Solubility Of Sulfide Research Articles

Removal of cadmium and zinc by calcium polysulfide in acidic groundwater: Injection ratio and precipitation mechanism

In this study, we conducted lab-scale experiments to assess the applicability of calcium polysulfide (CPS) for the removal of cadmium (Cd2+) and zinc (Zn2+) from acidic groundwater, with an emphasis on the injection ratio and removal mechanism. For the experiments, CPS was used to treat Cd2⁺ and Zn2⁺ contaminated solution. Solutions were purged with nitrogen gas, and CPS was injected in an anaerobic chamber. After 18 h, solutions were filtered, and heavy metal concentrations were measured using ICP-MS and ICP-OES. Total polysulfide (Sx2⁻) concentration in CPS was determined by converting it to bisulfide (HS⁻) at pH 8.20 and quantifying via UV–Vis spectrophotometry. Precipitates were analyzed using XRD and SEM-EDS after centrifugation. The findings revealed that more than 99.5% of the heavy metals were removed when CPS/Cd2+ (w/w) = 1.45 and CPS/Zn2+ (w/w) = 2.50, determined as the injection ratios for maximum efficiency. These ratios were applicable when Cd2+ and Zn2+ coexisted. From the XRD and SEM-EDS analyses, it was clarified that Cd2+ and Zn2+ precipitated in sulfide forms, consistently showing the preferential precipitation of Cd2+ because of the lower solubility of cadmium sulfide compared to zinc sulfide. In addition, the concentration of Sx2− in the 29% CPS solution was determined to be approximately 2.442 M. Finally, by comparing the injected Sx2− concentration with the concentration of heavy metals removed accordingly, it was concluded that CPS and heavy metals react with a 1:1 M ratio. Based on the above results and precise quantification method, our study suggests that CPS can be effectively utilized to address heavy metal contamination issues and may serve as a valuable tool for the remediation and management of contaminated groundwater globally.

An Investigation into Electrolytes and Cathodes for Room-Temperature Sodium–Sulfur Batteries

In the pursuit of high energy density batteries beyond lithium, room-temperature (RT) sodium–sulfur (Na-S) batteries are studied, combining sulfur, as a high energy density active cathode material and a sodium anode considered to offer high energy density and very good standard potential. Different liquid electrolyte systems, including three different salts and two different solvents, are investigated in RT Na-S battery cells, on the basis of the solubility of sulfur and sulfides, specific capacity, and cyclability of the cells at different C-rates. Two alternative cathode host materials are explored: A bimodal pore size distribution activated carbon host AC MSC30 and a highly conductive carbon host of hollow particles with porous particle walls. An Na-S cell with a cathode coating with 44 wt% sulfur in the AC MSC30 host and the electrolyte 1M NaFSI in DOL/DME exhibited a specific capacity of 435 mAh/gS but poor cyclability. An Na-S cell with a cathode coating with 44 wt% sulfur in the host of hollow porous particles and the electrolyte 1M NaTFSI in TEGDME exhibited a specific capacity of 688 mAh/gS.

Magmatic Controls on Volcanic Sulfur Emissions at the Iceland Hotspot

AbstractOutgassing of sulfur (as SO2) is one of the principal hazards posed by volcanic eruptions. However, S emission potentials of most volcanoes globally are poorly constrained due to a short observational record and an incomplete understanding of the magmatic processes that influence pre‐eruptive S concentrations. Here, we use a compilation of published and new data from melt inclusions (MIs)—which can preserve magmatic S concentrations prior to eruptive degassing—from the Iceland hotspot to evaluate the effects of mantle melting and crustal magmatic processes on the S budgets of Icelandic melts. We use MI data to estimate S emission potentials (ΔSmax, in ppm S) for 73 eruptions from 22 of Iceland's presently active ∼33 volcanic systems. We show that the S systematics of Icelandic melts are strongly regulated by the sulfide solubility limit. Sulfide‐saturated conditions during lower‐degree mantle melting, prevalent at off‐rift zones, likely explains observed decoupling between S and Cl. During magmatic differentiation, a local maximum in modeled sulfide solubility occurs in evolved basalts (4–6 wt.% MgO), coinciding with highest MI S concentrations. Highest ΔSmax values (2,100–2,600 ppm) are found in the Hekla 1913 CE, Eldgjá 939 CE, and Surtsey 1963–1967 CE eruptions in the South Iceland Volcanic Zone. Our results extend the record of volcanic sulfur emissions back in time and can be used to assess volcanic gas hazards at Icelandic volcanoes where no direct measurements are available. Broadly, the results underline the governing role of sulfide saturation during melting and magma differentiation in controlling the eruptible S contents of Icelandic magmas.

