Selective Extraction of Valuable and Critical Metals in Cassiterite Concentrate by Dry Chlorination, Part I: Thermodynamic and Modelling Perspective.

The chlorination of oxides of major concern in cassiterite concentrate with various chlorinating agents is investigated in light of their thermodynamic feasibilities to extract and recover their valuable metal components. Mechanisms responsible for the processes and their Gibbs free energy changes as a function of temperature to selectively separate and/or recover the metal(s) of interest and unwanted ones as their metallic chlorides are identified. Attention is given to gaseous (Cl2 and Cl2 + CO mixture) and solid (CaCl2 and MgCl2) chlorine sources, from which Cl2 + CO shows no reaction selectivity for any of the oxides but a feasible metal chloride formation for all. Chlorine gas (Cl2), on the other hand, could selectively form chlorides with metals of +2 oxidation state in their oxides, leaving those of high oxidation state unreacted. MgCl2, unlike CaCl2, is found capable of producing calcium, ferrous, and stannic chloride from their metallic oxides with enhanced reaction tendencies in the presence of silicon dioxide (SiO2). An overall study of the thermodynamic feasibility of all chlorine sources looked at alongside operational and environmental viabilities suitably suggests MgCl2 for a selective extraction of the valuable metal components in a cassiterite concentrate, in which case, moderate temperatures seem promising.

A comprehensive study of pharmaceutics solubility in supercritical solvent through diverse thermodynamic and hybrid Machine learning approaches.

The pharmaceutical industry is increasingly drawn to the research of innovative drug delivery systems through the use of supercritical CO2 (scCO2)-based techniques. Measuring the solubility of drugs in scCO2 at varying conditions is a crucial parameter in this context. In this research, the supercritical solubility of two pharmaceutical ingredients, namely Febuxostat and Chlorpromazine, has been assessed theoretically using various thermodynamic approaches, including PR, SRK, UNIQUAC, and Wilson models. Additionally, hybrid machine learning models of PO-GPR, and PO-KNN were applied to anticipate the supercritical solubility of these medicines. Verification of the accuracy of each model for each pharmaceutical substance is conducted against previously reported experimental solubility data. In the comparison between the SRK and PR models, it is observed that the SRK model displays greater precision in correlating the solubility of both drugs. It consistently achieves a mean Radj value of 0.995 across all cases and mean AARD% values of 14.47 and 9.30 for Febuxostat and Chlorpromazine, respectively. Furthermore, the findings indicate that the UNIQUAC model surpasses the Wilson model in precisely representing the solubility of both medicines. It consistently achieves a mean Radj value higher than 0.985 across both cases and mean AARD% values of 11.39 and 7.08 for Febuxostat and Chlorpromazine, respectively. Additionally, the performance of both hybrid machine learning models proved to be excellent in anticipating the supercritical solubility of both compounds.

Thermodynamic model of MSWI flue gas cooling path: Effect of flue gas composition on heavy metal binding forms.

In the context of circular economy and heavy metal (HM) recovery from municipal solid waste incineration (MSWI) fly ash (FA), detailed knowledge of HM binding forms is required for achieving higher extraction rates. The FA mineralogy is still poorly understood due to its low grain size and low metal concentration. To investigate the HM binding forms, a sophisticated thermodynamic reactive transport model was developed to simulate ash-forming processes. The stability of different binding forms was investigated at different flue gas conditions (varying ratios of HCl, SO2, O2) by simulating the gas cooling path in closed system and dynamic open system, where the gas composition is changing upon cooling due to precipitation of solids. The simulations predict that at flue gas conditions of molar ratio S/Cl < 1, Cu and Zn precipitate as oxides (and Zn silicates) at approximately 650°C. At temperatures <300°C, Zn, Cu, Pb and Cd are predicted to precipitate as easily soluble chlorides. In flue gas with molar ratio S/Cl > 1, the HM precipitate as less soluble sulphates. The results indicate that the less soluble HM fraction in the electrostatic precipitator ash represent oxides and silicates that formed in the boiler section but were transported to the electrostatic precipitator. The model provides insight into the physical-chemical processes controlling the metal accumulation in the flue gas and FA during the cooling of the flue gas. The obtained data serve as valuable basis for improving metal recovery from MSWI FA.

