JPH1192839A - Recovery of metal tin from sludge containing tin oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently recovering metal Sn from sludge contg. the oxide of Sn removed by an acidic soln. from Sn plating metallic materials. SOLUTION: This method consists in recovering the metal Sn from the sludge contg. the SnO2 removed by the acidic soln. from the Sn plating metallic materials. On this method, the moisture content in the sludge contg. the SnO2 is confined to <=10% and such sludge 2 is brought into contact with massive carbon based solid reducing agents 3 in a phase state. The sludge is then heated to >=700 deg.C in a furnace 1 to reduce the SnO2 in the sludge to the metal Sn 4 and, thereafter, the reduced metal Sn is recovered from the sludge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering metal Sn from sludge containing Sn oxide, which is produced by chemically treating a tin (Sn) plated metal material, and more particularly to a method for recovering metal material such as electronic material. The present invention relates to a method for recovering metallic Sn from sludge containing Sn oxide generated by chemically treating Sn-plated copper and a copper alloy material.

[0002]

2. Description of the Related Art Sn plating is widely used for surface treatment of copper and copper alloy materials for the purpose of improving the corrosion resistance and solderability of a base metal. On the other hand, when refining Sn-plated metal, for example, waste material of Sn-plated copper and copper alloy material, when used as a melting raw material with Sn plating attached, Sn is mixed into the obtained molten copper, this
Sn, as an impurity, causes a component defect out of the product standard of copper and copper alloy materials. And once mixed into the molten copper
It is extremely difficult to remove Sn by refining during melting or the like, and it is impractical from the point of refining efficiency. Therefore, when recycling waste material of Sn-plated metal,
It is necessary that the plating be separated or separated and then reused as the base metal.

For this reason, when the Sn plating is separated from the base metal, usually, the Sn plating metal material is chemically treated by dipping it in a strong acid solution such as hydrofluoric acid, hydrochloric acid or nitric acid. Acid and Sn plating to convert Sn into oxide (S
It is general to peel off and remove as nO ₂ ). However, the stripped and removed Sn oxide settles and accumulates at the bottom of the strong acid acidic solution tank (Sn plating stripping treatment tank) as sludge, which hinders the Sn stripping process, and after a certain period of time, It is necessary to discharge sludge containing this Sn oxide. The treatment of the discharged sludge is a new problem.

Conventionally, the discharged sludge has not been effectively used or recycled, for example, by recovering Sn contained in the sludge, and has been dumped or treated as a mere industrial waste at a landfill or the like at a high cost. .

[0005]

However, these conventional processes have a fundamental problem that they are costly and have a problem in terms of environmental conservation, and that Sn cannot be reused as a resource. Then, in order to reuse as resources, a method of efficiently recovering metal Sn from sludge containing oxides of Sn is absolutely necessary. Moreover, when recovering the metal Sn, the recovered metal Sn must be of a purity that can be reused (specifically, a purity of 90% or more), and if the recovery rate of the metal Sn is not high ( (Specifically, a recovery rate of 90% or more)) A recovery method cannot be industrially established. In other words, in this technical field, there has been no method for efficiently recovering metal Sn from the sludge containing the oxide of Sn at the above-described level, so that conventionally, it could only be treated as industrial waste. .

The present invention has been made in view of these problems of the prior art,
Sn oxide generated by chemically treating Sn plated metal material
It is an object of the present invention to provide a method for efficiently recovering metal Sn from sludge containing (hereinafter simply referred to as SnO ₂ ).

[0007]

Means for Solving the Problems To achieve the above object, a method according to the present invention provides a method for treating a Sn-plated metal material from a sludge containing SnO ₂ which is produced by chemically treating the material with an acidic solution or the like. A method of recovering metal Sn, in which a sludge containing SnO ₂ and a massive carbon-based solid reducing agent are brought into contact in a layer state,
Preferably, a massive carbon-based solid reducing agent is placed on and contacted with the sludge, and is contacted under air or oxidizing atmosphere.
The gist of the present invention is to reduce the SnO ₂ in the sludge to metal Sn by heating to 700 ° C. or higher, and to separate the molten metal Sn obtained by the reduction in a molten state or after solidification from the sludge.

Usually, Sn ore is an oxidized ore containing SnO _2, and therefore, the refining of Sn is basically performed by reducing this Sn oxidized ore. In this reduction reaction, coke is used as a reducing agent, electric furnace refining is performed at a temperature of about 1400 K, and the generated molten metal Sn is separated at a specific gravity difference to obtain rough Sn.

