JPS591688A - Method for reducing iron salt - Google Patents

Abstract

PURPOSE:To easily reduce a tervalent iron salt to an iron salt of lower valence without using additives, by dividing an electrolytic cell with an ion exchange membrane, introducing a mineral acid into the anode chamber and an aqueous soln. of the tervalent iron salt into the cathode chamber, and carrying out electrolysis. CONSTITUTION:An electrolytic cell is divided into anode and cathode chambers with a cation or anion exchange membrane. An about 1-30% aqueous soln. of a mineral acid such as hydrochloric acid is introduced into the anode chamber, and an aqueous soln. of a tervalent iron salt such as ferric chloride or ferric sulfate having about 1-200g/l concn. is introduced into the cathode chamber. Electrolysis is carried out at about 10-70 deg.C, about 0.1-30A/dm<2> current density and about 2-6V electrolytic voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reducing iron salts, particularly a method for electrolytically reducing trivalent iron salts.

For example, when fully plating a steel plate with an alloy of zinc and iron, divalent iron exhibits good adhesion to the steel plate, but trivalent iron exhibits adhesion to the steel plate along with zinc. is significantly reduced, making plating practically impossible industrially.

In general, iron is more stable at higher charges than at lower charges, so there is a strong tendency for iron to dislocate there. Moreover, it is not limited to the above-mentioned plating, and has various uses as a divalent iron salt.

Of course, there is a way to prevent the formation of trivalent iron salts by adding antioxidants to such iron salts, but such additives may have an adverse effect on the material to be treated or the reaction system. There are many cases in which it is harmful.

In order to deal with such cases, Fuyu conducted various research and examinations with the aim of easily reducing trivalent iron salts and rearranging them to lower iron salts without using di-additive gold. As a result, it has been found that the above object can be easily achieved by electrolytically reducing kumquats using an ion exchange membrane.

Thus, the present invention uses an electrolytic cell having an anode chamber and a cathode chamber separated by an ion exchange membrane, and introduces a mineral acid into the anode chamber and a trivalent iron salt into the cathode chamber for electrolysis. The object of the present invention is to provide a method for reducing iron salts.

The mineral acids used in the present invention include hydrochloric acid, sulfuric acid, and phosphoric acid, and these can be used alone or in combination. The concentration of the mineral acid used is generally approximately 1 to 30%. If the concentration is less than the above range, it will be difficult to flow a current with an industrially appropriate current density; on the other hand, if the concentration exceeds the above range, water in the cathode chamber will penetrate into the anode chamber. Both are undesirable because they cause the mineral acid to diffuse into the cathode chamber.

In addition, as trivalent iron salts introduced into the cathode chamber, ferric chloride and ferric sulfate are generally used, and these may be used alone or in combination. The concentration of salt is generally between 1 and 20
It is appropriate to adopt a value of about 0/l. If the concentration is less than the above range, the current efficiency may drop drastically or
On the other hand, if it exceeds the above range, a large amount of iron will be deposited on the cathode, which is not preferable.

Next, the material and shape of the anode used in the present invention are not particularly limited, and the material may be a base material plated or coated with a noble metal such as platinum or a noble metal oxide, and the shape may be, for example, a flat plate. Appropriate shapes such as a shape, a net shape, an expanded metal shape, etc. can be adopted.

The material of the cathode may be lead, iron, platinum, carbon, titanium, etc., and the shape may be similar to that of the anode. Further, as for the material, it is particularly preferable to use lead or platinum among the materials mentioned above, since this prevents the electrodeposition of iron.

Next, the ion exchange membrane used in the invention may be either a cation exchange membrane or an anion exchange membrane.

Examples of cation exchange membranes include sulfonic acid groups, sulfonic acid groups and carboxyl groups, and phosphoric acid groups.

It consists of a single polymer containing a mixture of cation exchange groups such as phenolic hydroxyl groups, and examples of darkening polymers include vinyl monomers such as tetrafluoroethylene and chlorotrifluoroethylene and sulfonic acid, carboxylic acid, and phosphoric acid groups. Copolymers with perfluorinated vinyl monomers having ion exchange groups such as ion exchange groups or reactive groups convertible to ion exchange groups are preferred.

In addition, membrane polymers of trifluoroethylene with ion exchange groups such as sulfonic acid groups, and styrene divinylbenzene with sulfonic acid groups can also be used.

In addition, when using a hydrocarbon-based cation exchange membrane, the ion exchange membrane is composited with a porous membrane of a fluorine-containing resin such as polytetrafluoroethylene or tetrafluoroethylene-hexafluoropropylene copolymer. By using such a fluororesin porous membrane toward the entire anode surface, the entire cation exchange membrane can be protected from high temperature, strongly oxidizing and strongly acidic air. The same applies to this hydrocarbon-based anion exchange membrane.

Further, the above-mentioned fluorine-containing fat cation exchange membrane having a sulfonic acid group is particularly preferred since it has high heat resistance and acid resistance and can be used as is in the present invention.

