JP6316100B2 - Mine wastewater or osmotic water treatment method - Google Patents

Description

The present invention relates to a method for treating mine wastewater or osmotic water.
Specifically, the present invention relates to a method for recovering these useful metals from mine wastewater or permeated water containing Cu ions, Zn ions and Fe ions, and a method for detoxifying the treated wastewater.
More specifically, the present invention recovers useful metals at a high recovery rate from underground effluent that flows out from a metal mine or percolated water that flows out from a deposit or accumulation site of metal mine treatment, and treated water after recovery. It relates to a practical and economical way to make pollution-free.

In metal mines, especially in many Japanese mines, minerals are composed of sulfide minerals, so minerals are oxidized with oxygen in the air to produce sulfate ions and metal ions, which are dissolved in rainwater and groundwater. It is known to become mine wastewater.
This acid mine drainage cannot be passed directly to a lake, river or sea.

Conventionally, as a treatment technique for acidic mine wastewater, the divalent iron ion Fe ²⁺ contained in the acidic mine wastewater is forcibly oxidized in the first stage to form a trivalent iron ion Fe ^3+, and then or simultaneously. By adding a base to make acid mine wastewater neutral or basic, Fe ³⁺ is precipitated and precipitated as ferric hydroxide (Fe (OH) ₃ ), and the strong coprecipitation of ferric hydroxide It is widely known that all other metal ions are precipitated and precipitated all at once as a mixture of metal hydroxides by utilizing the above characteristics, and is practiced in most mines.
Even after the mining is stopped, the metal mine generates semi-permanent wastewater and permeated water from the mine described above (hereinafter, these may be collectively referred to as “acid mine wastewater”). Precipitation from neutralization of acid mine drainage is on the rise, and construction of dams has become a major social problem from the viewpoint of securing land for storage dams, environmental destruction and pollution, and the complexity of maintenance and management. Yes.

  Conventionally, several methods for recovering useful metals from acidic mine wastewater have been proposed. For example, in Patent Document 1, in order to elute and remove arsenic and sulfur contained in the neutralized residue generated in the wastewater treatment process according to the prior art from acidic mine wastewater, it is made alkaline with sodium hydroxide or potassium hydroxide solution. The method of using the residue after this for iron smelting is described.

  In Patent Document 2, acidic metal mine drainage containing heavy metals is sequentially put into the first container to the fourth container, and oxidation treatment, PH control, iron oxidation bacteria treatment, and re-PH control are performed, and iron, copper, and zinc are added. The method of recovery is described.

  Patent Document 3 describes a method of gelling by adsorbing mine-generated water with a water-absorbing resin having an acid group, but this method is not intended to recover useful metals from mine wastewater. .

JP 2006-328498 A JP 2004-202488 A JP 2004-148140 A

  Patent Document 1 only discloses a method for removing arsenic and sulfur from a neutralized residue generated in a conventional water treatment process of acidic mine wastewater to recycle iron. There is no teaching about the method of recovering useful metals directly from wastewater, and there is no teaching about pollution-free treatment water. Patent Document 2 describes the recovery of iron, copper and zinc by oxidizing the mine drainage from the first stage, but the process is complicated, its management and operation are complicated, expensive and economical. It's not an ideal process. Moreover, the more valuable copper and zinc have the disadvantage of insufficient recovery and purity.

  Therefore, the present inventors have advanced research on a method for recovering each metal of copper, zinc and iron with relatively high purity and high recovery rate from acidic mine wastewater. As a result, according to the present invention, an economical method has been found in which copper, zinc and iron can be recovered from acid mine wastewater with high purity and as a recyclable metal in a high yield. It was also found that the wastewater in the water can be made pollution-free as clean water.