In the present invention, the sludge containing SnO ₂ is also subjected to a reduction reaction at a high temperature using a reducing agent to convert SnO ₂ into metallic Sn.
In that respect, the principle is that the Sn
Is the same as the refining method for obtaining

However, on the other hand, in the present invention, it is generated by chemically treating a Sn-plated metal material with an acidic solution or the like.
Intended for sludge containing SnO _2, since the target is different from the refining process of the Sn ore, to specific reduction method is different, the recovery rate and purity of 90% or higher level of recovery metal Sn In order to do that, you need a unique twist. Hereinafter, this point will be described in detail.

First, in the present invention, in the smelting reduction, in order to increase the recovery rate of metal Sn, the water content of the sludge containing SnO ₂ is preferably as low as possible. For this reason, when the water content of the sludge containing SnO ₂ is high, it is preferable to actively dehydrate the sludge. In addition, the water content of the sludge referred to in the present invention is the content of the water contained in the sludge or the plating stripping solution with respect to the weight of the sludge. Figure 2
4 shows the relationship between the water content of sludge containing SnO ₂ and the recovery of metallic Sn. 2, Sn-plated pure Cu material from acidic solutions intentionally changing the water content of the sludge containing SnO ₂ which is removed by (hydrofluoric acid, mixed acid solution of nitric acid), were each 500g charged into a graphite crucible, sludge Is sufficiently coated with charcoal, a carbon-based solid reducing agent, and heated to 1300 ° C. to perform a reduction reaction.The obtained molten metal Sn is extracted, and the extracted metal Sn weight and SnO _{2 in the} sludge are extracted. The recovery rate with metal Sn was determined based on the weight. As is clear from FIG. 2, the water content of the sludge has a great effect on the recovery of metallic Sn.
More specifically, in the example of FIG. 2, if the water content of the sludge is 20% or less, a recovery rate of 80% or more is obtained, and if the water content of the sludge is 10% or less, 90% or more. However, the recovery of metal Sn sharply decreases as the water content of the sludge increases. The reason is that if a large amount of water is present in the sludge, the reaction between water and CO generated from the carbon-based solid reducing agent proceeds preferentially, so that the carbon-based solid reducing agent that reduces SnO ₂ or
This is because the amount of CO is insufficient. Therefore, in the present invention
In order to guarantee a recovery rate of metal Sn of 90% or more, the water content of the sludge containing SnO ₂ is preferably as low as possible, preferably the water content of the sludge is 20% or less, more preferably the water content of the sludge. 10% or less. The method of dewatering the sludge containing SnO ₂ and lowering the water content is not particularly limited, and may be performed mechanically by a known dehydrator such as centrifugal separation or pressure squeezing, or by a heater or a high-temperature gas. It may be performed by heating. These dehydrating means are appropriately selected depending on physical properties such as viscosity of sludge and other conditions.

Next, in the present invention, in order to promote the SnO ₂ reduction reaction with respect to the sludge having a reduced water content,
It is necessary to bring a massive solid reducing agent into contact in a layer state and reduce it in the air or in an oxidizing atmosphere containing oxygen or an oxidizing agent. The layer state referred to in the present invention means that the sludge and the massive solid reducing agent are not in a state where individual particles are uniformly mixed, but the sludge layer and the massive solid reducing agent layer are macroscopically face to face with each other. The state of contact. Further, the finer the particles of the solid reducing agent are, the more difficult the reduction reaction will be. Therefore, it is necessary to make the particles of the solid reducing agent into a large lump. FIG. 3 shows the relationship between the state of contact between the sludge and the carbon-based solid reducing agent and the rate of recovery of metallic Sn. A shown on the horizontal axis of FIG. 3, a graphite crucible, the acidic solution from the Sn-plated pure Cu material sludge containing SnO ₂ as well as 500g charged removed by (hydrofluoric acid, mixed acid solution of nitric acid), carbon-based solid Fine charcoal as a reducing agent is added and mixed so that the fine charcoal is uniformly mixed in the sludge. On the other hand, B shown on the horizontal axis of FIG. 3 is a heated dewatered sludge containing the same SnO ₂ as A in the graphite crucible (water content 5%).
And the lump of charcoal is simply placed on the surface of the sludge, and the upper layer is made of charcoal and the lower layer is made of sludge, and the sludge is sufficiently covered with charcoal. Then, these were also heated to 1300 ° C. to perform a reduction reaction, and the obtained molten metal Sn was extracted.From the extracted metal Sn weight and the SnO ₂ weight in the sludge, the recovery of metal Sn was determined. Things. As is evident from Fig. 3, although the collection of metal Sn was more than 90% in B where lump charcoal was simply placed on the surface of the sludge, in A where pulverized charcoal was uniformly mixed in the sludge, The recovery rate of Sn is only about 0%.

