JP2002192167A - METHOD FOR TREATING Se AND As-CONTAINING WASTEWATER - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating Se and As-containing wastewater capable of removing both of Se and As in a high removing ratio. SOLUTION: In the method for treating Se and As-containing wastewater, a ferrous salt is added to wastewater containing Se and As or further containing Sn and Ca(OH)2 and/or CaO is subsequently added to the wastewater to be reacted with Se, As and Sn and the obtained treated liquid is subjected to solid-liquid separation treatment. In the method for treating Se and As- containing wastewater, the ferrous salt is added to the wastewater containing an electrolytic tails liquid of the tin electrolytic cell in a blast furnace using lead scrap and/or lead tails, smoke ash, which is obtained by the reductive smelting of the roasted precipitate of copper removed slime obtained in a crude copper electrolytic refining process and/or slag, which is obtained by the reductive smelting of the roasted precipitate of copper removed slime, as a raw material and a tin removing kettle as the post-process thereof and an electric tin manufacturing process using the tin electrolytic cell as the post-process of the tin removing kettle and, thereafter, Ca(OH)2 and/or CaO is added to be reacted with Se and As and the obtained liquid is subjected to solid-liquid separation treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating wastewater containing Se and As, and more particularly to a method for treating wastewater containing Se and As which can remove both Se and As at a high removal rate.

[0002]

2. Description of the Related Art Conventionally, in the electrorefining of metals such as the electrolytic refining of blister copper, since trace amounts of selenium (hereinafter also referred to as Se) and arsenic (hereinafter also referred to as As) are contained in raw ores, these are recovered. Se is a rectifier, copier photoconductor, solar cell,
Used in a wide range of applications such as catalysts and glass coloring agents, arsenous acid is used as pesticides, rodenticides, herbicides and other pesticides, wood insecticides and preservatives, toning compounds in the glass industry, pharmaceuticals and semiconductor materials such as salvarsansan Used for etc.

On the other hand, in the wastewater generated in the process of treating the precipitate in the electrolytic cell in the above-mentioned electrolytic refining of metal, S
e, As may be dissolved, Se, As by wastewater treatment
Need to be removed. As a method for removing Se, a coprecipitation method using ferric hydroxide is known. In Japanese Patent Publication No. 48-30558, Fe ²⁺ is added to wastewater, and then pH = 3 to
By adding Cu ²⁺ under the condition of 5, the oxidation and hydrolysis of Fe ²⁺ are promoted, and under the condition of pH = 5-6, Se 2 is added.
A method for coprecipitating and recovering ferric hydroxide is disclosed.

As a method for removing As, a coprecipitation method using a ferric salt is known. However, the Se
Is effective for removing tetravalent selenium,
The effect of removing selenium is low. On the other hand, in recent years, Se has been newly specified as a water quality standard item for wastewater, and the conventional Se removal method has become insufficient.

[0005] That is, in order to meet the new water quality standards for wastewater, it has become essential to develop a method for treating wastewater containing Se.
In addition, in the electrolytic refining of metals such as the electrolytic refining of blister copper described above, it is efficient to treat wastewater containing both Se and As derived from the raw ore, and to remove both Se and As. Therefore, a wastewater treatment method capable of removing both Se and As at a high removal rate is required.

[0006]

SUMMARY OF THE INVENTION The present invention relates to
It is an object of the present invention to provide a method of treating wastewater containing Se and As which can remove both of them at a high removal rate.

[0007]

According to a first aspect of the present invention, a treatment liquid obtained by adding a ferrous salt to a wastewater containing Se and As and then adding and reacting Ca (OH) ₂ and / or CaO. Is a method for treating wastewater containing Se and As, characterized in that the wastewater is subjected to solid-liquid separation. A second invention relates to smoke ash obtained by reduction smelting of lead scrap and / or lead slag, decopperized slime obtained in a step of electrolytic refining of blister copper, and / or roasted decopperized slime. In the manufacturing process of electric tin using entanglement (: slag) obtained by reduction smelting of a material as a raw material and using a smelting furnace and a tin removal pot as a subsequent step and a tin electrolytic cell as a post-step of the tin removal pot, After adding a ferrous salt to the wastewater containing the electrolytic tail solution of the tin electrolytic tank, Ca (OH) ₂ and / or CaO are added and reacted, and the obtained treatment liquid is subjected to solid-liquid separation. This is a method for treating Se- and As-containing wastewater.

