The geochemistry of antimony in hydrothermal solutions

<p>In this thesis, 30°C stibnite solubility experiments, ambient temperature X-ray absorption spectroscopic measurements of antimony in solution, and high temperature (70 to 400°C) stibnite solubility experiments were carried out in order to determine the aqueous antimony species present in equilibrium with stibnite in hydrosulfide solutions from pH = 3.5 to 12 and reduced sulfur concentrations from 0.001 to 0.1 mol kg⁻¹. Both ambient and elevated temperature solubility studies were conducted using a flow-through apparatus containing a column of stibnite grains though which solutions were pumped. Above 100°C, solubility experiments were conducted at slightly above saturated water vapour pressure to pressures of 300 bar. At 30°C, the stibnite solubility curve was best reproduced by a scheme of five species: Sb₂S₄²⁻, HSb₂S₄⁻, H₂Sb₂S₅²⁻, H₃SbS₂O, and Sb(OH)₃. At higher temperatures (≥ 70 °C), stibnite solubility at the conditions of the experiments was due to the following four species: Sb₂S₄²⁻, HSb₂S₄⁻, H₃SbS₂O, and Sb(OH)₃. Equilibrium constants were determined for the following five heterogeneous solubility reactions for the temperature ranges listed: [Please consult the thesis for details.] Stibnite solubility was independent of pressure at ≤ 350°C. At ~ 400°C, the solubility of stibnite was strongly dependent on pressure and decreased from Sbtotal = 0.015 to 0.0003 mol kg⁻¹ (~2000 to 40 ppm) with a pressure decrease from 300 to 160 bars. The Sb K-edge X-ray absorption spectroscopic (XAS) measurements of antimony in alkaline (pH = 10. 9 to 12) hydrosulfide solutions gave average first shell coordination environments that were consistent with the speciation model derived from solubility experiments for strongly alkaline solutions (i.e., Sb₂S₄²⁻ and Sb(OH)₃). XAS data enable the elimination of a speciation model involving only monomeric antimony complexes at strongly alkaline pH. Antimony speciation in near neutral to strongly alkaline pH’s is dominated by dimeric antimony-sulfide complexes at 30°C and sulfide concentrations > 0.001 mol kg⁻¹. With increasing temperature, antimony speciation becomes increasingly dominated by Sb(OH)₃. For hydrothermal solutions with sulfide concentrations between 0.0001 and 0.01 mol kg⁻¹, antimony-sulfide complexes are predominant at < 100°C, whereas antimonous acid, Sb(OH)₃, is the main aqueous species at contributing to stibnite solubility at > 200°C with the speciation in the intervening temperature range being dependent on the pH and sulfide concentration of the solution. For higher sulfide concentrations (i.e., ~ 0.1 mol kg⁻¹), HSb₂S₄⁻ and Sb₂S₄²⁻ control stibnite solubility to higher temperatures.</p>

The geochemistry of antimony in hydrothermal solutions

<p>In this thesis, 30°C stibnite solubility experiments, ambient temperature X-ray absorption spectroscopic measurements of antimony in solution, and high temperature (70 to 400°C) stibnite solubility experiments were carried out in order to determine the aqueous antimony species present in equilibrium with stibnite in hydrosulfide solutions from pH = 3.5 to 12 and reduced sulfur concentrations from 0.001 to 0.1 mol kg⁻¹. Both ambient and elevated temperature solubility studies were conducted using a flow-through apparatus containing a column of stibnite grains though which solutions were pumped. Above 100°C, solubility experiments were conducted at slightly above saturated water vapour pressure to pressures of 300 bar. At 30°C, the stibnite solubility curve was best reproduced by a scheme of five species: Sb₂S₄²⁻, HSb₂S₄⁻, H₂Sb₂S₅²⁻, H₃SbS₂O, and Sb(OH)₃. At higher temperatures (≥ 70 °C), stibnite solubility at the conditions of the experiments was due to the following four species: Sb₂S₄²⁻, HSb₂S₄⁻, H₃SbS₂O, and Sb(OH)₃. Equilibrium constants were determined for the following five heterogeneous solubility reactions for the temperature ranges listed: [Please consult the thesis for details.] Stibnite solubility was independent of pressure at ≤ 350°C. At ~ 400°C, the solubility of stibnite was strongly dependent on pressure and decreased from Sbtotal = 0.015 to 0.0003 mol kg⁻¹ (~2000 to 40 ppm) with a pressure decrease from 300 to 160 bars. The Sb K-edge X-ray absorption spectroscopic (XAS) measurements of antimony in alkaline (pH = 10. 9 to 12) hydrosulfide solutions gave average first shell coordination environments that were consistent with the speciation model derived from solubility experiments for strongly alkaline solutions (i.e., Sb₂S₄²⁻ and Sb(OH)₃). XAS data enable the elimination of a speciation model involving only monomeric antimony complexes at strongly alkaline pH. Antimony speciation in near neutral to strongly alkaline pH’s is dominated by dimeric antimony-sulfide complexes at 30°C and sulfide concentrations > 0.001 mol kg⁻¹. With increasing temperature, antimony speciation becomes increasingly dominated by Sb(OH)₃. For hydrothermal solutions with sulfide concentrations between 0.0001 and 0.01 mol kg⁻¹, antimony-sulfide complexes are predominant at < 100°C, whereas antimonous acid, Sb(OH)₃, is the main aqueous species at contributing to stibnite solubility at > 200°C with the speciation in the intervening temperature range being dependent on the pH and sulfide concentration of the solution. For higher sulfide concentrations (i.e., ~ 0.1 mol kg⁻¹), HSb₂S₄⁻ and Sb₂S₄²⁻ control stibnite solubility to higher temperatures.</p>

