JPH11207364A - Treatment of selenium-containing solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of efficiently lowering the selenium concentration in waste water in a short time by efficiently treating a discharge water incorporating selenium and inorganic acid salt of a compound such as alkali sulfate and boric compound, showing a buffer action in the neutral vicinity by a simple treating operation. SOLUTION: When the solution incorporating selenium and another metallic inorganic acid salt is passed through a packed layer of iron series metal and selenium is deposited on the surface of the iron series metal, the solution is brought into contact with the iron series metal at >30 deg. and preferably in a range of pH3-7, and in some case, a compound showing a buffer action in the neural vicinity of the discharge water is removed before the contact with the iron series metal, thus the treatment method of the selenium-containing solution can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating a solution containing selenium to efficiently reduce the selenium concentration in the solution or to recover selenium.

[0002]

2. Description of the Related Art Selenium and selenium compounds are used in various manufacturing industries such as a decolorizing agent for glass, a photoreceptor for a copying machine, a rectifier, a semiconductor material, a battery material, and an electrolytic coloring agent for metals such as aluminum. The wastewater discharged from these production processes usually contains a relatively high concentration of selenium. Selenium is also present in wastewater from selenium refining plants and selenium compound manufacturing plants. further,
It has been found that wastewater discharged from thermal power plants also contains selenium. Since selenium is a very toxic environmental pollutant, its amount in the effluent is strictly regulated. In recent years, the allowable amount has been set more strictly, and the effluent standard is set at 0.1 to 0.01 mg / l. .

[0003] As a method for recovering selenium, generally, a neutralization coagulation precipitation method, an iron hydroxide precipitation method, a ferrite 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 using a plurality of treatment methods in order to efficiently remove selenium, which increases equipment costs and operation costs, and is economically disadvantageous. is there.

[0004] A method of adding iron or an iron-based metal to wastewater and depositing selenium on the surface of the iron or iron-based metal (US Pat. No. 4,40,40)
No. 5,464, and Japanese Patent Application Laid-Open No. 7-2502) are known. However, this method of using iron metal is an effective means for removing selenium compounds, but it takes not only a long time but also a large amount of time to reduce a large amount of wastewater to a very low standard concentration. Handling heavy iron metal was also difficult. In particular, in a system in which a large amount of coexisting salts other than selenium is present, problems such as a decrease in the reaction rate have occurred.
As a countermeasure, it is conceivable to remove all coexisting salt components. However, when a large amount of coexisting salt is present, it is not practical to reduce the total amount of coexisting salt.

Among the selenium compound-containing waste liquids, a system containing a large amount of coexisting salts includes flue gas desulfurization effluent from a coal-fired power plant. It is known that various coexisting ions are present in the effluent of coal-fired power plants, as shown on page 1083 of Nuclear Power Plant, Vol. 35, No. 10, 1984. It is not yet known which component of the coexisting ions makes a large contribution. When a large amount of coexisting salts is present, such as flue gas desulfurization effluent from a coal-fired power plant, a method for removing selenium compounds more efficiently is required. On the other hand, a method of recovering selenium by adding a reducing iron compound to a selenium-containing solution, then adjusting the pH and adding a metal trapping agent (Japanese Patent Application Laid-Open No. 9-59007)
However, in this method, pH adjustment is required each time according to the treatment process, so that the operation is complicated and is not suitable as a method for treating a large amount of wastewater.

[0006]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies to solve the above problems and to provide a method for efficiently removing and recovering selenium in wastewater. By controlling the conditions under which selenium is deposited on the surface of the selenium, in some cases, compounds other than selenium in the wastewater may be removed by removing a compound exhibiting a buffering action near neutrality and then removing the selenium compound. The present inventors have found that the selenium concentration can be effectively reduced with time, and have arrived at the present invention based on this finding.

[0007]

The gist of the present invention is that a solution containing selenium and another metal inorganic acid salt is passed through a packed bed of iron-based metal to deposit selenium on the surface of the iron-based metal. In doing so, the present invention resides in a method for treating a selenium-containing solution, which comprises contacting the solution with an iron-based metal at a temperature of 30 ° C. or higher.

