Metals Ca Research Articles

Efficient separation of high-abundance rare earth element yttrium and lanthanides by solvent extraction using 2-(bis((2-ethylhexyl)oxy)phosphoryl)-2-hydroxyacetic acid

To overcome the drawbacks such as emulsification and esterification reaction of the extractant and phase modifiers of the commonly used naphthenic acid (NA) system for yttrium (Y) separation, some novel extractants have to be developed. By combining the functional groups of commercial organophosphorus extractants, carboxylic acids and alcohol phase modifiers, a novel extractant 2-(bis((2-ethylhexyl)oxy)phosphoryl)-2-hydroxyacetic acid (HPOAc, HL) was designed and synthesized. The pKa value of HPOAc is a little larger than that of 2-ethylhexyl phosphoric acid mono-2-ethylhexylester (P507) and smaller than that of common carboxylic acid extractants such as NA and sec-octylphenoxy acetic acid (CA−12). Y(III) is the most difficult to be extracted among trivalent rare earth elements (REEs(III)) by HPOAc. The distribution ratios exhibit a distinct “tetrad effect”. The extraction mechanism follows a cation exchange mechanism with the extraction complex being deduced as REL3. Compared with NA and CA−12, HPOAc has higher extraction ability for REEs(III), and better performance in the separation of Ln(III) and Y(III). The extraction capacity for Y(III) is about 1.75 times higher than those of NA and CA−12. The loaded Y(III) and Sm(III) can be completely stripped by 0.75 mol/L HCl solution. Moreover, even if the organic phase is saturated or there are several impurity metal ions (Mg(II), Al(III), Ca(II), Mn(II) and Zn(II)) in the aqueous solution, two phases can still be separated very quickly and the fluidity of the loaded organic phase is good without the phase modifiers. Encouragingly, the HPOAc system also exhibits good separation performance towards REEs(III) and the impurity metal ions. Finally, a cascade extraction process for separating Ln(III) and Y(III) was developed using HPOAc as the extractant. The Y product with the purity of 99.31 wt% was obtained by 20 stages of extraction and 4 stages of scrubbing.

Understanding natural radiation induced cationic and anionic defects in natural fluorite single crystals through spectroscopic investigations

Fluorite single crystals, CaF2 are multifunctional crystals that have potential applications in environmental, thermo-luminescent and accidental dosimetry. A comprehensive investigation of the co-located naturally occurring colourless and coloured (yellow, sea-green, purple, blue, black) fluorites (CaF2) doped with bivalent and multivalent cations was carried out for the cationic and anionic sub-lattice defects generated due to natural irradiation from associated actinide containing pyrochlore grains. Detailed spectroscopic analyses have been used to map the various cationic and anionic defect structures such as O3− and O2--Vacancy type defect complexes in yellow fluorites, F-centres and irradiation induced metallic Ca in purple, blue and black fluorites. The confinement of the radiation damage only to the anionic sub-lattice was explained in terms of higher displacement cross-section for F (59 b) as compared to Ca (33 b) as well as lower energy requirement to create F displacements and vacancies. It is observed that the fluorite retained its phase stability under natural radiation exposure and elemental substitutions.

Correlation between Electrolyte Chemistry and Solid Electrolyte Interphase for Reversible Ca Metal Anodes

AbstractThe development of rechargeable Ca metal batteries (RCMBs) is hindered by the Ca2+ passivating solid electrolyte interphases (SEIs). The cation solvation structure dictated by electrolyte chemistry plays a critical role in the SEIs properties. While a relatively weak cation‐solvent binding is preferred in Li metal anodes to promote anion‐derived SEIs, we demonstrate an enhanced Ca deposition/stripping reversibility under a strong cation‐solvent interaction, which is materialized in strongly‐solvating solvent and highly‐dissociated salt combinations. Such electrolyte formulations benefit the formation of solvent‐occupied solvation structure and minimize the anion reduction, resulting in organic‐rich/CaF2‐poor SEIs for reversible Ca metal anodes. Furthermore, RCMBs paired with an organic cathode using the optimized electrolytes are demonstrated as a proof‐of‐concept. Our work reveals the paradigm shift in SEIs design for Ca metal anodes, opening up new opportunities for emerging RCMBs.

