Solubility Of Oxide Research Articles

Solubility of Rare Earth Oxides in Fused Alkali and Alkaline Earth Halides

Melts based on mixtures of alkali and/or alkaline earth halides are considered as prospective media for electrowinning rare earth metals as well as for pyrochemical reprocessing spent nuclear fuels. Fluoride or mixed fluoride-chloride baths can be operated at high temperatures yielding molten rare earth metals (REMs) thus simplifying separation of the metal and salt. One of the problems in using fluoride melts is possible formation of fluorine at the anode. This can be avoided by adding a rare earth oxide to the melt both as the source of REM and oxide ions. The latter will be oxidized to oxygen producing carbon mono- or dioxide at the anode. The limiting factor for feeding the electrolysis bath with REM oxides is their solubility in the halide melt.The aim of the present study was determining the effect of temperature and melt composition on solubility of REM oxides in fused halides. The experiments were performed in CaCl2–CaF2 mixtures containing 20 or 75 mol. % CaF2; BaCl2–BaF2 mixtures containing 15 or 73 mol. % BaF2; equimolar CaF2–BaF2 mixture and NaCl–NaF eutectic mixture (34 mol. % NaF). Solubility of REM oxides was determined by the method of isothermal saturation. Time required for reaching the equilibrium between solid REM oxides and fused salts was determined in a preliminary set of experiments. To compare the behavior of 4f- and 5f-elements, solubility of uranium dioxide was also measured.The measurements were performed at the temperatures up to 1400 oC under argon atmosphere. The lower limit of the temperature range varied from 700 to 1100 oC depending on the melting temperatures of the salt mixtures used. Oxides of yttrium, lanthanum, cerium, praseodymium, neodymium and samarium were selected for the study. To assess a possible mutual influence of rare earth elements on solubility of their oxides in fused salts the solubility of a mixture of REM oxides was determined in a separate series of experiments and concentrations of individual REMs in the melt was determined.Solubility of REM oxides increased with increasing temperature and an example of effect of temperature on solubility of neodymium oxide in various melts is shown in Fig.Fig. Concentration of neodymium in alkali and alkaline halide based melts saturated with Nd2O3. Melt: CaCl2–CaF2 20 mol. % (1); CaCl2–CaF2 75 mol. % (2); BaCl2–BaF2 73 mol. % (3); BaCl2–BaF2 15 mol. % (4); CaF2–BaF2 50 mol. % (5; and NaCl–NaF 34 mol. % (6). Figure 1

Oxide Sensor Development By Square Wave Voltammetry for Molten Fluoride Salts

A fundamental understanding of oxide concentration is critical for operation of advanced nuclear reactors which use molten salts. Molten fluoride salts have been proposed as fuel solvents, coolants, and tritium breeding blankets in fission and fusion nuclear reactors due to their high temperature operation and favorable neutron-interaction properties. An electrochemical sensor which can measure the real-time concentration of oxide anions in the salt melt could be used to identify air ingress to the system. Additionally, similar electrochemical analyses used in the development of a sensor could be used to study the fundamental properties and behavior of oxides in molten fluoride salts. These properties include the activity coefficient, diffusion coefficient, and solubility of oxides. Understanding of these properties could, in turn, inform sensor development.A further understanding salt chemistry can also help predict and control the effects of oxide concentration on salt corrosion. Material integrity under exposure to high-temperature molten salts is an impactful technical challenge for the design of nuclear reactors that employ molten salts. Oxide anion concentration and complexation of cations and anions in the melt can influence corrosion. Therefore, electrochemical oxide sensors for molten fluoride salts would be instrumental in corrosion studies. Fundamental understanding of oxide chemistry in fluorides would also advance understanding of corrosion mechanisms in fluoride salts.Cyclic voltammetry, square wave voltammetry, and chronopotentiometry have been previously used to study the electrochemical behavior of oxides in fluoride salt melts. Square wave voltammetry (SWV) is particularly useful in this application because it limits the noise caused by oxygen bubbling from the oxidation of O2- anions, as found by Massot et al.. Titrations of known additions of oxide to the melt have previously been used to show that the intensity of the SWV oxide oxidation peak is linear with oxide concentration.Oxides have yet to be studied electrochemically in 2LiF-BeF2 (FLiBe) or LiF-NaF-KF (FLiNaK) molten salts, which are of interest for nuclear reactors. FLiBe is a likely coolant and solvent candidate for molten salt nuclear reactors. FLiNaK has been studied as a surrogate salt with similar thermo-physical properties to FLiBe. It is easier to handle experimentally since it presents no beryllium health hazard, but its chemical and neutronic behavior are different. FLiNaK is often used in salt loops for reactor design, safety analysis, component testing, and corrosion testing. Therefore, availability of oxide electrochemical sensors for FLiBe and FLiNaK would be instrumental in reactor operation as well as reactor development.This talk will summarize the application of SWV to quantification of oxides in FLiBe and FLiNaK melts. It will also discuss the available chemical and thermodynamic information for oxides in FLiBe and FLiNaK. Ultimately, an understanding of oxide behavior and a quantification of oxide concentration in molten fluoride salts will aide in the development of an electrochemical sensor for detecting leaks in molten salt reactors.

