An Experimental Study Of Dissolution Rates Of Muscovite In Pure Water At High Temperatures And High Pressure

Steady-state muscovite reaction kinetics in pure water have been measured using flow through reactor at temperatures from 23 to 400 ℃ and at 23MPa,whereas each temperature take four flow rates 2.0、2.5、30、3.5ml/min. The muscovite used in these experiments has a composition (Na0.1,K0.82)Mg0.09Ti0.01Fe0.09Al1.73Si1.77O10 (OH6.793, F0.41). The measurement experiments were performed at conditions far from equilibrium in Continuous Stirred Tank Reactor.The results of experiments indicate that the dissolution rates of elements Na、Si、 Al、Ti、V increasing with the temperatures increasing from 23 ℃ to 350 ℃ and then decease at 400 ℃. The release ratio of elementsMi/Si in our experiments indicates that the release ratio changes from positive incongruent dissolution to negative as increasing temperature. At 200℃, the release ratios of Na/Si、K/Si、Mg/Si、V/Si、 Ba/Si are almost equal to their stoichiometric numbers of the corresponding elements in the mineral. That fact demonstrate that congruent dissolution occurs at 200 ℃. When the temperature was fixed, the pH of the output solution almost increases with respect to the increase of the dissolution rates of element Si, but at 300 ℃,the pH of the solution deceases with the increase of the dissolution rates of Si. The rates in the present study at 300 ℃ are consistent with also find that at temperature 23 ℃、200 ℃、300 ℃ and 400 ℃, the rates of muscovite also depend on reactive fluid SiO2 activity consistent with:In low temperatures, as muscovite reacted with water, the H+ adsorption in the surface of the mineral——H+ -metal ion exchange occurs at surface, and the cations Na+、K+、Mg2+, etc. are removed from the surface of muscovite. As the temperature increases, tetrahedral Si-O bond and octahedral Al-0 bond break, hydration is dominant. and the release rate of Si. Al is increased.