JP3183579B2 - How to process photographic wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste solution of a photographic bleach-fixing solution, a photographic bleaching solution and a photographic fixing solution (these are generically referred to as photographic processing solutions in this specification). More specifically, the present invention relates to a method for recovering silver from waste photographic processing liquid and a method for regenerating photographic processing waste liquid.

[0002]

2. Description of the Related Art Conventionally, various methods for recovering silver from waste photographic processing liquid, such as an electrolytic method, a precipitation method, and an ion exchange method, have been used. In the electrolysis method, the pH fluctuates due to the change in current density during the electrolysis operation and / or the decomposition of the liquid to be electrolyzed (photographic processing waste liquid), and as a result, sulfuration occurs both on the electrode plate and in the liquid to be electrolyzed. Silver had formed. Therefore, the purity of the recovered silver is impaired, and the electrolyzed solution after electrolysis (that is, after the recovery of silver) contains silver sulfide, so that it cannot be reused as a photographic processing solution. .

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to recover silver with high purity and to remove silver after recovering silver. It is an object of the present invention to provide a method for treating a photographic processing waste liquid which can reuse an electrolytic solution as it is as a photographic processing liquid.

[0004]

SUMMARY OF THE INVENTION A method for treating a photographic processing waste liquid according to the present invention comprises a PR (periodic reverse) method.
Electrolyzing photographic wastewater using pulse electrolysis,
At this time, the cathode reference (that is, the electrode on the side where silver is deposited) is used.
Characterized by more than the electrical quantity of the pulse on the positive side of the electric quantity of pulses pole for) the minus side.

In the processing method of the present invention, it is essential to use PR-pulse electrolysis, and to make the electric quantity of a pulse on the minus side of the cathode reference larger than the electric quantity of a pulse on the plus side in electrolysis. Requirements, but PR to use
-The pulse is a constant potential PR-even if the pulse is a constant current PR-
Pulses may be used, and other electrolysis conditions and the like may be conditions used in normal electrolysis, and may be a continuous type or a batch type. The treatment method of the present invention can be carried out, for example, under the following apparatus and conditions (in the present specification,
Negative value an electron for the current density (e ^-) is silver deposit
When flowing from the electrode into the liquid (that is, when silver is deposited)
Represents a positive value, electrons flow from the liquid to the silver deposition electrode
Denote the case): electrolyzer: Using a two-dimensional electrode electrolytic bath, the electrolytic cell using a three-dimensional bed electrode, rotating electrodes electrolyzer, PR- pulse applying time: negative side of the application time (t _- ): 0.1 to 900 msec,
Preferably 0.5 to 100 msec, plus application time (t ₊ ): 0.01 to 100 msec,
Preferably, 0.1 to 20 msec, PR-pulse period (sum of t _- and t ₊ ): 0.11 msec-
1 sec, preferably 0.6~120msec, PR- pulse current density: the negative current density _{(i -): - 5~-} 150mA / c
m ² , preferably −20 to −60 mA / cm ² , plus current density (i ₊ ): +0.5 to +50 mA / c
m ^2, preferably ^{+ 1~ + 30mA / cm 2,} PR- pulse potential (in SCE standard): negative _{(V -): - 300~-} 950mV, preferably -500~-940mV, positive (V ₊₎ : +50 to +1350 mV, preferably +100 to +1300 mV.

In the processing method of the present invention, as a method of making the electric quantity of the pulse on the negative side with respect to the cathode larger than the electric quantity of the pulse on the positive side, the current density of the pulse on the negative side and the electric current of the pulse on the positive side are used. Adjust the application time (t _- and t ₊ ) by making the absolute value of the density equal, or make the current time of the negative pulse larger than the absolute value of the current density of the positive pulse by making the application time equal. Or
Alternatively, there is a method of adjusting both the application time and the current density.