Advanced and Intensified Seawater Flue Gas Desulfurization Processes: Recent Developments and Improvements

Seawater flue gas desulfurization (SWFGD) is considered to be a viable solution for coastal and naval applications; however, this process has several drawbacks, including its corrosive absorbent; low vapor loading capacity since the solubility of sulfur oxides (SOx) in seawater is lower than that of limestone used in conventional methods; high seawater flowrate; and large equipment size. This has prompted process industries to search for possible advanced and intensified configurations to enhance the performance of SWFGD processes to attain a higher vapor loading capacity, lower seawater flowrate, and smaller equipment size. This paper presents an overview of new developments as well as advanced and intensified configurations of SWFGD processes via process modifications such as modification and optimization of operating conditions, improvement of spray and vapor distributors, adding internal columns, using square or rectangular shape, using a pre-scrubber, multiple scrubber feed; process integration such as combined treatment of SOx and other gases, and waste heat recovery; and process intensification such as the use of electrified sprays, swirling gas flow, and rotating packed beds. A summary of the industrial applications, engineering issues, environmental impacts, challenges, and perspectives on the research and development of advanced and intensified SWFGD processes is presented.

A nanoscopic explanation of nitric oxide solubility in natural deep eutectic solvents

Since its discovery in December 2019, COVID-19 has been an unprecedented global threat. A massive collective scientific effort has been in place since the pandemic took off in order to put off its health threatening effects. The aim of this work is to evaluate the potential nitric oxide as a candidate therapeutics that can be considered for fighting against the severe effects of COVID-19. The findings of this work provide valuable molecular understanding on how nitric oxide behaves in close contact with natural deep eutectic solvents and this work paves the way towards enhancing bioavailibity of nitric oxide via liquid infusion through natural deep eutectic solvents. Nanoscopic explanation of nitric oxide interactions with L-Arginine based natural deep eutectic solvents are reported through findings obtained from density functional theory calculations and molecular dynamics simulations. Structural characteristics of the studied systems and critical interaction patterns of nitric oxide within proposed carrier medium are the main focus of the presented work. The results that are shared in this work can be considered fundamental scientific basis on increasing the mobility, availability and the accessibility of the nitric oxide, as it ameliorates pulmonary hypertension with pulmonary selectivity as well as improve cardiovascular health by providing protection against the initiation and progression of atherosclerosis in multiple proven ways.

