Solubility Of CuO Research Articles

Revealing the mechanism of solid-state electrochemical conversion reactions in strong alkaline solutions

Solid-state conversion reactions are ubiquitous in various electrochemical systems such as metal-ion batteries, lead-acid batteries, electrochemical reduction of solid oxides, etc. However, a deep understanding of the reaction mechanism in the solid electrode remains challenging. In this paper, we systematically study the deoxidation of porous CuO in strong alkaline solution using three types of electrode configurations. The reduction rate of CuO depends on the cell voltage, temperature, reduction depth, and solubility of CuO, and the reduction follows a geometrical contraction model. The diffusion coefficients (cm2 s−1) of O2− increase from 7.38 × 10−11 at 80 °C to 1.19 × 10−9 at 120 °C. In addition, the diffusion coefficients of O2− during the reduction of solid Bi2O3 and Sb2O3 are 3.00 × 10−10 and 1.22 × 10−9, respectively. Besides, a dissolution-deposition mechanism is proven to play a key role in controlling the reduction rate and morphologies of the electroactive species. Overall, this paper sheds light on deeply understanding various solid-state electrochemical reactions in terms of ion diffusion and the interplay of electrode materials and electrolytes.

Dissolution behavior of metal oxide nanomaterials in cell culture medium versus distilled water

Solubility is a key criterion used in the hazard assessment of metal oxide–engineered nanomaterials (ENMs). The present study investigated solubility of CuO, NiO, and TiO2 ENMs compared with their bulk analogues in two aqueous media: water and Dulbecco’s modified Eagle’s medium (DMEM). Particle size distributions were characterized using dynamic light scattering (DLS) and tunable resistive pulse sensing (TRPS). After centrifugal separation, the dissolved metal fraction was quantified using inductively coupled plasma optical emission spectroscopy (ICP-OES). Overall, solubility of the metal oxides decreased in the order CuO ≥ NiO > TiO2 in both media, with each ENM displaying higher solubility than its bulk analogue. However, the metal oxide ENMs responded differently to the two aqueous media, when comparing their solubility using a low initial concentration (10 mg/L) versus a high initial concentration (100 mg/L). In DMEM, both nano-CuO and nano-NiO displayed increased solubility at the higher initial concentration by 3.8-fold and 1.4-fold, respectively. In water, this trend was reversed, with both nano-CuO and nano-NiO displaying increased solubility at the lower initial concentration by 3.3-fold and 1.2-fold, respectively. Interestingly, solubility trends displayed by nano-TiO2 were the opposite of those displayed by nano-CuO and nano-NiO. In DMEM, nano-TiO2 displayed decreased solubility at the higher initial concentration (0.3-fold), whereas in water, nano-TiO2 displayed increased solubility at the higher initial concentration (5.5-fold). These results show the importance of evaluating the solubility of ENMs in biologically relevant fluids at concentrations that correspond to toxicity assays, for the purposes of read-across and grouping ENMs.

The solubility of crystalline cupric oxide in aqueous solution from 25 °C to 400 °C

Measurements of the solubility of crystalline cupric oxide were made in liquid water and steam at controlled pH conditions from 25.0°C to 400°C using flow-through packed columns and batch sampling techniques. Only partial agreement with literature values was evident for CuO(cr) solubility in liquid water leading to large differences in the first two hydrolysis constants of Cu2+ compared to those from numerous potentiometric studies. The concentrations of NaOH employed in this study were too low to form measureable amounts of Cu(OH)42- in solution and the Cu(OH)2(aq) species could only be detected in the regression processes at ≤50°C. However, the presence of CuOH+ and Cu(OH)3- was established unambiguously from 25°C to 350°C. The solubility of CuO(cr) was found to be higher than that of Cu2O(cr) at ambient conditions, except at very high pH, whereas at 350°C Cu2O(cr) was the more soluble phase in oxygen-free water. General agreement was found between the measured solubilities in steam under mainly sub-critical conditions and those from a number of previous studies in super-critical water, albeit within the inherently large scatter. The solubility CuO(cr) in steam was modelled as a function of steam density. Only the neutrally charged molecule Cu(OH)2(aq) is thought to partition between the phases in the absence of significant concentrations of complexing anions.

