Thermogravimetry And Differential Thermal Analysis Research Articles

(Invited) Multiscale Electrochemical Analysis of Sol-Gel Films Modified with Eco-Friendly Corrosion Inhibitors for Active Corrosion Protection of AZ61 Magnesium Alloy

The use of magnesium and its alloys has increased in recent years due to their low weight, high strength, excellent machinability, and high dimensional durability. Therefore, they have found application in communications, automotive and aerospace industries, among others. However, their high negative reduction potentials, low chemical stability, and the unstable native oxide films have limited their use, particularly in applications that require high corrosion resistance.1 -3 The application of sol-gel coatings has shown to be an effective method to overcome this problem. In this context, the aim of this study was to develop sol-gel thin-films doped with ecological corrosion inhibitors for corrosion protection of AZ61 alloy surfaces. The objective was to determine whether these new systems could provide an alternative to the replacement of chromates, surface pre-treatments and chemical conversion coatings that contain conventional corrosion inhibitors, which are currently being questioned for their harmfulness to health and the environment.4 Methyltriethoxysilane (MTEOS) and tetraethylorthosilicate (TEOS) were used as precursors to produce sols, which were then modified with active corrosion protection dopants. Eco-benign corrosion inhibitors, such as L-cysteine (L-Cys), lanthanum (III) acetate hydrate, and lanthanum (III) isopropoxide were incorporated in the sol-gel matrix as dopants. A set of sol-gel coatings was modified with a common dopant, benzotriazole (BTA), for comparison purposes, as it is a well-known effective corrosion inhibitor. However, this chemical compound is known to be carcinogenic and toxic to flora and fauna, and its use is currently being restricted today in compliance with environmental protection regulations.5,6 The resulting sols were processed and deposited on AZ61 substrates by dip-coating technique, producing transparent sol-gel thin-films. The thickness of the films was evaluated by interference of reflection spectra. Their chemical composition was characterized by X-ray fluorescence (XRF), while surface chemical composition and oxidation state of elements present at the outermost surface nanolayers was also analysed by X-ray photoelectron spectroscopy (XPS). The structural and thermal characterization of the doped thin-films were respectively analysed by Fourier transformed infrared spectroscopy (FTIR) and thermogravimetry and differential thermal analysis (TG/DTA).The corrosion protection behaviour of the sol-gel coatings during immersion tests in 0.006 M and 0.6 M NaCl aqueous solutions was studied using a multiscale electrochemical approach. Global electrochemical impedance spectroscopy (EIS) was used for macroscopic scale characterisation. Localised electrochemical impedance spectroscopy (LEIS and LEIM) was used for the characterisation at micro- and sub-microscopic scales using an electrochemical minicell system and a scanning electrochemical workstation.The texture and microstructure of coated samples before and after corrosion tests were observed by optical and scanning electron microscopies (OM and SEM), while topography and coating roughness were analysed by atomic force microscopy (AFM).In terms of corrosion resistance, similar results were obtained with sol-gel thin-films doped with lanthanum acetate or lanthanum isopropoxide. The synthesis method of the acetate-doped gels is much simpler and cheaper, so from a practical standpoint, these sol-gel thin-films could be more interesting. On the other hand, highly satisfactory results were obtained with gels doped with non-toxic L-Cys compared with those doped with BTA. Finally, it is noteworthy that an interesting synergistic effect was observed in the corrosion protection of the AZ61 alloy in sol-gel coatings that were doped with metal-organic inhibitors and loaded with organic inhibitors (L-Cys or BTA).As a concluding remark, this study has provided an effective and environmentally friendly solution for the active corrosion protection of the AZ61 alloy. Sol-gel thin-films doped with eco-friendly corrosion inhibitors have showed promising results in extending the durability of AZ61 alloy while being sustainable. The multiscale electrochemical approach used has provided a comprehensive understanding of the active corrosion protection behaviour and the self-healing properties of sol-gel coatings, which can be extended to other materials and systems. Funding Sources This work has been supported by the Ministry of Science and Innovation (MCINN, Spain) through the Project PID2019-104717RB-I00. References Feliu Jr., S., Maffiotte, C., Samaniego, A., Galván, J.C., Barranco, V. Acta, 56 (12) (2011) 4554-4565 Stojadinović, S., Vasilić, R., Radić-Perić, J., Perić, M. Coat. Technol., 273 (1) (2015), pp. 1-11 Toorani, M., Aliofkhazraei, M., Naderi, R., Golabadi, M., Sabour Rouhaghdam, A. Ind. Eng. Chem., 53, (2017) pp. 213-227 Vaghefinazari, B., Wierzbicka, E., Visser, P., Posner, R., Arrabal, R., Matykina, E., Mohedano, M., Blawert, C., Zheludkevich, M., Lamaka, S. Materials, 15 (23) (2022), art. no. 8676 Albini, M., Letardi, P., Mathys, L., Brambilla, L., Schröter, J., Junier, P., Joseph, E. Corrosion Sci., 143 (2018), pp. 84-92Tan, L., Sun, Y., Li, J., Han, S., Zhou, X., Tang, Y., Zeng, X. Langmuir, 39 (2023), 2579-2588