Correlation between Electrolyte Chemistry and Solid Electrolyte Interphase for Reversible Ca Metal Anodes.

The development of rechargeable Ca metal batteries (RCMBs) is hindered by the Ca2+ passivating solid electrolyte interphases (SEIs). The cation solvation structure dictated by electrolyte chemistry plays a critical role in the SEIs properties. While a relatively weak cation-solvent binding is preferred in Li metal anodes to promote anion-derived SEIs, we demonstrate an enhanced Ca deposition/stripping reversibility under a strong cation-solvent interaction, which is materialized in strongly-solvating solvent and highly-dissociated salt combinations. Such electrolyte formulations benefit the formation of solvent-occupied solvation structure and minimize the anion reduction, resulting in organic-rich/CaF2 -poor SEIs for reversible Ca metal anodes. Furthermore, RCMBs paired with an organic cathode using the optimized electrolytes are demonstrated as a proof-of-concept. Our work reveals the paradigm shift in SEIs design for Ca metal anodes, opening up new opportunities for emerging RCMBs.

EFFECT OF OXIDATIVE STRESS ON CATALASE INDUCTION AND OPTIMIZATION OF KINETIC PERFORMANCE OF ENZYME FROM B. SUBTILIS KIBGE HAS 1

The Catalase (H2O2 oxidoreductase, EC.1.11.1.6) is an enzyme that catalyses the decomposition of hydrogen peroxide to oxygen and water to protect the cell against oxidative stress. The aim of current study is to observe the effect of increasing oxidative stress on the catalase synthesis. Results of the study shows that the increase in oxidative stress by adding 0.1 % cholesterol in medium raises the catalase production by B. Subtilis KIBGE HAS 1. The molecular mass of this partially purified catalase was found to be 210 kDa by native PAGE. The enzyme was purified up to 8.9 %. The enzyme exhibits high thermal stability and retain 80.2 % of its original activity when stored at 50°C for 120 min. with Km and Vmax of 41.89 mM and 77.97 U/mg of protein respectively. Among various metal ions, Na+, Ca+ and Ba+ ions enhance the catalase activity however; Hg+ causes an inhibitory effect. The findings of this study give advantage to industries regarding augmentation of catalase production by generating the oxidative stress and therefore indirectly increase the production of enzyme.

Dry dechlorination of polychlorinated biphenyls in contaminated soil by using nano-sized composite of metallic Ca/CaO and its mechanism

Soil contamination by PCBs is still known as a serious problem across the world, and the development of new technologies or the improvement of existing ones (e.g. higher efficiency, shorter processing time, lower input energy) are more and more important. Moreover, understanding the chemistry of the entire process, from a mechanistic point of view, can accelerate the process of improvement. In these circumstances, we attempted a clarification of the highly efficient degradation of PCBs by nano-sized particle of metallic Ca in CaO (“nCa”) at 250 °C in dry solid state conditions. The reaction involved the hydrodechlorination, simple reduction, reductive coupling and hydroxylation processes. The detoxification efficiency reached over 99%. A tentative pathway and mechanism is proposed for explaining the final reactions products. Finally, the process was applied to real PCBs-contaminated soil, containing various amounts of PCBs, with a total success in completely eliminating the toxic polychlorinated compounds.

