Studies on fluorination of Fe_3O_4 (magnetite) by NH_4HF_2

摘要

Fluorination of magnetite (Fe_3O_4) by NH?HF? was investigated using simultaneous thermogravimetry and differential thermal analysis (TG-DTA), and observing the morphology and phase changes using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray difiractometry (XRD). The results indicate that fluorination with the involvement of oxygen begins at room temperature, peaks at 178.40 deg C, and is completed at 2000 deg C with the formation of only (NH_4)_3FeF_6. On heating, (NH_4)_3FeF_6 gradually releases NH_4F by the formation of NH_4FeF_4 at 2590 deg C, then (NH_4)_(0.18)FeF_3 at 3270 deg C, and finally FeF? with minor FeF? at 4000 deg C due to the partial reduction of Fe (III) to Fe (II). At 5500 deg C, FeF? is oxidized to FeOF/Fe_2O_3.