JPH048393B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrolytic refining method for kaolin and clay, in which iron content in kaolin and clay is removed by electrolytic leaching with a sulfite solution. .

That is, in the method of the present invention, sulfurous acid and sulfuric acid solution and kaolin or clay are placed in the cathode chamber, and sulfurous acid and sulfuric acid solution are placed in the anode chamber for electrolysis. On this occasion,
In the cathode chamber, dithionite is produced by electrochemical reduction of sulfite, and the produced dithionite leaches the iron in the kaolin or clay. On the other hand, in the anode chamber, sulfuric acid is produced by electrochemical oxidation of sulfurous acid, and the voltage drops.

[Prior art and problems to be solved by the invention]

The methods for refining kaolin and clay that have been mainly used up to now can be classified into two types: physical separation methods and chemical treatment methods. Physical separation methods include flotation, selective flocculation, and high gradient magnetic separation. In flotation, the pH of the mineral solution is adjusted by NaOH,
_{Alkalinity ( PH8}
~10), add a dispersant of Na ₂ SiO ₃ and stir at high speed to disperse the ore grains, then use hydrocarbon compounds such as oleic acid or petroleum sulfonate etc. as a collector. impurities are collected and removed by floating matter (EKCundy, US Patent No.
3450257) (1969)). In selective flocculation, the pH of the mineral solution is made alkaline, the ore grains are dispersed in a dispersion liquid, and then ions of the same amount as Ca ⁺² are added to remove impurity minerals such as quartz, iron oxide, and titanite. A polymer flocculant such as anionic polyacrylamide is adsorbed onto the grains, and these impurity mineral grains are selectively flocculated and removed by washing with water (EW).
Sawger, U.S. Pat. No. 3,737,333 (1973)). In the high-gradient magnetic separation method, a ferromagnetic medium such as steel wool is placed inside to separate weakly magnetic ore grains under a magnetic field of tens of thousands of Gauss, increasing the effect of separating weakly magnetic ore grains ( ALNott, U.S. Patent No.
No. 3974067 (1976); RROrder, U.S. Patent No.
No. 3985646 (1976)).

As described above, physical methods are effective only when the degree of separation of minerals and other substances containing impurities is high.

The purpose of the chemical treatment method is usually to improve whiteness by leaching out colored minerals attached to the surface of kaolinite grains or mixed in extremely fine grains. This method is also used to decolorize and remove iron, but in this case it must not change the kaolin and clay, and it must be possible to selectively leaching out only impurities. Therefore, leaching with strong acids is difficult in terms of decomposing kaolin, so it is appropriate to use a strong reducing leaching agent such as dithionite (J. Iannicelli and P. Aboytes, U.S. Pat.
No. 3193344 (1965); CRPrice and WF
Abercrombie, U.S. Pat. No. 3,853,984 (1974)).

Other leaching agents include Hypochlorite (JHCauman, U.S. Pat.
No. 3655417 (1972)), hydrazine (PJ Malden,
U.S. Patent No. 3,666,513 (1973), Alkyl Sulfoxide (JCLim, U.S. Pat. No. 3,899,343 (1975))
etc. are sometimes used, but so far they have not been put into practical use. Also, as a leaching agent for iron removal,
Hydrochloric acid, sulfuric acid, hydrofluoric acid (〓〓), etc. can also be used (K.Azuma and H.Kametani, AIME
Trans., 230653 (1964); REGrim, Clady,
Mineralogy, McGraw-Hill Book Co., P435
~444 (1968)), in this case the kaolin or clay is decomposed and the aluminum component is dissolved.
This is not preferred because the physical properties of kaolin change.

The iron removal method using dithionite reduces and leaches the iron in kaolin, and is currently mainly used. However, the dithionite reagent is relatively expensive, and in order to increase the iron removal effect, it is necessary to adjust the pH of the solution. Since the reduction potential of iron and iron must be maintained, a large amount of dithionite is consumed, causing operational difficulties.

[Means for solving problems]

The present invention provides for the purification of kaolin and clay,
The dithionite leaching agent, which has been mainly used so far, is electrochemically generated directly from a sulfite solution in the cathode chamber to leach the iron in kaolin or clay, and in the anode chamber, the sulfite solution is electrochemically generated. This is a method of oxidizing sulfuric acid to lower the voltage and producing sulfuric acid used for leaching kaolin.

The dithionite production reaction and standard potential by electrochemical reduction of sulfite solution in acidic and alkaline solutions are as follows (C.
Oloman, J.Electrochem.Soe., 117(12), 1604,
(1970)).

