Solubility Curves Research Articles

Phase Equilibrium of the Quaternary System LiBr-Li2SO4-KBr-K2SO4-H2O at 308.15 K

The phase equilibria of the reciprocal quaternary system LiBr-Li2SO4-KBr-K2SO4-H2O and its ternary sub-systems LiBr-Li2SO4-H2O and KBr-K2SO4-H2O at 308.15 K were studied using the isothermal dissolution equilibrium method. Then, the solubility data of the equilibrium solutions were collected, and the phase diagrams were plotted. The phase diagrams of the ternary sub-systems at 308.15 K were compared with those at other temperatures. This study found that the phase diagram of the LiBr-Li2SO4-H2O system at 308.15 K consisted of an invariant point, two solid-phase crystallization regions of Li2SO4·H2O and LiBr·2H2O, and their corresponding solubility curves. The system generated two hydrated salts, which belonged to the hydrate type I phase diagram. The phase diagram of the KBr-K2SO4-H2O system at 308.15 K consisted of an invariant point, two univariant solubility curves, and two solid-phase crystallization regions of KBr and K2SO4, and no solid solution and double salts were formed. Thus, it belonged to a simple co-saturation type phase diagram. In the LiBr-Li2SO4-KBr-K2SO4-H2O system, K2SO4·Li2SO4 double salt formed at 308.15 K, and the phase diagram consisted of three invariant points, five crystallization regions, and seven univariant solubility curves.

Binary equilibrium behavior for the N,N-dimethylaniline and N,N-diethylaniline in supercritical carbon dioxide

The thermodynamic equilibrium properties of two components, namely, N,N-dimethylaniline (NNDM) and N,N-diethylaniline (NNDE), in supercritical carbon dioxide (S-CO2) were reported. Data determinations were performed through the static-type method from 313.2 to 393.2 K and 4.70 to 24.90 MPa. The results obtained indicated that the solubility of CO2 increased monotonically with the increase in system temperature and mole fraction of NNDM and NNDE in binary (solute + solvent) mixtures. The solubility curve of NNDM and NNDE in the S-CO2 + NNDM and S-CO2 + NNDE system increased with respect to the increasing temperature at a constant pressure. The S-CO2 + NNDM and S-CO2 + NNDE models corresponded to type-I phase behavior. Moreover, laboratory results of both systems were adequately correlated with the Peng-Robinson equation of state. The rmsd (%) of S-CO2 + NNDM [kij = 0.075, ηij = −0.070] and S-CO2 + NNDE [kij = 0.078, ηij = −0.070] models working with two factors established at 353.2 K were noted as 7.50% and 7.08%, respectively.

Experimental and computational investigation of two-component mixtures for the alkyl (ethyl, propyl and butyl) oleate in supercritical carbon dioxide

The main aim of the current study is to understand of solubility curve in solvents at supercritical conditions and including thermodynamics modeling, as well as van der Waals-type models. A thermodynamic approach was commissioned to predict the solubility of a model alkyl oleate monomers in supercritical carbon dioxide (Sc-CO2). Furthermore, the experimental data of phase equilibrium were employed here which are based on measuring the solubility of alkyl oleate monomers in CO2 at supercritical conditions, and the experiments were performed using common synthetic-type method. The thermodynamic equilibrium properties for the two-component mixture of ethyl oleate, propyl oleate and butyl oleate in Sc-CO2 were reported. Bubble (dew)-point data determinations were performed through the synthetic method from various temperatures T= (313.2 to 393.2) K and pressures p = (3.07 to 31.71) MPa. The obtained results indicated that the phase equilibria of Sc-CO2 were found to increase monotonically with the augmented of system temperatures and mole fraction of (ethyl oleate, propyl oleate and butyl oleate) in binary (solute + solvent) mixtures. The solubility curve of ethyl oleate, propyl oleate, and butyl oleate in the ethyl oleate + Sc-CO2, propyl oleate + Sc-CO2, and butyl oleate + Sc-CO2 models rises as the temperature raises at a persistent pressure. The ethyl oleate + Sc-CO2, propyl oleate + Sc-CO2, and butyl oleate + Sc-CO2 models show type-I phase behavior. Moreover, laboratory investigated results of these systems were adequately compared with the P-R EOS. RMSD for the ethyl oleate + Sc-CO2 [κij = 0.060, ηij=-0.030], propyl oleate + Sc-CO2 [κij = 0.062, ηij=-0.030], and butyl oleate + Sc-CO2 [κij = 0.061, ηij=-0.030] models using 2 factors determined at 353.2 K were 4.06 %, 7.43 %, and 5.06 % correspondingly. Also, RMSD of ethyl oleate + Sc-CO2, propyl oleate + Sc-CO2, and butyl oleate + Sc-CO2 systems predicted by adjusted factors at each temperature was 8.46 %, 9.43 %, and 6.29 %, respectively.