Production and characterization of single-phase diopside sol–gel powder

In this work, diopside powder was synthesized through the sol–gel method aiming at obtaining single-phase fine particles. Tetraethyl orthosilicate, calcium nitrate tetrahydrate and magnesium chloride hexahydrate were used as sources of cations, in ratios specific to diopside. Wet gel was synthesized by hydrolyzing a homogeneous solution consisting of precursors dissolved in ethanol. Ground gel powder was investigated by differential thermal analysis and thermogravimetry (DTA-TGA) to define details of the subsequent heat treatments. Samples calcined at 600, 650, 700, 800 and 1100 °C for 3 h underwent characterization through Fourier-transform infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy. Diopside was found as the single crystalline phase in the interval 600–1100 °C.

Effect of heat treatment temperature on the morphology and upconversion properties of LaF3:Yb,Er nanoparticles

LaF3:5%Yb3+,0.5%Er3+ upconverting nanoparticles were synthesized with co-precipitation method and heat treated at temperatures 300–600 °C. The morphology of the particles was characterized by high-resolution transmission electron microscopy coupled with energy-dispersive spectrometry and dynamic light scattering. Crystal structure was studied by X-ray diffraction (XRD), and thermal behaviour was investigated by simultaneous thermogravimetry and differential thermal analysis (TG/DTA). Upconversion behaviour was studied in detail by fluorescence spectroscopy, with 980 nm excitation. Particle sizes increased with increasing heat treatment temperature, and samples showed significant aggregation above 500 °C. Hexagonal LaF3 crystal structure was identified for all samples, with increased crystallinity after heat treatment at 400 °C, which was corroborated with TG/DTA results. XRD and energy-dispersive spectrometry results revealed that at higher temperatures new crystal phases formed, as some Yb3+ and Er3+ dopant ions segregated into new nanocrystals, made of, for example, YbOF and YbOOH, which caused a significant decrease in the upconversion emission of the samples. The highest upconversion emission was achieved after heat treatment at 400 °C.

Leucopterin, the white pigment in butterfly wings: structural analysis by PDF fit, FIDEL fit, Rietveld refinement, solid-state NMR and DFT-D.

