The dissolution kinetics of feldspars at 25°C and 1 atm CO2 partial pressure

摘要: The dissolution kinetics of 5% by weight suspensions two potassium feldspars and six plagioclases were studied for 400–1200 hr at 1 atm PCO2 less than 37 μm particles had surface areas ranging from 0.83 to 1.84 m2/g. At frequent intervals, the pH stirred measured in reaction cell as solutions sampled. filtered aqueous samples acidified then analyzed Si, Al, K, Na, Ca, Mg, Fe. The following sequence events recognized artificial weathering all feldspars: 1. (1) an initial ion exchange stage lasting approximately l min during which cations replaced hydrogen ions bulk solution, 2. (2) up 4 day non-parabolic characterized very rapid release silicic acid into solution, 3. (3) a diffusion-controlled parabolic 19 days, and 4. (4) steady-state slow acid. All rate constants evaluated about 5. 5. calculated range 3.4 × 10−14 9.3 10−13 mole/cm2/sec1/2, linear 3.2 10−17 2.5 10−15 mole/cm2/sec, apparent diffusion coefficients 10−22 5 10−21 cm2/sec. The composition layer appears have 1:1 Si: Al molecular ratio, whereas contrast, appear 2:1 ratio.