According to the present invention, the following acid mine wastewater treatment method is provided.
(1) (a) Metallic acid wastewater containing at least copper ions and iron ions and / or zinc ions is reduced in the presence of a reducing agent in the first container to deposit copper metal and recovered, and then (b) adding base solution obtained after precipitation and recovery processes metallic copper in the container of the first in the second vessel while maintaining a reducing atmosphere, iron ions and / Alternatively, a method for treating acidic mine wastewater that precipitates and collects zinc ions as hydroxides.
(2) (a) The acidic mine drainage containing at least copper ions, iron ions and zinc ions is reduced in the presence of a reducing agent in the first container to deposit and recover metallic copper , b) A base is added in the second container while the aqueous solution obtained after the copper is precipitated and collected in the first container while maintaining the reducing atmosphere, and zinc ions are precipitated and collected as hydroxides. And (c) adding a base in the third container while keeping the aqueous solution obtained after precipitation and recovery of zinc ions as hydroxide in the second container in a reducing atmosphere, and ferrous hydroxide A method for treating acidic mine wastewater that precipitates and collects Fe (OH) ₂ .
(3) In the invention of the method for treating acidic mine wastewater, the reducing atmosphere is an acid in which oxygen molecules are not present in the gas phase portion of the container and / or an oxygen molecule blocking agent is used at the gas-liquid interface. Treatment method of mine wastewater.
(4) In the invention of processing method the acid mine drainage, oxygen molecules blocker, processing method of acid mine drainage liquid paraffin.
(5) In the invention of processing method of the acid mine drainage, the reducing agent is, processing method of acid mine drainage is sodium dithionite _{(Na 2 S 2 O 4)} .
(6) In the invention of processing method of the acid mine drainage, the processing method of acid mine drainage the base is sodium hydroxide.

According to the method of the present invention, valuable metals such as copper, zinc and iron can be recovered from acidic mine wastewater with relatively high purity and high recovery rate, and the process is also simple and economical. And practical. In addition, according to a preferred embodiment of the present invention, the water that has been subjected to the treatment after the metal recovery has the advantage that it can be drained as clean water containing almost no harmful substances.
Furthermore, there is an advantage that almost no precipitate or deposit due to neutralization, which has been a big problem in the prior art, is eliminated.
In the method of the present invention, in a particularly preferred embodiment, the metal to be recovered is desirably in the order of copper; zinc; iron.

In the present invention, the mine is not limited to a mine producing metal, but may be a mine that is suspended or abolished.
In the present invention, the target of recovery of useful metals "acidic mine drainage" is copper ion at least, is not particularly limited as long as anti wastewater acidic containing zinc ions and iron ions. As described above, “acid mine wastewater” may be anti-waste water that flows out from a metal mining road, or it may be permeated water that is generated from a treated or deposited material that has been processed from a mined ore. Good.

These acidic mine wastewaters contain various metals, mainly in the form of sulfates, are acidic and many have a pH value of about 2-6, in particular about 3-5.5. In Japan, there have been many zinc mines, gold mines, silver mines, etc., mainly iron mines and copper mines, but now they are almost completely abandoned. In particular, the present invention can be advantageously applied to acidic mine wastewater derived from a copper mine. The method of the present invention is applied even when other metals such as nickel, aluminum, manganese, lead, silver, cadmium and arsenic are contained in the acid mine drainage water in addition to copper, zinc and iron. be able to.
Moreover, it is preferable that the acidic mine wastewater used by this invention flows into a 1st container, avoiding an oxidizing atmosphere from the time of the generation | occurrence | production, and maintaining a reducing atmosphere as much as possible.

The present inventors reduce acidic mining wastewater containing at least copper ions, iron ions and zinc ions in the presence of a reducing agent, and deposit copper ions, iron ions and zinc ions as simple metals or compounds thereof, respectively.・ A method for treating acid mine drainage, which is characterized by recovery, was discovered.

  Here, the degree of the reduction treatment can be indicated by the DO value in the aqueous solution. The smaller the DO value, the better, but generally it is practical to keep it at 5 mg / L or less, preferably 1 mg / L or less, particularly preferably 0.3 mg / L or less.

