JPH02159326A - Method for recovering silver component - Google Patents

Abstract

PURPOSE:To continuously and stably recover silver components even if the concn. and kind of the components are changed by adding the three kinds ot high molecular flocculants, namely the condensate-type cationic, polymerizate- type cationic, and anionic flocculants, to the water contg. the silver components. CONSTITUTION:The condensate-type cationic high molecular flocculant, the polymerizate-type cationic high molecular flocculant, and the anionic high molecular flocculant are added to the water contg. silver components. The kind, addition rate, adding order, and agitation of the flocculants are appropriately specified, and treatment is carried out. The silver components are flocculated by the treatment, separated, and recovered. The method can be applied to a wide range of pH.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a recovery method for recovering silver components from silver component-containing water generated during the production of photosensitive materials, photoengraving, silver plating, silver alloys, etc. It is something.

<Prior art> Drainage generated during the production of photosensitive materials, photoengraving, silver plating, silver alloys, etc. contains various silver components such as silver salts, silver compounds, and colloidal particles. When recovering silver components from water containing silver components, conventionally, the silver components are separated into solid-liquid by centrifuging the water containing silver components, or by adding a foaming agent to the water and flotation separation. method is being done. In addition, an inorganic flocculant such as an aluminum salt or iron salt and an anionic polymer flocculant are added to the water contained, or after adjusting the pH to the acidic side, a polymeric cationic polymer flocculant and an anionic polymer flocculant are added to the water. A method has also been proposed in which the silver component is agglomerated by adding silver, the agglomerates are separated into solid and liquid, and then the sludge of the agglomerates is dehydrated.

Among the conventional collection methods mentioned above, the centrifugation method has a particle size of 0.5 μm.
The following silver components have the drawback that it is difficult to separate and recover them, and the recovery rate of the silver component depends on the particle size of the silver component.

Furthermore, the flotation separation method has the disadvantage that depending on the type of silver component, it may not be possible to float it even if a foaming agent is added, resulting in a low recovery rate. Furthermore, in the treatment method of adding an inorganic flocculant and an anionic polymer flocculant, aluminum, iron, etc. caused by the added inorganic flocculant coexist in the dehydrated silver component-containing sludge, making it difficult to purify silver. However, it has the disadvantage of requiring high costs for refining. Also I)
The treatment method in which a polymeric cationic polymer flocculant and an anionic polymer flocculant are added after adjusting H to the acidic side not only fails to capture fine silver components and has a low silver component recovery rate, but also results in solid-liquid Dewatering treatment is difficult because the separated silver component-containing sludge has poor strength and dewatering properties. In addition, due to the low processing pH, corrosion of equipment and types occurs, and the dehydration filtrate pH
The drawback is that it requires neutralization treatment.

Furthermore, the treatment methods using the above-mentioned flocculants have the following drawbacks.

In other words, if the silver component combines with gelatin to form a protective colloid, it is difficult to agglomerate it as it is, so it is necessary to add enzymes to break down the gelatin before performing the aggregation treatment. However, it has the disadvantage that not only the operation becomes complicated but also the processing cost increases.

In addition, a common drawback of each of the above-mentioned processing methods is that if the concentration of silver components or the type of silver components changes significantly, it becomes difficult to follow these changes, and it is difficult to recover the silver components during continuous processing. The problem is that the rate varies greatly.

<Problems to be Solved by the Invention> The present invention solves the above-mentioned drawbacks of the prior art, recovers as much silver as possible from silver-containing water, and eliminates large changes in the concentration and type of silver components. However, it does not affect the recovery rate, and it is easy to purify the recovered silver.
It can be processed without acidic acid corrosion or neutralization of dehydrated filtrate, and even if the silver component is combined with gelatin to form a protective colloid, enzymes etc. can be added. The object of the present invention is to provide a method for recovering silver components that can be effectively recovered without causing any damage.

<Means for Solving the Problems> The method of recovering silver components from silver component-containing water according to the present invention, which has been made in order to realize the above object, is a method of recovering silver components from silver component-containing water by adding a condensation type cationic polymer flocculant and polymerization to silver component-containing water. The method is characterized in that silver components are recovered from silver component-containing water by adding a cationic polymer flocculant and an anionic polymer flocculant.

<Effect> The present invention will be explained in more detail below.

Water containing silver components is discharged from various processes, and the remaining silver components are generally recovered by some method and reused as necessary. In this case, important technical issues are how to efficiently recover the remaining silver component, as well as how to efficiently dehydrate and purify it.

However, silver-containing water usually also contains many chemical substances such as surfactants, emulsifiers, and bleaching agents.
Furthermore, as mentioned above, there is also a silver component that forms a protective colloid with gelatin, so it is not easy to efficiently extract the silver component from among them.

