Metals Rb Research Articles

Discovery and genesis of high-temperature geothermal energy adjacent to the South Tibetan Detachment System, central Himalaya

The 193 °C geothermal fluids have been newly discovered in Lolo at the depth of 350 m through drilling in May 2024, identifying the occurrence of high-temperature geothermal energy adjacent to the South Tibetan Detachment System. Studies on such geothermal field will provide new insights into the distribution of high-temperature geothermal systems in Xizang. Here, we present element geochemistry (major and trace elements) and multi-isotope (H, O, and Sr) compositions of thermal spring, geothermal well, river, and snow waters to reveal the formation of the Lolo high-temperature geothermal system. The major elemental results of water samples show that the Lolo geothermal waters belong to Na-HCO3 type, mainly affected by carbonate dissolution, silicate weathering, and cation exchange through water-rock interaction. The positive correlations of trace alkali metals (Li, Rb, and Cs) and metalloid (B) with Cl indicate that these elements were derived from the same source, mainly released from Himalayan leucogranites with minor slate and limestone via water-rock reaction. The interpretation is further supported by varied Sr isotopic values recorded in geothermal waters. Combination of major and trace elements, and H-O isotopic results reveals that the geothermal waters were sourced from meteoric precipitation from the eastern parts of the region at an elevation of ∼4733 m, which were conducted along the WE-trending fault (F5). The temperature of deep geothermal reservoir was calculated to be 204–205 °C by using quartz geothermometers, and the temperature of shallow reservoir has been calculated to be 100–130 °C based on chalcedony geothermometers and computed mineral saturation index by PHREEQC. The shallow thermal fluids were suggested to be formed by mixing of deep thermal fluids with cold groundwater near to the surface, evidenced by positive linear correlations between B and Cl. The deep-circulated meteoric waters have been heated by partial melting and the circulation depth is up to ∼5 km. These new findings help us understand the formation of Lolo geothermal field and also provide guides in high-temperature geothermal resources exploration adjacent to the South Tibetan Detachment System.

Effects of heavy alkali metals (Rb, Cs) post-deposition treatments on CuInGaSe2 using a spin-coating technique

Abstract This study used a controlled environment to explore the post-deposition treatment (PDT) effects on CuInGaSe2 (CIGSe2) semiconducting thin films using a non-vacuum spin-coating technique for doping the CIGSe layers with Cs and Rb. The structural characterization confirmed the successful deposition of chalcopyrite structures with no phases belonging to any alkali metals after the PDT, with crystallite sizes in the range between 40-67 nm, and with a slight change in the X Ray Diffraction (XRD) peak positions indicating a change from copper-rich to copper-poor phases. The morphological studies confirmed the increase in grain sizes after the PDT. The EDS chemical studies showed that there is a reduction in the copper content after PDT. The topographical studies showed a change in the surface morphology with modifications of the grain parameters. In addition, the electrical characterization showed a significant increase of the effective carrier mobility after the treatments, consistent with the grain size increase observed by both microscopic (SEM and AFM) studies. Raman characterization of the CIGSe2 films showed the A1 optical phonon mode of CIGS chalcopyrite structures and peaks at lower frequencies belonging to ordered vacancy compounds (OVCs). The deconvolution of the Raman spectroscopy broad peaks for the CIGSe2 films after their PDT confirmed the formation of alk-InSe2 OVC phases on top of the absorber layer.

Structure of vanadia-titania catalysts doped with alkali metals according to solid-state NMR, ESR spectroscopies and DFT

In this work, V/M/TiO2 catalysts (M = Li, Na, K, Rb and Cs) were investigated with Solid-state nuclear magnetic resonance (SSNMR), electron paramagnetic resonance (ESR) and first-principles calculations. The total vanadium content corresponds to half monolayer (4 V atoms·nm−2 of TiO2 support surface), with V/M atomic ratio being 4/0.6. Static 51V and MAS 1H, 7Li, 51V, 23Na, 133Cs NMR spectra were acquired. Surface moieties of vanadium oxide on (001) anatase surface were modeled using density functional theory (DFT); their 51V NMR parameters were calculated with the Gauge-Including Projected Augmented Wave (GIPAW) method and compared to experimental data obtained with 51V SSNMR spectroscopy. It was found that mainly strongly bound vanadium sites (V3) are formed on anatase samples, located on TiO2 terminal oxygen atoms. Weakly bound vanadium sites (V1, V2) are formed on bridged anatase oxygen atoms. Supported alkali metals (Li, Na, K, Rb and Cs) on TiO2 were found to interact with protons located on the terminal and bridged TiO2 oxygen atoms. The relative ratio of weakly bound vanadium sites (V1, V2) increased on alkali-containing samples. Calculations performed showed lithium cation to prefer V-O-Ti or V-O-V bonds over VO, unsystematically deshielding vanadium nuclei. The presence of V3+ is likely to cause a loss of intensity in 51V NMR spectra.