Leucopterin (C6H5N5O3) is the white pigment in the wings of Pieris brassicae butterflies, and other butterflies; it can also be found in wasps and other insects. Its crystal structure and its tautomeric form in the solid state were hitherto unknown. Leucopterin turned out to be a variable hydrate, with 0.5 to about 0.1 molecules of water per leucopterin molecule. Under ambient conditions, the preferred state is the hemihydrate. Initially, all attempts to grow single crystals suitable for X-ray diffraction were to no avail. Attempts to determine the crystal structure by powder diffraction using the direct-space method failed, because the trials did not include the correct, but rare, space group P2/c. Attempts were made to solve the crystal structure by a global fit to the pair distribution function (PDF-Global-Fit), as described by Prill and co-workers [Schlesinger et al. (2021). J. Appl. Cryst. 54, 776-786]. The approach worked well, but the correct structure was not found, because again the correct space group was not included. Finally, tiny single crystals of the hemihydrate could be obtained, which allowed at least the determination of the crystal symmetry and the positions of the C, N and O atoms. The tautomeric state of the hemihydrate was assessed by multinuclear solid-state NMR spectroscopy. 15N CPMAS spectra showed the presence of one NH2 and three NH groups, and one unprotonated N atom, which agreed with the 1H MAS and 13C CPMAS spectra. Independently, the tautomeric state was investigated by lattice-energy minimizations with dispersion-corrected density functional theory (DFT-D) on 17 different possible tautomers, which also included the prediction of the corresponding 1H, 13C and 15N chemical shifts in the solid. All methods showed the presence of the 2-amino-3,5,8-H tautomer. The DFT-D calculations also confirmed the crystal structure. Heating of the hemihydrate results in a slow release of water between 130 and 250 °C, as shown by differential thermal analysis and thermogravimetry (DTA-TG). Temperature-dependent powder X-ray diffraction (PXRD) showed an irreversible continuous shift of the reflections upon heating, which reveals that leucopterin is a variable hydrate. This observation was also confirmed by PXRD of samples obtained under various synthetic and drying conditions. The crystal structure of a sample with about 0.2 molecules of water per leucopterin was solved by a fit with deviating lattice parameters (FIDEL), as described by Habermehl et al. [Acta Cryst. (2022), B78, 195-213]. A local fit, starting from the structure of the hemihydrate, as well as a global fit, starting from random structures, were performed, followed by Rietveld refinements. Despite dehydration, the space group remains P2/c. In both structures (hemihydrate and variable hydrate), the leucopterin molecules are connected by 2-4 hydrogen bonds into chains, which are connected by further hydrogen bonds to neighbouring chains. The molecular packing is very efficient. The density of leucopterin hemihydrate is as high as 1.909 kg dm-3, which is one of the highest densities for organic compounds consisting of C, H, N and O only. The high density might explain the good light-scattering and opacity properties of the wings of Pieris brassicae and other butterflies.

Studies on fluorination of Fe3O4 (magnetite) by NH4HF2

Fluorination of magnetite (Fe3O4) by NH4HF2 was investigated using simultaneous thermogravimetry and differential thermal analysis (TG-DTA), and observing the morphology and phase changes using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffractometry (XRD). The results indicate that fluorination with the involvement of oxygen begins at room temperature, peaks at 1784ºC, and is completed at 200ºC with the formation of only (NH4)3FeF6. On heating, (NH4)3FeF6 gradually releases NH4F by the formation of NH4FeF4 at 259ºC, then (NH4)0.l8FeF3 at 327ºC, and finally FeF3 with minor FeF2 at 400ºC due to the partial reduction of Fe (III) to Fe (II). At 550ºC, FeF3 is oxidized to FeOF/Fe2O3.

Influence of silicon-dioxide nanoparticles in cementitious mortars: verification using x-ray diffraction, thermal analysis, physical, and mechanical tests

