Pure Ca Research Articles

Direct reduction of CO2 to carbon material on liquid cathode in molten salts

This study presents a novel method for the direct reduction of CO2 to produce carbon materials on a liquid cathode in high-temperature molten salts. CO2 gases were introduced into a Sn-Li liquid alloy, and they were subsequently reduced to solid carbons by the Li in the alloy. Unreacted CO2 gases were absorbed as carbonate ions (CO32−) in molten salts containing oxide ions (O2−). Subsequently, these carbonate ions were electrochemically reduced to solid carbons on the liquid cathode surface. Consequently, the current density was five times higher than that achieved using the conventional method without bubbling CO2 into the liquid cathode. The enhanced current density can be attributed to the combined thermochemical reduction of CO2 by Li and the electrochemical reduction of CO32−. This combination was realized for the first time at a relatively positive potential range, where pure Li or Ca cannot be deposited, leading to the carbon yield of over 90 % relative to CO2 feed reached. The resulting carbons contained a trace amount of Sn, which could be removed by washing after milling. These results show the potential for efficient and sustainable carbon capture and conversion technologies using liquid cathodes in high-temperature molten salts for CO2 reduction.

Calcium Acetate Drug Produced from Rapana venosa Invasive Gastropod Shells: Green Process Control Assisted by Raman Technology.

The highly demanded calcium acetate (Ca(CH3COO)2) for biomedicine and various industries constantly requires green and low-cost methods of synthesis. In the present work, a sustainable approach to produce Ca(CH3COO)2 is reported as a proof of concept, processing for the first time as a starting material the worldwide highly abundant Rapana venosa shells, which is a neglected biogenic waste with high economical potential due to the rich mineral and organic pigmentary content. A green synthesis involving an eco-friendly acetic acid has been optimized at room temperature, without any additional energy consumption, and the resulting saturated Ca(CH3COO)2 solution was further slowly evaporated in three stages to obtain white Ca(CH3COO)2 crystalline powder, without impurity traces. Raman spectroscopy provided efficient structural information for every step of the process control, during demineralization as well as end product validation. Yields as high as 87.5% of highly pure Ca(CH3COO)2 mass have been achieved from raw R. venosa shells, proving the uniqueness and economic viability of the method. X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDX), and Fourier-Transform IR spectroscopy (FTIR) analyses validated the final product identity, hydration status, crystalline morphology, and composition. The purity of the resulting product suggests a high valorization potential of the abundant R. venosa shell in the context of the blue bioeconomy and offers a cleaner and efficient method of Ca(CH3COO)2 production with important applications in relevant industries.

HTO and selenate diffusion through compacted Na-, Na–Ca-, and Ca-montmorillonite

Radionuclide transport in smectite clay barrier systems used for nuclear waste disposal is controlled by diffusion, with adsorption significantly retarding transport rates. While a relatively minor component of spent nuclear fuel, 79Se is a major driver of the safety case for spent fuel disposal due to its long half-life (3.3 × 105 yr) and its low adsorption to clay (KD < 10 L/kg), thus a thorough understanding of Se diffusion through clay is critical for understanding the long-term safety of spent fuel disposal systems. Through-diffusion experiments with tritiated water (HTO, conservative tracer) and Se(VI) were conducted with a well-characterized, purified montmorillonite source clay (SWy-2) under a constant ionic strength (0.1 M) and three different electrolyte compositions: Na+, Ca2+, and a Na + -Ca2+ mixture at pH 6.5 in order to probe the effects of electrolyte composition and interlayer cation composition on clay microstructure, Se(VI) aqueous speciation, and ultimately diffusion. The results were modeled using a reactive transport modeling approach to determine values of porosity (ε), De (effective diffusion coefficient), and KD (distribution coefficient for adsorption). HTO diffusive flux was higher in Ca-montmorillonite (De = 1.68 × 10−10 m2 s−1) compared to Na-montmorillonite (De = 7.83 × 10−11 m2 s−1). This increase in flux is likely due to a greater degree of clay layer stacking in the presence of Ca2+ compared to Na+, which leads to larger inter-particle pores. Overall, the Se(VI) flux was much lower than the HTO flux due to anion exclusion, with Se(VI) flux following the order Ca (De = 1.03 × 10−11 m2 s−1) > Na–Ca (De = 2.12 × 10−12 m2 s−1) > Na (De = 1.28 × 10−12 m2 s−1). These differences in Se(VI) flux are due to a combination of factors, including (1) larger accessible porosity in Ca-montmorillonite due to clay layer stacking and smaller electrostatic effects compared to Na-montmorillonite, (2) larger accessible porosity for neutral-charge CaSeO4 species which makes up 32% of aqueous Se(VI) in the pure Ca system, and (3) possibly higher Se(VI) adsorption for Ca-montmorillonite. Through a combination of experimental and modeling work, this study highlights the compounding effects that electrolyte and counterion compositions can have on radionuclide transport through clay. Diffusion models that neglect these effects are not transferable from laboratory experimental conditions to in situ repository conditions.

