JP2582873B2 - Ferrous salt electrolysis method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for obtaining a ferric salt and hydrogen gas by electrolysis using a ferrous salt solution as an electrolytic solution.

(Prior art and its problems) Conventionally, as a method of oxidizing ferrous chloride to obtain ferric chloride, a chlorine gas is blown into the liquid while heating the ferrous chloride solution to 60 to 70 ° C. The most common method of oxidation is a method of adding an oxidizing agent to the ferrous chloride solution to obtain a ferric chloride solution. As the oxidizing agent, nitric acid, chloric acid, bromic acid, There are bromic acid, iodic acid, hydrogen peroxide, hot concentrated sulfuric acid and the like.

In the above method, the former has a drawback that it is difficult to effectively react the blown chlorine gas, requires the treatment of exhaust gas, and has a disadvantage that the equipment is complicated. When the substance added as an oxidizing agent remains or water is generated in the solution and the concentration of ferric chloride decreases, when using the ferric chloride solution,
There is a drawback that a concentration operation and a separation operation are required and the process becomes complicated.

(Object of the Invention) The present invention has been made in order to solve the above-mentioned drawbacks of the conventional method, and is a simple method in which a gas diffusion electrode is used as a hydrogen generating electrode and a ferrous salt solution containing hydrogen chloride is electrolyzed. The present invention provides a stable method which is hardly affected by a change in the concentration of the ferrous salt by using a simple apparatus and method and does not contain other components.

(Means for Solving the Problems) In the present invention, a ferrous salt solution containing hydrogen chloride is electrolyzed using a hydrogen gas generating electrode as a gas diffusion electrode and an insoluble electrode as a counter electrode, and hydrogen gas and ferric iron are used. A method for electrolyzing a ferrous salt, which comprises producing a salt.

 Hereinafter, the present invention will be described in detail.

FIG. 1 is an enlarged cross-sectional view of a gas diffusion electrode. The gas diffusion electrode 1 is a film-like body having two layers, a reaction layer 2 and a gas diffusion layer 3, and the reaction layer 2 has a water repellency having an average particle diameter of 420 °. It consists of carbon black and hydrophilic carbon black, polytetrafluoroethylene (hereinafter referred to as PTFE) with an average particle size of 0.3 μm, and solvent naphtha as a solvent, and the mixing ratio is 7: 4: 4:
At a ratio of 20, a platinum black average particle size of 250 mm
When molded to 0.1 mm, a ratio supporting 0.56 mg / cm ² was added, mixed and compression molded, and then heated and dried at 280 ° C. to remove the solvent.

The reaction layer 2 uses carbon black as a main component in order to impart conductivity as an electrode.

The hydrophilic carbon black is for forming the electrolyte passage, and the water-repellent carbon black is for forming the gas diffusion passage without impairing the performance as an electrode. PTFE as a dressing
Is added.

In addition, platinum is uniformly dispersed throughout to promote an oxidation-reduction reaction and to provide electron conductivity.

The gas diffusion layer 3 is a membrane having only hydrophobic pores of 0.1 μm or less, and is composed of water-repellent carbon black having an average particle diameter of 420 °, PTFE having an average particle diameter of 0.3 μm, and solvent naphtha as a solvent. Mix at a ratio of 0.5 and mold to a thickness of 0.5 mm.
It is dried by heating at 80 ° C to remove melamine.

The gas diffusion layer 3 uses water-repellent carbon black and PTFE to prevent leakage of the electrolyte.

In particular, it has pores for improving gas permeability.

The gas diffusion electrode 1 is obtained by joining the reaction layer 2 and the gas diffusion layer 3 described above, and the gas diffusion electrode 1 can be used with reinforcement. For example, the gas diffusion electrode 1 may be sandwiched and fixed using a metal mesh coated with a resin resistant to hydrochloric acid and iron chloride.

FIG. 2 is a schematic diagram of an electrolysis apparatus using the gas diffusion electrode 1 produced as described above as a hydrogen gas generating electrode.

The electrolysis apparatus 4 has a gas chamber 7 and a gas outlet 8 on the anode 5 and hydrogen generating electrode 6 side, and a diaphragm 9 between the anode 5 and the hydrogen generating electrode 6. The electrolyte solution 10 is allowed to flow.

As the anode 5, an electrode in which a platinum group metal or an oxide thereof is coated on titanium, tantalum, or the like, or a carbon electrode made of carbon fiber or a porous carbon material is used. 1 is set so as to be on the reaction layer 2 side.