[0008] In a preferred aspect of the present invention, in the above treatment method, the pH value of the solution containing selenium and the other metal inorganic acid salt is adjusted to 3 to 7;
Being a sulfate of an alkali metal and an alkaline earth metal; flowing a solution containing selenium and other metal inorganic acid salts upward through a packed bed of iron-based metal; selenium and other metal inorganic acids When the solution containing the salt is brought into contact with the packed layer of the iron-based metal, the solution is kept while maintaining the pH value of the solution in the packed layer at 3 to 7; a solution containing selenium and other metal inorganic acid salts A plurality of steps of adjusting the pH of the solution to 3 to 7 and contacting the solution after the pH adjustment with a packed bed of iron-based metal; a solution containing selenium and other metal inorganic acid salts Is passed through a packed bed of an iron-based metal, a method comprising adding an acid to the packed bed to maintain the pH value of a solution in the bed at 3 to 7,
In another embodiment, a reaction vessel containing an iron-based metal is
A method for treating a selenium-containing solution, comprising adding a solution containing selenium and another metal inorganic acid salt and a dilute acid, and performing a contact reaction at a temperature of 30 ° C. or more with stirring while maintaining the pH value at 3 to 7. It is.

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; That the ferrous metal is fibrous by a cutting method; that the ferrous metal is fibrous having a diameter of 0.01 to 0.3 mm; that the ferrous metal is steel wool; The metal is porous; the iron-based metal is iron having a surface area of at least 0.001 m ² / g; the iron-based metal has an iron surface area of 0.0001 m ² per column volume.
Iron / metal; the amount of iron-based metal supported on the column is from 0.01 g / ml to 3 g / ml.

[0010] A preferred treatment solution for the method of the present invention is that the solution containing selenium and other metal inorganic acid salts is a solution containing sulfate ions at 100 times or more the selenium concentration; The solution containing another metal inorganic acid salt 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 And / or the metal complex salt
Examples include ammonium salts, carbonates, phosphates, borates, carboxylates, aluminum complexes, copper complexes, cobalt complexes and / or iron complexes.

The present invention comprises 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; Includes a method for treating a selenium-containing solution, which comprises a step of incinerating or removing selenium deposited on the surface of the iron-based metal and subjecting the selenium-containing solution to peeling treatment, wherein the peeling treatment is contact with a dilute acid or ultrasonic treatment. A method of regenerating an iron-based metal by contact with a dilute acid or ultrasonic treatment, and further, a solution containing selenium and another metal inorganic acid salt is heated at a temperature of 30 ° C. or more to obtain an iron-based metal. A step of flowing selenium on the surface of the iron-based metal by flowing a metal packed layer, a step of incinerating or separating selenium deposited on the surface of the iron-based metal and recovering the selenium, and a step of recovering selenium in the step. Respond to decline Raising the solution temperature Te, the solution p
The method of the present invention also includes a treatment method comprising a step of decreasing the H value and / or decreasing the flow rate of the solution.

In another preferred embodiment of the present invention, when a solution containing a selenium compound and containing a compound having a buffering action near neutrality is treated, the solution is buffered near neutrality from the solution. A method of removing a compound exhibiting an action, and a step of 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, The processing method is
After the step of removing compounds showing a buffering action near neutral,
Performing a step of removing the selenium compound by contacting with a treating agent comprising an iron-based metal capable of reducing and removing the selenium compound from the neutral side to the acidic side; reducing and removing the selenium compound from the neutral side to the acidic side The treating agent having the ability is an iron-based metal; the compound having a buffering action near neutral is a boron compound and / or an aluminum compound; the compound having a buffering action near neutral is a boron compound That removal of a compound exhibiting a buffering action near neutrality is performed using a boric acid-selective resin;
A glucamine-type chelate resin; a compound having a buffering action near neutrality is an aluminum compound, and includes a method comprising removing the aluminum compound by coagulation and precipitation.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The selenium-containing solution to be treated in the present invention is mainly a decolorizing agent for glass, a photoconductor of a copying machine, a rectifier, a semiconductor material,
Wastewater from various manufacturing plants such as battery materials and aluminum,
It targets wastewater from selenium refining and selenium compound manufacturing plants, or wastewater from thermal power plants.Selenium contained therein is present as various selenium compounds depending on the source of the wastewater. For example, selenium compounds such as selenic acid, selenium dioxide, selenium trioxide, selenous acid, selenium tetrachloride, sodium selenide, potassium selenide, ferrocene, copper selenide, nickel selenide, sodium selenite, potassium selenite And selenites such as barium selenite and the like, and selenates such as sodium selenate, potassium selenate and barium selenite.
The selenium concentration in the solution also differs depending on the type of wastewater,
For example, during drainage from thermal power plants, typically 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 and magnesium chloride, and alkaline earth metals. Heavy metals such as sulfates, chlorides, copper, chromium, nickel and the like are contained together with selenium, and it is effective to apply a solution containing these salts to the treatment method of the present invention. Especially,
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 at 100 times or more the selenium concentration, and other metal inorganic acid salts other than selenium are alkali metal. And a sulfate of an alkaline earth metal.

