Speciation, structure and hydration of solutes under hydrothermal conditions

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Many geological and industrial processes take place at conditions far beyond the range of conventional room temperature measurements. The objective of this proposal is to develop the knowledge base and theoretical understanding needed to describe the behaviour of aqueous systems at extremes of temperature and pressure encountered in electrical power stations, advanced nuclear reactors, geothermal ore bodies, deep-ocean hydrothermal vents, and the capture and sequestration of CO2. ******Sensitive flow calorimeters and densitometers, constructed of inert materials to withstand the corrosive conditions, will be used to determine the thermodynamic properties of simple electrolytes and organic molecules in liquid water at temperatures up to 400 oC and pressures as high as 350 atmospheres, to examine the effects of ionic charge and organic functional groups under conditions approaching the critical point of water. The form of the chemical species, and their equilibrium constants, will be determined by in situ measurements in novel high temperature, high pressure flow cells using UV-visible spectroscopy, Raman spectroscopy, calorimetry, densimetry and a one-of-a-kind, high-precision conductance apparatus, all capable of reaching sub-critical or supercritical conditions. These measurements will yield new insights into the fundamental nature of solute hydration, and solute-solute interactions. The project will also yield thermodynamic data, transport properties, semi-empirical models, and theoretical methods for predicting the properties and phase behaviour of aqueous inorganic and organic solutes in water-based geothermal systems and advanced industrial technologies that operate under extremes of temperature and pressure.******The program will focus on three areas: (i) basic research to understand the role of speciation and ion-ion interactions on the vapour-liquid critical locus and the lower critical solution temperature of electrolyte solutions above 250 oC; (ii) the thermodynamics and phase behaviour of CO2 and (CO2 + amine) solutions at intermediate and high temperatures relevant to carbon capture and geological sequestration; and (iii) the thermodynamic and kinetic stability of pre-biotic molecules required to model postulated mechanisms for the hydrothermal origin of life. The novelty in the work lies in the very extreme conditions being studied, the potential for identifying unusual effects, and the need to develop specialized instrumental techniques to obtain quantitative data for complex aqueous systems under these very aggressive conditions.