In addition, in order to find an optimum reducing agent, the present inventors added various reducing agents and investigated the reactivity with metal ions. For example, as a reducing agent, sodium dithionite (Na ₂ S ₂ O ₄ ), sodium hydrogen sulfite (NaHSO ₃ ), sodium sulfite (Na ₂ SO ₃ ), hydrazine-hydrate (N ₂ H ₄ .H ₂ O ), 1-amino-4-methylpiperazine, sodium erythorbate, etc. were added, although a slight difference in reactivity was observed depending on the type of metal ion, but in each case a reducing action was observed.

  Among these reducing agents, sodium dithionite and hydrazine have good reactivity, especially the reactivity with copper ions, and it is recognized that copper ions fold out with high yield as metallic copper. It was. Among these, sodium dithionite was found to be excellent in action for selectively folding out as copper metal copper. In addition, sodium dithionite is the most excellent reducing agent in terms of the effect of treating the remaining liquid after recovering the metal copper that has been folded out in the next step and the ease of draining the treated water from the final step. It is.

In addition, depending on the addition amount of the reducing agent, there is an additive capable of sequentially depositing a plurality of metals. For example, when hydrazine-hydrate is added to acidic mining wastewater containing copper ions, zinc ions and iron ions, copper is first precipitated, and when hydrazine-hydrate is further added, iron is precipitated.
Further, when the composition of the aqueous solution is different, the pH and the amount of the reducing agent added for precipitation may be different. In order to determine the pH and the amount of reducing agent added for precipitation in each composition, it can be easily determined by conducting a small experiment in advance.

  Hereinafter, a method for treating acidic mine wastewater that precipitates and collects copper ions, zinc ions, and iron ions contained in the acidic mine wastewater as individual metals or their compounds will be described in detail.

  The treatment method of acid mine drainage water containing copper ions, zinc ions and iron ions is completely different from the conventional treatment method. In the first container, reduction treatment is carried out in the presence of a reducing agent, and only copper ions are converted into metal. It is the processing method of acidic mine wastewater characterized by depositing and collect | recovering as copper.

  Here, the degree of the reduction treatment can be indicated by the DO value in the aqueous solution. The smaller the DO value, the better, but generally it is practical to keep it at 5 mg / L or less, preferably 1 mg / L or less, particularly preferably 0.3 mg / L or less.

Examples of the reducing agent include sodium dithionite (Na ₂ S ₂ O ₄ ), sodium bisulfite (NaHSO ₃ ), sodium sulfite (Na ₂ SO ₃ ), hydrazine-hydrate (N ₂ H ₄ .H _2). When O), 1-amino-4-methylpiperazine, sodium erythorbate, and the like were added, although there was a slight difference in reactivity depending on the type of metal ion, a reduction action was recognized in all cases.

  Among these reducing agents, sodium dithionite and hydrazine have good reactivity, especially the reactivity with copper ions, and it is recognized that copper ions fold out with high yield as metallic copper. It was. Among these, sodium dithionite was found to be excellent in action for selectively folding out as copper metal copper. In addition, sodium dithionite is the most excellent reducing agent in terms of the effect of treating the remaining liquid after recovering the metal copper that has been folded out in the next step and the ease of draining the treated water from the final step. It is.

In the first container, if the acidic mine wastewater is reduced in the presence of a reducing agent, copper ions break out as metallic copper, and the pH of the mine wastewater is about 2.0 to 3.5, preferably Is advantageously adjusted to about 2.5 to 3.3. When adding a base to adjust the pH, sodium hydroxide (NaOH) is usually used. The reduction treatment, even when the first oxygen molecule in the gas phase portion in the container (O ₂₎ is present, but may not be present, it is preferred to carried out in the absence. Therefore, an oxygen molecule blocking agent (for example, liquid paraffin is used at the gas-liquid interface in order to prevent oxygen molecules from being dissolved from the gas phase portion to the liquid phase portion in accordance with Henry's law. ) May be present.

