JPS6089600A - Regenerating method of electrolyte to be decontaminated - Google Patents

Abstract

PURPOSE:To recover the dissolved metallic ions in particular in the concd. form as far as possible by conducting DC current between an insoluble anode electrode and a capturing electrode which is a cathode via a diaphragm, depositing and recovering the dissolved metallic ions in the used electrolyte by the cathode and recovering simultaneously the electrolyte in the form of a strong acid in the initial period in an anode chamber. CONSTITUTION:A cathode chamber 2 partitioned by a diaphragm 2 of an electrodepositing and regenerating cell 1 contains the used electrolyte 4 consisting of the acid electrolyte of a high concn. in which radioactive dissolved metallic ions are accumulated. A capturing electrode 5 is installed in said chamber. An anolyte 7 which consists of the acid of the same component as the acid of the electrolyte, is adjusted to about 2pH and is provided with conductivity is contained in an anode chamber 6 having the same capacity as the capacity of the chamber 2. An insoluble electrode 8 is installed in said chamber. DC current is conducted to he electrode 8 as an anode and the electrode 5 as a cathode to deposit and recover the radioactive metal on the electrode 5 and to form the regenerated liquid in the chamber 6. The pH of the electrolyte 4 increases to about 2 in this case and at the same time the amt. of the gaseous H2 to be generated is decreased so that metal deposition takes place.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for removing radioactive metal from an electrolyte that has almost lost its decontamination effect and is used to decontaminate equipment that is radioactive after being used at nuclear power plants. This invention relates to a method for recovering ions as a gold-phase solid and simultaneously regenerating an electrolyte into an initial strong acid solution.

During the process of electrolytic de-dying, among the radioactive substances accumulated in the electrolyte, suspended matter such as gold-oxides, which are released from the surface of the object to be decontaminated into the electrolyte, are removed by circulation filtration of the electrolyte and sedimentation. Minute m. By applying a solid-liquid separation means such as the above, the electrolyte can be relatively easily discharged from the electrolyte system. However, the radioactive substances dissolved in the electrolyte from the object to be decontaminated as metal ions are gradually concentrated and accumulated in the electrolyte solution. Continuing the decontamination work in a state where the radiation level 11) has increased may put workers at risk of radiation exposure. The polishing efficiency decreases due to the increase in the concentration of dissolved metal ions, resulting in a decrease in the electrolytic solution. If a dilute aqueous solution of a strong acid such as 5% sulfuric acid is used as the electrolyte for electrolytic F97 polishing decontamination, the polishing speed will decrease. Although it is easy to carry out hot electrolytic treatment, the surface of the polished surface is rough and easy to recontaminate, so the objects to be removed are limited to n-class materials. When a high concentration acid solution is used for electrolytic polishing decontamination in accordance with general electrolytic polishing, high concentration sulfuric acid systems have poor polishing gloss, but high concentration phosphoric acid systems and high concentration r4 acid-sulfuric acid systems can produce gloss. Therefore, the effect of preventing recontamination of reusable equipment is maximized when VC is used to decontaminate the inner surfaces of containers or parts intended for reuse. However, there are problems with the treatment of waste electrolyte.

In other words, various methods have been proposed to recover the metal ions that accumulate from the electrolyte during the decontamination process, but when a highly concentrated acid solution is used as the electrolyte, the dissolved Until now, it has been difficult to recover gold ions in the a-supplied form. For example, one way to recover dissolved metal ions in an electrolyte is to collect them in an electrolytic tank separated by a diaphragm. $! A method of precipitation and recovery from aiK is known, but in this case, the hydrogen gas generation reaction occurs preferentially at the collection electrode in the cathode chamber partitioned by a diaphragm, rather than the precipitation center of the wire mesh, so the hydrogen ion concentration cannot be reduced. Requirement 2 is to reduce the concentration to a level where metal can be precipitated. However, in a highly concentrated acid solution, there is a large concentration gradient between the anode chamber and the cathode chamber, which are separated by a partition.According to Buddhism, when the acid enters the cathode chamber, it lowers the aqueous ion concentration in the VC cathode chamber, making it possible for metals to precipitate. # It was not possible to reduce the drop, and the diaphragm was not effective.

Depending on the above, you can make a highly concentrated dispersion! Conventionally, when using a decontamination solution, the electrolyte solution that has reached a certain level (dissolved metal ion concentration or radiation dose) is treated as a waste solution by performing plastic assimilation treatment or cement assimilation treatment and discarding it. ing. However, this method of processing waste electrolyte has a problem in that it increases the amount of secondary contaminated waste.