Rheologically improved microemulsion for deactivation of simulants of blister and nerve agents

The efficiency of decontamination of blister and nerve agents was studied using the example of nucleophilic decomposition of paraoxone (O,O-diethyl-O-4-nitrophenyl phosphate) and oxidation of methylphenyl sulfide. Hydrogen peroxide solutions in an oil-in-water microemulsion containing synthetic nanoclay Laponite EP and polyvinylpyrrolidone polymer were studied as reactive decontamination systems. The base of the microemulsion consisted of an aqueous phase, a codetergent (isopropanol), oil (hexane), with a variation of detergent (cetylpyridinium chloride, sodium dodecyl sulfate, and Triton X-100). It was shown that the solubility of paraoxone and methylphenyl sulfide in the studied microemulsions increases by an average of 100 times or more compared to the solubility in water, and the substrate binding constants are 2–3 times higher than the binding constants in similar microemulsion media. It was found that the presence of nanoclay in the microemulsion provides a catalytic effect, i.e. an increase in the rate of decomposition of paraoxone and methylphenyl sulfide by at least 2 times. In addition, nanoclay thickens the microemulsion and, together with the polymer, increases the viscosity of the reaction medium. The determined kinetic parameters of decontamination and solubility of substrates allow us to conclude that the use of the investigated microemulsion system provides an acceleration of nucleophilic substitution and oxidation reactions by 150–350 times compared to the reaction rate in water.

Experimental determination and thermodynamic modeling of the hydrogen sulfide hydrate solubility in water

The solubility of hydrogen sulfide (H2S) hydrate, which determines the minimum concentration required for hydrate stability, is critical for the production and transportation of natural gas and the safety of H2S emissions. Herein, Raman spectroscopy was used to measure the solubility of H2S hydrate in water at a temperature of 273.15–301.15 K and pressures ranging from the hydrate–liquid–vapor (H–Lw–V) three-phase equilibrium pressure for each temperature to 100 MPa. The results showed that the solubility of H2S hydrate in water increases with temperature under H–Lw–V three-phase equilibrium conditions. Meanwhile, under hydrate–liquid two-phase equilibrium conditions, the solubility increases significantly with temperature at constant pressure but decreases slightly with pressure at constant temperature. The three-phase solubility can be expressed as mH2Smol∙kg-1=exp-6176.6286/T+20.8318, where the temperature is in K, and the two-phase solubility also depends on the pressure in MPa: mH2Smol∙kg-1=exp-21.1-0.0182P-6281.47-4.23P/T. In addition, a thermodynamic model based on the van der Waals-Platteeuw theory was developed to predict the solubility of H2S hydrate in water and the relative deviations of the solubility of H2S hydrate (AADP) demonstrating the model’s capability to accurately predict the H2S hydrate solubility in water.

Updated COMAGMAT-5: Modeling the Effects of Sulfide Precipitation in Parallel to Crystallization Of Alumino-Chromian Spinel

An updated version of the COMAGMAT-5.3 program is presented, which enables simulations of the silicate-sulfide immiscibility in parallel to crystallization of Al-Cr spinel and other rock-forming minerals. Main changes include a completed recalibration of the previous Fe-Ni sulfide solubility model (Ariskin et al., 2013) and incorporation of equations describing spinel-melt equilibria in a wide range of magmatic systems (Nikolaev et al., 2018а, 2018b). This allowed us to specify more accurately the link between compositions of immiscible sulfides and magma crystallization temperatures, as well as to correct partitioning of alumina between the model spinel and crystallizing melt. The updated COMAGMAT-5.3 can be used for calculations of the crystallization of basaltic to komatiitic magmas, as well as the history of solidification of mafic to ultramafic cumulates, including relative proportions of Al-Cr spinel and immiscible sulfides. Application example includes solidification of sulfide-bearing primitive olivine cumulate from the endocontact of the Yoko-Dovyren intrusion in Northern Transbaikalia (Russia). It is established that maximum crystallization proportions of Al-Cr spinel as much as 3.5 wt % are observed at Ol-Spl cotectic, following an abrupt decrease to slightly negative values during crystallization of plagioclase-bearing assemblages. This results in the inflection point on the trend of evolution of the spinel compositions, which changes from descending the Cr/Al ratio in the field of olivine to its increase when plagioclase starts to crystallize. As compared to previous version COMAGMAT-5.2, the updated model predicts somewhat higher proportions of precipitated sulfides.