Dinitromethyltetrazole (DNMT)-based energetic coordination polymers (ECPs) as lead-free primary explosives and laser initiators

A series of energetic coordination polymers has been synthesized by incorporating dinitromethyltetrazole with alkali metals (Na, K, Rb and Cs), which have potential applications in laser initiating high explosives.

Bioaccumulation, biomagnification, and ecological risk of trace metals in the ecosystem around oilfield production area: A case study in Shengli Oilfield.

The production for crude oil usually leads to contamination of the soil with trace metals and organic contaminants from spilled petroleum. Organic contaminants were generally paid more attention than trace metals in the oilfield pollution. Many studies have investigated the impacts of some petroleum hydrocarbon pollutants, however, the impacts and risk assessment of trace metals remain largely unexplored. Moreover, under some circumstances, the risks associated with trace metals are not necessarily lower than those associated with organic contaminants. This study aimed to investigate methods to evaluate the possible risks associated with 11 trace metals (Ti, Ba, Sr, Rb, V, Li, Mo, Co, Cs, Bi, and Tl) in soil and biota samples from the Shengli Oilfield using ICP-MS. The results showed that 11 trace metals in the surface soils exceeded the local background levels. The geo-accumulation index (Igeo) indicated that the soils had light-moderate to moderate contamination levels, with higher Igeo value of Ba, V, Li, Mo, Co, and Cs. The individual potential ecological risk indices ([Formula: see text]) demonstrated moderate Bi and Tl pollution in soils. Comparatively, the [Formula: see text] is recommended for the risk assessment of trace metals on the ecosystem around the oilfield area. Mo, Bi, and Sr easily accumulate in plants, as reflected by their bioaccumulation factor. Ti, Ba, V, Li, Co, Cs, Bi, and Tl exhibited considerable biomagnification, particularly in birds. In this study, trace metals showed considerable bioaccumulation and biomagnification, and the risks of these trace metals on the ecosystem around oilfield production area need more attention.

Associations between plasma metal/metalloid mixtures and the risk of central obesity: A prospective cohort study of Chinese adults

Central obesity has increased rapidly over the past decade and posed a substantial disease burden worldwide. Exposure to metals/metalloids has been acknowledged to be involved in the development of central obesity through regulation of cortisol, insulin resistance, and glucocorticoid receptor reduction. Despite the importance, it is lack of prospective study which comprehensively evaluate the relations between multiple metals exposure and central obesity. We explored the prospective associations of plasma metal concentrations with central obesity in a prospective study of the Dongfeng-Tongji cohort. The present study included 2127 participants with a 6.87-year mean follow-up duration. We measured 23 plasma metal/metalloid concentrations at baseline. The associations between metals and incident central obesity were examined utilizing the Cox proportional hazard regression in single and multiple metals models. Additionally, we applied elastic net (ENET), Bayesian kernel machine regression (BKMR), plasma metal score (PMS), and quantile-based g-computation (Qgcomp) models to explore the joint associations of metal mixtures with central obesity. After adjusting potential confounders, we found significant associations of plasma manganese (Mn) and thallium (Tl) concentrations with a higher risk of central obesity, whereas plasma rubidium (Rb) concentration was associated with a lower risk of central obesity both in single and multiple metals models (all FDR <0.05). The ENET and Qqcomp models verified similar metals (Mn, Rb, and Tl) as important predictors for central obesity. The results of both BKMR model and PMS suggested cumulative exposure to metal mixtures was associated with a higher risk of central obesity. Our findings suggested that co-exposure to metals was associated with a higher risk of central obesity. This study expands our knowledge that the management of metals/metalloids exposure may be beneficial for the prevention of new-onset central obesity, which may subsequently alleviate the disease burden of late-life health outcomes.

