplified Imaging of miRNAs in Living Cells and Mice

Micro‐Raman spectroscopy and complementary techniques applied for the study of copper and iron wastes from Motya (Italy)

AbstractThis work is the first archaeometric investigation on copper and iron wastes from the Phoenician site of Motya (Sicily, Italy), dating back to the 8th to the 4th century BC. The samples were analyzed through micro‐Raman Spectroscopy (μ‐RS), Optical Microscopy (OM), Scanning Electron Microscope‐Energy‐Dispersive X‐ray Spectroscopy (SEM‐EDS), High‐Resolution Field Emission Scanning Electron Microscopy (HR‐FESEM), and Electron Micro‐Probe Analysis (EMPA). Micro‐Raman techinique permitted to identify both primary phases, for example, calchopyrite, and secondary products such as cuprite and copper thrihydroxychlorides in the Cu‐slags and goethite in the Fe‐slags. SEM and HR‐FESEM imaging showed the occurrence of inhomogeneous microstructures in the Cu‐ and Fe‐slags due to elements segregation, solidification, and corrosion. EMPA data revealed that the archaeometallurgical wastes from Motya can be differentiated on the basis of their chemical compositions. These preliminary results showed different typologies of by‐products, such as base metals speiss, copper slags from smelting sulfide ore with matte, and iron smelting and smithing slags, suggesting different stages of copper and iron productions.

Sulfate resistance of ultrahigh-performance concrete with recycled fine aggregate

The effect of sulfate attack (SA) on the strength of ultrahigh-performance concrete (UHPC) made with different replacements (0%, 50% and 100% by weight) of natural fine aggregate with recycled fine aggregate (RFA) was investigated. The UHPC samples were soaked in 10% sodium sulfate solution for 0–180 days (SA duration). The sulfate ion concentration, flexural strength and compressive strength of the UHPCs were investigated. The microstructure of the UHPCs before and after SA was analysed using a multi-technique approach (analysis of interfacial transition zones (ITZs), X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray spectroscopy and mercury intrusion porosimetry). The results showed that, with an increase in SA duration, the compressive strength of the UHPC made with RFA increased. The generated gypsum and ettringite refined the microstructure by converting harmful pores (&gt;20 nm) into harmless pores (&lt;20 nm) in the UHPC matrix. For the same SA duration, the sulfate ion concentration of UHPC increased with an increase in RFA content due to more ITZs, pores and microcracks introduced by the RFA. Strength development models for UHPC with different RFA contents under SA were developed.

Strength development and microstructure of sustainable geopolymers made from alkali-activated ground granulated blast-furnace slag, calcium carbide residue, and red mud

Red mud (RM) and calcium carbide residue (CCR) are waste generated from alumina refining and acetylene gas producing, respectively. This study utilized alkali-activated ground granulated blast-furnace slag (GGBS) and wet-basis CCR stabilized RM to prepare geopolymers material. The alkali activator solution was composed of CCR supernatant, sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). CCR supernatant was used to reduce the amount of strong alkali. The effects of alkali activator on chemical composition and microstructure of geopolymers were studied by X-ray diffraction (XRD), thermogravimetric-derivative thermogravimetric (TG-DTG) analysis, and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The results show that the utilization of alkali activator improved the compressive strength and especially significantly improved the flexural strength of geopolymers. The strength was negatively correlated with the RM content: the geopolymers containing 30 % RM achieved a maximum 28-day compressive and flexural strength value of 20.3 MPa and 4.3 MPa, respectively. The microstructural analysis revealed that the strength increased due to the formation of calcium aluminate hydrates (C-A-H) and calcium silicate hydrates (CSH). The toxic heavy metals (Cr, Ni, Cu, Pb, Sb, and Zn) from RM formed some complex compounds and were combined in the geopolymers. The 28-day leaching experiment showed that the toxic heavy metals levels were below the test limits. In summary, this study confirmed the safety and feasibility of preparing RM-GGBS-CCR based geopolymers via alkali-activated method.