Further, as the anion exchange membrane, for example, quaternary ammonium base, primary. Second. Examples include a tertiary amine group, a mixture of a quaternary ammonium base and a primary, secondary, and tertiary amino group.

When a cation exchange membrane is used as the ion exchange membrane, hydrogen moves from the anode chamber through the membrane to the cathode chamber due to electrolysis, and this literally exhibits the full reduction effect, and when electrolysis is performed using an anion exchange membrane, Some of the anions that made up the iron salt in the cathode chamber move to the cathode chamber, causing −
The appearance is that dust is produced in the same state as if reduction had occurred in the upper cathode trap, and the term "reduction" that is uninvented includes such a state.

Furthermore, in the present invention, a liquid- and gas-permeable anode is completely directly densely layered on these ion exchange membranes, or a liquid- and gas-permeable, for example, a porous thin N of metal oxide, which has no electrode function, is formed. By using the anode and the cation exchange membrane in close contact with each other via the anode, the electrolytic voltage can be completely reduced, and the purpose of lower energy can sometimes be achieved.

Thus, in carrying out the method of the present invention, the liquid temperature is between 10 and 7
It is appropriate to adopt a temperature of about 0°C.

If the liquid temperature is lower than the above-mentioned φ]L range, the voltage will become high and economical operation will be difficult.If it is higher, on the other hand, gas generation will increase and the operation will become unstable, which is not preferable. Further, it is appropriate to adopt a current density of 0.1 to 30 A/dd.

'A lifting platform with a flow rate less than the above range requires a large r9T membrane area and is not economical when considering industrial equipment. On the other hand, if it exceeds the above range, the efficiency decreases and iron precipitation tends to occur, which is not preferable. or,
It is appropriate to adopt an electrolytic voltage of 2 to 6v2. If the electrolytic voltage is less than the above range, the reduction rate will be extremely low, whereas if it exceeds the above range, the temperature will rise completely and iron precipitation will occur more easily, both of which are not preferred.

Next, the present invention will be explained by examples.

Example 1 Between a platinum anode with an effective electrode area of 6 atti" and a lead cathode with the same area, an average pore diameter of 0.1μ and a porosity of 10 to 40
%, a cation exchange membrane (Celemion cMv manufactured by Asahi Glass Co., Ltd.) in which all sulfonic acid groups are introduced into styrene divinylbenzene on a polytetrafluoroethylene membrane with a thickness of 100μ? I
A battery case was constructed by arranging a membrane of polytetrafluoroethylene [ffi] with a cathode-anode spacing of 35 rIun so as to be opposite to the anode. Hydrochloric acid 'io with a concentration of 15% was introduced into the anode chamber of the cell at a rate of 661/hour, while into the cathode chamber ferric chloride 2 (Jf//lf containing pH 1
, 2 hydrochloric acid bath solution was introduced at a rate of 1101/hour, and electrolysis was carried out at a current density of 7.3 A/am" and a sliding voltage of 6 cm, and products were released from the cathode chamber at a rate of 10 A!/hour. All such substances were analyzed and found to be ferrous chloride (1963).
2) l was contained, and the conversion rate was 45%.

Example 2 The same anode and cathode as in Example 1 were used.

An electrolytic cell was assembled with an anode spacing of 35 M and a fluorine-containing resin membrane containing sulfonic acid groups as cation exchange groups, and 10 units of sulfuric acid was placed in the nuclide cathode chamber at a rate of 0.661/hour. The cathode chamber was filled with a second value iron 107/l'ft: containing a pH 1,2 sulfuric acid bath solution at a rate of τ1101/hour, and the entire electrolysis was carried out at a current density of zoA/an12 and a sliding voltage of 6V. Product was removed from the cathode chamber at a rate of 1101/hr. Such products were analyzed 1 to 9.
The conversion rate was 30%.

Claims (1)

[Claims] 1. Using an electrolytic cell having an anode chamber and a cathode chamber separated by an ion exchange membrane, a mineral acid is introduced into the anode chamber, and a trivalent iron salt aqueous solution is introduced into the cathode chamber. A method for reducing iron salts, which is characterized by electrolyzing the iron salts. 2. The method according to claim (1), wherein the ion exchange membrane is a cation exchange membrane or an anion exchange membrane. 3. The method according to claim (2), wherein the cation exchange membrane is a hydrocarbon-based anion exchange membrane, a composite membrane of a hydrocarbon-based cation exchange membrane and a fluorine-containing porous membrane, or a fluorine-containing cation exchange membrane. 4. The method according to claim (2), wherein the ion exchange membrane is a hydrocarbon anion exchange membrane or a composite membrane of a hydrocarbon anion exchange membrane and a fluorine-containing porous membrane. 5. The mineral acid is hydrochloric acid, sulfuric acid, or phosphoric acid (claim 1).
)the method of. 6. The concentration of the mineral acid is 1 to 30% (1)
)the method of. 7. The method according to claim (1), wherein the trivalent iron salt aqueous solution is ferric chloride or ferric sulfate. 8. The method according to claim (1) or (7), wherein the concentration of the trivalent iron salt aqueous solution is 1 to 2'00 f/1.