Analyzing the upscaling potential and geospatial siting of calcination-free calcium hydroxide production in the United States

This study evaluates the techno-economic feasibility and the embodied carbon dioxide intensity (eCI) of a novel process for producing nominally pure (>95 mass %) calcium hydroxide without the need for the thermal calcination of limestone. The process relies on the aqueous extraction of calcium from alkaline industrial wastes following which portlandite (Ca(OH)2: CH, a.k.a. slaked lime or hydrated lime) is precipitated by application of a waste-heat based thermal swing. This approach takes advantage of the temperature dependent solubility of CH at ambient pressure. We evaluated the feasibility of implementing this process in the U.S. based on the geospatial availability of waste heat and slags as a Ca-source. For the base case, the cost of production of “Low-Temperature Portlandite (LTP)” is 2-to-3 times that of traditional portlandite (∼$180/tonne). The main driver of cost is the electricity demand for reverse osmosis (RO) which is used to concentrate Ca-ions in solution, and the costs of membrane replacement. Our sensitivity analysis showed that parity with the cost of production of traditional portlandite is readily achievable by selecting membranes with better durability (i.e., better pH resistance) and flux (i.e., higher permeability) without sacrificing selectivity. Significantly, LTP features an eCI that is between 40%- and - 80 % lower than its traditional counterpart when electricity is sourced from natural gas combustion or wind power, respectively. Finally, our geospatial analysis reveals that there are three areas in the U.S. with the potential for implementation of industrial-scale facilities that could produce at least 50 tonnes of pure Ca(OH)2 per day, while achieving a production cost of ∼$270 per tonne of Ca(OH)2, owing to the proximity between slag feedstocks and waste heat sources.

Structure and equation of state of Ti-bearing davemaoite: new insights into the chemical heterogeneity in the lower mantle

Abstract Davemaoite (CaSiO3 perovskite) is considered the third most abundant phase in the pyrolytic lower mantle and the second most abundant phase in the subducted mid-ocean ridge basalt (MORB). During the partial melting of the pyrolytic upper mantle, incompatible titanium (Ti) becomes enriched in the basaltic magma, forming Ti-rich MORB. Davemaoite is considered an important Ti-bearing mineral in subducted slabs by forming a Ca(Si,Ti)O3 solid solution. However, the crystal structure and compressibility of Ca(Si,Ti)O3 perovskite solid solution at relevant pressure and temperature conditions were not systematically investigated. In this study, we investigated the structure and equations of state of Ca(Si0.83Ti0.17)O3 and Ca(Si0.75Ti0.25)O3 perovskites at room temperature up to 82 GPa and 64 GPa, respectively, by synchrotron X-ray diffraction (XRD). We found that both Ca(Si0.83Ti0.17)O3 and Ca(Si0.75Ti0.25)O3 perovskites have a tetragonal structure up to the maximum pressures investigated. Based on the observed data and compared to pure CaSiO3 davemaoite, both Ca(Si0.83Ti0.17)O3 and Ca(Si0.75Ti0.25)O3 perovskites are expected to be less dense up to the core-mantle boundary (CMB), and specifically ~1-2 % less dense than CaSiO3 davemaoite in the pressure range of the transition zone (15-25 GPa). Our results suggest that the presence of Ti-bearing davemaoite phases may result in a reduction in the average density of the subducting slabs, which in turn promotes their stagnation in the lower mantle. The presence of low-density Ti-bearing davemaoite phases and subduction of MORB in the lower mantle may also explain the seismic heterogeneity in the lower mantle, such as large low shear velocity provinces (LLSVPs).