Characterization of PM2.5 in Coastal Urban Area, Northwest Morocco: Seasonal Variations, Elemental Composition and Source Apportionment

Sale, located along the Atlantic Ocean, is the third-largest city in Morocco. The Bouregreg river separates Sale from Rabat (Morocco’s capital city). This City is characterized by a high demographic density. Their main air pollution sources are traffic, ocean, potteries, fishing, domestic heating, and artisanal activities. Ambient PM2.5 particles were collected in an urban area of Sale City (Morocco) from July 2018 to July 2019. The sampling was carried out using a Dichotomous sampler and the Total X-Ray Fluorescence technique (TXRF) was used to evaluate the elemental composition of the collected filters. In this paper, chemical characterization, and source apportionment of PM2.5 were investigated. The results showed that the PM2.5 mass concentrations vary, during the sampling period, from 3.08 µg/m3 to 49.48 µg/m3 with an average of 17.30 µg/m3. The highest values were observed in winter while the lowest in summer. The influence of atmospheric transport scenarios on the levels of PM was carried out using air mass back-trajectories, using the HYSPLIT™ model. This study allowed identifying four main clusters arriving at our receptor site in Sale City: Iberian Coast (24%), Near Atlantic Ocean (33%), Local (28%), and Oceanic (15%). For seasonal variations of metal concentrations, K, Ca, V, Mn, Fe, Ni, Cu, Zn, As, Sr, Ba, and Pb exhibited their highest concentrations during winter while Ti and Cr, their highest concentrations were observed during Autumn. The Enrichment Factor (EF) analysis showed that Ti, Sr, Mn, K, Ca, and Ba are mainly originated from airborne dust with EF < 10, V, Cu, Cr have both natural and anthropogenic sources with 10 < EF < 100, while Ni, Zn, and Pb were mainly from anthropogenic source with EF > 100. Five factors were selected in Positive Matrix Factorization (PMF) model’s analysis: crustal contribution, road dust, brake wear, heavy oil combustion, and exhaust vehicle emissions. Their contributions to PM2.5 were 5%, 53.6%, 20.1%, 14.3% and 7%, respectively. Road dust and vehicle exhaust sources showed the highest contribution in winter; while soil dust, brake wear, and oil combustion sources contributed the most in summer. The present study could be considered as the first source apportionment study on PM2.5 fractions carried out in Sale City, Morocco.

The effects of alkali metals and alkaline earth metals on the mechanism of N-containing gases production during glutamic acid pyrolysis

Biomass contains Alkali and Alkaline Earth Metals (AAEMs) which, during the pyrolysis process of biomass, can affect the production of harmful gases such as NH3, HCN and HNCO. In this study, the effect of AAEMs on the mechanisms of amino acid pyrolysis was analysed with a combination of Thermogravimetric- Fourier Transform Infrared Spectroscopy (TG-FTIR) experiments and Density Functional Theory (DFT) calculations. Moreover, the four most abundant metals in biomass (K, Ca, Na and Mg) were selected, and glutamic acid (Glu), which accounts for the largest proportion of plant proteins, was studied. The results showed that all four metal chlorides had an inhibitory effect on the production of N-containing gases, while promoted the char formation. Sodium was the most effective in reducing the yields of NH3, HCN and HNCO. The alkaline earth metals (Ca and Mg) could influence the temperature range for gas release. Diketopiperazines (DKP) were produced from the pyrolysis of amino acids, and the precursor of HCN and HNCO. This study explained the effect of AAEMs on nitrogen conversion mechanisms during biomass pyrolysis and provided theoretical support for controlling the nitrogen element transfer.