Solubility of CuO(s) in highly alkaline solutions

The solubility of tenorite, CuO(s), has been measured at 25°C and 60°C as a function of total hydroxide concentration, [OH−]T, at constant ionic strength (I=5 or 6molkg−1) in Li(OH,ClO4)(aq) and Na(OH,ClO4)(aq) media. Additional measurements were also made in highly concentrated (≥6molkg−1) NaOH(aq) and KOH(aq). The solubility (S) of CuO(s), measured as the total concentration of dissolved Cu(II) by atomic absorption spectroscopy, decreased at approximately constant [OH−]T in the order LiOH≫NaOH>KOH and increased with temperature and [OH−]T in all media. Plots of log S against log [OH−]T were linear with a slope of ~2.0, indicating, consistent with UV–Vis spectra, that the only significant Cu(II) species in solution was Cu(OH)42−(aq) under all conditions studied. Detailed analysis indicates that previous studies overestimated S because of the presence of fine particles of CuO(s). Using equilibrium constants and SIT parameter values derived from the present experimental data, the solubility of CuO(s) could be described with good precision up to the highest hydroxide concentrations investigated in all media.

Effects of cupric chloride and tamrabhasma, a traditional Indian preparation of copper, on eicosanoid production by human gastric and colonic mucosa.

Tamrabhasma is a traditional copper oxide-containing Indian preparation which has anti-ulcer activity. We have studied the effect of tamrabhasma and CuCl2.2H2O on prostaglandin formation by human gastric and colonic mucosa and submucosa, as prostaglandins have mucosal protective activity, and their release may contribute to the anti-ulcer effect. With the gastric mucosa, tamrabhasma 10 micrograms mL-1, but not 0.1 or 1 microgram mL-1, increased prostaglandin E (PGE) concentration by 38% (P < 0.05), with little or no effect on 6-keto-PGF1 alpha, thromboxane B2 or the leukotriene (LT) LTC4/LTD4. CuCl2.2H2O (10 micrograms mL-1) increased 6-keto-PGF1 alpha by 46% (P < 0.05), but 0.1, 1, 50 and 250 micrograms mL-1 did not significantly affect any of the prostanoids, and only the highest concentration reduced the amount of LTC4/LTD4. In the colon mucosa, tamrabhasma (0.1-10 micrograms mL-1) or CuCl2.2H2O (10-50 micrograms mL-1) increased all the prostanoids and this effect was greater than in the gastric mucosa but there was no significant change in LTC4/LTD4. CuCl2.2H2O showed a bell-shaped concentration-effect curve, with no significant effect at lower and higher amounts. Indomethacin (0.1-10 micrograms mL-1) caused a concentration-dependent reduction in the prostanoid amounts. The effect of tamrabhasma was probably not only due to the presence of Cu2+, as tamrabhasma was more effective than CuCl2.2H2O alone; in addition the solubility of CuO is very low. Increased prostanoid levels might explain, at least partly, the gastric mucosal protection by tamrabhasma. The results in the colon, however, raise the possibility that tamrabhasma should be examined for the treatment of inflammatory bowel disease.

CuO Solubility in Alkali-Chloride Melts

Used method of isothermal saturation solubility of copper (II) oxide in alkali and alkaline-salt melts has been investigated at temperature range 673 - 873 K. It was determined that solubility of CuO in the order of melts LiOH < NaOH < KOH are increased. The effect of temperature on the CuO solubility in alkali melts are described of the equation of straight line lnC = A + B/T, where C is concentration of the CuO in the melts, mole fract., A and B are constants. The salt additions of lithium chloride, sodium chloride and potassium chloride to sodium hydroxide melt are decreased the solubility of copper (II) oxide.