The lead scrap according to the second aspect of the present invention is, for example, a lead-containing material which is at least one selected from a used lead-acid battery, a solder component, and lead swarf. For example, a lead-containing substance that is a lead-containing fume obtained from a lead slag from a dismantling factory of used lead-acid batteries and / or environmental dust is exemplified. The first and second inventions described above are more preferably used as a method for treating the Se- and As-containing wastewater in which the Se- and As-containing wastewater further contains Sn.

In the first and second aspects of the present invention, the Se and As-containing wastewater may contain Se ⁶⁺ of 1 mg / l or more, more preferably Se ⁶⁺ of 1 to 200 mg / l, 5 mg / l or more, more preferably 5 to 20,000 mg / l of As, or
mg / l or more, more preferably contains Sn from 1 to 10,000 mg / l
It is more suitably used as a method for treating wastewater containing Se and As.

In the first and second aspects of the present invention, the amount of the ferrous salt is 0.10 (mol / l-
Treatment liquid) or more, and more preferably 0.10 to 1.
It is more preferably 0 (mol / l-treatment liquid). Also,
In the first invention and the second invention described above,
The added amount of Ca (OH) ₂ and / or CaO is preferably 2 (g / l-treated solution) or more in terms of Ca (OH) ₂ conversion, and more preferably 2 to 15 ( g / l-treatment liquid).

In the first and second aspects of the present invention, after the addition of the ferrous salt, Ca (OH) ₂ and / or
Alternatively, the pH of the processing solution, which is wastewater before the addition of CaO, is 4.0 to 6.
It is preferably 5. Further, in the first and second aspects of the present invention, the above Ca (OH) ₂ and / or
Alternatively, it is preferable that the pH of the treatment liquid at the time of adding and reacting CaO is 5.0 to 7.5.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found the following findings (1) to (5) and have reached the present invention. (1) Addition of ferrous salt to wastewater containing Se and As, Ca (OH) ₂ , CaO
Removal of Se and As by addition: Ferrous salts such as ferrous sulfate are added to Se and As-containing wastewater and reacted, and Ca (OH) ₂ and / or CaO are added and reacted, and then obtained. Se and As in the wastewater
Can be removed at an extremely high removal rate.

(2) Addition of ferrous salt to wastewater containing Se, As and Sn and removal of Se, As and Sn by addition of Ca (OH) ₂ and CaO: Ferrous sulfate is added to wastewater containing Se, As and Sn. And ferrous salts such as Ca (OH) ₂ and / or
After adding and reacting CaO 2, the resulting treatment liquid is subjected to solid-liquid separation, so that not only Se and As in the waste water but also Sn
Can also be removed at an extremely high removal rate.

(3) Regulation of pH of treatment solution after addition of ferrous salt:
By regulating the pH of the treatment solution after the addition of the ferrous salt within the range of 4.0 to 6.5, both Se and As can be removed at an extremely high removal rate. (4) Regulation of pH of treatment solution after addition of Ca (OH) ₂ and CaO: Ca (OH)
₂ and / or the pH of the treatment solution after adding CaO is 5.0
By regulating the content within the range of -7.5, both Se and As can be removed at an extremely high removal rate.

(5) The method for treating the wastewater containing Se and As described in the above (1) to (4) is a method of roasting lead scrap and / or lead slag and decopperized slime obtained in a step of electrolytically refining blister copper. Slag obtained from the reduction smelting of smoked ash obtained from the reduction smelting of wastes and / or roasted decopperized slime as a raw material; It is particularly preferably used as a method for treating wastewater containing Se and As in a production process of electric tin using a tin electrolytic cell as a post-process of a tin pot.

Hereinafter, I. First Invention, II. Second Invention, II
I. Se, As and Sn removal mechanism, and IV. Suitable reaction conditions in the present invention will be described in order. [I. First Invention:] The first invention is to add a ferrous salt to a wastewater containing Se and As, and then add and react Ca (OH) ₂ and / or CaO to obtain a treated solution. And solid-liquid separation of
It is a method for treating contained wastewater.