Acidic solution 2H ₂ SO ₃ +H ⁺ +2e ^- →HS ₂ O ₄ ^- +2H ₂ O (1) E ₀ =0.08V Alkaline solution 2SO ₃ ^-2 +2H ₂ O+2e ^- →S ₂ O ₄ ^-2 +4OH ^- (2) E ₀ = 1.12V Dithionite produced by electrochemical reduction of sulfite solution reduces and leaches iron present in kaolin or clay, and the reaction formula is as follows (Journal of the Korean Society of Mines). , 15(4), 315
(1978)).

Fe ₂ O ₃ +S ₂ O ₄ ^-2 +4H ⁺ 2Fe ⁺² +2HSO ^- ₃ +H ₂ O (3) 2FeO(OH) +S ₂ O ₄ ^-2 +4H ⁺ 2Fe ⁺² +2HSO ^- ₃ +2H ₂ O (4) Anode chamber In order to electrochemically oxidize a sulfite solution, which is a small polar medium, to reduce the energy consumption of the anodic reaction and to produce sulfuric acid used for leaching kaolin or viscosity, the oxidation reaction of sulfite in an acidic solution and the standard Looking at the potential, it is as follows (AJ Appleby and B. Pichon, J.Electronal.
Chem., 95, 59 (1979)).

SO ₂ +2H ₂ O→HSO ^- ₄ +3H ⁺ +2e (5) E ₀ =0.12V To explain the present invention with reference to the accompanying drawings, FIG. 1 is a sectional view of an electrolytic cell 10 used in the method of the present invention. The electrolytic cell 10 is separated by a diaphragm 1 into an anode chamber 2 and a cathode chamber 3. The cathode chamber 3 contains a sulfite solution and kaolin (or clay), and the anode chamber 2 contains sulfuric acid and a sulfite solution. inject. For the anode 4, a porous graphite electrode that is effective in oxidizing sulfite solution is used, and for the cathode 5, a platinum electrode, an aluminum electrode, or a stainless steel electrode is used.
In the cathode chamber 3, dithionite is produced by electrochemical reduction of sulfur dioxide gas, and the iron content in kaolin or clay is removed and purified by the produced dithionite. In the anode chamber 4, sulfuric acid is produced by electrochemical oxidation of sulfur dioxide gas, and the electrolytic voltage drops. At this time, the generated sulfuric acid is used again as an electrolytic leachate in the anode chamber 4. A stirring rod 6 is provided in the cathode chamber 3.

FIG. 2 is a diagram of the kaolin leaching process of the present invention.
In the anode chamber, the sulfurous acid solution is oxidized to produce sulfuric acid. A portion of the generated sulfuric acid is used for the kaolin leachate in the cathode chamber, and the rest is recovered and dissolved in the sulfur dioxide gas before being sent to the anode chamber. Use again as a solution. In the distribution tank, gangue such as quartz and feldspar present as impurities in kaolin is removed. The kaolin that has passed through the distribution tank is polished, mixed with a sulfite solution in a mixing tank, and then flows into the cathode chamber of the electrolytic tank. In the electrolytic tank, the iron in kaolin is electrolytically leached to refine kaolin. The purified kaolin mineral liquid is passed through a filter tank and separated into kaolin and peroxide. The filtered kaolin is recovered as purified kaolin through a water washing process and a drying process. The filtrate is returned to the mixing tank, mixed with highly concentrated sulfuric acid produced in the anode chamber, and then flows into the sulfite dissolution tank. Sulfurous acid gas is dissolved in the sulfurous acid dissolving tank. This sulfite solution is mixed with kaolin that has passed through grinding in a kaolin mixing tank, and then flows into the cathode chamber of the electrolytic cell.

When kaolin is purified by the electrolytic method of the present invention, it is generally possible to remove about 50 to 60% of the iron content in kaolin, although there are slight differences depending on the sample. This is approximately 10% higher than the leaching rate of 40-55% using dithionite. The present invention eliminates the need for pH adjustment and potential adjustment associated with leaching to dithionite, and can prevent unnecessary consumption of excessive amounts of dithionite.
It is also easy to operate. In particular, the advantage of this electrolytic leaching process compared to other leaching processes is that it utilizes sulfite gas, and since leaching is carried out in the electrolytic bath at the same time as dithionite is produced, It is a very economical and effective leaching process. When leaching with dithionite, increasing the acidity of the solution destroys the dithionite, so it was advantageous to work in the pH range of 2 to 3, but in the electrolytic leaching process of the present invention,
Since electrolytic leaching can be performed with a strong acid of about 0.1M to 2.0M, the leaching efficiency can be increased.