When the pH value described below is controlled within a certain range, a solution containing a metal inorganic acid salt other than selenium may be used, especially if the solution contains a weak acid strong base salt, a strong acid weak base salt, or a weak acid weak salt. A solution containing a base salt and / or a metal complex salt,
In other words, preferably it has an acid dissociation constant is a solution containing a substance that is in the range of 10-2 ^{2-10 -10.} As the weak acid strong base salt, strong acid weak base salt, weak acid weak base salt and / or metal complex salt, ammonium salt, carbonate, phosphate,
Borate, carboxylate, aluminum complex, copper complex,
Preferably, it is either a cobalt complex salt and / or an iron complex salt.

The present invention is also effective when the solution containing selenium and other metal inorganic acid salts contains a compound exhibiting a buffering action near neutrality in the solution. Examples of the compound having a buffering action near neutrality include a weakly acidic strong base salt, a strongly acidic weakly basic salt, a weakly acidic weakly basic salt, a complex compound or a metal ion compound which forms a hydroxide. Specifically, the acid dissociation constant of 10-2 ^2-10
A compound of the range of over ^12, ammonium salts, carbonates,
Examples thereof include phosphate, borate, carboxylate, aluminum complex, copper complex, cobalt complex, iron complex, and metal hydroxides such as aluminum hydroxide. In a selenium-containing solution in which such a substance is present, the ability to remove selenium due to contact with an iron-based metal is reduced, but in the present invention, a step of removing these buffer components is performed by removing In this case, the selenium removing ability can be prevented from being reduced by performing the steps sequentially or simultaneously.

The amount of the buffer component contained in the selenium-containing solution is as follows:
It is preferable that the amount is as small as possible, but it is not particularly limited and is preferably 100 ppm or less, more preferably 10 ppm or less.
It suffices if it is less than ppm. As described above, the cause of the reduction in the efficiency of selenium removal in the following steps due to the presence of the buffer component is not clear, but upon contact with an iron-based metal,
The presence of the buffer component increases the pH of the solution,
This is considered to be because the pH exceeds the neutral to acidic pH range in 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 to the range of 2 to 10, preferably 3 to 7, and particularly preferably 3 to 4. Since the removal rate of selenium by iron increases as the pH decreases,
From the viewpoint of the reaction rate, the lower the pH, the better. However, when the pH is lowered, the reaction between iron and protons increases the elution of iron ions and also increases the amount of acid added for pH adjustment. For this reason, a pH lower than 2 is not practical. On the other hand, if 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 using an acid or an alkali. As the acid, an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid is used. As the alkali, an alkali metal water such as sodium hydroxide or potassium hydroxide is used. Oxides.

In the present invention, an iron-based metal is used to precipitate selenium. Here, the iron-based metal includes pure metal iron and alloyed iron containing other metals such as chromium and manganese. It is. Specific examples of iron-based metals include electrolytic iron, low-carbon steel, medium-carbon steel, high-carbon steel, ultra-mild steel, mild steel,
Alloy steel, pig iron, cast iron, rimmed steel, capped steel, semi-killed steel, killed steel, clad steel, crude steel, steel ingot, and the like. 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 products. Any of processed products, forged products, cast steel products, etc. may be used.

Although the shape of the iron-based metal used in the present invention is not particularly limited, in the treatment method of the present invention, selenium in the solution is deposited on the surface of the iron-based metal by a catalytic reduction reaction with the selenium-containing solution to be treated. A shape having as large a contact surface area as possible is desirable because it is deposited, and a shape that can easily form a homogeneous packed layer when packed in a treatment tower is preferred. Specific examples include thin fibrous wire rods such as steel wool, plate-like strips, powders, granules, fine chips, and the like, with steel wool being preferred. A plate-like material has a drawback that it is difficult to pack it into a column and that the surface area is small. In addition, when the particle size is small, the problem of compaction occurs in the column when the particle size is small, and the surface area cannot be increased when the particle size is large. Further, there is a problem that the weight of the whole apparatus is increased because iron is packed most densely in a granular or powdery material. Here, the fibrous material is optimally used because the surface area and the packing density can be easily adjusted. As the fibrous iron, iron having a small fiber diameter is suitable.
A preferred fiber diameter is 0.01 to 0.3 mm.