Comments on "Overview and thermodynamic modelling of deep eutectic solvents as co-solvents to enhance drug solubilities in water".

This communication highlights the significance of the final pH of the solution and the potential instability of deep eutectic solvent (DES) within aqueous solutions, and introducing a challenging aspect regarding solute solubilization by DESs.

An experimental and thermodynamic equilibrium investigation of heavy metals transformation in supercritical water gasification of oily sludge.

Supercritical water gasification (SCWG) is an advanced and highly efficient method for treating oily sludge. However, it is crucial to consider the transformation characteristics of heavy metals (HMs) during the SCWG process to prevent potential secondary pollution. This work studied the transformation and distribution characteristics of Cu, Cr and Zn after SCWG of oily sludge in a batch reactor at temperatures ranging from 550 to 700 °C. Additionally, thermodynamic equilibrium analysis was conducted to assess the distribution of HMs based on the minimization of Gibbs free energy. Experimental results indicated that higher temperatures led to the conversion of HMs into more stable forms, effectively immobilizing them within solid products. Furthermore, the addition of Na2CO3 enhanced this process and contributed to a reduction in HMs pollution in the effluent. Thermodynamic equilibrium results were consistent with our experimental data, indicating that the molar fraction of stable HMs forms followed the order: Cr > Cu > Zn. Besides, it is worth noting that Na2CO3 had a limited impact on the distribution of Cu and Cr. However, it played a significant role in inhibiting the formation of silicate Zn at lower temperatures, promoting the decomposition of ZnO*Al2O3 into unstable Zn. This may explain the higher presence of unstable Zn when Na2CO3 was introduced. In summary, this study offers valuable insights into the transformation characteristics of heavy metals and strategies for pollution control during SCWG of oily sludge.

Development and validation of a software application to analyze thermal and kinematic multimodels of Stirling engines.

The work developed presents, for the first time, a tool to analyze all the thermodynamic models used in the study and development of Stirling engines: isothermal, ideal adiabatic and adiabatic with losses, combined adiabatic thermodynamic with finite speed (CAFS), thermodynamic with finite speed (FST), ideal polytropic and polytropic with losses (PSVL), allowing a comparative study of them. This software (ASCE-UMA), designed and implemented in a Matlab GUI® allows to obtain the operating parameters of these engines, calculating the thermodynamic parameters, power output and efficiency. Additionally, the thermodynamic models can be evaluated with different mechanical configurations, for which different drive mechanisms are implemented: Sinusoidal, Alfa Ross yoke types, Alfa Ross V yoke, Beta rhombic type and free piston Stirling engine (FPSE). Thermoacoustic and other, models could be analyzed by virtue of their similarity of movement with some of the implemented models. In the same way, ASCE-UMA allows the study of various exchanger configurations, as well as various regenerator models. The versatility of ASCE-UMA allows the development analysis of all the fundamental elements of a new prototype as well as the analysis of experimental data by performing a customized and detailed calculation. To test the effectiveness of ASCE-UMA, its performance is verified by analyzing Ross Yoke D-90 models and a GM GPU-3 engine. This is a tool that allows to analyze and comparing the different models and the different existing mechanisms for the multiple configurations of Stirling engines in an easy and intuitive application with a high-quality graphical interface.

Sorption of CO2, CH4 and Their Mixtures in Amorphous Poly(2,6-dimethyl-1,4-phenylene)oxide (PPO).

