A Raman spectroscopic and investigation of aqueous boron speciation under alkaline hydrothermal conditions: evidence for the structure and thermodynamic stability of the diborate ion.

Raman spectra of aqueous sodium borate solutions, with and without excess NaOH, NaCl, and LiCl, have been obtained from perpendicular and parallel polarization measurements acquired using a custom-built sapphire flow cell over the temperature range 25 to 300 °C at 20 MPa. The solvent-corrected reduced isotropic spectra include a large well-defined band at 865 cm which overlaps with the boric acid B(OH) band at 879 cm, and becomes increasingly intense at elevated temperatures. This band does not correspond to the spectrum of any other previously reported aqueous polyborate ions, all of which have symmetric stretching bands at frequencies below that of borate, [B(OH)], at 745 cm.

Second ionization constant of sulfuric acid in HO and DO from 150 to 300 °C at = 11.5 MPa using flow AC conductivity.

A custom-built flow-through AC conductivity instrument was used to measure the deuterium isotope effect on the ionization quotient of bisulfate from 150 to 300 °C, at = 11.5 MPa. Standardized solutions of KCl, HCl, KOH, KHSO, KSO, and HSO were prepared in light and heavy waters and their conductivities were measured and fitted with the Quint-Viallard conductivity model to obtain single ion conductivities at infinite dilution for K, Cl, H, OH, HSO, and SO.

Limiting Conductivities of Strong Acids and Bases in DO and HO: Deuterium Isotope Effects on Proton Hopping over a Wide Temperature Range.

The molar conductivity (Λ°) of hydrochloric acid, potassium hydroxide, and sodium hydroxide has been measured in both light and heavy waters from 298 to 598 K at = 20 MPa using a high-precision flow-through alternating current (AC) conductance instrument. The results were used to explore the deuterium isotope effect on ionic transport by proton hopping mechanisms under hydrothermal conditions. Extrapolations of published transport number data to elevated temperature were used to calculate the individual ionic contributions (λ°) for HO, DO, OH, and OD, from which the excess molar conductivities due to proton hopping were calculated.

Third dissociation constant of phosphoric acid in HO and DO from 75 to 300 °C at = 20.4 MPa using Raman spectroscopy and a titanium-sapphire flow cell.

A custom-built titanium-sapphire flow cell has been used with a confocal Raman microscope to collect solvent-corrected reduced isotropic spectra of sodium and potassium phosphate solutions in light and heavy water from 75 to 300 °C at 20.4 ± 0.4 MPa over a wide range of concentrations.

Second Dissociation Constant of Carbonic Acid in HO and DO from 150 to 325 °C at = 21 MPa Using Raman Spectroscopy and a Sapphire-Windowed Flow Cell.

Solvent-corrected reduced isotropic spectra of carbonate and bicarbonate in light and heavy water have been measured from 150 to 325 °C at 21 MPa using a confocal Raman microscope and a custom-built titanium flow cell with sapphire windows. The positions of the symmetric vibrational modes of CO and HCO/DCO were compared to density functional theory (DFT) calculations with a polarizable continuum model in light and heavy water. The experimental Raman peak positions shifted linearly toward lower wavenumbers with increasing temperatures.

Investigation of Uranyl Sulfate Complexation under Hydrothermal Conditions by Quantitative Raman Spectroscopy and Density Functional Theory.

Quantitative first and second formation constants of aqueous uranyl sulfate complexes were obtained from Raman spectra of solutions in fused silica capillary cells at 25 MPa, at temperatures ranging from 25 to 375 °C. Temperature-dependent values of the symmetric O-U-O vibrational frequencies of UO(aq), UOSO(aq), and UO(SO)(aq) were determined from the high-temperature spectra. Temperature-independent Raman scattering coefficients of UO(aq) were calculated directly from uranyl triflate spectra from 25 to 300 °C, while those of UOSO(aq) and UO(SO)(aq) were derived from spectroscopic data at 25 °C and concentrations calculated using the formation constants of Tian and Rao ( 2009 , 41 , 569 - 574 ), together with the Specific Ion Interaction Theory (SIT) activity coefficient model.

Triborate Formation Constants and Polyborate Speciation under Hydrothermal Conditions by Raman Spectroscopy using a Titanium/Sapphire Flow Cell.

