Fusions at lower temperatures and extended periods

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Introduction

Titanium dioxide (TiO2) is a white powder with high opacity, brilliant whiteness, excellent covering power and resistance to colour change. These properties have made it a valuable pigment and opacifier for a broad range of applications in paints, in the paper industry, in fibbers, cosmetics, sunscreen products, toothpaste, foodstuffs, optical coatings, beam splitters and anti-reflection coatings. It is also used as support catalyst. Its use as a humidity sensor and high-temperature oxygen sensor is under consideration. Titanium dioxide is also a starting material for titanium metal production. Titanium metal is applied in construction projects, aircraft, spacecraft, turbine engines and missiles. The metal is also used in the chemical industry (Alemany et al., 2000; Barksdale, 1966; Mellor, 1960; Nielsen and Chang, 1996; Samuel et al., 2005; Stamper, 1970; Stanaway, 1994).

Aim of the Study

The aim is to establish and optimise an alternative route to the traditional sulfate route. The new method will enable the sulfate process to treat ores previously considered economically untreatable, such as anatase (90–95% TiO2), titanomagnetites [Fe(Ti)Fe2O4] and other low grade ilmenites with high contents of calcium and magnesium (Yuan et al., 2005).

Methodology

The proposed route consists in fusing ore with an alkali compound. The identity of the fused products was verified by X-ray diffraction (XRD). After fusion, the fused product was subjected to a leaching process. The leachate was subjected to an acid hydrolysis and the hydrolysate was reacted with sulphuric acid. The product was dissolved in water and unreacted solids were filtered out. The aqueous solution was subjected to elemental analysis by inductively coupled plasmamass spectrometry (ICP-MS) for iron and titanium determination. Accessory characterisation techniques such as scanning electron microscopy (SEM) and Fourier transform infra-red spectrometry (FT-IR) were used.

Rationale

According to Pong et al. (1995), for a process to be commercially acceptable, it should be environmentally benign, result in minimal chemical loss through recycling, be able to use all grades of ores, produce manageable intermediate products and be economically favourable.

Declaration
Abstract
Dedication
Acknowledgements
1 Introduction
1.1 Aim of the Study
1.2 Methodology
1.3 Rationale
1.4 References
2 Literature Review
2.1 Titanium Minerals and Ores
2.1.1 Rutile
2.2 Ilmenite
2.2.1 Titanium Minerals Occurrence
2.2.2 Mining
2.3 Synthetic Feedstock
2.3.1 Titanium slag
2.3.2 Synthetic rutile
2.4 Titanium Processing Technology Overview
2.4.1 The Sulfate Process
2.4.2 The Chloride Process
2.4.3 Surface Crystal Treatment
2.5 Other Processes
2.5.1 Direct leaching
2.5.2 Reduction and leaching
2.5.3 Dissolution
2.5.4 Oxidative roasting/fusion
2.5.5 Remarks on Titania Technology
2.6 Phase Diagrams
2.6.1 System Na2O–TiO2
2.6.2 System Na2O-TiO2-Fe2O3
2.6.3 Comments on the phase diagrams
2.7 The Proposed Process
2.7.1 The Richter Process
2.7.2 The de Wet Process
2.7.3 Description of the New Process
2.7.4 Benchmarks of the Proposed Process
2.8 References
3 Experimental
3.1 Characterisation Techniques and Materials
3.1.1 X-ray powder diffraction (XRD)
3.1.2 X-ray fluorescence (XRF)
3.1.3 FT-IR absorption
3.1.4 Thermogravimetric analysis
3.1.5 Particle size distribution
3.1.6 Scanning electron microscopy
3.1.7 Materials
3.2 Fusion Temperature
3.3 Fusion Samples
3.4 Optimisation of Fusion Stage
3.5 Leaching
3.6 Leaching Solution
3.7 Hydrolysis
3.8 Sulfation Process
4. Results and Discussions
4.1 Material Composition
4.2 Thermogravimetric Analysis
4.3 Fusion Results
4.3.1 Fusions at lower temperatures and extended periods
4.3.2 Effect of fusion temperature
4.3.3 Effect of mole ratio and time
4.3.4 Fusions under NaOH starved conditions
4.4 FT-IR Analysis
4.5 Scanning Electron Microscopy
4.6 Ilmenite Alkali Fusion Reaction
4.7 Kinetics of the Ilmenite Alkali Fusion Reaction
4.7.1 Theoretical Background
4.7.2 Kinetic Analysis of Alkali Fusion Reaction
4.8 Optimisation of the Fusion Process
4.8.1 Effect of particle size
4.8.2 Effect of mole ratio
4.8.3 Effect of time
4.8.4 Effect of temperature
4.9 Reagent Consumption
4.10 Optimisation of the Leaching Process
4.10.1 Effect of solid:liquid ratio
4.10.2 Effect of time and temperature
4.10.3 Batch leaching
4.10.4 Kinetics of the leaching process
4.11 Optimal Hydrolysis pH
4.12 Sulfation Process
4.13 Trials with Anatase
4.14 Summary of the Discussions
4.15 References
5 Conclusions
5.1 Fusion Step
5.2 Leaching Step
5.3 Other Steps
5.4 Recommendations