Sorption of pure CO2 and CH4 and CO2/CH4 binary gas mixtures in amorphous glassy Poly(2,6-dimethyl-1,4-phenylene) oxide (PPO) at 35 °C up to 1000 Torr was investigated. Sorption experiments were carried out using an approach that combines barometry with FTIR spectroscopy in the transmission mode to quantify the sorption of pure and mixed gases in polymers. The pressure range was chosen to prevent any variation of the glassy polymer density. The solubility within the polymer of the CO2 present in the gaseous binary mixtures was practically coincident with the solubility of pure gaseous CO2, up to a total pressure of the gaseous mixtures equal to 1000 Torr and for CO2 mole fractions of ~0.5 mol mol-1 and ~0.3 mol mol-1. The Non-Equilibrium Thermodynamics for Glassy Polymers (NET-GP) modelling approach has been applied to the Non-Random Hydrogen Bonding (NRHB) lattice fluid model to fit the solubility data of pure gases. We have assumed here that no specific interactions were occurring between the matrix and the absorbed gas. The same thermodynamic approach has been then used to predict the solubility of CO2/CH4 mixed gases in PPO, resulting in a deviation lower than 9.5% from the experimental results for CO2 solubility.

Speciation of iron(II/III) at the iron-cement interface: a review.

Steel is used as reinforcement in construction materials and it is also an important component of cement-stabilized waste materials to be disposed of in deep geological repositories for radioactive waste. Steel corrosion releases dissolved Fe(II/III) species that can form corrosion products on the steel surface or interact with cementitious materials at the iron-cement interface. The thermodynamically stable Fe species in the given conditions may diffuse further into the adjacent, porous cement matrix and react with individual cement phases. Thus, the retention of Fe(II/III) by the hydrate assemblage of cement paste is an important process affecting the diffusive transport of the aqueous species into the cementitious materials. The diffusion of aqueous Fe(II/III) species from the steel surface into the adjacent cementitious material coupled with the kinetically controlled formation of iron corrosion products, such as by Fe(II) oxidation, decisively determines the extension of the corrosion front. This review summarises the state-of-the art knowledge on the interaction of ferrous and ferric iron with cement phases based on a literature survey and provides new insights and proper perspectives for future study on interaction systems of iron and cement.

Supercritical carbon dioxide solubility measurement and modelling for effective size reduction of nifedipine particles for transdermal application.

Nifedipine (NIF) is a Class II drug of the Biopharmaceutical Classification System (BCS) with low oral bioavailability, low dissolution rate and significant hepatic drug metabolism. The transdermal route using supersaturated systems could be considered. For this purpose, physicochemical properties of NIF such as its dissolution rate, may be a limiting factor and must be improved. Crystallization processes assisted by supercritical carbon dioxide (scCO2) and particularly the Rapid Expansion of Supercritical Solution (RESS) process may improve drug bioavailability by reducing particle size and consequently increasing surface area. This study addresses the reduction of NIF particle size using scCO2-RESS as crystallization process. Experimental solubility studies were performed at different temperature (308 and 318 K) and pressure ranges (9-24 MPa). Solubility data were correlated with two thermodynamic models in order to predict NIF solubility in scCO2. Optimized operating conditions, identified by thermodynamic modelling, allowed the production of thinner NIF particles and a size reduction up to ten fold. Particle size reduction improved NIF dissolution kinetics in aqueous medium: after 90 min, 42 % of raw NIF was released against 80 % for crystallized NIF. The scCO2-RESS process is a solvent free process, that can produce micronized or nanosized crystals able to improve physicochemical properties of poorly water-soluble drugs.

Effects of Limestone Powder on the Early Hydration Behavior of Ye'elimite: Experimental Research and Thermodynamic Modelling.

To investigate the effects of limestone powder and gypsum on the early hydration of ye'elimite, the hydration behavior of C4A3S¯-LP-CaSO4·2H2O-H2O systems are researched. The hydration behavior of systems are researched by employing isothermal calorimetry, XRD technique and chemical shrinkage. The thermodynamic modelling method is employed to predict the equilibrium phase assemblages. The results show that the system with 5 wt.% LP has a comparable hydration heat evolution to limestone powder-free systems. Limestone powder can take part in the reaction to produce monocarboaluminate in the system with M-value (molar ratio of gypsum to ye'elimite) of 1, but monocarboaluminate is not found in the system with M-value of 2. The level off time of chemical shrinkage shortens with the increase of limestone powder dosage. Thermodynamic modelling results show that monocarboaluminate is no longer formed in all systems when M-value exceeds 1.27, which corresponds to the XRD results. This study can provide theoretical guidance for the rational utilization of limestone powder in calcium sulphoaluminate cement.

