JPH0245300B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for regenerating an electrolyte used in electrolytic deposition. Conventionally, as a method for filling a porous electrode substrate such as a porous nickel sintered body with a nickel active material, a nickel salt aqueous solution such as nickel nitrate or nickel sulfate is used as an electrolyte, and a nickel plate is used as a counter electrode to perform negative electrolysis. The production of nickel electrode plates by the so-called electrolytic deposition method in which a nickel hydroxide active material is deposited within a porous substrate is known, but as time passes during the electrolytic deposition process, ammonium ions NH ₄ ⁺ It forms in large quantities, which reduces the precipitate impregnation of nickel hydroxide in the substrate and makes efficient continuous operation difficult. In order to achieve continuous electrolytic deposition with good impregnating properties, it is necessary to control the ammonium ions below a certain level. For this reason, ammonium ions are removed in the form of ammonia gas by replacing the electrolyte with a new electrolyte or adding an alkaline aqueous solution to the electrolyte, and then neutralizing the alkalinity with acid to regenerate the electrolyte from which ammonium ions have been removed. Measures such as reusing the electrodes have been used, but this increases manufacturing costs and requires the use of chemicals for regeneration, and due to neutralization, NaNO ₃ remains on the electrode plates and deteriorates their self-discharge characteristics. It is accompanied by disadvantages such as being undesirable. The present invention eliminates these drawbacks and provides a method for regenerating the electrolytic solution used in electrolytic deposition, which can efficiently remove ammonium ions without using chemicals, and which enables continuous production. In a method for regenerating an electrolytic solution containing ammonium ions generated in the process of electrolytically depositing an active material onto an electrode substrate for an alkaline storage battery, the electrolytic solution is removed from an electrolytic tank, and the electrolytic solution is heated and concentrated. It is characterized in that it is cooled to precipitate the active ingredient as crystals, and then separated from the liquid and the resulting crystals are dissolved in water to form an electrolytic solution with a predetermined concentration. An example of implementing the present invention will be described with reference to the accompanying drawings. Figure 1 shows an electrolytic deposition apparatus A for nickel hydroxide active material used in the production of nickel electrodes for alkaline storage batteries, which is equipped with an electrolyte regeneration apparatus that implements this method, in which 1 is an electrolytic tank and 2 is a DC power source. , 3 is DC power supply 2
4 is a strip-shaped sintered nickel substrate connected to the DC power supply 2, and 5 is an electrolytic solution contained in the battery case 1. The strip-shaped nickel sintered substrate 4 passes through the electrolytic solution 5 in the battery container 1 through an unwinding roll 6 on one side and is wound up onto a winding roll 7 on the other side, thereby enabling continuous electrolytic deposition work. 8 indicates a plurality of guide rollers that guide the substrate, and one of the guide rollers is connected to the power source 2. The substrate 4 has, for example, a porosity of 80% and a thickness of 0.68 mm. Using this electrolytic deposition apparatus A, continuous electrolytic deposition of a substrate is performed. The conditions in this case are, for example, electrolyte 5
is a 4M nickel nitrate aqueous solution, 120mA/
The substrate 4 at a constant speed as a constant electrolytic condition of cm ²
is immersed in an electrolytic solution 5 to perform negative electrolysis with a counter electrode plate 3.According to the present invention, an electrolytic solution device B for carrying out the present method is attached to the device A as follows, and the electrolytic solution is A part of the electrolyte 5 is taken out, regenerated, and returned to the electrolytic bath 1 to keep the ammonium ion concentration in the electrolytic solution 5 below a certain level at all times, and the active material is continuously electrolytically deposited. I made it possible to do it. That is, the regeneration tank 9 has a jacket 9a in which a refrigerant such as water and a heat medium such as heated steam are exchanged and circulated. The regeneration tank 9 includes a drain pipe 1 from the electrolytic tank 1.
The top surface is open to receive 0. On the side of the lower part of the regeneration tank 9, there is an on-off valve port 11 for taking out the separated liquid.
A prepared liquid supply pipe 12 whose tip end is located on the upper surface of the battery container 1 is provided at the lower part and other side surfaces thereof, and a valve closing valve 13 and a pump 14 are interposed in the pipe 12. A net-like filter or the like can also be provided inside the separated liquid extraction valve port 11. In order to regenerate the electrolytic solution using this device, when the ammonium ions generated in the electrolytic solution 5 in the electrolytic cell 1 during the electrolytic deposition process become excessive to the extent that the active material precipitation generation efficiency decreases. , a part of the electrolyte is taken out from the drain pipe 10 into the regeneration tank 9 and the electrolyte is passed through the jacket 9a of the regeneration tank 9 through a heating medium such as heated steam.
Heat to over 100℃ to evaporate water and reduce the initial volume to 70
Concentrate it to about 80%, then cool it to 20°C by passing a refrigerant into the jacket 9a and leave it. When about 80% of the volume has been crystallized, the take-out valve 11 is opened to separate and remove the liquid. This liquid fraction contains ammonium ions in a high concentration, and almost no ammonium ions remain on the side where they remain as crystals. In this way, a predetermined amount of water is added and heated in the regeneration tank 9 in which the crystals remain, or hot water is directly added to dissolve the crystals to prepare an electrolytic solution of a predetermined concentration. By repeating the regeneration of the electrolytic solution 5 and returning it to the container 1 in this way, the electrolytic deposition method can always be carried out with a predetermined good electrolyte state, resulting in highly efficient electrolytic deposition. I can work. Next, we compared the changes in the ammonium ion concentration, the changes in the amount of active material impregnated, and the residual capacity ratio (case) of the electrolyte produced using the electrolyte regenerated by this method to those obtained without regenerating the electrolyte (case). case) and regenerated case where ammonia gas is removed from the electrolyte with alkali and then redissolved with nitric acid (case)
Comparative tests and measurements were conducted on each of these, and the results shown in Table 1 below were obtained.

[Table] Initial capacity
As is clear from the above table, the electrodes manufactured using this method are the same as those in the case where the liquid is not regenerated at all.
It can be seen that an electrode with a high residual capacity ratio and less so-called self-discharge can be obtained compared to the case where the electrode is removed and regenerated using an alkali. Moreover, this regeneration method has the advantage that the regeneration cost is significantly lower than the removal regeneration method using alkali. In this way, according to the present invention, mere heating,
Ammonium ions can be easily removed by physical means of cooling, and the electrolyte can be regenerated simply by dissolving the separated active ingredient crystals in water, and does not contain impurities compared to regeneration using alkali or acid. Regenerates into a good electrolyte.

[Brief explanation of drawings]

The drawing shows a diagram of an example of implementing the invention. A... Electrolytic deposition device, 1... Electrolytic cell, 4... Electrode substrate, 5... Electrolyte, B... Electrolyte regeneration device,
9... Heating/cooling regeneration tank, 9a... Jacket, 1
0...Drain pipe, 11...Separated liquid take-out opening/closing valve port, 12...Prepared liquid supply pipe, 14...Pump.

Claims (1)

[Claims] 1 In a method for regenerating an electrolytic solution containing ammonium ions generated in the process of electrolytically depositing active materials onto electrode substrates for alkaline storage batteries, the electrolytic solution is removed from the electrolytic tank, heated and concentrated, and then An electrolytic solution used in an electrolytic deposition method characterized by cooling to precipitate the active ingredient as crystals, and then separating it from the liquid and dissolving the obtained crystals in water to obtain an electrolytic solution with a predetermined concentration. Regeneration method.