Solubility of β-FeF₃·3H₂O in Mixtures of Nitric and Hydrofluoric Acid

Abstract

The solubility of β-FeF 3 ‚3H 2 O has been measured in solutions with different concentrations of nitric acid (0 to 7 m) and hydrofluoric acid (1 to 6 m) at the temperatures of (30, 40, and 50) °C. The total iron concentration at equilibrium was measured with inductively coupled plasma (ICP) spectroscopy. The solubility was evaluated in terms of the stepwise complexation of iron by fluoride ions at different ionic strength and temperature. The solubility of β-FeF 3 ‚3H 2 O increases with decreasing concentration of HF and HNO 3 and increasing temperature.

Determination of iron and chromium fluorides solubility for the treatment of wastes from stainless steel mills

“…When higher temperatures are considered, logarithmic variation is considered as done in the literature [19]. Thermodynamic constants for the considered equilibriums are shown in Table 1.…”

“…[20] and used by Ref. [19], revealed that new Table 3 for optimized model. Ionic strength of a typical SPL solution is about 3-4 mol kg −1 .…”

“…Iron forms FeF 3 (aq), which would precipitate, mainly as ␤-FeF 3 (s) [19]. This process is too slow, so it is not considered when modelling in normal conditions and SPL management.…”

“…Although reaction (7a) is too slow in SPL, achieving equilibrium composition in several weeks, its solubility product is calculated fromÖsterdahl and Rasmuson reported data [19]. In this reference equilibrium concentration is calculated with SSPEC, using equilibrium constants fitted for specific ionic strength and temperatures.…”

“…Previously, this model is compared with SSPEC (Stainless Steel Pickle Equilibria Calculation) used in other works [19,20] for solubility calculation.…”