WO1998050304A1

WO1998050304A1 - Method for treating selenium-containing solution

Info

Publication number: WO1998050304A1
Application number: PCT/JP1998/002033
Authority: WO
Inventors: Junya Watanabe; Katsuhiko Yano; Koji Kusabe; Tatsuya Sakurai
Original assignee: Mitsubishi Chemical Corporation; Kawasaki Kasei Chemicals Ltd.
Priority date: 1997-05-08
Filing date: 1998-05-07
Publication date: 1998-11-12

Abstract

A method for the disposal of waste water containing selenium and inorganic acid salts having a buffering action around a neutral region, such as alkali metal sulphates and boron compounds, in a simple treatment manner with good efficiency and for effectively reducing the concentration of selenium in the waste water in a short time. The method for treating a selenium-containing solution comprises passing a solution containing selenium and inorganic acid salts of other metals through a packed bed of an iron-base metal to precipitate selenium on the surface of the iron-base metal, wherein the solution is brought into contact with the iron-base metal at a temperature of 30 °C or above preferably at a pH ranging from 3 to 7 and, if necessary, the compounds having buffer action around a neutral region and contained in the waste water is removed before the contact of the solution with the iron-base metal.

Description

Description Processing method of selenium-containing solution

The present invention relates to a method for treating a selenium-containing solution and efficiently reducing the selenium concentration in the solution or recovering selenium. Background art

Selenium and selenium compounds are used in a variety of manufacturing industries, such as glass decolorizing agents, photocopier photoconductors, rectifiers, semiconductor materials, battery materials, and electrolytic coloring agents for metals such as aluminum. The wastewater discharged from the manufacturing process usually contains a relatively high concentration of selenium. Selenium is also present in wastewater from selenium refinery factories and selenium compound manufacturing factories. Furthermore, selenium has been found to be present in the wastewater discharged from thermal power plants. Since selenium is a very toxic environmental pollutant, its amount in the effluent is strictly regulated, and in recent years its allowable amount has been stricter, and the effluent standard has been set at 0.1 to 0.1 mg / l. It has been.

As a method of recovering selenium, generally, a neutralization coagulation precipitation method, an iron hydroxide precipitation method, a funilite precipitation method, an ion exchange membrane method, an activated carbon adsorption method and the like are known. However, these methods require special equipment and equipment for the combined use of multiple treatment methods in order to efficiently remove selenium. Disadvantageous.

A method is known in which iron or an iron-based metal is added to wastewater and selenium is precipitated on the surface of the iron or iron-based metal (see US Pat. No. 4,405,464 and JP-A-7-2502). I have. However, while this method of using ferrous metal is an effective means for removing selenium compounds, it takes not only a long time to reduce a large amount of wastewater to a very low standard concentration, but also a long time. Handling heavy iron metal was also difficult. In particular, in a system containing a large amount of coexisting salts other than selenium, problems such as a decrease in the reaction rate may occur. As a countermeasure, it is conceivable to remove all the coexisting salt components, but it is not realistic to reduce the total coexisting salt amount when the coexisting salt is present in a large amount.

Among the selenium compound-containing waste liquids, one of the systems containing a large amount of coexisting salts is flue gas desulfurization wastewater from coal-fired power plants. It is known that various types of coexistence exist in the wastewater of coal-fired power plants, as shown on page 1083 of Vol. 35 No. 10 (1984) of Thermal Power Nuclear Power. It is not yet known which component of these coexistences has a large contribution.

When large amounts of coexisting salts are present, such as in the flue gas desulfurization effluent of coal-fired power plants, there is a need for a method to remove selenium compounds more efficiently.

On the other hand, a method is also known in which a reducing iron compound is added to a selenium-containing solution, the pH is adjusted, and a metal-collecting agent is added to recover selenium (see JP-A-9-59007). However, in this method, pH adjustment is required each time depending on the treatment process, so the operation is complicated and is not suitable as a large-scale wastewater treatment method.

The present inventors have conducted intensive studies with the aim of solving the above problems and providing a method for efficiently removing and recovering selenium in wastewater, and as a result, when depositing selenium on the surface of an iron-based metal, In some cases, the selenium concentration can be effectively reduced in a short period of time by removing the selenium compound after removing compounds that exhibit a buffering action near neutrality among the compounds other than selenium in the wastewater. They have found that they can be reduced, and have arrived at the present invention based on this finding. Disclosure of the invention

The gist of the present invention is that a solution containing selenium and another metal inorganic acid salt is allowed to flow through a packed bed of an iron-based metal to deposit selenium on the surface of the iron-based metal. The present invention relates to a method for treating a selenium-containing solution by contacting with a ferrous metal at a temperature of not less than ° C.

In a preferred aspect of the present invention, in the above treatment method, the pH value of the solution containing selenium and another metal inorganic acid is adjusted to 3 to 7; Being a sulfate of lithium earth metal; flowing a solution containing selenium and other metal inorganic acid in an upward flow through a bed of iron-based metal; When a solution containing another metal inorganic acid salt is brought into contact with a packed layer of an iron-based metal, the solution is maintained while maintaining the PH value of the solution in the packed layer at 3 to 7; selenium and other metals Adjusting the pH value of the solution containing the inorganic acid salt to 3 to 7 and contacting the pH-adjusted solution with the packed bed of iron-based metal a plurality of times; When a solution containing another metal inorganic acid salt is passed through a packed bed of iron-based metal, an acid is added to the packed bed to maintain the PH value of the solution in the bed at 3 to 7. In another embodiment, a solution containing selenium and other metal inorganic acid salts and a dilute acid are added to a reaction vessel containing an iron-based metal, and the pH value is adjusted to 3 to 7 This is a method for treating a selenium-containing solution by subjecting it to a contact reaction at a temperature of 30 ° C or higher while stirring while maintaining the temperature.

In another preferred embodiment of the present invention, in the above-mentioned treatment method, the iron-based metal is fibrous, porous, fine plate-like, granular, or powdery; the iron-based metal is fibrous; The ferrous metal is fibrous by a cutting method; the ferrous metal is fibrous with a diameter of 0.1 to 0.3 mm; the ferrous metal is steel wool; The iron-based metal must be porous; the iron-based metal must be iron having a surface area of at least 0.001 m ² Zg; and the iron-based metal has an iron surface area of 0.0 per column volume. 0.1 m ² Zm 1 or more iron; This is a method in which the amount of iron-based metal supported on the column is from 0.01 gZm 1 to 3 gZm 1.

Preferred treatment solutions for the method of the present invention include a solution containing selenium and another metal inorganic acid salt containing a sulfate ion having a concentration of 100 times or more the selenium concentration; The solution containing a metal inorganic acid salt of (a) contains a weak acid strong base salt, a strong acid weak base salt, a weak acid weak base salt and / or a metal complex salt; a weak acid strong base salt, a strong acid weak base salt, a weak acid weak base salt and The Z or metal complex salt may be an ammonium salt, a carbonate, a phosphate, a borate, a carboxylate, an aluminum complex, a copper complex, a cobalt complex and a Z or iron complex.