Preparation, characterization and photocatalytic studies of LaAl0.5Fe0.5O3, LaAl0.5Cr0.5O3 and LaCr0.5Fe0.5O3

Organic dye contaminants which are frequently detected in water bodies have attracted significant attention as they are mostly non-biodegradable. These contaminants pose severe environmental and health risks. In the present work, perovskites of compositions LaAl0.5Fe0.5O3, LaAl0.5Cr0.5O3, LaCr0.5Fe0.5O3 (here after LAFO, LACO and LCFO respectively) were prepared by ethylene glycol assisted gel burning method. The as prepared materials were subjected to powder X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy-selected area electron diffraction (TEM-SAED), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), Raman, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) techniques for characterization. Rietveld refinement was carried for all the compositions and deduced the unit cell parameters. Bandgap energy was obtained for all the three perovskites from their DRS profiles. The FT-IR and Raman spectra gave characteristic M-O and O-M-O (M = La, Cr, Fe, Al) vibrational modes. The photocatalytic activity of these compounds was examined against the degradation of methylene blue (MB). The participation of transient species in the degradation of MB, mechanism of photodecomposition and stability of the catalyst were also presented.

Ni/Ni(OH)2-rGO nanocomposites sensor for the detection of long forgotten mycotoxin, xanthomegnin

Xanthomegnin, a known fungal toxin, secondary metabolite, and pigment diffuses from the dermatophytes has gained attention as local virulence factor because of the mutagenicity, toxicity, cytocidal, and immunosuppressive properties. Not only as a dermatophyte in skin related disorders, the production of xanthomegnin is implicated as a powerful diagnostic marker in patients suffering from ocular mycoses. Incidentally also attributed to death in livestock's majorly by exposing themselves to food-borne fungi like Aspergillus and Penicillium. The production of xanthomegnin in dermetophytic species Trichophyton rubrum, found commonly in infected skin and nails. In this study nickel/nickel hydroxide nanoparticles decorated reduced graphene oxide (Ni/Ni(OH)2-rGO) modified glassy carbon electrode has been successfully used for non-enzymatic detection of xanthomegnin. The Ni/Ni(OH)2-rGO composites were synthesized through a simple microwave assisted technique with less harmful reducing agent. The UV-visible spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDS), and electrochemical investigations demonstrated the robust formation of the sensor. The sensor exhibited improved electrochemical properties with enhanced electrochemical active area and excellent electrochemical behavior towards xanthomegnin detection with a limit of detection of 0.12 μM. The selectivity, stability, and analytical recovery studies proved the potential use of the sensor for the detection of xanthomegnin in real samples. Further, the sensor successfully detected xanthomegnin produced by the Trichophyton rubrum, the most common superficial fungus, accounting for at least 60% of all superficial fungal infections in humans. Validation studies showed satisfiable and quantifiable amount of xanthomegnin in comparison with common bench mark UV-Vis studies meant for fungal mycotoxin detection.

A novel process for recovering aluminum and silicon from fly ash in cryolite molten salt

The recovery and utilization of by-product coal fly ash (CFA) in high-value-added thermal power plants is of great significance. This research focused on producing high-value-added Al–Si master alloy by aluminothermic reduction with coal fly ash as the raw material. The effects of reduction time and reducing agent amount on thermal reduction products were investigated using the single factor method. X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) results showed that Al, Si, and a small amount of Fe were the main components of the alloy. With an increase in reaction time, the mass fraction of Si in the product increased from 4.41% to 9.93%. Besides, the molten salt after thermal reduction was recovered by the electrochemical reduction process. The results showed that a longer electrolysis time is more conducive to improving the recovery of Si and Al. The results of cyclic voltammetry and electrodeposition showed that Si would be reduced in a multi-step process. Combined with thermal reduction and electrochemical secondary recovery process, the comprehensive recovery of Al and Si in fly ash could reach 87.33% and 84.02%, respectively.