Improved Hydrotropic Extraction of Carnosic Acid from Rosemary and Sage with Short-Chain Monoalkyl Glycerol Ethers

Hydrotropic extraction in water with biobased amphiphiles is considered as an interesting alternative to conventional extraction with organic solvents. In this study, butyl, isoamyl, and pentyl glycerol ethers (C4Gly, iC5Gly, and C5Gly, respectively) are investigated for the extraction from rosemary (Rosmarinus officinalis) and sage (Salvia officinalis) of carnosic acid (CA), a powerful natural antioxidant used as an alternative to synthetic ones in food and cosmetic industries. First, interactions between CA and hydrotropes are studied to set the extraction conditions, resulting in the measurement of the solubility curves and miscibility of CA in the hydrotropic solutions. Then, C5Gly is shown to have the highest efficiency to extract CA, which is rationalized with a molecular model previously established for an alkyl polyethylene glycol ether (CiEj) series of amphiphiles based on their log P and molecular volume. Additionally, measurement of the contact angles of the hydrotropic solutions on rosemary leaves indicates that the efficiency of the hydrotrope is also dependent on the interfacial tension.

Lifting the cloak of invisibility: Gold in pyrite from the Olympic Dam Cu-U-Au-Ag deposit, South Australia

Abstract “Invisible gold” refers to gold (Au) occurring either within the lattice of a host sulfide or as discrete nanoparticles (NPs, <100 nm diameter) within a host that are only observable when imaged at very high magnifications. Previous research has regarded the physical form of invisible gold to be partially controlled by the concentration of arsenic (As) in the host sulfide, with stability fields for lattice-bound vs. Au-NPs defined by an empirical Au-As solubility curve. We undertook micrometer- and nanoscale analysis of a representative sample of As-Co-Ni-(Au)-bearing pyrite from Cu-mineralized breccias in the deeper part of the Olympic Dam Cu-U-Au-Ag deposit (South Australia) to define the location and physical form of Au and accompanying elements. Trace element geochemistry and statistical analysis show that >50% of pyrites contain measurable Au and As, and plot below the Au-As solubility curve. Au and As are geochemically associated with Te, Bi, Pb, Ag, and Sn. Primary oscillatory zoning patterns in pyrite defined by As-Co-Ni are reshaped by processes of dissolution-reprecipitation, including new nanoscale growth and rhythmical misorientation structures. Low-angle slip dislocations, twist-wall boundaries and deformation-dipole nanostructures are associated with Te-Bi-Pb-enrichment and host Au-Ag-telluride nanoparticles (NPs). Electrum NPs occur associated with pores coated by Bi-Ag-tellurides or within chalcopyrite particles. Bi-Pb-sulfotellurides, petzite, and sylvanite were identified by atomic-scale scanning transmission electron microscopy. The data support trace element (re)mobilization during pyrite deformation at the brittle to ductile transition (0.5–1 kbar, 300–400 °C) during brecciation. Au-NP formation is decoupled from initial As incorporation in pyrite and instead fingerprints formation of strain-induced, chalcogen-enriched nanoscale structures. Pore-attached NPs suggest scavenging of Au by Bi-bearing melts with higher rates of fluid percolation. Similar scenarios are predictable for pyrite-hosted “invisible Au” in pyrite from other deposits that experienced multiple overprints. Unveiling the cloak of invisibility using contemporary micro- to nano-analytical techniques reveals new layers of complexity with respect to the trace/minor element incorporation in mineral matrices and their subsequent release during overprinting.