The present invention provides a solution containing selenium and another metal inorganic acid salt at a temperature of 30 ° C. or more, and flows through a packed layer of an iron-based metal to precipitate selenium on the surface of the iron-based metal. A method of treating a selenium-containing solution, comprising a step of incinerating or recovering selenium deposited on the surface of the iron-based metal by incineration or stripping treatment. Contact or ultrasonic treatment; regenerating the iron-based metal by contact with a dilute acid or ultrasonic treatment. In addition, a solution containing selenium and other metal inorganic acid salts is used. A step of flowing a packed bed of iron-based metal at a temperature of 30 ° C. or more to precipitate selenium on the surface of the iron-based metal, and subjecting selenium deposited on the surface of the iron-based metal to incineration or peeling treatment The present invention also provides a treatment method comprising a step of recovering and recovering the solution and a step of increasing the solution temperature in accordance with the decrease in the selenium recovery ability in the step, decreasing the pH value of the solution, and decreasing the flow rate of the solution or solution. Included in the method.

In another preferred embodiment of the present invention, when a solution containing a selenium compound and containing a compound exhibiting a buffer action near neutrality is treated, a buffer action from the solution to near neutrality is obtained. A process for removing the compound represented by the formula: and contacting the solution with a treating agent capable of reducing and removing the selenium compound from neutral to acidic side to remove the selenium compound. Removes the selenium compound by contacting it with a treatment agent composed of an iron-based metal that has the ability to reduce and remove the selenium compound from the neutral to the acidic side after the step of removing the compound exhibiting a buffering action near neutrality The treating agent having the ability to reduce and remove the selenium compound from neutral to acidic side is an iron-based metal; and the compound having a buffering action near neutral is a boron compound and Z or an aluminum compound; a compound exhibiting a buffering action near neutrality; a boron compound; removing a compound having a buffering action near neutrality using a boric acid selective resin; boric acid The selective resin is a glucamine-type chelating resin; the compound having a buffering action near neutrality is an aluminum compound, which includes a method comprising removing the aluminum compound by coagulation and precipitation; is there. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram illustrating a N a ₂ S 0 ₄ a (NH ₄₎ ₂ SC titration curve. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

The selenium-containing solution to be treated in the present invention is mainly a decolorizing agent for glass, copying Wastewater from various factories such as photoconductors, rectifiers, semiconductor materials, battery materials, aluminum, etc., wastewater from selenium refineries, selenium compound manufacturing plants, or thermal power plants The selenium contained therein exists as various selenium compounds depending on the source of the wastewater.For example, selenic acid, selenium dioxide, selenium trioxide, selenous acid, selenium tetrachloride, sodium selenide, selenide Selenium compounds such as potassium, ferrocene, copper selenide, nickel selenide, sodium selenite, potassium selenite, potassium selenite, barium selenite, etc., sodium selenate, potassium selenite, selenium Selenates such as barium acid; The selenium concentration in the solution also differs depending on the type of wastewater, but for example, wastewater from thermal power plants usually contains 0.2 to 5 ppm (as selenium).

In addition, these wastewaters usually contain inorganic salts of metals other than selenium. For example, alkali metals such as sodium sulfate, magnesium sulfate, sodium chloride, magnesium chloride, etc., and sulfuric acid of alkaline earth metals Heavy metal salts such as salts, chlorides, copper, chromium, and nickel are contained together with selenium, and it is effective to apply a solution containing these salts to the treatment method of the present invention. In particular, the solution containing selenium and other metal inorganic salts, which is the treatment liquid of the method of the present invention, is a solution containing sulfate ions having a concentration of 100 times or more the selenium concentration, and other metal inorganic acid salts other than selenium. Is preferably a sulfate of an alkaline metal or an alkaline earth metal.

When the pH value described below is controlled within a certain range, the solution containing a metal inorganic acid salt other than selenium may be a weak acid strong base salt, a strong acid weak base salt, or a weak acid weak base. the solution containing the salt and Z or metal complex salts, i.e., preferably has an acid dissociation constant is a solution containing a substance that is in the range of ^{^{1 0- 2 ~ 1 0- 1 ϋ}} . Examples of the weak acid strong base salt, strong acid weak base salt, weak acid weak base salt and / or metal complex salt include ammonium salt, carbonate, phosphate, borate, carboxylate, aluminum complex, copper complex, cobalt complex and It is preferred that the compound is either Ζ or an iron complex salt.

Furthermore, in the present invention, a solution containing the above-mentioned selenium and other metal inorganic acid salts is powerful, and is effective even when the solution contains a compound having a buffering action near neutrality. Compounds having an action generally include a weak acid strong base salt, a strong acid weak base salt, a weak acid weak base salt, a complex compound, or a metal ion compound forming a hydroxide. I can do it. Specifically, a compound ranging acid dissociation constant of 1 0 ² to 1 0 ^{1 2,} Anmoniumu salts, carbonates, phosphates, borates, carboxylates, aluminum complex salts, copper complex , Cobalt complex salts, iron complex salts, and metal hydroxides such as aluminum hydroxide. A selenium-containing solution in which such a substance is present causes a decrease in selenium removal ability due to contact with an iron-based metal.In the present invention, however, a step of removing these buffer components is performed by removing selenium as described later. By performing the removal step sequentially or simultaneously, a decrease in the selenium removal ability can be prevented.

The amount of the buffer component contained in the selenium-containing solution is preferably as small as possible, but is not particularly limited, and is preferably 100 ppm or less, more preferably 10 ppm or less.

Although it is not clear why the presence of the buffer component reduces the efficiency of selenium removal in the following steps, the pH of the solution increases due to the presence of the buffer component during contact with the iron-based metal, As a result, it is considered that the pH exceeds the neutral to acidic pH range at which the selenium compound can be optimally removed.

The pH value of the selenium-containing solution to be treated by the method of the present invention is usually adjusted in the range of 2 to 10, preferably 3 to 7, and particularly preferably 3 to 4. The lower the pH, the faster the removal of selenium by iron; therefore, the lower the pH, the better the reaction rate.However, when the pH is low, the reaction between iron and protons elutes iron ions. In addition to this, the amount of acid added for pH adjustment also increases. For this reason, a pH lower than 2 is not practical. On the other hand, when the pH exceeds 10, the reactivity decreases, and the effect of the present invention is not achieved, which is not preferable.

The pH is adjusted by using an acid or an alkali. As the acid, an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid or the like is used. As the alkali, sodium hydroxide, hydroxide hydroxide And the like.

