Grant: Collaborative Research and Development Grants

Molten Salt Hydrates (MSHs) are promising media for chemical metallurgical processes. These are highly concentrated salt solutions, for example, molten FeSO4-7H2O or CaCl2-4H2O where the polar water molecule is bound to the salt. This gives MSHs a number of unusual properties that put them in a different class than brines or molten salts. MSHs can exist as liquids at temperatures above 300oC at atmospheric pressures, albeit with some level of humidity. MSHs also have both a high heat capacity and a large heat of hydration. These properties suggest diverse applications and at higher temperatures compared to those in aqueous processing. Despite this exciting potential, molten salt hydrates have had no systematic study. Most of the research that has been done is sporadic, exploring a few aspects and applications of MSHs with little actual elucidation of their fundamental chemistry. Investigations have been done on MSHs for heat storage, using both sensible heat and latent heat of hydration. Some MSHs have been explored as quasi-aqueous media for reactions, including serpentine carbonation and cellulose derivitization. This more applied part of the project (MSc) will seek to employ the corrosive nature of magnesium chloride MSHs in leaching refractory, magnesium-rich laterite nickel ores, and then using hydrolysis to achieve an acid recycle loop. This project will also serve as a demonstration of the potential of these systems. At present, magnesium-rich ores can presently only be treated by melting in electric furnaces, a costly process requiring enormous amounts of energy. A systematic array of leaching tests will be performed on laterite ore samples to determine the advantages of the use of MSHs for mineral processing and upgrading. Simultaneously, a series of experiments by the PhD student will examine more fundamental aspects of molten salt hydrates to better understand the role of the type of salt to the properties and water activity in the system. This work will provide data for a new molten salt hydrate thermodynamic model that would allow predictions of the interaction of MSH with metal oxide systems at a variety of temperatures.