JPS5953336B2 - Method for recovering silver and film base from photographic film using microorganisms - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering silver and film base from photographic film.

With the development of microfilm and magnetic tape technology for storage reasons, the amount of photographed medical X-ray film that is discarded will continue to increase. Therefore, if it were possible to recover silver and film base from these discarded photographic films, it would be extremely effective in terms of resource conservation and pollution control, and the present invention is considered to have high value. Conventionally, methods of recovering silver on the film surface include an ashing method and a method of treatment with high concentration sodium hydroxide.

Among these methods, the ashing method produces unpleasant odors and dust, and it is impossible to recover the film base. on the other hand,
The method using high concentration sodium hydroxide involves alkaline wastewater, and various additives are mixed into the gelatin membrane to improve film performance, so it is not possible to separate only silver by filtration. It's becoming possible.

Furthermore, recovery of the film base is not planned in the first place and is completely impossible. The present invention eliminates the drawbacks of these methods and uses microbial reactions without secondary pollution to recover the silver on the film surface, and also to recover the silver in a recyclable state without damaging the film base. This is what we are trying to recover.

Ding The method of the present invention will be explained below.

The present invention uses aerobic or anaerobic microorganisms that decompose organic substances such as proteins, starches, fats and oils, and cellulose, especially mixed microorganisms containing gelatin-active mutant bacteria that have activated gelatin-feeding bacteria that use gelatin as a nutritional source. It is used to decompose the gelatin membrane of the film. In addition, this gelatin-eating bacteria is a bacteria that prefers to eat organic gelatin and excretes inorganic silver from the body without taking it into the body, and gelatin-active mutant bacteria is a bacteria that prefers to eat gelatin, which is an organic substance, and excretes inorganic silver from the body without taking it into the body. line, γ
Bacteria that have been artificially mutated and activated by irradiation with radiation, ultraviolet light, etc. Generally, when aerobic bacteria are used, gelatin is biologically decomposed by the reaction of anaerobic bacteria.

Therefore, by exposing the film to a liquid or gas containing these microorganisms, silver can be recovered from the film surface. Furthermore, since Mylar film is not decomposed by these bacteria, it can be recovered without damaging the film base, and this film base can be used again. The microorganism of this invention is mainly composed of gelatin-feeding bacteria, and in addition, protozoa, bacteria, and other miscellaneous bacteria are mixed in.
Their ability to survive is strong and durable, and biological activities such as metabolism, growth, and proliferation are carried out even under harsh conditions.
Effective in terms of management.

゛In order to decompose gelatin films efficiently and in a short time, it is necessary to warm the film to soften it, make it hydrophilic, and provide nutrients (nitrogen, phosphorus, minerals) for microorganisms. etc.) is desirable.

In addition, the microorganisms to be used may be any bacteria that can decompose proteins, starches, fats and oils, cellulose, etc. as mentioned above, but in order to process them in a shorter time. For this purpose, it is desirable to use those with high decomposition ability. For this reason, Honkamei uses gelatin-feeding bacteria that prefer to eat gelatin on the surface of photographic film, and in addition to these bacteria, protozoa, bacteria, and other contaminants are added to ensure strong survival even under adverse conditions. We took microorganisms mixed with 5 and added high-level radiation such as X-rays, α-rays, γ-rays, and ultraviolet rays to them in order to dramatically shorten the processing time that previously took a long time and improve work efficiency. It uses gelatin-active mutant bacteria that have been artificially mutated by irradiation with special energy-imparting radiation. Through such treatment, as described in the example below, gelatin membranes can be completely decomposed in about 5 minutes, compared to several days or hours when using normal bacteria that are not mutant bacteria with gelatin activity. I made it possible to do so.

Silver can be easily separated from the film base by any of the natural sedimentation method, vibration separation method, and mechanical separation method (spray method, scraping method).

The silver to be separated is in the form of black fine powder, and it is possible to directly obtain fine powder silver by centrifugation, and it is also possible to obtain high purity silver by simple electrolytic treatment.
Note that one of the features of this method is that the treated liquid containing microorganisms does not cause any harm even if it is directly drained or drained.

A typical example of the specific procedure of this method when using anaerobic microorganisms is shown below.

First step (hot water treatment step) The film is immersed in a 1% aqueous sodium phosphate solution at 80 to 90° C. for 2 minutes.