In the present invention, an iron-based metal is used for precipitating selenium. Here, the iron-based metal includes pure metal iron and alloyed iron containing other metals such as chromium and manganese. is there. Specific examples of iron-based metals include electrolytic iron, low-carbon steel, medium-carbon steel, high-carbon steel, mild steel, mild steel, alloy steel, pig iron, gray iron, rimmed steel, capped steel, semi-killed steel, Examples include killed steel, clad steel, crude steel, and ingots. In the present invention, these ferrous metals can be used as molded products formed into a desired shape, but they are hot-rolled products, cold-rolled products, compressed products, extruded products, drawn products. , Plastic work, curtain, steel, etc.

The shape of the iron-based metal used in the present invention is not particularly limited. However, in the treatment method of the present invention, selenium in the solution is precipitated on the surface of the iron-based metal by a catalytic reduction reaction with the selenium-containing solution to be treated. It is desirable to have a shape having as large a contact surface area as possible, and further, a shape capable of easily forming a homogeneous packed bed when filled in a treatment tower is preferred. Specifically, a steel fibrous wire rod such as steel wool, a plate-like strip, a powdery substance, a granular substance, a fine chip, and the like are cited, and a steel wool is preferable. Plates have the drawback that it is difficult to pack them into columns and the surface area is small. In the case of granular and powdery materials, if the particle size is reduced, there is a problem of consolidation in the column. If the particle size is increased, the surface area cannot be increased. Further, there is a problem that the weight of the whole apparatus is increased because iron is filled most densely in the form of particles or powder.

Here, the fibrous material is easily used for adjusting the surface area and the filling density, and is optimally used. As the fibrous iron, iron having a small fiber diameter is suitable. The preferred fiber diameter is from 0 to 3 mm.

Examples of the method for processing the fibrous iron-based metal include a drawing method, a melt spinning method, and a cutting method. (Takeo Nakagawa et al., Textile Society Journal, Vol. 39, No. 4, pp. 121-127, 1983), but among them, those manufactured by the cutting method are preferable.

This seems to be due to the fact that a smaller fiber diameter can be manufactured by using the cutting method, and that the surface morphology of the fibrous metal obtained by the cutting method is suitable for selenium adsorption.

Here, the cutting method refers to cutting a metal block with a knife and discharging fine chips to obtain a desired shape.A fiber that uses these chips as fibers is a fibrous metal obtained by the cutting method. is there. A wire cutting method is a method for constantly cutting fibers having a finer cross section, and a typical example is the production of steel wool by the wire cutting method. This steel wool is most suitable for the selenium removal of the present invention.

Also, regardless of the shape of the iron, a porous material is advantageous in increasing the surface area, Since the filling density can be controlled, it is preferably used. The iron porous body can be manufactured by a sintering method, a plating method, a foaming method, a pressure forming method, or the like, and can be used with no particular limitation on the pore diameter, the pore shape, and the like.

Regarding the surface area of the iron-based metal, it is preferable that the surface area is not less than 0.001 lm ² Zg regardless of the shape of the iron. Since the reaction between iron and selenium proceeds from the iron surface, if the surface area of iron is small, the reaction rate is low and selenium cannot be removed efficiently. For the same reason, the surface area of the iron-based metal per column volume is also limited, and is preferably 0.001 m ² Zm 1 or more per column volume.

In addition, the amount of iron carried on the column is limited in terms of equipment. The specific gravity of iron is 7.86 g / cm ^3, which is much higher than the specific gravity of a carrier such as ordinary ion exchange resin, which is around 1. For this reason, special equipment that is different from equipment that normally carries ion exchange resins is required. Therefore, it is practical to reduce the amount of charge to the column. If the supported amount is too low, the selenium removability will be reduced. Therefore, it is preferably from 0.01 g / ml to 3 g Zml, more preferably from 0.05 g Zm 1 in terms of column volume. Not less than 1 g / m 1.

According to the method of the present invention, a packed bed formed by filling a treatment tower with an iron-based metal having an appropriate shape such as a fibrous, porous, granular, or powdery material is coated with selenium and other metal salts. The treatment solution is brought into contact by passing water to precipitate selenium on the surface of a metal such as iron.At this time, the contact treatment needs to be performed at 30 ° C or higher, and preferably 45 to 9 ° C. It is performed in a temperature range of 0 ° C. If the contact temperature is lower than 30 ° C, the reduction reaction of selenium with iron hardly proceeds, and it is difficult to recover and remove selenium from the solution. Further, it is not desirable to raise the temperature to an unnecessarily high temperature in terms of operability and economy, and in some cases, it may be affected by other components coexisting in the waste liquid.

Even if the contact temperature is controlled by maintaining the temperature inside the packed tower within a predetermined range by external heating, the contact temperature can be controlled by heating the solution to be treated to a predetermined temperature and supplying it to the packed tower. May be maintained.

Flow of the solution to be treated into the packed tower may be either a downward flow or an upward flow, but in order to make sufficient contact with the iron metal, the solution is passed upward from the bottom of the packed tower. Is preferred. The flow rate of the solution to be treated depends on the size of the packed tower, the type of iron-based metal, the processing conditions such as temperature, etc. Normally, SV (space velocity, unit: h— ') = 2 to 10 Operated on a range.

In the method of the present invention, temperature, pH, and SV are factors that determine the reaction rate of selenium removal. As already mentioned for the individual conditions, the higher the temperature, the lower the pH, the better and the lower the SV, the better the reaction rate. Setting these factors to improve the reaction speed as described above is a negative direction in terms of economy. Increasing the temperature and lowering the pH will increase the cost required for it, and lowering the SV will require more equipment as the throughput per unit time will decrease. For this reason, the operating conditions are selected according to the selenium concentration in the selenium-containing solution, the amount of the inorganic salt, the set value of the selenium concentration in the solution after the treatment, and the like.

As a method for bringing the pH of a solution containing selenium and another metal inorganic acid salt into contact with an iron-based metal while maintaining the pH in the contact layer at 3 to 7, generally, the pH of a stock solution is used. 3 to 4 and passed through a column packed with fibrous metal with a fiber diameter of 100 to 100 μm to a packing density of about 0.01 to 0.5 g / m1 at SV = about 1 to 10 Just liquid. If the pH cannot be kept in the range of 3 to 7 under these conditions due to the composition of the stock solution, the flow rate may be increased, or the iron filling amount or the surface area per unit volume of iron may be reduced.

As one method of carrying out the method of the present invention, a method of adjusting the pH of a solution containing selenium and other metal inorganic acid salts and adding the solution to a column filled with an iron-based metal can be mentioned. However, in general, when an iron-based metal is brought into contact with an acidic solution, the metal is consumed over time, and the PH value gradually rises, exceeding the range of 3 to 7, which is a pH at which selenium can be optimally removed. There are cases. In this case, even if the packed bed height of the column is increased without changing the flow rate of the solution or the packing density of the iron-based metal, selenium is not removed, and the iron-based metal is simply consumed unnecessarily. Therefore, by changing the concentration or flow rate of the iron-based metal in the column, the pH value in the column is maintained in the range of 3 to 7 in which selenium can be optimally removed, and selenium removal is performed in that state. It is preferred to do so.

