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Title: Physical and Process Chemistry of Alkali Roasting of Titaniferous Minerals
Author: Lahiri, Abhishek
ISNI:       0000 0001 3603 7831
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2008
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Worldwide titanium dioxide pigments are extracted from ilmenite, anatase and rutile minerals by sulphate and chloride processes. The disadvantages ofthe two processes are that each of them produces a large volume of toxic and hazardous wastes which cannot be disposed without an additional treatment step which is a difficult and expensive process. The shortage of high-grade titaniferous ores has not only increased the production cost but also reduced the efficiency of the current sulphate and chloride processes. The present investigation shows a new beneficiation· process based on the roasting of titaniferous minerals followed by leaching. Prior to alkali roasting, the phase decomposition of ilmenite was studied in detail using TGA, DTA, SEM and TEM techniques under different atmospheric conditions. Roasting of ilmenite ore with alkali was conducted with different alkalis such as sodium carbonate, bicarbonate and hydroxide. Similar experiments were conducted by changing the cation from. sodium to lithium and potassium to understand the influence of different cations on the roasting chemistry, removal of major, minor and trace impurities. During roasting, process parameters such as alkali to ore ratio, roasting time and temperature were varied and the change in the crystal structure were ascertained using XRD, SEM, and EDX techniques. The roasting reaction kinetics was analysed and thermodynamic calculations were carried out to study the various roasting reactions which led to the understanding of the roasting mechanism. Alkali roasting was followed by reduction leaching in which the roasted product was leached in a solution of oxalic and ascorbic acids to produce synthetic rutile. The reaction mechanism of the leaching process was studied in detail using FTIR. The results of this research work show a new method of beneficiating titaniferous ores by removing most of the impurities including the rare earths from the mineral ore to produce synthetic rutile of greater than 95% Ti02 concentration.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available