An experimental study on dynamic coupling process of alkaline feldspar dissolution and secondary mineral precipitation

In order to clarify the dynamic process of feldspar dissolution-precipitation and explore the formation mechanism of secondary porosity, six batch reactor experiments were conducted at 200 degrees C and pH = 7 measured at room temperature. Temporal evolution of fluid chemistry was analyzed with an inductively coupled plasma optical emission spectrometer (ICP-OES). Solid reaction products were retrieved from six batch experiments terminated after 36, 180, 276, 415, 766 and 1008 h. Scanning electron microscopy (SEM) revealed dissolution features and significant secondary mineral adhered on the feldspar surface. The process of feldspar dissolution-precipitation proceeded slowly and full equilibrium was not achieved after 1008 h. Saturation indices suggested that the albite and K-feldspar dissolution occurred throughout the experiments. The average dissolution rates for albite and K-feldspar were 2.28 x 10(-10) and 8.51 x 10(-11) mol m(-2) s(-1), respectively. Based on the experimental data, the reaction process of alkaline feldspar was simulated and the secondary porosity had increased 0.3% after the experiment.