Thermodynamics of high entropy oxides

With the hype of “high entropy” alloys and more recently, “high entropy” ceramics and “high entropy” oxides (HEOs), there has been a great push to investigate and characterize systems with 5 or more components. This push has been extremely beneficial for the materials community as it has led to the development of many new systems with targeted applications. However, with our desire to find “new” and “exotic” materials, we have not spent enough time to step back and think deeply about the fundamental thermodynamic constraints that will guide design of future HEOs. Here, we present data-driven discussions with examples that have been collected from the fields of geology and materials science over the past 50 years to highlight critical thermodynamic parameters and principles that can be used for the design of HEOs. The goal of HEOs is to push the limit of the number of components in a single-phase solid solution to achieve unique and tunable properties. True single-phase HEOs are stabilized if the positive entropy of formation more than compensates an unfavorable enthalpy of formation above some critical temperature, making the overall ΔGf negative i.e. the HEO phase is “entropy stabilized”. Under ideal mixing, the number of components in a solid solution does not affect the solubility of an additional component. In real systems, the types of additional components, their structural transformations, and their associated non-ideal interactions influence the solubility limit. Non-ideal interactions can lead to short- or long-range ordering that decreases the overall configurational entropy. Due to the ionic-covalent nature of oxides, this ordering is the norm, not the exception. In the limited cases where mixing is ideal, charge coupled substitutions can work to influence overall configurational entropy contributions due to unique crystallographic sites. Long-range ordering can be minimized by mixing oxide components that have similar charge or are isostructural. Most excitingly, is the realization that surface energies will drastically affect the stability of oxide polymorphs and solubility limits. Thus, nano-materials are an interesting and novel approach that will vastly extend the HEO engineering space. As one can see, there are many avenues for the design and development of “HEOs” that thermodynamics will allow, even though they all may not be driven explicitly by entropy.

Modification of Surface Properties of Colloidal Suspensions of NixOy-SiO2 Mixed Oxides with Different Ni Contents by the Adsorption Layers of Poly(Vinyl Alcohol)

The adsorption and electrokinetic properties of hybrid silica materials composed of nickel and silicon oxides (NixOy-SiO2), characterized by different contents of nickel oxide (from 0.5 to 3 mmol/g SiO2), were examined. These solids were also modified by poly(vinyl alcohol) to change their surface characteristics. The polymer is non-toxic and very well soluble in water. Due to incomplete hydrolysis of the polymer acetate groups, its macromolecules become negatively charged. The limited range of studied pH (6–10) resulted from high solubility of nickel oxide at more acidic pH values. The spectrophotometric, surface charge and electrophoretic measurements indicated that PVA exhibits higher adsorption affinity for the surfaces of mixed oxide with a larger content of nickel in its structure. Moreover, the presence of polymeric layers on the solid surface influences considerably the structure of electrical double layer formed at the mixed oxide-aqueous solution interface.

Chemical and Phase Equilibria in the Reaction between NO and O2 in the Presence of Water and CO2 at 298.15 K up to 3 MPa

New experimental data for cosolubility of carbon dioxide, nitric oxide, and nitrogen dioxide produced from the reaction in situ between nitric oxide and dioxygen in pure water at 298.15 K and up to 3 MPa are presented in this work. These data are essential to develop and validate thermodynamic models for CO2 and other gases capture and storage processes. In this work, measurements of carbon and nitrogen oxide solubilities in water are achieved; the liquid phase composition at the thermodynamic equilibrium was determined by analytical methods (ion chromatography), pH-metric titration, and a static synthetic method, and the gaseous phase composition was determined by two infrared spectrometers. The experimental apparatus and the analytical procedure were validated by studying the CO2 + water systems and comparing the experimental measurements with the literature data. On the other hand, the measurements of NO2 + water systems are original and do not exist in the literature. In order to study the behavior of the nitrogen dioxide in water, a suitable reaction mechanism was carefully chosen to predict the composition of the different nitrogen species (NO, NO2, N2O3, N2O4, HNO2, H+, NO2–, HNO3, and NO3–.) in the aqueous medium at 298.15 K. Then, a Henry constant for the studied nitric oxide systems was calculated. Some difficulties have been encountered in the stabilization of the nitrogen dioxide partial pressure due to its metastable conditions; therefore, data related to the Henry constant of this compound will not be reported.

Solubility of Rare Earth Oxides in Fused Alkali and Alkaline Earth Halides

Solubility of rare earth oxides in mixtures of alkali or alkaline earth halides was determined by the method of isothermal saturation at the temperatures up to 1400oC. The melts studied included CaCl2–CaF2 (20 or 75 mol. % CaF2), BaCl2–BaF2 (15 or 73 mol. % BaF2), equimolar CaF2–BaF2 and eutectic NaCl–NaF mixtures. Melting points of the salt mixtures were determined by differential thermal analysis and effect of added rare earth oxide on the melting point was considered. Solubility of yttrium, lanthanum, cerium, praseodymium, neodymium, and samarium oxides was determined. The effect of temperature, melt composition, and presence of a mixture of rare earth oxides on solubility was assessed.

