Process for recovery of silver from spent, waste, acidic processing fluids

[Detailed Description of the Invention]

The present invention relates to how to have been improved from the waste treating solution for acid photographs for collecting silver. The present invention relates also to the device for collecting silver from the waste treating solution for acid photographs. It is publicly known to collect silver from the used treating solution for photographs. The thing of the 1st place is what is called "fixing" liquid about a treating solution with high silver concentration. Since a picture "is fixed", this solution is used in order to be eluted in the unexposed part of the element for photographs, i.e., the silver halide of a non-developing section. Since acetic acid exists, a fixing solution is usually acidity. Since silver is important resources and is expensive, many methods of collecting silver are developed. Two fundamental systems are contained in these methods, and one is using the chemical substitution depended on the base metal of a price with the low 2nd, i.e., the metal in which an electrochemical series is higher than silver, with regards to the electrolysis method. Any system has an advantage and a disadvantageous point. The system of electrolysis consumes electric power, and is too expensive, and is not efficient about the discharge liquid containing 200 ppm or the silver beyond it. A chemical substitution system is not generally efficient, either. In addition, by there being a tendency which makes precipitation of the detailed black solid in which both systems are known as "black sludge", this blocks a system, or is delayed, and the liquid containing much silver is made to bypass and Lost from a system. This loss and Natsumata produce it being not only a disadvantage on economy but a pollution problem, and are inconvenient environmentally. Then, it is still efficient and more economical and how for the environment top to also have been improved for collecting silver from the convenient waste treating solution for acid photographs is needed. In the method of according to the present invention passing a waste treating solution through the iron which was stored in the container and which was divided minutely, and collecting the liquid which does not contain the dissolved silver substantially, it is the above-mentioned container, The silver recovering method from the used silver halide waste treating solution for acid photographs which consists of the metal salt chosen from the group which consists of copper and cadmium being included in small quantities to the iron divided minutely is provided. According to other viewpoints of the present invention A -- the container made from a stable material to the treating solution and; which have an even bottom and an upper lid Sole plate arranged at the above-mentioned container bottom which can distribute a treating solution through the inside of the B above-mentioned container so that a treating solution may flow uniformly; Iron which is filling the C above-mentioned container substantially at least and which was divided minutely; an entrance pipe and an outlet pipe are arranged at the D above-mentioned container -- a treating solution -- the above-mentioned entrance pipe -- a connoisseur -- flowing into the ON intermediary above-mentioned sole plate lower part into an intermediary container and the above-mentioned outlet pipe -- a connoisseur -- in the device it was made to flow through the iron divided minutely before carrying out intermediary discharge Before pouring a treating solution through the above-mentioned container, the used silver recovery subsystem from the silver halide waste treating solution for acid photographs which consists of a small quantity of the metal salt chosen from the group which consists of copper and cadmium existing to the iron divided minutely in the above-mentioned container is provided. Container 1 has even bottom 2 and upper lid 3 which can be removed as shown in Drawing 1 showing the vertical section of the silver recovery subsystem of a desirable mode. By another method, in order to remove, upper lid 3 can also adhere to container 1 so that it may cut off. there is sole plate 4 by which the hole was dug preferably in the bottom of container 1 -- this board -- entrance pipe 5 -- a connoisseur -- intermediary container 1 can be made to have distributed the silver halide waste treating solution for acid photographs of Used since an ON intermediary The inside of the container on this board 4 is substantially filled with iron 6 like the form of steel wool distributed minutely at least, for example. In order to remove a Noodle treating solution excluding silver substantially in container 1, there is outlet pipe 7 in a container. Although copper or cadmium metal salt 8 can also be made to exist as solution like a dry state or solution, generally it is arranged at the place under sole plate 4, and is made to exist in container 1. Although the specification of this device can be changed, in order to collect the silver of a quantity substantial at least from a used photograph waste treating solution, a treating solution enters into a container and can fully contact iron and metal salt which were divided minutely [ before being discharged from a container ]. This device can be used as a part of automatic processing unit. For example, a plurality of devices beyond five pieces or it are also used by request. A treating solution flows into one device of the above-mentioned form, and flows continuously through a series of similar devices with a pump means, gravity, etc. After leaving the last device, the treating solution can also pass the silver detector which measures the silver which remains in it. An automatic processing unit is exchanged as that from which the recovery subsystem of one piece or some collected sufficient silver. Container 1, sole plate 4, entrance pipe 5, and outlet pipe 7 are made from a stable material to the acid silver halide waste treating solution for photographs. Although the stable plastic of material is preferred, the material of others which were known by the person skilled in the art can also be used including metal. As explained above, iron 6 divided minutely is a form of steel wool preferably. The net of a Woven steel line, the rounded steel line, etc. can be used. In the upper part of sole plate 4, a container is essentially preferably filled with iron 6 divided minutely. A small quantity exists in the bottom of container 1 of the sole plate 4 lower part to iron 6 in which metal salt 8 of either the shape of a solid or the shape of solution was divided minutely. Other copper, cadmium salt, etc. are contained in the metal salt accepted to be effective in combination with the iron divided minutely at a copper sulfate and copper chloride ()2 water ghost, cadmium sulfate, and the appearance. For example, since Copper salt like a copper sulfate 5 water ghost has these cheap, it is the most preferred. The negative ion portion of salt is not important to an actual effect. The range of the rate of metal salt to the iron divided minutely is 25:1~4:1 by weight. Although it does not limit, 500g ~ 2500 g of metal salt is combined with ~10886g (24 pounds) of the iron divided minutely as an example. A desirable quantity of a copper sulfate 5 water ghost is 1000g to ~10886g (24 pounds) steel wool. Existence of acetic acid or sulfuric acid, an acetic acid mixture, etc. lets