A novel and greener sequential column leaching approach for the treatment of two different Greek laterites

Τhe present study investigates, from an environmental protection viewpoint, the efficiency of sequential column leaching of two different Greek laterites, i.e. a limonitic ore from central and a saprolitic ore from northern Greece. First, the most refractory limonitic laterite is leached in the first column for 15 days and the obtained pregnant leach solution (PLS) is further used for the leaching of the easier to treat saprolitic ore in the second column, thus achieving a significantly reduced acid consumption. The main parameters affecting the process efficiency, i.e. acid molarity (1.5 or 3 mol/L H2SO4) and addition of sodium sulfite (Na2SO3) in the leaching solution were studied. The extraction of Ni, Co, Fe, Al, Mg, Mn and Ca was determined by Atomic Absorption Spectroscopy (AAS), while the characterization of the ores and final residues was carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA/DTA), and Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM-EDS) analysis. The results confirm the efficiency of the proposed green approach, which with the use of leaching solution containing 1.5 mol/L H2SO4 and 20 g/L Na2SO3 resulted in 73.8 % Ni, 71.6 % Co and 8.4 % Fe extraction after a short period of time (33 days), while the acid consumption, which is a serious environmental concern, was very low and did not exceed 300 kg/t ore. Overall, the proposed process not only improves the efficiency of leaching of different types of laterites for the recovery of both Ni and Co but also reduces the environmental impacts due to the significantly lower acid consumption.

A multi-analytical approach for the characterization of materials, manufacturing process and damage mechanisms of wall paintings in Samye Temple, Tibet

This research focuses on the multi-technique characterization and identification of degradation mechanisms of the wall paintings at the Samye Temple in Tibet, which is considered the first built temple of Tibetan Buddhism with an enormous cultural significance to the region. Wall painting general stratigraphy was thoroughly analyzed by Optical Microscopy (OM), Scanning Electron Microscopy – Energy Dispersive X-Ray Spectroscopy (SEM-EDS) and X-ray Powder Diffraction (XRD). Results reveal a clear sequence, from the interior to the surface, consisting on an adobe wall support, a coarse mud plaster, a fine mud plaster, a white ground layer, a surface paint layer, and a coating layer. The identification of natural and/or synthetic pigments and possible re-painted areas was analyzed by polarized light microscope and SEM-EDS, and subsequently studied using Raman spectroscopy. Results reveal the mineral pigments include red cinnabar (HgS) and red lead (Pb3O4), blue azurite (Cu3(CO3)2(OH)2), green malachite (Cu2CO3(OH)2), yellow orpiment (As2S3), and a gold layer (gold powder). White and black pigments are magnesite (MgCO3) and carbon, respectively. Additionally, the external surface coating varnish found on the top of the paint layer was also analyzed by Transmission Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance mode (FTIR-ATR), Proton Nuclear Magnetic Resonance (H1 NMR), Thermogravimetric analysis (TG), Mass Spectrometry (MS) and SEM-EDX analysis. Results show main components of this coating include acrylates and, possibly, silanes, revealing a recent conservation intervention activity. The hydric expansion/contraction of clay minerals in the adobe support and mud plaster layers and the rigid and impervious acrylate coating layer could have accelerated the deterioration and be the responsible for the development of cracks both at the interface of the different support layer and normal to the wall painting surface, resulting in massive losses. These findings are relevant to better understand the traditional manufacturing process of historic wall paintings in Tibet, which is not fully understood yet, and serve to further conservation activities of this historically rich temple.

Formation of Noble Metal Phases (Pt, Pd, Rh, Ru, Ir, Au, Ag) in the Process of Fractional Crystallization of the CuFeS2 Melt