In recent years, nanotechnology has been applied to building materials, such as cementitious composites (e.g., mortar and concrete), to improve their properties. The aim of this study was to analyze the thermal, physical, and mechanical properties of mortars with and without silicon-dioxide (SiO2) nanoparticles. Experiments such as thermogravimetry and differential thermal analysis (TG-DTA), x-ray diffraction (XRD), fresh density, incorporated-air content, bulk density, capillary absorption, capillarity coefficient, flexural tensile strength, and compressive strength on prismatic specimens were performed on mortars and analyzed for different levels of nanosilica (nS). These levels were 1% and 3%, in addition to the reference mortar (0% nS). The TG-DTA curves showed an elevated content of chemically combined water and a lower content of calcium hydroxide (Ca(OH)2) in the 3% nS compositions, while the XRD curves presented a lower content of calcite and portlandite in the same mortar. These results indicate the fixation capacity of lime for the formation of calcium silicate hydrate (C-S-H), which is the primary cause of resistance in cementitious mortars. In addition, it was found that the use of nanosilica contributed to a fresh density increase of approximately 15%, which caused a minimum air-incorporated content decrease of 37% and a minimum bulk density increase of 10%. Higher densities resulted in a minimum water absorption reduction of 36%, owing to fewer pores in the mortars. Therefore, the capillarity coefficient decreased by a minimum of 41%. These nanoparticles also improved the minimum flexural tensile and compressive strengths by 88% and 158%, respectively, when using a 3% nS composition. These results can enable the use of lightweight aggregates in cementitious composites, improving their physical and mechanical characteristics and allowing greater reuse of these materials, including construction waste.

Structure and release properties of pyrethroid/sulfobutyl ether β-cyclodextrin intercalated into layered double hydroxide and layered hydroxide salt.

The aim of this study was to realize the intercalation of the pyrethroid pesticides beta-cypermethrin (BCT) and lambda-cyhalothrin (LCT) into ZnAl-layered double hydroxides (LDH) and NiZn-layered hydroxide salt (LHS). BCT (LCT)/SBECD-LDH and BCT (LCT)/SBECD-LHS hybrids were obtained with the aid of sulfobutyl ether β-cyclodextrin (SBECD) through one step method. The hybrids were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetry and differential thermal analysis (TGA/DTA). The hybrids based on LHS had larger basal spacing than those on LDH. The LDH-hybrids prepared in N-methylpyrrolidone (NMP) had larger basal spacing than those in ethanol. These results were discussed in terms of the matrix structure and solvent properties. The supramolecular structure of the hybrid was reasonably proposed. Furthermore, the release properties of BCT (LCT) from the hybrids were investigated and discussed in two media. The release rate in pH = 5.0 was slower than that in pH = 6.8. The accumulated release amount of pesticide in pH = 5.0 was lower than that in pH = 6.8. LHS-hybrids synthesized in ethanol exhibit a sustainable release property. These depend on the inclusion complexes’ arrangement and release medium. The release kinetic processes could be described by pseudo-second order and parabolic diffusion models. The release behavior can be controlled by adjusting the synthesis conditions and the releasing media. This provides the guidance for the application of SBECD and LDH (LHS) in pesticide formulation.

Synthesis and Characterization of Nanocellulose from Lignocellulosic Agricultural Biomass by Acid Hydrolysis

The present study emphasizes lignocellulosic materials like agricultural biomass such as ragi stalk also known as Finger Millet Stalk (Eleusine coracana), mango wood (Mangifera caesia) and groundnut husk (Arachis hypogaea) were transformed into cellulose by pretreatment with 5% NaOH and 5% NaClO2 solution. In addition, the cellulose obtained was transformed into nanocellulose (NC) using acid hydrolysis, ultrasonication and centrifugation. The X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetry and differential thermal analysis (TGA/DTA) were used to characterize the synthesized nanocellulose. According to the FTIR findings, the chemical structure of cellulose synthesized from these agricultural biomasses was not affected by the synthetic approach, however, the synthetic procedure employed affects the morphology/surface topology of synthesized nanocellulose as confirmed by SEM. XRD studies reveal the crystalline and semi-crystalline nature of the synthesized nanocellulose. TEM monographs illustrate the surface structure and size of the synthesized nanocellulose ranging from 8 to 17 nm. The thermal stability of nanocellulose is revealed by TGA/DTA studies and the obtained nanocellulose shows thermal stability in the range of 240 to 327 ºC.

Organobeidellites for Removal of Anti-Inflammatory Drugs from Aqueous Solutions.

