JP2006334492A - Method for treating selenium-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating selenium-containing water, in which selenium can be easily removed from selenium-containing water at a high recovery rate and at a low cost and a selenium-containing compound can be efficiently separated/recovered from selenium-containing water. <P>SOLUTION: The method for treating selenium-containing water comprise the steps of: adding copper powder or a copper compound to the selenium-containing water to be produced at a smelting step to exude/reduce selenium by copper; adding metal powder such as Fe powder and Zn powder having the ionization tendency larger than that of copper to produce/recover a precipitate, namely, to remove selenium together with copper. The recovered precipitate is used as a raw material for a flash smelting furnace to recover selenium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for treating selenium-containing water, and more particularly, to a method for treating selenium-containing water such as selenium-containing wastewater discharged from a smelting process or a selenium production / processing process.

  Conventionally, as a method for treating selenium-containing water, there are known an iron powder replacement treatment method, a reduction treatment method using divalent iron, a coprecipitation method using trivalent iron, and the like. With the revision of the Ordinance on Enforcement of the Pollution Control Act, the selenium drainage standard was stipulated to be 0.1 mg / L or less, and the development of treatment technology with high selenium removal capability has been promoted.

  In recent years, as a method having a high ability to remove selenium, divalent iron ions are added to selenium-containing wastewater under weak acidity, and the redox potential of the liquid is lowered to a very low potential level using a reducing agent, and then rapidly. There has been proposed a method of removing selenium by performing neutralization treatment to crystallize divalent iron ions as iron hydroxide, neutralization treatment, and solid-liquid separation (see, for example, Patent Document 1). In addition, as another method, a method of adding a metal salt that reacts with selenium to form a hardly soluble salt to selenium-containing water, a method of bringing selenium-containing water into contact with biological sludge in an anaerobic state, and precipitating and removing selenium compounds, A method of removing metal and selenium from the flue gas desulfurization wastewater by contacting a metal such as Fe with the flue gas desulfurization wastewater, a method of adsorbing selenium to an ion exchange resin or a chelate resin, and adding a copper salt to the selenium-containing liquid After that, a method for removing selenium by adding an alkali to separate aggregates and a method for removing selenium as a precipitate from a hexavalent selenium-containing wastewater in the presence of a transition metal compound and a reducing agent have been proposed. (For example, refer to Patent Documents 2 to 7).

JP-A-8-224585 (paragraph numbers 0006-0007) JP-A-5-78105 (paragraph number 0010) JP-A-8-323392 (paragraph numbers 0004-0006) JP-A-9-47790 (paragraph numbers 0010-0011) Japanese Patent Application Laid-Open No. 10-137753 (paragraph number 0006) JP 11-57746 A (paragraph number 0008) JP-A-8-132074 (paragraph number 0007)

  As described above, various methods for safely separating selenium in waste water and detoxifying it in accordance with strict emission regulations have been proposed. However, these methods have excessive facilities to increase the recovery efficiency of selenium when a large amount of precipitate other than selenium remains or the desired selenium removal rate cannot be obtained due to restrictions on the target wastewater. There are problems such as being necessary, expensive reagents used, and complicated processes. There is also a problem that the recovered selenium cannot be separated into a usable state as a raw material for non-ferrous metal smelting.

  Therefore, in view of such conventional problems, the present invention can easily and inexpensively remove selenium from selenium-containing water at a high removal rate, and efficiently separate selenium-containing compounds from selenium-containing water. It is an object of the present invention to provide a method for treating selenium-containing water that can be recovered.

  As a result of diligent research to solve the above problems, the present inventors have added copper or a compound thereof to selenium-containing water, and then added a metal powder having a higher ionization tendency than copper to generate a precipitate. Thus, it has been found that selenium can be easily and inexpensively removed from selenium-containing water at a high removal rate and that selenium-containing compounds can be efficiently separated and recovered from selenium-containing water. It came to be completed.

  That is, the method for treating selenium-containing water according to the present invention is characterized in that after adding copper or a compound thereof to selenium-containing water, a metal powder having a higher ionization tendency than copper is added to generate a precipitate. . In this selenium-containing water treatment method, metals having a higher ionization tendency than copper (Cu) are aluminum (Al), zinc (Zn), iron (Fe), nickel (Ni), cobalt (Co), tin (Sn). And a metal selected from the group consisting of lead (Pb). Moreover, it is preferable that the quantity of the copper added to selenium containing water is 0.5 to 1.5 weight part with respect to 1 weight part of selenium (Se) in selenium containing water, and 0.7 to 1.2 weight. More preferably, it is part. Further, copper or a compound thereof is preferably copper powder or a sulfate, nitrate or chloride thereof, or an electrolytic solution used in a smelting process. Further, when adding a metal powder having a higher ionization tendency than copper, the oxidation-reduction potential (Ag / AgCl electrode (silver / silver chloride electrode)) is preferably +50 to −400 mV, and −100 to −300 mV. More preferably. Furthermore, the Se concentration in the selenium-containing water is preferably 5 mg / L or more.

