RU2381991C1 - Method of producing silica gel - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: sodium silicate solution is treated outside an electrolysis cell with an anodic acid aqueous solution flowing from the anode chamber of the electrolysis cell at pH 3-4. The anodic acid solution is obtained through electrolysis of tap water in flowing mode. ^ EFFECT: invention increases purity of silica gel by avoiding contamination with sodium sulphate and reduces power consumption on production. ^ 1 ex

Description

The invention relates to the field of colloid chemistry, and more specifically to the synthesis of silicic acid gels from alkali metal silicates, in particular from sodium silicate as a relatively cheap and affordable raw material.

A known method of producing a gel of silicic acid from a solution of sodium silicate by treating it with a solution of sulfuric acid. The resulting product is washed from sodium sulfate with aqueous ammonia at t = 200 ° C. The resulting gel contains only 3% SiO ₂ , by evaporation its content is adjusted to 20-25% (1).

The disadvantage of this method is the use of elevated temperature and the use of a valuable chemical reagent - sulfuric acid. In addition, the resulting product - sodium sulfate does not find wide practical application, is a waste.

There is also a method closest to the present invention, which consists in obtaining a gel of silicic acid in a 2-chamber electrolyzer with a cation exchange membrane, in the cathode chamber of which contains a 0.1% NaOH solution, and a 4% solution of sodium silicate is fed into the anode chamber (2) .

The disadvantage of this method is that the resulting silicic acid polymerizes directly on the surface or near the membrane, which leads to a sharp increase in the resistance of the system and an increase in energy consumption.

The objective of the present invention is to ensure the purity of the final product and reduce energy consumption.

The efficiency of the process is achieved by using flow electrolysis.

The technical result is achieved by the fact that the process is carried out outside the electrolyzer by mixing silicic acid sodium with an acidified solution of drinking water formed in the anode chamber during the electrolysis of drinking water, i.e. due to the transfer of cations from water to the cathode chamber and acidification of water in the anode chamber.

The essence of the method of producing silicic acid gel from alkali metal silicates, which includes electrochemical treatment of water, is that the electrolysis of tap water is carried out in a flow mode, and the processing of sodium silicate solution is carried out outside the cell by an anodic acid aqueous solution flowing from the anode chamber of the cell, at pH 3-4.

As a result of the treatment, silicic acid precipitates and the basic ionic composition of the starting water is restored.

An anodic acidic aqueous solution is prepared as follows: running drinking water is discharged through a 2-chamber electrolyzer with a cation exchange membrane at a temperature of 25 ° C, anodic current density of 0.01 A / cm ² ; electrolysis is carried out in flow mode, water is divided into two streams and passes through the anode and cathode chambers; The pH of the water during electrolysis is maintained at a level of 3-4 by changing the volume of water flowing through the anode chamber.

An example implementation of the method is as follows. Electrolysis is carried out in a flow mode using a 2-chamber electrolyzer with a cation exchange membrane. Moreover, ordinary tap water is subjected to electrolysis. Platinum titanium was used as the anode material, and copper as the cathode material.

A solution of sodium silicate in a ratio of 1:10 was treated with acidified water flowing out of the anode chamber already outside the cell. The resulting silica gel is ready for use.

In this case, depending on the pH of the medium, a silica gel of various percent composition is formed. The best option is the electrolysis of drinking water at pH 3-4. At lower pH values of the anode liquid, excessive power consumption is observed.

Example 1. The electrolysis of tap water was carried out in a 2-chamber electrolyzer with a cation exchange membrane in a flow mode at a flow rate of 1 ml / s. Sodium silicate in a ratio of 1:10 was treated with water flowing from the anode chamber to obtain a gel. In this case, a gel of silicic acid is formed, and the basic ionic composition of the water is restored.

At a pH of less than 3-4, it is undesirable to carry out electrolysis in connection with an increase in the voltage on the electrolyzer and additional energy consumption.

Water electrolysis conditions.

pH 1,0 1,5 2.0 2.5 3.0 3,5 4.0 4,5 5,0 U in 28 25 twenty eighteen fifteen fifteen fifteen fifteen fifteen

The table shows the dependence of energy consumption and voltage on the pH of the medium.

In the known method, silicic acid, deposited on the surface of the membrane, shields the surface, which inhibits the further process and requires large energy costs. In the proposed method, silicic acid does not precipitate, because the deposition process goes beyond the limits of the cell in a separate chamber. The resulting silica gel is not contaminated with a chemical compound such as Na ₂ SO ₄ , from which it must be completely cleaned for use in the food industry. The gel obtained by this method contains only water that meets the MPC standards.

The content of sulfate ions and other ions present in tap water meets the MPC standards, which allows to obtain a gel of high purity, and the proposed method is economical.

The gel obtained by this method can be used to process wine materials, clarify and stabilize juices, as well as to eliminate metal cash registers (3).

Literature

1. Japanese patent No. 41-10237, 1966.

2. Ayler R.K. Chemistry of silica. Per. from English - M .: World. Part 2, 1982, pp. 449-453.

3. Patent of Russia No. 2272833, 03/27/2006, Khizrieva I.Kh., Kharlamova T.A., Aliev Z.M. "The method of clarification and stabilization of wine materials."

Claims (1)

A method of producing a silicic acid gel from alkali metal silicates, including electrochemical treatment of water, characterized in that the electrolysis of tap water is carried out in a flow mode, and the treatment of a sodium silicate solution is carried out outside the cell with an anodic acid aqueous solution flowing from the anode chamber of the cell at pH 3 -four.