Thermodynamic constant of MgUO2(CO3)32- complex in NaClO4 and NaCl media using time-resolved luminescence spectroscopy, and applications to different geochemical contexts.

The formation constants and specific ion interaction coefficients of MgUO2(CO3)32 complex were determined in 0.1 to 1 mol kgw-1 NaCl and 0.1 to 2.21 mol kgw-1 NaClO4 media in the...

Investigation of Adsorption of Cobalt-phthalocyanine from Aqueous Waste Stream Using UVM-7/Ag

The effect adsorption of cobalt-phthalocyanine-3,4’,4”,4”’- tetrasulfonicacid tetrasodium salt [Co(tsPc)-4•4Na＋] onto UVM-7/Ag mesoporous material was investigated. In addition, X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorptiondesorption measurement were used to examine the morphology and the microstructure of the obtained composite. Various parameters including solution adsorbent dosage, contact time, initial dye concentration and temperature were systematically studied. Equilibrium data fitted well the Langmuir models; moreover, the fitness suggests that the adsorption be monolayer and physical in nature. Kinetic studies showed that the adsorption process could be better described by the Lagergren pseudosecond- order models. Thermodynamic constant values (ΔG < 0, ΔH< 0 and ΔS< 0) demonstrated that the adsorption reactions of Co(tspc)-4 onto UVM-7/Ag were feasible, spontaneous, and exothermic under the examined conditions.

The Role of the Interaction between Fe(III) and Cell Surface in the Accumulation of 67Ga by Tumor Cells

The study of the interaction between complexed iron and tumor cells in the presence of 67Ga-citrate indicates that a phenomenon of iron-binding related to the thermodynamic constant of stability of the iron complex, and a hydrolysis (or anion penetration) of the interaction product determine the uptake of 67Ga. The effects of various parameters such as ionic composition of the medium, nature of the iron complex, time of incubation and number of cells are discussed.

Cyclovoltammetric study of the homogenous keto-enol equilibrium of dihydroxyfumaric acid in acid and neutral media

The keto-enol equilibrium of dihydroxyfumaric acid (DHF) was investigated in acid and neutral buffer solutions by cyclic voltammetry. The keto-form decreases with increasing pH, so that in neutral region (pH = 6 - 8) the equilibrium is totally shifted to the enol-form of the acid. The thermodynamic constant, Kk, of the equilibrium: enol-DHF ⇄ keto-DHF, was estimated at different pH and temperatures. The thermodynamic parameters ΔG, ΔH, and ΔS of the above equilibrium were also determined in 0.5 M-H2SO4 solution.

Effects of salt concentration and counterion on stability of alkali ion-18-crown-6 complexes in aqueous and methanolic solution: A conflicting evidence from potentiometric and sodium-23 NMR studies

Contrary to expectation, the title effects observed concurrently by potentiometry with ion-selective electrode and by sodium-23 NMR spectroscopy are completely different. The potentiometric stability constants for the sodium ion-18-crown-6 complex (KISE) exhibit a very pronounced variation with the counterion, KISENaSCN > KISENaCl > KISENaOH, as well as with the sodium salt concentration, the KISENaSCN/KISENaOH ratio being about 1.5, 2.0, 5.0 and 20 in the 0.01, 0.1, 0.5 and 1.0 mol l-1 aqueous and about 2.0, 12, 600 and 2 500 in the 0.01, 0.1, 0.5 and 1.0 mol l-1 methanolic solution, respectively. Whereas, the corresponding spectroscopic stability constants, KNMR, are virtually insensitive to the changes of counterion as well as to the salt concentration the overall spread of the KNMR values being less than 3. Resolution for the conflicting evidence is provided in terms of the activity coefficients γML+, γM+, γL differentiating between the concentration (Kconc) and thermodynamic (Kth) stability constants in the relation Kconc = (γM+ γL : γML+) Kth. At variance with the current opinion it is shown that only KISE are clean concentration constants subjected to the γML+/γM+ γL variation, while KNMR are hybrids between the concentration and thermodynamic constant leaning assumedly to the latter (Kth). Concerning the powerful effect of counterion and salt concentration of KISE, it is attributed to a large variation of γML+. No satisfactory explanation can be, however, offered in customary terms of the Debye-Hückel theory.