Analysis of Heavy Metals and Other Elements in Soil Samples for its Physicochemical Parameters Using Energy Dispersive X-Ray Fluorescence (EDXRF) Techniques

The present study was conducted to determine the physicochemical properties and the composition of trace elements of soil samples in agriculture lands. This study has been designed to analyze heavy metal contaminations in 12 soil samples collected at a depth 0-20 cm from the agriculture areas of Munshiganj using Energy Dispersive X-Ray Fluorescence (EDXRF) spectroscopy. This study revealed that the maximum Ca, Ti, Mn, Fe, Cu, Zn, Rb, Sr, and Pb contents in soil samples were 76293, 3911, 534, 44652, 57.50, 532, 101.45, 242.11 and 39.31 mg/ kg respectively. A physicochemical study of soil is based on various parameters like soil PH, electrical conductivity (EC), TDS mg/L, Salinity. The value of soil PH found to be 7.53 to 9.24, conductivity was ranging from 22.4-66.5 μs, Total Dissolved Solid (TDS) was ranging from 13.39-37.70mg/L and salinity was ranging 22.40-66.50 μs. Along with the experimental data, several environmental indices (Contamination factor, geo-accumulation index, enrichment factor, pollution load index, Quantification of Anthropogenic Concentration of Metal (QoC) have been identified for comprehensive assessment of our study site, which suggesting that these heavy metals Ca, Ti, Mn, Fe, Cu, Zn, Rb, Sr, and Pb might come in the samples due to anthropogenic activities.

Heavy Metal Concentration in Harmattan Dust across Selected Stations in Nigeria

Abstract: The atmospheric assessment of elements and heavy metals concentrations contained in Harmattan dust samples is addressed in this research. From November 2017 to March 2018, suspended Harmattan dust was sampled using locally constructed Australian model gauges installed at each sampling points (Iwo, Oyo, Ilorin, Minna, Abuja, Lafia, and Jos). The gauges used stood around 5.0 meters tall and were made of 10.0 mm plastic bowls installed on a plastic container that was encased in a metal shell for support and stability. The concentrations of various elements and heavy metals included in suspended Harmattan dust across selected Nigerian cities were assessed using particle-induced x-ray emission (PIXE) technology. The samples were subjected to statistical analysis using the ANOVA test in order to discover the significant differences between the positions of the elements in the sample. The suspended Harmattan dust samples revealed the presence of the following eighteen elements: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Rb, Sr, and Zr. Particle-induced x-ray emission (PIXE) demonstrated that these elements are present in various amounts. The samples contain both heavy metals (Ti, Cr, Mn, Fe, Cu, Zn, and Zr) and non-heavy metals (Na, Mg, Al, Si, Cl, K, Ca, Rb, and Sr). The study’s results indicate that the presence of heavy metals in Harmattan dust can be attributed to various activities within the country. Consequently, it is advised that further research be conducted in order to raise public awareness about environmental issues. Keywords: Harmattan, PIXE, Elements, Dust, Heavy metals.

A sustainable approach to managing city park waste through biochar as a renewable energy source

An abundant natural resource known as lignocellulosic biomass is seen to be a promising and sustainable alternative to renewable energy. A carbon-rich, porous substance called biochar is created when biomass is thermally decomposed during pyrolysis procedures in order to make biofuels. Biochar can be made in big industrial facilities or on a local scale. In order to limit the usage of fossil fuels and find a solution for managing urban park garbage, this project will examine the potential of biochar made from waste from city parks as a renewable energy source. A 25-gram natural zeolite catalyst was used to produce biochar at temperatures between 100 and 500 °C with sample weights of 50, 100, 150, and 200 grams. Calorimetric analysis, FTIR analysis, SEM analysis, XRF analysis, ultimate analysis, and proximate analysis are used to characterize the product. The results showed that the zeolite process produced the maximum calorific value of biochar at 6009.8 cal/gram, the highest yield of biochar at 200 °C, and the weight of 50 grams of biomass without a catalyst at 96%. Aliphatic OH and CH groups associated with phenols, alcohols, and carboxylic acids can be seen using FTIR analysis. Large holes can be seen in leaf litter biochar according to SEM examination. For biochar products, the XRF examination of the metal elements Al, Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Co, Zn, Rb, Sr, Na, Mg, Sr, and Pb is within the permitted limits. Leaf waste can be converted into a non-toxic renewable energy source because biochar has a low sulfur concentration of 4.0%. The findings of this study are anticipated to fill in some gaps left by earlier studies, particularly with regard to the use of garbage from municipal parks and the advancement of renewable energy sources..