Intelligent modeling of hydrogen sulfide solubility in various types of single and multicomponent solvents

This study aims to study the solubility of acid gas, i.e., hydrogen sulfide (H2S) in different solvents. Three intelligent approaches, including Multilayer Perceptron (MLP), Gaussian Process Regression (GPR) and Radial Basis Function (RBF) were used to construct reliable models based on an extensive databank comprising 5148 measured samples from 54 published sources. The analyzed data cover 95 single and multicomponent solvents such as amines, ionic liquids, electrolytes, organics, etc., in broad pressure and temperature ranges. The proposed models require just three simple input variables, i.e., pressure, temperature and the equivalent molecular weight of solvent to determine the solubility. A competitive examination of the novel models implied that the GPR-based one gives the most appropriate estimations with excellent AARE, R2 and RRMSE values of 4.73%, 99.75% and 4.83%, respectively for the tested data. The mentioned intelligent model also performed well in describing the physical behaviors of H2S solubility at various operating conditions. Furthermore, analyzing the William's plot for the GPR-based model affirmed the high reliability of the analyzed databank, as the outlying data points comprise just 2.04% of entire data. In contrast to the literature models, the newly presented approaches proved to be applicable for different types of single and multicomponent H2S absorbers with AAREs less than 7%. Eventually, a sensitivity analysis based on the GPR model reflected the fact that the solvent equivalent molecular weight is the most influential factor in controlling H2S solubility.

Prediction of the Solubility of Acid Gas Hydrogen Sulfide in Green Solvent Ionic Liquids via Quantitative Structure–Property Relationship Models Based on the Molecular Structure

Ionic liquids (ILs) can be used as capturing acidic gases that damage the environment. By establishing a quantitative structure–property relationship (QSPR) model of the IL structure, temperature, pressure, and H2S solubility, it can be used to screen ILs with excellent properties. In this study, molecular descriptors (MD), molecular identifiers (MI), and combinations of MD and MI (MD_MI) are used to represent the structure of ILs, combining pressure and temperature as the input of the model; the QSPR model is built by coupling the two models of the deep neural network (DNN) and random forest (RF). We find that the model constructed by using MI to represent ILs and DNN has the best performance. The Shapley additive explanation (SHAP) method is used to analyze features to obtain the most valuable molecular structure information for prediction. The results show that the contribution degree and direction of different MD and MI in the prediction of H2S solubility are different and correctly identify the impact of environmental factors (temperature and pressure). Finally, the electrostatic potential (ESP) between H2S and ILs was calculated to study the influence of different carbon chain lengths on the solubility of H2S.

Diffusion Coefficient and Absorption of Carbonyl Sulfide in 1-Hexyl-3-methylimidazolium Bis (Trifluoromethyl) Sulfonylimide ([hmim][Tf2N

The solubility of carbonyl sulfide (COS) and also the diffusion coefficients of COS, carbon dioxide, and hydrogen sulfide were experimentally investigated in 1-hexyl-3-methylimidazolium bis(trifluoromethyl) sulfonylimide ([hmim][Tf2N]). The solubility was measured using a static apparatus, and the acid gas diffusivity was obtained by monitoring pressure drop with low initial pressure via the so-called semi-infinite volume method. All experimental absorption trials were carried out in the range of low and medium pressures and temperatures from (313.15 to 353.15) K. Furthermore, all diffusion coefficient experiments were determined at a temperature from (313.15 to 333.15) K and low pressure to some extent to be acceptable in the semi-infinite volume approach. The experimental results were correlated using the Shiflett and Yokozeki versions of the Redlich–Kwong equation of state. In addition, Henry’s law constants and the thermodynamic properties of dissolution at infinite dilution were calculated and discussed.

