Diffusion property of dissolved silica in rock pore water

为了研究溶解Si的扩散系数与溶解Si的化学形态之间的关系，分别在pH为6、9.5和11的条件下，用砂岩和流纹岩进行了扩散实验。测定了K^+和Cl^-的扩散系数以及溶解Si的扩散系数。随着pH的增大，溶解Si的有效扩散系数增大，接近于K^+和Cl^-的有效扩散系数。溶解硅的扩散依赖于pH值的一个可能的原因可能是，随着pH值的增加，溶解硅在带负电荷的孔壁面上的吸附减少。

To study the relationship between the diffusion coefficient of dissolved Si and the chemical form of dissolved Si, through diffusion experiments were conducted at pH 6, 9.5 and 11 using sandstone and rhyolite. The diffusion coefficients of K^+ and Cl^- as well as that of dissolved Si were determined. As pH increased, the effective diffusion coefficient of dissolved Si increased and approached to those of K^+ and Cl^-. One possible reason for the pH dependence of the diffusion of dissolved Si might be that as pH increases dissolved Si become less sorbed on negatively charged pore wall surfaces.