Periodic DFT computation of rotational barriers for linear molecules in zeolites: Validation via zero-point energies and isotopic heat difference values of adsorbed H2/D2

A climbing image nudged elastic band (cNEB) algorithm was applied on the basis of density functional theory (DFT) calculations of the rotational barriers of eight linear molecules (H2, N2, O2, CO, CO2, NO, N2O, C2H2) adsorbed in NaY and NaCaY periodic zeolite models at the MeII cation sites (the Na or Ca metal cation in the SII site) located near the 6R windows. A specific approach is applied for molecules with positive quadrupole (H2, C2H2) and small negative quadrupole (3O2) moments while applying cNEB. The obtained T-geometry relative to the cation is the most frequent case for H2 adsorption in cationic form sieves and metalorganic frameworks (MOFs). The computed barriers for the T- and other linear (L) orientations are in good correlation with the quadrupole moments taken from literature irrespective of the dipole values (CO, NO, N2O). In the case of NaY, the Al distribution per 6R sites is also discussed which allowed finding particular favorite adsorption sites. The calculated zero-point energies relative to the obtained rotational barriers regarding the H2 - D2 pair result in a qualitative agreement with the experimental isotopic difference in the H2/D2 adsorption heats in NaY which ultimately lead to the H2/D2 separation coefficient.

Laser-Assisted Method for Cleaning and Analysis of Archaeological Metallic Coins

Metal coins discovered during archaeology have artistic and cultural value. Careful cleaning is required for artifact conservation. Metal artifacts must be cleaned to remove corrosion, which can range from tarnishing to a thick crust, in addition to dust, previous coatings, and burial deposits. Cleaning corrosion is still a challenging conservation process, but the advantages of using traditional cleaning methods outweigh the disadvantages. The current study aimed to evaluate the use of a nanosecond infrared Q-switched Nd: YAG pulsed laser for biodeteriogen elimination by laser cleaning and elemental analysis via LIBS analysis on old, corroded coins. The corroded coins used in this study were found in Egyptian burial dirt. Four different varieties of unknown corroded coins were exposed to laser cleaning testing. Throughout the cleaning process, LIBS diagnostics was used to monitor the laser ablation process as it removed various types of corrosion products. The coins were analyzed with a scanning electron microscope equipped with an energy-dispersive X-ray analyzer before and after the laser cleaning to assess the efficacy of the suggested laser setup technique used in this experiment (SEM-EDX). The results show a reduction in the spectral lines of corroded metals (Cu, Ca, and Mg) in the investigated coins after cleaning when compared to the original analyses. However, the surface morphology of each coin changes somewhat due to the presence of CuOx, which was recognized by increasing the strength of O lines, ensuring the viability of utilizing LIBS to identify the unknown coins tested.

Gasification and Co-gasification of paper-rich, high-ash refuse-derived fuel in downdraft gasifier

Among the various waste-to-energy conversion methods, gasification is a technically feasible option for municipal solid waste valorization, meeting current emission limits and reducing landfill disposal burden. This work investigates the potential of paper rich (⁓ 76 % wt.) commercial refuse-derived fuel (RDF) having high ash content (⁓ 17 % wt.) for gasification and co-gasification in downdraft gasifier. The ash formed from RDF, with higher proportion of alkaline earth metals (Ca and Mg) and lower proportion of alkali metals (Na and K), can effectively avoid agglomeration and clinker formation during gasification. The producer gas obtained from RDF gasification reports a maximum lower heating value of 4.34 MJ/Nm3at an equivalence ratio of 0.34 with corresponding cold gas efficiency of 59.24%.Co-gasification of RDF with biomass was examined as a strategy to reduce overall ash content of the mixture, using sawdust. Co-gasification has exhibited a synergy between RDF and sawdust when the RDF fraction in feedstock is at the higher side. A maximum lower heating value of 4.65 MJ/Nm3 was obtained during the co-gasification and the tar yield reduced from 13.6 g/Nm3to 8.8 g/Nm3 when RDF in the feed increased from 25% to 75% (w/w).

