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向不含金属离子的硅酸体系中加入Fe3+离子,研究了体系胶凝时间、溶胶粒径、凝胶比表面积、官能团及热稳定性的变化.结果表明,加入Fe3+降低了体系pH值;初始pH≤2时,Fe3+起促凝作用,初始pH≥3时,Fe3+起缓凝作用.初始pH=2时,放置24 h溶胶粒径随Fe3+浓度增加而增大,凝胶比表面积逐渐增大,Fe3+浓度为0.03 mol/L时粒径为444 nm,比表面积为1500 m2/g;初始pH=3时,放置24 h溶胶粒径随Fe3+浓度增加呈先增大后减小的趋势,最大粒径达379 nm,而凝胶比表面积逐渐减小,Fe3+浓度为0.03 mol/L时为81 m2/g.Fe3+引起聚硅酸网络结构变形,导致凝胶部分吸收峰强度减弱和移位及凝胶结合水减少和晶化转变峰变弱.
Fe3 + ion was added into the silicic acid system without metal ions to study the change of gelation time, sol particle size, specific surface area, functional groups and thermal stability of the system. The results showed that the addition of Fe3 + When pH≤2, the effect of Fe3 + is procoagulant, and when the initial pH≥3, Fe3 + plays a retarding role.When the initial pH is 2, the particle size of sol increases with the increase of Fe3 + concentration and the specific surface area of gel increases gradually , The particle size is 444 nm and the specific surface area is 1500 m2 / g when the concentration of Fe3 + is 0.03 mol / L. When the initial pH is 3, the particle size of the sol first increases and then decreases with the increase of Fe3 + concentration, The particle size reaches 379 nm, and the specific surface area of the gel decreases gradually, which is 81 m2 / g when the concentration of Fe3 + is 0.03 mol / L.Fe3 + causes the network structure of polysilicic acid to deform, Gel-bound water decreases and the peak of crystallization transition becomes weaker.