In order to solve the above-mentioned island problem of the prior art, the present invention makes it possible to recover dissolved metal ions in the electrolyte of a highly concentrated acid solution during the electrolytic dedying process in a form as concentrated as possible, and also regenerates the electrolyte and wastes it. The purpose of this invention is to provide a method that makes it possible to suppress the occurrence of waste materials, and to reduce the amount of secondary mine waste bales.

The method of the present invention is that in cell #411, which has an anode chamber and a cathode chamber separated by a diaphragm, the cathode chamber stores a used electrolyte and a collection electrode that have reached a special purpose, and the anode chamber is Add an acid with the same components as the electrolyte to reduce the pH to approximately 2Kv! 4) Contains the prepared aqueous solution and the inert electrode, and 1) DC current is applied to the anode insoluble electrode and the cathode collection electrode through a diaphragm to remove dissolved gold ions in the spent electrolyte from the inner electrode. At the same time, the electrolyte is recovered as a strong acid in the anode chamber.

In the unexploded side force method, settings are made so that the following processes are carried out in a Pl luck manner. In other words, from the dissolved metal ions in the spent electrolyte that has reached the end of its life stored in the Ii & electrode chamber. In order to deposit gold, it is first necessary to remove hydrogen ions from free acids that are not bonded to metal ions as mizuya gas to lower the hydrogen ion concentration.On the other hand, in order to regenerate the electrolyte, Kri cathode The anions separated in the chamber are transferred to the anode chamber through the diaphragm 'f, JI]I, where they are combined with hydrogen ions generated by the insoluble electrolyte at the anode, and the anions are absorbed at the same rate as the acid decomposed in the cathode chamber. It is necessary to regenerate the acid solution with a concentration of 7. To do this, the solution to be stored in the anode chamber must first be a solution that has the same volume as the electrolyte to be stored in the cathode chamber, but does not contain acid. However, a neutral solution containing no acid has poor conductivity and makes diaphragm electrolysis difficult.
The liquid in the anode chamber must be electrically conductive and within a range that does not affect the acid concentration after regeneration. Therefore, in order to make the treated solution conductive due to the awakening of the same components as the electrolytic solution and to use the treatment solution generated in the cathode chamber as the l'A M solution for the next bunch operation, PJ (21j'J
Vt-Klt'! It is preferable to use the prepared solution for the first time.

The present invention is performed by setting the VC as described above and performing a punch-type operation. In the present invention, when electricity is initially applied, hydrogen ions of the acid in the cathode chamber are scattered as hydrogen gas and anions are separated, and at the same time hydrogen ions are generated in the Itjil electrode chamber by an insoluble electrode in parallel with the generation of oxygen. The separated anions move into the anode chamber and combine with hydrogen ions to be regenerated into acid again. Continuing this reaction process, the hydrogen ion concentration in the cathode chamber gradually decreases and when pH=2VC is reached, dissolved 4','-U ions are deposited on the collection electrode. During this time, the separated anions move to the Li electrode chamber and are similarly regenerated as an acid. Therefore, in the end, l'lil
The rod chamber contains the same high concentration of dissolved oxygen and ions as the original electrolyte.
The removed acid f'8# is regenerated, which can be used as an electrolyte for electrolytic de-dying, - force-yin-like chamber K u Ji
When the center of gravity of the dissolved gold ions is collected on the ffits electrode, there remains a solution that hardly contains dissolved gold ions with a VCPH of about 2. The solution in the cathode chamber can then be transferred to the solar chamber for the next batch operation and used as a VC in the same way as the pH adjusting solution 2 described above. By repeating this punching operation, it is possible to recover the remaining gold (1 iodine) as gold powder and regenerate the electrolyte without producing any waste liquid. In the cathode chamber (3) partitioned by a diaphragm (2) in the electrodeposition regeneration tank (1), Vt- is the spent electrolyte (4) that has reached the ν life, i.e. # of the radioactive dissolved gold io/ A collecting electrode (5
) was rebuilt and the anode chamber (6) with the same capacity loss as the 1st electrode chamber (3) was used. ) and an insoluble 71j electrode (8) made of platinum-coated titanium. Then, one page of current was applied using the insoluble electrode (8 mm as a quadrupole and L 4 Tl) as the collector electrode (5) as the cathode, and the collector electrode (5) was used as the cathode.
) upper r (dissolved potential ions are precipitated and recovered, and the anode chamber (6) K generates a regenerated electrolyte (σ). Ω At the beginning of energization, the hydrogen ion concentration of the electrolyte in the cathode chamber (3) is high and the collection electrode (5) ), a large amount of hydrogen gas is generated and gold drop does not precipitate, but as the PI of the electrolyte (4) rises to 28+! degrees r, the amount of hydrogen gas generated decreases and precipitation occurs at the excess. K.Then, this anion is produced in the cathode chamber (3) and becomes K in the anode chamber (6).
112 in the infallible electrode (8) in the transition 1 electrode chamber (6)
Combines with hydrogen ions generated by the release of hydrogen atoms to form an electrolyte VC
If a predetermined result is reached by 5JJf + electric connection #i, the punching operation ends.