Centrosymmetric Rb2Sb(C2O4)2.5(H2O)3 and Noncentrosymmetric RbSb2(C2O4)F5: Two Antimony (III) Oxalates as UV Optical Materials.

Herein, we have successfully synthesized two rubidium antimony (III) oxalates, namely, Rb2Sb(C2O4)2.5(H2O)3 and RbSb2(C2O4)F5, utilizing a low-temperature hydrothermal method. These two compounds share a similar chemical composition, consisting of Sb3+ cations with active lone pair electrons, alkali metal Rb+ ions, and planar π-conjugated C2O42- anions. However, they exhibit different symmetries, Rb2Sb(C2O4)2.5(H2O)3 is centrosymmetric (CS), while RbSb2(C2O4)F5 is noncentrosymmetric (NCS), which should be caused by the presence of F- ions. Notably, the NCS compound, RbSb2(C2O4)F5, demonstrates a moderate second-harmonic generation (SHG) response, approximately 1.3 times that of KH2PO4 (KDP), and exhibits a large birefringence of 0.09 at 546 nm. These characteristics indicate that RbSb2(C2O4)F5 holds promising potential as a nonlinear optical material for ultraviolet (UV) applications. Detailed structural analysis and theoretical calculations confirm that the excellent optical properties arise from the synergistic effects between Sb3+ cations with SCALP and planar π-conjugated [C2O4]2- groups.

Investigation of electronic and optical properties of alkali atom doped CuInSe2 using density functional theory

In this study, the effect of alkali metal (Rb, Cs) doping on the electronic structure of CuInSe2 chalcopyrite have been investigated. The electronic structure of pure and doped chalcopyrites has been interpreted in terms of energy bands and density of states. The doping of Rb and Cs increases the band gap of CuInSe2 from 0.81 eV and attains its maximum value of 1.16 eV with 25% doping of Rb at Cu site. The forbidden gap of doped compounds is found to be suitable for optoelectronic and photovoltaic applications. Therefore, the investigations of various optical properties such as, dielectric tensors, absorption, reflection and refraction spectra, for Cu1−xAxInSe2 (A = Rb, Cs; x = 0, 0.125 and 0.25) compounds are performed to understand the optical performance of all these compounds. The imaginary part of dielectric tensor of pure and doped CuInSe2 are explained with the help of the various inter-band transitions. The refractive index for CuInSe2 is found to be 2.60 which reduces to 2.40 and 2.53 for Cu0.75Rb0.25InSe2 and Cu0.75Cs0.25InSe2 compounds, respectively. All investigations for Cu1−xAxInSe2 (A = Rb, Cs; x = 0, 0.125 and 0.25) compounds have been carried out using density functional theory. Present study shows that doping of Rb and Cs enhances the optoelectronic response of CuInSe2 for its utilization in photovoltaic and optoelectronic applications.

An integrated overview of metals contamination, source-specific risks investigation in coal mining vicinity soils.