As a method for processing the fibrous iron-based metal, for example, a method such as a drawing method, a melt spinning method, and a cutting method is used (Takeo Nakagawa et al., Journal of the Textile Society, Vol. 39, No. 4, 121-12).
7 (1983)), among which those produced by the cutting method are preferred. This seems to be due to the fact that a fiber having a smaller fiber diameter can be produced by using the cutting method, and the surface morphology of the fibrous metal obtained by the cutting method is suitable for selenium adsorption. Here, the cutting method is a method of shaving a metal block with a blade and obtaining a desired shape while discharging fine chips, and a fiber metal obtained by using the chips as a fiber is obtained by the cutting method. . A wire cutting method is a method for constantly shaving fibers having a finer cross section, and a typical example thereof is production of steel wool by a wire cutting method. This steel wool is most suitable for the selenium removal of the present invention. Further, regardless of the shape of iron, a porous material is advantageous in increasing the surface area and can control the packing density, so that it is preferably used. Regarding the porous iron body,
It can be manufactured by a sintering method, a plating method, a foaming method, a pressure casting method, or the like, and can be used without any particular limitation on the pore diameter, the pore shape, and the like.

The surface area of the iron-based metal is preferably 0.001 m ² / g or more 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. In addition, for the same reason, the surface area of the iron-based metal per column volume is also limited, and the surface area of iron-based metal per column volume is limited to 0.
It is preferably at least 0001 m ² / ml. Also, 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 an ordinary ion exchange resin is around 1.
For this reason, special equipment that is different from equipment that normally carries an ion exchange resin or the like is required. Therefore, it is practical to reduce the amount of packing in the column. If the supported amount is too low, the selenium removability is reduced. Therefore, the amount is preferably 0.01 g / ml or more and 3 g / ml or less, more preferably 0.05 g / ml or more and 1 g / ml or less in terms of column volume.

In the method of the present invention, fibrous, porous, granular,
The treatment tower containing a powdery or other suitable iron-based metal in a processing tower is brought into contact with a packed bed formed by passing a solution to be treated containing selenium and other metal salts, so that selenium and the like Is deposited on the surface of the metal of
C. or more, preferably 45-90 ° C.
It is performed in a temperature range of ° C. If the contact temperature is lower than 30 ° C., the reduction reaction of selenium with iron hardly progresses, and it is difficult to recover and remove selenium from the solution. Further, it is not preferable to raise the temperature to an unnecessarily high temperature in terms of operability and economy, and in some cases, it is not desirable because it may be affected by other components coexisting in the waste liquid.
Even if the contact temperature is controlled by maintaining the temperature in the packed tower within a predetermined range by external heating, the contact temperature is maintained by heating the solution to be treated to a predetermined temperature and supplying the solution to the packed tower. Is also good.

The flow of the solution to be treated into the packed tower is performed in a downward flow,
Either upward flow may be used, but in order to sufficiently contact the iron metal, it is preferable to pass the liquid upward from the lower part of the packed tower. 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 the temperature, and the like, but it is usually operated in the range of SV (space velocity; h ^-1 ) = 2 to 10. Is done.

In the method of the present invention, factors that determine the reaction rate of selenium removal include temperature, pH and SV. The individual conditions have already been described, but to increase the reaction rate, the higher the temperature, the lower the pH, the better, and the lower the SV, the better. However, setting these factors as described above in order to improve the reaction rate is a negative direction from the viewpoint of economy.
Increasing the temperature and lowering the pH will increase the cost required, and lowering the SV will require larger equipment since the throughput per unit time will decrease. Therefore, 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 solution containing selenium and other metal inorganic acid salt into contact with the iron-based metal while keeping the pH of the solution in the contact layer at 3 to 7, generally, the pH of the undiluted solution is used. Is set to 3 to 4, and a liquid filled with a fibrous metal having a fiber diameter of 10 to 100 μm at a packing density of about 0.01 to 0.5 g / ml at about SV 1 to about 10 may be passed. If the pH cannot be maintained 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 amount of charged iron or the surface area per unit volume of iron may be reduced.

