JPS6092491A - Electrolyzing method of potassium carbonate - Google Patents

Abstract

PURPOSE:To form electrolytically K2CO3 to useful KOH by electrolyzing an aq. KOH soln. contg. solid K2CO3 in an electrolytic cell provided with a specific diaphragm. CONSTITUTION:A suspension of an aq. KOH soln. contg. solid K2CO3 is supplied into the anode chamber 5 of an electrolytic cell which is provided with an anode 2 formed of an Ni plate and a cathode 3 formed of Pb and has diaphragm 4 formed of asbestos, PVC, etc. The aq. KOH soln. flows through the diaphragm 4 and enters a cathode chamber 6 from which the soln. is recovered through a circulating line 13 into a KOH tank 14. The solid K2CO3 sticks as a deposition layer 7 on the diaphragm 4. When the layer 7 grows to 0.5-5mm. thickness, the suspension and the KOH soln. are respectively drawn from both chambers 5, 6 and pure water is supplied thereto. A DC voltage is impressed to both electrodes 2, 3 to dissolve and electrolyze the K2CO3 deposited on the diaphragm 4. The formed aq. KOH soln. is taken out of a conduit 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a method for electrolyzing potassium carbonate.

Potassium carbonate is a substance that is produced in large amounts as a by-product from potassium hydroxide and carbon dioxide in alkaline fuel cells, etc., and it is desirable to convert this to potassium hydroxide and reuse it.

Conventionally, the methods for converting potassium carbonate to potassium hydroxide include (1) 2Go3 in a causticizing reaction using calcium hydroxide;
+Ca (OH)2→2KOH+Ca C03 (2) 2C0j-4K2O+ CO2 for calcination and hydration of potassium carbonate 20+H20→2 K O+-1 (3) 2G O, + 2 1-120 -> 2 K O1 for electrolytic reaction
Methods using 1+ CO2+ l-1, + -zO2, etc. are known.

Among these, the causticizing reaction using calcium hydroxide (1) has been used as an industrial method since ancient times. This method has the advantage of being able to perform schemistic reactions. However, it requires a regeneration process to produce calcium hydroxide, and the produced calcium carbonate solid must be separated and calcined, so if the operation 3 and the equipment become complicated, b C? is mixed in, and its complete removal requires an additional expensive treatment such as chelate resin treatment, which increases the number of fibers.

The method (2) of firing potassium carbonate requires a high temperature of about ioO0°C, and many problems remain to be solved regarding the operation, equipment, and materials involved.

The electrolytic method (3) is the easiest method, but the drawback of hFJj is that in the process of separating solid potassium carbonate from the liquid to be treated and electrolytically treating it.
, crystal 41i, separation, redissolution, and electrolysis, which are complicated operations that require a large number of cores.

The present invention provides a method for simplifying and rationalizing the complicated separation and redissolution process in the electrolytic method (3).

The present invention provides an electrolytic cell equipped with an anode J3 and a cathode and partitioned into an anode chamber and one remote electrode chamber by a diaphragm that allows liquid to pass through but does not allow air bubbles J3J and potassium carbonate solids to pass through.
By introducing a potassium hydroxide aqueous solution containing solid potassium carbonate into the anode chamber and leaching the potassium hydroxide aqueous solution through the diaphragm to the cathode chamber side, a precipitated layer of potassium carbonate solid is formed on the surface of the diaphragm on the anode chamber side. After forming, the liquid in both electrode chambers is replaced with water and DC electricity is passed through both electrodes to electrolyze the potassium carbonate solid deposited on the surface of the diaphragm on the anode chamber side, and the potassium carbonate solid is generated from the cathode chamber side. This is a method for electrolyzing potassium carbonate, which is characterized by extracting a potassium hydroxide aqueous solution, i3, and by-product hydrogen.

According to the present invention, (1) Potassium hydroxide, which wastefully consumes power during the reaction, is separated to the maximum extent from the raw material potassium carbonate-18.

(2) Sufficient potassium carbonate is always supplied to the anode chamber during the electrolytic reaction.