Heavy metals in soil are harmful to natural biodiversity and human health, and it is difficult to estimate the effects accurately. To reduce pollution and manage risk in coal-mining regions, it is essential to evaluate risks for heavy metals in soil. The present study reviews the levels of 21 metals (Nb, Zr, Ag, Ni, Na, K, Mg, Rb, Zn, Ca, Sr, As, Cr, Fe, Pb, Cd, Co, Hg, Cu, Mn and Ti) in soils around Barapukuria coal-mining vicinity, Bangladesh which were reported in literature. An integrated approach for risk assessments with the positive matrix factorization (PMF) model, source-oriented ecological and health hazards were applied for the study. The contents of Rb, Ca, Zn, Pb, As, Ti, Mn, Co, Ag, Zr, and Nb were 1.63, 1.10, 1.97, 14.12, 1.20, 3.13, 1.22, 3.05, 3.85, 5.48, and 7.21 times greater than shale value. About 37%, 67%, 12%, and 85% of sampling sites posed higher risks according to the modified contamination factor, Nemerow pollution index, Nemerow integrated risk index, and mean effect range median quotient, respectively. Five probable metal sources were computed, including industrial activities to coal mining (17%), agricultural activities (33%), atmospheric deposition (19%), traffic emission (16%), and natural sources (15%). Modified Nemerow integrated risk index reported that agricultural activities, industrial coal mining activities, and atmospheric deposition showed moderate risk. Health hazards revealed that cancer risk values computed by the PMF-HHR model with identified sources were higher than the standard value (1.0E-04) for children, adult male, and female. Agricultural activities showed higher cancer risks to adult male (39%) and children (32%) whereas traffic emission contributed to female (25%). These findings highlight the ecological and health issues connected to potential sources of metal contamination and provide useful information to policymakers on how to reduce such risks.

Promotion effects of alkali metals on iron molybdate catalysts for CO2 catalytic hydrogenation

CO2 hydrogenation is an attractive way to store and utilize carbon dioxide generated by industrial processes, as well as to produce valuable chemicals from renewable and abundant resources. Iron catalysts are commonly used for the hydrogenation of carbon oxides to hydrocarbons. Iron-molybdenum catalysts have found numerous applications in catalysis, but have been never evaluated in the CO2 hydrogenation. In this work, the structural properties of iron-molybdenum catalysts without and with a promoting alkali metal (Li, Na, K, Rb, or Cs) were characterized using X-ray diffraction, hydrogen temperature-programmed reduction, CO2 temperature-programmed desorption, in-situ 57Fe Mossbauer spectroscopy and operando X-ray adsorption spectroscopy. Their catalytic performance was evaluated in the CO2 hydrogenation. During the reaction conditions, the catalysts undergo the formation of an iron (II) molybdate structure, accompanied by a partial reduction of molybdenum and carbidization of iron. The rate of CO2 conversion and product selectivity strongly depend on the promoting alkali metals, and electronegativity was identified as an important factor affecting the catalytic performance. Higher CO2 conversion rates were observed with the promoters having higher electronegativity, while low electronegativity of alkali metals favors higher light olefin selectivity.

English

The study aimed to assess concentrations of heavy metals in soil samples on both sides along the three Niles (Blue, White, and Nile Rivers) and Almogran area (Tuti Island) in Khartoum city (the capital of Sudan country) after the overflow season. Concentrations of heavy metals Br, Cu, Ni, Pb, Co, Rb, Cr, Zn, Zr, Sr, Mn, Ti, K, Ca, and Fe were determined using Xray fluorescence (XRF) techniques compatible with direct analysis of soils. The results showed that the element's concentration along the Blue Nile is higher than White Nile, Nile river, and Almogran area. In addition, Enrichment Factor (EF) and Geoaccumulation index (GI) factor was calculated, and both are in recommended ranges except EF for Ni high at Blue Nile 2.58, which is more than recommended value (2).

Hofmeister effects influence bulk nanostructure in a protic ionic liquid

HypothesisThe origins and behaviour of specific ion effects have been studied in water for more than a century, and more recently in nonaqueous molecular solvents. However, the impacts of specific ion effects on more complex solvents such as nanostructured ionic liquids remains unclear. Here, we hypothesise that the influence of dissolved ions on the hydrogen bonding in the nanostructured ionic liquid propylammonium nitrate (PAN) constitutes a specific ion effect. ExperimentsWe performed molecular dynamics simulations of bulk PAN and 1–50 mol% PAN-PAX (X = halide anions F−, Cl−, Br−, I−) and PAN-YNO3 (Y = alkali metal cations, Li+, Na+, K+ and Rb+) solutions to investigate how monovalent salts influence the bulk nanostructure in PAN. FindingsThe key structural characteristic in PAN is a well-defined hydrogen bond network formed within the polar and non-polar domains in its nanostructure. We show that dissolved alkali metal cations and halide anions have significant and unique influences on the strength of this network. Cations (Li+, Na+, K+ and Rb+) consistently promote hydrogen bonding in the PAN polar domain. Conversely, the influence of halide anions (F−, Cl−, Br−, I−) is ion specific; while F− disrupts PAN hydrogen bonding, I− promotes it. The manipulation of PAN hydrogen bonding therefore constitutes a specific ion effect – i.e. a physicochemical phenomena caused by the presence of dissolved ions, which are dependent on these ions’ identity. We analyse these results using a recently proposed predictor of specific ion effects developed for molecular solvents, and show that it is also capable of rationalising specific ion effects in the more complex solvent environment of an ionic liquid.