Phase Equilibria in the ZrO2–CeO2–Yb2O3 System at 1100°C

Phase equilibria and structural transformations in the ternary ZrO2–CeO2–Yb2O3 system at 1100°C were studied by X-ray diffraction over the entire composition range. Fields of solid solutions based on monoclinic (M) and tetragonal (T) ZrO2 modifications, cubic (C) Yb2O3 modification, cubic fluorite-type (F) CeO2 (ZrO2) modification, and an intermediate Zr3Yb4O12 (δ) orthorhombic phase were found to exist in the system. The boundaries of the phase fields and lattice parameters of the phases were determined. The maximum solubility of cerium oxide in the δ phase was 4 mol.% at the CeO2–(60 mol.% ZrO2–40 mol.% Yb2O3) section. Solid solutions based on the tetragonal ZrO2 modification were established to form in the region with high ZrO2 content. The solubility of Yb2O3 in T-ZrO2 is low and comes to δ0.5 mol.%, which is evidenced by X-ray diffraction and microstructural analyses. The solid solutions based on the tetragonal ZrO2 modification cannot be quenched from high temperatures in the chosen cooling conditions. An infinite series of F-CeO2(ZrO2) solid solutions forms at 1100°C. The isothermal section of the ZrO2–CeO2–Yb2O3 system at 1100°C contains one three-phase region (F + C + δ), five single-phase regions (FCeO2(ZrO2), M-ZrO2, T-ZrO2, δ, C-Yb2O3), and five two-phase regions (C + F, C + δ, F + δ, F + T, T + M). New phases were not found in the system. The nature of phase equilibria in the ternary ZrO2–CeO2–Yb2O3 system at 1100°C is determined by the constitution of binary phase diagrams.

Dissolution behavior of metal oxide nanomaterials in cell culture medium versus distilled water

Solubility is a key criterion used in the hazard assessment of metal oxide–engineered nanomaterials (ENMs). The present study investigated solubility of CuO, NiO, and TiO2 ENMs compared with their bulk analogues in two aqueous media: water and Dulbecco’s modified Eagle’s medium (DMEM). Particle size distributions were characterized using dynamic light scattering (DLS) and tunable resistive pulse sensing (TRPS). After centrifugal separation, the dissolved metal fraction was quantified using inductively coupled plasma optical emission spectroscopy (ICP-OES). Overall, solubility of the metal oxides decreased in the order CuO ≥ NiO > TiO2 in both media, with each ENM displaying higher solubility than its bulk analogue. However, the metal oxide ENMs responded differently to the two aqueous media, when comparing their solubility using a low initial concentration (10 mg/L) versus a high initial concentration (100 mg/L). In DMEM, both nano-CuO and nano-NiO displayed increased solubility at the higher initial concentration by 3.8-fold and 1.4-fold, respectively. In water, this trend was reversed, with both nano-CuO and nano-NiO displaying increased solubility at the lower initial concentration by 3.3-fold and 1.2-fold, respectively. Interestingly, solubility trends displayed by nano-TiO2 were the opposite of those displayed by nano-CuO and nano-NiO. In DMEM, nano-TiO2 displayed decreased solubility at the higher initial concentration (0.3-fold), whereas in water, nano-TiO2 displayed increased solubility at the higher initial concentration (5.5-fold). These results show the importance of evaluating the solubility of ENMs in biologically relevant fluids at concentrations that correspond to toxicity assays, for the purposes of read-across and grouping ENMs.

Matrix-specific mechanism of Fe ion release from laser-generated 3D-printable nanoparticle-polymer composites and their protein adsorption properties

