Abstract
The solubility of β-heh 3·3H 2U has been measured in solutions with a range of different hydrofluoric acid concentrations (2, 4 and 6 mol/kg) and constant nitric acid concentration (3 mol/kg) in order to calculate a solubility constant applicable at the present ionic strength and temperature. Crystal growth of β-FeF 3·3H 2O has been measured in 3molal hydrofluoric acid and 3molal nitric acid solutions at 50°C by performing seeded isothermal desupersaturation experiments (1 < S < 3). The supersaturation was recorded by taking out solution samples which were analysed for total iron concentration with inductively coupled plasma atomic emission spectrometry (ICP-AES). The true supersaturation driving force was estimated by a proper speciation to account for the complexation, using the software SSPEC and relevant stability constants. Parameters of a desired growth rate equation were estimated by fitting the supersaturation balance equation directly to the supersaturation measurements. The results show that growth of β-FeF 3·3H 2O follows a parabolic rate law (g= 2,0 ±0,2). The growth rate at S= 2 was found to be 4,6×10- 11 m/s (50°C). The growth order and the low value of the growth rate suggest that the rate is surface integration controlled.
| Original language | English |
|---|---|
| Article number | A-1 |
| Pages (from-to) | 17-22 |
| Number of pages | 6 |
| Journal | VDI Berichte |
| Issue number | 1901 I |
| Publication status | Published - 2005 |
| Externally published | Yes |