Diana Rabadjieva

Solubility and Crystallization in the System MgCl2–MgSO4–H2O at 50 and 75°C

The system MgCl2–MgSO4–H2O has been investigated experimentally and modeled thermodynamically according to the Pitzer method at 50 and 75°C. It was found that, even when seemingly all requirements for reaching the stable thermodynamic equilibrium are fulfilled, the crystallization of higher hydrates as metastable phases is possible, and cannot be avoided in each crystallization field of a stable lower hydrate of magnesium sulfate. Crystallization of MgSO4 · x H2O (x = 1, 4, 6) and MgCl2 · 6 H2O at 50°C and of MgSO4 · H2O and MgCl2 · 6 H2O at 75°C as stable phases has been observed. Three metastable crystallization fields of MgSO4 · x H2O (x = 4, 6, 7) have been detected at 50°C and two of MgSO4 · x H2O (x = 4, 6) at 75°C. The results obtained and the contradictions existing in the literature with respect to the solubility and the crystallizing solid phases are discussed in terms of the crystal structures.

Kinetics of copper slag oxidation under nonisothermal conditions

The kinetics of air copper slag oxidation under nonisothermal conditions is studied using simultaneous TG–DTA at a varying heating rate of slag and flow rate of the oxidizing gas flux. The values of the kinetic parameters, activation energy and pre-exponential factor, have been determined based on: data from DTA by the methods of Kissinger and Ozawa; data from TG using an isoconversion method and the computation procedures of Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose. No relationship between the kinetic parameters and the oxidation gas flow rate has been established. The changes of the phase composition with temperature are investigated by X-ray powder diffraction analysis on the basis of data obtained for the products formed at the different stages of the oxidation process. The morphology of the oxidized slag as well as the elements distribution is studied by electron microscopy and EDS analysis.

Chemical speciation in mining affected waters: the case study of Asarel-Medet mine

The inorganic chemical species in Maresh and Luda Yana rivers affected by the Cu– Mo Asarel-Medet mine, Bulgaria were determined during a low-flow and a high-flow period. The mining activities, the weathering and the oxidation processes strongly influenced the physicochemical processes in the whole water system. The main pollution source was a small lake receiving the acid effluents of the mining activities. High levels of SO42 − , Cu, Mg, Al, Mn and Fe were determined at the mining polluted and affected stations. Cu2 +  and CuCO30 species (1:1) were present in the reference waters and Cu2 +  and CuSO40 species (1:1) in the polluted and affected waters; Cu2 +  species was dominating downstream. Me2 +  followed by

Sea-water solubility phase diagram. Application to an extractive process

\rm{MeSO}_{4}^{\kern3pt{0}}

Chemical speciation of inorganic pollutants in river–estuary–sea water systems

(Me = Mn, Zn, Cd and Pb),

Mg- and Zn-modified calcium phosphates prepared by biomimetic precipitation and subsequent treatment at high temperature

\rm{PbCO}_{3}^{\kern3pt{0}}

Chemical speciation in natural and brine sea waters

and

Chemical speciation in fresh, saline and hyper-saline waters

\rm{PbHCO}_{3}^{\kern3pt{+}}

Thermodynamic study of the aqueous rubidium and manganese bromide system

species as well as

On the crystallization kinetics of highly soluble salts

\rm{Fe(OH)}_{2}^{\kern3pt{+}}