The Effectiveness of Silver Nanoparticles Mixed with Calcium Hydroxide against Candida albicans: An Ex Vivo Analysis.

The purpose of this study was to assess the antifungal activity of silver nanoparticles (AgNPs) in combination with calcium hydroxide (Ca(OH)2) against Candida albicans (C. albicans). AgNPs was mixed with pure Ca(OH)2 powder in an aqueous base. A standard suspension (1 × 108 bacterial cells/mL) of C. albicans was prepared in a 96-well plate and incubated on shaker at 37 °C in 100% humidity to allow fungal biofilm formation in infected dentin slices (n = 98). The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of AgNPs alone or with Ca(OH)2 were determined. The samples were separately placed in 24-well tissue culture plates and divided into three experimental groups (0.03, 0.04, and 0.06) and three control groups; negative (saline) and positive chlorhexidine gel and Ca(OH)2. Quantitative measurements of fungal activity by XTT colorimetric assay and qualitative measurements using confocal laser microscopy and scanning electron microscopy were performed. The cell viability of C. albicans in the experimental groups was significantly reduced compared to the negative control group. The combination of (AgNPs (0.04%) and Ca(OH)2) was the most potent against C. albicans. The findings demonstrated that combining silver nanoparticles with Ca(OH)2 was more effective against C. albicans biofilm compared to Ca(OH)2 alone, suggesting a combing effect.

Agglomeration inhibition mechanism of SiO2 in the Ca(OH)2/CaO thermochemical heat storage process: A reactive molecular dynamics study

As a promising thermochemical heat storage material, the Ca(OH)2/CaO can be agglomerated after repeated heat storage cycles, which will affect its performance severely. Experimental evidence indicated that the dopant of SiO2 particles alleviated the agglomeration phenomenon of Ca(OH)2/CaO. However, the mechanisms have not been clarified in theory, including the agglomeration of Ca(OH)2/CaO and the agglomeration inhibition of SiO2. Investigating these mechanisms is important for the broad application of Ca(OH)2/CaO thermochemical heat storage technology. In this paper, reactive molecular dynamics is employed to simulate and quantify the agglomeration of Ca(OH)2 and the inhibition by SiO2 during the heat storage process. Then, the agglomeration phenomena under the two processes are quantitatively described. The mechanisms are analyzed by using the parameters of kinetics and thermodynamics. From the phenomenological analysis, smaller size changes, larger mass center distances, and smaller atomic displacements indicate that SiO2 doping reduces the tendency of nanoparticles to agglomerate into a larger cluster. From the kinetic perspective, the diffusion of pure Ca(OH)2 clusters conforms to viscous flow, while the diffusion of the SiO2-doped clusters is close to surface diffusion. The dopant of SiO2 increases the activation energy of the diffusion process, which would increase the atomic mobility resistance and thus inhibit the agglomeration. From the thermodynamic perspective, cluster agglomeration is mainly caused by the work done by van der Waals forces, which leads to a decrease in potential energy, especially surface potential energy. By doping SiO2, the interatomic van der Waals forces are increased, which lowers the stable potential energy surface of the clusters, thereby obtaining a more stable structure to inhibit agglomeration.

