The dependence of monazite composition on HF concentration and T-P-X parameters of fluids (thermodynamic simulation)

Abstract

Thermodynamic modeling of the probable effect of fluoride on the lanthanide relationship in the REE component of the “conditional” monazite has been carried out by HCh computer code [Shvarov, 1999; Shvarov, Bastrakov, 1999]. The calculations were made at T-P-X parameters given in Table 1. Additional amounts of KOH and HCl were added to stabilize pH of the equilibrium solutions (see captions to x-axis). Modeling was the calculation of the equilibrium composition of solid phase associations and coexisting fluid, which formed since that solutions influenced on monazite in the presence of calcite. 5,07·10 mole monazite with REE was introduced into the system in the ratio of (mole of the corresponding phosphates): La – 1,3·10; Ce – 2,4·10; Pr – 2,7·10; Nd – 8,3·10; Sm – 1,17·10; Eu – 4,7·10; Gd – 9·10; Y – 9·10 and 0,01 mole CaCO3. Monazite association with REE-fluorite and REE-fluorapatite has been obtained in these near neutral slightly alkaline carbonatechloride solutions.