The Solubility of Some Transition Metal Oxides in Cryolite-Alumina Melts: Part III. Solubility of CuO and Cu2O

The solubilities of CuO (at 1 atm oxygen pressure) and of Cu2O (in equilibrium with Cu) were measured in cryolite-alumina melts at 1020 °C as functions of the alumina content of the melt, and of the NaF/AlF3 ratio in melts saturated with alumina. The results enable separation of the contributions of Cu(I) and Cu(II) species in solution, and are interpreted in terms of the solute species CuF, CuAlO2, and Na2CuF4. In alumina-saturated melts with NaF/AlF3 = 3 the solubility of CuO is given by log (wt% Cu) = −9664/T + 7.0128, where T is temperature in kelvins, and of Cu2O by log (wt% Cu) = −8677/T + 6.173.

Phase equilibria of the MgO-Cu 2O-CuO system

Phase equilibria of the MgO-Cu 2O-CuO system have been determined in air at temperatures ranging from 850 to 1100 °C. The starting compositions ranged from 0 to 100% Mg in (Mg 1 − xCu x)O. CuO was quite soluble in MgO. The solubility of CuO in MgO at 850 °C was about 9% and at 1050 °C was about 20%. The only known ternary Guggenite phase had a composition of Cu 2MgO 3. The Guggenite phase exists in three forms, namely, Guggenite A (G A, orthorhombic, space group Pmmn(59)), Guggenite B (G B, orthorhombic, space group I(0)), and Guggenite X (G x, monoclinic). Guggenite A was obtained as a single phase in air at X CuO = 67% (i.e., 67% CuO and 33% MgO) and 1000 °C. It undergoes a phase transition to the Guggenite X phase when it is heated above 1050 °C. The Guggenite B phase was obtained in a mixture at X CuO = 75% and at temperatures above 1050 °C. MgO was not found to be soluble in CuO. For samples with x cuo ≥ 67%, the Guggenite A phase coexisted with tenorite (CuO, monoclinic) at temperatures ≤ 1000 °C and above 1021 °C, it was in equilibrium with cuprite (Cu 2O, cubic). For CuO compositions between 20% and 67%, a mixture of Guggenite A phase and the periclase phase (MgO, cubic) was obtained at temperatures ≤ 1000 °C. The decomposition of Cu 2MgO 3 (Guggenite A) phase was determined at several oxygen partial pressures and the Gibbs free energy of formation of this phase was also calculated.

The influence of dislocations on the nonlinearity of ZnO:Cu varistors

Zinc Oxide doped only with Cu shows highly nonlinear I–V characteristics. Microstructural observations of these ceramics reveal the presence of extensive dislocation network. The transmission electron microscopy (TEM) indicates that the dislocations are impurity decorated which arise as a result of limited solubility of CuO in ZnO. It is envisaged that the depletion region is generated in the region containing the dislocations because of the presence of acceptor type traps.

Ground tests of piasecki 59K VTOL

The solubility of tenorite, CuO(s), has been measured at 25 °C and 60 °C as a function of total hydroxide concentration, [OH−]T, at constant ionic strength (I = 5 or 6 mol kg− 1) in Li(OH,ClO4)(aq) and Na(OH,ClO4)(aq) media. Additional measurements were also made in highly concentrated (≥ 6 mol kg− 1) NaOH(aq) and KOH(aq). The solubility (S) of CuO(s), measured as the total concentration of dissolved Cu(II) by atomic absorption spectroscopy, decreased at approximately constant [OH−]T in the order LiOH ≫ NaOH > KOH and increased with temperature and [OH−]T in all media. Plots of log S against log [OH−]T were linear with a slope of ~ 2.0, indicating, consistent with UV–Vis spectra, that the only significant Cu(II) species in solution was Cu(OH)42 −(aq) under all conditions studied. Detailed analysis indicates that previous studies overestimated S because of the presence of fine particles of CuO(s). Using equilibrium constants and SIT parameter values derived from the present experimental data, the solubility of CuO(s) could be described with good precision up to the highest hydroxide concentrations investigated in all media.