The present invention not only aims to purify kaolin, but also utilizes sulfite gas, which is a small polar medium, in the anode reaction to prevent evaporation of the dissolved material and the huge consumption of electrical energy due to the oxygen generation reaction that occurs in the absence of sulfite gas. This is a method for simultaneously producing sulfuric acid used in kaolin purification. The electrolysis voltage varies slightly depending on the sulfuric acid concentration and current density, but when the sulfuric acid concentration is 0.1M to 2.0M and the current density is 10mA/cm ² to 100m
It is about 1.0V to 2.0V under A/ ^cm2 . Appropriate working conditions for electrolytic leaching of kaolin are sulfuric acid concentration
0.1M~2.0M, sulfite gas concentration 0.1M~1.0M, temperature 20℃~50℃, solid concentration 10%~50% and current density
It is 10 mA/cm ² to 100 mA/cm ² .

Regarding the electrode materials for the anode and cathode, from the viewpoint of the required voltage, a platinum electrode can perform electrolytic leaching at the lowest voltage, but since platinum is expensive, in the present invention, platinum electrode is effective for sulfite oxidation as an anode. It is preferable to use a porous graphite electrode, and as a cathode, use an aluminum or stainless steel electrode, which is effective in reducing sulfite.

〔Example〕

Example 1 After injecting 0.5M sulfuric acid + 1.0M sulfite gas + 20% kaolin solution and 0.5M sulfuric acid + 1.0M sulfite gas solution into the cathode chamber and anode chamber, respectively, a graphite anode and a platinum cathode were used as both electrodes. , total current 0.45A for Damingshan 0.82% Fe kaolin (current density 50mA cm ² )
Electrolytic leaching was carried out for 1 hour under

Refined kaolin obtained from electrolytically leached kaolin liquid through filtration, water washing and drying processes has a low iron content.
The iron content was 0.32%, and the iron removal effect was 61%.

The electrolytic voltage is about 1.4V, and the cathode potential is about −275
mV (vs SCE).

Example 2 Example 1 for a sample in which Daimingsan 2.28% Fe kaolin and 1.90% Fe kaolin were dispensed into particle sizes of 10μ or less
Electrolytic leaching was carried out in the same manner as the experimental conditions.

The iron content of kaolin purified through filtration, water washing and drying processes is 0.87% and 0.77%, respectively.
The iron removal rates were about 65% and about 60%, respectively.

The electrolytic voltage is about 1.4V, and the cathode potential is about -280
mV (vs SCE).

Example 3 The cathode chamber solution was 0.5M sulfuric acid + 0.1M sulfite gas + 20
% kaolin solution, and electrolytically leached Damingshan 0.82% Fe kaolin using the same experimental conditions and method as in the example.

The iron content of the purified kaolin was 0.43% Fe, and an iron removal effect of approximately 48% could be obtained.

The electrolytic voltage is 1.4V, and the cathode potential is approximately -240m.
It was V (vs SCE).

[Brief explanation of drawings]

FIG. 1 is a sectional view of an electrolytic cell used in the method of the present invention. FIG. 2 is a flowchart of the kaolin purification process according to the method of the present invention. 1...Diaphragm, 2...Anode chamber, 3...Cathode chamber, 1
0... Electrolytic cell.

Claims (1)

[Scope of Claims] 1. A sulfuric acid and sulfite solution and kaolin or clay are placed in the cathode chamber of an electrolytic cell separated by a diaphragm into a cathode chamber and an anode chamber, and a sulfuric acid and sulfite solution is placed in the anode chamber. A method for electrolytically refining kaolin and clay, which comprises performing electrolysis and leaching out iron in kaolin or clay. 2. The method according to claim 1, wherein the sulfuric acid produced by electrochemical oxidation of sulfurous acid in the anode chamber is reused as the electrolytic leachate. 3 In the cathode chamber, the sulfuric acid concentration is 0.1-2.0M, the sulfite concentration is 0.1-1.0M, and the kaolin or clay concentration is
10 to 50%, and the sulfuric acid concentration in the anode chamber to 0.1 to 50%.
2.0M, sulfite concentration 0.1~1.0M, temperature 20~
50℃ and current density 10mA/cm ² ~100m
A method according to claim 1, in which A/cm ² is obtained. 4. The method according to claim 1, wherein a platinum, aluminum or stainless steel electrode is used as the cathode and a porous graphite electrode is used as the anode.