Design and scale-up of amorphous drug nanoparticles production via a one-step anhydrous continuous process.

Polymeric nanoparticle drug delivery systems are increasingly viewed as crucial building blocks for efficacious treatments of disease conditions. However, production methods at commercially practical scales pose a significant challenge for successfully translating such technology. This paper describes a novel, anhydrous, twin-screw extrusion (TSE) platform-based technology to overcome the issues associated with developing and scale-up production of nanoparticulate drug delivery systems. With polyol as the process medium, the proposed TSE platform enables the encapsulation of the drug and reduction of particle size in a one-step process without the requirement for organic solvents or water. pH-responsive nanoparticle drug delivery of two nonsteroidal anti-inflammatory drugs, naproxen, and celecoxib, was successfully produced using the TSE process. Remarkably, these resulted in nanoparticles with sizes ranging from 80 to 240 nm, up to 98 % drug encapsulation efficiency, and maximum production throughput of 400 g/hour. pH-responsive drug release for both naproxen and celecoxib was also achieved: immediate drug release with enhanced solubility was obtained for naproxen-Eudragit®E nanoparticles (6 times higher) at pH 1.2 and celecoxib-HPMCAS nanoparticles (15 times higher) at pH 6.8, whilst sustained drug release was achieved for naproxen-Eudragit®E nanoparticles at pH 6.8 and celecoxib-HPMCAS nanoparticles at pH 1.2. We expect this platform technology to streamline the development and scale-up production of various polymeric nanoparticle drug delivery systems.

Effects of CO2 Concentration and the Uptake on Carbonation of Cement-Based Materials.

Carbonation seriously deteriorates the durability of existing reinforced concrete structures. In this study, a thermodynamic model is used to investigate the carbonation reactions in cement-based materials. The effects of the concentration and amounts of CO2 on the carbonation behaviors of mortar are discussed. The simulation results show that the mechanisms of the carbonation reaction of cement-based materials at different CO2 concentrations may be different. Nearly all of the hydrate phases have a corresponding CO2 concentration threshold, above which the corresponding carbonation reaction can be triggered. The thresholds of the C-S-H phases with different Ca/Si ratios are different. The calculation results also show that the phase assemblages in cement paste after being completely air-carbonated, primarily consist of a low-Ca/Si ratio C-S-H, strätlingite, CaCO3 and CaSO4. The pH of the pore solution exhibits a significant decrease when a higher Ca/Si ratio C-S-H phase is completely decalcified into a lower Ca/Si ratio C-S-H phase, by increasing the CO2 uptake. Additionally, the experimental results and the previously published investigations are used to validate the simulation results.

Porewater compositions of Portland cement with and without silica fume calculated using the fine-tuned CASH+NK solid solution model.

The CASH+ sublattice solid solution model of C-S-H aims to predict the composition of C-S-H and its ability to take up alkalis. It was originally developed for dilute systems with high water-solid ratios, and thus in this paper further optimized and benchmarked against measured pore solution compositions of hydrated Portland cement (PC) and PC blended with silica fume (SF) at realistic water-binder ratios. To get an improved agreement with the pore solution data, the stability of two CASH+ model endmembers, TCKh and TCNh, has been fine-tuned with standard Gibbs energy corrections of + 7.0 and + 5.0 kJ·mol-1, respectively (at 1 bar, 25 °C). The agreement was maintained with the experiments used to originally parameterize the CASH+ model for the uptake of K and Na in dilute systems. The K and Na concentrations predicted using the fine-tuned CASH+NK model are in a good agreement with the measured values for PC and PC + SF system at different water to binder ratios, silica fume additions, and at temperatures up to 80 °C. Supplementary Information: The online version contains supplementary material available at 10.1617/s11527-022-02045-0.

