RU2334834C1 - Method of reduction of electrolyte for anode preparation of parts on base of iron to ironing - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to electrochemical processing of metals, particularly to reduction of spent electrolyte for anode preparation of parts on base of iron to ironing. The method includes reduction of ions Fe²⁺, Fe³⁺ from spent electrolyte for anode preparation on base of iron to ironing containing saturated solution of aluminium sulphate, sulphur acid and iron salts. As a reducer sheet metal aluminium is used which is loaded into electrolyte on calculation of 50-60 cm²/sheet, and reduction is carried out at temperature 50-98 °C till obtaining the concentration of ions Fe²⁺, Fe³⁺ 0.1-0.2 Fe²⁺, Fe³⁺ 0.1-0.2 g/l.

EFFECT: intensifying of reduction process using contact exchange with extraction of metallic iron; facilitating efficiency and reducing duration of process at more complete removal of iron ions.

2 cl, 1 dwg, 5 ex

Description

The invention relates to the electrochemical processing of metals, in particular to the regeneration of spent electrolyte for anodic preparation of iron-based parts for ironing. In the process of anodic processing of iron-based parts in the electrolyte, the accumulation of Fe ²⁺ , Fe ³⁺ ions occurs, which further affects the adhesion of the coating. To ensure the necessary adhesion, regular replacement of the working solution or reduction of Fe ²⁺ , Fe ³⁺ ions is required.

A known method of reducing metal ions contained in an electrolyte by contact exchange of more electropositive metals is more electronegative.

Contact silvering can be considered as an analogue in which the contact exchange process proceeding due to the difference of electrode potentials is used [1].

The disadvantage of this method is its applicability only in the presence of expensive non-ferrous metals as a reducing agent.

There is also a known method of reducing ions of Fe ²⁺ , Fe ³⁺ from aqueous solutions by electrolysis, when an electric current is used as a reducing agent. This method relates to the implementation of the ironing process from solutions of known compositions containing iron salts, for example: iron chloride 180-200 g / l, sodium chloride 80-100 g / l, hydrochloric acid 3-3.5 g / l. Electrolysis is carried out at a temperature of 70-80 ° C, a current density of 8-10 A / dm ² and a current output of 75-100% [2].

A disadvantage of the known recovery method is that when the concentration of Fe ²⁺ , Fe ³⁺ ions is reduced to 0.1-0.2 g / l, the current efficiency is many times reduced. Therefore, for electrolyte regeneration for anodic preparation of iron-based parts for ironing, it is necessary to conduct electrolysis for 100-200 hours with insoluble anodes and a large consumption of electrical energy.

The objective of the invention is to reduce the duration and energy intensity of the process of regeneration of the electrolyte.

EFFECT: intensification of the process of regeneration of spent electrolyte for anodic preparation of iron-based parts for ironing using contact exchange with the extraction of metallic iron with an economical reducing agent.

The technical result is achieved by the fact that during the regeneration of the spent electrolyte for anodic preparation of iron-based parts for ironing, containing a saturated solution of aluminum sulfate, sulfuric acid and iron salts, by reduction of Fe ²⁺ , Fe ^{3+ ions} , sheet metal aluminum is used as a reducing agent, which is loaded into the electrolyte at a rate of 50-60 cm ² / l, and the reduction is carried out at a temperature of 50-98 ° C until a concentration of Fe ²⁺ , Fe ³⁺ ions is 0.1-0.2 g / l. In one embodiment of this method, waste from disposable tableware is used as sheet metal aluminum.

) делает возможным протекание процесса контактного обмена с извлечением металлического железа (

,

) из электролита для анодной подготовки деталей на основе железа к железнению. При регенерации этого электролита с содержанием ионов Fe²⁺, Fe³⁺ 20-25 г/л при температуре 50-98°С и загрузке листового металлического алюминия из расчета 50-60 см²/л происходит практически полное восстановление ионов Fe²⁺, Fe³⁺ (остаточное количество этих ионов не превышает 0,1-0,2 г/л) за 1-3 часа. Процесс контактного обмена идет по схеме:Used metal aluminum due to the negative value of the electrode potential (

) makes possible the process of contact exchange with the extraction of metallic iron (

