SU1597344A1 - Electrolyzer for treating aqueous solutions - Google Patents

Abstract

The invention relates to the field of applied electrochemistry, in particular to electrolyzers for treating aqueous solutions, and can be used in electroplating where solutions with a high content of hydrogen ions or hydroxide are used. In order to increase the efficiency of the cell electrodes are disposed coaxially and are designed so that the areas of the outer and inner electrodes are coupled relation March ¹⁰ ≤S _Ext. / S _ext. * 9810 ⁷ . 2 Tablets, 1 Il.

Description

The invention relates to d) cyclic electrochemistry, in particular, electrolyzers for treating aqueous solutions, and can be used in electroplating and other areas where solutions with a high content of hydrogen ions or hydroxyl are used. .

The purpose of the invention is to increase the efficiency of the electrolyzer by allowing the solution pH to be adjusted without using a diaphragm.

The drawing shows the cell, General view, the section.

The device comprises a housing 1 (chamber) of the electrolyzer, a cover 2, an external electrode 3, an internal electrode, input terminals 5 of the electrodes, an inlet 6, an outlet 7.

The device works as follows.

An aqueous solution (liquid) through the inlet pipe 6 enters the cell 1 of the electrolyzer at a rate of not more than 0.1 l / min. As soon as the cell of the electrolyzer is filled to half, the voltage is applied to the input terminals 5 of the electrodes. At the same time, the process of electrolysis begins, which can be judged by gassing on the outer 3 and inner k electrodes rigidly fixed on the lid 2 of the electrolyzer. Waste fluid through the pipe 7 flows to the consumer.

According to Farad’s law, the same amount of electricity is consumed when a reaction takes place both on the inner and outer electrodes. Consequently, the material effect of electrode reactions must be the same. However, due to the large difference in the surfaces of the inner and outer electrodes, the rate of formation of reaction products per unit surface of the inner electrode (smaller in area) will be significant.

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This creates a gradient of concentrations of the reaction products of the internal electrode and facilitates their rapid movement from the internal to the external electrode. In addition, a high current density on the inner electrode causes local heating of the electrolyte and its subsequent convective movement from the center to the periphery of the electrolyzer (from the inner electrode to the outer one).

At the outer electrode, reactions will also proceed, but the rate of formation of their products per unit surface will be substantially less than at the inner electrode. As a consequence, the rate of withdrawal of the reaction products 20 from the surface of the electrode will be very small. The reaction products will accumulate in the surface irregularities of the external electrode, adsorb on it. In addition, the convective flow directed from the inner to the outer electrode pushes the solution enriched in the reaction products on the outer electrode to the surface of this electrode. The thickness of the solution layer adjacent to the surface of the external electrode and enriched by the products of the reaction occurring on it will not be greater than the thickness of the Prandtl layer, which is due to the hydrodynamics of the process. Thus, due to the concentration gradient and convection, the area of the electrolyte enriched with the reaction products on the inner electrode will extend up to the surface layer of liquid on the outer electrode.

When pumping through the electrolyzer of the initial solution at the exit

the device will get a solution enriched with hydrogen ions or hydroxyl. generated on the internal electrode. This is due to the fact that a solution enriched in reaction products on the inner electrode and occupying almost the entire volume of the electrolyzer will be in turbulent motion and easily removed, and the solution enriched in reaction products on the outer electrode will form a laminar layer that has an extremely low speed of movement. (practically immovable and remains near the surface and in the irregularities of the external electrode).

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Electrolyte samples were taken at different distances from the internal electrode, the pH and redox potential of these samples were measured. The diameter of the electrolyzer is 80 mm, the diameter of the external electrode is 75 mm, the diameter of the internal electrode is 0.5 mm. The ratio of the areas of the external and internal electrodes was 10. The polarity of the external electrode is +, the internal electrode is - -. The original solution contained Na / jS04 with a concentration of 0.2 g / l; pH 6.8; E ok 80ССТ, +200 mV, The results of the experiment are summarized in table. one.

According to the results of the experiment, almost the entire volume of the electrolyzer is occupied by a solution containing the reaction products going on the inner electrode (hydroxyl ions). The boundary of the electrolyte zones enriched in the reaction products flowing on the inner and outer electrodes lies in the immediate vicinity of the surface of the outer electrode, which is confirmed experimentally (experiment 8, Table 1), the pH of the solution drained from the electrolyzer was 11.24. This indicates that the reaction products flowing on the external electrode, while draining the solution, remained in irregularities and on the surface of this electrode.

Example. Made laboratory version of the device.