Settleable atmospheric particulate matter harms a marine invertebrate: Integrating chemical and biological damage in a bivalve model

Some atmospheric pollutants may affect aquatic ecosystems after settling, generating contamination, bioaccumulation, and threats to aquatic species. Metallurgical processes result in the emission of settleable atmospheric particulate matter (SePM), including metals and metalloids, along with rare earth elements (REE) that are considered emerging contaminants. We report the 30-day exposure of brown mussels (Perna perna) to SePM collected in a metallurgical area of southeast Brazil close to estuarine ecosystems, followed by a 30-day clearance period, to evaluate the toxic potential of SePM to this model mollusk. The bioaccumulation of 28 elements identified in SePM and the sublethal effects were evaluated. REEs were found in SePM (Ce, Y, and La). Significant bioaccumulation of eight metals (Fe, Ni, Cu, Zn, Rb, Sr, Cd, and Ba) was found in the bivalves and correlates with the cytotoxicity and genotoxicity, showing a dose-dependent mode and suggesting a pre-pathological condition that could lead to ecological disturbances over time. Conversely, the unchanged lipid-peroxidation level after SePM exposure could indicate the effectiveness of the antioxidant system in protecting gills and digestive glands. The clearance period was not enough to successfully reverse the negative effects observed. So far, the current results enhance the comprehension of the negative role of SePM on metal bioaccumulation and metal-induced toxicity to aquatic biota. Thus, this report adds innovative findings on the role of SePM in aquatic pollution in coastal areas affected by atmospheric pollution, which should be relevant for future public policies to verify and control the environmental pollution.

Gemological and Mineralogical Characteristics of Emerald from Ethiopia

Ethiopia has been gaining attention in recent years as an emerging source of high-quality emerald. Ethiopian emerald samples with different colors ranging from dark green to light green were selected to study the gemological properties, chemical composition, and spectral characteristics. The Ethiopian emeralds were examined using conventional gemological instruments, including X-ray fluorescence spectrometry, LA-ICP-MS, UV/Vis/NIR, infrared spectrometry, and Raman spectrometry, providing a wealth of data and research information related to Ethiopian emeralds. The EDXRF results show that the chemical composition of Ethiopian emeralds is distinctly regional compared to emeralds of Colombian origin, being low in Cr, low in V, and high in Fe. LA-ICP-MS results demonstrate consistent results for Cr (734.34 to 1644.3 ppmw), V (89.61 to 106.61 ppmw), and Fe (4468.04 to 5022.3 ppmw) based on the chemical composition analysis by EDXRF. In addition, the LA-ICP-MS assay revealed that the combination of alkali metals (Li, Na, K, Rb, and Cs) and some trace elements (Sc, V, Cr, and Fe) could distinguish the Ethiopian emeralds from those from other regions. The Ethiopian emerald had absorption of Fe2+, Cr3+, V3+, and Fe3+, and the typical absorption intensity of Fe2+ (around 850 nm) was higher than that of Fe3+ (around 371 nm) in the UV/Vis/NIR spectra. The infrared spectrum of samples indicated that the absorption of type II H2O was higher than type I H2O in the emeralds from Ethiopia, which is consistent with the high content of alkali metals detected by LA-ICP-MS that would lead to an increase in the content of type II H2O. The Raman spectra showed absorption at 410 cm−1, 569 cm−1, 687 cm−1, 995 cm−1, and 1067 cm−1, with an emerald species recognition pattern. The gas–liquid two-phase inclusions of the emerald in this area were mainly CO2 and H2O, and the samples contained typical dark inclusions of magnesium-rich biotite sheets that revealed the tectonic-magmatic-related geological environment in this region.