Diclofenac (DC) and ibuprofen (IBU) are widely prescribed non-steroidal anti-inflammatory drugs, the consumption of which has rapidly increased in recent years. The biodegradability of pharmaceuticals is negligible and their removal efficiency by wastewater treatment is very low. Therefore, the beidelitte (BEI) as unique nanomaterial was modified by the following different surfactants: cetylpyridinium (CP), benzalkonium (BA) and tetradecyltrimethylammonium (TD) bromides. Organobeidellites were tested as potential nanosorbents for analgesics. The organobeidellites were characterized using X-ray powder diffraction (XRD), Infrared spectroscopy (IR), Thermogravimetry and differential thermal analysis (TG/DTA) and scanning microscopy (SEM). The equilibrium concentrations of analgesics in solution were determined using UV-VIS spectroscopy. The intercalation of surfactants into BEI structure was confirmed both using XRD analysis due to an increase in basal spacing from 1.53 to 2.01 nm for BEI_BA and IR by decreasing in the intensities of bands related to the adsorbed water. SEM proved successful in the uploading of surfactants by a rougher and eroded organobeidellite surface. TG/DTA evaluated the decrease in dehydration/dehydroxylation temperatures due to higher hydrophobicity. The Sorption experiments demonstrated a sufficient sorption ability for IBU (55–86%) and an excellent ability for DC (over 90%). The maximum adsorption capacity was found for BEI_BA-DC (49.02 mg·g−1). The adsorption according to surfactant type follows the order BEI_BA > BEI_TD > BEI_CP.

Influence of Operational Parameters on Photocatalytic Degradation of Linuron in Aqueous TiO2 Pillared Montmorillonite Suspension

TiO2 pillared clay was prepared by intercalation of titan polyoxocation into interlamelar space of an Algerian montmorillonite and used for the photocatalytic degradation of the linuron herbicide as a target pollutant in aqueous solution. The TiO2 pillared montmorillonite (Mont-TiO2) was characterized by X-ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD), X-Ray fluorescence (XRF), scanning electronic microscopy (SEM), thermogravimetry and differential thermal analysis (TG-DTA), Fourier transformed infra-red (FT-IR), specific area and porosity determinations. This physicochemical characterization pointed to successful TiO2 pillaring of the clay. The prepared material has porous structure and exhibit a good thermal stability as indicated by its surface area after calcination by microwave. The effects of operating parameters such as catalyst loading, initial pH of the solution and the pollutant concentration on the photocatalytic efficiency and COD removal were evaluated. Under initial pH of the solution around seven, pollutant concentration of 10 mg/L and 2.5 g/L of catalyst at room temperature, the degradation efficiency and COD removal of linuron was best then the other operating conditions. It was observed that operational parameters play a major role in the photocatalytic degradation process. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Superior Competitive Adsorption Capacity of Natural Bentonite in the Efficient Removal of Basic Dyes from Aqueous Solutions

AbstractIn this study, natural bentonite has been used as a highly efficient, and low‐cost sorbent for the adsorptive removal of methylene blue (MB), crystal violet (CV), and fuchsine basic (FB) dyes from aqueous solutions. X‐ray fluorescence (XRF), Thermogravimetry and differential thermal analyses (TG‐DTA), X‐ray diffraction (XRD), Scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) analyses for bentonite clay were performed. Results revealed that bentonite is an excellent sorbent for the elimination of these dyes with maximum adsorption capacities of 598.8, 929.7 and 875.2 mg g−1 for MB, CV, and FB, respectively. In addition, thermodynamic results reflected that the adsorption process is a spontaneous, endothermic, and of chemisorption nature. While kinetic studies specified that the adsorption of these dyes is ruled by the film diffusion and pore diffusion mechanism. Moreover, simultaneous removal of these dyes from their binary and ternary mixtures was also examined. A Regeneration study demonstrated that, bentonite can be recycled several times with almost the same efficiency.