The case and the cover of the electrolyzer are made of plexiglass. The diameter of the electrolyzer is 8 cm, height 12 cm. The inner electrode is a platinum wire with a diameter of 1 mm and a length of 8 cm. It is located exactly in the center of the cell of the electrolyzer. The outer electrode is made in the form of a cylinder tightly adjacent to the walls of the cell of the electrolyzer. It is made of an oxide-ruthenium grid, its height is 1 O cm. The ratio of the areas of the external and internal electrodes is 10.

In addition, other electrodes were fabricated with an area ratio of 10; 100; 300; 1000; 5-10.

The tests were carried out using rectifiers VSA-4k, pH meter EV-7.

An aqueous solution of sodium sulfate is used as the working fluid. concentration of 0.2-1 g / l, as well as tap water.

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The pH of the initial solution of sulfate is 6.8, the redox potential is +200 mV, the temperature of the solution is 20 ° C,

The voltage at the terminals of the electrolyzer offered was V. The average current reached 0.8 A. An electric-JQ cell consisting of a chamber with electrons whose spaces were separated by an aphragm was also used to communicate with the proposed electrolyzer. The aqueous solution is fed into the zones of the main and auxiliary electrodes through the inlet nozzles, j, with 80-85% of the total fluid entering the electrolyzer being fed into the main electrode space. Processed in the space of the main electrode, the liquid through the outlet 20 nozzle enters the consumer. Fluid from the space of the auxiliary electrode is discharged into the sewer through the outlet. The voltage at the terminals of the electrolyzer, 25 taken as a known device, was 110 V.

The average current reached 3 A. Both electrolyzers had the same working volume of 0.5 l (for an electrolysis cell, this is the space of the main electrode

The tests carried out showed the advantage of the proposed electrolyzer. Test results are summarized.

in tab. 2

A further increase in the ratio of the areas of the external and internal electrodes may entail an increase in the cell of the electrolyzer to large sizes, which will make its manufacture impractical or impossible (Table 2). The pH values of the redox potential, which are slightly different from those of the untreated solution, show that the electrolyzer stops working due to clogging of the diaphragm (Table 2).

Thus, an opportunity is created 50 to obtain a liquid, characterized by a certain pH value, in the entire volume of the electrolyzer, which will make it possible to exclude the flow rate associated with its supply to the auxiliary space.

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electrode as in the case of a cell with a diaphragm. In addition, a reduction in the cost of electricity can be achieved by reducing the flow rate of the liquid, as well as by eliminating the loss of electricity on the diaphragm. Using the cell of the electrolyzer without a diaphragm can significantly increase the uptime. This is due to the fact that the diaphragm clogs with the by-products of electrolysis during operation and the duration of the operation of the electrolyzer in the JTOM case is an average of 30–0 O. The life of the electrolyzer of this design increases by 2–3 times and is determined only by electrodes (i.e., the rate of their destruction). .

Claims (1)

Invention Formula An electrolyzer for treating aqueous solutions, comprising a housing with coaxially mounted cylindrical electrodes placed therein, in order to increase the efficiency of the electrolyzer by allowing the solution pH to be adjusted without the use of a diaphragm, the electrodes are designed so that the area ratio of external sound. internal s. electrodes satisfies the condition j 40 c fsl: f un mcofv-s (V4raromu LA m j s c; YU fO tSEEC U-VCDLACDUr O LAO - T-fsJ CN f {V.jCDCJLAOOOOOO  rococo racvi r HNO- and -R- crirsICNl + + + + + + + + + imgch r cr COr- vDCJ-ir o GO r r GL -: f LA O D seseoooooch ooi CO h r- GL about un CM r r  04 CvJ CM fN t-, - I I I I I I I I t LA LALA CM CJ CM - (- .,., r-CDCnOOr r ooseoseoseooz cocococooooocooooo - -: 3-LACOf rar CM ME ChO CHO vO I O O CHO vO seoooosesaseoseo CDOOOOtpOOO GJ I X S about CSglXX ) yuzoshShchH OZtO j, -I | c. qu) 5gq 3 (U  YU U CE about X Q) QJ Sh 3 H I ct I x o 0) (u cd m j X - about LA about M LA SE about SE SE SPALG G LLCO lArv-s vOvOfMvQ DvO POCM CM + H- + + + + + + +  OL r , - ,,, p- LAOLA ОL CA iv {V CO r LA vO vO CD ooo u c; about SE about  r - t l -LACNl CM CM CM CM CM 1- I I t f I t I I 1  SE CO r r OSEOOSIOOOO SEZESSEESEAOOSZO . ( seseseseseseooose 1- fM fO - LTV I3 G - SHE SP