Improving the Solubilization and Bioavailability of Arbidol Hydrochloride by the Preparation of Binary and Ternary β-Cyclodextrin Complexes with Poloxamer 188

In the current study, the effect of poloxamer 188 on the complexation efficiency and dissolution of arbidol hydrochloride (ADL), a broad-spectrum antiviral agent, with β-cyclodextrin (β-CD) was investigated. Phase solubility studies confirmed a stoichiometry of a 1:1 ratio for both ADL:β-CD and ADL/β-CD with a 1% poloxamer 188 system with an AL type of phase solubility curve. The stability constants (K1:1) calculated from the AL type diagram were 550 M-1 and 2134 M-1 for AD:β-CD and ADL/β-CD with 1% poloxamer 188, respectively. The binary ADL/β-CD and ternary ADL/β-CD with 1% poloxamer 188 complexes were prepared by kneading and a solvent evaporation method and were characterized by aqueous solubility, FTIR, PXRD, DSC and SEM in vitro studies. The solubility (13.1 fold) and release of ADL were markedly improved in kneaded ternary ADL/β-CD with 1% poloxamer 188 (KDB). The binding affinity of ADL and β-CD was confirmed by 1H NMR and 2D ROSEY studies. The ternary complex (KDB) was further subjected for in vivo pharmacokinetic studies in rats and a significant improvement in the bioavailability (2.17 fold) was observed in comparison with pure ADL. Therefore, it can be concluded that the solubilization and bioavailability of ADL can be remarkably increased by ADL/β-CD complexation in the presence of a third component, poloxamer 188.

Test Method for the Solubility Model of Physical Blowing Agent of Self-Expanding Polymer

This paper aims to present a solubility model of physical blowing agent (PBA) for a kind of commonly used self-expanding polymer on engineering. The self-expanding polymer contains Component A (isocyanate) and Component B (polyhydric alcohol, PBA, water, and catalyst). Component B grout of the polymer, which contains PBA, was heated to measure its temperature and volume variations. Based on the principle of mass conservation and Clapeyron equation, the solubility curve of PBA with respect to temperature was calculated. The solubility curve was then applied to simulate the foaming process. A two-component polymer grout foaming experiment was then carried out to verify the applicability of the measured solubility curve. The simulated changes of temperature and density with respect to time of polymer grout were analyzed and compared with experimental results. The error of both sets of curves is within 5%, which shows a good agreement among them and proves the feasibility of the solubility model. This study provides a relatively complete test and verification process for the solubility model of PBA, which lays a theoretical foundation for both the polymer grouting diffusion mechanism and engineering application.

Production, characterization and application of ternary phase diagrams for the purification of biodiesel produced from tropical almond seed oil

This study presents the application of ternary phase diagrams to tropical almond biodiesel components separation and purification at two temperatures. The seed oil was extracted mechanically and alkaline transesterified to produce biodiesel. The oil and biodiesel were characterized using standard methods. Tie lines and binodal solubility curve data were determined using modified cloud point titration procedures. Gas chromatographic method was employed in the analysis of the phase compositions. The mixture of biodiesel, methanol and glycerol were investigated at 20 °C, 30 °C and withdrawal times of 2 to 32 minutes at 2 minutes intervals. Distribution coefficient, K and solvent selectivity, S analysis were performed. Results obtained showed that S > 1 indicating the ability of methanol to promote phase separation and purification. K < 1 implying that there was lower quantities of methanol solubilized in the biodiesel phase. The ternary phase diagrams provided the means of predicting the components distribution. Keywords: Production, Characterization, Tropical Almond Biodiesel, Purification, Ternary Phase Diagram

Room-temperature synthesis, growth mechanisms and opto-electronic properties of organic–inorganic halide perovskite CH3NH3PbX3 (X = I, Br, and Cl) single crystals

Growth of MAPbX3 (X = I, Br, and Cl) single crystals by room temperature crystallization (RTC) method, and the crystallization pathway illustrated by the solubility curve of MAPbCl3 in DMSO, compared with inverse temperature crystallization (ITC) method.