the used silver halide waste treating solution for photographs which is acidity pass in container 1 through entrance pipe 5 when carrying out the present invention, Thereby, a treating solution flows into the field of the container of the sole plate 4 lower part in which the hole is dug preferably, first, it distributes equally on metal salt 8, and a treating solution is raised through iron 6 subsequently divided minutely. continuing -- a treating solution -- outlet pipe 7 -- a connoisseur -- it comes out of an intermediary device. Time for a treating solution to pass a device is influenced by variables, such as concentration of silver, a size of a recovery subsystem, and the passage flow velocity. By analyzing the silver in outflow liquid, holding time is determined best and changes broadly there. In this stage, the substantially dissolved silver of a treating solution is lost, and it can be discarded safely economically and environmentally. The conventional silver recovery subsystem did not use metal salt by the present invention, therefore these devices were not efficient. After use, it adds to the dry content of a device with 30~70% of silver conventionally at it, and a lot of black sludge is contained. For example, adding metal salt like copper sulfate will improve the usefulness of a device by decreasing black sludge and other harmful by-products by raising a silver analytical value more than 90% or it. In addition, use of metal salt holds the structure in early stages of iron like steel wool divided minutely, prevents a jam and channeling by this, inhibits a side reaction, and strengthens that iron changes to silver. Thus, the method of the present invention and silver recovery were completed, and economically, the above-mentioned improvement that an environment top could also perform abandonment of a treating solution safely was not conventionally indicated in literature, either, and prediction was not completed from the conventional knowledge, either. The desirable mode of the present invention is shown in Example 1. The present invention by copper and cadmium metal salt existing provides how to have been improved for collecting silver from the acidic solution of others containing a thing like the used silver halide waste treating solution for acid photographs, for example, a fixing solution, and similarly dissolved silver. Typically, these solution contains comparatively a lot of acetic acid, thiosulfate salt, sulfite salt, bromides, sodium salt, some tetra thionic acid salt, etc. Existence of comparatively a small amount of metal salt in a silver recovery subsystem improves the usefulness of silver recovery wonderfully by it not only decreasing the amount of generation of the harmful by-product of others besides black sludge, but having accepted increasing a silver analytical value more than 90% or it by weight. an early structure thru/or form of iron like steel wool divided minutely is maintained -- therefore, channeling -- getting it blocked -- Be avoided. This method and device can suit easily in an automatic processing unit. The exposed element for photographs is sent into these processing units, and it is carried to a developing solution, a flush, a fixing solution, and a water washing bath through many rollers and similar means, and it succeeds to a film and it is dried automatically. A fresh developing solution and fixing solution (replenisher) are usually added at a rate decided with the finished film, and used solution is taken out simultaneously. It is this solution that the present invention considered as the object originally including the silver halide in which the highest quantity dissolved the used fixing solution which is essentially acidity. This waste fluid contains a lot of silver, and since silver is expensive, to collect these silver in the purest possible form is desired economically. In addition, discarding the solution which contains a lot of [ in this way ] dissolved silver in it is that it is not desirable environmentally. In fact, it is usually illegal to discard this useless article to an ordinary useless article institution. Then, there is the serious necessity of collecting these dissolved silver. The present invention solves this problem by a suitable and effective method. EXAMPLE Although the present invention is explained below, it is not limited to this. Percent is based on weight in each example. Example 1 The silver recovery cylinder which can be obtained in a market is used, and it is I got it about the various tests of the present invention method. These systems are the pipes (Kodak type 3) of 56.781 (15 gallons) which stored 10.89 kg (24 pounds) of commercial class steel wool of the doughnut form at 38.1 cm (15 inches) in height. Some of this pipe was used in this example. The 1st (contrast) thing was used, purchased. CuSO of the quantity of versatility [ things / other ]₄·5H₂O was added. The flow of the used silver halide fixing solution for photographs poured through this pipe is after [ 37.85 (10 gallons) ] used fixing per hour, and, typically, this liquid contains 5400 ppm dissolved silver as thiosulfuric acid complex ion. Completion of a displacement reaction and consumption of effective iron in the pipe by it were investigated by monitoring the quantity of the silver in outflow liquid by an atomic absorption spectroscopic method. The capacity of the used pipe was proportional to the amount used. Due to the control test using steel wool (contrast) as it is, doughnut form steel wool with a height [ first ] of 38.1 cm (15 inches) collapses in the lump of the mixture of black sludge about 2.7 cm (5 inches) high and a silver fibril, The high value and Noodle which the value of the silver flowing out begins to increase and are hard to accept. A typical yield is 13.15 kg (29 pounds) of dry articles [ about 9.2 kg (20.3 pounds) of ], i.e., recovery silver, containing about 70% of silver, and is Oh. What added a 1000-g copper sulfate 5 water ghost to the pipe as a dry solid before introducing, the pipe, i.e., the used fixing solution, of the present invention, :A which gave the following results About 12.7~13.15 kg (28~29 pounds) of 13.6~14.06 kg (30~31 pounds) dry articles, i.e., recovery silver, containing 90~95% of pure silver were obtained. Black sludge is not included in B essence target. Doughnut form steel wool with a start height of 38.1 cm (15 inches) of C became small at about 5.08~7.62 cm (2~3 inches), and comprised a fibril of the silver in which the same structure as the first doughnut form steel wool shone. That is, silver has been collected easily. Use of the pipe containing D steel wool and copper sulfate was remarkably extended compared with the time of the pipe of contrast. Even if the silver made from the improved method does not pass through the interim process needed about the contrasting method, although refined for silver real value to be reproduced, it is pure enough. Example 2 A copper chloride ()2 water ghost is used in a quantity almost equal to the copper () ion concentration supplied by the copper sulfate ()5 water ghost, and a test is done, It was added by steel wool as a dry solid, and as Example 1 subsequently described, when a used photograph fixing solution was poured out, it was accepted that an equivalent improvement is substantially obtained in silver adherence efficiency. 5.0 g of steel wool was put in the 130-ml beaker made from a plastic, and the suitable salt shown below was added.

