SU1726389A1 - Method for desiliconizing of water - Google Patents

Abstract

The invention relates to applied electrochemistry, in particular, to electro-membrane technology, and can be used to obtain deionized water from natural waters and industrial solutions with a high initial content of silicon compounds. The aim of the invention is to increase the degree of purification of water from silicon compounds and eliminate the consumption of chemical reagents. The process of water desaccination by electrodialysis is carried out in an electrodialyzer with alternating bipolar and anion-exchange membranes forming alkaline and acid chambers at a current density of 0.05-0.5 A / dm2, and the water being treated is fed into alkaline chambers. 2 tab., 1 Il.

Description

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The invention relates to applied electrochemistry, in particular to electro-membrane technology, and can be used to obtain deionized water from natural waters and industrial solutions with a high initial content of silicon compounds.

The closest to the claimed technical essence is the electrodialysis method of removing silicates, in which the desiliconization is carried out in an electrodialysis apparatus with alternating anion-exchange and cation-exchange-. mi membranes. To convert the silicates into anionic form, the treated water is pre-alkalized to pH values of 9.5-11.5 with either soluble hydroxide or soda.

The disadvantage of the method is the use of reagents to maintain the required pH of the water. In addition, the method does not allow achieving a high degree of water purification from silicon compounds.

The aim of the invention is to increase the degree of purification of water from silicon compounds and eliminate the consumption of chemical reagents.

This goal is achieved by the fact that in the process of desilicating water by electrodialysis in an electrodialyzer with alternating ion-exchange membranes, some of which are anion-exchange, bipolar membranes facing the anode with the formation of acid and alkaline chambers are used as other membranes

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alkaline chambers and the process is carried out at a current density of 0.05-0.5 A / dm2.

The drawing shows an electrodialysis circuit used to remove silicates consisting of alternating anion-exchange 1 and bipolar 2 membranes forming alkaline 3, acid 4, electrode 5, 6 chambers. The cathode 7 is made of stainless steel X18H10T, as the anode 8 using an oxide ruthenium-titanium electrode. The bipolar membranes 2 face the cathode 7 with an anionic side.

The purified water is fed into the alkaline chambers 3 electrodialyzer. Under the action of an external constant electric field in the bipolar membrane 2 at the interface between the anion exchangers and cation exchangers, water molecules dissociate. Hydroxyl ions are transferred to the alkaline chamber 3 and the pH of the treated water is shifted to values between 9.5 and 11.0, while the silicates are converted to the anionic form H2503, U3S, and under the action of an electric field with hydroxyl ions migrate through the anion-exchange membrane 1 acid chamber 4. Hydrogen protons are transferred from bipolar membrane 2 to acid chamber 4, neutralize the hydroxyl ions that are present here, and their excess prevents the undesirable process of precipitation of silicic acid in these chambers.

Example. For the desilification of water, two geometrically identical electrodialyzers were collected. In the apparatus according to the proposed method, the anionic membranes MA-41I1 and bipolar membranes MB-3 2 were used. In the apparatus assembled by the prototype, the cation-exchange membrane MK-40 was used instead of the bipolar membranes. The initial solution containing 15 mg / l of sodium silicate was supplied in a continuous flow mode to alkaline 3 (for the prototype to desalting) chambers of the apparatus with the same volumetric rate of 0.6 l / h. The solution supplied to the apparatus of the prototype, pre-alkalinized to a pH of 10.5. Acidic 4 (concentrating in the prototype) and electrode chambers 5, 6 of the devices under study were washed with distilled water at the same volumetric rate. The processes of electrodialysis purification were carried out in galvanostatic mode. At each fixed current, a steady state was achieved, in which the pH and concentration of silicate ions, measured at a 30-minute interval, differed by no more than 3%.

The test results are given in

Table 1.

As can be seen from the table. 1, with the same current density in the proposed method with bipolar membranes, it is possible to reduce the silicate concentration by half per pass, while in the known method the decrease in the silicate concentration does not exceed 15%. In this case, the energy consumption in the proposed method is several times

less than in the famous. Thus, the use of an electrodialyzer with bipolar membranes makes it possible to effectively descumber water without the use of chemical reagents.

In tab. 2 shows the test results of the proposed electrodialyzer to determine the optimal current density.

As can be seen from the table. 2, when the current density is less than 0.05 A / dm2, the degree of water purification from

silicates are small; at current densities above 0.5 A / dm, the specific energy consumption increases significantly. Therefore, for carrying out the process of desiliconization, the optimal range of current density is chosen.

from 0.05 A / dm2 to 0.5 A / dm2, which makes it possible to reduce the concentration of sodium silicate by a factor of 2–5 with low energy consumption. Thus, presented in table. 1 and 2, experimental data indicate that the task has been achieved by carrying out the process of desilication in an electrodialyzer with alternating bipolar and anion-exchange membranes at a current density of 0.05-0.5 A / dm2.

Ph o r u m a l i z o b r e i n A method of water desiliconization by electrodialysis in an electrodialyzer with alternating ion exchange membranes, some

of which are anion-exchange, characterized in that, in order to increase the degree of desintering and eliminate the consumption of chemical reagents, bipolar membranes are used as other membranes,

facing the anode with the anion-exchange side with the formation of acid and alkaline chambers in the electrodialyzer, with the supply of source water into the alkaline chambers and the process is carried out at a current density of 0.05-0.5

A / dm2

Comparative characteristics of the known and proposed methods of desilicating water with an initial concentration of sodium silicate 15 mg / l

The dependence of the degree of purification and energy consumption from current density in the proposed method

Table 1

table 2

Claims (1)

Claim A method of desalting water by electrodialysis in an electrodialyzer with alternating ion-exchange membranes, one of which is anion-exchange, characterized in that, in order to increase the degree of desiliconization and eliminate the consumption of chemicals, bipolar membranes are used as other membranes, facing the anode with the formation of acid and alkaline chambers in the electrodialyzer, with the supply of source water to the alkaline chambers and the process is conducted at a current density of 0.05-0.5 A / dm ² . b Table 1 Comparative characteristics of the known and proposed methods of desiliconization of water with an initial concentration of sodium silicate 15 mg / l Apparatus Current density, A / dm ² Alkaline chamber Acid chamber Specific energy consumption W · h / l · dm ² pH Degree about h and with t Svyh / Syskh, mg / l pH With bipolar 0.04 10.0 0.57 4.7 0.84 my membranes 0.06 10,2 0.48 4.8 1.40 (offer- 0.08 10,2 0.43 3.4 2.92 th way) The camera Camera con With monopolar- ' salting centering them membrane NII by us (known ny way) 0.04 6.4 0.80 6.5 7.32 0.06 6.3 0.80 7.3 10.80 0.08 6.6 0.74 6.0. 19.24 table 2 The dependence of the degree of purification and energy consumption on the current density in the proposed method Current density A / dm The degree of purification, mg / l Specific energy consumption, W * h / l * dm ² 0.004 0.87 0.05 0.02 0.73 0.18 0,03 0.69 1.10 0.05 0.63 1,50 0.06 0.48 2.12 0.08 0.43 3.48 0.15 0.36 19.50 0.2 0.33 36.40 0.3 0.31 70.50 0.4 0.27 110,10 0.5 0.25 158.30 0.6 0.23 257.80 0.7 0.23 550.30 oily ^ yenase.