Remarkable low-temperature dehydration kinetics of rare-earth-ion-doped Ca(OH)2 for thermochemical energy storage

Thermochemical energy storage based on dehydration-hydration of Ca(OH)2/CaO reversible reaction is considered a promising strategy to address the intermittency of solar thermal energy due to its extremely high storage density, possibility of seasonal heat storage, and low cost. However, conventionally-used Ca(OH)2 particles suffer from instabilities and poor multi-cycle performance at high temperature, which limits their applications. Here, we propose rare-earth-ion-doped Ca(OH)2 materials for thermochemical energy storage at reduced dehydration temperature through extensive DFT computational screening. Rare-earth elements, Sc, Y, La, Gd and Lu, -doped Ca(OH)2 exhibit lower decomposition barrier in comparison to the Ca(OH)2 without doping. The Sc-doped Ca(OH)2 shows the significantly reduced onset temperature of ∼326 °C, which is 50 °C lower than that of the pure Ca(OH)2. Importantly, more than 3-fold increase in the dehydration rate and excellent stability during multi-cycles of the compositions at 320 °C is reached by the doping of Sc or Y into Ca(OH)2. The working performance makes this material a practical alternative to realize stable high-density solar thermal energy storage.

Fabrication of MgO nanorods blended cellulose acetate-based mixed matrix membranes for selective gas separation of H2/CH4, CO2/CH4 and H2/CO2: Effect of loading and pressure

The growing interest in polymer-based mixed matrix membranes (MMMs) in the field of gas separation encouraged the authors to fabricate MgO nanorods and cellulose acetate (MgO-X/CA) MMMs for the separation of H2/CH4, CO2/CH4, and H2/CO2 gases. The facile solution-casting, followed by solvent evaporation technique, was applied to fabricate MMMs. FE-SEM, EDS, FT-IR, XRD, DSC, and TGA characterization techniques were used to investigate the physico-chemical properties of fabricated MMMs, whereas the gas transport properties of MMMs were investigated using a gas permeation setup. Upon uniform MgO nanorods incorporation in CA polymer, the gas permeation through MMMs is improved due to disruption of the polymer chain. The influence of feed pressure and various loadings of nanorods (5, 10, and 15 wt%) on gas permeability and selectivity of CA based MMMs were investigated at 25 °C and 1–4 bar gas pressure. Based on the results, the MgO-15/CA MMMs achieved the highest H2 permeability of 77.80 Barrer which is higher than pure CA by 45%, with a two-fold increase in H2/CO2 selectivity and unchanged H2/CH4 selectivity. Meanwhile, MgO-5/CA MMMs revealed the highest CO2 permeability of 62.90 Barrer with an increased in CO2/CH4 selectivity from 22.30 to 24.30.

Influence of Ca doping in structural, electronic, optical and mechanical properties of Ba1−xCaxTiO3 perovskite from first-principles investigation

Nowadays, perovskite materials are well known for electronics and optoelectronics applications. We have investigated a potential candidate for those applications to compare the applicability in optoelectronics, photorefractive and photovoltaic (PV) devices. The systematic comparative study of the structural, electronic, optical, mechanical, and thermodynamic properties of pure BaTiO3 and Ca doped BaTiO3 (Ba1−xCaxTiO3 where x = 0.125, 0.25, 0.375, 0.500, 0.625) perovskite have been carried out using first-principles and density-functional-theory calculations as recently this material was mostly experimented. The measured structural parameters from the geometrically optimized structure of cubic BT ceramic compared with the other theoretical values. A crystal phase transition occurs when doping content x = 0.25. The electronic band structure shows that the nature of the bandgap is changed from indirect bandgap to direct bandgap energy at G-point after doping the Ca atom into BaTiO3 (BT) crystal. Doping of Ca into BT has led to bandstructure modification including conduction band (CB) shifting toward the higher energy level. Electronic properties have been reported to examine the contribution of different orbitals to the CB and to the valance band (VB). This study investigated the modification of optical properties such as absorption, reflectivity, refractive index, extinction coefficient, conductivity, dielectric function and loss function at the energy range from 0 to 30 eV. The prominent absorption peak and optical energy were observed at the UV light energy region. Based on the optical behavior of the material this theoretical research suggests that the doped BT solution is a suitable candidate for photorefractive and optoelectronic devices. Different elastic constants reveal mechanical stability and the existence of the covalent bond of those compounds. Debye temperature increases with doping content. Hence modification of BaTiO3 crystal by Ca atom significantly develop various properties that led it to multifunctional applications.

