JP2002079269A - Silver capturing agent, column for capturing, and silver capturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that a conventional method using EDTA is effective as a sliver capturing agent but causes a new environmental problem because EDTA is a hardly degradable substance. SOLUTION: A silver capturing agent consisting of an organic amino carboxylic acid having a biodegradability of >=60% is used for removing silver from a silver-containing solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for promoting desorption of silver from a photosensitive material during a desilvering step of photographic development, or contained in a waste liquid discharged from a photographic developing station, a plate making station, a printing station or a factory. Related to removing silver.

[0002]

2. Description of the Related Art In recent years, the standards for silver emission in sewers have become strict. For example, the standards for silver emissions in sewers in Europe are 0.1 ppm or less. In addition, from the viewpoints of the global environment and the protection of activated sludge and fish, the regulation of silver in wastewater has become strict. Conventional silver regulations have set the silver concentration in wastewater to 2 ppm or less. Silver concentration 0.2ppm or less, silver concentration 0.02p in some cases
pm or less.

Hitherto, as a method of trapping silver, a method of forming a silver complex insoluble in water and separating a precipitate formed by precipitation of the silver complex has been used.

[0004] For example, ethylenediaminetetraacetic acid (hereinafter referred to as EDTA) has been often used as a silver scavenger because of its high coordination ability with silver.

[0005]

However, this EDTA is poor in biodegradability by a biological treatment method represented by the activated sludge method. That is, when EDTA is used for silver recovery, it is difficult to detoxify the remaining EDTA.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that, when silver is recovered from a silver-containing solution, an organic aminocarboxylic acid having a biodegradation rate of 60% or more is obtained. It has been found that the use of an acid leads to a high silver removal rate, leading to the present invention.

[0007] That is, the present invention provides a method of recovering a silver comprising an organic aminocarboxylic acid having a biodegradation rate of 60% or more, a silver recovering agent having the organic aminocarboxylic acid supported on a carrier, and a container containing the recovered recovering agent. Silver Recovery Agent Column and Silver Recovery Method Using These Columns ".

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The biodegradation rate in the present invention is defined as the biodegradation rate represented by the following equation (1).

Degree of decomposition (%) = (BOD−B) / TOD × 100 (1) where, BOD: biochemical oxygen demand (measured value) of test substance (mg) B: activated sludge in basic culture medium Consumption (measured value) (mg) TOD: Theoretical oxygen demand (calculated value) (mg) required when the test substance is completely oxidized. Test method (Kanho No. 5 / Yakuhatsu No. 615/49 bureau No. 392)
No.) ".

[0010] The test method uses a closed system oxygen consumption measuring device, and A is defined by 16 (-) of JIS K0120.
Solution, solution B, solution C and solution D, each with 3 ml of water,
Liters.

Prepare the following test vessels and adjust them to the test temperature. If the test substance does not dissolve in water up to the test concentration, use finely pulverized material as much as possible. (1) A test container containing a basic culture medium containing 100 ppm (W / V) of the test substance. (2) A control empty test container containing only the basic culture medium. Test vessel containing 100 ppm (W / V) added aniline (4) Test vessel containing aniline added to base culture medium at 100 ppm (W / V) (1), (2) ) And JIS K0
The suspended substance concentration determined by 10, 2, 3 of 120 is 30
Inoculate activated sludge so that it becomes ppm (W / V).

Cultivation is carried out at 25 ± 1 ° C. for a fixed period of time (14 days in principle) with sufficient stirring, and changes in oxygen consumption are measured over time.

After culturing for a certain period, the remaining test substance is subjected to analysis, and its amount is measured. If the test substance dissolves in water, measure the residual amount of total organic carbon.

If the degree of degradation of aniline in (3) obtained from oxygen uptake does not exceed 40% after 7 days, this test is invalid.

The organic aminocarboxylic acid having a biodegradation rate of 60% or more includes, for example, picolinic acid, isonicotinic acid, methylpicolinic acid, pyridinedicarboxylic acid, aminonicotinic acid, pyrazinecarboxylic acid, methylpyrazinecarboxylic acid, quinaldic acid , Keridamic acid, citrazinic acid and the like, and more preferably, picolinic acid, 6-methylpicolinic acid, 2,6-pyridinedicarboxylic acid, quinaldic acid,
It is keridamic acid.

In the present invention, an organic aminocarboxylic acid may be bound to a carrier. There are organic and inorganic carriers, and examples of the inorganic carrier include porous silica gel, alumina, zeolite and montmorillonite. Organic carriers include natural and synthetic polymer carriers.Agarose, dextran, and particles made of polysaccharides such as cellulose as natural sources, and polystyrene, polyacrylamide, and the like as synthetic polymer carriers. There are particles that become.

When an organic aminocarboxylic acid is supported on these carriers, the surface of the carrier may be chemically modified and directly bonded to the carrier, or the carrier may serve as a spacer between the carrier and the organic aminocarboxylic acid. You may introduce something.

The carrier supporting the organic aminocarboxylic acid is
It is packed in a container such as a cylinder and can be used as a fixed-bed separation column. For example, two or more columns are arranged in parallel, while silver is captured, while another column desorbs silver and regenerates it, thereby continuously processing silver. Can also.

[0019]

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

The reagent used was a silver capture agent manufactured by Aldorich.
2,6-dipyridinecarboxylic acid, silver nitrate manufactured by Wako Pure Chemical Industries.

As a result of the biodegradation test, the biodegradation rate of 2,6-dipyridinecarboxylic acid was 82%.

Example 1 Silver nitrate was dissolved in 100 g of water so as to be 100 ppm in terms of silver. To this, 2,6-pyridinecarboxylic acid was added in a molar amount of 10 times the amount of silver, followed by stirring at 50 ° C. overnight.
After allowing the solution to stand, the silver concentration in the aqueous solution was 1 ppm.

[0023]

According to the present invention, an organic aminocarboxylic acid having a biodegradability of 60% or more acts as a silver scavenger from a silver-containing solution and can reduce the burden on the environment.

Claims (6)

[Claims] 1. A silver scavenger containing an organic aminocarboxylic acid having a biodegradability of 60% or more. 2. The silver scavenger according to claim 1, wherein the organic aminocarboxylic acid is an aromatic nitrogen-containing heterocyclic compound. 3. The silver scavenger according to claim 1, wherein the carboxyl group of the organic aminocarboxylic acid is on carbon next to the nitrogen atom. 4. The silver scavenger according to claim 1, wherein the organic aminocarboxylic acid is carried on a carrier. 5. A silver capturing column, wherein the container is filled with the silver capturing agent according to claim 4. 6. A method for capturing silver, comprising contacting a silver-containing solution with the column according to claim 5 to remove silver.