Table 1 shows an example of the steps of the method for treating wastewater containing Se and As according to the present invention, together with suitable reaction conditions. Also,
FIG. 1 shows an example of the change over time of the pH of the treatment liquid when the wastewater containing Se and As is treated according to the steps shown in Table 1. Table 2 shows the treatment conditions at this time, and the composition of the wastewater containing Se and As before treatment (the liquid to be treated) and the wastewater after treatment (final treatment liquid).

In the treatment of the wastewater containing Se and As shown in FIG. 1 and Table 2, a tin electrolytic tail solution in copper smelting and lead smelting described later was used as the wastewater containing Se and As. Dilute sulfuric acid is used for pH adjustment, ferrous sulfate aqueous solution adjusted to pH 1.5 with sulfuric acid to suppress oxidation is used as ferrous salt, and slaked lime is used as Ca (OH) ₂ and / or CaO. Milk was used.

As shown in Table 2, ferrous salt and Ca (O
H)_TwoAnd / or CaO 2 containing Se and As containing waste gas of the present invention.
According to the water treatment method, As and conventional removal are difficult.
Se ⁶⁺Can be removed at a high removal rate, and Sn is also highly removed.
It was found that it could be removed at the rate of removal.

[0020]

[Table 1]

[0021]

[Table 2]

[II. Second Invention:] The second invention is obtained by reduction smelting of a roasted precipitate of lead scrap and / or lead slag and decopperized slime obtained in an electrolytic purification process of blister copper. From the slag obtained from the reduction smelting of smoke ash and / or the roasted deposit of the decopperized slime as a raw material, a smelting furnace, a detinning pot as a subsequent step, and a post-step of the detinning pot as a post-step In a production process of electric tin using a tin electrolytic cell, after adding a ferrous salt to wastewater containing an electrolytic tail solution of the tin electrolytic cell, Ca (OH) ₂ and / or CaO ₂ are added and reacted, Se, As for solid-liquid separation of the obtained treatment liquid
It is a method for treating contained wastewater.

FIG. 2 shows an example of a process chart of copper smelting and lead smelting according to the present invention. In copper smelting, in the electrolytic refining of blister copper, high purity copper is electrolytically deposited on the seed plate using the blister copper produced by the converter, refining furnace and cast copper machine of the smelting plant as the anode and the seed plate as the cathode. Manufacture electrolytic copper. In the above-mentioned electrolytic refining of the crude copper, the so-called sediment (anode slime), which is a precipitate at the bottom of the copper electrolytic cell, is decopperized by sulfuric acid leaching in a decoppering tank, and the so-called decoppering obtained after the decoppering. The slime is oxidized and roasted in a roasting furnace, and selenium dioxide generated as a gas is collected as selenous acid by a collection tower, a scrubber or a wet electric dust collector, and selenite is reduced to recover Se.

The roasting residue, which is a roasting residue in the roasting furnace, is mainly composed of PbSO ₄ and is subjected to reduction smelting (reduction smelting) by adding a solvent in a smelting furnace (smelting furnace). Then, Au and Ag are collected in precious lead and processed in a silver separation furnace to obtain coarse silver. On the other hand, Pb and S are also contained in the smoke (molten ash) and entanglement (slag) generated when reducing and smelting (reducing smelting) the roasted precipitate in a melting furnace.
e and As are included.

For this reason, in the copper smelting process shown in FIG. 2, the above-mentioned smoke ash (melted smoke ash) and entanglement (slag)
Is used as a part of raw materials for lead smelting. That is, used lead-acid batteries, lead scrap such as solder components and plumber scrap, recycled raw materials such as lead slag generated in battery dismantling, etc., and the above-mentioned molten smoke and entanglement are processed in a blast furnace to form coarse lead. .

Since tin is contained in the recycle raw materials such as the solder components described above, coarse lead is detinned by a tin removal pot, and the lead content after detinning is cast and electrolyzed to produce electrical lead. To manufacture. Also, so-called tin removal slag containing tin by-produced in the tin removal pot is electrolyzed to produce electric tin.