Early Predictors of Future Disability in Stiff Person Syndrome Spectrum Disorders (S40.001)

<h3>Objective:</h3> Assess for early predictors of future disability in a large cohort of individuals with stiff person syndrome spectrum disorders (SPSD). <h3>Background:</h3> SPSD are rare disorders with an increasing spectrum of phenotypes. There is a paucity of data identifying whether early predictors for future disability exist. <h3>Design/Methods:</h3> Retrospective review of medical records from 1997–2022 at Johns Hopkins yielded 235 individuals with SPSD. Clinical phenotypes were assigned: classic SPS (torso/back and limb), partial-SPS (limb, trunk), SPS-plus (classic features with cerebellar/brainstem findings), pure cerebellar ataxia (CA, without classic features), and progressive encephalomyelitis with rigidity and myoclonus (PERM). Outcomes were modified Rankin scale (mRS) and use of assistive device for ambulation at last follow-up. Multivariate logistic regression was used to assess for significant predictors of outcomes. <h3>Results:</h3> Mean age at symptom onset was 44 years (SD 14 years), and the majority were white (69%) and female (75%). Mean follow up was 9.8 years and mean disease duration was 9.7 years. Phenotype breakdown: 154 classic SPS, 45 SPS-plus, 16 PERM, 11 pure CA, and 9 partial-SPS. The mean mRS was 2.5. Over 70% required assistive devices for ambulation. Female sex (OR 2.08, CI 1.06–4.11, p=0.03), initial symptom of brainstem/cerebellar (OR 4.41, CI 1.63–14.33, p=0.006), and no immunotherapy in the first three years from symptom onset (OR 2.22, CI 1.09–4.55, p=0.03) predicted poorer outcome by mRS. Female sex (OR 1.99, CI 1.01–3.01, p=0.05), Black race (OR 4.14, CI 1.79–10.63, p=0.002), initial symptom of brainstem/cerebellar (OR 2.44, CI 1.04–7.19, p=0.04), and no immunotherapy in the first three years from symptom onset (OR 1.27, CI 1.06–1.52, p=0.007) predicted poorer outcome by use of assistive device for ambulation. <h3>Conclusions:</h3> Our study identified specific clinical and demographic features associated with future disability in SPSD. Further studies are needed to assess if treating subgroups of SPSD more aggressively will help long-term outcomes. <b>Disclosure:</b> The institution of Dr. Wang has received research support from Genentech. Miss Hu has nothing to disclose. Dr. Mukharesh has nothing to disclose. Dr. Aljarallah has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for Novartis. Dr. Aljarallah has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for Biogen. Dr. Aljarallah has received personal compensation in the range of $0-$499 for serving on a Speakers Bureau for Sanofi Genzyme. Dr. Reyes-Mantilla has nothing to disclose. Mr. Comisac has nothing to disclose. Alexandra Balshi has nothing to disclose. Danielle Obando has nothing to disclose. Sarah Snoops has nothing to disclose. The institution of Dr. Fitzgerald has received research support from NIH. The institution of Dr. Fitzgerald has received research support from National MS Society. Dr. Newsome has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Autobahn. Dr. Newsome has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Biogen. Dr. Newsome has received personal compensation in the range of $10,000-$49,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Genentech. Dr. Newsome has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Novartis. Dr. Newsome has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for EMD Serono. Dr. Newsome has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Greenwich Biosciences. Dr. Newsome has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Bristol Myers Squibb. Dr. Newsome has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Horizon Therapeutics. The institution of Dr. Newsome has received research support from Biogen. The institution of Dr. Newsome has received research support from Genentech/Roche. The institution of Dr. Newsome has received research support from Department of Defense. The institution of Dr. Newsome has received research support from Patient Centered Outcomes Research Institute. The institution of Dr. Newsome has received research support from National MS Society. The institution of Dr. Newsome has received research support from The Stiff Person Syndrome Research Foundation. Dr. Newsome has received personal compensation in the range of $5,000-$9,999 for serving as a Clinical adjudication committee member for clinical trial with medDay Pharmaceuticals. Dr. Newsome has received personal compensation in the range of $10,000-$49,999 for serving as a Lead PI for Clinical Trial with Roche.