The amount of the reducing agent to be added depends on the type, but the amount varies depending on the type of acid mine wastewater and the concentration of copper ions. The preferred amount can be confirmed by simple experiments. When sodium dithionite (Na ₂ S ₂ O ₄ ) is used as the reducing agent, its concentration is advantageously 50 ppm or more in the acid mine drainage, preferably about 70-200 ppm, particularly preferred Is practically in the range of about 80-170 ppm.

Since sodium nithionite is a powder with high water absorption, there is a possibility that the supply pipe may be blocked due to consolidation in practical use. In order to solve this problem, it has been confirmed that the same effect can be obtained when sodium nitrite powder is added in a suspension or slurry state in an organic solvent of ethyl alcohol or acetone in advance. Further, in some cases the suspended directly at a high concentration in water of sodium dithionite is not available because the decomposition.

  By the treatment method described above, copper ions break out from the acid mine wastewater as metallic copper, so that copper (Cu) can be recovered by solid-liquid separation. Hereinafter, this process may be abbreviated as “Cu recovery process”. The recovered copper has a high purity, and the recovery rate is as high as 90% or more.

In the aqueous solution after separating the copper metal, most of the zinc ions and iron ions remain, and other metal ions are contained. While maintaining the reducing atmosphere, the aqueous solution separated from the Cu recovery step adds a base and raises the pH to 7.5 to 8.5 in the second container, thereby converting zinc ions into white water. It can be precipitated and recovered as an oxide (Zn (OH) ₂ ). Hereinafter, this process may be abbreviated as “Zn recovery process”.

  In this Zn recovery step, in order to obtain a reducing atmosphere, the gas phase portion is replaced with a gas phase that does not contain oxygen molecules (for example, nitrogen gas, argon gas), or / and further from the gas phase portion according to Henry's law In order to prevent oxygen molecules from dissolving in the phase part, it is advantageous to have an oxygen molecule blocking agent present at the gas-liquid interface. As an oxygen molecule blocking agent, it is easy to use fluidized paline.

In the Zn recovery step, if the oxidizing atmosphere is not used in the reducing atmosphere, the divalent iron ion Fe ²⁺ is preferentially oxidized before the Zn (OH) ₂ is precipitated to become the trivalent iron ion Fe ³⁺ . Due to the rise, ferric hydroxide Fe (OH) ₃ precipitates and precipitates, making it difficult to recover Zn (OH) ₂ alone. In addition, when ferric hydroxide is precipitated, the coprecipitation action with other metal ions is strong, so other metal ions are deposited at the same time, and it becomes impossible to collect not only zinc but also other metals alone. It is important to maintain a reducing atmosphere.

  The degree of oxidizing atmosphere in the Zn recovery step can be indicated by the DO value in the aqueous solution. The smaller the DO value, the better, but generally it is practical to keep it at 10 mg / L or less, preferably 2 mg / L or less, particularly preferably 0.3 mg / L or less.

In the Zn recovery step, zinc ions fold out and precipitate alone as zinc hydroxide (Zn (OH) ₂ ), which may be separated by solid-liquid separation. The recovered zinc hydroxide has the advantages of high purity and a high recovery rate.

  In addition, the order and pH of the metal hydroxides deposited may differ slightly depending on the type of metal ions contained in the second container and the amount dissolved, but the metal hydroxide precipitation equilibrium and various metal ion concentrations It can be easily determined by a small experiment based on literature such as the relationship of pH.

In the aqueous solution after separation of zinc hydroxide, iron ions and other metal ions remain. When the aqueous solution separated from the Zn recovery step is maintained in a reducing atmosphere and added with a base in the third container to raise the pH to 8.5 to 9.0, light green ferrous hydroxide ( Since Fe (OH) ₂ ) folds out and precipitates, it can be separated and recovered by solid-liquid separation. The recovered ferrous hydroxide has the advantages of high purity and high recovery rate.

