| In this thesis, the electrolysis techniques for producing solid barium ferrate (Ⅵ) and solid potassium ferrate (Ⅵ) were studied. The effects of technology parameters upon the features of these ferrates (Ⅵ), have been probed. Upon the base of orthogonal components experimental results, the optimum technique condition had been determined for producing solid barium ferrate (Ⅵ) and solid potassium ferrate (Ⅵ) respectively. The crystal structure and crystal morphology of solids K2FeO4 were detected by imaging plate with X-ray diffraction, scanning electron microscope (SEM). The crystal structure of solids K2FeO4 and BaFeO4 were detected by powder X-ray diffraction (XRD). The thermal decomposition process of solid K2FeO4, have been probed by in situ high temperature powder X-ray diffraction (XRD) and thermo-gravimetric-analysis (TGA) and differential thermal analysis (DTA). The main results are shown as follow.1. The results of orthogonal components experiments confirmed that the effects of different technology parameters e.g. the total concentration of NaOH and Ba(OH)2 and their respect concentration in the electrolyte, the electrolysis temperature and so on, up on different features of the produced solid ferrates, e.g. the solid barium ferrate yield, the purity of solid barium ferrate, current efficiency and so on, when using the mixed bi-components electrolyte made from NaOH and Ba(OH)2 for producing solid barium ferrate. The determined proper condition: temperature 40℃, the concentration of NaOH and Ba(OH)2 were 13M and 0.1M respectively.2. From the viewpoints of the solid barium ferrate yield, the purity of solid of barium ferrate, the molar ratio of Fe(Ⅵ) to Fe(T) in solid BaFeO4, comparing the results gained by using the mixed bi-components electrolytes made from NaOH and Ba(OH)2, and made form KOH and Ba(OH)2, the former was a more proper electrolyte for producing solid BaFeO4 than the later.3. From the viewpoints of solid potassium ferrate yield, purity of solid of potassium ferrate, molar ratio of Fe(Ⅵ) to Fe(T) in solid KFeO4, current efficiency, comparing the results gained by using the electrolyte of pure NaOH, the electrolyte of pure KOH, and the mixed electrolyte of KOH and NaOH respectively, the electrolyte of pure KOH was more proper serve as electrolyte for producing solid K2FeO4 than the pure NaOH electrolyte and than the mixed electrolyte of KOH and NaOH. The optimum condition determined was: temperature higher than 40℃, the concentration of KOH in the range of 13-16M.4. The results of Scan Electron Micrograph indicated that the single crystal ofsolid K2FeO4 can be directly separated from the anodic solution during the electrolysis without any other purification process, if using 14M KOH single component electrolyte and electrolyzing at 65 °C.5> The results of imaging plate with X-ray diffraction indicated that the crystal of K2Fe04 was belong to orthorhombic system and belong to the Pnma space group, FeO42" was just as a slight distorted normal tetrahedral structure, be directly separated from the anodic solution during the electrolysis without any other purification process, if using 14M KOH single component electrolyte and electrolyzing at 65 °C. The lengths of the four bonds between Fe and O in the cell structure of K2Fe04 were 1.644(6)A, 1.651(4)A, 1.651(4)A, 1.657(5)A respectively. The calculated density of solid K2Fe04 was Dc = 2.102 g/cm3o6. The results gained by the in situ high temperature powder X-ray diffraction (XRD) indicated that only two kinds of ferrates of Fe(VI) and Fe(HI) were found during the thermal decomposition process of solid K2Fe04 in the temperature range of 25 °C to 900 °C, there was not any other ironic compounds produced with the intermediate valance of iron.7. The results gained by powder X-ray diffraction (XRD) indicated that the powder XRD spectrograms of solid BaFeO4 and solid K2Fe04 produced by electrolysis were more consistent with the standard powder XRD collected in JCPDS, than that of them produced by chemical oxidation.8. The results gained by the thermo-gravimetric-analysis (TGA) and differential thermal analysis (DTA) indicated that: in the temperature range of 161 °C to 327 °C, there was only one loss weight process for K2Fe04 single crystal and the loss weight ratio was 8.9092%;in the temperature range of 720°C to 1091 °C, there was another loss weight process for K2Fe04 single crystal and the loss weight ratio was 28.7684 %.9. In order to sure the analytical results accuracy of solid BaFeO4 purity, the time for the reaction between BaFeO4 and Cr(OH)3 should be longer than 8 hours in 100 °C boiling water. Using concentrated chlorhydric acid to dissolve the sample for analysis the total iron in solid BaFeO4 always lead to positive error. The mixed acid of chlorhydric acid and nitric acid, with the total concentration of hydrogen ion keep in 12M, should be used to dissolve the sample for analysis the total iron in solid BaFeO4. The analytical results for solid K2Fe04, both for the purity and the content of total iron were nearly unaffected by these factors.
|
PDF Full Text Request