Characterization study of novel process and high purity-magnesium products recovered from brine and bitterns = 브라인(brines)으로부터 회수된 고순도 마그네슘 산물 및 공정의 특성연구

다국어 초록 (Multilingual Abstract)

Magnesium is known to be the lightest among the light metals. Due to its light weight and low density, Mg and its compounds have extensively been used in various applications such as in automotive, aerospace, electronics, agricultural and chemical industries, etc.
Currently, magnesium is recovered from two major sources, namely seawater/brines/bittern and Mg – containing minerals. In this study, the recovery of Mg as carbonate was conducted using Uyuni salar brine (containing ~13.3 g/kg Mg) from Bolivia and bittern (containing ~41.1 g/kg Mg).
Stabcal software was first used to investigate the stability of various magnesium species and Mg carbonate during the precipitation. Depending on the pH of solution, Stabcal predicts the formation of various Mg products such as Mg oxalate, magnesite, hydromagnesite, and magnesium hydroxide.
The Mg recovery from Uyuni salar brine was conducted at different stoichiometries of 0.6 – 2.4:1 (corresponding to CO3/Mg molar ratio of 0.5 – 1.9:1) in the meanwhile a stoichiometry of 1:1 was used for the bittern. After precipitation, the solids were washed by distilled water prior to drying at 25, 65, and 100oC. X-Ray Diffraction results obtained for the samples recovered from brine as well as bittern confirmed the formation of dypingite – (MgCO3)4.Mg(OH)2.5H2O or (MgCO3)4.Mg(OH)2.8H2O at ambient temperature precipitation and drying while the drying at 65oC and 100oC formed hydromagnesite – (MgCO3)4.Mg(OH)2.4H2O.
Field Emission – Scanning Electron Microscopy analysis showed that a sheet – like morphology was yielded for the hydromagnesite precipitated from the low – oxalate brine as well as bittern at room temperature precipitation and 100oC drying.
Differential Thermal Analysis of dypingite – (MgCO3)4.Mg(OH)2.5H2O showed its total mass loss experimentally measured as 58.7 ± 0.1% including adsorbed water, equivalent to 41.2 ± 0.1% MgO in the residue. The total mass losses of hydromagnesite obtained at 65oC and 100oC drying were in the range of 54.8 – 56.7%, corresponding to 45.2 – 43.3% MgO in the residue. Theoretical mass losses of dypingite and hydromagnesesite should be 58.5% and 56.8%, respectively, representing 41.5% and 43.2% MgO in the residue.
Chemical analysis showed that the hydromagnesite obtained from low – oxalate brine had a grade of 23.3 – 24.3%, corresponding to a content of 38.7 – 40.3% MgO. Meanwhile a grade of 25.3 – 25.9% Mg (~41.9 – 42.9% MgO) was yielded for hydromagnesite recovered from the high-oxalate brine and a 25.7 – 25.9% Mg (~42.7 – 42.9% MgO) was from bittern. Theoretical hydromagnesite should contain 26.0% Mg, representing 43.1% MgO.
Differential Scanning Calorimetry analysis showed that the net endothermic energy released (heat adsorbed) during decomposition of hydromagnesite recovered from the low-oxalate brine was in the range –1173.1 to –1196.1 J/g. In the meanwhile those from high-oxalate brine and bittern were from –972.1 to –1073.8 J/g, and –585.1 to –591.2 J/g, respectively.
Hydromagnesite obtained from the low-oxalate brine was found to have a highest endothermic energy.

목차 (Table of Contents)