Amino acid hydrotropes to increase the solubility of indomethacin and carbamazepine in aqueous solution

A number of amino acids (AA) has been investigated as promising hydrotropes to improve the solubility of biopharmaceutics classification system (BCS) class II drugs carbamazepine (CBZ) and indomethacin (IND) via specific complexations in aqueous solution. The aim of this work is to understand the molecular basis of these hydrotropic interactions by investigating the two model drugs combined with 12 amino acids including phenylalanine, tryptophan, isoleucine, proline, valine, glycine, serine, threonine, arginine, lysine, histidine and aspartic acid in water at 25 °C, 30 °C and 45 °C. The amino acids were chosen based on their different side chains (neutral aromatic, aliphatic, polar charged or uncharged) to investigate their hydrotropic performance. A linear solubility curve was observed between indomethacin and mono-neutral hydrophobic amino acids (phenylalanine, tryptophan, isoleucine, proline and valine) well beyond 1:1 molar ratio indicating the interaction is predominantly non-ionic between the drug and the hydrotropes. Interestingly, the aqueous solubility of carbamazepine (a neutral compound) was enhanced by neutral, charged basic or acidic amino acids, confirming the presence of hydrophobic interactions that involve H-bonds, H/π and π/π stacking and the results were confirmed by UV-Vis spectroscopy. A combination of multiple neutral amino acids showed additive hydrotropic effect in indomethacin solubility with up to 7-folds increases. This study demonstrates for the first time the potential of amino acids as hydrotropes to improve aqueous solubility of poorly water-soluble drugs, which is important for pharmaceutical development.

Investigations on nucleation kinetics and dielectric behavior of potassium DL-malato borate hydrate (C8H10BKO11) single crystal

A single transparent crystal of potassium DL-malato borate was grown with the help of solvent evaporation technique. The lattice parameters, a = 11.3571 Å, b = 5.3225 Å, c = 21.2348 Å and α = β = γ = 90° with space group Pna21 of the grown crystal was confirmed by using the single crystal XRD analysis. The solubility of the compound was measured with the help of gravimetric analysis. The polythermal method was adopted for the determination of the metastable zone width. The solubility curve indicates that the material exhibited a positive temperature gradient of solubility. The induction period of the grown material was measured with the help of the isothermal method. It was found to decrease with increasing the supersaturation ratio and temperature. Various nucleation parameters were calculated with the help of the classical theory of nucleation, which was required for optimizing the growth condition for the growth of the good quality crystal. The low value of the dielectric loss and constant value for high applied frequency ensure the application of this material in device fabrication. The third-order nonlinear properties of the grown crystal were studied with the aid of the Z-scan technique.

Solubility determination and thermodynamic modeling in the quaternary system Li2SO4 – LiBO2 – Li2B4O7 – H2O at T = 308.15 K and p = 0.1 MPa

The solubilities, refractive indices and pH values in the systems LiBO2 – Li2B4O7 – H2O and Li2SO4 – LiBO2 – Li2B4O7 – H2O at 308.15 K were studied by isothermal dissolution equilibrium method. The phase diagram of the ternary system has two single salt crystallization regions of LiBO2·8H2O and Li2B4O7·3H2O, one invariant point and two univariant solubility curves. The dry-salt diagram of the quaternary system is composed of three single salt crystallization regions for Li2SO4·H2O, LiBO2·8H2O and Li2B4O7·3H2O, three univariant solubility curves and one invariant point. The physicochemical properties in the two systems change regularly with the concentration of lithium metaborate of equilibrium solution changing. Combining Pitzer binary parameters obtained in the literatures, the lacking Pitzer mixing parameters in the quaternary system were fitted with the solubilities. The deviation between the calculated solubilities and experimental data in the quaternary system shows that the assumption of only two boron species in the solution is not very accurate, but the calculated results with the assumption can still describe the experimental values.

Evaluation of Physicochemical and Functional Properties of Isolated Pea Protein

Proteins were obtained from pea seeds. Protein solubility, water and oil absorption capacity, emulsifying capacity and emulsion stability, foaming capacity and foam stability were used to determine the pea a chemical and functional properties of protein. The pea protein, obtained by alkaline (NaOH 0.1 N) solubilization (pH 10) and 1:10 (gm/ml) ratio followed by TCA/Acetone precipitation, displayed the highest protein content and the best functional properties. The profiles of the solubility curves corresponding to the participated pea protein (PPP) indicate a minimum solubility at pH ranging from 4-10. The emulsifying capacity of pea participated pea protein was low (3.2) but it has high emulsifying stability (98.9). PPP show a high foaming capacity at pH2 and the suitable time to form the foam is 30 min. the high stability of foam was 78.8%. The result of this study emphasized that PPP has an ability to absorb water more than oil. Thus, the experimental suggesting that PPP can be successfully used as food ingredient due to its nutritional value, chemical composition and functional properties.