In the above-described tin electrolysis, the electrolysis tail solution of the electrolysis tank (tin electrolysis tail solution) contains Sn, Se and As. From the viewpoint of drainage measures, these three components can be removed at a high removal rate. Required. According to the wastewater treatment method of the present invention, Sn, Se and As can all be removed at a high removal rate. Therefore, the present invention provides the treatment of the above-described tin electrolytic tail solution (Sn electrolytic tail solution). It can be particularly preferably used as a method.

[III. Removal Mechanism of Se, As and Sn:] Next, the removal mechanism of Se, As and Sn in the present invention will be described. The removal mechanism of Se, As and Sn in the present invention is:
For example, it is estimated as follows for the alkaline drainage as the Sn electrolysis tail solution described above. (Se removal mechanism :) Se in the wastewater is ferrous salt and Ca (O
H) By the addition of _2, the metal is formed according to the following reaction formulas (1) to (3).
Reduced to Se.

Na ₂ SeO ₄ + 9Fe (OH) ₂ → Se + 3Fe ₃ O ₄ ↓ + 2NaOH + 8H ₂ O... (1) Na ₂ SeO ₄ + 6Fe (OH) ₂ → Se + 3Fe ₂ O ₃ ↓ + 2NaOH + 5H ₂ O …………… (2) Na ₂ SeO ₄ + Fe ²⁺ + Fe (OH) ₂ → Se + Fe ₃ O ₄ , FeOOH, Fe (OH) ₃ ↓… (3) Metal Se and Intermediate Formation in Metal Se Formation Sn ⁴⁺ is co-precipitated with iron hydroxide and ferric arsenate generated in the reaction formula (4) described below, and as a result,
It is estimated that Se is removed at a high removal rate.

(As removal mechanism :) As in the wastewater, as a result of addition of a ferrous salt, As is precipitated mainly as ferric arsenate according to the following reaction formula (4), and Ca (OH) in the subsequent step is removed. )
_{When 2} and / or CaO is added, it is presumed that calcium arsenate precipitates according to the following reaction formula (5), and as a result, As is removed at a high removal rate by solid-liquid separation.

Fe ³⁺ + H ₃ AsO ₄ + mH ₂ O = FeAsO ₄ · mH ₂ O ↓ + 3H ⁺ …………… (4) 3Ca ²⁺ + 2H ₃ AsO ₄ + nH ₂ O = Ca ₃ (AsO ₄ ) ₂ · nH ₂ O ↓ + 6H ⁺ … (5) (Sn removal mechanism :) Sn in the wastewater precipitates as tin hydroxide and is removed at a high removal rate by solid-liquid separation.

[IV. Preferred reaction conditions in the present invention:]
Next, preferred reaction conditions in the present invention will be described. (PH of treatment solution after addition of ferrous salt :)
The pH of the treatment solution before the addition of (OH) ₂ and / or CaO (hereinafter referred to as the treatment solution after the addition of the ferrous salt) is preferably 4.0 to 6.5.

FIG. 3 shows the pH of the treatment liquid after the addition of ferrous sulfate and the residual Se concentration and residual As concentration in the final treatment liquid after solid-liquid separation when ferrous sulfate was used as the ferrous salt. The relationship is shown below. In addition, in FIG. 3, T.Se shows all Se. FIG.
As shown in the above, the pH of the treatment solution after the addition of the ferrous salt was 6.5.
If the pH exceeds 1, the removal rates of both Se and As decrease. Conversely, if the pH of the treatment solution after the addition of the ferrous salt is less than 4.0, the removal rate of As decreases.

[PH of treatment solution after addition of Ca (OH) ₂ and CaO:]
PH of treatment solution after adding Ca (OH) ₂ and / or CaO
Is preferably 5.0 to 7.5. FIG. 4 shows the relationship between the pH of the treatment liquid 1.5 hours after the addition of slaked lime and the residual Se concentration and residual As concentration in the final treatment liquid after solid-liquid separation.

As shown in FIG. 4, when the pH of the treatment liquid after the addition of slaked lime exceeds 7.5, the removal rate of As decreases. Conversely, when the pH of the treatment liquid after the addition of slaked lime is less than 5.0, As Removal rate decreases. (Addition amount of ferrous salt :) In the present invention, the addition amount of ferrous salt is preferably 0.10 (mol / l-treatment solution) or more, and more preferably 0.10 to 1.0 (mol / l- (Processing solution).