Fireproofing wood using borate and vinyl phosphorus compounds and its water resistant treatment using copolymer of dimethyl vinylphosphonate and methyl methacrylate

Vinyl phosphorus compounds such as poly (vinyl phosphonic acid) (PVPA), poly (dimethyl vinyl phosphonate) (PDMVP) impart high flame retardancy to wood comparable to conventional fireproofing wood by combined use of sodium polyborate (SPB) in contrast to their single use. The differential thermal analysis and thermogravimetry (DTA/TG) suggest a synergy effect between SPB and PVPA. The water resistance of the treated wood is improved by copolymerization of dimethyl vinyl phosphonate (DMVP) with methyl methacrylate (MMA) inside the wood after the impregnation of SPB, and the incombustibility of the wood is mostly maintained after leaching tests. The combustion residues of the wood treated with DMVP and MMA after SPB show high compressive strength, and their SEM images suggest that the strength is due to formed charcoal.

Removal of analgesics from aqueous solutions onto montmorillonite KSF

Due to increasing consumption of analgesic drugs associated with their occurrence in wastewater, it is necessary to pay attention to find new accessible types of sorbents for effective drug removal. The objective of this work is the assessment of ability of commercial montmorillonites for the removal of drugs from aqueous solutions since these inexpensive materials exhibit both adsorption and ion exchange properties as well as environmental stability. The commercial montmorillonite KSF, primarily used as acidic catalyst, was used in both unmodified and cetyltrimethylammonium bromide (CTAB) modified form as potential sorbent for three analgesics: paracetamol (PAR), ibuprofen (IBU) and diclofenac (DC) from aqueous solutions. The samples were characterized by X-ray fluorescence (XRFS), X-ray powder diffraction (XRD), simultaneous thermogravimetry and differential thermal analysis (TG/DTA) and high-performance liquid chromatography (HPLC). XRD confirmed the intercalation of CTAB into the montmorillonite structure with the increasing of basal spacing. Thermal analysis also determined the presence of CTAB associated with increasing of the hydrophobicity accompanied by a decrease in dehydration temperature. Also, due to surfactant modification, the temperature of constitution water removal decreased. Adsorption experiments were carried out in a batch mode with different initial concentration of paracetamol, ibuprofen and diclofenac solutions. Montmorillonite samples especially in organically modified form demonstrated sufficient sorption ability of pharmaceuticals from aqueous solutions in the order diclofenac > ibuprofen > paracetamol.

Mineralogical Characterization of Carreaux de Pavement from Northern Spain (Tiebas, Navarre)

Several medieval tiles from Tiebas Castle in Navarre, classified as carreaux de pavement, were mineralogically analyzed. The aim was to add information to the very scarce analytical data available for carreaux de pavement in order to provide a quality primary work, mainly descriptive, in this topic. The characterization techniques applied were: optical microscopy (OM), colorimetry, Fourier transform infrared (FT-IR) spectroscopy, differential thermal analysis and thermogravimetry (DTA-TG), X-ray fluorescence (XRF) spectroscopy, petrographic microscopy (PM), X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS). The tiles comprised three layers: a top glaze with mainly silicon and lead-based compounds; a thin layer of silicoaluminate (very possibly kaolinite) called engobe under it; and the pastes, composed of quartz, hematite, potassium feldspars and calcite. Honey glazes were richer in iron, being copper-based compounds responsible for dark green glazes. The orangish-reddish color of the pastes was provided by hematite. Although the tiles were found in three different locations within the castle, no significant differences were detected among them. The carreaux de pavement from Tiebas had similarities with that from the Bordeaux region. According to the composition data and thickness of tiles from other French carreaux de pavement, the Tiebas artifacts were dated to the 13th century.