In addition, metallic iron is first oxidized to Fe (II) upon contact with the selenium-containing solution, but in the region where the pH exceeds 7 in the contact layer, a precipitate of iron hydroxide (11) is formed. Precipitate is power An obstacle to Ram processing. Therefore, in this regard, it is preferable to control the pH value to 7 or less.

In the force ram method, increasing the flow rate of the solution or reducing the amount of the ferrous metal charged, in other words, reducing the pH increase in the contact layer and maintaining the pH in a suitable range, in other words, However, the surface area of the ferrous metal that is being filled may be reduced. According to this method, selenium can be removed while suppressing the amount of iron-based metal consumed, so that the processing amount of the selenium-containing solution per iron-based metal amount is large and efficient.

In the column method, when the pH value is controlled to 3 to 7 by this method, the operating conditions vary depending on the composition of the solution containing selenium and other metal inorganic acid salts and the buffering action. Conditions may be appropriately selected according to the conditions.

In particular, as described above, a solution containing a metal inorganic acid salt other than selenium is a solution containing a weak acid strong base salt, a strong acid weak base salt, a weak acid weak base salt and Z or a metal complex salt, that is, an acid. dissociation constant is 1 0 ² to 1 0 - If a solution containing a substance that is in the range of ^{1 Y} is often necessary to control the p H value occurs. In such a case, the consumption of metallic iron by acid increases even near neutrality, and the pH value often rises to 7 or more. In the region where the pH value is 7 or more, selenium is not removed, and only metallic iron is consumed, which is not economical. Therefore, when a substance having such a buffering action is present, it is particularly necessary to control the pH value to 3 to 7 as described above. This is because the pH behavior of a solution containing a weak acid strong base salt, a strong acid weak base salt, a weak acid weak base salt and Ζ or a metal complex salt is different from that of a strong acid strong base salt. In Figure 1 shows the慨形typical strong strong salt Motoshio type [N a ₂ S 0 _4] with a strong acid weak base salt form _{_{[(NH 4) 2 S 0}} J titration curve. In the present invention, it is preferable that a solution containing a metal inorganic acid salt other than selenium behaves similarly to the titration curve of the strong acid weak base salt type shown in FIG. Note that wastewater from thermal power plants often exhibits such behavior.

If the treatment with the ferrous metal in the solution containing selenium and other metal inorganic acid salts cannot reduce the selenium concentration to the specified selenium concentration by one ram treatment, the selenium and other selenium obtained in the primary treatment Readjust the pH value of the solution containing the metal inorganic acid salt to 3 to 7 and repeat the process consisting of pH adjustment of the solution and contact treatment several times so that it comes into contact with the iron-based metal layer. Thus, a desired value can be achieved. Usually, the operation Just repeat the process two or three times. Here, when the pH of the primary treatment water is adjusted and added to the packed bed column again, the column used for the primary treatment may be used, or may be added to another new column.

To obtain the same effect as performing a contact treatment with an iron-based metal packed bed multiple times using a single column, it is necessary to fill the iron-based metal packed bed with a selenium-containing solution when flowing it. A method in which the solution is passed while adding an acid to the 通 layer column can be used. In this case, the acid can be added from the upper part of the packed bed together with the selenium-containing solution.However, use a column in which the solution can be added from the middle of the packed bed as a packed bed, and add the acid from the middle of the column. Is preferred. There is no limitation on the number of portions to which the acid is added to the column, but usually 1 to 10 is appropriate. The concentration and amount of the acid to be added are most preferably controlled so that the pH value in the column is in the range of 3 to 7. The acid can be added continuously or intermittently.

The contact treatment with an iron-based metal can be performed not only by a column method using a packed bed of an iron-based metal but also by a batch method. In this case, a reaction vessel capable of stirring the iron-based metal is used, and a solution containing selenium and other metal inorganic acid salts and a dilute acid are added, and the mixture is stirred at a temperature of 30 ° C or more, so that p during the contact treatment is reduced. What is necessary is just to make it contact with ferrous metal, keeping H in the range of 3-7. In this case, the treatment can be performed by continuously discharging the treatment solution after the contact treatment from the reaction vessel while continuously supplying the solution containing selenium or the like and the acid to the reaction vessel.

Further, in the method of the present invention, the removal of selenium by the catalytic reduction reaction of selenium with iron is promoted by oxygen dissolved in the liquid to be treated, so that the contact treatment between a metal such as iron and the liquid to be treated is carried out by air. It is preferably performed in an oxygen-containing atmosphere such as

Further, as a preferred treatment solution in the method of the present invention, there is a flue gas desulfurization wastewater of a coal-fired power plant, which is a wastewater containing selenium and a buffer component. Generally, when such effluent is brought into contact with an iron-based metal to treat a selenium compound, it is more difficult to treat the selenium compound than effluent containing no other buffer components. Thermal Nuclear Power, Vol. 35, No. 10, (1984), p. 1083, shows an example of water quality of flue gas desulfurization effluent of a coal-fired power plant. According to this, F, there is a S 0 _4, C and Ca, Mg, Al, and B exist. Here, Al and B are substances that may have a buffering effect near neutrality. No. (1984), p. 1083, shows that A1 is present at 100 to 800 ppm and B is present at 10 to 130 ppm. This amount is sufficient to exhibit a buffering effect near neutrality, indicating that this component hinders the removal of selenium compounds from flue gas desulfurization effluent by contact with the selenium removing agent. The inventors have found out.

Then, after removing a boron compound and / or an aluminum compound, which exhibit a buffering action near neutrality from the wastewater containing selenium and are generally contained in the waste liquid, We have established a treatment agent that has the ability to reduce and remove selenium compounds from the neutral to acidic side, that is, a method that can efficiently remove selenium compounds by contact with iron-based metals.

Here, the boron compound is usually present in a solution in the form of a borate. For removing the boron compound, contact with a boric acid selective resin is effective. As a boric acid-selective resin, a glucamine-type chelating resin is commercially available. With this resin, boric acid can be selectively removed even in the presence of several thousand ppm of coexisting salt. A specific example is Diaion CRB02 manufactured by Mitsubishi Chemical Corporation. The contact method with the boric acid-selective resin may be a batch method or a column method, but is usually used in a column method. There are no particular restrictions on the pH, temperature, and flow rate during normal operation, but it is preferable that the contact be made at a pH of about 4 to 12, and the contact be made at a normal temperature and a flow rate of about SV1 to about 50. As for the removal of the aluminum compound, removal by a chelating resin, removal by coagulation and precipitation, etc. can be considered, but removal by coagulation and precipitation is effective. In the coagulation sedimentation method, the aluminum compound may be neutralized with an acid or an alkali, and the aluminum compound may be precipitated as a hydroxide, followed by solid-liquid separation.