In order to obtain a reducing atmosphere in the Fe (OH) ₂ recovery step, the gas phase portion is replaced with a gas phase that does not contain oxygen molecules (for example, nitrogen gas, argon gas), or / and further according to Henry's law. In order to prevent oxygen molecules from dissolving from the liquid part to the liquid phase part, it is advantageous to have an oxygen molecule blocking agent present at the gas-liquid interface. As an oxygen molecule blocking agent, it is easy to use fluidized paline.

In the Fe (OH) ₂ recovery step, the Fe ²⁺ ions dissolved in the oxidizing atmosphere are oxidized prior to the other metal ions in the oxidizing atmosphere, so that ferric hydroxide Fe (OH) ₃ is precipitated. It precipitates and it becomes difficult to recover Fe (OH) ₂ alone. Furthermore, when ferric hydroxide is precipitated, the coprecipitation with other metal ions is strong, so other metals also precipitate at the same time, and it is impossible to recover not only iron but also other metals alone. It is important to maintain the atmosphere.

The degree of the oxidizing atmosphere in the Fe (OH) ₂ recovery step can be indicated by the DO value in the aqueous solution. The smaller the DO value, the better, but generally it is practical to keep it at 10 mg / L or less, preferably 2 mg / L or less, particularly preferably 0.3 mg / L or less.

In the Fe recovery step, iron ions are separated and precipitated alone as ferrous hydroxide Fe (OH) ₂ , and may be separated by solid-liquid separation. The recovered iron hydroxide has an advantage that it has a relatively high purity and a high recovery rate.

  In addition, the order and pH of the metal hydroxides deposited may differ slightly depending on the type of metal ions contained in the third container and the amount dissolved, but the metal hydroxide precipitation equilibrium, various metal ion concentrations and pH It can be easily determined by a small experiment based on literature such as

As described above, it is explained that copper, zinc, and iron, which are valuable metals, from acid mine drainage mainly containing copper ions, zinc ions, and iron ions are completely separated from the conventional method and recovered and recovered in a reducing atmosphere. did.
In addition, the metal obtained by this method can be recovered with high purity and high recovery rate, and the process is simple and economical and practical.

When the amount of other metal ions remaining in the aqueous solution after separating Fe (OH) ₂ is very small, supplying air containing oxygen molecules before separating and recovering Fe (OH) ₂ makes it easy Fe ²⁺ can be oxidized to Fe ³⁺ . As a result, Fe (OH) ₃ is generated and precipitated, and other remaining metal ions can be almost precipitated by the strong coprecipitation action of Fe (OH) ₃ .

By subjecting the aqueous solution after separation and recovery of Fe (OH) ₃ and trace metals to post-treatment such as pH adjustment, it becomes possible to drain as clean water containing almost no harmful substances.

Further, since Fe (OH) ₂ does not have magnetizability, it is impossible to separate and collect the iron component using magnetizability.
Hereinafter, a method for separating and collecting iron components using magnetizability will be briefly described.

A part of the aqueous solution in which ferrous hydroxide was precipitated was added to a base in an oxidizing atmosphere in a fourth container to raise the pH to 9.0 to 9.3, and iron oxyhydroxide (FeOOH) was added. Fold it out. Next, an aqueous solution containing ferrous hydroxide obtained in the third container and an aqueous solution containing iron oxyhydroxide obtained in the fourth container have an iron molar ratio of 1: 1 to 2. : When a base is added in an oxidizing atmosphere in a fifth container so that the ratio becomes 3, and the pH is raised to 9.3 to 9.6, iron ions are converted to triiron tetroxide (Fe ₃ O ₄ ). Fold out. In the Fe ₃ O ₄ recovery step, the reaction in the fifth container is performed in an oxidizing atmosphere in the presence of an oxidizing agent. Therefore, in the fifth container, it is desirable to fill the gas phase part with a gas (preferably air) containing oxygen molecules (O ₂ ) and adjust the pH while stirring. It is preferable to use sodium hydroxide as the base. As mentioned above, the process of depositing and recovering iron may be abbreviated as “Fe recovery process”.