Biomimetic Mineralization of Fibrillar Collagen with Strontium-doped Hydroxyapatite

Fibrillar collagen structures mineralized with hydroxyapatite using the polymer-induced liquid precursor (PILP) process have been explored as synthetic models for studying biomineralization of human hard tissues and have also been applied in the fabrication of scaffolds for hard tissue regeneration. Strontium has important biological functions in bone and has been used as a therapeutic agent for treating diseases that result in bone defects, such as osteoporosis. Here, we developed a strategy to mineralize collagen with Sr-doped hydroxyapatite (HA) using the PILP process. Doping with Sr altered the crystal lattice of HA and inhibited the degree of mineralization in a concentration-dependent manner, but did not affect the unique formation of intrafibrillar minerals using the PILP. The Sr-doped HA nanocrystals were aligned in the [001] direction but did not recapitulate the parallel alignment of the c-axis of pure Ca HA in relation to the collagen fiber long axis. The mimicry of doping Sr in PILP-mineralized collagen can help understand the doping of Sr in natural hard tissues and during treatment. The fibrillary mineralized collagen with Sr-doped HA will be explored in future work as biomimetic and bioactive scaffolds for regeneration of bone and tooth dentin.

Preparation and Characterization of Cellulose Acetate-Hydroxyapatite (CA-HA) Composite Membrane for Ultrafiltration Process

A composite material is of two or more combined constituents with disparate properties and forming an inseparable component with novel characteristics. This study was aimed to acquire cellulose acetatehydroxyapatite (CA-HA) composite membrane and apply it in an ultrafiltration process. HA was synthesized hydrothermally from pre-calcined-eggshell calcium oxide. The CA-HA composites were prepared by addition of HA to give final HA composition of 0, 4 and 5% (w/w). The addition of HA altered CA morphologies and constricted the porous of CA-HA over the pure CA. The tensile strength analysis suggested that CA with 4% and 5% HA showed increasing tensile strength form 0.15 MPa for pure CA to 0.35 and 0.2 MPa respectively.

Direct and easily prepared nanocomposite impurity-free hydroxyapatite derived from CKD as an effective catalyst for trans-2-butene production

This research is regarded as the first successful attempt at directly producing highly pure nanocomposite hydroxyapatite (HAPT) from cement kiln dust (CKD) using a cost-effective preparation method. The crystallite size of HAPT was 23.6 nm and showed a hierarchical mesoporous unit with a Ca-deficient structure according to SEM-EDX analyses. HAPT exhibits a high population of different acidic sites, i.e. weak, moderate and strong acidic sites, as determined by TG and DSC-TPD experiments using tetrahydrofuran as a probe molecule. The wide range of acidic sites over HAPT is clearly and positively enhanced its catalytic activity during the conversion of sec-butanol to trans-2-butene. In addition, our prepared HAPT demonstrated greater catalytic activity when sec-butanol was converted using air as a carrier rather than N2-gas. A comparison between the catalytic activity of HAPT prepared from the waste CKD and pure Ca(NO3)2 was also conducted, showing HAPT derived from waste streams with higher catalytic activity.

Investigating the hygroscopicities of calcium and magnesium salt particles aged with SO2 using surface plasmon resonance microscopy