Formation of NaCl eutectics in water-in-oil emulsion.

It is shown by thermal analysis and optical microscopy observations that when an NaCl aqueous solution is cooled as a water-in-oil emulsion, a metastable eutectic is formed that has a eutectic point at around -28 °C. The concentration at which the -28 °C eutectic (solid H2O + solid NaCl) melting peak occurs is found by differential scanning calorimetry to be 0.5-2.5 mol kg-1, with no peak found at concentrations above 3.0 mol kg-1. Furthermore, although the heat of eutectic melting increases when the final temperature during cooling is -49 to -51 °C, this decreases at lower temperatures. The conditions for forming this -28 °C eutectic can be understood based on a phase diagram created from existing research data. This suggests that it is possible to predict the formation of the eutectic under non-equilibrium conditions by using (extending) the hydrohalite (NaCl·2H2O) curve (HH curve) and the NaCl solubility curve (HA curve) obtained under equilibrium conditions.

Textures of gold-bearing sulfides and gold precipitation mechanism, Wangu gold deposit, Jiangnan Orogen

万古金矿床位于江南造山带中部，赋存于新元古界冷家溪群浅变质岩系中，受NNE-NE向长沙-平江断裂带和近EW向九岭-清水韧性剪切带联合控制，金资源量约85t。其主要矿石类型为毒砂-黄铁绢英岩型和石英-硫化物脉型，其次为构造角砾岩型。毒砂和黄铁矿为该矿床主要的载金矿物，分布广泛。金成矿作用可分为四个阶段，I为乳白色石英-绢云母-白钨矿阶段；Ⅱ为烟灰色石英-绢云母-毒砂-黄铁矿-金阶段；Ⅲ为烟灰色石英-绢云母-黄铁矿-毒砂-多金属硫化物-金阶段；Ⅳ为乳白色石英-方解石阶段。其中，Ⅱ、Ⅲ为成矿主阶段。根据成矿主阶段毒砂电子探针分析结果，Ⅱ阶段毒砂中As的含量在42.19%~44.84%之间，均值为43.42%（n=56），Ⅲ阶段毒砂中As的含量在40.08%~43.36%之间，均值为42.08%（n=19）。通过毒砂温度计相图估算出Ⅱ、Ⅲ阶段的形成温度和硫逸度分别为364±21℃、319±22℃和10^-9.7~10^-7、10^-11.5~10^-8.6。电子探针数据揭示的载金毒砂和黄铁矿中不可见金含量分别为0.01%~0.66%和0.01%~0.11%。黄铁矿Au-As元素投点分布于金溶解度曲线两侧，说明其内金主要以纳米级颗粒和固溶体金或晶格金的形式赋存；其中Ⅱ阶段黄铁矿纳米级金颗粒占比为73.33%，多于Ⅲ阶段黄铁矿（67.80%）。以上数据说明在水岩反应过程中，围岩中的含铁矿物与成矿流体中的H₂S发生反应，生成毒砂和黄铁矿。伴随着强烈的水岩反应，成矿温度和硫逸度降低，成矿Ⅱ阶段至Ⅲ阶段主要载金硫化物由毒砂转变为黄铁矿，强烈的硫化作用导致金-硫络合物失稳并释放金，金以置换的方式进入硫化物晶格或以显微-超显微金颗粒的形式沉淀，形成含金硫化物；即硫化作用是导致万古矿床不可见金沉淀的主导机制。;The Wangu gold deposit, with a proven gold resource of~85t, is located in the middle section of the Jiangnan Orogen and occurs in metamorphic rock series of the Neoproterozoic Lengjiaxi Group. It formed under the control of the NNE-NE-trending Changsha-Pingjiang fault zone and the EW-trending Jiuling-Qingshui ductile shear zone. The main ore types of the deposit include arsenopyrite-, pyrite-, sericite-, and quartz-altered slate and quartz-sulfide veins, followed by slate breccia within hydrothermal quartz. Arsenopyrite and pyrite are the main gold bearing minerals in the deposit, which are widely distributed in the deposit. Gold mineralization can be divided into four stages:I, the milky quartz-muscovite-scheelite; Ⅱ, the smoky gray quartz-muscovite-arsenopyrite-pyrite-gold; Ⅲ, the smoky gray quartz-muscovite-pyrite-arsenopyrite-polymetallic sulfide-gold; and Ⅳ, the milky quartz-calcite. Among them, the Ⅱ and Ⅲ are the main mineralization stages. Based on the results of Electron Probe Micro Analysis (EPMA) of arsenopyrite from the main mineralization stages, the contents of As in arsenopyrite at stage Ⅱ range from 42.19% to 44.84%, with an average of 43.42% (n=56). The contents of As in arsenopyrite at stage Ⅲ range from 40.08% to 43.36%, with an average of 42.08% (n=19). According to the phase diagram of arsenopyrite thermometer, the formation temperature of Apy-1 in the stage Ⅱ is estimated to be 364±21℃ with a sulfur fugacity varying within 10^-9.7~10^-7. The formation temperature of Apy-2 in the stage Ⅲ is 319±22℃, and its sulfur fugacity is 10^-11.5~10^-8.6. The contents of invisible gold in gold-bearing arsenopyrite and pyrite were 0.01%~0.66% and 0.01%~0.11%, respectively, revealed by EPMA data. The Au-As data of pyrite are plotted on both sides of the gold solubility curve, indicating that gold in pyrite mainly exists in the form of nano-scale particles and solid solution or lattice gold. The proportion of nanometer gold particles in Py-1 pyrite is 73.33%, more than that in Py-2 (67.80%). The above data indicate that in the process of water-rock reaction, the iron-bearing minerals in surrounding rocks react with H₂S in ore-forming fluid to form arsenopyrite and pyrite. Accompanied by a strong water-rock reaction, the main gold-bearing sulfides changed from arsenopyrite to pyrite during mineralization from stage Ⅱ to Ⅲ with the decrease of mineralization temperature and sulfur fugacity, i.e., strong sulfurization results in instability of the gold-sulfur complex and the release of gold. As a result, gold is deposited into the sulfide lattice by substitution or in the form of microscopic-ultra microscopic gold particles to form gold-bearing sulfide. Therefore, sulfidation is the main mechanism of the precipitation of invisible gold in sulfides at the Wangu gold deposit.