In the Fe recovery step, it is industrially valuable that iron ions are finally broken out as triiron tetroxide (Fe ₃ O ₄ ). That is, the folded iron trioxide is strongly bound to the magnet by magnetic adsorption, and can be easily recovered while being distinguished from other metals. That is, when the magnetized iron trioxide is inserted into the fifth container (for example, a neodymium magnet), the iron trioxide is selectively attracted to the magnet and easily recovered. By using a magnet, the Fe component can be easily separated with high purity and high recovery as iron trioxide.

  In the method of the present invention, after recovering the iron component in the Fe recovery step, the aqueous solution may contain other metal components. Therefore, in that case, ferrous hydroxide recovered in the Fe recovery step is added to the aqueous solution, and this is oxidized to further increase PH by coprecipitation of ferric hydroxide. It is desirable to remove residual metal ions as necessary by conventional techniques such as the use of a chelating agent and discharge it as clean water that can be drained.

  As described above, the solid / liquid separation in each step in the method of the present invention can be carried out by various operations as long as it is a means for separating a normal solid and a liquid. For example, the liquid in the supernatant may be removed from the solid component that has been folded or precipitated, or a solid / liquid separation method using a filter may be used. Further, the pH adjustment, stirring and separation operations in each step do not require special temperature control, and can be performed at room temperature, for example, 5 to 40 ° C., preferably 10 to 35 ° C.

Hereinafter, the method of the present invention will be described with reference to examples.
[Example]
Although the Example of the processing method of acidic mine wastewater of this invention is given, this invention is not limited to a following example.
The acid mine wastewater used in this example was artificially prepared in the laboratory while correlating with the acid mine wastewater discharged from mines in various places.

水溶液１〜４にそれぞれ試薬第一級の亜ニチオン酸ナトリウム（Ｎａ_２Ｓ_２Ｏ_４）の粉末を１２０ｐｐｍ添加した結果、各水溶液のＤＯは０．１〜０．３ｍｇ／Ｌとなり、直ちに金属銅が析出した。析出した銅を濾過分別・乾燥し、回収率を算出した結果を表２に示した。また、銅以外の金属の沈殿は見られなかった。 Examples 1-2 and Comparative Examples 1-2
(Recovery of metallic copper by sodium dithionite)
The aqueous solutions in Table 1 were obtained using reagent primary copper sulfate CuSO ₄ , zinc sulfate ZnSO ₄ and ferrous sulfate FeSO ₄ to prepare acidic mine wastewater. The pH of the aqueous solution at the time of preparation and DO (mg / L) are shown together in Table 1.

As a result of adding 120 ppm of a primary reagent sodium nitrite (Na ₂ S ₂ O ₄ ) powder to each of the aqueous solutions 1 to 4, the DO of each aqueous solution was 0.1 to 0.3 mg / L, and the copper metal was immediately added. Precipitated. The precipitated copper was separated by filtration and dried, and the results of calculating the recovery rate are shown in Table 2. Moreover, precipitation of metals other than copper was not seen.

また、実施例１〜２において、亜ニチオン酸ナトリウムの粉末を少量のエチルアルコールおよびアセトンに高濃度で懸濁もしくはスラリーの状態として添加しても、同様の結果を得た。

In Examples 1 and 2, similar results were obtained even when sodium nithionite powder was added in a small amount of ethyl alcohol and acetone in a suspended or slurry state at a high concentration.

Examples 3-6
(Recovery of copper and iron with hydrazine)
Reagent primary liquid paraffin was added to the aqueous solution described in Table 3 as an oxygen molecule blocking agent so as to have a thickness of about 5 mm on the water surface, and then the reagent primary concentration of 200 mg / L hydrazine monohydrate. A Japanese product (N ₂ H ₄ .H ₂ O) was added, and copper and iron could be precipitated and separated. The results are shown in Table 3. It can be seen that when the composition of the aqueous solution is different, the amount of hydrazine monohydrate added for precipitation is different.