The present inventors investigated methods for efficiently recovering silver components from silver component-containing water using various flocculants, solid-liquid separation devices, and dehydration devices, and as a result, discovered a treatment method with extremely high treatment effects.

That is, three types of polymer flocculants, a condensed cationic polymer flocculant, a polymerized cationic polymer flocculant, and an anionic polymer flocculant, are added to silver component-containing water to flocculate the silver component. It separates solid and liquid.

In addition, according to the present invention using the above three types of polymer flocculants,
The silver component that has formed a protective colloid with the gelatin described above can also be aggregated as a protective colloid to form coarse particles that can be separated into solid and liquid.

In the present invention, the above three types of flocculants are added to silver component-containing water to flocculate silver components in various forms, and the aggregates are separated and recovered. Among the three types of flocculants, If even one of them is missing, the object of the present invention cannot be achieved.

For example, when only a clamp-type cationic polymer flocculant is added, not only does the amount of flocculant used increase significantly, but the flocs (hereinafter referred to as flocs) become finer. In case of separation, the sedimentation rate is slow and the capacity of the sedimentation tank must be considerably large.

Further, even when two types of flocculants, a condensation type cationic polymer flocculant and an anionic polymer flocculant, are added, the flocs do not become coarse and as a result, a sufficient recovery rate of the silver component cannot be obtained.

In addition, when only a polymeric cationic polymer flocculant is added, although the flocs produced become coarse, the silver components contained in the flocs are small.In other words, silver components that cannot be flocculated remain, resulting in A sufficient recovery rate of silver components cannot be obtained.

Furthermore, when two types of flocculants, a polymerized cationic polymer flocculant and an anionic polymer flocculant, are added, the flocs produced become rubber-like, making it difficult to dehydrate the flocs.

In addition, if two types of flocculants, a condensed cationic polymer flocculant and a polymerized cationic polymer flocculant, are added and an anionic polymer flocculant is not used, the floc strength will not be sufficient and the dewatering process will be hindered. At the same time, a sufficient recovery rate of the silver component cannot be obtained.

Note that when only an anionic polymer flocculant is added to silver-containing water, the aggregation effect of the silver component itself does not occur.

Therefore, in order to add a polymer flocculant to silver component-containing water to flocculate and efficiently separate the silver component, it is essential to add the three types of polymer flocculants described above.

In addition, by adding the three types of polymer flocculants mentioned above to flocculate the silver components, even if the properties of the silver component-containing water to be treated change, that is, the concentration of the silver component or the type of the silver component. Can be processed continuously and stably.

In addition, in the present invention, the typical order in which the three types of polymer flocculants are added to silver component-containing water is a condensed cationic polymer flocculant (a), a polymerized cationic polymer flocculant (b), and a.
When the anionic polymer flocculant is C, it is as follows.

B, Addition of C - Stirring - Addition - Stirring - Addition of C - Stirring port, b
Addition → Stirring - Addition of C - Stirring - Addition of C - Stirring c, a, b simultaneous addition - Stirring - Addition of C - Stirring 2, Addition of a → Stirring - Addition of C - Stirring 1 Addition - Stirring E, Addition of b - Stirring - Addition of C - Stirring -> Addition of a - Stirring Adding a condensation type cationic polymer flocculant, a polymerization type cationic polymer flocculant, and an anionic polymer flocculant at the same time is a cationic polymer flocculant and anionic polymer flocculant. This is undesirable because it will react with the polymeric flocculant and will no longer participate in the flocculation reaction, and it is also undesirable to add the anionic polymeric flocculant to silver component-containing water first because it will reduce the flocculating effect. However, depending on the type of anionic polymer flocculant, it may be possible to adopt it.

The three types of polymer flocculants used in the present invention will be explained in more detail below. First, the condensation type cationic polymer flocculants include polyalkylene polyamine condensates, polyamine-
Use polyamine-based flocculants such as epichlorohydrin condensates, epichlorohydrin-ethyleneimine condensates, and polyethyleneimine, amine-formaldehyde condensates such as aniline-formaldehyde condensates, dicyandiamide-formaldehyde condensates, and urea-guanidine formaldehyde condensates. Can be done.

Further, as the polymerizable cationic polymer flocculant, polyaminoalkyl acrylate, cationic modified polyacrylamide, polyvinylimidazole, chitosan, etc. can be used, and the colloid equivalent value is +3.0 m e g
/g or more is preferable.

Further, as the anionic polymer flocculant, a partially hydrolyzed product of polyacrylamide, a copolymer of sodium acrylate and acrylamide, a sodium polyacrylate, and a sulfonated product of polyacrylamide can be used.

In order to eliminate the viscosity of the flocs, it is preferable to use sodium polyacrylate and another anionic polymer flocculant together as the anionic polymer flocculant.