The quasi-equilibrium directional crystallization of the melt composition (at. %): Cu 24.998, Fe 25.001, S 49.983, with Ag 0.002, Pd 0.003, Ru 0.004, Rh 0.006, and Au, Pt, Ir (each as 0.001) was carried out. The crystallized cylindrical ingot consisted of two primary zones and three secondary zones with different chemical and phase compositions. The compositions of the primary zones corresponded to high-temperature intermediate solid solution (zone I) and liquid enriched in sulfur (zone II). The compositions of the secondary zones corresponded to low-temperature intermediate solid solution and chalcopyrite (zone Ia), the same intermediate solid solution with chalcopyrite and bornite (zone Ib), and again with bornite, chalcocite, and idaite (zone II). We plotted the distribution curves of Fe, Cu, and S along the ingot, calculated the distribution coefficients of the components during directional crystallization, and clearly showed that, from the initial stoichiometric composition CuFeS2, the intermediate solid solution enriched in Fe and depleted in S is crystallized. Based on the data of directional crystallization and thermal analysis, a cross section was constructed in the intermediate solid solution-sulfide melt region of the Cu-Fe-S system. With solubility in the solid Cu-Fe sulfides lying below detection limit of scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM/EDS), noble elements occurred as individual phases of a size more often &lt;10 µm. They were identified as Ag, RuS2, PdS, Au* (an Au based alloy), (Rh, Ir, Ru)3S8, (Rh, Ir)3S8, Rh3S8, and (Cu, Fe)~2(Pt, Rh)1S~5 phases by electron microprobe. Based on ab initio calculations of crystal structure, electronic band structure, and lattice dynamics of idealized laurite RuS2 phase and the idealized Ir3S8, Rh3S8, and Ru3S8 phases, the interpretation of Raman spectrum of the cation-mixed (Ru, Rh, Ir)S2 sulfide was presented for the first time.

Crystallization and pyrolysis of nitric acid pressure leach liquor of limonitic laterite and separation of valuable metals

Based on the advantages of nitric acid pressure process (NAPL) for laterite nickel ores, this study innovatively proposes nitric acid pressure leach liquor crystallization pyrolysis-mixed metal oxides separation process. Firstly, the feasibility and the possible reactions of mixed nitrate pyrolysis were confirmed by thermodynamic analysis. Subsequently, the optimal pyrolysis temperature was experimentally investigated. Then, the pyrolysis process of combined nitrate was thermodynamically analyzed, and the phase composition of mixed metal oxides was determined by X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and Scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS). The Pourbaix diagram shows that using NaOH as leaching agent can selectively separate aluminum from mixed metal oxides, and the variables influencing aluminum's leaching rate are investigated. The experimental results are as follows: the optimal pyrolysis temperature of mixed nitrate crystals is 600 °C; the pyrolysis products are mainly oxides with the formation of NiAl2O4 and MgAl2O4 spinel phases; the aluminum leaching rate is 81.9% under the optimal alkali leaching conditions. The presence of spinel phase is not favorable for aluminum leaching. After leaching, an enriched residue of 15.8% Ni, 1.9% Co and 0.19% Sc was obtained.

Internal Curing Effect of Waste Glass Beads on High-Strength Cement Composites

High-strength concrete (HSC) uses binders and microfillers with ultrafine particles, such as silica fume. The resulting dense internal hydration structure rapidly decreases HSC humidity, causing shrinkage cracks and affecting internal hydration. Herein, the hydration degree inside high-strength cement composites (HSCCs) was examined using waste glass beads (WGBs) as lightweight aggregates (LWAs). Moreover, unreacted hydrate reduction and hydrate formation tendencies were investigated. WGBs with particle sizes within 2.00–6.00 mm were added at ratios of 5%, 10%, and 20% after pre-wetting. The increased number of hydrates inside the specimens were examined under steam curing (80 °C) and room temperature curing (25 °C). The strength decreased as the WGB content increased. Thermogravimetric, X-ray diffraction, and Si nuclear magnetic resonance analyses revealed that the hydration degree of Si inside HSCCs changed when the content of pre-wetted LWAs changed. A visual inspection of the specimen cross-section and scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM–EDS) analysis revealed the moisture trapped inside WGB pores and the hydration tendency. Under steam curing and room temperature curing, the paste contained different amounts of hydrates, depending on WGB content. Moreover, water-absorbed WGBs were continuously desorbed through SEM–EDS, and hydrates were present in WGB pores.

Production of Mesoporous Magnetic Carbon Materials from Oily Sludge by Combining Thermal Activation and Post-Washing.