Nanocomposites have been widely applied in medical device fabrication and tissue-engineering applications. In this context, the release of metal ions as well as protein adsorption capacity are hypothesized to be two key processes directing nanocomposite-cell interactions. The objective of this study is to understand the polymer-matrix effects on ion release kinetics and their relations with protein adsorption. Laser ablation in macromolecule solutions was employed for synthesizing Au and Fe nanoparticle-loaded nanocomposites based on thermoplastic polyurethane (TPU) and alginate. Confocal microscopy revealed a three-dimensional homogeneous dispersion of laser-generated nanoparticles in the polymer. The physicochemical properties revealed a pronounced dependence upon embedding of Fe and Au nanoparticles in both polymer matrices. Interestingly, the total Fe ion concentration released from alginate gels under static conditions decreased with increasing mass loadings, a phenomenon only found in the Fe-alginate system and not in the Cu/Zn-alginate and Fe-TPU control system (where the effects were proportioonal to the nanoparticle load). A detailed mechanistic examination of iron the ion release process revealed that it is probably not the redox potential of metals and diffusion of metal ions alone, but also the solubility of nano-metal oxides and affinity of metal ions for alginate that lead to the special release behaviors of iron ions from alginate gels. The amount of adsorbed bovine serum albumin (BSA) and collagen I on the surface of both the alginate and TPU composites was significantly increased in contrast to the unloaded control polymers and could be correlated with the concentration of released Fe ions and the porosity of composites, but was independent of the global surface charge. Interestingly, these effects were already highly pronounced at minute loadings with Fe nanoparticles down to 200 ppm. Moreover, the laser-generated Fe or Au nanoparticle-loaded alginate composites were shown to be a suitable bioink for 3D printing. These findings are potentially relevant for ion-sensitive bio-responses in cell differentiation, endothelisation, vascularisation, or wound healing.

Hydroflux-assisted densification: applying flux crystal growth techniques to cold sintering

Hydroflux-assisted densification (HAD) is introduced as a method for low-temperature ceramic densification. HAD expands upon the cold sintering process, using an inorganic “hydroflux” secondary mass transport phase as opposed to the aqueous acidic, basic, or salt solutions that have been reported previously. Hydrofluxes combine ionic salts with sparing quantities of water to depress their melting points into the cold sintering range. The substantial solubility of many oxides in these hydrofluxes makes them appealing transport phases for an expanded cold-sinterable materials spectrum. This paper focuses on a hydroflux transport phase containing a eutectic mixture of NaOH and KOH (called “NaK”) for which particular nuances and properties are discussed. We demonstrate HAD in the ZnO system, highlighting the importance and impact of processing variables such as pressure, transport phase quantity, and water content. Additionally, we show densification of the oxide binaries Bi2O3, WO3, CuO, and MnO, and the functional ternaries Bi2WO6 and KxNa1-xNbO3 in the 200–300 °C range. This entire set is challenging to cold sinter using aqueous transport phases.

Quality reference values for heavy metals in soils developed from basic rocks under tropical conditions

Soil Quality Reference Values (QRV) refer to the natural heavy metal concentrations that is not influenced or is minimally influenced by anthropogenic activities. Such values are unique of each environment, and their extrapolation to different locations becomes inadequate. This research aimed to determine the natural concentrations of metals in soils (QRV) developed on essentially basaltic lithology and tropical conditions in the south of Brazil. Seventy-two soil samples from the Forest Conservation Areas in the west of the state of Paraná, Brazil, were obtained. The extraction and dosage of Ag, As, Ba, Cd, Cr, Cu, Mo, Ni, Pb, Sb, V, and Zn were carried out employing methods USEPA 3051a and ICP-OES. The QRV was set to 75th percentile of each element, from the detection and exclusion of the outliers. The natural concentration of all heavy metals was related to the geological context of the basaltic area in Brazil. There was no influence of the pedogenetic degree of soils on the natural heavy metal concentration. The only relevant process for reducing the natural heavy metal levels was the Fe and Mn oxide solubility promoted by hydromorphic conditions. Fe oxides had a significant role in the maintenance of structural and adsorbed heavy metal forms in soils. The results may help the research and monitoring of environmental heavy metals in soils developed from basalt under tropical conditions.

The Solubility of Gd<sub>2</sub>O<sub>3</sub> in K Cl-GdCl<sub>3</sub> Melts

The differential scanning calorimetry and the method of cooling curves are used to obtain data on liquidus temperatures of oxide-chloride systems Gd2O3 – K Cl - GdCl3. The solubility of gadolinium oxide in K Cl - GdCl3 melts has been studied. This information can be used for a developing process of the reduction of solid rare-earth oxides into their metals in molten salts.