The hygroscopicities of calcium and magnesium salts strongly affect the environment and climate, but the aging products of these salts at high relative humidities (RHs) are still poorly understood. In this study, surface plasmon resonance microscopy (SPRM) was used to determine the hygroscopic growth factors (GFs) of Ca(NO3)2 and Mg(NO3)2 separately or mixed with galactose at different mass ratios at different RHs before and after aging. For all particles, the measured GFs showed no indication of deliquescence across the range of RHs tested, and overall hygroscopicity was clearly lower after than before aging. The Ca(NO3)2 and Mg(NO3)2 GFs at 90 % RH were 1.80 and 1.66, respectively, before aging and 1.33 and 1.42, respectively, after 4 h aging, meaning aging decreased the GFs by 26.11 % and 14.46 %, respectively. Aging decreased the hygroscopicity because insoluble or sparingly soluble substances (CaSO3, CaSO4, MgSO3) formed and strongly changed the overall hygroscopicity. For bicomponent aerosols with different mass ratios, the GFs (calculated using the Zdanovskii-Stokes-Robinson method) of the other components except galactose at 90 % RH after 1 h aging were all lower, respectively, than the measured GFs of pure Ca(NO3)2 and Mg(NO3)2 after aging for 1 h, especially with the mass ratio of 1:2, their GFs have decreased by 14.63 % and 7.50 %, respectively. Subsequently, Ion chromatograms indicated that the peak area ratio of SO42− to NO3− ratios were higher for the aged bicomponent particles than aged single-component particles, possibly because adding galactose improved the gas–liquid state stability during drying after the aging process and therefore promoted nitrate consumption and sulfate formation. The results indicated that organic components may play important roles in heterogeneous reactions between trace gases and multicomponent aerosols and should be considered in evaluating the impacts on submicron aerosol composition of high atmospheric SO2 concentrations at high humidities.

New Perspectives for the Consolidation of Mural Paintings in Hypogea with an Innovative Aqueous Nanolime Dispersion, Characterized by Compatible, Sustainable, and Eco-Friendly Features

Consolidation of mural paintings in hypogea is challenging because of their severe microclimatic conditions, characterized by high humidity levels, low air circulation, the presence of salts efflorescence, and the detrimental growth of biodeteriogen agents. Traditional consolidant products show significant drawbacks when used in hypogeum. Organic compounds, such as acrylic emulsions, are bio-receptive and some inorganic consolidants, such as silica-based products, show a lack of compatibility with the original substrate, which could lead to a reduction in permeability and an increase in the mechanical resistance of the external layer. The presence of solvents in their formulations, particularly short-chain alcohols that can activate germination of fungal spores, leads to the release of great amounts of volatile organic compounds, which are particularly harmful in the hypogeic environment. To solve these problems, restorers of the Istituto Centrale per il Restauro (ICR) decided to use a new aqueous nanolime dispersion, NANOLAQ, consisting of pure and crystalline Ca(OH)2 nanoparticles dispersed in water, produced by an innovative and sustainable patented procedure. After laboratory testing, the product has been applied on site, on a medieval mural painting in the Ss. Peter and Paul hypogeum in the UNESCO site of Matera (Italy), monitoring the performance in terms of cohesion of the paint layer and preservation of aesthetic features.

Calcium isotope ratio in kidney stones: preliminary exploration of mechanism from the geochemical perspective.

Stable calcium (Ca) isotope ratios are sensitive and radiation-free biomarkers in monitoring biological processes in human bodies. Recently, the Ca isotope ratios of bone, blood, and urine have been widely reported to study bone mineral balance. However, as a pure Ca crystallization product, there is no report on the Ca isotope ratios of kidney stones, even though the prevalence of kidney stones is currently on the rise. Here, we measured Ca isotope data of 21 kidney stone samples collected in Beijing, China. The δ44/42CaNIST 915a values ranged from 0.25‰ to 2.85‰ for calcium oxalate, and from 0.38‰ to 3.00‰ and 0.61‰ to 0.69‰ for carbonate apatite and uric acid, respectively. Kidney stones have heavier Ca isotope ratios than bone or blood, which is probably because complexed Ca contains more heavy Ca isotopes than free Ca2+. Ca isotope evidence suggests that magnesium (Mg) affects kidney stone formation, as the δ44/42CaNIST 915a value is inversely correlated with the Ca/Mg ratio. This study provides important preliminary reference values on the Ca isotopic composition of kidney stones and proposes a factor influencing Ca isotope fractionation in biological processes for future research.