The solution obtained above is then subjected to a step of removing a selenium compound. In the present invention, the selenium compound is removed by contacting the selenium compound with a treating agent capable of reducing and removing the selenium compound from the neutral to acidic side. Treatment agents capable of reducing and removing selenium compounds from the neutral to acidic side include iron-based metals, reducing agents such as hydrazine, thiourea, borohydride compounds, anthrahydroquinone, and resins carrying them. Other metals such as zinc and copper, and reducing salts such as copper (I) and Fe (II) salts. In the present invention, it is preferable to use an iron-based metal.

When contacting with ferrous metal, in this process, the type of ferrous metal and contact method It can be used without any particular limitation.For example, a ram method in which the ρ の of the solution obtained in the previous step is adjusted as necessary and added to a column filled with an iron-based metal as described above Can be adopted.

Selenium deposited on the surface of a metal such as iron by the method of the present invention can be recovered as metallic selenium by burning it. The method of incineration is not particularly limited, and any type of selenium can be easily recovered from the incineration residue such as a rotary incinerator such as a single kiln and a crucible-type incinerator. But it can be adopted. Further, a method in which a dilute acid is brought into contact with a metal surface on which selenium is deposited, and the separated selenium is recovered as a solid can also be adopted. In this case, 0.01 to 6 mL of hydrochloric acid may be passed through the column to separate solid selenium that separates with the dissolution of iron from the column.

It is also possible to adopt a method in which the selenium-adsorbed metal is removed from the column and brought into contact with HC1 in a range of 0.01 to 6Ν by a batch method to separate and recover solid selenium that is exfoliated with the dissolution of iron. it can. Here, if the iron component is completely dissolved with an acid, only selenium can be recovered as a high-purity element, but only by dissolving a part of the iron component, solid selenium is separated, It can be recovered. In general, solid selenium can be separated and recovered by dissolving 1% by weight or more of the iron component. Since solid selenium to be exfoliated is in powder form, iron-based metal and solid selenium can be separated only by separating fibrous or other massive iron from a mixture of both, and a magnetic separation method can also be used. .

Other methods include the separation of selenium coming off by ultrasonically treating the metal on which selenium is deposited, and the separation of selenium coming off by passing hot water through the metal on which selenium is deposited. No. Although there is no particular limitation in the ultrasonic treatment, a transmission frequency of 20 to 100 ° and a processing time of 1 to 30 minutes are preferably used. The higher the temperature, the more effective it is, but it can be used without particular limitation. Since the adsorption power of selenium on the metal surface is not strong, a method of separating selenium by some physical action is also used without limitation.

It has been found that the reactivity of iron-based metals used in the treatment of wastewater containing selenium gradually decreases. This is because solid reactions occur because the reaction is This is because the surface of the iron-based metal is covered with an inert reactant due to the precipitation of ren on the iron-based metal surface and the formation of iron oxide on the iron-based metal surface. Therefore, the reactivity of the iron-based metal is increased by contacting the selenium-adsorbed iron-based metal with a dilute acid or separating the solid selenium by ultrasonic treatment or the like. Therefore, selenium recovery methods such as contact with dilute acid and ultrasonic treatment also have the effect of regenerating ferrous metals. In particular, contact with dilute acid is effective for regenerating ferrous metals.

In addition, when the reactivity of selenium-containing wastewater decreases, the reactivity can be changed over time to prevent the decrease in reactivity. Regarding the reaction conditions, at the stage where the reactivity decreases, that is, at the stage where the leaked selenium concentration increases, raise the temperature after treatment, lower the pH of the processing solution, or lower the SV. Thus, the reactivity can be increased to the same level as before the decrease in reactivity. Changing these conditions is more effective when used in combination, which can extend the life of the iron-based metal and increase the amount of processing solution per weight of the iron-based metal. At this time, decreasing the pH also has the effect of regenerating the iron-based metal.Therefore, the selenium is removed while temporarily reducing the pH and regenerating the iron-based metal. The method of returning can also be adopted.

In the method of the present invention, iron ions are eluted in the liquid after the treatment. When elution of iron ions becomes a problem, a method of removing as a precipitate by adding an alkali, a method of removing with a chelating resin, a method of removing with an ion exchange membrane, a method of removing with manganese sand, and the like can be used. Also, by making the pH of the selenium-containing solution relatively high, elution of iron ions can be suppressed.

In addition, a method of separating selenium that separates by sonicating the metal on which selenium is deposited, a method of separating selenium that separates by passing hot water through the metal on which selenium is deposited, etc. Is mentioned. Since selenium does not have a strong adsorptive power on the metal surface, a method of separating selenium by some physical action is also used without limitation.

The treatment method of the present invention may be used in combination with conventional methods such as neutralization precipitation method for recovering selenium, iron hydroxide precipitation method, ferrite precipitation method, ion exchange membrane treatment method, and activated carbon adsorption method, if necessary. Can be implemented. Example

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist is not exceeded.

Example 1

Steel wool (00.04mm: Product name Bonstar: Nippon Steel Wool Co., Ltd.)

1.65 g packed into a glass column with a jacket (inner diameter 11 mm, height 120 mm, column volume 12 ml) (iron surface area: 0.0127 m ² / g-iron, iron column Per volume: 0.00175m ² Zm 1, iron column loading: 0.133 gZm 1), containing 300 ppm of sodium sulfate (converted to sulfuric acid) adjusted to pH 4 and 5 ppm of sodium selenate (converted to selenium) The solution was passed through the column in an upward flow at a flow rate of SV = 5. The temperature of the jacket was maintained at 50 ° C during the passage. After passing through 10 BV (Bed Volume), the concentration of selenium in the solution was 3.2 ppm.

The selenium concentration was measured by ICP (Inductively coupled plasma) emission spectroscopy (hereinafter, referred to as "ICP emission method").

Example 2

Example 1 was repeated except that the temperature of the jacket was maintained at 80 ° C. As a result, the concentration of selenium in the solution after passing 10 B.V. was 0.7 ppm.

Comparative Example 1

Example 1 was repeated except that the temperature of the jacket was maintained at 20 ° C. As a result, the concentration of selenium in the solution after passing 10 B.V. was 5. Oppm, and selenium in the solution was hardly removed.

Example 3

1.0 g of steel wool (00.025 mm: trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) into a glass column with a jacket (inner diameter 11 mm, height 100 mm, force ram volume 10 ml) Sodium sulphate packed (surface area of iron: 0.021 m ² / g-iron, iron column volume: 0.0021 m ² nom 1, iron column loading: 0.10 gZm 1), and adjusted to pH 4 A solution containing 0 ppm (in terms of sulfuric acid) and 5 ppm of sodium selenate (in terms of selenium) was passed through the column in an upward flow at a flow rate of SV = 2. Permeate During this time, the temperature of the jacket was maintained at 50 ° C. The concentration of selenium in the solution after passing the solution through 20 BV was 0.01 Ppm or less. The measurement of the selenium concentration was performed by the ICP emission method.

