Effect of inorganic salt impurities on seeded precipitation of silica hydrate from sodium silicate solution

无机盐杂质对硅酸钠溶液晶种分解析出二氧化硅水合物的影响

To clarify the precipitation of silica hydrate from the real desilication solutions of aluminosilicate solid wastes by adding seeds and improve integrated waste utilization,the seeded precipitation was studied using synthesized sodium silicate solution containing different inorganic salt impurities.The results show that sodium chloride,sodium sulfate,sodium carbonate,or calcium chloride can change the siloxy group structure.The number of high-polymeric siloxy groups decreases with increasing sodium chloride or sodium sulfate concentration,which is detrimental to seeded precipitation.Calcium chloride favors the polymerization of silicate ions,and even the chain groups precipitate with the precipitation of high-polymeric sheet and cage-like siloxy groups.The introduced sodium cations in sodium carbonate render a more open network structure of high-polymeric siloxy groups,although the carbonate ions favor the polymerization of siloxy groups.No matter how the four impurities affect the siloxy group structure,the precipitates are always amorphous opal-A silica hydrate.

为明确真实铝硅酸盐固体废物脱硅液通过添加晶种析出水合二氧化硅的情况和提高固废综合利用率,利用含有不同无机盐杂质的合成硅酸钠溶液进行晶种分解研究。结果表明:氯化钠、硫酸钠、碳酸钠或氯化钙能改变硅氧基团的结构。高聚合态硅氧基团数量随氯化钠或硫酸钠浓度的增加而减少,对晶种分解不利。氯化钙有利于硅酸盐离子聚合,链状硅氧基团甚至会伴随着高聚合态层状和网状基团的析出而析出。碳酸钠中碳酸根离子也有利于硅氧基团聚合,但引入的钠阳离子使高聚合态硅氧基团网状结构更加开放。不管这四种杂质如何影响溶液中硅氧基团结构,析出产物均为无定形蛋白石-A型二氧化硅水合物。