Adsorption behaviour of simulant radionuclide cations and anions in metakaolin-based geopolymer.

Geopolymers are a class of alkaline-activated materials that have been considered as promising materials for radioactive waste disposal. Currently, metakaolin-based geopolymers (MK-GPs) are attracting interest for the immobilisation of radionuclides in contaminated water from the Fukushima Daiichi Nuclear Power Station. However, the associated chemical interaction mechanisms and the theoretical prediction of the adsorption behaviour of MK-GP in response to cationic radionuclides have not been thoroughly studied or fully understood. In addition, there is a lack of studies on the adsorption capacity of MK-GP for anionic radionuclides. In this study, two types of metakaolin-based (Metastar501 and Sobueclay) geopolymers were synthesised at a K2O:SiO2:H2O ratio of 1:1:13. The binding capacity and interaction mechanism of MK-GP with Cs+, Sr2+, Co2+, I-, IO3-, SeO32-, and SeO42- were evaluated based on the zeta potential, radionuclide binding, and alkali leaching. The results showed that MK-GP does not have the ability to incorporate anionic radionuclides irrespective of the metakaolin source used, but both types of geopolymers have a high capacity to immobilise cationic radionuclides. The uptake of Cs+ was observed as a one-to-one exchange between Cs+ and K+ whereas both one-two and one-one ion exchanges are possible in the case of Sr2+ and Co2+ with K+. The formation of cobalt blue (CoAl2O4) also contributed to the binding of Co2+. Thermodynamic modelling was conducted according to the ion exchange mechanism which predicts the binding of Cs+ and Sr2+ at low concentrations.

Mechanisms and thermodynamic modelling of iodide sorption on AFm phases.

Both, experimental and modelling evidence is presented in this study showing that interlayer anion exchange is the dominant sorption mechanism for iodide (I-) on AFm phases. AFm phases are Ca-Al(Fe) based layered double hydroxides (LDH) known for their large potential for the immobilization of anionic radionuclides, such as dose-relevant iodine-129, emanating from low- and intermediate-level radioactive waste (L/ILW) repositories. Monosulfate, sulfide-AFm, hemicarbonate and monocarbonate are safety-relevant AFm phases, expected to be present in the cementitious near-field of such repositories. Their ability to bind I- was investigated in a series of sorption and co-precipitation experiments. The sorption of I- on different AFm phases was found to depend on the type of the interlayer anion. Sorption Rd values are very similar for monosulfate, sulfide-AFm and hemicarbonate. A slightly higher uptake occurs by AFm phases with a singly charged anion in the interlayer (HS-AFm) as compared to AFm with divalent ions (monosulfate), whereas uptake by hemicarbonate is intermediate. No significant sorption occurs onto monocarbonate. Our derived thermodynamic solid solution models reproduce the experimentally obtained sorption isotherms on HS-AFm, hemicarbonate and monosulfate, indicating that anion exchange in the interlayer is the dominant mechanism and that the contribution of I- electrostatic surface sorption to the overall uptake is negligible.

Thermodynamic and Structural Modelling of Non-Stoichiometric Ln-Doped UO2 Solid Solutions, Ln = {La, Pr, Nd, Gd}.

Available data on the dependence of the equilibrium chemical potential of oxygen on degrees of doping, z, and non-stoichiometry, x, y, in U1-z Ln z O2+0.5(x-y) fluorite solid solutions and data on the dependence of the lattice parameter, a, on the same variables are combined within a unified structural-thermodynamic model. The thermodynamic model fits experimental isotherms of the oxygen potential under the assumptions of a non-ideal mixing of the endmembers, UO2, UO2.5, UO1.5, LnO1.5, and Ln 0.5U0.5O2, and of a significant reduction in the configurational entropy arising from short-range ordering (SRO) within cation-anion distributions. The structural model further investigates the SRO in terms of constraints on admissible values of cation coordination numbers and, building on these constraints, fits the lattice parameter as a function of z, y, and x. Linking together the thermodynamic and structural models allows predicting the lattice parameter as a function of z, T and the oxygen partial pressure. The model elucidates contrasting structural and thermodynamic changes due to the doping with LaO1.5, on the one hand, and with NdO1.5 and GdO1.5, on the other hand. An increased oxidation resistance in the case of Gd and Nd is attributed to strain effects caused by the lattice contraction due to the doping and to an increased thermodynamic cost of a further contraction required by the oxidation.