It's a quasi-fi with electricity! ll If the pH in the cathode chamber (3) rises too much, remove the
), the regenerated electrolyte in the anode chamber (6) can be added to the 18-electrode chamber (3) by operating the bo/p00 to control pn=21c for high electrodeposition efficiency. can.

Numerical examples of the method of the present invention are shown below.

(1) The target is a used electrolyte produced by electrolytically dedying 5US14 filth with an electrolyte containing 75ωt% phosphoric acid.

This liquid pζ is 62.5 g of chromium ion/Is chromium ion 9
．． 75g//s Nickel ion 1.75g/l
, 0.21 g// of cobalt ions are dissolved. This liquid is stored in the cathode chamber (3) of the apparatus shown in the attached figure, and the anode chamber (6)
Contain P)12 ICC corrected liquid and perform diaphragm electrolysis at a current density of IOA/a of 3.500 AH/l.
carried out up to. As a result, the amount of iron ions added to the liquid in the cathode chamber (3) was 0.045 g/li.
Chromeio 70.052g//, Nickel ion 0.
067g/l 1 Cobalt ion 0.002(g//
k, - force 1 - the phosphoric acid / in the polar chamber (6) is 1
250g/i? ! : Almost completely the original 75ωt
It was played as 5+5 Takano Anti-Fried General Jun 2. However, it was observed that approximately 20% gold ions leaked into the regenerating solution through i't tiM 1M (2).

(: M) niJ (1) As in the example, K and phosphoric acid 70
Autumn, chromium, produced by de-dying the two-component Takashi Iy1 solution containing ωt% and 30ωt% sulfuric acid as electrolyte oil,
When diaphragm electrolysis was carried out using the Kamemoto Inventive Power Method using a used electrolytic solution in which nickel and cobalt ions were dissolved to about 100%, similar results to Example 4 [1] were obtained.

In particular, according to the method of the present invention, the phosphoric acid/fluoric acid regenerated solution in the anode chamber (6) has the same mixing ratio as the original electrolyte. ! : Used in conjunction with electrolysis with high concentration acid, which is advantageous, the radioactive substances removed from the equipment to be decontaminated are concentratedly captured by the collection electrode, reducing the concentration of radioactive substances. It is now possible to dispose of the electricity ri'+ that has been used for electrolysis 1 after-dyeing.
Since I-liquid is regenerated and reused, the amount of 6sodium that must be treated as radioactive waste is eliminated or reduced, which has the effect of solving the problem of diffusion of 2υ (dirt!1g).

[Brief explanation of the drawing]

The attached figure is a Z diagram of an example of the lateral arrangement of the apparatus for applying the method of the present invention. (1) Electrodeposition regeneration stand, (2) Diaphragm. , (3)...
Cathode chamber) (4) ・ ・ 1 meeting Pole chamber Kin, Ri5)
・ ・ t+Ii collector electrode, (6) ・ ・Anode chamber, (7)... Ceramic chamber fluid, (8)... Insoluble status accumulation, (
9)...PHI71, 4-bo/bu.

Claims (1)

[Claims] Radioactive gold is recovered from the highly concentrated acid electrolyte containing radioactive gold N ions used for electrolytic de-dying to a collection electrode, and the electrolyte is then recovered from the initial high concentration. A method for regenerating into Q-degree acid using a diaphragm.
The anode chamber of the electrodeposition regeneration tank, which replaced the anode chamber and cathode chamber of equal volume, contained a solution prepared by adjusting PJ (after 2 QiJ) with an acid of the same composition to make it conductive, and an insoluble 4'1 electric rod was placed in the anode chamber. installed,
The cathode chamber contains a highly concentrated acid spent electrolyte solution containing radioactive ions, and a collection electrode such as a singing board is installed.By applying direct current, radioactive metal is collected on the collection electrode, and the anode chamber A method for regenerating a decontamination electrolyte using the FPA Den MK, which is characterized by regenerating a highly concentrated acid solution as an electrolyte.