From the common sense of the reduction reaction, the reaction efficiency should be better if the solid reducing agent is finely divided and uniformly mixed in order to increase the contact surface area between the sludge and the solid reducing agent. Nevertheless, in the sludge containing SnO ₂ removed from the Sn-plated metal material with an acidic solution, which is the object of the present invention, it is rather preferable to contact the sludge with the massive solid reducing agent in a layer state. Good recovery of metal Sn. The reason is that the SnO ₂ reduction reaction is not caused by the direct reduction of the carbon-based solid reducing agent, but is reduced by carbon monoxide generated by the reaction of the carbon-based solid reducing agent with atmospheric oxygen. it is conceivable that. Therefore, when the solid reducing agent is pulverized and uniformly mixed, the contact efficiency is certainly improved, but conversely, the atmosphere decreases around the carbon-based solid reducing agent mixed in the sludge layer. As a result, the amount of carbon monoxide itself generated by the reaction with the oxygen in the atmosphere is reduced, and the reduction reaction of SnO ₂ by the carbon monoxide does not occur, but only the direct reduction reaction by the carbon-based solid reducing agent occurs. Since the reaction rate of the direct reduction by this solid reducing agent is slow and occurs only in the vicinity of the finely divided solid reducing agent, the obtained metal Sn is also small,
Also, reduced molten Sn is generated in a fine powder state according to the size of the carbon-based solid reducing agent powder. And this fine powder metal
Since Sn is small in quantity and small in size and specific gravity, it remains in the sludge and does not fall and aggregate due to a density difference at the bottom of the sludge. Conceivable.

On the other hand, as in the present invention, if SnO ₂ is reduced by the carbon-based solid reducing agent and carbon monoxide generated by oxygen in the atmosphere, SnO ₂ distributed in the sludge is converted to SnO ₂ . On the other hand, carbon monoxide gas permeates the sludge. Therefore, the reduction reaction itself occurs entirely in the sludge, the amount of reduced metal Sn also becomes large, and the reduced molten metal Sn easily aggregates, and the obtained metal Sn becomes large droplets, and Drops and gathers at the bottom due to the density difference, and the efficiency of separation and recovery from sludge and the purity of recovered metal Sn increase. Therefore, in order to achieve a recovery rate of the recovered metal Sn of 90% or more and a purity of the recovered metal Sn of 90% or more in terms of separation efficiency or recovery efficiency from the sludge, the sludge and the massive solid reducing agent are layered. In addition, it is necessary to make contact under an air atmosphere.

Further, in the present invention, the recovery rate of the recovered metal Sn
In order to make the purity of the recovered metal Sn 90% or more and 90% or more, the reduction temperature of the sludge needs to be 700 ° C or more. FIG. 4 shows the relationship between the reduction temperature of sludge and the recovery rate of metallic Sn. Fig. 4 shows Sn plating pure on a graphite crucible.
500 g of heated dewatered sludge (water content: 5%) containing SnO ₂ removed from the Cu material with an acidic solution (a mixed acid solution of hydrofluoric acid and nitric acid), and lump charcoal was simply placed on the surface of the sludge. The upper layer was charcoal, the lower layer was sludge, the sludge was sufficiently covered with charcoal, reduced for 30 minutes by changing the heating temperature, and the resulting metal Sn was extracted.The extracted metal Sn weight and the SnO ₂ weight in the sludge were extracted. From this, the recovery rate with metal Sn was determined. As is evident from Fig. 4, the reduction temperature is 700 ° C.
As described above, a recovery rate of metal Sn of 90% or more and a purity of recovered metal Sn of 90% or more can be obtained. However, as is clear from FIG.
Even if the reduction (heating) temperature is too high, the recovery rate and purity of metal Sn will not be further improved. Therefore, the upper limit of the reduction temperature is preferably 1300 ° C. in consideration of economy.

