Diffusion property of dissolved silica in rock pore water

为研究溶解硅的扩散系数与溶解硅化学形态的关系，以砂岩和流纹岩为材料，在pH值分别为6、9.5和11的条件下进行了扩散实验。测定了K^+、Cl^-和溶解态Si的扩散系数。随着pH值的升高，溶解态Si的有效扩散系数增大，并逐渐接近K^+和Cl^-的有效扩散系数。溶解的Si的扩散的pH依赖性的一个可能的原因可能是，随着pH增加，溶解的Si变得较少吸附在带负电荷的孔壁表面上。

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.