Solvent-corrected reduced isotropic Raman spectra of aqueous boric acid + sodium borate solutions have been obtained from perpendicular and parallel polarization measurements in a novel custom-made titanium flow cell with sapphire windows over the temperature range 25 to 300 °C at 20 MPa using the perchlorate anion, ClO, as an internal standard. The reduced isotropic spectra of solutions yielded the first reported quantitative speciation results for polyborate ions in equilibrium with boric acid and borate in high-temperature aqueous solutions above 200 °C. The spectra obtained from solutions at low sodium/boron ratios, 0 < m/ m < 0.

Non-Complexing Anions for Quantitative Speciation Studies Using Raman Spectroscopy in Fused Silica High-Pressure Optical Cells Under Hydrothermal Conditions.

This paper reports methods for obtaining time-dependent reduced isotropic Raman spectra of aqueous species in quartz capillary high-pressure optical cells under hydrothermal conditions, as a means of determining quantitative speciation in hydrothermal fluids. The methods have been used to determine relative Raman scattering coefficients and to examine the thermal decomposition kinetics of the non-complexing anions bisulfate (HSO4(-)), perchlorate (CIO4(-)), perrhenate (ReO4(-)), and trifluoromethanesulfonate, or "triflate" (CF3SO3(-)) in acidic and neutral solutions at temperatures up to 400°C and 30 MPa. Arrhenius expressions for calculating the thermal decomposition rate constants are also reported.

Raman and ab initio investigation of aqueous Cu(I) chloride complexes from 25 to 80 °C.

Temperature-dependent Raman studies of aqueous copper(I) chloride complexes have been carried out up to 80 °C, along with supporting ab initio calculations for the species [CuCl(n)(H2O)m](1-n), n = 0-4 and hydration numbers m = 0-6. Normalized reduced isotropic Raman spectra were obtained from perpendicular and parallel polarization measurements, with perchlorate anion, ClO4(-), as an internal standard. Although the Raman spectra were not intense, spectra could be corrected by solvent baseline subtraction, to yield quantitative reduced molar scattering coefficients for the symmetric vibrational bands at 297 ± 3 and 247 ± 3 cm(-1).

Standard partial molar volumes of some aqueous alkanolamines and alkoxyamines at temperatures up to 325 degrees C: functional group additivity in polar organic solutes under hydrothermal conditions.

Apparent molar volumes of dilute aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), N,N-dimethylethanolamine (DMEA), ethylethanolamine (EAE), 2-diethylethanolamine (2-DEEA), and 3-methoxypropylamine (3-MPA) and their salts were measured at temperatures from 150 to 325 degrees C and pressures as high as 15 MPa. The results were corrected for the ionization and used to obtain the standard partial molar volumes, Vo2. A three-parameter equation of state was used to describe the temperature and pressure dependence of the standard partial molar volumes.

Apparent and standard partial molar volumes of NaCl, NaOH, and HCl in water and heavy water at T = 523 K and 573 K at p = 14 MPa.

Apparent molar volumes, Vphi,2, of aqueous NaCl, NaOH, NaOD, HCl, and DCl in water and heavy water were determined at T = 523 and 573 K and p = 14 MPa with a high-temperature platinum vibrating-tube densimeter in the aquamolality range 0.25 View Article and Find Full Text PDF

Standard partial molar volumes of aqueous glycolic acid and tartaric acid from 25 to 350 degrees C: evidence of a negative Krichevskii parameter for a neutral organic solute.

Apparent molar volumes have been determined using a high-pressure vibrating-tube densimeter for aqueous solutions of glycolic acid (HGly = HOCH(2)COOH) and tartaric acid (H(2)Tar = HOOCCH(OH)CH(OH)COOH) at temperatures from 25 degrees C to 350 degrees C and pressures as high as 20 MPa. The resulting standard partial molar volumes (HGly,aq) are relatively independent of temperature until 315 degrees C, at which point (HGly,aq) deviates sharply toward negative values. This suggests that the Krichevskii parameter, A(Kr) = lim(x(2) --> 0) , which describes the discontinuities in standard partial molar properties at the critical point of water, is negative.