RU2155639C1 - Method for electrochemical regeneration of anion-exchange resins - Google Patents

Abstract

FIELD: waste water treatment. SUBSTANCE: horizontal titanium electrodes connected to constant-current source are immersed into exhausted anionite slurry and regeneration is accomplished under voltage of 10-12 V. Electrodes are constructed in the form of titanium wire gauze, and anode is insulated with dielectric membrane or cloth. Process is carried out under static conditions. EFFECT: eliminated expenses on expensive regeneration reagents and reduced volume of eluates. 3 cl, 4 ex

Description

 The invention relates to a method for the electrochemical regeneration of anion exchange resins used for wastewater treatment from anions.

 A known method of regeneration of cation exchangers, in which cation exchange resins are subjected to DC treatment. Hydrogen ions are generated at the anode, which, moving towards the cathode, displace the cations remaining from the previous desalination. Thus, the regeneration of cation exchangers occurs (Verfahren und Vorrichtung zur Regeneration von lonenaustaushermateril: Application 3805813 Germany, MKI 4 01 J 49/00, B 01 J 19/12; Grunbeck Wasse raufbereitung GmbH. - NP 38058138. Declared 02.24.88. Published on 03.30.88. 89).

 Closest to the proposed invention is a method of electrochemical regeneration of anion exchangers depleted in the process of water purification from anions, in which the anion exchange resin is exposed to direct electric current (SU 833 292 A, C 02 F 1/42, 05/30/1981).

 The difference between the proposed method and the known one is that horizontal titanium electrodes connected to a direct current source are immersed in the anionite mass, and the optimal process voltage is 10-12 V.

 Additional differences are that the electrodes are made in the form of a grid of titanium wire, the anode is insulated with a dielectric membrane or fabric, the process is carried out in static conditions.

 The purpose of the invention is to reduce the amount of waste generated during the regeneration of anion exchange resins and the exclusion of the use of scarce expensive reagents.

 This goal is achieved by the fact that depleted in the cleaning process, the anion exchange resin is exposed to direct electric current. The mechanism of the process is as follows: in a constant electric field between two electrodes (anode and cathode) hydroxide ions are generated at the cathode, which are introduced into the anionite mass and cause the remaining in the anionite mass to be displaced after absorption of anions (for example, chloride ions or sulfate ions) in the direction of the anode, the displaced anions together with the hydrogen ions formed on the anode are collected in the anode space.

 The pH of the resulting filtrate depends on the voltage applied to the electrodes. The higher the voltage, the lower the pH of the solution. But the electrochemical regeneration of anion exchangers must be carried out at voltages of 10-12 V. This voltage value is optimal, since at process voltages below 10 V the process efficiency is small, and at voltages above 12 V, resin degradation occurs in the anode space due to the liberated atomic oxygen. The intensity of the reaction of the evolution of atomic oxygen depends on the voltage supplied to the electrodes.

 Thus, the proposed method of regeneration has the following advantages: eliminates the use of reagents for the regeneration of anion exchange resins, reduces the amount of formed eluates.

 The foregoing is illustrated by the following examples.

Example 1. Regeneration of anion exchange resin AN-31. Anion exchange resin is saturated with chloride ions. U = 10 V, I = 14.3 mA. The distance between the electrodes is 45 - 50 mm. The feed rate of water into the interelectrode space is 0.36 dm ³ / h. The position of the electrodes is horizontal. The electrode material is a titanium mesh with a cell side of 1-2 mm. The duration of the process is 6 hours. Regeneration was carried out in a static mode. The regeneration efficiency of 60.55%.

Example 2. Regeneration of the AN-31. Anion exchange resin is saturated with sulfate ions. U = 10 V, 1 = 14.3 mA. The feed rate of water into the interelectrode space is 0.36 dm ³ / h. The position of the electrodes is horizontal. The duration of the process is 5.5 hours. The regeneration efficiency is 38.71%.

 Example 3. Regeneration of anion exchange resin AB-17-8. Anion exchange resin is saturated with sulfate ions. U = 10 V, I = 0.12 A. Regeneration was carried out under static conditions. The distance between the electrodes, the feed rate of water into the interelectrode space and the material of the electrodes as in example 1. The position of the electrodes 4 is horizontal. The duration of the process is 6 hours. The regeneration efficiency is 28.5%.

 Example 4. Regeneration of anion exchange resin AB-17-8. Anion exchange resin is saturated with chloride ions. U = 10 V, I = 0.12 A. Regeneration was carried out under static conditions. The distance between the electrodes and the material of the electrodes as in example 1. The position of the electrodes is vertical. The duration of the process is 6 hours. The regeneration efficiency is 11.53%.

 In all four examples, a perforated dielectric membrane is adjacent to the anode in order to minimize oxidation of the anion exchange resin, which is an organic polymer, atomic oxygen released in the anode space. The process must be carried out under static conditions in order to minimize the consumption of water for the regeneration of anion exchangers, i.e. reduce the number of eluates.

Claims (3)

 1. The method of electrochemical regeneration of anion-exchange resins depleted in the process of water purification from anions, characterized in that horizontal titanium electrodes immersed in an anionite mass connected to a direct current source with an optimal process voltage of 10-12 V.  2. The method according to claim 1, characterized in that the electrodes are in the form of a grid of titanium wire.  3. The method according to claims 1 and 2, characterized in that the process is carried out in static conditions.