Растворимость кислорода в расплавах системы Ni-Co, содержащих цирконий

Thermodynamic analysis of oxygen solutions in zirconium-containing Ni-Co melts has been carried out. The equilibrium constants of interaction of zirconium and oxygen, the activity coefficients at infinite dilution, and the interaction parameters for melts of different composition at 1873 K were determined. The dependences of the oxygen solubility on the contents of cobalt and zirconium in the studied melts were calculated. Zirconium contents in minimum points on the oxygen solubility curves and the corresponding minimum oxygen concentrations were determined.

Revising Concepts on Liquid–Liquid Extraction: Data Treatment and Data Reliability

The intention of this article is to clarify some concepts and relevant aspects of the experimental determination and treatment of liquid–liquid equilibrium data for ternary systems. Distinction is made between solubility curve and binodal curve, setting the stability limit which is defined by the spinodal curve. In addition, it is recommended to carry out the equilibrium data correlation using semiempirical models with a thermodynamic base, over the use of empirical equations. Moreover, the misuse of these empirical equations (Hand, Bachman, Othmer-Tobias, etc.) as proof of data quality or consistency is clarified.

Optical limiting behavior, nonlinear optical studies, geometrical descriptors, chemical properties data, topology analysis on tetraethylammonium L-tartarate dihydrate crystals

The slow cooling technique was utilized to grow organic single crystals of tetraethylammonium L-tartarate dehydrate (EAT) with dimensions 20 × 4 × 4 mm3. The meta stable zone width was obtained via solubility curve. Structural confirmation was achieved using X-ray diffraction. EAT possesses noncentro symmetric P21 space group within the monoclinic crystal structure. Optical transmittance in the visible region reveals a strong transparency with lower cutoff wavelength of 261 nm. EAT crystal’s refractive index is 1.611. The EAT compound's thermal stability was found to be 115 °C, measured by TG-DTA experiments. EAT's specific heat capacity is be 3.670 g −1 K −1. The laser damage threshold of grown EAT crystal surface was measured at 0.3611 GW/cm2. Vicker's microhardness, Kurtz-Perry Powder Method evaluated the mechanical power, particle size based second harmonic generation efficiency (SHG) which identified phase matching in EAT. The SHG maker Fringes technique investigated the SHG of EAT. Optical limiting analysis showed transmitted output power rises linearly till 2.736 mW mm−2 of irradiance.