Example 7
(Zinc recovery)
As described in Table 4, the reagent primary liquid paraffin was added to the gas-liquid interface to a thickness of about 5 mm as an oxygen molecule blocking agent in the aqueous solution after copper was separated and recovered in Example 2. did. The DO of the aqueous solution at this time was 0.2 mg / L. Next, when a reagent primary sodium hydroxide aqueous solution with a concentration of 2.5 × 10 ⁻² mol / L is added and the pH is 8.0, white Zn (OH) ₂ precipitates and Zn can be separated and recovered. did it. The recovery rate of Zn at this time was 96.5%.
Comparative Examples 3-4
In addition, when treated in the same manner as in Example 4 except that liquid paraffin is not added and air is forcibly blown from the bottom of the container and supplied in the form of bubbles, precipitation of yellow to reddish brown Fe (OH) ₃ occurs. Zn (OH) ₂ precipitated and Zn could not be separated and recovered alone. The results are shown in Table 4.

Example 8
(Recovery of ferrous hydroxide)
Reagent primary liquid paraffin was added to the water surface so as to have a thickness of about 5 mm as an oxygen molecule blocking agent in the aqueous solution obtained after separating and recovering Zn (OH) ₂ in Example 4. The DO of the aqueous solution at this time was 0.1 mg / L. Next, a reagent primary sodium hydroxide aqueous solution having a concentration of 2.5 × 10 ⁻² mol / L was added to adjust the pH to 8.5 to precipitate light green Fe (OH) ₂ (aqueous solution-1). When the yield at this time was calculated, it was Fe (OH) ₂ corresponding to 81.5% of iron content as prepared in Example 2.

Example 9
(Recovery of Fe ₃ O ₄ )
A half amount of the solution-1 obtained in Example 8 was dispensed into a separate container, and air was introduced to create an oxidizing atmosphere, and the reagent primary water having a concentration of 2.5 × 10 ⁻² mol / L. An aqueous sodium oxide solution was added to adjust the pH to 9.0, and iron oxyhydroxide FeOOH was precipitated (aqueous solution-2).
The aqueous solution-1 and the aqueous solution-2 were mixed in separate containers, and an oxidizing atmosphere was maintained to precipitate fine black Fe ₃ O ₄ . A neodymium magnet wrapped in a polyethylene bag was put into this aqueous solution, and Fe ₃ O ₄ was magnetically adsorbed / taken out, washed and dried, and the yield was calculated to be 72.3% of the iron content as prepared in Example 2. The corresponding Fe ₃ O ₄ could be selected.

Claims (5)

(A) Acidic mining wastewater containing at least copper ions and iron ions and / or zinc ions is reduced in the presence of a reducing agent in the first container to deposit and recover metallic copper , (B) A base is added in the second container while keeping the aqueous solution obtained after depositing and recovering metallic copper in the first container in a reducing atmosphere, and iron ions and / or zinc ions are added to the water. A method for treating acid mine wastewater that precipitates and collects as oxides. (A) At least acid copper wastewater containing copper ions, iron ions and zinc ions is reduced in the presence of a reducing agent in the first container to deposit and recover metallic copper ; A base is added in the second container while keeping the aqueous solution obtained after the copper is deposited and recovered in the first container in a reducing atmosphere, and zinc ions are precipitated and recovered as hydroxides. c) A base was added in the third container while maintaining the aqueous solution obtained after precipitation and recovery of zinc ions as hydroxides in the second container in a reducing atmosphere, and ferrous hydroxide Fe (OH) ) Acid mine wastewater treatment method for precipitating and collecting ₂ . The acidic mine according to any one of claims 1 to 2, wherein the reducing atmosphere is such that oxygen molecules are not present in the gas phase portion of the container and / or an oxygen molecule blocking agent is used at the gas-liquid interface. Wastewater treatment method. The method for treating acidic mine wastewater according to claim 3 , wherein the oxygen molecule blocking agent is liquid paraffin. Reducing agent is, processing method of acid mine drainage according to claim 1 which is sodium dithionite _{(Na 2 S 2 O 4)} .