Example 4

Example 3 was repeated in the same manner as in Example 3 except that the diameter of the steel wool was changed to 00.04 mni (iron surface area: 0.013 m ² / g-iron, per iron column volume: 0.0013 m ² / m 1, iron Column carrying amount: 0.1 lOgZm 1). The concentration of selenium in the solution after passing 20 BV was 0.1 lOppm.

Example 5

Example 3 was carried out in the same manner as in Example 3, except that iron wool having a fiber diameter of 0.5 (0.5 mm metal wire _: manufactured by Mitsuwa Chemicals Co., Ltd.) was used instead of steel wool (surface area of iron: 0.001 m ^2). / g-iron, per iron column volume: 0.0001 m ² Zm 1, iron force Ram loading: 0.1 lOgZm 1). The concentration of selenium in the solution after passing through 2 O BV was 0.47 ppm.

Example 6

1.50 g of steel wool (trade name: Bonstar, manufactured by Nippon Steel Wool Co., Ltd.) packed in a glass column (inside diameter llmm, height 120 mm, column volume 12 ml) with a jacket (iron surface area: 0.0127 m ² / g-iron, per iron column volume: 0.00158 m ² / ml, iron column loading: 0.125 g / ml) 5000 ppm of sodium sulfate (sulfate conversion) adjusted to pH 4 and 0.5 ppm of sodium selenate (selenium conversion) The containing solution was passed through the column in an upward flow at a flow rate of SV = 5. During the passage, the temperature of the jacket was maintained at 80 ° C. In this test, liquid was passed up to 800 BV. Further, the pH of the treatment liquid was lowered to 3, and 100 B.V. was passed. Thereafter, the pH of the treatment liquid was set to 4, and 100 B.V. was further passed. Sampling was performed every 100 BV, and the selenium and iron concentrations of the solution were determined by the ICP emission method. Table 1 shows the results.

After passing the solution to 800 B.V., the leak of selenium was reduced by lowering the pH to 3, and then the leak of selenium remained lowered even when the pH was returned to 4. table 1

S e Fe

B. V. p HC ini t.) P P m P P m

Undiluted solution 0.15 ―

100 4 0.03 2.84

200 4 0.03 2.23

300 4 0.03 2.87

400 4 0.07 2.22

500 4 0.11 2.72

600 4 0.08 2.40

700 4 0.09 2.39

800 4 0.13 2.39

900 3 0.01 35. 0

1000 4 0.03 2.98 Example 7

Steel wool (0.04 thigh, trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) 1. Pack 50 g into a glass column with a jacket (inner diameter l lmm, height 120ππη, column volume 12 ml) (iron surface area) : 0.0127m ² Zg-iron, per iron column volume: 0.00158m ² / ml, iron column loading: 0.125g / ml), 5000ppm sodium sulfate adjusted to pH3 (sulfuric acid conversion) and selenic acid A solution containing 0.5 ppm of sodium (in terms of selenium) was passed through the column in an upward flow at a flow rate of SV = 5. During the passage, the temperature of the jacket was maintained at 80 ° C. In this test, the liquid was passed up to 500 BV. Sampling was performed every 100 BV, and the selenium and iron concentrations of the solution were quantified by ICP emission method. The results are not shown in Table 2. Table 2

S e Fe

B. V. p H (init.P P m P P m

Undiluted solution 0.50

100 4 <0.01 01 27.3

200 4 0.01 28. 4

300 4 0.01 29.8

400 4 0.01 29.5

500 4 0.01 34.0 Example 8

Steel wool (0.04 mm, trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) 1. Place 50 g into a glass column with a jacket (inner diameter lirau height 120 mm, column volume 12 ml) (iron surface area: 0 0127m ² Zg-iron, per iron column volume: 0.00158m ² / ml, iron column loading: 0.125g / ml), pH 4 adjusted sodium sulfate lOOppm (sulfuric acid conversion) and sodium selenate 5ppm A solution containing (in terms of selenium) was passed through the column at an upward flow rate at a flow rate of SV = 5. During the passage, the temperature of the jacket was maintained at 50 ° C. In this test, liquid was passed up to 2000 BV. The selenium concentration in the solution after passing through 2000 B.V. was 0.37 ppm. The selenium concentration was determined by the ICP emission method.

After the test, a part of the steel wool having a weight of about 1/6 was extracted, placed in a 100 ml Erlenmeyer flask, further added with 50 ml of 0.01N HC1, and shaken at 50 spm for 30 minutes. At this time, red solid components were released from the steel wool. The iron component was magnetically separated from this solution, and the remaining precipitated component was filtered through a 0.45 μm nitrocellulose membrane filter. The selenium concentration in this filtrate was 0.1 ppm or less, and the iron concentration was 256 ppm. The filtered components were placed in a 100 ml eggplant type flask equipped with a Dimroth condenser, 5 ml of concentrated nitric acid was added, and the mixture was reacted at 90 ° C. for 30 minutes with stirring to dissolve all solid components. Cooling water at 5 ° C was passed through the Jimroth condenser. After cooling, the reaction solution was diluted to 50 ml and the selenium and iron concentrations were measured. The selenium concentration was 14.9 ppm and the iron concentration was 11.2 ppm. Example 9

About one sixth of the weight of the steel wool after the passage of the selenium solution carried out in Example 8 was removed, placed in a 100 ml Erlenmeyer flask, further added with 50 ml of INHC1, and shaken at 50 spm for 30 minutes. At this time, a reddish brown solid component was released from the steel wool. The iron component was magnetically separated from this liquid, and the remaining precipitated component was filtered through a 0.45 zm nitrocellulose membrane filter. The selenium concentration in the filtrate was 0.1 ppm or less, and the iron concentration was 1580ΡΡΠ1. The filtered components were placed in a 100 ml eggplant-shaped flask equipped with a Dimroth condenser, 5 ml of concentrated nitric acid was added, and the mixture was reacted at 90 ° C. for 30 minutes with stirring to dissolve all solid components. Cooling water at 5 ° C was supplied to the Jimroth condenser. After cooling, the reaction solution was diluted to 50 ml and the selenium and iron concentrations were measured. The selenium concentration was 42.7 ppm and the iron concentration was 3.6 ppm.

Example 10

About one sixth of the weight of the steel wool after passing the selenium solution carried out in Example 8 was removed, put into a 100 ml Erlenmeyer flask, and further added with 50 ml of demineralized water. The treatment was performed at a frequency of 46 KHZ) for 30 minutes. At this time, a brown solid component was released from the steel wool. The iron component was magnetically separated from this solution, and the remaining precipitated component was filtered through a 0.45 μm nitrocellulose membrane filter. The selenium concentration in the filtrate was less than 0.1 ppm and the iron concentration was less than 0.1 ppm. The filtered components were placed in a 100-ml eggplant type flask with a Dimroth condenser, 5 ml of concentrated nitric acid was added, and the mixture was reacted at 90 ° C for 30 minutes with stirring to dissolve all solid components. Cooling water at 5 ° C was passed through the Jimroth condenser. After cooling, the reaction solution was diluted to 50 ml and the selenium and iron concentrations were measured. The selenium concentration was 20.6 ppm and the iron concentration was 76.8 ppm.