(3) Solid potassium carbonate can be processed in a completely closed system,
Excellent IC effects are achieved in that the operation and device system are extremely simplified and rationalized.

Next, the present invention will be explained in more detail.

FIG. 1 is a schematic diagram of an electrolytic cell 1 of the present invention.

In the present invention, specific examples of materials for the anode 2 used include lead, nickel, nickel-plated iron plate, 9% Ni
11.5%Nf mJ5J: (f 18 8 stainless steel is mentioned. Among these, nickel is preferably used.

In addition, specific examples of the material used for shade (4i3) are:
Examples include lead and iron.

The diaphragm 4 used in the present invention is one that allows a potassium hydroxide aqueous solution to pass through but does not allow hydrogen, carbon dioxide gas, and oxygen bubbles, and potassium carbonate solids to pass through, and does not meet the following requirements. dena(] mustn'
J 4 Must be alkali resistant, acid resistant, reduction resistant, oxidation resistant; 0.1% between anode chamber 5 and cathode chamber 6/
Contains a strong acid that can withstand a pressure difference of more than csnF;
It has a heat resistance of 90 to 100℃ for 4 hours;
The size of the eyes is 1 μm or more and 50 μl or less; and there are 31 bamboos that retain the first place in the V4 layer 7.

Considering these requirements, specific examples of materials with an η spacing n'A of 4 include polymeric materials such as asbestos, polytetrafluoroethylene, polyvinyl chloride, polyvinylidene chloride, and polyacrylonitrile, A3, and these polymeric materials. Asbestos is pre-coated using the base material.

An anode 2 and a cathode 3 are connected to both ends of the electrolyzer 1!1, respectively. The electrolysis groove 1 is partitioned into an anode chamber 5 and a cathode chamber 6 by a diaphragm 4 installed in the center.

The oil conduit 9 of the cathode chamber 6 of the electrolytic groove 1 is closed, and a suspension of potassium hydroxide aqueous solution containing solid potassium carbonate is introduced through the oil conduit 8 of the anode chamber 5. The liquid component of the suspension fed into the anode chamber 5 leaks into the cathode chamber 6 through the pores of the partition 1144. In this case, the gas exhaust pipe 10 of the anode chamber 5 is closed, and the gas exhaust pipe 11 of the cathode chamber 6 is left open. In order to maintain a uniform suspension state, the suspension in the anode chamber 5 can be circulated through the circulation line 12 on the side of the anode chamber 5.

The liquid components leached into the cathode chamber 6 are transferred to the cathode side circulation line 13,
Alternatively, the oil is sent from the oil conduit 9 via the circulation line 13 to the storage tank 14 for potassium hydroxide aqueous solution. At this time, the solid potassium carbonate in the suspension is deposited on the surface of the diaphragm 4 on the anode chamber side, forming a deposit E7. The feeding pressure of the suspension to the anode chamber 5 at this speed is l atm l, which is 711. nl
is appropriate. The pressure in the cathode chamber 6 is 1 atm or i
be intimidated. Hotpox is usually treated at room temperature to 90°C.
I'm sad.

Under this operation, the solid potassium carbonate membrane 4
The thickness of the deposited layer 7 on the surface of the anode chamber 5 side is Q, 5 mm or more 10 n+nlX, preferably 0.5 mm 1
mm or less; Lc, the suspension is sent through the oil conduit 8.

After forming the deposit 1ii7 and 1J, the potassium hydroxide solution (,'L) on the cathode chamber 6 side is extracted from the oil conduit 9 and transferred to the storage tank 14 for potassium hydroxide aqueous solution.

On the other hand, the suspension in all the anodes 5 tlj and the anode side circulation line 12 is flited through the gas IJI outlet pipe '10 to the oil conduit 8.
Take it out.

Then l! In the J electrode chamber 5 at and the cathode chamber 6, respectively,
Pure water is fed through oil conduit 8 and oil conduit 9.