Oxide Sensor Development By Square Wave Voltammetry for Molten Fluoride Salts

A fundamental understanding of oxide concentration is critical for operation of advanced nuclear reactors which use molten salts. Molten fluoride salts have been proposed as fuel solvents, coolants, and tritium breeding blankets in fission and fusion nuclear reactors due to their high temperature operation and favorable neutron-interaction properties. An electrochemical sensor which can measure the real-time concentration of oxide anions in the salt melt could be used to identify air ingress to the system. Additionally, similar electrochemical analyses used in the development of a sensor could be used to study the fundamental properties and behavior of oxides in molten fluoride salts. These properties include the activity coefficient, diffusion coefficient, and solubility of oxides. Understanding of these properties could, in turn, inform sensor development.A further understanding salt chemistry can also help predict and control the effects of oxide concentration on salt corrosion. Material integrity under exposure to high-temperature molten salts is an impactful technical challenge for the design of nuclear reactors that employ molten salts. Oxide anion concentration and complexation of cations and anions in the melt can influence corrosion. Therefore, electrochemical oxide sensors for molten fluoride salts would be instrumental in corrosion studies. Fundamental understanding of oxide chemistry in fluorides would also advance understanding of corrosion mechanisms in fluoride salts.Cyclic voltammetry, square wave voltammetry, and chronopotentiometry have been previously used to study the electrochemical behavior of oxides in fluoride salt melts. Square wave voltammetry (SWV) is particularly useful in this application because it limits the noise caused by oxygen bubbling from the oxidation of O2- anions, as found by Massot et al. Titrations of known additions of oxide to the melt have previously been used to show that the intensity of the SWV oxide oxidation peak is linear with oxide concentration.Oxides have yet to be studied electrochemically in 2LiF-BeF2 (FLiBe) or LiF-NaF-KF (FLiNaK) molten salts, which are of interest for nuclear reactors. FLiBe is a likely coolant and solvent candidate for molten salt nuclear reactors. FLiNaK has been studied as a surrogate salt with similar thermo-physical properties to FLiBe. It is easier to handle experimentally since it presents no beryllium health hazard, but its chemical and neutronic behavior are different. FLiNaK is often used in salt loops for reactor design, safety analysis, component testing, and corrosion testing. Therefore, availability of oxide electrochemical sensors for FLiBe and FLiNaK would be instrumental in reactor operation as well as reactor development.This talk will summarize the application of SWV to quantification of oxides in FLiBe and FLiNaK melts. It will also discuss the available chemical and thermodynamic information for oxides in FLiBe and FLiNaK. Ultimately, an understanding of oxide behavior and a quantification of oxide concentration in molten fluoride salts will aide in the development of an electrochemical sensor for detecting leaks in molten salt reactors.

Flux Balance Analysis for Media Optimization and Genetic Targets to Improve Heterologous Siderophore Production.

SummarySiderophores are small molecule metal chelators secreted in sparse quantities by their native microbial hosts but can be engineered for enhanced production from heterologous hosts like Escherichia coli. These molecules have been proved to be capable of binding heavy metals of commercial and/or environmental interest. In this work, we incorporated, as needed, the appropriate pathways required to produce several siderophores (anguibactin, vibriobactin, bacillibactin, pyoverdine, and enterobactin) into the base E. coli K-12 MG1655 metabolic network model to computationally predict, via flux balance analysis methodologies, gene knockout targets, gene over-expression targets, and media modifications capable of improving siderophore reaction flux. E. coli metabolism proved supportive for the underlying production mechanisms of various siderophores. Within such a framework, the gene deletion and over-expression targets identified, coupled with complementary insights from medium optimization predictions, portend experimental implementation to both enable and improve heterologous siderophore production. Successful production of siderophores would then spur novel metal-binding applications.

The solubility of Cu, Pb, As, Sb of copper-lead matte in the slag

An installation was developed and studies were carried out to determine the oxide solubility of copper, lead, arsenic, and antimony from copper-lead matte to slag under conditions of controlled values ​​of РО2=2,74*10-4 Pa and PS2=1,45*102 Pa, applicable to smelting reduction processes of copper-, lead-containing raw materials. It was found that the oxide solubility of copper from matte to slag increases monotonously with an increase of copper content in the matte. The presence of lead in the matte does not significantly affect the final solubility of copper in the slag. In a reducing atmosphere, the solubility of copper in slag is 0.28-0.35%, at the range of copper content of 30-45% in the matte, which is typical for industrial practice. The solubility of lead from copper-lead matte to slag has higher values ​​and increases to 1%. According to the results of mineralogical studies, there is no metallic form of arsenic in slags. Arsenic in slags was found in the form of oxide (As2O5) bound to silicate. Antimony in slag was found in oxide and metallic form. Moreover, the proportion of the last form in the slag prevails. It is shown that under reduction conditions the sublimation of arsenic and antimony from copper-lead matte is difficult. Equilibrium concentrations of As, Sb in the slag (0.17%) are achieved with their optimum content in the matte which is about 0.63%. Obtained results can be used to predict the loss of oxide solubility of copper and to develop optimal solutions to reduce the total loss of copper with slag during the reduction processes of separate processing of copper-, lead containing raw materials.

