Ion pair formation in copper sulfate aqueous solutions at high temperatures

Ion Association in Dilute Aqueous Magnesium Sulfate and Nickel Sulfate Solutions Under Hydrothermal Conditions by Flow Conductivity Measurements

“…Dielectric relaxation studies from (278 to 340) K , and ab initio MD calculations also provide evidence for the presence of 1:2 or 2:1 ion pairs at concentrations above about 0.1 mol·kg −1 and confirm that their stability increases with temperature. According to both the DRS studies and the Archer−Wood model, the triplet species should not be a significant factor at the concentrations ( m < 0.01 mol·kg −1 ) employed in our present study. The lower values of log K 11 reported by Archer and Rard (Table ), relative to our experimental values of log K A in Table , suggest that all or part of the contributions of the solvent−solvent separated ion pairs and solvent-separated ion pairs are described by the Debye−Hückel and ion-interaction terms of the Pitzer model, so that their fitted values for log K 11 are more closely associated with the contact ion-pair formation constant, log K CIP .…”

“…The effect of temperature and pressure on the association of 2:2 electrolytes has been a topic of active investigation since the pioneering studies of Noyes and his co-workers at the Carnegie Institute more than 100 years ago. , A wide variety of studies using conductance, − potentiometry, solubility, − calorimetry, densimetry, and osmotic pressure methods , have been used to derive thermochemical models for these systems. These have been complemented by techniques such as ultrasonic absorption, Raman spectroscopy, − UV−visible spectroscopy, and dielectric relaxation spectroscopy (DRS), , which have been proven to be powerful tools for distinguishing between different types of ion pairs, the so-called “solvent−solvent-separated”, “solvent-separated”, and “contact” ion pairs. Most of these methods are limited to temperatures near ambient conditions, either because of experimental constraints or because many of the metal sulfate salts display inverse solubility relationships at elevated temperatures which limits the use of instruments that require solution concentrations greater than ∼0.05 mol·kg −1 . ,,,− …”

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

“…A steep increase in the values of log β 1 with temperature is expected, since preferential formation of the neutral species UO 2 SO 4 0 (aq) is favored at high temperatures due to the increasing importance of long-range solvent polarization effects associated with the decrease in the dielectric constant and increase in isothermal compressibility as water approaches its critical point. While other 2:2 electrolytes show similar behavior (Cu 2+ , Zn 2+ , Mg 2+ , and Ni 2+ ) − the increase in the formation constant of uranyl sulfate is much larger. For example, the increase in association constant from 25 to 250 °C for the transition metal complexes NiSO 4 0 (aq) and CuSO 4 0 as well as the alkaline earth metal complex MgSO 4 0 (aq) is ∼2.2 log 10 units, while the formation constant of UO 2 SO 4 0 (aq) shown in Figure and Table increases by ∼3.4 log 10 units.…”

PtII‐Catalyzed Hydroxylation of Terminal Aliphatic C(sp3)−H Bonds with Molecular Oxygen

“…First, one must note that CuCl 2 is expected to partially dissociate to free Cu II ,a samoderately low equilibrium constant has been reportedf or the interaction of Cu II with one or more Cl À ions. [48] Conversely,C u II has ah igh tendency to associate with SO 4 2À , [49] which indicates that CuCl 2 is partially transformed into CuSO 4 when H 2 SO 4 is present. Moreover,s tabilityt ests with varying H 2 SO 4 concentrations revealed an otable change in the side product distribution;a ne levated concentrationo ft he degradation product acetic acid was observed in H 2 SO 4 -free conditions.…”