Chemical Reaction Kinetic Experimental Study On Amphibole In Water At High Temperatures

Chemical kinetic experiment study on steady-state amphibole dissolution rates in aqueous solutions have been measured at temperatures from 25 to 350℃ and constant pressure of 24 MPa,and at the conditions far from equilibrium.Through the study we summarizes the kinetic characteristics of steady-state amphibole dissolution rates in aqueous solutions. Temperature is the main factors which controlling the dissolution rate, the dissolution is non-stoichiometric in most cases, while the different chemical elements of the amphibole are released at different rates in different temperature. The dissolution rates(Si) increase with temperature while below 300℃, reach a maximum at 300℃, and then decrease with temperature. p H value is a important factor affect the dissolution rates. The dissolution rate reach a maximum when pause time close to 100 min at 300℃, and when pause time close to 66 min at other temperatures. Water properties control the dissolution rates near critical state. The dissolution proceeds by the sequential removal of metals from the mineral structure; the order of the removal of each metal is dictated by the relative rates of breaking of each metal–oxygen bond. Octahedral Mi–O bonds break more rapidly than tetrahedral Si–O bonds while below 300℃, the opposite occurs while above 300℃.T=100℃, the dependence of the amphibole dissolution rates on activities of Ca, Mg, Fe and H+ in the fluid can be expressed by the relation: r = Aexp(-E/RT)[(aH+)2/aMi2+]0.5416T=300℃, Al3+, Na+, Si4+ are near stoichiometric, the dependence of the amphibole dissolution rates on activities of Al, Na, Si and H+ in the fluid can be expressed by the relation:r = Aexp(-E/RT)[(aH+)Zi /aMi Zi+]-0.108 Pre-exponential factor A=4.8029*10^-4mol/m2/min, activation energy E=29.085 k J/mol/K,R the gas constant, T the absolute temperature.