• ACKNOWLEDGEMENTS v
• LIST OF FIGURES vi
• LIST OF TABLES x
• LIST OF PUBLICATIONS xiii
• ABSTRACT xv
• CHAPTER 1. INTRODUCTION 1
• 1.1. Background 1
• 1.2. Objectives 3
• CHAPTER 2. LITERATURE SURVEY 5
• 2.1. Background 5
• 2.2. Sources of magnesium 6
• 2.2.1. Magnesium from magnesium – containing minerals 6
• 2.2.2. Magnesium from magnesium – containing brines 9
• 2.3. Resources and Reserves 11
• 2.4. Applications 12
• 2.4.1. Use of Mg metal 12
• 2.4.2. Use of magnesia 13
• 2.4.3. Use of Magnesium chemical products 14
• 2.5. Market 15
• 2.6. Process technologies 18
• 2.6.1. Production of Mg metal 18
• 2.6.2. Production of magnesia (CCM, DBM, and EFM) from ores 22
• 2.6.3. Production of magnesia from brines 23
• 2.6.4. Production of chemical magnesium products from brines 24
• 2.7. Fundamental studies and characterization of Hydrated Magnesium Carbonate (HMC) 32
• CHAPTER 3. MATERIALS AND EXPERIMENTAL PROCEDURES 40
• 3.1. Materials and chemicals 40
• 3.1.1. Materials 40
• 3.1.2. Chemicals 40
• 3.2. Analytical methods and material characterization 40
• 3.2.1. X-Ray Diffraction 40
• 3.2.2. Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) 41
• 3.2.3. Differential Scanning Calorimetry (DSC) 41
• 3.2.4. Inductively Couple Plasma – Optical Emission Spectrometer (ICP-OES) 41
• 3.2.5. Ion Chromatography (IC) 42
• 3.2.6. Alkalinity (Titration technique) 42
• 3.2.7. Field Emission – Scanning Electron Microscope (FE-SEM) 42
• 3.3. Experimental procedures 43
• CHAPTER 4. THERMODYNAMIC MODELING USING STABCAL PROGRAM 47
• 4.1. STABCAL program introduction 47
• 4.2. STABCAL modeling for calcium removal as oxalate from Uyuni salar brine 48
• 4.3. STABCAL modeling for the magnesium precipitation (without removing oxalate excess) 49
• 4.4. STABCAL modeling for the magnesium precipitation (after the removal of oxalate excess) 51
• 4.5. STABCAL modeling for the distribution of C (corresponding to CO3) 52
• CHAPTER 5. EXPERIMENTAL RESULTS AND DISCUSSION 54
• SECTION 5.1. RECOVERY OF MAGNESIUM PRODUCTS FROM UYUNI SALAR BRINE 54
• 5.1.1. Magnesium carbonate recovery from Uyuni salar brine 54
• 5.1.2. Two – stage process for producing high – oxalate Mg product 54
• 5.1.2.1. X-Ray Diffraction (XRD) analysis of Mg carbonate precipitates 56
• 5.1.2.2. Thermal Gravimetric Analysis (TGA) of Mg carbonate precipitates 63
• 5.1.2.3. Differential Scanning Calorimetry (DSC) analysis of Mg carbonate precipitates 68
• 5.1.2.4. Chemical analysis 71
• 5.1.2.5. Conclusion 72
• 5.1.3. Three – stage process for producing low – oxalate Mg product 74
• 5.1.3.1. Characterization of Ca oxalate obtained after Ca removal 74
• 5.1.3.2. Characterization of Mg oxalate obtained after the removal of remained oxalate 77
• 5.1.3.3. Characterization of Mg carbonate products obtained from low-oxalate brine 79
• 5.1.3.3.1. X-Ray Diffraction (XRD) analysis of Mg carbonate precipitates 79
• 5.1.3.3.2. Thermal Gravimetric Analysis (TGA) of Mg carbonate precipitates 81
• 5.1.3.3.3. Differential Scanning Calorimetry (DSC) analysis of Mg carbonate precipitates 84
• 5.1.3.3.4. Field Emission – Scanning Electron Microscopy (FE-SEM) analysis of Mg carbonate precipitates 86
• 5.1.3.3.5. Chemical analysis 88
• 5.1.3.3.6. Conclusion 89
• SECTION 5.2. RECOVERY OF MAGNESIUM PRODUCTS FROM BITTERN 91
• 5.2.1. Magnesium carbonate recovery from bittern 91
• 5.2.2. Characterization of Mg carbonate products from bittern 91
• 5.2.2.1. X-Ray Diffraction (XRD) analysis of Mg carbonate precipitates 92
• 5.2.2.2. Thermal Gravimetric Analysis (TGA) of Mg carbonate precipitates 94
• 5.2.2.3. Differential Scanning Calorimetry (DSC) analysis of Mg carbonate precipitates 98
• 5.2.2.4. Field Emission – Scanning Electron Microscopy (FE-SEM) analysis of Mg carbonate precipitates 100
• 5.2.2.5. Chemical analysis 102
• 5.2.3. Quality of waste discharge 103
• 5.2.4. Conclusion 105
• SECTION 5.3. COMPARISON OF EXPERIMENTAL RESULTS AND THERMODYNAMIC MODELING DATA 106
• 5.3.1. Calcium removal as oxalate from Uyuni salar brine 106
• 5.3.2. Excess oxalate removal as magnesium oxalate from Uyuni salar brine 106
• 5.3.3. Magnesium carbonate precipitation from Uyuni salar brine after the excess oxalate removal 106
• CHAPTER 6. GENERAL CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK 108
• 6.1. General conclusions 108
• 6.2. Recommendations for future work 109
• REFERENCES 111
• ABSTRACT (Korean) 132
• APPENDIX 134