[0016]

1A and 1B show an embodiment of the present invention. First, as shown in FIG. 1 (A), sludge 2 whose water content has been reduced by dehydration is put into a crucible-shaped heating furnace 1 having an open upper part which is easily opened to the atmosphere. Then, a lump of charcoal 3 is placed on the surface of the sludge 2 to cover the surface of the sludge 2. In this state, the furnace is heated to reduce SnO ₂ in the sludge. In this way, as shown in FIG. 1 (B), the volume of the sludge 2 decreases due to the scattering of water and volatile components, leaving only the residue. On the other hand, the reduced molten metal Sn accumulates at the bottom of the heating furnace 1 due to a difference in specific gravity. The metal Sn accumulated at the bottom of the heating furnace 1 is separated from sludge (residue) by extracting the metal Sn from the bottom in a solid state by melting or cooling, or removing the sludge residue on the upper part.

In order to further increase the purity of the separated metal Sn, the metal Sn is further dissolved and reduced with a suitable reducing agent such as carbon. Further, it is preferable that these recovered metals Sn are reused as an alloy melting raw material of a metal material such as a copper alloy.

[0018]

Next, embodiments of the present invention will be described. Scraps with different types of copper, such as scraps plated with Sn on pure copper-based copper plates, scraps plated with Sn on Cu-Fe copper alloy plates, mixed scraps plated with Sn on Cu-Fe copper alloy plates and Cu-Ni copper alloy plates, Each was immersed in a mixed acid solution of hydrofluoric acid and nitric acid, and the acid was reacted with Sn plating to convert tin (Sn) to oxide (S
It was peeled off as nO ₂ ). The sludge containing the generated SnO ₂ and the acidic solution was heated at 120 ° C. and dewatered to prepare sludges having different moisture contents. The sludge of Invention Example No. 7 in Table 1 was the sludge as produced (water content: 50%), and was not dehydrated by heating. After measuring the amount of SnO _{2 in} the solid content of these sludges with different moisture contents,
50 kg / ch is charged into the crucible-shaped heating furnace 1 shown in Fig. 1, and lump of charcoal is placed on the surface of the input sludge at 20 kg / ch and
A reduction treatment was performed by heating to 30 ° C. and holding for 30 minutes. After that, the sludge residue was discarded, and the metal Sn accumulated at the bottom of the crucible
Was separated and recovered, and the purity and recovery of this metal Sn were determined.
Table 1 shows the results.

[0019]

[Table 1]

As is apparent from Table 1, the water content of the sludge is set to 10% or less, and the carbon-based solid reducing agent is
Invention Examples Nos. 1 to 4 in contact with sludge in a layer state
Both the recovery rate and purity of Sn are 90% or more. On the other hand, although the carbon-based solid reducing agent is in a lump and is in contact with the sludge in a layer state, the invention example No. 5 in which the sludge moisture content is 20%, the recovery rate of metal Sn is 80% and the purity is low.
About 91% is inferior to Invention Examples Nos. 1-4. In addition, in Invention Examples Nos. 6 and 7 in which the sludge moisture content exceeds 20%, the recovery rate of metal Sn is extremely low, particularly 48 to 69%, and the purity is 63 to 84%.
And lower. As a result, considering higher efficiency (cost and profitability) in practical use, the higher the recovery or purity of metal Sn, the better, and the water content of sludge as in Invention Examples 1 to 5 is 10%. A low water content of from 20% to 20% is preferred. However, on the other hand, compared with the prior art in which the recovery of metal Sn is difficult, recovery of a considerable amount of metal Sn is possible, even at a low recovery rate as in Invention Examples Nos. 6 and 7, which is sufficiently significant. Have. Note that this embodiment is an example of an actual machine scale,
The sludge moisture content and metallic Sn at the laboratory level in FIG.
The relationship with the recovery rate is that the numerical value does not always correspond to a portion having a particularly high water content, but the tendency is the same. In particular, in the portion where the water content of the sludge is low, as in FIG. 2, if the water content is 10% or less, a high recovery rate of 90% or more is obtained.
High purity of 90% or more is obtained, and even with a water content of 20% or less, a recovery of about 80% and a purity of about 90% are obtained.

For comparison, in the case of the above-mentioned invention example, except that the pulverized charcoal was added at the time of reduction melting, and that the pulverized charcoal was thoroughly mixed so as to be uniformly mixed with the sludge in the heating furnace. Under the same conditions as in 1. and 2, smelting reduction was performed to recover metallic Sn. But as a result,
In each of these comparative examples, as in FIG.
The recovery of Sn was almost impossible. Therefore, these results support the significance of the requirements of the present invention in which the carbon-based solid reducing agent is made into a bulk and is in contact with sludge in a layered state.