FIG. 3 is a schematic diagram when carbon felt is used as the anode. An electrolytic solution 10 composed of an aqueous ferrous salt solution is introduced from below, and is passed through an anode 5 composed of carbon felt fiber, where it is oxidized to ferric ions. In this case, continuous oxidation can be performed without a separator by controlling the flow rate and current density of the ferrous salt.

Electrolyte 10 is composed of ferrous salt, hydrogen chloride and water,
The ferrous salt and hydrogen chloride are preferably in the same molar concentration, and the electrolysis voltage may be 0.8V to 1.2V. Ferrous ions in the electrolytic solution 10 are oxidized by the anode 5 to become ferric ions. On the hydrogen generating electrode 6 side, the hydrogen ions are reduced by the reaction layer 2 of the gas diffusion electrode 1 to become hydrogen gas, which becomes hydrogen gas. 3 and is moved to the gas chamber 7 and taken out from the gas outlet 8.

The use of the gas diffusion electrode can prevent the bath voltage from increasing due to the effect of hydrogen gas generated when a high voltage is applied to increase the electrode oxidation rate.

The electrolysis voltage is the standard voltage required to oxidize ferrous ions to ferric ions while generating hydrogen gas.
0.77V. The hydrogen gas extracted here is used for many purposes.

By supplying oxygen gas from the gas outlet 8 as a method of not generating hydrogen gas in order to lower the electrolysis voltage, a voltage drop of about 0.7 V can be measured under actual electrolysis conditions. This method can be preferably used when hydrogen is not required.

Hereinafter, examples of the present invention will be described, but the examples do not limit the present invention.

(Example 1) A solution in which hydrogen sulfide gas was brought into contact with a solution containing 2 mol / ferric chloride was filtered, and a solution in which precipitated sulfur was separated was analyzed. Hydrogen was 2 mol /.

Using this solution as the electrolyte, the distance between the electrodes was 10 mm, and 1.
Electrostatic potential electrolysis was performed at a voltage of 0V.

Analysis of the solution after electrolysis showed that the concentration of ferric chloride was 2
Mol /.

Four hydrogen gases were obtained from the gas outlet.

The gas diffusion electrode used was 10 cm × 10 cm, and the anode was a lath electrode platinum-plated on titanium and 10 cm × 10 cm.

(Example 2) Electrolysis was performed under the same conditions as in Example 1 except that the anode was changed to a carbon electrode, and the same results as in Example 1 were obtained.

(Example 3) When the electrolysis voltage was set to 0.95 V in the same manner as in Example 1,
The same results as in Example 1 were obtained.

(Example 4) When an aqueous solution containing 0.5 mol / ferrous chloride and 0.8 mol / hydrogen chloride was electrolyzed under the same conditions as in Example 1, an aqueous solution containing 0.5 mol / ferric chloride / 0.3 mol / hydrogen chloride was obtained. Was done.

In the above embodiment, ferrous chloride was described as a ferrous salt, but the present invention is not limited to this, and ferrous sulfate may be used.

(Effects of the Invention) The present invention is a method for obtaining a ferric chloride solution by electrolytic oxidation of a ferrous chloride solution, using a gas diffusion electrode as an electrode on the hydrogen gas generation side, and coating the counter electrode side with platinum on titanium. It can be easily oxidized by electrolysis using an electrode or a carbon electrode, and even if the voltage is increased to accelerate electrolytic oxidation, the bath voltage is reduced because the gas diffusion electrode is used for the hydrogen gas generating electrode. Electrolysis efficiency can be increased without increasing, and hydrogen gas can be easily taken out, which is extremely simple as compared with the conventional method, and the range of use utilizing the characteristics of the ferric chloride solution can be expanded.

As an example, in a contact method with a ferric chloride solution that can be used as a method for treating toxic hydrogen sulfide gas in an oil refinery plant, a solution containing ferrous chloride and hydrogen chloride after separating sulfur is used. The fact that the ferric chloride solution can be circulated and used by converting the ferric chloride solution to hydrogen gas by the electrolytic oxidation method of the present invention can be said to have a very high contribution.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view of a gas diffusion electrode, FIG. 2 is a schematic cross-sectional view showing an example of a ferrous salt electrolysis method of the present invention, and FIG.
The figure is a schematic sectional view showing an example of the present invention.

Claims (1)

(57) [Claims] 1. A ferrous salt solution containing hydrogen chloride is electrolyzed using a hydrogen gas generating electrode as a gas diffusion electrode and an insoluble electrode as a counter electrode to generate hydrogen gas and a ferric salt. Electrolysis method of ferrous salt.