Purpose 1. Soften gelatin with heat 2. 3. Gives hydrophilicity to gelatin. 2nd step of providing nutrients (gelatin membrane decomposition step) Immerse in a solution containing microorganisms for 5 to 10 minutes (temperature 35
℃) Purpose 3rd step of decomposing the gelatin layer (silver film base separation step) Separate the silver from the film base in water using a vibration method, mechanical method, etc. (1) About the silver This separated silver is in the form of black fine powder. doing.

(1)-1 As a chemical method A. (Fourth step) 0.4N nitric acid solution.

B. (Fifth step) Electrolyze. For example, cathode potential +0.4V
VSS. C. E voltage between electrodes 1.5 to 1.4V C. Recovery of 99% pure silver (1)-2 Physical method A. Dehydration by centrifugation etc. B. Recovery of finely divided silver (2) Regarding the film base (4th step) Immerse in 1% sodium hypochlorite solution.

eyes Sterilize (5th step) washing with water The film base is thus recovered.

When using aerobic bacteria, almost the same treatment may be performed in the air.

Hereinafter, the usefulness of the present invention will be explained while showing comparative examples and examples.

Comparative example 1. Commercially available bacteria (trade name: Clean Team, Toyo Clean Co., Ltd.), which is one of the normal bacteria that is not a gelatin-activating mutant.
A photographic film was immersed in the suspension (35° C.) for 15 minutes, taken out into distilled water, and irradiated with ultrasonic waves for 2 minutes to separate the silver.

With this bacterium, only a portion (approximately 10%) of silver could be separated as shown in Figure 1. Example 1. As a gelatin-active mutant strain, Perfect Clean (trade name, manufactured by Suiri Co., Ltd.) was used. Photographic film was immersed in a 1% suspension of this at 35°C for 15 minutes, and then taken out into distilled water for 2 minutes. The silver was separated by ultrasonic irradiation.

As shown in Figure 2, most of the silver (approximately 99%) could be separated. Example 2. It has been found that processing time can be shortened by immersing the film in hot water in advance to soften the gelatin layer and then allowing it to be decomposed by microorganisms.

A hot water-treated film was immersed in the solution used in Example 1, and then irradiated with ultrasonic waves for 2 minutes to separate silver. In Figure 3, hot water treatment and Perfect Clean treatment are performed for 1 minute, 5 minutes in (1), 5 minutes, 5 minutes in (2), and 3 minutes in (2).
) for 1 minute and 10 minutes, and (4) for 5 minutes and 10 minutes, the silver separation was about 20%, 50%, 95%, respectively.
It was 100%. In addition, the hot water treatment was performed at 80% as described above.
It was carried out in a 1% aqueous sodium phosphate solution at ~90°C. By using this aqueous solution, compared to simple hot water treatment, it was possible to impart hydrophilicity to gelatin in a shorter time and at the same time provide nutrients to the gelatin-active mutant bacteria, thereby promoting the activation of the mutant bacteria. . This hot water treatment using an aqueous solution is one of the factors that made it possible to achieve the short-time treatment required for industrial treatment. Example 3. In order to confirm the decomposition time of the gelatin layer, temporal changes in the amount of ammonia ions, which are decomposition products, were measured.

When the amount of ammonia ions was measured during the experiment described in Example 2, the results were as shown in FIG. As is clear from this, it can be seen that it is decomposed in about 10 minutes. In addition,
If the silver is separated by ultrasonic irradiation at the same time as the microorganism treatment, the action of suppressing activation will be reduced because the microorganisms are silver, and the processing time will be about half that, about 5 minutes. It was also confirmed that it is possible.

[Brief explanation of the drawing]

Figure 1 shows an X-ray film treated with Clean Team, which is a normal bacteria that does not have a gelatin activity mutant, and Figure 2 shows a film treated with PerfectClean, which is a gelatin activity mutant. Figure 3 is a diagram of perfect clean treatment after hot water treatment, and the hot water treatment and perfect clean treatment times are (1
) is 1 minute and 5 minutes, (2) is 5 minutes and 5 minutes, (3) is 1 minute and 10 minutes, and (4) is 5 minutes and 10 minutes. The figure also shows the decomposition rate of gelatin in X-ray film when PerfectClean is used. In addition, a... The part where silver is attached before treatment,
b... Shows the surface of the film after silver peeling.

Claims (1)

[Claims] 1 Photographic film is immersed in a 1% sodium phosphate aqueous solution at 80 to 90°C and treated with hot water, and the hot water-treated film is aerobic or anaerobic and contains a gelatin-active mutant bacteria. A photographic film using microorganisms, which is characterized by decomposing the gelatin film of the film by exposing it to a mist or liquid containing microorganisms, and further separating silver and the film base from the film with the gelatin film decomposed. How to recover more silver and film base.