Comparative Example 2

About 1/6 of the weight of the steel wool after the passage of the selenium solution carried out in Example 8 was removed, put into a 100 ml Erlenmeyer flask, and further added with 50 ml of 0.001N HC1, and added with 50 spm for 30 minutes. Shake. At this time, no solid components were released from the steel wool. The iron component was magnetically separated from this solution, and the remaining precipitated component was filtered through a 0.45 / 1-nitrocellulose membrane filter. In this filtrate The selenium concentration was less than 0.1 ppm and the iron concentration was 37.6 ppm.

Example 1 1

1.0 g of steel wool (00.04 mm: product name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) into a glass column with a jacket (inner diameter 11 mm, height 100 mm, force ram volume 10 ml) Filled (surface area of iron: 0.0068m ² Zg-iron, per column volume of iron: 0.00063m ² Zm, column loading of iron: 0.05 g / m 1), and adjusted to pH 4 with sodium selenate 0.50ppm A 50 mM phosphate buffer (selenium-containing solution) containing (in terms of selenium) was passed through the column in an upward flow at a flow rate of 50 ml / hour. The jacket temperature was maintained at 50 ° C during the flow. The concentration of selenium in the solution after passing 20 BV was 0.25 ppm. The pH at this time was 6.5. Example 1 2

As the primary treatment, the same method as in Example 11 was performed. The outlet liquid (selenium concentration: 0.25 ppm) was adjusted to pH 4 with hydrochloric acid, and used as a secondary treatment liquid to be added to the column. The liquid was passed through the same column again in the same manner as in Example 11. The selenium concentration in the solution after passing through 20 B.V. was 0.08 ppm. The pH at this time was 6.3.

Example 13

Example 11 The columns used in 1 were connected in series in two stages, and 50 mM phosphate buffer (solution containing selenium) containing 0.50 ppm (converted to selenium) of sodium selenate adjusted to pH 4 was added to the column. The liquid was passed upward at a flow rate of 50 m 1 / hour. The temperature of the jacket was maintained at 50 ° C during the passage. The concentration and pH of selenium in the solution after passing through 20 BV were 0.25 ppm, pH 6.5 at the outlet of the first column, and 0.21 ppm, pH 7.25 at the outlet of the second column. It was eight.

Comparative Example 3

Example 11 The columns used in Example 1 were connected in series in three stages, and 50 mM phosphate buffer (solution containing selenium) containing 0.50 ppm (converted to selenium) of sodium selenate adjusted to pH 4 was added to the column. The liquid was passed upward at a flow rate of 50 m 1 Zhour. The temperature of the jacket was maintained at 50 ° C during the passage. The concentration of selenium in the solution after passing through 20 BV and the selenium concentration at the outlet of the first-stage column were 0.25 ppm, pH 6.5, and the second-stage column. The selenium concentration at the outlet was 0.21 ppm, pH 7.7, and the selenium concentration at the third outlet was 0.21 ppm, pH 8.1.

Example 14

In Example 13, at the inlet of the second-stage column, 0.5N Zhour of 0.1N HC1 was continuously added in addition to the treatment solution. 20 The selenium concentration and pH of the solution after passing through the solution were 0.25 ppm, pH 6.3 at the outlet of the first column and 0.09 ppm, pH 6.6 at the outlet of the second column. Was.

Example 15

50 g of steel wool (00.04 mm, trade name: Bonstar: manufactured by Japan Steel Wool Co., Ltd.) was added to a 100-m1 square flask, and 50 g of distilled water was added. Stirred at 50 rpm in C water bath. Sodium selenate 50 ppm (converted to selenium) Sodium sulfate l OOOppm (converted to sulfuric acid) A mixed solution was added at 50 ml / hour, and the reaction solution was removed outside the system at 50 ml / hour. . Here, the pH in the reactor was kept in the range of 4 to 6 by adding 0.1N HCl as appropriate. One liter of solution was processed and its selenium concentration was 0.06 ppm.

Comparative Example 4

In Example 15, the same method as in Example 15 was carried out except that the pH in the reactor was maintained at pH 9 to 10 by appropriately adding 0.1 IN HC1 and 0.1 IN NaOH. . One liter of solution was processed and its selenium concentration was 0.50 ppm.

Example 16

200 ml of a solution containing sodium selenate lOppm (converted to selenium) and 500 ppm (converted to boron) of sodium tetraborate were adjusted to boric acid-selective resin Diaion CRB02

The solution was passed through a column packed with 100 ml (manufactured by Mitsubishi Chemical Corporation) (internal diameter 26) at SV = 2. The boron concentration in the solution after the passage was less than 1 ppm. This solution is adjusted to pH 3 with hydrochloric acid, placed in a 300 ml square flask, and 0.20 g of steel wool (00.04 substitute: trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) is added. The solution is heated to 50 ° C in a water bath. The mixture was heated and reacted under stirring. The selenium concentration at a reaction time of 4 hours was 3.0 ppm, and the selenium concentration at a reaction time of 6 hours was 0.3ΡΡΠ). Selenium concentration was measured by the ICP emission method. Example 17

200 ml of a solution containing sodium selenate lOppm (converted into selenium) and 500 ppm (converted into boron) sodium tetraborate is adjusted to pH 3 with hydrochloric acid, placed in a 300-ml square flask, and further filled with steel wool (0.04 mm: product). 0.20 g) was added, and the mixture was heated to 50 ° C. in a water bath and reacted under stirring. The selenium concentration at a reaction time of 4 hours was 7.8 ppm. Selenium concentration is measured by ICP emission method.

XE 7

Example 18

500 ml (adjusted to pH7) of a solution containing 0.5 ppm of sodium selenate (converted to selenium), 5000 ppm of sodium sulfate (converted to ionic sulfate), and 250 ppm (converted to boron) of boric acid was added to the boric acid-selective resin Diaion CRB02 ( The liquid was passed through a column (45 mm inside diameter) filled with 500 ml at SV = 1 (manufactured by Mitsubishi Chemical Corporation). The boron concentration in the solution after passing was less than 10 ppm. The pH of this solution was adjusted to 4 with hydrochloric acid, and steel wool (0.04 mm: trade name Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) l. Og-filled jacketed column (inner diameter 11 difficult, high The solution was passed through an upward flow at a flow rate of SV = 2 through a column with a length of 100 mm and a column volume of 10 ml). During the passage, the temperature of the jacket was 50 ° C. The selenium concentration at the time of passing 500 ml of liquid was 0.1 ppm.

Example 19

Adjust the pH to 4 with hydrochloric acid in 500 ml of a solution containing 0.5 ppm of sodium selenate (converted into selenium), 5000 ppm of sodium sulfate (converted into ion sulfate), and 250 ppm of boric acid (converted to boron). 04 mm: Trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd. l The liquid was passed upward through a column with a jacket filled with Og (inner diameter l lnrau, height 100 mm, column volume 10 ml) at SV = 2. During the passage, the temperature of the jacket was 50 ° C. The selenium concentration at the time of passing through 500 ml was 0.13 ppm.