ZnSe nanoparticles growth by aqueous colloidal solution at room temperature

ZnSe nanoparticles (ZnSe-NPs) were obtained by aqueous colloidal solution at room temperature (25 °C) at different pH. A physicochemical study of the aqueous solution was proposed. The chemical reagents of the colloidal solution were zinc chloride, selenium elementary powder, Extran® as a surfactant, and sodium borohydride as a reducing agent. The species distribution diagrams (SDDs) and solubility curves (SCs) as pH functions were plotted as a result of the physicochemical analysis. The SDDs and SCs predicted the ZnSe-NPs formation and their growing process, therefore, a series of experiments according to these diagrams were performed at various pH of the colloidal solution through different Extran® content. The ZnSe-NPs were obtained without further purification. The ZnSe-NPs were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) techniques. The XRD results revealed that the ZnSe-NPs have mixed cubic and hexagonal crystalline structures, with crystal size at the nanoscale. The Raman spectra exhibited two peaks at 253 cm−1 of the longitudinal optical (LO) phonon mode, and 235 cm−1 of the surface phonon mode corresponding to the ZnSe bulk. The SEM images showed a variety of morphologies with different Zn/Se atomic ratios estimated from the EDS analysis.

Solid-liquid equilibrium of nicotinamide in water-ethanol and water-propylene glycol mixtures

Nicotinamide is an active pharmaceutical ingredient (API) with high structural complexity and one form of vitamin B3 still poorly understood. For the pharmaceutical industry, the solubility knowledge of APIs is truly relevant for their production, bioavailability, and to be careful with polymorphs formation. In this context, it was determined nicotinamide solid–liquid equilibrium in temperatures from 20 to 50 °C for two solvent systems: water–ethanol and water-propylene glycol (PG), by a refractometric method. The experimental results were compared with a correlative thermodynamic model (Apelblat), three activity coefficient models (Wilson, UNIQUAC, NRTL) with (Δcp = 0, Δcp = ΔS, Δcp = f(t)) and with literature data. The Apelblat model showed a good correlation in both solvent systems, the best predictive fit model. For the water–ethanol system was NRTL (Δcp = 0), and for the water-PG was UNIQUAC (Δcp = 0). Maximum solubility values were observed in a 25 % m/m water-PG composition at 50 °C. The results of this work were compared with the literature and indicated to be in good agreement for the water-nicotinamide and ethanol-nicotinamide data. X-ray diffraction measurements of the solids in equilibrium with the liquid indicated that the behavior of solubility curves is not associated with a change in the crystalline structure of solids, probably due to the formation of oligomers in solution.

Design and analysis of CO2 cryogenic separation process for the new LNG purification cold box

l A CO 2 cryogenic separation process at high pressure is proposed and designed for the new LNG purification cold box. l The main parameters are obtained through the mixture phase diagram and solubility curve, and then verified and analyzed by HYSYS simulation. l The temperature curves of the heat exchangers in the process are analyzed. l The exergy losses of the major equipment in the process are calculated and compared with the original process. A CO 2 cryogenic separation process is proposed and designed for the new liquefied natural gas (LNG) purification cold box. This process is based on the liquefaction process using brazed plate heat exchanger (BPHE) and two separators are embedded between the liquefaction and subcooling heat exchangers to remove frozen CO 2 . The separator adopts one-use one-standby mode to ensure uninterrupted operation. The main parameters are first obtained through the phase diagram and solubility curve, and then verified by HYSYS simulation. The simulation results show that the preset values are in good agreement with the simulation. LNG enters the separator at 163 K and then is cooled down to 132.5 K to freeze and separate the CO 2 , so that the CO 2 solids will not block the heat exchanger when they are further subcooled. When the mole fraction of CO 2 inside the separator accumulates to 10%, the process will switch to another separator to work. The mixed refrigerants (MRs) heat the frozen separator to above 189 K, and the mixtures (solid CO 2 and LNG) become liquid and flow out. The change of the process does not cause the temperature crossover inside the heat exchanger. Furthermore, the exergy losses of the proposed process are slightly increased by 1.3% compared to the original process.

