Kley M, Kempter A, Boyko V, Huber K
Physical Chemistry, University of Paderborn , Warburger Str. 100, 33098 Paderborn, Germany.
Langmuir. 2014 Oct 28;30(42):12664-74. doi: 10.1021/la502730y. Epub 2014 Oct 16.
Silica polymerization in a supersaturated aqueous solution of sodium silicate is a fundamental mineralization process with broad relevance for technical applications as well as for biological processes. To contribute to a better understanding of the mechanism underlying the polymerization of sodium silicate under ambient conditions, a combined multiangle static and dynamic light scattering study on the evolution of particle mass and size is applied for the first time in a time-resolving manner. The light scattering experiments are complemented by a time-resolved analysis of the decay of the concentration of monomeric silicate by means of the silicomolybdate method. Particle formation was investigated at a variable concentration of silicate at pH 7 and 8. The joint experiments revealed a loss of monomers, which is parallel to the formation of compact, spherical particles growing by a monomer-addition process. An increase in the silicate content of up to 750 ppm increased the extent of nucleation and at the same time decreased the lag time observed between the start of the reaction and the actual onset of the growth of particles. Once the silica content is considerably larger than 1000 ppm, the formation of particles is succeeded by particle-particle agglomeration leading to larger fractal-like particles. By the time agglomeration becomes noticeable with light scattering, the monomer concentration has already reached its equilibrium value. An increase in the pH to 8 again revealed particle formation via a monomer-addition process. However, the extent of nucleation was increased and particle-particle agglomeration was inhibited even at an initial silica content of 2000 ppm.
硅酸钠过饱和水溶液中的二氧化硅聚合是一个基本的矿化过程，在技术应用以及生物过程中都具有广泛的相关性。为了有助于更好地理解环境条件下硅酸钠聚合的潜在机制，首次以时间分辨的方式对颗粒质量和尺寸的演变进行了多角度静态和动态光散射联合研究。通过硅钼酸盐法对单体硅酸盐浓度衰减的时间分辨分析对光散射实验进行了补充。在pH值为7和8的可变硅酸盐浓度下研究了颗粒形成。联合实验揭示了单体的损失，这与通过单体添加过程生长的致密球形颗粒的形成平行。硅酸盐含量增加至750 ppm会增加成核程度，同时减少反应开始与颗粒实际生长开始之间观察到的滞后时间。一旦二氧化硅含量显著大于1000 ppm，颗粒形成之后会发生颗粒-颗粒团聚，导致形成更大的类分形颗粒。当通过光散射可明显观察到团聚时，单体浓度已经达到其平衡值。将pH值提高到8再次揭示了通过单体添加过程形成颗粒。然而，即使在初始二氧化硅含量为2000 ppm时，成核程度也会增加，并且颗粒-颗粒团聚受到抑制。
