Home – Home – Jornals – Chemistry for Sustainable Development 2016 number 6

The synthesis of demanded chromium (III) molybdate by the solid phase method based on the Cr₂(SO₄)₃-Na₂CO₃-MoO₃ system, in which the initial mixture of reagents at the thermal treatment may transform into triple mutual exchange (Na, Cr//CO₃, SO₄) and displacement (Na(Cr)CO₃(SO₄)-MoO₃) systems was proposed. The thermodynamic parameters of the indicated reactions were studied and it was demonstrated that processes associated with the synthesis of Cr₂(MoO₄)₃ were characterized by the significant negative Gibbs energy D G_T , and this is fundamentally for achieving the desired goal. A special role in this is played by the interaction of Cr₂(SO₄)₃ with Na₂CO₃, resulting in the formation of a thermodynamically quite unstable phase - the transition state Cr₂(СO₃)₃ that is a donor of highly defective Cr₂O₃. The latter intensively reacts with thermally activated MoO₃ by forming chromium (III) molybdate. Alongside with thermodynamic data, the results of kinetic studies of the reagent reaction in the Cr₂(SO₄)₃-Na₂CO₃-MoO₃ system depending on temperature (500 and 600 °С) are given. Reaction rate constants and activation energies were calculated according to them, and complete correlation with regularities of a change in isobaric potentials of appropriate processes was demonstrated. The synthesis of Cr₂(MoO₄)₃ was carried out by the thermal treatment of a stoichiometric mixture of the reagents with the specified mass at 600 °C (precision of ±10 °C) during 1.5-2.0 h followed by leaching and isolating the Cr₂(MoO₄) preparation. It was identified by XPA, chemical and sedimentation analysis methods.