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在较广p~H范围内研究了1—1价盐对硅酸聚合速度的影响。实验证明:在硅酸聚合的碱性机制范围内,多硅酸表面带负电荷,此电荷阻碍多硅酸聚合形成凝胶。当有外加盐存在时,多硅酸由于吸附加入的阳离子而中和其表面电荷,使硅酸凝胶形成的速度增加。碱金属离子促凝作用的次序为:K~+>Na~+>Li~+。这种作用随溶液P~H值减小而降低,当溶液到达硅酸聚合的酸性机制范围时,多硅酸表面带正电荷,外加盐的阳离子阻碍多硅酸聚合形成凝胶。理论计算的结果与实验事实相符。外加盐的阴离子在酸性机制范围内具有促凝作用,其促凝次序为IO_3~->BrO_3~->NO_3~-;而Cl~-、Br~-、I~-没有明显的差别。这种作用随溶液酸度降低而减小,当达到微酸性至微碱性范围时,阴离子的作用不明显。
The effect of 1-1 salt on the polymerization rate of silicic acid was studied in a wide range of p ~ H. Experiments show that: within the framework of the basic mechanism of silicic acid polymerization, the surface of polysilicic acid is negatively charged, and the charge hinders the polymerization of polysilicic acid to form a gel. When an additional salt is present, polysilicic acid neutralizes its surface charge due to the adsorption of added cations, increasing the rate of silicic acid gel formation. The order of procoagulant of alkali metal ions is: K ~ +> Na ~ +> Li ~ +. This effect decreases with the decrease of the P ~ H value of the solution. When the solution reaches the acidic mechanism of silicic acid polymerization, the surface of the polysilicic acid is positively charged. The addition of salt cations impedes the polymerization of polysilicic acid to form a gel. The result of theoretical calculation is consistent with the experimental fact. The anions with added salt have procoagulant effect within the scope of the acid mechanism, and the procoagulant order is IO_3 ~ -> BrO_3 ~ -> NO_3 ~ -, while Cl ~ -, Br ~ - and I ~ have no obvious difference. This effect decreases with decreasing acidity of the solution, and when the acidity to slightly alkaline range is reached, the effect of anions is not conspicuous.