Density, Viscosity, and Hydrogen Sulfide Solubility of the Triethylamine Hydrochloride Ferric Chloride Ionic Liquid

The density, viscosity, and hydrogen sulfide solubility of the triethylamine hydrochloride ferric chloride ionic liquid (rFeCl3/Et3NHCl) were measured at temperatures of 303.15 to 348.15 K, pressures up to 200 kPa, and iron–amine ratios (r, molar ratio of anhydrous FeCl3 to Et3NHCl) of 0.4 to 1.0 mol·mol–1. Density and viscosity data were respectively fitted with empirical correlations for temperature. The H2S solubility in rFeCl3/Et3NHCl was measured by the isochoric pressure drop method. The absorption of H2S in FeCl3/Et3NHCl contains the physical process and chemical process. The decrease in temperature and iron–amine ratio and the increase in pressure are beneficial to improve the total solubility of H2S. Using the reaction equilibrium thermodynamic model (RETM) to correlate the solubility data, the chemical reaction equilibrium constant and Henry’s constant were obtained. Affected by the molecular molar volume and acidity, Henry’s constant first decreases and then increases with the increase in iron–amine ratio and has a minimum value at 0.6 molar ratio. The reaction equilibrium constant decreases with the rise of iron–amine ratio and the reduction of temperature. The total solubility at low pressure is dominated by chemical absorption. As the pressure increases, the proportion of physical absorption increases.

Solubility and dissolution kinetics of sulfur and sulfides in electrolyte solvents for lithium-sulfur and sodium-sulfur batteries.

In this study, we monitor the dissolution of sulfur and sulfides in electrolyte solvents for lithium-sulfur (Li-S) and sodium-sulfur (Na-S) batteries. The first aim of this research is to assemble a comprehensive set of data on solubilities and dissolution kinetics that may be used in the simulation of battery cycling. The investigation also offers important insights to address key bottlenecks in the development and commercialization of metal-sulfur batteries, including the incomplete dissolution of sulfur in discharge and insoluble low-order sulfides in charge, the probability of shuttling of soluble polysulfides, and the pausing of the redox reactions in precipitated low order sulfides depending on their degree of solid state. The tested materials include sulfur, lithium sulfides Li2Sx, x = 1, 2, 4, 6, and 8, and sodium sulfides Na2Sx, x = 1, 2, 3, 4, 6, and 8, dissolved in two alternative electrolyte solvents: DOL:DME 1:1 v/v and TEGDME. The determined properties of the solute dissolution in the solvent include saturation concentration, mass transfer coefficient, and diffusion coefficient of the solvent in the solid solute. In general, the DOL:DME system offers high solubility in Li-S batteries and TEGDME offers the highest solubility in Na-S batteries. Low solubility sulfides are Li2S2 and Li2S for the Li-S batteries, and Na2S3, Na2S2, and Na2S for the Na-S batteries. However, it is noted that Na2S3 dissolves fast in TEGDME and also TEGDME diffuses fast into Na2S3, offering the possibility of a swollen Na2S3 structure in which Na+ ions might diffuse and continue the redox reactions in a semisolid state.

Thallium removal from wastewater using sulfidized zero-valent manganese: Effects of sulfidation method and liquid nitrogen pretreatment