Carbonation of heat-activated serpentine driven by Microcystis aeruginosa PCC7806

The capture and storage of CO2 has been a critical strategy towards coping with global warming in recent years. Mineral carbonation is gaining much attention as a novel method of CO2 storage owing to its stability and safety. In this study, the mechanism and effect of carbonation of heat-activated serpentine [Mg3Si2O5(OH)4] driven by cyanobacteria were explored, taking Microcystis aeruginosa PCC7806 as an example. The serpentine was heated at different temperatures, and thermal decomposition of serpentine was characterized by simultaneous thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD) and scanning electron microscope (SEM). The pH, ion concentrations, mineral composition and surface morphology in the process of interactions between the algae cells and heat-activated serpentine were analyzed. The results show that the serpentine can be transformed to forsterite after heat treatment at over 614 °C, and the medium for the addition of heat-activated serpentine at over 614 °C did not allow algae growth. The algae grew well in BG11 liquid medium with 400 °C heat-activated serpentine, and the pH of the culture liquid reached 10.2–10.3, which is in favor of the carbonation of serpentine. The analysis results show the carbonation of trace serpentine. Moreover, the carbonation effect of 400 °C heat-activated serpentine driven by the algae in a solid medium was the most significant, and the carbonate content of serpentine increased by 75.21% as detected by chemical analysis. XRD, SEM, and energy dispersive spectrometer (EDS) results indicate that amorphous CaMg(CO3)2 and MgCO3 were formed on the surface of serpentine driven by the algae. This study advances our understanding of the biological mechanism of serpentine carbonation, and provides a new way to fully exploit serpentine resources in carbon sequestration.

Evaluation of Natural and Calcined Eggshell as Adsorbent for Phosphorous Removal from Water

Natural and calcined eggshell as adsorbent alternatives were evaluated for the removal of phosphorous from water. Calcined eggshell was obtained after treating the natural eggshell at 900 °C in electric furnace for 2 h. The examination on their characteristics was carried out with thermogravimetry and differential thermal analysis (TG/DTA), scanning electron microscope (SEM), X‐ray diffractometer (XRD), and energy dispersive X‐ray spectrometer (EDX). The working solution containing phosphorous was prepared by dissolving KH2PO4 with distilled water. The batch adsorption experiment was conducted by changing various variables such as initial phosphorous concentration, dosage of natural and calcined eggshell, contact time, and pH. It turned out that natural eggshell was unable to remove phosphorous from water, whereas a considerable amount of phosphorous by calcined eggshell was removed in initial contact time (0.25 h). The removal efficiencies were found to be 99.5 and 99.28% at experimental conditions of 5 mg/g of initial phosphorous concentration and a 1.0 g of calcined eggshell dosage, respectively. The removal efficiencies of phosphorous by calcined eggshell were dependent on the abovementioned variables. The difference in the removal behavior of phosphorous by natural and calcined eggshell may be explained due to the different pH values and Ca2+ concentration in solution. The research results suggested that phosphorous removal mechanism by natural eggshell is caused by adsorption of phosphate (as phosphorous source) onto the surface of natural eggshell, however, on the contrary to this, the phosphorous removal on calcined eggshell is arisen from the binding of phosphosphate and calcium resulting in precipitation of calcium phosphate. Experimental data were applied by the pseudofirst‐order and pseudosecond‐order kinetics models and Freundlich and Langmuir isotherm models, respectively. The pseudosecond‐order kinetics model and Langmuir isotherm model were more suitable for calcined eggshell owing to the higher correlation coefficient R2. In conclusion, the result showed that calcined eggshell could become a favorable adsorbent material for removing phosphorous from water.

High efficient removal and mineralization of Cr(VI) from water by functionalized magnetic fungus nanocomposites

A hydroxyl-functionalized magnetic fungus nanocomposite (MFH@GO) was prepared by a simple one-pot method for the removal of Cr(VI) from wastewater. The adsorption behavior of MFH@GO to Cr(VI) in wastewater was discussed in detail. At pH of 5.0 and temperature of 323.15 K, MFH@GO had higher adsorption capacity to Cr(VI) (58.4 mg/g) than the unmodified fungus and GO. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry and differential thermal analysis (TG-DTA), scanning electron microscopy and energy dispersive X-Ray spectroscopy (SEM-EDX) were employed to determine the characteristics of MFH@GO. Results showed that magnetic graphene oxide nanoparticles significantly enhanced the physiochemical properties of the fungi. In addition, the adsorption mechanisms analyses show that Cr(VI) could be reduced and mineralized into ferric chromate in residues. These results suggested that MFH@GO could be used as an promising and alternative biosorbent for removal of Cr(VI) from industrial wastewater.