Systematic Theoretical Study of CO Activation over Clean and Potassium-Modified Transition Metals

By using the periodic density functional theory (DFT) method, the adsorption and activation of CO on clean and potassium-modified transition metals, which includes Fe(100), Co(0001), Ni(111)/(100), Cu(111), Ru(0001), Rh(111)/(100), Pd(111), and Pt(111) surfaces, have been investigated systematically. The calculation results show that the additive of potassium atoms greatly enhances the binding strength of CO and O while only slightly improving the adsorption of C atoms. Moreover, the activation energy of CO dissociation is decreased in the presence of potassium additive atoms. Our results indicate that the CO activity enhancement by the series of alkali metals (Li, Na, K, Rb, and Cs) on Ni(100) increases in the order of Li < Na < Cs < Rb = K. On the basis of the electronic structure and geometric analysis, the physical origin of the promotion effect has been clarified, and it can be attributed to the direct electron transfer between potassium and O atoms involved in CO. The effect of an external electric field on CO activation was also investigated, in which it was shown that a positive electric field accelerated CO activation by elongating the C–O bond and transferring electrons. It is obvious that CO adsorption is enhanced when the orientation of the external electric field is the same as the direction of charge transfer. At last, the promoting effect of potassium on CO activation drops as the oxide state of potassium increases due to the steric effect and direct chemical bonding.

Sustainable recovery of critical elements from seawater saltworks bitterns by integration of high selective sorbents and reactive precipitation and crystallisation: Developing the probe of concept with on-site produced chemicals and energy

The availability of raw mineral resources containing elements included in the Critical Raw Materials (CRMs) list is a growing concern for the European Union. Sea mining has been identified as a promising secondary source. In particular, brines obtained in solar saltworks (bitterns) contain relevant amounts of valuable CRMs such as Mg(II), B(III), other alkaline/alkaline earth metals (Rb(I), Cs(I), Sr(II)) and transition/post-transition elements (Co(II), Ga(III), Ge(IV)). However, the low concentration of some of these elements (µg/L) requires an effort to develop recovery routes that are sustainable and economically feasible where the required chemicals and energy are produced on-site from the saltworks bitterns (i.e. HCl and NaOH). Even the conventional recovery processes such as ion exchange, sorption and precipitation, which have proved to be competitive for metals recovery, are challenged in the case of Trace Elements (TEs). This work studies the recovery of TEs included in the CRMs list from saltworks bitterns after ion exchange processes. First, batch crystallisation and reactive precipitation were tested for some target elements in single-component solutions: Sr(II), Co(II), Ga(III), Ge(IV) and B(III). Then, the experiments were carried out with multi-component synthetic solutions assuming different scenarios of bittern streams coming out a selective extraction stage using sorption and ion exchange processes. The targeted elements were recovered except for Ge(IV), where alternative routes need to be evaluated, as its precipitation involves the use of tannic acid or sulphide solutions that could not be produced from the bitterns. However, a further concentration step would be necessary to achieve element concentrations closer to the mineral phases saturation. Moreover, model simulations were performed using the PHREEQC program, which provided a good prediction of the experimental trends obtained in most cases.

First-principles study of adsorption and migration of alkali and alkaline earth metals (Rb, Cs, and Ba) on graphene

The adsorption and migration characteristics of Rb, Cs, and Ba on pristine and defective graphene have been systematically investigated by utilizing the density functional theory (DFT) method, which could help address the challenges of developing novel anode materials of thermionic energy converters (TECs). In this work, we found that the work function of the adsorption system is lower as Cs is adsorbed on graphene compared with Rb and Ba, which indicates that the electron emission capability has been greatly improved. Computational results of defective graphene demonstrate that defect sites act as traps for metals. The diffusion near the Stone-Wales defect and vacancy is severely hindered and the migration barrier on the surface of B/O doped graphene is also slightly increased. Particularly, the work functions of all defective graphenes are significantly increased, which is attributed to the decrease in the probability of electric dipole formation and the increase of the absolute cohesive energy. O-containing defects are ubiquitous in graphene due to their low formation energies, and the lowest work function of defective graphene is 2.74 eV, which is reached after Cs adsorption at 2OC defect sites, whereas this is still expected to have detrimental effects on graphene-based anode materials.