EDTA对硅垢形成过程的影响机理

Effect of EDTA on the Silica Scale Formation and Its Mechanisms

为揭示EDTA对硅酸聚合沉淀过程的影响机理,本文结合浊度分析法和粒度分析法研究了有无添加EDTA的不同浓度硅酸钠溶液的浊度变化及粒径变化。浊度分析结果发现,硅酸钠浓度为400 mg·L^(-1)和800 mg·L^(-1)时,溶液的浊度基本相同,在3 NTU左右。而硅酸钠浓度大于800 mg·L^(-1)时,溶液浊度随浓度的增大而增大。在同样的硅酸钠溶液中添加一定浓度的EDTA时,混合溶液的浊度大于相应的硅酸钠溶液的浊度,且添加的EDTA浓度越大浊度越大,说明EDTA促进硅酸的聚合反应。粒度分析结果发现,添加EDTA的混合溶液中所形成的硅胶颗粒的粒径比相应的硅酸钠溶液的粒径大,且随EDTA浓度的增加而增大,说明EDTA促进硅胶颗粒的生长。根据FT-IR分析结果推测EDTA对硅酸聚合沉淀的促进机理如下:EDTA分子内所含的羰基上的氧原子或胺基上的氮原子通过氢键与溶液中已形成的硅胶体表面的Si-OH官能团相互作用,通过P-P反应把小的硅胶颗粒集聚到一起,促进硅胶颗粒的生长,从而促进硅酸的聚合沉淀反应。

To evaluate the effect of EDTA on the polymerization of silicon acid, the turbidity analysis method and particle size analysis method were used to investigate the changes of turbidity and particle size in the different concentration of sodium silicate solutions with presence and absence of EDTA. Turbidity analysis found that the turbidity of sodium silicate solution with concentration 400 mg · L^-1 and 800 mg · L^-1 were around 3 NTU. Moreover, the turbidity increased with the increase of the concentration of sodium silicate solution when the concentration was greater than 800 mg · L^-1. The turbidity of sodium silicate solution with certain amount of EDTA was larger than that the corresponding pure sodium silicate solution, and increased with the increase of the concentration of EDTA, indicating that EDTA accelerate the polymerization reaction of silicon acid. Particle size analysis results show that the size of silica gel particles formed in mixture solution with sodium silicate and EDTA was larger than that formed in the corresponding pure sodium silicate solution, suggesting the EDTA accelerate the growth of silica gel particles. Based on the FT-IR analysis results, the accelerating mechanism of EDTA for silicon acid polymerization reaction were extrapolated as follows： the oxygen atoms in the carbonyl groups and nitrogen atom in the amino groups interacted with hydroxyl groups （Si-OH） on the surface of silica gel particles through hydrogen bond, and gathered together the small silica particles by P-P reaction to accelerate the growth of silica particles, thereby accelerate the polymerization of silicon acid to form silica.