Solubility analysis of pharmaceuticals guaifenesin, ketoprofen, and artemisinin in different solvents

Solubility is a fundamental parameter in the discovery of new drug molecules as well as in their production using crystallization processes. In this work, we experimentally investigate the solubility in different solvents and the density of the anti-cough drug guaifenesin and characterize its solid state via Powder X-Ray Diffraction (PXRD) and thermal analysis. Moreover, a strategy is developed and successfully applied to predict the density and solubility behavior of that pharmaceutical. On the solubility curve concentration and temperature depend on each other for a binary solution at fixed pressure. Therefore, densities of undersaturated aqueous solutions of guaifenesin are measured and used alongside with solubility data to obtain more realistic parameters of thermodynamic model. Perturbed Chain-Statistical Associating Fluid Theory (PC-SAFT) Equation of State (EoS) is used. It was able to successfully represent the solubility curves using a small amount of data for fitting the model parameters. In a second part, the applicability of the model to predict the solubility in various organic solvents of two other pharmaceutically relevant molecules, namely the anti-inflammatory drug ketoprofen and the antimalarial compound artemisinin has been studied.The results showed that guaifenesin is the most soluble in ethanol and least soluble in ethyl acetate. Its aqueous solubility shows a special behavior with a specific sharp increase with temperature. In all of the solvents, ketoprofen is the highest soluble among the compounds studied followed by guaifenesin and artemisinin. PC-SAFT is able to capture the experimentally observed effects of temperature, and solvent type on the solubility behavior of each of the three solutes.

Solid–Liquid Phase Equilibria of the Quaternary system Li2SO4–LiBO2–Li2B4O7–H2O and the Ternary Subsystem LiBO2–Li2B4O7–H2O at T = 288.15 K and p = 0.1 MPa

The solubilities, densities, refractive indices, and pH values in the systems LiBO2–Li2B4O7–H2O and Li2SO4–LiBO2–Li2B4O7–H2O at 288.15 K were studied by the classical dissolution method in this paper. The solid–liquid equilibrium phase diagrams and the physicochemical property diagrams were constructed with the experimental results. The phase diagram of the ternary system is composed of two single-salt crystallizations of LiBO2·8H2O and Li2B4O7·3H2O, two solubility univariant curves, and one invariant point saturated with the above salts. The comparison for the phase diagrams in the ternary system at different temperatures shows that the solubilities of lithium metaborate and lithium tetraborate in this system are in a positive correlation with the temperature. The dry-salt diagram of the quaternary system consists of three single-salt crystallization fields for Li2SO4·H2O, LiBO2·8H2O, and Li2B4O7·3H2O, three univariant solubility curves, and one invariant point. The physicochemical properties in the two systems change regularly as the concentration increases in solution. The calculated densities and refractive indices with empirical equations are in good agreement with the experimental results.

Green solvents to tune the biomolecules’ solubilization in aqueous media: An experimental and in silico approach by COSMO-RS

In this work, the solubility of curcumin, gallic acid, and caffeine was measured in aqueous solutions of deep eutectic solvents (DES) and its constituents individually (HBA: cholinium chloride, and HBD: ethylene glycol and 1,2-propanediol) at 298.2 K. The solubility behavior was evaluated by experimental and in silico (by COSMO-RS model) approaches. Additionally, the solubilization kinetics of the curcumin was also evaluated. The finds of this work showed that the use of proper additives can favor the solubility of hydrophobic biomolecules, such as curcumin, in aqueous media. When the gallic acid solubility curves were determined, the hydrotropic effect was observed. This fact allows manipulating the solubilization or precipitation of this biomolecule according to the target application. For the caffeine, in its turn, all additives reduced the solubility of caffeine in relation to pure water. To support the understanding of the experimental data, the biomolecules and additives polarity were calculated by COSMO-RS, through their σ-profile. The in silico approach reinforces the postulate that there is a set of factors involved in solubilization processes, being some of them: the non-polar charges, size, and linearity of the chemical chain, of both solvent and solute. Finally, the dissolution kinetics of curcumin was determined demonstrating the DES' viscosity effect on the mass transfer processes which are the basis of the solubility mechanism. The results here explored reinforces the importance of understanding the role of the polarity, size, and linearity of the chemical chain of all compounds involved in the solubility assay. The comprehension of these facts is of great importance to process development for the food and pharmacist industry, allowing to tune the solubility of the target biomolecule.