Industrial applicability

According to the method of the present invention, wastewater containing other inorganic acid salts such as a compound having a buffering action near neutrality, such as an alkali metal sulfate and a boron compound, together with selenium in a solution is efficiently treated by a simple treatment operation. Processing to reduce selenium concentration.

Claims

The scope of the claims

1. A solution containing selenium and another metal inorganic acid salt is allowed to flow through a packed bed of iron-based metal to deposit selenium on the surface of the iron-based metal. 3. The method for treating a selenium-containing solution according to claim 1, wherein

2. The method for treating a selenium-containing solution according to claim 1, wherein the pH value of the solution containing selenium and another metal inorganic acid salt is adjusted to 3 to 7.

3. The method for treating a selenium-containing solution according to claim 1, wherein the other metal inorganic acid salt is a sulfate of an alkali metal and an alkaline earth metal.

4. The method for treating a selenium-containing solution according to claim 1, wherein the solution containing selenium and another metal inorganic acid salt is allowed to flow in an upward direction through a packed bed of an iron-based metal.

5. When contacting a solution containing selenium and other metal inorganic acid salts with a bed of iron-based metal, contact the solution while maintaining the PH value of the solution in the bed between 3 and 7. The method for treating a selenium-containing solution according to claim 1, which is characterized in that:

6. A plurality of steps consisting of adjusting the pH value of the solution containing selenium and other metal inorganic acid salts to 3 to 7 and bringing the solution after the pH adjustment into contact with the iron-based metal packed layer. 2. The method for treating a selenium-containing solution according to claim 1, wherein the method is repeated twice.

7. When a solution containing selenium and other metal inorganic acid salts is allowed to flow through the iron-based metal packed bed, an acid is added to the packed bed to adjust the pH value of the solution in the bed to 3 to 7. 2. The method for treating a selenium-containing solution according to claim 1, wherein the selenium-containing solution is retained.

8. Add a solution containing selenium and other metal inorganic acid salts and dilute acid to a reaction vessel containing an iron-based metal, and stir at 30 ° C while maintaining the pH value at 3 to 7. A method for treating a selenium-containing solution, wherein the reaction is carried out at the above temperature.

9. The method for treating a selenium-containing solution according to claim 1, wherein the iron-based metal is in a fibrous form, a porous body, a fine plate-like form, a granular form, or a powdery form.

10. The method for treating a selenium-containing solution according to claim 9, wherein the iron-based metal is fibrous.

1 1. The method for treating a selenium-containing solution according to claim 9, wherein the ferrous metal is formed into a fibrous form by a cutting method.

12. The method for treating a selenium-containing solution according to claim 9, wherein the ferrous metal is fibrous having a diameter of 0.01 to 3 mm.

1 3. The method for treating a selenium-containing solution according to claim 1, wherein the iron-based metal is steel wool.

14. The method for treating a selenium-containing solution according to claim 9, wherein the iron-based metal is porous.

1 5. The method for treating a selenium-containing solution according to claim 1, wherein the iron-based metal is iron having a surface area of 0.001 m ² / g or more.

1 6. The method for treating a selenium-containing solution according to claim 1, wherein the iron-based metal is iron having a surface area of iron of 0.001 m ² Zml or more per column volume.

17. The method for treating a selenium-containing solution according to claim 1, wherein the amount of the iron-based metal loaded on the column is from 0.01 g / m1 to 3 gZm1.

1 8. The selenium-containing solution according to claim 1, wherein the solution containing selenium and other metal inorganic acid salt is a solution containing 100% or more of selenium sulfate of selenium concentration. Processing method.

19. The solution according to claim 1, wherein the solution containing selenium and another metal inorganic acid salt contains a weakly acidic strong base salt, a strongly acidic weakly basic salt, a weakly acidic weakly basic salt and Z or a metal complex salt. A method for treating a selenium-containing solution as described in the above.

20. Weak acid strong base, strong acid weak base, weak acid weak base and Z or metal complex, ammonium salt, carbonate, phosphate, borate, carboxylate, aluminum complex, copper complex, cobalt The method for treating a selenium-containing solution according to claim 19, which is a complex salt and a Z or iron complex salt.

2 1. a step of passing a solution containing selenium and another metal inorganic acid salt at a temperature of 30 ° C. or more through a packed bed of iron-based metal to precipitate selenium on the surface of the iron-based metal; and A method for treating a selenium-containing solution, comprising the step of incinerating or separating selenium deposited on the surface of the iron-based metal and recovering it.

22. The method for treating a selenium-containing solution according to claim 21, wherein the separation treatment is contact with a dilute acid or ultrasonic treatment.

23. The method for treating a selenium-containing solution according to claim 21, wherein the ferrous metal is regenerated by contact with a dilute acid or ultrasonic treatment.

24. a step of flowing a solution containing selenium and another metal inorganic acid salt through a packed bed of iron-based metal at a temperature of 30 ° C. or higher to precipitate selenium on the surface of the iron-based metal; A step of incinerating or separating selenium precipitated on the surface of the iron-based metal and recovering the same, and raising the solution temperature in accordance with a decrease in the selenium recovery capacity in the step, lowering the pH value of the solution, and A method for treating a selenium-containing solution, which comprises a step of reducing the flow rate of the solution.

25. In treating a solution containing a selenium compound and containing a compound having a buffer action near neutral, a step of removing the compound having a buffer action near neutral from the solution And removing the selenium compound by contacting the solution with a treating agent capable of reducing and removing the selenium compound on the neutral to acidic side.

26. After the step of removing the compound exhibiting a buffering action near neutrality, the selenium compound is brought into contact with a treating agent composed of an iron-based metal having the ability to reduce and remove the selenium compound from neutral to acidic side. The method for treating a selenium-containing solution according to claim 25, wherein a step of removing is performed.

27. The method for treating a selenium-containing solution according to claim 25, wherein the treating agent capable of reducing and removing a selenium compound from a neutral to an acidic side is an iron-based metal.

28. The method for treating a selenium-containing solution according to claim 25, wherein the compound having a buffer action near neutrality is a boron compound and / or an aluminum compound.

29. The method for treating a selenium-containing solution according to claim 25, wherein the compound having a buffering action near neutrality is a boron compound.

30. The method for treating a selenium-containing solution according to claim 29, wherein the compound exhibiting a buffering action near neutrality is removed using a boric acid-selective resin.

31. The method for treating a selenium-containing solution according to claim 30, wherein the boric acid-selective resin is a glucamine-type chelate resin.

32. The method for treating a selenium-containing solution according to claim 25, wherein the compound having a buffering action near neutrality is an aluminum compound, and the aluminum compound is removed by coagulation precipitation. .