In the processing method of the present invention, since the PR-pulsed electrolysis is used, the silver deposited on the cathode plate becomes fine and dense particles and is deposited smoothly. The disturbance of the current density due to the concentration of the unique charges does not occur in the processing method of the present invention. That is, the increase in the precipitated silver particle diameter due to the depletion of ions near the electrode as occurred in the prior art can be prevented by the PR-pulse electrolysis used in the processing method of the present invention,
Furthermore, by using PR-pulse electrolysis, the generation of hydrogen at the cathode and the generation of oxygen at the anode can be extremely reduced, so that there is no fluctuation in pH, and thus there is no fluctuation in pH as in the prior art. The resulting formation of silver sulfide from thiosulfuric acid and silver salt can be prevented in the processing method of the present invention. That is, in the processing method of the present invention, side reactions other than the silver precipitation reaction can be suppressed. Such an action,
In order to achieve the effect more effectively, in the treatment method of the present invention, in the case of the constant potential PR-pulse electrolysis, the electric quantity of the negative pulse is 2 to 10 times the electric quantity of the positive pulse. In the case of constant current PR-pulse electrolysis, it is preferable that the electric quantity of the negative pulse be 2 to 700 times the electric quantity of the positive pulse. When it is out of this range, silver precipitated on the cathode plate becomes slightly coarse particles, and the smoothness of the surface of the precipitated silver tends to decrease.

[0008] In the processing method of the present invention, on the cathode plate,
Since the formation of silver sulfide, which tends to form on the anode plate and in the electrolyte solution, can be suppressed, the purity of the recovered silver is improved, and the electrolyte solution after the electrolytic treatment can be reused as a photographic processing solution as it is.

[0009]

【Example】

Examples 1-3 and Comparative Examples 1-2 Photobleaching and fixing waste solution (silver content about 8 g / l) was electrolyzed under the following conditions: Electrolyzer: Electrolyzer using two-dimensional electrode, Material of anode and cathode : platinum, mode of operation: batch operation, the operation time of 1 hour, PR- pulse applying time _(t -, t _+): As shown in Table 1 (the unit msec), use the constant potential PR- pulses, the constant potential ( (Based on SCE) (V ₋ , V ₊ ): As shown in Table 1 (unit: mV), the electrolytic deposit was subjected to ESCA analysis after electrolysis under the above conditions, and the result was as shown in Table 1 (unit: weight%). The XRD of the electrolytic deposit of Example 1 was as shown in FIG. The electrolysis solution after the electrolysis was filtered, but no filtration residue was observed (when silver sulfide was present, a black filtration residue was formed). That is, no silver sulfide was formed.

[0010]

[Table 1]

Examples 4-6 and Comparative Examples 3-4 Photobleaching and fixing waste solution (silver content about 8 g / l) was electrolyzed under the following conditions: Electrolyzer: Electrolyzer using two-dimensional electrode, working electrode material: SUS304, the counter electrode: platinum, mode of operation: batch operation, the operation time of 3 hours, PR- pulse applying time _(t -, t _+): as shown in Table 2 (in msec), the constant current PR- pulses using its PR- pulse current density _(i -, _{i +):} As shown in Table 2 (unit: mA / c
m ² ), ESCA analysis of the analysis product revealed the results shown in Table 2 (unit:% by weight). The electrolysis solution after the electrolysis was filtered, but no filtration residue was observed (when silver sulfide was present, a black filtration residue was formed). That is, no silver sulfide was formed.

[0012]

[Table 2]

[0013]

According to the processing method of the present invention, silver can be recovered with high purity, and the electrolyzed solution after recovery of silver can be reused as a photographic processing solution as it is.

[Brief description of the drawings]

FIG. 1 is an XRD of the electrolytic deposit of Example 1.

Continuation of the front page (56) References JP-A-3-141348 (JP, A) JP-A-49-119457 (JP, A) JP-A-60-1000069 (JP, A) JP-A-63-210291 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25C 1/00-7/08 G03C 5/00

Claims (3)

(57) [Claims] The present invention is characterized in that a photographic processing waste solution is subjected to electrolytic treatment using PR-pulse electrolysis, wherein the amount of electricity on the negative side with respect to the cathode is larger than the amount of electricity on the positive side. Of photographic processing wastewater. 2. Use of constant potential PR-pulse electrolysis.
2. The processing method according to claim 1, wherein the electric quantity of the pulse on the negative side with respect to the cathode is set to 2 to 10 times the electric quantity of the pulse on the positive side. 3. Use of constant current PR-pulse electrolysis,
2. The processing method according to claim 1, wherein the electric quantity of the pulse on the negative side with respect to the cathode is set to be 2 to 700 times the electric quantity of the pulse on the positive side.