Incidentally, the recovered metal Sn of Invention Examples Nos. 1 to 4 was
Cu-Sn based copper alloy ingot was used as a raw material for melting Cu-Sn based copper alloy. In addition, the recovered metal Sn of Invention Examples Nos. 1 and 3 is high in purity, so that the recovered metal Sn remains as it is, and the recovered metal Sn of Invention Examples No.
Since the recovered metal Sn of 4 is slightly low in purity, 20 kg of charcoal as a reducing agent is added to the tin surface in a crucible, and then re-dissolved and re-refined (reduced) at 1200 ° C.
It was used as a raw material for dissolving 99% of metal Sn. The ingot was hot-worked and cold-worked into a 1 mm thick Cu-Sn based copper alloy plate and a 1.2 mm thick 19.0 mmφ and 25.4 mmφ copper alloy tube. The quality of the copper alloy tube was not abnormal, satisfying the required properties in terms of mechanical properties and surface properties, and each could be used as a copper alloy plate for electronic materials and copper alloy tubes for heat exchangers. .

[0023]

As described above, according to the metal Sn recovery method of the present invention, the metal Sn is recovered from the sludge containing SnO ₂ removed from the Sn-plated metal material by the acidic solution, and the recovery rate of the recovered metal Sn is improved. And a purity of 90% or more, which enables efficient recovery. Moreover, also the method, rather than a large-scale facilities and complicated methods, can be performed with relatively simple equipment and methods, as a result, opened the way to recover metallic Sn as resources from sludge comprising SnO ₂ In this respect, industrial significance is significant.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention. FIG. 1 (a) is an explanatory diagram showing heating (reduction) of sludge, and FIG. 1 (b) is an explanatory diagram showing heating (reduction) of sludge.

FIG. 2 is an explanatory diagram showing the relationship between the water content of sludge and the recovery of metal Sn.

FIG. 3 is an explanatory diagram showing a relationship between a contact state between sludge and a carbon-based reducing agent and a recovery rate of metal Sn.

FIG. 4 is an explanatory diagram showing a relationship between a reduction temperature of sludge and a recovery rate of metal Sn.

[Explanation of symbols]

 1: heating furnace 2: sludge 3: charcoal 4: metal Sn

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshiaki Narishige 14-1, Chofu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Inside the Kofu Steel Works Chofu Works (72) Inventor Kazuhiro Oe 141-1, Nagafuminatocho, Shimonoseki City, Yamaguchi Prefecture Kobe Steel, Ltd.

Claims (9)

[Claims] 1. A method for recovering metal Sn from a SnO ₂ -containing sludge produced by chemically treating a Sn-plated metal material, wherein the SnO ₂ -containing sludge and the massive carbon-based solid reducing agent are combined with each other. After contacting in a layered state and heating to 700 ° C or higher to melt-reduce SnO ₂ in sludge to metallic Sn,
A method for recovering metal Sn from sludge containing SnO ₂ , wherein the molten metal Sn obtained by the reduction is separated from the sludge. 2. The method for recovering metal Sn from a sludge containing SnO _{2 according} to claim 1, wherein the smelting reduction is performed with the water content of the sludge being 20% or less. 3. The method for recovering metallic Sn from SnO ₂ -containing sludge according to claim 1, wherein the smelting reduction is performed with the water content of the sludge being 10% or less. 4. The Sn according to claim 1, wherein a massive carbon-based solid reducing agent is placed on the sludge.
A method for recovering metal Sn from sludge containing O ₂ . 5. The method for recovering metal Sn from sludge containing SnO _{2 according} to claim 1, wherein charcoal and / or coke is used as the carbon-based reducing agent. 6. The method for recovering metal Sn from sludge containing SnO _{2 according} to claim 1, wherein the recovery rate of the metal Sn is 90% or more. 7. The method for recovering metal Sn from sludge containing SnO _{2 according} to any one of claims 1 to 6, wherein the purity of the recovered metal Sn is 90% or more. 8. The method according to claim 1, wherein the metal Sn separated from the sludge is further dissolved, and the dissolved Sn is reduced by a reducing agent to make the purity of the metal Sn 95% or more. method of recovering metallic Sn from sludge comprising SnO _2. 9. The method for recovering metal Sn from sludge containing SnO _{2 according} to any one of claims 1 to 8, wherein the metal Sn separated from the sludge is used as an alloy raw material for a copper alloy.