,

) from an electrolyte for anodic preparation of iron-based parts for ironing. During the regeneration of this electrolyte with the content of Fe ²⁺ , Fe ³⁺ ions of 20-25 g / l at a temperature of 50-98 ° С and loading of sheet aluminum metal at a rate of 50-60 cm ² / l, almost complete reduction of Fe ²⁺ ions occurs, Fe ³⁺ (the residual amount of these ions does not exceed 0.1-0.2 g / l) for 1-3 hours. The process of contact exchange is as follows:

2Al ⁰ + 3Fe ²⁺ = 3Fe ⁰ ↓ + 2Al ³⁺

or

Al ⁰ + Fe ³⁺ = Fe ⁰ ↓ + Al ³⁺ .

Freshly prepared electrolyte for anodic preparation of iron-based parts for ironing consists of a saturated solution of aluminum sulfate and sulfuric acid, therefore, an increase in the content of Al ³⁺ ions during contact exchange during the reduction of Fe ²⁺ , Fe ³⁺ ions does not affect the performance of the electrolyte.

A graph of the dependence of the concentration of iron ions on the recovery time of Fe ²⁺ , Fe ³⁺ ions by contact exchange at temperatures of 40 and 98 ° C is shown in the drawing.

Example 1. At a concentration of accumulated iron ions of 20-25 g / l, an electrolyte temperature of 40 ° C and loading of sheet metal aluminum at a rate of 50-60 cm ² / l, the reduction of Fe ²⁺ , Fe ³⁺ ions to a concentration of 10 g / l occurs in 1 hour.

Example 2. At a concentration of accumulated iron ions of 20-25 g / l, an electrolyte temperature of 50 ° C and a loading of sheet aluminum metal at a rate of 50-60 cm ² / l, the reduction of Fe ²⁺ , Fe ³⁺ ions to a concentration of 0.1-0 , 2 g / l occurs in 3 hours.

Example 3. At a concentration of accumulated iron ions of 20-25 g / l, an electrolyte temperature of 70 ° C and a loading of sheet aluminum metal at a rate of 50-60 cm ² / l, the reduction of Fe ²⁺ , Fe ³⁺ ions to a concentration of 0.1-0 2 g / l occurs in 2.5 hours.

Example 4. When the concentration of accumulated iron ions of 20-25 g / l, the temperature of the electrolyte is 90 ° C and the loading of sheet aluminum metal at a rate of 50-60 cm ² / l, the reduction of Fe ²⁺ , Fe ³⁺ ions to a concentration of 0.1-0 , 2 g / l occurs in 2 hours.

Example 5. At a concentration of accumulated iron ions of 20-25 g / l, an electrolyte temperature of 98 ° C and a loading of sheet aluminum metal at a rate of 50-60 cm ² / l, the reduction of Fe ²⁺ , Fe ³⁺ ions to a concentration of 0.1-0 , 2 g / l occurs in 1 hour.

At low temperatures, the recovery time of Fe ²⁺ , Fe ³⁺ ions from the electrolyte increases for anodic preparation of iron-based parts for ironing. This is because at lower temperatures the dissolution rate of the oxide film on the aluminum surface decreases, which delays the onset of the contact reduction process of Fe ²⁺ , Fe ³⁺ ions, and also reduces the speed of the contact exchange process.

Information sources

1. Weiner Ya.V., Dasoyan M.A. Technology of electrochemical coatings. M .: Mashgiz, 1962, p. 306.

2. Weiner Y. V., Dasoyan M.A. Technology of electrochemical coatings. M .: Mashgiz, 1962, p. 292.

Claims (2)

1. The method of regeneration of the spent electrolyte for the anodic preparation of iron-based parts for ironing, containing a saturated solution of aluminum sulfate, sulfuric acid and iron salts, including the reduction of Fe ²⁺ , Fe ³⁺ ions, while metal sheet aluminum is used as a reducing agent, which loaded into the electrolyte at a rate of 50-60 cm ² / l, and the recovery is carried out at a temperature of 50-98 ° C to obtain a concentration of ions of Fe ²⁺ , Fe ^{3+ of} 0.1-0.2 g / L. 2. The method according to claim 1, in which waste from disposable tableware is used as sheet metal aluminum.

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