Experimental study of kyanite dissolution rates as a function of chemical affinity and solution composition

摘要: Abstract Kyanite steady state dissolution rates were measured in mixed flow reactors as a function of aqueous aluminum and silica concentration at pH 1.6 to 2.2 temperatures from 108 194°C. Aqueous these experiments ranged 2.8 × 10−7 ≤ [Sitotal] 1.9 10−4 mol/kg, 3.0 [Altotal] 4.1 10−5 respectively, corresponding chemical affinities ranging ∼40 ∼97 kJ/mol. Steady was stoichiometric within experimental uncertainty. Dissolution found vary linearly with aAl+3−1/2 aH+3/2, where ai designates the activity subscripted species. This behavior is consistent being controlled by destruction neutrally charged deficient precursor complex mineral surface. Because its dependence on aluminum, kyanite’s constant temperature/pH appear depend affinity overall reaction far equilibrium conditions. All rates, which obtained conditions contribution reverse negligible, are r=A A exp (−E /RT ) H + 3 Al +3 0.5 , r signifies kyanite rate normalized 1 cm2 surface, AA refers pre-exponential factor equal 2 mol/cm2/sec, EA an apparent activation energy 75 kJ/mol, R represents gas constant, T denotes absolute temperature.