Zero-valent manganese (ZVMn) possesses high reducibility in theory, while sulfide exhibits strong affinity towards a variety of heavy metals owing to the low solubility of metal sulfides. Yet the performance and mechanisms on using sulfidized zero-valent manganese (SZVMn) to remove thallium (Tl) from wastewater still remain unclear. In this study, the performance of Tl(I) removal using SZVMn synthesized by borohydrides reduction followed by sulfides modification, with and without liquid nitrogen treatment, was compared and the mechanism behind was investigated. The results show that at a S/Mn molar ratio of 1.0, liquid nitrogen modified SZVMn (LSZVMn) possessed more interior channels and pores than SZVMn, with 65.3% higher specific surface area and 73.7% higher porosity, leading to 6.4–8.1% improvement in adsorption of Tl(I) at pH 4–10. LSZVMn showed effectiveness and robustness in Tl(I) removal in the presence of co-existing ions up to 0.1 M. The adsorption of Tl(I) conformed to the pseudo-1st-order kinetic model, and followed the Langmuir isothermal model, with the maximum Tl adsorption capacity of 264.9 mg·g−1 at 288 K. The mechanism of Tl(I) removal with SZVMn was found to include sulfidation-induced precipitation, manganese reduction, surface complexation, and electrostatic attraction. The liquid nitrogen pretreatment embrittled and cracked the outer shell of S/Mn compounds, resulted in a highly hierarchical structure, enhancing the manganese reduction and improving the Tl(I) removal. Based on the above results, the SZVMn and its liquid nitrogen-modified derivatives are novel and effective environmental materials for Tl(I) removal from wastewater, and the application of SZVMn to the removal of other pollutants merits investigation in future study.

Measurement and model of density, viscosity, and hydrogen sulfide solubility in ferric chloride/trioctylmethylammonium chloride ionic liquid

The density and viscosity of ferric chloride/trioctylmethylammonium chloride ionic liquid (rFeCl3/[A336]Cl) with different molar ratios (r = 0.1–0.8) of FeCl3 to [A336]Cl were measured at temperatures from 313.15 to 358.15 K and atmospheric pressure. The density and viscosity data were fitted by the relevant temperature variation equations, respectively. The variation of density and viscosity with temperature and r was obtained. The solubility of rFeCl3/[A336]Cl to H2S was measured at temperatures from 318.15 to 348.15 K and pressures from 0 to 150 kPa. The effects of temperature, pressure, and r on the solubility of H2S were discussed. The reaction equilibrium thermodynamic model (RETM) was used to fit the H2S solubility data, and the average relative error was less than 1.3%, indicating that the model can relate the solubility data well. And Henry's constant and chemical reaction equilibrium constant were obtained by the RETM fitting. The relationships of Henry's constant and chemical reaction equilibrium constant with temperature and r were analyzed.

Copper mobilisation from Cu sulphide minerals by methanobactin: Effect of pH, oxygen and natural organic matter.

Aerobic methane oxidation (MOx) depends critically on the availability of copper (Cu) as a crucial component of the metal centre of particulate methane monooxygenase, one of the main enzymes involved in MOx. Some methanotrophs have developed Cu acquisition strategies, in which they exude Cu‐binding ligands termed chalkophores under conditions of low Cu availability. A well‐characterised chalkophore is methanobactin (mb), exuded by the microaerophilic methanotroph Methylosinus trichosporium OB3b. Aerobic methanotrophs generally reside close to environmental oxic–anoxic interfaces, where the formation of Cu sulphide phases can aggravate the limitation of bioavailable Cu due to their low solubility. The reactivity of chalkophores towards such Cu sulphide mineral phases has not yet been investigated. In this study, a combination of dissolution experiments and equilibrium modelling was used to examine the dissolution and solubility of bulk and nanoparticulate Cu sulphide minerals in the presence of mb as influenced by pH, oxygen and natural organic matter. In general, we show that mb is effective at increasing the dissolved Cu concentrations in the presence of a variety of Cu sulphide phases that may potentially limit Cu bioavailability. More Cu was mobilised per mole of mb from Cu sulphide nanoparticles compared with well‐crystalline bulk covellite (CuS). In general, the efficacy of mb at mobilising Cu from Cu sulphides is pH‐dependent. At lower pH, e.g. pH 5, mb was ineffective at solubilizing Cu. The presence of mb increased dissolved Cu concentrations between pH 7 and 8.5, where the solubility of all Cu sulphides is generally low, both in the presence and absence of oxygen. These results suggest that chalkophore‐promoted Cu mobilisation from sulphide phases is an effective extracellular mechanism for increasing dissolved Cu concentrations at oxic–anoxic interfaces, particularly in the neutral to slightly alkaline pH range. This suggests that aerobic methanotrophs may be able to fulfil their Cu requirements via the exudation of mb in natural environments where the bioavailability of Cu is constrained by very stable Cu sulphide phases.

Preparation and characterization of the dimethyl sulfide-β-cyclodextrin inclusion complex.