Geochemical constraints on supercritical fluids in geothermal systems

Supercritical fluids with temperatures of ~400–500 °C have been reported from several active geothermal fields worldwide. Although the utilization of such fluids may multiply power production from new and already exploited geothermal systems, the fluid origin and chemical controls on their composition remain unclear. We performed flow-through high-temperature (400–420 °C) experiments at 34–69 bar to study the chemical and mineralogical changes associated with supercritical fluid formation upon boiling of subcritical geothermal fluids of varying chemical composition. Based on geochemical modeling and laboratory results, we propose that an important mechanism of supercritical fluid formation is conductive heating and boiling of subcritical geothermal groundwater by a magmatic intrusion. Such supercritical fluids will display low concentrations of mineral-forming elements (Si, Na, K, Ca, Mg, Al), with their concentrations being controlled by the solubility of salts, oxides, and aluminum silicates in high-temperature (>400 °C) and low-density (ρ < 0.3 g cm−3) fluids. In contrast, supercritical fluids will show elevated concentrations of volatile elements (C, S, B) of crustal and/or mantle origin with their concentrations often being similar to those of subcritical geothermal fluids. Associated mineral deposition, dominated by quartz, aluminum silicates, and salts, may form in the vicinity of the intrusion. Comparison of the modeling and laboratory results with observed chemical composition of natural supercritical fluid discharges indicates that conductive heating and boiling of subcritical geothermal groundwater may indeed be the formation mechanism of such fluids observed for example at Krafla (Iceland), Menengai (Kenya), Los Humeros (Mexico), and Larderello (Italy) with an addition of volcanic gases in many cases. Metal and salt-rich supercritical fluids, for example, at Kakkonda (Japan), may also exist in geothermal systems. However, such supercritical fluids are considered to have been trapped upon crystallization of the magmatic intrusion.

Effect of Holding Temperature on Growth of Ruby Crystal Films via Molybdenum Trioxide Flux Evaporation–Solubility of Aluminum Oxide, Growth Rate, and Material Balance

Ruby (Al2O3:Cr) is used not only for jewelry but also in various industrial materials because of its excellent mechanical, optical, and chemical properties. Ruby crystals have been grown using the ...

Graphene oxide functionalized with oxygen-rich polymers as a pH-sensitive carrier for co-delivery of hydrophobic and hydrophilic drugs

In this work, a novel carrier based-on modified graphene oxide was designed for co-delivery of hydrophobic and hydrophilic anticancer drugs (curcumin (Cur) and doxorubicin (DOX) as the model of drugs). The hydroxyl groups at the edges of graphene oxide (GO) sheets were used as the initiation sites for growing poly(epichlorohydrin) (PCH) chains. Then, hyperbranched polyglycerol (HPG) was grafted on the hydroxyl end groups of PCH (PCH-g-HPG). Pendant chlorines in the main chain of GO-PCH-g-HPG were replaced with hydrazine. The modification of GO sheets with oxygen-rich polymers increased water solubility of graphene oxide. Doxorubicin was loaded onto the nanocarrier by covalent bonding with hydrazine pendant group and curcumin was loaded through π−π stacking with graphene oxide sheets which were partially reduced to graphene sheets during the carrier preparation. The MTT assay revealed that the carrier had low toxicity because of the presence of oxygen-rich polymers. The drug release of the carrier was investigated and a pH-sensitive behavior was observed for the release of drugs from the carrier. The cellular uptake images proved that co-encapsulation of both DOX and Cur drugs showed higher drug internalization in comparison with the single drug loaded carrier. According to the results, a combination of both drugs exhibited a synergistic behavior for chemotherapy.