The amount of ferrous salt added is 0.10 (mol / l-treated solution)
If less, the removal rate of Se and As decreases, and conversely, if the addition amount of ferrous salt exceeds 1.0 (mol / l-treatment solution), the effect of adding ferrous salt is practically saturated, Not economic. (Liquid temperature of treatment liquid after addition of ferrous salt :) In the present invention, the liquid temperature of the treatment liquid after addition of ferrous salt is preferably 75 to 95 ° C.

When the temperature of the processing solution after the addition of the ferrous salt is lower than 75 ° C., the removal rate of Se and As decreases, and conversely, the temperature of the processing solution after the addition of the ferrous salt decreases to 95 ° C. If it exceeds, the effect of increasing the liquid temperature saturates practically, and it is not economical in terms of energy consumption. (Ferrous salt) The type of ferrous salt in the present invention is not particularly limited. However, in view of the removal rate of Se and As and the availability, ferrous sulfate is used as the ferrous salt. It is preferred to use iron and / or ferrous chloride.

(Addition amount of Ca (OH) ₂ and CaO :) In the present invention, the addition amount of Ca (OH) ₂ and / or CaO is
H) The total amount in terms of ₂ is preferably 2 (g / l-treatment liquid) or more, and more preferably 2 to 15 (g / l-treatment liquid) in the above total amount.
Is more preferable. Ca (OH) ₂ and / or Ca
If the total amount of O 2 is less than 2 (g / l-treatment solution), the removal rate of Se and As decreases, and conversely, the total amount becomes 15%.
If (g / l-treatment solution) is exceeded, the removal rate of As decreases.

(Liquid temperature of treatment liquid after addition of Ca (OH) ₂ and CaO): In the present invention, Ca (OH) ₂ and / or CaO
The temperature of the treatment liquid after the addition is preferably 75 to 95 ° C. If the temperature of the treatment liquid after adding Ca (OH) ₂ and / or CaO is lower than 75 ° C, the removal rate of Se and As decreases, and conversely
The temperature of the processing solution after adding Ca (OH) ₂ and / or CaO is 95
When the temperature exceeds ℃, the effect of increasing the liquid temperature is saturated practically, and it is not economical in terms of energy consumption.

The reaction apparatus of the processing equipment in the present invention is not particularly limited, but it is preferable to use a stirring reaction tank from the viewpoint of industrial easiness. The solid-liquid separator is not particularly limited, and the reactor may be used also as a sedimentation separation tank as shown in FIG.
Further, a thickener, a centrifuge, a filter, or the like may be used.

FIG. 5 shows an example of processing equipment suitably used in the present invention. In FIG. 5, 1 is a reaction tank (stirring reaction tank), 2 is a stirrer, 3 is a reaction liquid heating device such as a superheated steam flow tube, 4 is a processing liquid discharge pipe, 5 is a sludge discharge pipe, and 6 is a filter. Press 7, pH meter,
Numeral 8 is a pump, numeral 9 is a valve, numeral 10 is a reaction liquid (liquid to be treated), numeral 11 is raw water (a wastewater containing Se and As, liquid to be treated), numeral 12 is an aqueous solution containing ferrous salt, numeral 13 is slaked lime milk, and numeral 14 is dilute. PH adjusters such as sulfuric acid and NaOH, 15 indicates a treatment liquid, and 16 indicates dewatered sludge.

In the treatment equipment shown in FIG. 5, first, raw water (liquid to be treated) 11, which is a wastewater containing Se and As, is supplied to the reaction tank 1 and, if necessary, a treatment liquid (liquid) 11 is added by adding a pH adjuster 14. After adjusting the pH of the reaction solution to a range of 6 to 8, an aqueous solution 12 containing ferrous salt is added. The pH of the treatment liquid (reaction liquid) after the addition of the ferrous salt-containing aqueous solution is preferably 4.0 to 6.5.