Pembentukan ko-amorf irbesartan-l-arginin dan dampaknya terhadap kelarutan dan laju disolusi irbesartan

Abstrak Latar Belakang: Irbesartan (IBS) adalah antihipertensi yang bekerja menghambat sistem renin-angiotensin dan memiliki kelarutan rendah dalam air, sehingga bioavailabilitasnya terbatas. Tujuan penelitian ini adalah untuk menghasilkan ko-amorf irbesartan dengan l-arginin (ARG) dan untuk mengetahui dampaknya terhadap kelarutan dan laju disolusi irbesartan. Metode: Pembuatan kurva kelarutan fasa dilakukan dengan menentukan kelarutan IBS di dalam rentang konsentrasi 0,1-1,1M dari larutan ARG di dalam air. Ko-amorf dibuat dengan menggiling 1,716 g IBS, 0,696 g ARG, dan lima tetes metanol di dalam Retsch mortar grinder RM 200 selama 15 menit. Untuk mengetahui terbentuknya ko-amorf dilakukan karakterisasi menggunakan difraktometer sinar-X serbuk dan differential scanning calorimeter (DSC). Uji kelarutan dalam media air dilakukan di suhu ruang, sedangkan dalam media larutan dapar pH 1,2 dan 6,8 dilakukan di suhu 37±°C. Larutan dapar pH 1,2 dan 6,8 juga digunakan sebagai media pengujian laju disolusi. Hasil: Kurva kelarutan fasa IBS di dalam larutan ARG menunjukkan tipe AL. Difraktogram menunjukkan terbentuknya ko-amorf IBS-ARG setelah penggilingan. Termogram DSC hasil penggilingan juga menunjukkan telah terbentuk ko-amorf setelah penggilingan basah dengan transisi gelas (Tg) pada 82,2°C. Kelarutan ko-amorf IBS-ARG di dalam air, larutan dapar pH1,2 dan 6,8 berturut-turut 7,2, 2,0, dan 1,9 kali lebih tinggi daripada IBS murni. Laju disolusi ko-amorf IBS-ARG pada kedua media lebih cepat daripada IBS murni. Kesimpulan: Ko-amorf IBS-ARG telah sukses dibuat dengan metode penggilingan basah yang menyebabkan kelarutan dan laju disolusinya lebih baik daripada IBS murni. Abstract Background: Irbesartan (IBS) is an antihypertensive is an antihypertensive which acts to inhibit the renin-angiotensin system and has low water solubility, thus its bioavailability is limited. The aim of this study was to produce co-amorphous irbesartan-l-arginine (IBS-ARG) and to determine its impact on solubility and dissolution rate of irbesartan. Method: Preparation of phase solubility curve was carried out by determining the solubility of IBS in the concentration range 0.1-1.1 M of the ARG solution in water. Co-amorphous was prepared by grinding of 1.716 g IBS, 0.696 g ARG, and five drops of methanol in a Retsch mortar grinder RM 200 for 15 minutes. To determine the formation of co-amorphous, characterization was conduct by a powder X-ray diffractometer and a differential scanning calorimeter (DSC). The solubility test in aqueous medium was carried out at room temperature, while in the buffer solution media pH 1.2 and 6.8 was carried out at 37±0.5°C. The buffer solutions of pH 1.2 and 6.8 were also used as media for dissolution rate testing. Results: The IBS phase solubility curve in the ARG solution showed the AL type. The diffractogram showed the formation of IBS-ARG co-amorphous after wet milling. The DSC thermogram also showed that it was co-amorphous after grinding with a glass transition (Tg) at 82.2°C. The solubility of co-amorphous IBS-ARG in water, pH1.2 and 6.8 of buffer solutions were 7.2, 2.0, and 1.9 folds higher than pure IBS, respectively. The dissolution rate of IBS-ARG co-amorphous in both test media was faster than pure IBS. Conclusion: The IBS-ARG co-amorphous has been successfully prepared by the wet milling method which causes better the solubility and dissolution rate than pure IBS.