In this work, the oily sludge (OS) from a local waste oil recycling plant was reused as a precursor for producing porous magnetic carbon composites (CC) by pyrolysis, followed by carbon dioxide activation. Based on the thermogravimetric analysis (TGA) of the OS feedstock, the preparation experiments were performed at 800–900 °C. From the pore analysis of the CC products, it indicated an increasing trend, as the BET surface area greatly increased from about 1.0 to 44.30 m2/g. In addition, the enhancement effect on the pore properties can be consistently obtained from the acid-washed CC products because the existing and new pores were reformed due to the leaching-out of inorganic minerals. It showed an increase from 32.27 to 94.45 m2/g and 44.30 to 94.52 m2/g at 850 and 900 °C, respectively, showing their mesoporous features. These porous and iron-containing features were also observed by the scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). In addition, the adsorption removal of total organic carbon (TOC) in the raw wastewater, by the CC product, showed its high performance (>80%).

Green Synthesis and Antimicrobial Activities of Silver Nanoparticles Using Calotropis gigantea from Ie Seu-Um Geothermal Area, Aceh Province, Indonesia.

Herein, we report our success synthesizing silver nanoparticles (AgNPs) using aqueous extracts from the leaves and flowers of Calotropis gigantea growing in the geothermal manifestation Ie Seu-Um, Aceh Besar, Indonesia. C. gigantea aqueous extract can be used as a bio-reductant for Ag+→Ag0 conversion, obtained by 48h incubation of Ag+, and the extract mixture in a dark condition. UV–Vis characterization showed that the surface plasmon resonance (SPR) peaks of AgNPs-leaf C. gigantea (AgNPs-LCg) and AgNPs-flower C. gigantea (AgNPs-FCg) appeared in the wavelength range of 410–460 nm. Scanning electron microscopy energy-dispersive X-ray spectrometry (SEM-EDS) revealed the agglomeration and spherical shapes of AgNPs-LCg and AgNPs-FCg with diameters ranging from 87.85 to 256.7 nm. Zeta potentials were observed in the range of −41.8 to −25.1 mV. The Kirby-Bauer disc diffusion assay revealed AgNPs-FCg as the most potent antimicrobial agent with inhibition zones of 12.05 ± 0.58, 11.29 ± 0.45, and 9.02 ± 0.10 mm for Escherichia coli, Staphylococcus aureus, and Candida albicans, respectively. In conclusion, aqueous extract from the leaves or flowers of Calotropis gigantea may be used in the green synthesis of AgNPs with broad-spectrum antimicrobial activities.

Designer biochar with enhanced functionality for efficient removal of radioactive cesium and strontium from water

Radioactive elements released into the environment by accidental discharge constitute serious health hazards to humans and other organisms. In this study, three gasified biochars prepared from feedstock mixtures of wood, chicken manure, and food waste, and a KOH-activated biochar (40% food waste + 60% wood biochar (WFWK)) were used to remove cesium (Cs+) and strontium (Sr2+) ions from water. The physicochemical properties of the biochars before and after adsorbing Cs+ and Sr2+ were determined using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, extended X-Ray absorption fine structure (EXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDX). The WFWK exhibited the highest adsorption capacity for Cs+ (62.7 mg/g) and Sr2+ (43.0 mg/g) among the biochars tested herein. The removal of radioactive 137Cs and 90Sr exceeded 80% and 47%, respectively, in the presence of competing ions like Na+ and Ca2+. The functional groups present in biochar, including –OH, –NH2, and –COOH, facilitated the adsorption of Cs+ and Sr2+. The Cs K-edge EXAFS spectra revealed that a single coordination shell was assigned to the Cs–O bonding at 3.11 Å, corresponding to an outer-sphere complex formed between Cs and the biochar. The designer biochar WFWK may be used as an effective adsorbent to treat radioactive 137Cs- and 90Sr-contaminated water generated during the operation of nuclear power plants and/or unintentional release, owing to the enrichment effect of the functional groups in biochar via alkaline activation.