  In the present specification, “metal powder” refers to metal particles having a particle size of several μm to several mm, and a metal powder having a particle size of several μm may be supported on a carrier. Any form that is included and can contact the selenium-containing water is acceptable.

  According to the present invention, selenium can be easily and inexpensively removed from selenium-containing water at a high removal rate, and a compound containing selenium can be efficiently separated and recovered from selenium-containing water.

  Embodiments of a method for treating selenium-containing water according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a process diagram illustrating one embodiment of a method for treating selenium-containing water according to the present invention. As shown in FIG. 1, first, selenium-containing wastewater discharged from the smelting process is prepared as selenium-containing water to be treated. This selenium-containing wastewater contains, for example, about 90% of tetravalent Se ions and about 10% of hexavalent Se ions as Se ions.

Next, Cu powder or copper sulfate (CuSO ₄ ) is added to the selenium-containing waste water. When Cu powder is added, selenium is reduced and the Se concentration in the selenium-containing wastewater becomes about 50%. On the other hand, even if CuSO ₄ is added, the Se concentration in the selenium-containing wastewater does not change. In addition, it is preferable that the quantity of Cu powder added here is 0.5-1.5 weight part with respect to 1 weight part of selenium in selenium containing water, and is 0.7-1.2 weight part. Is more preferable.

  Next, when a metal powder having a higher ionization tendency than copper, such as Fe powder or Zn powder, is added to the selenium-containing wastewater, the reduction potential is lowered by cementation, causing a substitution reaction, and a precipitate is generated. The amount of metal powder added to cause this cementation is determined by the amount of added Cu powder and needs to be 1 molar equivalent or more with respect to Cu. .1 molar equivalent or more is preferred. However, if it is 2.0 molar equivalents or more, the potential is lowered more than necessary, leading to an increase in cost associated with an increase in the amount of metal powder added, and the purity of precipitated Cu is reduced (metal powder for cementation). This is not preferable because the undissolved residue is contaminated). Therefore, it is preferable that the addition amount of a metal powder is 1.0-2.0 molar equivalent with respect to Cu, and it is further more preferable that it is 1.1-1.5 molar equivalent. When this metal powder is added, the oxidation-reduction potential (Ag / AgCl electrode) is preferably +50 to −400 mV, more preferably −100 to −300 mV. In addition, the liquid temperature at this time should just be 0 degreeC or more and less than 100 degreeC, it is preferable that it is 10-60 degreeC, and room temperature may be sufficient without heating especially.

Thus, in order to remove copper from selenium-containing wastewater to which Cu powder or CuSO ₄ is added, a metal powder having a higher ionization tendency than copper is added and the potential is controlled and lowered by cementation. Selenium can be removed simultaneously. In the case of non-ferrous smelting, it is preferable to use iron powder or zinc as the metal that causes such cementation. If iron powder or zinc powder is used, even if it becomes a residue after treating the selenium-containing water, it can be used in other processes, or no special equipment is required for the subsequent treatment, which is costly. Is advantageous. In addition, if it is a metal with a larger ionization tendency than copper, it can remove copper by a substitution reaction.

  Next, solid-liquid separation is performed after the addition of the above metal. The produced | generated deposit is a starch containing Cu and Se, and can be used as a smelting raw material.

Next, Se can be precipitated and removed by adding a barium (Ba) salt such as barium chloride (BaCl ₂ ) to the solution to form a hardly soluble Ba salt. The excessively charged BaCl ₂ can be removed as a BaSO ₄ salt by adding sulfuric acid (H ₂ SO ₄ ) or sodium sulfate (Na ₂ SO ₄ ) in order to return the pH of the solution to neutrality. The precipitate can be returned to the flash furnace as a slag raw material. Thus, the raw material thrown into a flash furnace is isolate | separated by carrying out solid-liquid separation with the precipitate produced | generated by a cementation process.

The addition amount of Ba ions is determined by the Se concentration and the SO ₄ concentration. When the concentration of these ions is unknown, the amount of excess Ba ions added can be minimized by measuring the electrical conductivity. For example, when BaCl ₂ is added, since the Ba salt is precipitated first, the electrical conductivity does not increase greatly. However, when excess BaCl ₂ is added, it is due to Ba ²⁺ ions and Cl ⁻ ions. The electrical conductivity increases.

