SU1604863A1 - Method of producing ferrate solutions - Google Patents

Abstract

This invention relates to methods for producing solutions of iron compounds that are oxidizing agents, and allows increasing the specific content of oxidant in solution by using anodic dissolution of iron in sodium hydroxide solution with a concentration of 1-10 mol in a known method for producing solutions of ferrite. l, current density of 0.6-17.5 A / cm ² . Moreover, the anode is subjected to pretreatment with methane at 150-200 ° C. 2 tab.

Description

The invention relates to methods of preparation, solutions of sodium ferrates of the formula Na2Fe04, which are oxidizing agents that can be used as bleaching agents for wastewater treatment, in organic synthesis as selective oxidizing agents, and the like.

The aim of the invention is to increase the concentration of ferrates. in solution.

Distinctive features of the proposed method are the use of NaOH solutions with a concentration of 1-10 mol / L, density, current 0.6–17.5 A / cm, and an anode activated in MeTajta current at 150–200 ° C.

When using solutions of NaOH with a concentration different from the specified range, the goal is not achieved. With NaOH i 1 mol / l, it is impossible even to obtain solutions.

containing about 4.0 g-SQR oxidizer per mole of iron. In the case of NaOH,.

 -10 mol / l. It is possible to synthesize only solutions in which the content of the oxidizing agent does not exceed that specified in the prototype, 3.97 g-eq of oxidizing agent per mole of iron (K-3.66-3.97). The value of K is numerically equal to the concentration of sodium ferrate in solution, g-eq / l.

The reason for the existence of this density range to achieve this goal is due to the fact that iron compounds in the oxidation state are higher than +6, causing a high specific content of the oxidizing agent in the solution, are rapidly restored in concentrated alkalis, and the stability of ferrates increases with increasing NaOH. VI). Going beyond the specified interval of current densities also does not allow to achieve

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with

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set goal Thus, at 5 A / cm, the amount of oxidant is reduced to the level of the prototype. In this case, decomposition of iron-oxidizing compounds occurs due to significant localized overheating in the anode space. At 5- c.

. 0.6 A / cm2, no more than 4.0 g-eq of oxidizer is fixed in the solution. This JQ may be due to processes that occur in the anode space, the nature of which is not known until now.

 It has been established that only activation I in a current of methane leads to the achievement of the goal. For example, the use of such a well-known method of activation (depassivation) as the treatment of the iron anode with a solution of hydrochloric acid does not lead to the achievement of a concentration of sodium ferrate in the solution of more than 4 g-eq / l. This is due to non-: controlled sorption of C ions.

iwhich play the role of restorer

in relation to iron compounds - oxidizing agent on the surface of the anode. O. 5 4 and other organic gases were used as possible activators. The data obtained indicate that a reproducible positive effect is achieved only in the case of activation in a current of methane. The process must be carried out at 150-200 ° C. If the anode is activated at a temperature below, the specific concentration of the oxidizing agent in the solution decreases to the level of the prototype. An increase in the activation temperature of the upper limit (T iZOO O leads to deactivation of the surface and, consequently, a decrease in the specific content of oxidized bodies to the prototype level. The activation time of the anode with methane does not affect the achievement of the goal so when the activation time changes from 15 to 60 mines were not observed to change the content of the oxidizing agent in the solution.

To achieve this goal and eliminate impurities of alkali metal and Fe (ill) compounds in solution, it is necessary to use an electrolyzer made of materials resistant to alkalis and oxidizing agents. The use of glass and / or clay equipment even under the specified conditions is not pos

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five

It is possible to obtain solutions with an abnormally high content of oxidizing agent in the solution.

The proposed method consists in that a two-chamber electrolyzer of fluoroplastic or metal vessels lined with high-pressure polyethylene with a perforated fluoroplastic diaphragm is filled in with a solution of NaOH of a concentration of 1-10 mol / l. A silver electrode is placed in the catholyte, and a plastic iron / tin of metallic iron previously activated in the current of meta- is placed in the anolyte. on at 150-200 ° C. Electrolyzer Pome-. Pull into a bath with running water to cool the anolyte to 20-25 C. The system is adjusted so that the current density is 0.6-17.5 L / cm and the anodic dissolution of iron is carried out. As a result, solutions of iron-oxidant compounds are formed, in which from 4.0 to 6.0 g-eq of oxidant per 1 mole of iron is fixed.

Example 1. The electrolyzer is made of polyethylene and fluoroplastics, the diaphragm is made of a perforated fluoroplastic film. Anolite and catholyte. serves as a solution of NaOH concentration of 6 mol / l. In the anode space is placed 200 ml of alkali solution. An iron plate with a surface area of 4 cm serves as an anode (chemical analysis of the anode is shown in Table 1), the cathode is made of silver. The activation of the anode is carried out by heating in a stream of methane at 175 ° C for 30 minutes. The electrolysis is carried out at a current density of 1.4 A / cm at the anode. Synthesis time does not exceed 20 minutes. As a result, a solution containing 6.0 g-eq of oxidizer per mole of iron is obtained.

. Conducted a series of experiments on the implementation of the proposed method.

In tab. Table 2 shows the values of current density, alkali concentration, anode activation temperature, and the amount of approx. Simitel in g-eq.

Thus, the proposed method, in comparison with the prototype, which is the basic object, allows increasing the concentration of the oxidizing agent in the solution to 6.0 g-eq, avoiding contamination of the target product with impurities of Fe (III) derivatives, silicate, carbonate and other salts. mi soda and also reduce the time

thirty

35

40

50

55

1604863 "

oxidizing compounds of iron. different in that.

that, in order to increase the concentration

Claims (1)

f. ferrates in solution, anodic solution. The invention is carried out in a solution containing g "" mol / l sodium hydroxide at ,, Method ..L ™. 1 I Atomic absorption 0.15 01 Electronic probe a grain center; oh, 085 - oh, 088-o 070 on the grain boundary, o, 064 - o, 000-o, 053 J.J: .. J: L .... 7 5.1 ".o ,, 2, .o ,," .o  The dissolution of iron “p” t, “eko” does not occur, the content of oxidizing agent is below the level prototype. Table 1 Metal content,% prototype.