Dimethyl sulfide has been widely used in flavors and can also be used as a solvent and catalyst. However, dimethyl sulfide is volatile, and its lasting power is weak. Furthermore, dimethyl sulfide is insoluble in water and is unstable in some cases. This study concentrated on the encapsulation of dimethyl sulfide in β-cyclodextrin to form an inclusion complex and to improve the durability, water solubility, and stability of dimethyl sulfide. The product was successfully produced and characterized by scanning electron microscopy, diffraction of X-rays, and thermal analysis. The dimethyl sulfide loading capacity is 6.40±0.08%. Based on the thermal release characteristics of dimethyl sulfide, the kinetic and thermodynamic parameters were obtained. The apparent activation energy, pre-exponential factor, and reaction order of the dimethyl sulfide release reaction were obtained and the values were 95.0±0.1kJ/mol,1.03×1015 s-1 , and 1, respectively. The activation entropy change, activation enthalpy change, and activation Gibbs free energy change were 41.6 J/K, 95.0kJ/mol, and 81.3kJ/mol, respectively, during the process of dimethyl sulfide release at 56.7℃. To make it clear that the dimethyl sulfide molecule interacts with β-cyclodextrin molecule, molecular simulation was used to investigate the formation process of the dimethyl sulfide-β-cyclodextrin inclusion complex. The binding energy and the optimized structure were obtained. When the Z coordinate of the S atom in the dimethyl sulfide molecule is 1.1×10-10 m, the binding energy attained the minimum value, -51.3kJ/mol. These basic data are helpful for understanding the dimethyl sulfide-β-cyclodextrin inclusion complex formation mechanism and the interaction between dimethyl sulfide and β-cyclodextrin. PRACTICAL APPLICATION: By forming an inclusion complex with β-cyclodextrin, the stability, durability, and water solubility of dimethyl sulfide can be improved. Dimethyl sulfide-β-cyclodextrin inclusion complex can be widely used in the food, beverage, flavor, and fragrance industries. The kinetic and thermodynamic parameters, binding energy, and the results of molecular simulation are helpful to understand the dimethyl sulfide-β-cyclodextrin inclusion complex formation mechanism and the interaction between dimethyl sulfide and β-cyclodextrin.

Experimental modeling of antimony sulfides-rich geothermal deposits and their solubility in the presence of polymeric antiscalants

Antimony (Sb)-rich geothermal deposits have been observed in many geothermal power plants worldwide. They occur as red-colored, sulfidic precipitates disturbing energy-harvesting by clogging the geothermal installations. In order to prevent the formation of this scale, information on its physicochemical features is needed. For this purpose, Sb-rich sulfide-based deposits were synthesized at controlled conditions in a pressurized glass reactor at geothermal conditions (135 °C and 3.5 bar). Various polymeric antiscalants with different functional groups, such as acrylic acid, sulphonic acid, and phosphonic acid groups were tested for their effect on Sb sulfide solubility. An additional computational study was performed to determine the binding energy of Sb and S atoms to these groups. The results suggest that sulfonic acid groups are the most affective. Therefore, it was concluded that these macromolecule containing sulfonic acid groups and poly (vinyl sulfonic acid) derivatives could potentially act as antiscalants for the formation of antimony sulfide.

Investigation of H2S Solubility in Aqueous N- Methyldiethanolamine + Amine Functionalized UiO-66 as a nano solvent

In this paper, the experimental solubility of hydrogen sulfide in aqueous N- Methyldiethanolamine + Amine Functionalized UiO-66 (UiO-66-NH2) was studied. UiO-66-NH2 was produced using solvothermal process, and its physicochemical properties were investigated by different techniques including XRD, TGA, TEM, BET, and FTIR to realize its crystalline structure, morphology, thermal stability, and porous structure. The Zeta potential of the solution was turned out to be about 26.6 mV (millivolt), meaning that UiO-66-NH2 particles are moderately stable in aqueous 40 wt.% MDEA. The solubility of hydrogen sulfide has been carried out using the isochoric saturation / or static method in two concentration grades of 0.1 and 0.5 wt.% of UiO-66-NH2 in the aqueous solution of 40 wt.% MDEA known as nanofluid. Experimental measurements were carried out at temperatures of 303.15 through 333.15 K, and pressures up 1100 kPa. Results showed that the addition of UiO-66-NH2 nanoparticles to the MDEA solution altered the results less than 3% , while the mean value of uncertainty reported in this work is about 4% , meaning that the addition of nanoparticles do not have remarkable effect on H2S solubility. In contrast, it causes an increased capacity of CO2 absorption of that solution up to 10%.