Optimizing electrical and thermal transport properties of Ca3Co4O9 based thermoelectric materials by Ag and Fe co-addition

Ca 3-x Ag x Co 4-y Fe y O 9 (x=0, 0.05; y=0, 0.1, 0.2, 0.4) polycrystalline materials were prepared by sol-gel method with spark plasma sintering. The phase composition, microstructure and high temperature thermoelectric property of the bulk samples were systematically studied. The sintered Ca 3-x Ag x Co 4-y Fe y O 9 ceramics exhibit fine lamellar grain and dense morphology. Compared with single addition of Ag or Fe, appropriate co-additive amount of Ag and Fe can further increase electrical conductivity due to higher carrier concentration and mobility, while decreasing thermal conductivity by stronger phonon scattering. The coordinated regulation of electron and phonon transport is realized in Ca 2.95 Ag 0.05 Co 3.8 Fe 0.2 O 9 with the maximum ZT value of 0.25 at 1000 K, which is 34% larger than that of pure Ca 3 Co 4 O 9 . • Appropriate co-doping content of Ag and Fe in Ca 3 Co 4 O 9 can bring higher carrier concentration and mobility, while enhancing phonon scattering. • Simultaneously enhanced power factor and suppressed thermal conductivity can be achieved by Ag and Fe co-doping with appropriate doping contents. • Excessive doping of Fe would generate secondary phase FeO and deteriorate thermoelectric property.

Calcium hydroxide and porous silicon-impregnated silicon carbide-based composites for thermochemical energy storage

Thermal energy storage has a prospect for large-scale storage of renewable energy. Thermochemical energy storage using reversible gas–solid reactions can store thermal energy for unlimited periods with high energy density. Calcium hydroxide (Ca(OH)2), which is abundant and environmentally friendly, is one of the most promising materials for thermochemical energy storage systems. However, pure Ca(OH)2 powder has poor power density and bulk stability owing to its low thermal conductivity, volume change, and agglomeration over dehydration–rehydration cycles. Practical composites that can simultaneously overcome these problems have not been reported yet. This study combines Ca(OH)2 with ceramic foam and honeycomb structures of silicon-impregnated silicon carbide (Si–SiC) and demonstrates the improved power density and bulk stability of the resulting composites. The Si–SiC foam composite, loaded in a laboratory-scale fixed-bed reactor, exhibits a thermal discharging power density of 0.71 MW mbed−3, which is 1.6 times that of the pure Ca(OH)2 powder. In addition, the foam composite reduces the volume change by 80% and does not form centimeter-scale agglomerates even after 15 cycles, unlike the pure powder. The results suggest that embedding solid storage materials into thermally conductive open-cell foams can simultaneously enhance power density and bulk stability.

Preparation of Cellulose Acetate Nanocomposite Films Based on TiO2-ZnO Nanoparticles Modification as Food Packaging Applications

To develop bio-packaging materials, nanocomposite films of cellulose acetate reinforced with titanium dioxide and zinc oxide nanoparticles were prepared, by the casting method at different weight ratios of ZnO nanoparticles (1.5, 2, and 2.5) wt% and a constant weight ratio of 2 wt% TiO2. ZnO and TiO2 nanoparticles were tested using scanning electron microscopy (SEM). The mechanical properties (tensile strength and elongation) were improved at a fixed level of Cellulose Acetate+ 2% TiO2+1.5wt% ZnO loading. Beyond that level of loading, they decreased. The tensile strength was decreased due to some degrees of agglomeration of filler particles above a critical content. Fourier-Transform Infrared Spectroscopy (FTIR) was conducted to reveal the microstructures and chemical composition of as-prepared composite films. The wettability of the films was also determined by the sessile drop method. An increase in contact angle was also observed by the addition of ZnO content from 70.6° to 77.1° compared to pure Cellulose Acetate, which indicated a value of 61.3°. Antibacterial activity against Escherichia coli and Staphylococcus aureus was enhanced after incorporation of ZnO-TiO2 compared with pure CA. The enhanced wettability and antibacterial activity of the prepared films suggest that they could be used for packaging applications.