In order to prevent backflow of the liquid, the liquid level in the anode chamber 5 should be at least 10 mm higher than the liquid level in the cathode chamber 6.
]8.

After making such preparations, electrolysis begins by passing direct current electricity through both electrodes 2.3. "For DC electricity, a voltage of 2.0 to 2.5V is appropriate.The current density is 3 to 40A/d'TIF, especially 5 to 2OA/d.
It is preferable that it is 1F.

In the cathode chamber 6, potassium carbonate in the potassium carbonate solid deposit layer 7 is gradually dissolved and decomposed by electrolysis, converted into potassium hydroxide, and K 2 ions are accumulated. Also,
The generated 1-12 gas is discharged from the gas outlet 11 of the cathode chamber 6.

In the cathode chamber 6, the potassium hydroxide component gradually increases. Pure water is fed into the cathode chamber 6 through the oil conduit 9 so that 1nrtt of the potassium hydroxide aqueous solution is adjusted to 30% by weight or less, preferably 15% by weight or less, and the potassium hydroxide aqueous solution in the cathode chamber 6 is is drawn into the storage tank 14 while maintaining a predetermined liquid level.

The liquid in both electrode chambers 5.6 is appropriately circulated through the circulation line 12.13, and the liquid temperature in the electrode chambers 5.6 is from room temperature to 901:
, preferably within the range of 40 to 80'C.

Next, let's take a look at the examples.

Example 1 An effective area 10 comprising an anode 2 made of iron and a cathode 3 made of iron, and made of asbestos.
An electrolysis groove 1 with a capacity of 150 cc was used, which was partitioned into an anode chamber 5 and a cathode chamber 6 by a diaphragm 4 of c+nx 10 cn+. Iif an aqueous solution with a potassium hydroxide concentration of 50% by weight and a potassium carbonate depth of 17% by weight at 50°C.
) JJ [1] Introduce a suspension of potassium hydroxide aqueous solution containing solid potassium carbonate into the anode chamber l\full ffi! , :. A liquid component whose main component is potassium hydroxide,
The potassium carbonate solid was leached into the cathode 7+! 6 through one diaphragm and deposited on the anode chamber 5 side of the diaphragm 1. At this time, the thickness of the deposited layer 7 was about 4 InIII.

After that, the remaining liquid is extracted from the bipolar chambers 5 and 5 through the oil conduit 8 and the oil conduit 9, respectively.Next, the anode chamber 5
and pure water to the cathode chamber 6, the oil conduit 8 and the conduit rs+-
ym-h7 Tsum2 j-1 was circulated through the tube. The liquid level in the anode chamber 5 was kept 1011 Ill^ higher than the liquid level in the cathode chamber 6. Next, direct current electricity was applied to both electrodes 5.6 at 2.5 mm, 5 Δ/d1+F to cause an electrolytic reaction. After about 10 hours, the generation of CO2 from the anode chamber 57J) decreased and most of the solid potassium carbonate was electrolyzed.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an electrolytic groove. 1... Electrolytic groove, 2... Anode, 3... Cathode, 4...
・Diaphragm, 5... Anode chamber, 6... Cathode chamber, -7...
Sedimentary layer patent applicant Ube Industries Co., Ltd.

Claims (1)

[Claims] A diaphragm comprising an anode and a cathode and allowing liquid to pass through but not air bubbles and potassium carbonate solids. i
In an electrolytic cell equipped with C1, 1, IJ, a potassium hydroxide aqueous solution containing solid potassium carbonate is introduced into the anode chamber, and the potassium hydroxide aqueous solution is leached through the diaphragm to the cathode chamber side. On the surface of the anode chamber side,
After forming a deposited layer of potassium carbonate solid, the liquid in both electrode chambers is replaced with water, and IJ current electricity is passed through both electrodes to electrolyze the potassium carbonate solid deposited on the wire membrane surface on the anode chamber side. A method for electrolyzing potassium carbonate, characterized in that a potassium hydroxide aqueous solution and a raw water cord U1 are taken out from the W:A electrode chamber side.