Dairy farm roadway surface materials as a P-source within the nutrient transfer continuum framework

Internal farm roadways are connectors within agricultural landscapes, which act as sub-components of the nutrient transfer continuum (NTC). On dairy farms, roadway surface runoff dissolved and particulate phosphorus (P) sources stem from a combination of cow excreta deposited at locations that impede animal flow, soil deposited from cow hooves or machinery tyres, run-on from up-gradient fields, public roadways or farmyards and incidental spill of organic/inorganic fertilizers. The present study investigates the storage and potential release of P from the underlying roadway material (i.e. composite of soil and stone aggregates) as this source component is not considered in the NTC framework or documented in the literature. Herein, farm roadway materials were sampled (to 1 cm depth) at 17 locations avoiding fresh cow excreta. Multiple location types were selected e.g. straight roadway sections, roadway junctions, before and adjacent standoff areas associated with cattle underpasses, with all locations varying in distance from the farmyard. Roadway samples were analysed for phosphorus (P) and metals (Al, B, Ca, Co, Cu, Fe, K, Mg, and Mn) content. Results showed that the soil component of roadway materials are significant P legacy sources and are in themselves a P-storage component that merits inclusion in the NTC framework. All sampled locations, when compared with fresh roadway stone aggregates or surrounding fields, had highly elevated P with plant available Morgans P > 8 mg L-1 (Index 4, ranging from 10 – 110 mg L-1). Sampling points within 100 m of the farmyard together with roadway junctions and underpasses beyond this distance had highest P concentrations. Critical source areas, where source, mobilisation and transport of P to waters coincided, formed at three locations. Possible mitigation measures are a) divert roadway runoff into fields using low-cost surface water breaks, b) disconnect cattle underpass tanks from receiving waters and c) change roadway infrastructure to improve cow flow and minimise source build-up. Future research should examine P loads in runoff from roadway sections across farm typologies and roadway material types.

(Battery Division Student Research Award Sponsored by Mercedes-Benz Research & Development) Energy Storage with the Abundant Divalent Metal Batteries

The transitions to electric vehicles and renewable power sources are not only a change of personal lifestyles but also tactical approaches to a sustainable future for us and our offspring, in which the energy supply will no longer be at the expense of natural resource depletion and environmental damage. The cornerstones of this sensational transition are rechargeable batteries, particularly lithium-ion batteries (LIBs). And it is not difficult to imagine that the consumption and demand for LIBs will skyrocket in the foreseeable future if EVs dominate the market. However, the massive growth of the LIBs industry will lead to another resource crisis due to the scarcity of materials used in LIBs, such as lithium and cobalt1.While battery recycling could partially relieve these issues, it is desirable to find abundant and cheap substitutes, especially for the regions where lithium resources are less accessible. Magnesium (Mg) and calcium (Ca) are among the most abundant elements in the earth's crust (>1000 times more abundant than lithium)2. More importantly, they store charges by two electron-transfer reactions and have fairly low redox potentials3. When appropriate high-potential cathodes are paired with Mg or Ca metal, the resulting rechargeable magnesium and calcium batteries (RMBs and RCBs) could render energy densities comparable to or even higher than LIBs4. However, these systems are always typified by irreversibility. The underlying reason is that it is much more difficult to desolvate and transfer the divalent Mg2+ or Ca2+ than Li+ at the electrolyte-electrode interface and inside electrode materials, and the extra energy required for reaction sometimes causes undesirable parasitic reactions such as electrolyte decomposition and irreversible phase transition in the intercalating cathodes (especially high-voltage oxide cathodes) 5-7. These issues have plagued the practicality of RMBs for over a decade.In this study, we found that the charge transfer kinetics involving Mg2+ and Ca2+ in both transitional metal oxide cathodes and the metal anodes can be significantly enhanced with methoxylethyleneamine chelants in the solvation sheath8. A peculiar observation is that the methoxylethyleneamine chelants demonstrate a much higher affinity toward the Mg2+ than the ether solvent as demonstrated by the Nuclear Magnetic Resonance (NMR) results, requiring higher energy to remove them from the solvation sheath. However, the large desolvation energies do not translate to more sluggish reaction kinetics; on the contrary, low overpotentials were observed. With a combined effort of the surface chemistry analysis with X-ray photoelectron spectroscopy, solvation sheath characterization with NMR and Raman spectroscopy, electrochemical modeling with Marcus-Chidsey kinetics for interfacial electron transfer, and quantum chemistry calculations, we have identified that the cause of such unconventional behavior is that the charge transfer reactions occur without desolvation. This process is significantly facilitated by the polarizable structures of the chelants in the solvation sheath. By boosting the main reaction kinetics, the undesirable side reactions are suppressed without the solid electrolyte interface as in LIBs, thus opening up a completely different electrolyte design approach to stabilize high-energy RMBs and RCBs. Furthermore, this achievement could help reduce reliance on mining raw materials to build LIBs and provide cheaper and safer options for future energy storage. Reference Herrington, R. Nature Reviews Materials 2021, 6, 456-458. Muldoon, J.; Bucur, C. B.; Gregory, T. Quest for Nanoaqueous Multivalent Secondary Batteries Magnesium and Beyond. Chemical Reviews 2014, 114, 11683-11720. Li, M.; Lu, J.; Ji, X.; Li, Y.; Shao, Y.; Chen, Z.; Zhong, C.; Amine, K. Design strategies for nonaqueous multivalent-ion and monovalent-ion battery anodes. Nature Reviews Materials 2020, 5, 276-294. Canepa, P.; Gautam, G. S.; Hannah, D. C.; Malik, R.; Liu, M.; Gallagher, K. G.; Persson, K. A.; Ceder, G. Odyssey of Multivalent Cathode Materials: Open Questions and Future Challenges. Chemical Reviews 2017, 117, 4287-4341.