[Table]

100 g of the used photograph fixing solution which contains 3600 ppm silver in the form of thiosulfuric acid negative ion complex salt was added to this mixture. The mixture was held on the order oscillating device for 1.5 hours at the contact state. The fixing solution was succeeded to it and discharged and analysis of silver was made the atomic absorption spectroscope using the standard technique. The 2nd fixing solution was added, and this method was repeated, without further adding Copper salt. Similarly, the 3rd fixing solution was added. The silver ion analysis result of discharge liquid is shown below.

[Table]

The recovery nature of the silver in which any salt is almost equivalent was shown. In both cases, it is structurally the same, is only that solution is transparent and the generation of black precipitation which black sludge is little and was finely distributed by being colorless and covering Then and steel wool uniformly with shining silver, and is Oh. The contrast only using steel wool of silver removal is effective, black sludge is contained, Oh (namely, an average of 10.2 ppm) has black discharge liquid, and steel wool collapsed structurally. Example 3 It is I got it about a series of tests similar to having described the above-mentioned Example 2. 5.0 g of steel wool by which the solid salt of various cations was added was continuously contacted to 100 g of the used photograph fixing solution containing 3600 ppm silver complex salt 3 times. The method described in the above-mentioned Example 2 was used. The result of this series is shown all over the following table [ 1st ].

[Table]

(1) Contrast showed collapse of black discharge liquid, a lot of black sludge, and steel wool. (2) The deposition of silver and the black sludge of tolerance level which have brightness on water-white discharge liquid and the steel wool of the same form were shown. (3) Some muddiness and collapse of some steel wool were shown in deposition of a dim metal and discharge liquid. (4) Deposition of transparent discharge liquid and the metal which has brightness without structural modification of steel wool, and a little black sludge were shown. (5) It is the same as the above (1). (6) The black sludge of yellow-green discharge liquid, deposition of metal with some brightness, a minute collapse of steel wool, and some was shown. (7) Although discharge liquid was transparent, black sludge quite larger than the above (2) was shown. (8) Collapse of some of the transparent discharge liquid accompanied by generation of some black sludge and steel wool was shown. (9) It is the same as the above (4). This example shows that only copper and cadmium salt are useful among various metal salt although sufficient silver is removed from discharge liquid, without being accompanied by other inconvenient points. Example 4 It is I got it about a series of experiments in order to decide the optimum amount of the copper sulfate ()5 water ghost added to steel wool. As for the fixing solution, four addition was adopted although the same laboratory procedure as having described Example 2 was used in this example. Other experimental conditions contacted the 100-ml fixing solution for used photographs and 5.0 g of steel wool which contain 5400 ppm silver as soluble complex salt on the oscillating device for 1.5 hours. The result of these tests is shown all over the following table [ 2nd ].

[Table]

[Table]

By this test, giving a result with 300 mg of optimal salt was accepted.

[Brief Description of the Drawings]

Drawing 1 is the vertical cross section passing through the center of 1 example device of the silver recovery subsystem of the present invention. 1 ... container, 2 ... bottom, 3 ... top lid, 4 ... sole plate, 5 ... entrance pipe, 6 ... outlet pipe, 7 ... outlet pipe, 8 ... metal salt.