Thermodynamics of the Eu(III)-Mg-SO-HO and Eu(III)-Na-SO-HO systems. Part II: spectroscopy experiments, complexation and Pitzer/SIT models.

A time-resolved laser fluorescence spectroscopy (TRLFS) study was carried out to investigate the Eu(III)-SO complexation at room temperature over a wide range of NaSO concentrations (0-2 mol kg). Spectroscopic observations confirm the step-wise formation of the aqueous complexes Eu(SO), Eu(SO) and Eu(SO) over the investigated NaSO concentrations. Combining TRLFS data obtained in this study and solubility data reported in Part I of this work for the Eu(SO)-NaSO-HO and Eu(SO)-MgSO-HO systems, thermodynamic and activity models were derived based on the SIT and Pitzer formalisms.

Thermodynamics of the Eu(III)-Mg-SO-HO and Eu(III)-Na-SO-HO systems. Part I: solubility experiments and the full dissociation Pitzer model.

The solubility of Eu(III) was investigated under undersaturated conditions in acidic, dilute to concentrated MgSO and NaSO solutions at = (22 ± 2) °C. After attaining equilibrium conditions, solid phases were characterized by a multi-method approach, including X-ray diffraction (XRD), Raman and infrared (IR) spectroscopy, quantitative chemical analysis (ICP-OES) and thermogravimetric analysis (TG-DTA). A total of 45 solubility samples were investigated for the systems Eu(SO)-MgSO-HO (19 samples) and Eu(SO)-NaSO-HO (26 samples).

Mass diffusion and Soret coefficient measurements of triethylene glycol/water binary mixtures by dynamic shadowgraphy.

The investigation of the transport properties of binary fluid mixtures remains a topic of interest in relation to the more challenging studies of ternary mixtures. In fact, the study of the phase boundary limits of the Gibbs composition triangle can be the initial step for a more complete analysis of ternary mixtures. In this paper, we apply the dynamic shadowgraphy optical technique to study non-equilibrium fluctuations induced by the presence of a gradient of temperature and/or concentration in the triethylene glycol (TEG)/water system.

Thermodynamic evidence of giant salt deposit formation by serpentinization: an alternative mechanism to solar evaporation.

The evaporation of seawater in arid climates is currently the main accepted driving mechanism for the formation of ancient and recent salt deposits in shallow basins. However, the deposition of huge amounts of marine salts, including the formation of tens of metres of highly soluble types (tachyhydrite and bischofite) during the Aptian in the South Atlantic and during the Messinian Salinity Crisis, are inconsistent with the wet and warm palaeoclimate conditions reconstructed for these periods. Recently, a debate has been developed that opposes the classic model of evaporite deposition and argues for the generation of salt by serpentinization.