Method for preparing high-purity silicic acid

The invention relates to a method for preparing high-purity silicic acid. The method comprises the following steps of (1) water glass dilution, wherein the content of silicon dioxide contained in raw material water glass is 15%-35%, the content of silicon dioxide contained in a solution obtained after the raw material water glass is diluted by using water is 2%-7%; (2) water glass purification: filtering the solution obtained after dilution from the step (1) by adopting a bag filter; (3) cation resin exchange: carrying out the cation resin exchange to obtain silicic acid; (4) silicic acid acidification: acidifying the silicic acid obtained from the step (3) by adding acid; (5) resin exchange: carrying out the resin exchange to obtain the high-purity silicic acid. The high-purity silicic acid prepared through the method disclosed by the invention has the characteristics of low metal ion content, the process is easy to operate and continuously produce on large scale and low in raw material requirement, and the production cost of an enterprise is greatly reduced.