Modelling of chemical species of Al, Mn, Zn, and Pb in river body waters of industrial areas of West Rhodope Mountain, Bulgaria.

The assessment of the ecological status of natural surface water, in terms of dominant trace metals, within an area subject to various sources of pollution including a non-ferrous metal ore mining, such as the West Rhodope Mountain, Bulgaria, is significant. The present study estimates the ecological status of river body waters at industrial areas of the West Rhodope Mountain, Bulgaria, simultaneously evaluating the possibility of state forecasting, together with assessing the potential risks, through the study of scenarios focusing on (i) possible variations of physicochemical parameters such as pH, concentration levels of trace metals, sulphates, and dissolved organic carbon (DOC) of surface water and (ii) consideration of potential spontaneous precipitation reactions in the studied waters. The ecological status of river body waters was assessed through a combination of experimental field, laboratory, and computational techniques. Al, Mn, Zn, and Pb were found to be the dominant pollutants with a variety of chemical species and distribution. The most significant difference characterizing the chemical species distribution in light of total spontaneous crystallization in the systems was found for Pb, followed by Zn and Mn, with the differences being more significant at lower trace metal levels. The calculated species were discussed on the basis of HSAB (hard and soft acids and bases) principle.

Soluble Salts Quantitative Characterization and Thermodynamic Modeling on Roman Bricks to Assess the Origin of Their Formation.

The environmental weathering and the formation of efflorescences on the brick walls are studied at the "Casa di Diana" Mithraeum at Ostia Antica archaeological site. Previous studies on subsoil, bedrock, hydrological systems and environmental conditions, and new ion chromatography analysis combined with ECOS-RUNSALT and Medusa-Hydra thermodynamic modelling software, had allowed us to identify the subsoil contamination related to soluble salts. The atmospheric acidic gases, CO2 and SO2, are determined as the main salt weathering species. A dry deposition after a subsequent hydration action from the shallow freshwater aquifer that reaches up to 1 m on the walls is identified as the mechanism of salt formation. An evaluation of potential sources such as the nearby Fiumicino airport, CO2-rich gases inputs from fumaroles and CO2 inputs was also debated. The risk level of contamination the surfaces of the materials should be considered mildly/very polluted with a medium/high risk of hygroscopic moisture due to the high concentration of sulphates.

Recycling of blast-furnace sludge by thermochemical treatment with spent iron(II) chloride solution from steel pickling.

One of the typical wastes produced in blast-furnace (BF) ironmaking is BF sludge, which mostly consists of carbon and iron oxides, but also contains toxic trace metals such as Zn, Pb, Cd, As, and Hg that render the material hazardous. Due to the lack of an established recycling process, BF sludges are landfilled, which is ecologically questionable and costly. Here, we investigate selective removal of Zn, Pb, and Cd from BF sludge by chlorination-evaporation reactions using thermodynamic modelling and laboratory-scale experiments. Specifically, BF sludge was thermochemically treated at 650-1000 °C with a spent iron(II) chloride solution from steel pickling and the effects of process temperature and retention time on removal of Zn, Pb, and Cd were investigated. Zinc and Pb were quantitatively removed from BF sludge thermochemically treated at 900-1000 °C, whereas Fe and C as well as other major elements were mostly retained. The Zn, Pb, and Cd contents in the thermochemically treated BF sludge could be lowered from ∼56 g/kg, ∼4 g/kg, and ∼0.02 g/kg to ≤0.7 g/kg, ≤0.02 g/kg, and ≤0.008 g/kg, respectively, thus rendering the processed mineral residue a non-hazardous raw material that may be re-utilized in the blast furnace or on the sinter band.