Thermal and structural analysis of the reaction pathways of α-spodumene with NH4HF2

In this work, the thermal and microstructural analysis of the reaction pathways of α-spodumene with NH4HF2 at low temperatures is presented. The thermal behavior of NH4HF2, mixtures α-LiAlSi2O6/NH4HF2 and by-products (NH4)3SiF6·F/(NH4)2SiF6, are analyzed by simultaneous thermogravimetry and differential thermal analysis (TG-DTA). The study of the crystallite size and lattice strain in the solids is carried out using X-ray diffraction (XRD). The obtained results indicate that the heating rate has a remarkable influence on the processes. At low heating rates, 1 K/min, the reaction between the mineral and NH4HF2 begins at about 351 K and is completed around 426 K, approximately. The obtained products are LiF, (NH4)3SiF6·F, (NH4)3AlF6, NH3 and H2O. In the 368–429 K temperature range, the unreacted NH4HF2 is removed and (NH4)3SiF6·F starts to decompose to generate (NH4)2SiF6. Finally, (NH4)2SiF6 and (NH4)3AlF6 sublimate and decompose at 433 and 493 K, respectively. The main final product is a LiF/AlF3 mixture at 533 K.

Elektroprovodljiva vlakna u kaseticama bombi kojima je napadnut elektroenergetski sistem SR Jugoslavije 1999. godine

Introduction/purpose: The paper presents the mode of operation of the CBU-102(V) 2/B cluster bomb, weighing about 340 kg and containing bomblets with electrically conductive fibers for disabling power plants. Methods: Physical and chemical analyses of the fibers were performed. The following test methods were used for fiber characterization: a binocular microscope for determining fiber thickness and a qualitative XRF analysis performed on an XRF-MiniPal spectrometer, PANalytical. The XRF analysis aimed at qualitative detection of the present elements, which was confirmed by a quantitative chemical analysis. Results: The semi-quantitative XRF analysis determined the content of gallium (0.007%), the peak of which was detected on the spectrum. Gallium nitride is a material that can be used as a semiconductor. The chemical analysis was performed on an atomic absorption spectrophotometer Analyst 300, Perkin Elmer. Conclusion: The instrument for differential thermal analysis and thermogravimetry (DTA/TG), NETZCH STA 409 EP (operational range from 20°C to 1000°C), confirmed that the sample was of 50% silicate origin, non-toxic and with heavy metal content in traces. The rest of the sample is aluminum whose presence in soil can cause decline in soil fertility thus leading to decline in crop yields.

Preparation of hydro-sodalite from fly ash using a hydrothermal method with a submolten salt system and study of the phase transition process

Hydro-sodalites are zeolitic materials with a wide variety of applications. Fly ash is an abundant industrial solid waste, rich in silicon and aluminum, from which hydro-sodalite can be synthesized. However, traditional hydrothermal synthesis methods are complex and cannot produce high-purity products. Therefore, there is a demand for processing routes to obtain high-purity hydro-sodalites. In the present study, high-purity hydro-sodalite (90.2wt%) was prepared from fly ash by applying a hydrothermal method to a submolten salt system. Samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry and differential thermal analysis (TG-DTA), and Fourier transform infrared spectroscopy (FUR) to confirm and quantify conversion of the raw material into the product phase. Purity of the samples prepared with an H2O/NaOH mass ratio of 1.5 and an H2O/fly ash mass ratio of 10 was calculated and the conversion process of the product phase was studied. Crystallinity of the product was influenced more by the NaOH concentration, less by the H2O/fly ash mass ratio. The main reaction process of the system is that the $${\rm{SiO}}_3^{2-}$$ ions produced by dissolution of the vitreous body in the fly ash and Na+ ions in the solution reacted on the destroyed mullite skeleton to produce hydro-sodalite. This processing route could help mitigate processing difficulties, while producing high-purity hydro-sodalite from fly ash.