After a lapse of a predetermined time, slaked lime milk 13 is added, and the treatment liquid (reaction liquid) is stirred, preferably at a liquid temperature of 75 to 95.
The reaction is carried out by adjusting the temperature of the solution (reaction solution) to within the range of 5.0 to 7.5. After a lapse of a predetermined reaction time, the treatment liquid is allowed to stand, and a solid-liquid is separated by settling. Next, the supernatant liquid (treatment liquid) of the reaction tank 1 is extracted using the treatment liquid extraction pipe 4.

Next, sludge settled at the bottom of the reaction tank 1 is extracted using a sludge extraction pipe 5 and fed to a filter press 6. The treatment liquid separated by the filter press 6 is drained out of the system together with the treatment liquid obtained above, and the dewatered sludge 16 is reused.

[0045]

The present invention will be described more specifically below with reference to examples. [Example 1] (Examples 1 to 3 of the present invention and Comparative Examples 1 and 2) In this example, the tin electrolytic tail solution generated in the lead smelting step shown in Fig. 2 was treated.

As raw materials for lead smelting, there are used lead storage batteries, solder components, lead scrap such as plumber swarf, lead slag, and reductive dissolution of roasting deposits of decoppered slime obtained in the electrolytic refining process of blister copper. A mixed raw material of smoke ash (melted smoke ash) obtained by smelting (reduction smelting) and kamimi (slag) obtained by reduction smelting (reduction smelting) of a roasted decopperized slime deposit is used.

The processing method followed the steps in Table 1 described above. In addition, dilute sulfuric acid was used for pH adjustment, ferrous sulfate aqueous solution adjusted to pH: 1.5 with sulfuric acid to suppress oxidation was used as ferrous salt, and slaked lime milk was used as Ca (OH) ₂ . .
Further, as the processing equipment, the above-described processing equipment shown in FIG. 5 was used.

That is, a stirred reaction tank is used as a reaction apparatus.
A sedimentation separation method was used as the solid-liquid separation method. In addition,
In this example, the case of slaked lime milk was not added.
An experiment was performed. Table 3 shows the processing conditions, the composition of the liquid to be processed, and
The final treatment liquid composition is shown. As shown in Table 3, the present invention
According to the treatment method, the addition of ferrous salt, Ca (OH) _TwoAddition of
With high removal rate for both Se and As and Sn
It was found to be removable.

By setting the pH of the liquid to be treated after the addition of the ferrous salt and the pH of the liquid to be treated after the addition of Ca (OH) ₂ within the preferred ranges of the present invention, both Se and As can be extremely reduced. It was found that removal was possible at a high removal rate.

[0050]

[Table 3]

[0051]

[Table 4]

[Example 2] (Examples 4 and 5 of the present invention) A tin electrolytic tail solution was treated in the same manner as in Examples 1 to 3 of the present invention described above. In this example, in order to examine the effect of adding each of the ferrous salt and Ca (OH) ₂ , after pH adjustment, 5 minutes after FeSO ₄ addition, 1 to 5 Ca (OH) ₂ addition
After a period of time, a part of the reaction solution was extracted, and the extracted solution was subjected to solid-liquid separation. Then, the concentrations of Se, As, and Sn in the solution were examined.

Table 4 shows the obtained results together with the processing conditions. As shown in Table 4, the Se concentration was Ca (OH) ₂ added 1
After the addition, the concentration decreased over time, and became less than 1 mg / l 3 hours after the addition. From this, the reason why Se can be removed at a high removal rate is that metal Se produced according to the above-mentioned reaction formulas (1) to (3) and Sn which is an intermediate product in the production of metal Se
⁴⁺ co-precipitates with iron hydroxide and ferric arsenate,
It is estimated that the solid-liquid separation removes it at a high removal rate.

[0054]

[Table 5]

Example 3 (Example 6 of the Invention) The treatment of the tin electrolysis tail solution was performed in the same manner as in Examples 1 to 3 of the invention in Example 1 described above. In this example, the treatment was performed under the same treatment conditions as in Example 1 of the present invention except that an aqueous solution of ferrous chloride was used instead of the aqueous solution of ferrous sulfate in Example 1 of the present invention.

The amount of ferrous chloride added was 0.15 (mol / l-
(Treatment liquid). As a result, the composition of the liquid to be treated; the total Se concentration:
For 57 mg / l, As concentration: 3360 mg / l, Sn concentration: 2350 mg / l, the composition of the final treatment solution was: total Se concentration <1 mg / l, As concentration <1.
mg / l, Sn concentration <1 mg / l, and excellent Se, As and Sn removal effects were obtained as in Example 1 of the present invention described above.