  Hereinafter, the Example of the processing method of selenium containing water by this invention is described in detail.

[Example 1]
First, as shown in Table 1, Se161.7 mg / L, Cu 0.5 mg / L, Pb 1.21 mg / L, Zn 4.3 mg / L, Fe 2.49 mg / L, As (arsenic) 682.3 mg / L, Hg 1 mL of selenium-containing wastewater containing 1.6 μg / L (mercury), pH-0.01, oxidation-reduction potential (ORP) (Ag / AgCl electrode) 370 mV was weighed into a beaker.

  Next, 10 g of reagent (special grade) copper powder was added to the selenium-containing wastewater, and a propeller blade having a diameter of 30 mm was rotated at 400 rpm at room temperature and stirred for 60 minutes. Next, in order to remove undissolved components and solid components, suction filtration was performed using 5C filter paper, and the filtrate was analyzed. The results are shown in Table 1.

  Reagent iron powder 10.67 g was added to 1 L of a solution in which copper thus obtained was slightly dissolved. The potential was lowered by the addition of this iron powder, and after stirring for 15 minutes, suction filtration was performed and the filtrate was analyzed. The results are shown in Table 1. As shown in Table 1, it can be seen that when iron powder is added to remove copper after adding copper powder, copper is removed and selenium is removed at the same time.

[Example 2]
12.33 g of reagent zinc powder was added to 1 L of a liquid in which copper obtained in the same manner as in Example 1 was slightly dissolved. The potential was lowered by the addition of the zinc powder, and after stirring for 15 minutes, suction filtration was performed and the filtrate was analyzed. The results are shown in Table 1. As shown in Table 1, it is understood that when zinc powder is added to remove copper after adding copper powder, selenium is removed at the same time as copper is removed.

[Example 3]
11.79 g of the reagent CuSO ₄ .5H ₂ O was added to the same selenium-containing wastewater as in Example 1, and a propeller blade having a diameter of 30 mm was rotated at 400 rpm at room temperature and stirred for 15 minutes. Although it seemed to be completely dissolved by the naked eye, suction filtration was performed using 5C filter paper, and the filtrate was analyzed. The results are shown in Table 1. As shown in Table 1, it can be seen that the concentration of selenium does not change only by adding copper ions.

  Reagent iron powder 7.91 g was added to 1 L of the solution in which the copper sulfate thus obtained was dissolved. The potential was lowered by the addition of this iron powder, and after stirring for 15 minutes, suction filtration was performed and the filtrate was analyzed. The results are shown in Table 1. As shown in Table 1, it can be seen that when iron powder is added to remove copper after adding copper sulfate, selenium is removed at the same time as copper is removed.

[Example 4]
9.26 g of reagent zinc powder was added to 1 L of a solution obtained by refining copper sulfate obtained in the same manner as in Example 3. The potential was lowered by the addition of the zinc powder, and after stirring for 15 minutes, suction filtration was performed and the filtrate was analyzed. The results are shown in Table 1. As shown in Table 1, it is understood that when zinc powder is added to remove copper after adding copper sulfate, copper is removed and selenium is also removed at the same time.

It is process drawing of embodiment of the processing method of selenium containing water by this invention.

Claims (7)

A method for treating selenium-containing water, comprising adding copper or a compound thereof to selenium-containing water and then adding a metal powder having a higher ionization tendency than copper to generate a precipitate. The treatment of selenium-containing water according to claim 1, wherein the metal having a higher ionization tendency than copper is a metal selected from the group consisting of Al, Zn, Fe, Ni, Co, Sn, and Pb. Method. The amount of copper to be added to the selenium-containing water is 0.5 to 1.5 parts by weight with respect to 1 part by weight of selenium in the selenium-containing water. A method for treating selenium-containing water. The method for treating selenium-containing water according to any one of claims 1 to 3, wherein the copper or a compound thereof is copper powder or a sulfate, nitrate or chloride thereof. The method for treating selenium-containing water according to any one of claims 1 to 3, wherein the copper or a compound thereof is an electrolytic solution used in a smelting process. 6. The oxidation-reduction potential (Ag / AgCl electrode) is set to +50 to −400 mV when the metal powder having a higher ionization tendency than copper is added. 6. A method for treating selenium-containing water. The method for treating selenium-containing water according to any one of claims 1 to 6, wherein the Se concentration in the selenium-containing water is 5 mg / L or more.

Images