The solubility calculation of methane and acidic gases in associating solvents by a predictive approach using Henry’s law together with SRK and CPA equation of states

In this study, the binary interaction parameters (BIPs) between a solute and solvent were calculated by combining Henry’s law and an equation of state (EoS) while the obtained BIPs were then applied to predict the solubility of carbon dioxide, hydrogen sulfide, and methane in various associating solvents. Water-CO2, water-H2S, water-CH4, methanol-CO2, methanol-H2S, methanol-CH4, ethanol-CO2, 1,2-propanediol-CO2, and glycerol-CO2 mixtures, were studied by Soave-Redlich-Kwong (SRK) and cubic-plus-association (CPA) EoSs over a wide range of temperature and pressure (a total of 384 data points). Both EoSs were capable of predicting the solubility of gases in studied associating solvents by obtained BIPs at investigated temperatures and pressures; however, CPA EoS has produced relatively more satisfactory results with a general absolute average relative deviation (AARD) of 5.38% compared to SRK EoS with that of 6.21%. This can be atributed to the high potential of CPA EoS in describing associating compounds (water and alcohols). Moreover, there was a linear relationship between obtained BIPs and temperature for some mixtures, while for others a quadratic one was the best.

A modeling approach for estimating hydrogen sulfide solubility in fifteen different imidazole-based ionic liquids

Absorption has always been an attractive process for removing hydrogen sulfide (H2S). Posing unique properties and promising removal capacity, ionic liquids (ILs) are potential media for H2S capture. Engineering design of such absorption process needs accurate measurements or reliable estimation of the H2S solubility in ILs. Since experimental measurements are time-consuming and expensive, this study utilizes machine learning methods to monitor H2S solubility in fifteen various ILs accurately. Six robust machine learning methods, including adaptive neuro-fuzzy inference system, least-squares support vector machine (LS-SVM), radial basis function, cascade, multilayer perceptron, and generalized regression neural networks, are implemented/compared. A vast experimental databank comprising 792 datasets was utilized. Temperature, pressure, acentric factor, critical pressure, and critical temperature of investigated ILs are the affecting parameters of our models. Sensitivity and statistical error analysis were utilized to assess the performance and accuracy of the proposed models. The calculated solubility data and the derived models were validated using seven statistical criteria. The obtained results showed that the LS-SVM accurately predicts H2S solubility in ILs and possesses R2, RMSE, MSE, RRSE, RAE, MAE, and AARD of 0.99798, 0.01079, 0.00012, 6.35%, 4.35%, 0.0060, and 4.03, respectively. It was found that the H2S solubility adversely relates to the temperature and directly depends on the pressure. Furthermore, the combination of OMIM+ and Tf2N-, i.e., [OMIM][Tf2N] ionic liquid, is the best choice for H2S capture among the investigated absorbents. The H2S solubility in this ionic liquid can reach more than 0.8 in terms of mole fraction.

Synergistic dual conversion reactions assisting Pb-S electrochemistry for energy storage

SignificanceBased on the analysis of three thermodynamic parameters of various M-S systems (solubility of metal sulfides [MxSy] in aqueous solution, volume change of the metal-sulfur [M-S] battery system, and the potential of S/MxSy cathode redox couple), an aqueous Pb-S battery operated by synergistic dual conversion reactions (cathode: S⇄PbS, anode: Pb2+⇄PbO2) has been officially reported. Benefitting from the inherent insolubility of PbS and a conversion-type counter electrode, the aqueous Pb-S battery exhibited two advantages: it is shuttle effect free and has a dendrite-free nature. Moreover, the practical value of the Pb-S battery was further certified by the prototype S|Pb(NO3)2ǁZn(NO3)2|Zn hybrid cell, which afforded an energy density of 930.9 Wh kg-1sulfur.