Although the embodiment has been described above, in the present invention, according to the principle of the present invention, Ca (OH) _{2 and} / or CaO or both of them are directly treated to be treated instead of slaked lime milk used in the embodiment. It can also be added to the liquid.

[0058]

According to the present invention, both Se and As in wastewater can be removed at a high removal rate, which is of great industrial significance. Further, according to the present invention, wastewater containing Se, As, and Sn can be treated by an industrially simple method, and the wastewater in copper smelting and lead smelting is extremely efficiently treated. It became possible to do.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of a change over time in the pH of a treatment solution during a wastewater treatment containing Se and As.

FIG. 2 is a process chart showing an example of copper smelting and lead smelting according to the present invention.

FIG. 3 is a graph showing the relationship between the pH of a processing solution after the addition of ferrous sulfate and the concentrations of residual Se and residual As in a final processing solution.

FIG. 4 is a graph showing the relationship between the pH of a treatment liquid 1.5 hours after the addition of slaked lime and the residual Se concentration and residual As concentration in the final treatment liquid.

FIG. 5 is a flow sheet showing an example of a facility for treating wastewater containing Se and As according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tank (stirring reaction tank) 2 Stirrer 3 Reaction liquid heating apparatus (superheated steam circulation pipe) 4 Treatment liquid extraction pipe 5 Sludge extraction pipe 6 Filter press 7 pH meter 8 Pump 9 Valve 10 Reaction liquid (liquid to be treated) 11 Raw water (liquid to be treated) 12 Ferrous salt-containing aqueous solution 13 Slaked lime milk 14 pH adjuster 15 Treatment liquid 16 Dewatered sludge

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C22B 7/04 C22B 30/04 30/04 61/00 61/00 C25C 1/14 C25C 1/14 7/06 301Z 7 / 06 301 C22B 3/00 Q // C22B 25/00 25/04

Claims (8)

[Claims] Claims 1. A ferrous salt is added to a wastewater containing Se and As, and Ca (OH) ₂ and / or CaO is added and reacted.
Se, As characterized in that the obtained processing solution is subjected to solid-liquid separation
How to treat contained wastewater. 2. Smoke ash obtained by reductive smelting of lead scrap and / or lead slag and decopperized slime obtained in the electrolytic refining step of blister copper and / or roasted product of said decoppered slime From the smelting obtained by the reduction smelting of
In a production process of electric tin using a blast furnace and a tin removal pot as a subsequent step and a tin electrolytic cell as a subsequent step of the tin removal pot, ferrous iron is added to wastewater containing an electrolytic tail solution of the tin electrolytic tank. A method for treating Se- and As-containing wastewater, comprising adding Ca (OH) ₂ and / or CaO ₂ and reacting after adding a salt, and subjecting the resulting treatment liquid to solid-liquid separation. 3. The method for treating wastewater containing Se and As according to claim 1, wherein the wastewater containing Se and As further contains Sn. 4. The wastewater containing Se and As contains Se ⁶⁺ of 1 mg / l or more, As of 5 mg / l or more, or Sn of 1 mg / l or more. S described in crab
e, How to treat As-containing wastewater. 5. The addition amount of the ferrous salt is 0.10 (mol / l-
The method for treating wastewater containing Se and As according to any one of claims 1 to 4, wherein the treatment liquid is the above. 6. The method according to claim 1, wherein the amount of Ca (OH) ₂ and / or CaO added is 2 (g / l-treated solution) or more as a total amount in terms of Ca (OH) _2. S described in any one of ~ 5
e, How to treat As-containing wastewater. 7. The method according to claim 1, wherein the pH of the treatment liquid before the addition of Ca (OH) ₂ and / or CaO is 4.0 to 6.5 after the addition of the ferrous salt. Se described,
How to treat As-containing wastewater. 8. The method according to claim 1, wherein said Ca (OH) ₂ and / or CaO ₂ is added, and the pH of the treatment solution at the time of the reaction is 5.0 to 7.5. How to treat contained wastewater.