Alloy Anodes for Nonaqueous Calcium-Ion Batteries

In the search to find new battery technologies that will extend current Li-ion technology towards the high-energy density and stability required for extended-range electric vehicles and efficient grid energy storage, earth-abundant working metal ions are increasingly being investigated. Calcium ion batteries are of interest due to calcium’s wide accessibility and abundance in the earth’s crust, but present novel challenges, such as sluggish diffusion kinetics and lack of known suitable intercalation hosts. The replacing of Ca metal anodes with new alloy materials that can work reversibly in current electrolyte systems is one practical route towards realizing the high voltage and capacity of a calcium battery. This complements current research in conventional Li-ion batteries to replace the conventional graphite anode by Group IIIA and IV elements. In this work, research into new alloy designs in novel electrochemical systems for Ca batteries will be explored and evaluated alongside key issues and challenges towards commercial applications.

Microscopic impact mechanism of alkali earth metal poisoning and Ce modification on the deNOx over the γ-Fe2O3 (0 0 1) surface

Ce-doped γ-Fe2O3 catalyst has excellent deNOx and poisoning resistance. However, the NH3-SCR mechanism of improving of Ca poisoning by Ce at atomic level is still unclear. Therefore, the effects of alkali earth metal Ca poisoning on the γ-Fe2O3 (001) surface and Ce modified Ca-γ-Fe2O3 (001) surface in the selective catalytic reduction (SCR) of NOx by NH3 were studied. γ-Fe2O3 catalyst poisoned by Ca results from the decrease of surface acidity and the improvement of stable nitrite/nitrate species. Ce brings extra Lewis acid sites for the NH3 adsorption when it is used to modify the poisoned catalyst, which improves the NH3 adsorption and activation. The adsorption of NO and O2 as well as the decomposition of O2 may be inhibited by the presence of Ce. Most of the stable, inactive nitrite/nitrate species are active and decomposed. The production of NH2 is aided by the enhancement of the dehydrogenation process of NH3. This study provides a direction for prolonging the service life of low-temperature Fe-based deNOx catalysts in industrial cement furnaces.