The present invention adds the three types of polymer flocculants mentioned above to flocculate the silver component and separate the flocs.
The optimal type of each polymer flocculant, its optimal addition rate, and optimal stirring conditions were determined by conducting a jar test by varying the type of flocculant, addition rate, and stirring conditions, and determining the floc diameter, floc strength, and floc sedimentation. It is determined from the speed, silver concentration of supernatant water, C3T value of supernatant water, etc.

Next, to explain the aggregation pH of the present invention, the above-mentioned 3
By using different types of flocculants, it is possible to effectively flocculate silver components from acidity to alkalinity.Therefore, two types of flocculants, the polymerized cationic polymer flocculant and anionic polymer flocculant mentioned above, are added. There is no need to make the pH particularly acidic, unlike in conventional treatment methods.

In addition, in the present invention, since the pH range at which aggregation is possible is wide, aggregation treatment can be performed at the pH of the silver-containing water itself, and there is also the advantage that a neutralizing agent to make it acidic or alkaline is not required.

The present invention adds the above-mentioned three types of flocculants to silver-containing water to flocculate the silver component and separate the flocs,
In some cases, the flocs may be separated by adding the flocculant to cause flocculation, and then directly separating the flocs using various filtration devices such as ceramic filtration devices, hollow fiber membrane filtration devices, and rotary suction filtration devices. Especially when the flocs have high strength and low viscosity, the flocs can be separated using a vibrating screen.

It is also suitably used to agglomerate the silver component to obtain flocs, and then concentrate the flocs in a flotation separator or coagulation-sedimentation apparatus to form a sludge.

For example, if the floc contains air bubbles and a light floc can be obtained, a flotation separator may be used, and if the floc has a large density and particle size and has good sedimentation properties, a coagulation-sedimentation device may be used.

In addition, when obtaining a dehydrated cake by dewatering silver-containing sludge obtained in a flotation separator or coagulation-sedimentation device, any of the screw type dehydrators, centrifugal dehydrators, belt type dehydrators, etc. may be used, and the properties of the silver-containing sludge Use depending on the situation. In the range of experiments conducted by the inventors, the screw type dehydrator has a throughput of
Although the moisture content of the dehydrated cake and the recovery rate of silver components were excellent, the present invention is not limited thereto. Metallic silver can be efficiently recovered by purifying this dehydrated cake containing silver components by heat treatment at, for example, 500-1,000°C.

As explained above, according to the present invention, even if the concentration of silver components and the type of silver components change greatly, the recovery rate is not affected and silver components can be efficiently, reliably, and continuously removed from silver-containing water. It can be recovered.

In addition, since the present invention does not use an inorganic flocculant, it is easy to purify silver, and furthermore, the silver component can be effectively flocculated without making the pH particularly acidic, so acid corrosion of equipment and types does not occur. There are various effects, such as eliminating the need to consider neutralization of the dehydrated filtrate.

In addition, the silver component that has formed a protective colloid with gelatin can be aggregated as a protective colloid without adding enzymes to decompose it, so the conventional process of adding enzymes can be omitted. processing operations can be simplified.

The present invention will be described in detail below, but the present invention is not limited to the following examples.

Examples Using silver component-containing water having the composition shown in Table 1 which is discharged in the process of producing photographic light-sensitive materials, conventional agglomeration methods and comparative examples as shown in A-1 below and those according to the present invention were carried out. The silver component was continuously agglomerated using a coagulation method, and the resulting sludge was continuously dehydrated using various dehydrators. The results are shown in Table 2.

In the following A to ■, a represents a condensed cationic polymer flocculant, b represents a polymerized cationic polymer flocculant, C represents an anionic polymer flocculant, and d represents an inorganic flocculant.

