CZ348192A3 - Process for preparing ferrates(vi) by electrochemical way - Google Patents

Abstract

Anodic oxidation of iron in alkaline solutions, based on the superimposing of alternating components of electric current with an amplitude of current density in a range of 2.1 to 2.5 times the current density of the direct components of the electric current with a frequency of 1 to 30 Hz to direct current. The alternating component prevents gradual passivation of the anode during electrolysis.

Description

BACKGROUND OF THE INVENTION

Iron (VI) compounds are promising substances which can replace, for example, permanganates in various areas of the chemical industry.

The most preferred methods for producing ferrates include the electrochemical oxidation of iron and cast iron in alkali hydroxide solutions. Usually a direct current of suitable anodic current density is used for this purpose. A disadvantage appears to be the fact that the anode surface is passivated during electrolysis and the current yields in this case decrease significantly with time.

then

The integral current yield fpetkj is of course very low.

As found by G. Grube and H. Gmelin (Zeitschrift fur Electrochemistry 7, 153 (1920)), the passivation of the anode surface can be slowed and the current yield can be significantly increased by using an AC component with an appropriate ratio of the AC current amplitude to DC current density. This prevents the current yields from decreasing with time. However, the optimum ratio varied [for example] with the temperature of the electrolyte, e.g.

A value of 2.5 and at a temperature of 3 ° C, this ratio was 1 ₍ 5, making it considerably more difficult to use this method to prevent anode passivation during ferrate production. The effect of frequency was not considered important and therefore not even observed. at a constant frequency of the superposed alternating current component of 50 Hz In the current applications, due to the current demand for iron oxidation from the metal state to the sixth oxidation stage, there was a considerable loss of electric charge or current, respectively.

SUMMARY OF THE INVENTION

These drawbacks are overcome by the method of electrochemical production of ferrates according to the invention using alternating current components superimposed on a direct current component. It is an object of the invention that the frequency of the AC superposed component of the electric current is in the range of 1.0 to 30.0 Hz at a ratio of the amplitude of the AC current density to the DC current density in the range of 2.1 to 2.5.

The advantage of the method of electrochemical production of ferrates according to the invention is that when the device operates in this mode, the optimum AC frequency is not temperature dependent, therefore the device does not need to be thermostatized and also (the power source can be designed for one AC current amplitude ratio). components of the electric current to the current density of the DC component of the electric current and one frequency of the AC component, thereby reducing the investment costs of this technology and its energy consumption.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

A 14 mol / dm @ 2 NaOH solution was poured into a cathode-iron anode cell with an unfilled polyvinyl chloride diaphragm.

The anode was cathodically activated for 30 minutes. Totorn at a DC current density of 20 mA / cm. electrolysis was initiated. At electrolyte temperature

An anode current density of 16.7 mA / cm and an AC component amplitude of 35 mA / cm was used at 20 ° C. The ratio of the amplitude of the AC current density to the DC current density was 2 ₍ 1 at AC frequency)

After 180 minutes of electrolysis, the duration of the electrolysis was removed and the anolyte was determined and titrated to 192 mg, corresponding to sodium ferrate, which

20.2%.

AND.

Example 2

The procedure was the same as that of Example 1. except that the current density amplitude of the AC component 'Ti' was 41.75 mA / cmTa and the ratio of the current density amplitude of the AC component to the current density of the DC component was value of 2.5. Under these conditions, a current yield of 23.5% was achieved.

Example 3

The procedure was the same as in Example 1, with the difference in the frequency of the superposed alternating component, which in this case was 30 Hz. Under these conditions a current yield of 22.6% was achieved.

Example 4

The procedure was the same as in Example 1. with the difference in the frequency of the superimposed AC component, which in this case was 30 Hz, and in the amplitude of the AC current density, which was 41.75 mA / cm ² . The ratio of the amplitude of the AC current density to the DC current density was 2.5. Under these conditions, a current yield of 25% was achieved.

Example 5

The procedure was the same as in Example 1, with the difference in the AC component frequency, which in this case was 5 Hz, and the AC current amplitude, which was 38.4 mA / cm. The ratio of the amplitude of the AC current density to the DC current density was 2.3. Under these conditions, a current yield of 32.1% was achieved.

Industrial applicability

The process of electrochemical production of ferrates according to the invention can be used for the production of substances used for disinfection and chemical treatment of drinking and service water or for the realization of some types of chemical syntheses as oxidizing and condensing agent in all areas of chemical and pharmaceutical industry.

Claims (1)

PATENTOVÉ Claims A method for the electrochemical production of ferrates using an AC component superposed on a DC component, characterized in that the frequency of the AC superposed component is in the range of 1.0 to 30.0 Hz, wherein the ratio of the amplitude current density of the AC component is the current density of the direct current component is in the range of 2.1 to 2.5.