Appraisal of heavy metal pollution in alluvial aquifers. Study case on the protected area of Ronișoara Forest, Romania

• Waters from protected area are rich in As, Ca and heavy metals (Pb, Al, Mn, Fe, Se). • Generally, the WQI scores indicate excellent, medium, and low quality. • HEI and HPI scores indicate three levels of pollution. • Na, Ca, Mg, Co, Cd are mainly transfer from mud to the alluvial aquifers. • This research is a reference for aquifers protection in a protected area. This study was carried out in a protected area (Ronișoara Forest) in Romania. A combined approach of quality assessment of alluvial aquifers is employed, by determining the chemistry and applying two pollution indices based on heavy metals concentrations (HPI- Heavy metal Pollution Index and HEI- Heavy metal Evaluation Index), a quality assessment index based on specific physico-chemical indicators (WQI- the Water Quality Index) and different plots (Durov, Schoeller and TIS-Total Ion Salinity). The study revealed that waters are rich in manganese, calcium, sodium, sulphate, ammonium, manganese, iron, total dissolved solids, dominated by bicarbonates. The chemicals’ sources are related to the water–rock interactions and to mine exploitation activities. Correlations were observed between the electrical conductivity and sulphate, total dissolved solids and sulphate, and total hardness and electrical conductivity. The results based on the levels of heavy metals pollution indicate that the studied water samples are characterized by low, medium and high pollution levels, with values ranging between 0.40 and 234. The WQI scores vary from 8.6 to 54, generally indicating excellent and medium quality, and low quality for two samples. This research, one of the first in the area, can serve as a reference for the protection of natural water resources and for the contamination control of alluvial aquifers in the protected area of Ronișoara Forest.

Solid state deoxidation of zirconium-oxygen solid solution using a combination of metallic Ca and Y in CaCl2 flux

Aiming at the deficiencies of the three typical "external gettering" systems: metal-oxide equilibrium deoxidation (MED), halide flux deoxidation (HFD) and electrochemical deoxidation (ECD), a novel deoxidation method based on the combination of oxytropic rare earth metal Y and Ca for in-depth deoxidation of Zr-O solid solution was proposed. The thermodynamic properties of the deoxidation method were analyzed, and it was found that the addition of metallic Y could significantly improve the deoxidation ability of the Ca-CaCl2 system, because Y could form Y-Y2O3 equilibrium to "anchor" the activity of CaO (aCaO) at a very low level. When the activity of Y2O3 (aY2O3) and aCaO in the flux conforms to aY2O3< 18.9a3CaO at 1173 K, the deoxidation mode is thermodynamically feasible. Experiments were conducted to verify the method. The results showed that even if CaO was saturated in CaCl2 flux, the oxygen content of Zr-O solid solution could still be controlled at the level of less than 100 ppm, thus the "anchoring effect" of Y on aCaO was verified. The oxygen content, phase and microstructure of the reacted Y specimens were analyzed, which suggested that when the ratio of CaO was less than 40 % of its solubility in CaCl2 flux, the oxygen potential of the system was controlled by Y-O solid solution, and when it was greater than 40 %, the oxygen potential of the system was controlled by Y-Y2O3 equilibrium.

Structural characteristics and thermal conversion performance of ash and slag from circulating fluidized bed gasifier

Based on the circulating fluidized bed (CFB), Xinjiang Zhundong coal (ZDC) gasification ash (FA: fly ash; BA: bottom slag) was analyzed by industrial analysis, ultimate analysis and Fourier infrared spectroscopy to determine the basic properties and functional group species. The results show that BA contains up to 99.30% in ash, while FA shows high fixed carbon and C content of 69.30% and 73.78% respectively. Furthermore, the carbonaceous forms and surface morphology of ZDC and FA were characterized by Raman, XRPES and SEM, and the pyrolysis, combustion and gasification characteristics of ZDC and FA were studied with TG-DTG methods. XRPES show that C content of the FA surface is 89.42%, and exists primarily as >C–C< and >C–H, while O was in the form of >C=O. Alkaline earth metals Ca bound to the above-mentioned carbon-involved functional groups cause high disorder in FA. SEM observed that the rough and porous FA surface occurs due to spherical particles of molten mineral attached and embedded surface and pore channels. The thermal conversion characteristics show that the maximum weight loss rate peak temperature of pyrolysis and combustion of FA is significantly higher than that of ZDC, indicating that the pyrolysis and combustion performance of FA is reduced. However, 100% carbon conversion of FA uses about half the time compared with ZDC and the gasification performance has improved significantly since it has well-developed pore structures, more amorphous carbon and abundant active sites, enhancing diffusion of CO2 from gasifiers. Briefly, FA has the potential and ability to be recycled for direct utilization in CFB as gasification feed.