Table 1 Composition of silver component-containing water A, (conventional method) (1) Flocculant sulfate band used...d (addition amount 300mg/6) Polyacrylamide partial hydrolyzate...C (1f direct per colloid, -2.8 m eq / g, addition amount 10 / 1) (2) Addition order d addition - stirring - C addition - stirring - coagulation precipitation (3) Coagulation pH 5,9 (4) Solid-liquid separator coagulation sedimentation device (5) Sludge dehydrator Centrifugal dehydrator B, (conventional method) (1) Coagulant used polydimethylamino methacrylate...b (colloid equivalent, +4. 8 m eq / g, addition amount 80 ■ / 1) Polyacrylamide partial hydrolyzate ... C (colloid equivalent direct, -2.8 m eq / g, addition amount 10 ■ / N) ( 2) Addition order Addition of neutralizing agent (sulfuric acid) - Stirring - Addition - Stirring - Addition of C - Stirring - Coagulation and precipitation (3) Coagulation pH 4,0 (4) Solid-liquid separation device Coagulation and precipitation device (5) Dehydration of sludge Centrifugal dehydrator C2 (method of the present invention) (1) Coagulant used: dicyandiamide-formaldehyde condensate...a
(Additional amount 60■/l) Polydimethylamino methacrylate b (colloid equivalent value, +4.8meq/g, addition amount 20■/l
) Sodium polyacrylate...C (Additional amount 3■
/l) Polyacrylamide partial hydrolyzate...C'(
Colloid equivalent: -2,3 m eq / g, addition amount: 2 / 1) (2) Addition order: a addition - stirring - addition - stirring - c, c' addition - stirring - floating separation (3) Coagulation pH 6,2 (4) Solid-liquid separator flotation separator (5) Sludge dehydrator Screw type dehydrator D, (method of the present invention) (1) Coagulant used polyethylene polyamine...a (addition) Amount 60m
g/j2) Polydimethylamino methacrylate...B (colloidal equivalent (direct, +4.0 m eq/g, added N20/I) Sodium polyacrylate...C (added) Amount 3■
/It') Polyacrylamide partial hydrolyzate...C'(
Colloid equivalent value, -2.8meq/g, addition amount 2■/1
) (2) Addition order a Addition - Stirring - Addition - Stirring - Addition c, c' - Stirring - Floating separation (3) Coagulation pH 6,2 (4) Solid-liquid separator flotation separation device (5) Dehydration of sludge Machine screw type dehydrator E, (comparative example) (1) Coagulant used: dicyandiamide-formaldehyde condensate (
Addition amount 100 possible/A) Sodium polyacrylate...C (addition amount 5■
/l) polyacrylamide partial hydrolyzate, ---+ -('
(Colloid equivalent value, -2,8 m eq / g, addition amount 5 / 1) (2) Addition order a addition - stirring - c, c' addition - stirring - flotation separation (3) Coagulation pH 6,3 ( 4) Solid-liquid separator flotation separator (5) Sludge dehydrator Screw type dehydrator F, (comparative example) (1) Coagulant polydimethylamino methacrylate used b (colloid equivalent value, + 4 .8m eq / g, addition amount 80■/l) Sodium polyacrylate...C (additional amount 3■
/l) Polyacrylamide partial hydrolyzate...C'(
Colloid equivalent: -2,8 m e Q / g, addition amount: 2 / l1) (2) Addition order - Stirring - c, c' Addition - Stirring - Flotation separation (3) Agglomeration p)i 6. 3 (4) Solid-liquid separator flotation separator (5) Sludge dehydrator Screw type dehydrator G, (method of the present invention) (1) Coagulant used dicyandiamide-formaldehyde condensate...a
(Additional amount 60■/l) Polydimethylamino methacrylate b (colloid equivalent value, +4.8meq/g, addition amount 20■/l
) Sodium polyacrylate...C (Additional amount 6■
/1) (2) Addition order a Addition - Stirring One addition - Stirring - Addition C - Stirring - Floating separation (3) Coagulation pH 6,3 (4) Solid-liquid separator Floating separation device (5) Sludge dehydrator Screw type dehydrator Hl (method of the present invention) (1) Coagulant used: dicyandiamide-formaldehyde condensate..., a
(Amount added: 60n+g/j?) Polydimethylaminomethacrylate...b (Colloid equivalent, +4.8 m eq/g, amount added: 20■/l) Polyacrylamide partial hydrolyzate... ...C (colloid equivalent: -2,8 m eq / g, addition amount 5 / 1) (2) Addition order a, b addition - stirring - C addition - stirring - flotation separation (3) Coagulation pH 6,3 (4) Solid-liquid separator flotation separator (5) Sludge dehydrator Screw type dehydrator I, (method of the present invention) (1) Coagulant used Disia condensate Mido-formaldehyde condensate... a
(Additional amount 60■/l) Polydimethylamino methacrylate-1～・・・・・・b(
Colloid equivalent value, + 2.0 m eq / g・Additional amount 30 Akebono/l) Sodium polyacrylate・・・・・・C (Additional amount 3■
/l) Polyacrylamide partial hydrolyzate...C'(
Colloid equivalent: -2,8m eq/g, addition amount: 2mg/1) (2) Addition order: a addition → stirring → b addition - stirring - c, c' addition - stirring - flotation separation (3) Coagulation pH 6,3 (4) Solid-liquid separator flotation separator (5) Sludge dehydrator Screw type dehydrator Table 2 Treatment results

Claims (1)

[Claims] A silver component characterized in that a condensed cationic polymer flocculant, a polymerized cationic polymer flocculant, and an anionic polymer flocculant are added to silver component-containing water to recover a silver component from silver component-containing water. collection method.