Experimental study of natural pyrochlore and niobium oxide solubility in Alkaline hydrothermal solutions

Abstract

The concentration and temperature dependences of pyrochlore and Nb oxide solubility in Na₂CO₃ and Na₂СO₃ + NaF aqueous solutions with concentrations from 0.01 to 2.0 m at 300–550°C and 50 and 100 MPa (the Co–CoO buffer) are studied. It is established that the Nb equilibrium content in the solution increases at 550°C and 100 MPa with an increase in mNa₂CO₃ and reaches the value of 10^–4m. The Nb₂O₅ solubility almost does not change as the concentration of Na₂CO₃ increases and is found within 10^–6 to 10^–5.5m.