First Lidar Profiling of Meteoric Ca+ Ion Transport From ∼80 to 300 km in the Midlatitude Nighttime Ionosphere

AbstractWe report a world record of lidar profiling of metallic Ca+ ions up to 300 km in the midlatitude nighttime ionosphere during geomagnetic quiet time. Ca+ measurements (∼80–300 km) were made over Beijing (40.42°N, 116.02°E) with an Optical‐Parametric‐Oscillator‐based lidar from March 2020 through June 2021. Main Ca+ layers (80–100 km) persist through all nights, and high‐density sporadic Ca+ layers (∼100–120 km) frequently occur in summer. Thermosphere‐ionosphere Ca+ (TICa+) layers (∼110–300 km) are likely formed via Ca+ uplifting from these sporadic layers. The lidar observations capture the complete evolution of TICa+ layers from onset to ending, revealing intriguing features. Concurrent ionosonde measurements show strong sporadic E layers developed before TICa+ and spread F onset. Neutral winds can partially account for observed vertical transport but enhanced electric fields are required to explain the results. Such lidar observations promise new insights into E‐ and F‐region coupling and plasma inhomogeneities.

Mass characterisation of elemental toxicants in popular cigarettes sale in Pakistan using ICP-OES

ABSTRACT Environmental pollution and public health risks increase due to elevated metal levels in cigarettes throughout the globe especially in the developing countries. Herein, study is carried out to investigate the heavy metals and rare earth element contents in the popular cigarette brands (local and imported) in Pakistan. Twenty-six elements are measured in cigarette, tobacco, wrapping paper and filter (n = 168) sold in the Pakistan market in 14 brands of cigarettes using inductively coupled plasma-optical emission spectrometry (ICP-OES). The mean concentrations of Cr, V, Mo, Ni, Sn, As, Sb, Fe, Al, Mg, Ti and B (8.30, 0.22, 0.45, 1.85, 4.63, 1.32, 0.89, 378.01, 180.18, 2134.21, 6.53 & 22.20 μg/g), respectively, are slightly higher in local cigarette brands and the mean concentration of Co, Cd, Pb, Se, Sr, Mn, Cu, Zn, Ca, K, Na, Y, Zr and Ba (0.49, 0.69, 1.58, 1.47, 71.03, 68.23, 32.69, 32.33, 2906.82, 7601.73, 962.31, 0.10, 1.04 & 35.19 μg/g), respectively, are slightly higher in imported cigarette brands. The concentrations of Pb, Ni, Cd, Co, Fe and Zn in local tobacco cigarettes are approximately comparable to concentration levels of metals in imported tobacco cigarettes sold in other countries. While a strong positive correlation was observed in Cr, Sn, Mn, Ba, Ni, Co, As and Sr, while K, Mo, Ti, Ca and Mo were negatively associated with other elements. In addition, this study also provides an important information on the elemental levels such as alkali metals (Na & K), alkaline rare earth metals (Mg, Ca, Sr & Ba), transition metals (Ti, V, Mo, Y & Zr), post-transition metals (Sn), metalloids (B & As) and reactive non-metal (Se) for the very first time in Pakistan in different components of cigarettes. We believe that this study will be beneficial to the prevention of public health hazards and the reduction of human health risks through tobacco consumption.