Solubility of Na2SO4 in silica-saturated solutions: Implications for REE mineralization

Sulfate is traditionally considered to have retrograde solubility in aqueous solutions. However, our recent hydrothermal diamond-anvil cell (HDAC) experiments have shown that the solubility of Na2SO4 changes from retrograde to prograde in the presence of silica, leading to the formation of sulfate-rich solutions at high temperatures, in line with observations on natural geofluids. In this study, we use synthetic inclusions of fused silica capillary capsules containing saturated Na2SO4 solutions and Na2SO4 crystals to quantitatively investigate the solubility of Na2SO4 at different temperatures in the Na2SO4-SiO2-H2O system. Sulfate concentrations were measured using Raman spectroscopy and calibrated using Cs2SO4 solutions with known concentrations. The solubility of crystalline Na2SO4 dropped slightly when heated from 50 to 225 °C and dramatically from 225 to 313 °C. At 313 °C, the Na2SO4 crystals began to melt, forming immiscible sulfate melt coexisting with the aqueous solution, with or without solid Na2SO4. With the formation of sulfate melt, the solubility of Na2SO4 was reversed to prograde (i.e., solubility increased considerably with increasing temperatures). The solubility of Na2SO4 in the measured solution was significantly higher than that predicted in the absence of SiO2 over the entire temperature range (except for temperatures around 313 °C). This indicates that the presence of SiO2 greatly changes the dissolution behavior of Na2SO4, which may be caused by the formation of a sulfate–silicate intermediates such as Si(OH)4SO42−. Considering that most crustal fluids are silica-saturated, the solubility curve of Na2SO4 obtained in this study can better reflect the characteristics of geofluids when compared to that of Na2SO4-H2O binary system. At temperatures of 313–425 °C, the solubility of Na2SO4 increases with temperature following the function Csulfate = –3173.7/T + 5.9301, where Csulfate and T represent the solubility of Na2SO4 in mol/kg H2O and temperature in Kelvin, respectively. As an application, this temperature-solubility relationship can be used to evaluate the sulfate contents in fluid inclusions that contain sulfate daughter minerals, based on the temperature of sulfate disappearance obtained from microthermometric analysis. The sulfate concentrations of the ore-forming fluids of the giant Maoniuping carbonatite-related rare earth element (REE) deposit (southwest China) were calculated to be 4.67–4.81 m (mol/kg H2O). These sulfate concentrations were then used as internal standards to calibrate the previously reported semi-quantitative results of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis of REE-forming stage fluid inclusions at this deposit. The calculated Ce concentrations in the REE-mineralizing fluid range from 0.42 to 0.49 wt%. The high fluid REE contents suggest that the sulfate-rich fluids are ideal solvents for REE transport. A mass-balance calculation was carried out to evaluate the minimal volume of carbonatite melt that was required for the formation of the giant Maoniuping REE deposit. The result indicates that the carbonatite dikes in the mining area are enough to provide the required fluids and metals, and thus a deep-seated magma chamber is not necessary for ore formation.

Perbaikan Kelarutan Albendazol Melalui Pembentukan Kristal Multikomponen dengan Asam Malat

An effort to improve the solubility of albendazole (ABZ), an anthelmintic drug has been successfully carried out through the formation of multicomponent crystal with dl-malic acid (MAL). Construction of phase solubility curve of ABZ in MAL solution and crystal morphological observations after recrystallization in the acetone-ethanol (9:1) mixture were performed for initial prediction of multicomponent crystal formation. ABZ-MAL multicomponent crystal was prepared by wet grinding or also known as solvent-drop grinding (SDG) with acetone-ethanol (9:1) mixture as a solvent followed by characterization of the multicomponent crystal formation by powder X-ray diffraction and Fourier transform infrared (FTIR) methods. The solubility of ABZ-MAL multicomponent crystal was tested in water at ambient temperature and in pH 1.2, 4.5 and 6.8 of buffered solutions at 37°C. The phase solubility curve of the ABZ in the MAL solution showed type Bs. The ABZ-MAL mixture has a different crystalline morphology than pure ABZ and MAL after recrystallization in the acetone-ethanol mixture (9:1). The powder X-ray diffraction pattern and the FTIR spectrum of ABZ-MAL from SDG different from intact ABZ and MAL powder X-ray diffraction patterns and these results can indicate the ABZ-MAL multicomponent crystal formation. The ABZ-MAL multicomponent crystal has better solubility than pure ABZ in all media used. These results can be concluded that ABZ-MAL multicomponent crystal can be prepared by solvent-drop grinding method with acetone-ethanol (9:1) mixture as a solvent and can increase the solubility of albendazole.

Growth, Nucleation Kinetics and Structural Studies on L-Valine Piperazinium Single Crystals

A single crystal of L-valine piperazinium was grown by slow growth technique. Structural studies confirm the monoclinic structure with space group P21. The solubility curve showing high soluble in water and peak shows positive solubility nature. A tiny nucleation formed at 10 ºC for room temperature process and it gradually increasing with respect process temperature. Induction period revels that time period for nucleation at constant temperature and it absorbed that in (10 ºC) 500 s for room temperature. The calculated interfacial tension values are greater than one order other amino acid based piperazinium. By using growth parameters bulk L-valine piperazinium crystal were harvested and single crystal XRD confirms that formation of L-valine piperazinium crystals.