JPH0549757B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing electrolytic manganese dioxide using a slurry method, and relates to an improved method for producing electrolytic manganese dioxide deposited on an anode plate evenly and homogeneously. [Conventional technology] Currently, electrolytic manganese dioxide (hereinafter referred to as EMD)
When manufacturing EMD, EMD is deposited onto the anode plate using a method of suspending manganese oxide in an electrolytic solution and electrolyzing it (hereinafter referred to as the slurry method). The slurry method has an advantage over a method of electrolyzing manganese oxide without suspending it in an electrolytic solution in that electrolysis can be performed at a high current density and without making the anode plate or the like nonconductive. [Problems to be solved by the present invention] As mentioned above, the slurry method has the advantage of being able to manufacture at high current density, but on the other hand, the EMD deposited on the anode plate has a large thickness at the top and bottom of the anode plate. However, there is a drawback that variations occur in the components, crystal state, etc. The present invention eliminates the variations in thickness, composition, and crystalline state in the slurry method and provides a method for producing EMD deposited on an anode plate having a uniform thickness, composition, and crystalline state. It is in. [Means for Solving the Problems] The present invention is an EMD manufacturing method using a slurry method, in which the current density is increased at a rate of 0.2 A/dm ² /min or less from the start of electrolysis until reaching a predetermined current density. This is a method of manufacturing EMD having uniform thickness, composition, and crystalline state at the upper and lower parts of the EMD deposited on the anode plate by electrolyzing the anode plate. [Function] The present invention is constructed as described above, and electrolysis is performed by starting the current density during electrolysis from a value close to 0 and gradually increasing the current density. In other words, gradually increasing the current density means increasing the rate of increase in current density per unit time to 0.2A/dm ² /
Alternatively, the current density may be gradually increased linearly to a predetermined current density, or the current density may be electrolyzed for several minutes at a low current density, the current density may be increased, electrolysis may be carried out for several minutes at that current density, and this process may be repeated sequentially. A method may also be used in which the current density is increased in so-called steps to a predetermined current density. In this case, the rate of increase in current density is
0.2A/dm ² /min. FIG. 1 shows an example in which the current density is linearly increased from the initial stage of electrolysis to a predetermined current density. That is, when the predetermined current density is 2.5A/ ^dm2 , as shown by the solid line, the current density changes from 0 to
Slowly increase the voltage to 2.5A/ ^dm2 over about 40 minutes. Also, when the predetermined current density is 1.2A/ ^dm2 ,
It is sufficient to raise the temperature in about 10 minutes as shown by the dotted line. Furthermore, Fig. 2 shows an example of increasing the current density stepwise from the initial stage of electrolysis until reaching a predetermined current density.
m ² , electrolysis is performed for about 15 minutes at an initial current density of 0.2 A/dm ² , and then the current density is increased by 0.2 ^{to 0.4 A/dm 2 .} Approximately 5 minutes, approximately 8 minutes at 0.3A/ ^dm2 ,
Electrolysis is carried out by increasing the current density little by little for about 12 minutes at 0.4 A/dm ² . That is, in the conventional electrolytic method, electrolysis is carried out at a predetermined current density immediately from the beginning of electrolysis, whereas in the present invention, electrolysis is carried out at a low current density in the initial stage of electrolysis, and the current density is gradually increased to carry out electrolysis at a predetermined current density. . [Example] A 1 mol/concentration manganese sulfate solution was used as an electrolyte, and 1 g/g of manganese dioxide pulverized to less than 30μ was suspended in the electrolyte. A graphite plate was used as the cathode and a Ti plate was used as the anode. Every 5 minutes at the beginning of electrolysis
Electrolysis was carried out at a current density of 0.2 A/dm ² gradually increasing stepwise for 40 minutes and at a predetermined current density of 1.6 A/dm ² . Table 1 shows the rate of increase in bath voltage when electrolyzed for 7 days in comparison with the conventional method.

[Table] Table 2 shows the characteristic values of EMD obtained by the method of the present invention and the conventional method.

【table】

〔Effect of the invention〕

As described above, in the slurry method electrolysis, the present invention
From the beginning of electrolysis to the predetermined current density, electrolysis is performed at a low current density initially, and by increasing the current density at a rate of 0.2 A/dm ² /min or less to reach the predetermined current density, the electrolysis is deposited on the anode plate. This has the effect of making the thickness, composition, and crystalline state of the upper and lower parts of the EMD uniform, making it possible to obtain EMD of stable quality and reducing the rate of increase in bath voltage during electrolysis.

[Brief explanation of drawings]

FIG. 1 is a graph of an example of a case where the current density is increased linearly, and FIG. 2 is a graph of an example of a case where the current density is increased stepwise.

Claims (1)

[Claims] 1. In producing electrolytic manganese dioxide by the slurry method, the current density is increased at a rate of 0.2 A/dm ² /min or less during electrolysis from the start of electrolysis to the current density. A method for producing electrolytic manganese dioxide using a slurry method characterized by electrolysis. 2. According to the slurry method according to claim 1, wherein the current density is increased stepwise at a rate of 0.2 A/dm ² /min or less during electrolysis from the start of electrolysis to a predetermined current density. A method for producing electrolytic manganese dioxide.