As one method for carrying out the method of the present invention, there is a method of adjusting the pH of a solution containing selenium and another metal inorganic acid salt and adding the solution to a column filled with an iron-based metal. Thus, generally, when an iron-based metal is brought into contact with an acidic solution, protons are consumed over time, and the pH is lowered.
The value may rise gradually and exceed the range of 3 to 7, which is the pH at which selenium can be optimally removed. In this case, even if the height of the packed bed 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 the flow rate of the iron-based metal in the column, the pH value in the column is maintained in a range of 3 to 7 in which selenium can be optimally removed, and selenium is removed in that state. preferable.

Further, metallic iron is first oxidized to Fe (II) upon contact with the selenium-containing solution. In a region where the pH in the contact layer exceeds 7, a precipitate of iron (II) hydroxide is formed. Precipitates hinder column processing. Therefore, it is preferable to control the pH value to 7 or less also in this regard. In the column method, in order to suppress the increase in pH in the contact layer and maintain the pH in a preferable range, increase the flow rate of the solution or reduce the amount of the iron-based metal charged, in other words, reduce the amount of the charged iron-based metal. What is necessary is just to reduce the surface area of the iron-based metal used. According to this method, since selenium can be removed while suppressing the amount of consumed iron-based metal, the processing amount of the selenium-containing solution per iron-based metal amount is large, which is 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 and buffering action of the solution containing selenium and other metal inorganic acid salts. You just have to select

In particular, as described above, the solution containing a metal inorganic acid salt other than selenium is a weak acid strong base salt,
Strong acid weak base salt, a solution containing a weak acid weak base salts and / or metal complex salts, i.e., acid dissociation constant of 10-2 ^{2-10 -10}
If the solution contains a substance in the range of
Often it is necessary to control the value. In such a case, the consumption of metallic iron by acid increases even near neutral, and p
The H 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 above-mentioned pH value to 3 to 7. This is a weak acid strong base salt,
This is because the pH behavior of the solution containing the strong acid weak base salt, the weak acid weak base salt and / or the metal complex salt is different from that of the strong acid strong base salt. FIG. 1 shows an outline of a titration curve of a representative strong acid strong base salt type (NaCl) and a strong acid weak base salt type (NH ₄ Cl). In the present invention, it is preferable that the 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. In addition, drainage from a thermal power plant often shows such behavior.

If the treatment with the iron-based metal of the solution containing selenium and another metal inorganic acid salt cannot be reduced to a predetermined selenium concentration by one column treatment, the selenium and other selenium obtained by the primary treatment are not used. The pH value of the solution containing the metal inorganic acid salt is adjusted to 3 to 7 and the process comprising the pH adjustment of the solution and the contact treatment is repeated a plurality of times so that the solution is brought into contact with the packed bed of the iron-based metal. Value can be achieved. Usually, the operation steps may be repeated 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.

In order to obtain the same effect as performing the contact treatment with the packed bed of iron-based metal a plurality of times using a single column,
When a selenium-containing solution is allowed to flow in a packed bed of an iron-based metal, a method in which an acid is added to the packed bed column while passing through the packed bed 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, it is preferable to use a column capable of adding the solution from the middle of the packed bed as the packed bed column and add the acid from the middle of the column.
The number of portions to which the acid is added to the column is not limited, 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 the iron-based metal can be performed not only by the column method using a packed bed of the iron-based metal but also by a batch method. In this case, using a reaction vessel capable of stirring the iron-based metal, adding a solution containing selenium and other metal inorganic acid salts and a dilute acid, and stirring at a temperature of 30 ° C. or higher, the pH during the contact treatment is adjusted to 3 What is necessary is just to contact with a ferrous metal in the state kept within the range of ~ 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, since the removal of selenium by the catalytic reduction reaction of selenium with iron is promoted by oxygen dissolved in the liquid to be treated,
The contact treatment between the metal such as iron and the liquid to be treated is preferably performed in an oxygen-containing atmosphere such as air.

Further, a preferable treatment solution in the method of the present invention is a flue gas desulfurization wastewater of a coal-fired power plant, which is a wastewater containing selenium and a buffer component. In general, when treating such selenium compounds by bringing such wastewater into contact with an iron-based metal, the treatment becomes more difficult than wastewater containing no other buffer component. On page 1083 of Thermal Power Nuclear Power Plant, Vol. 35, No. 10, 1984, an example of the water quality of flue gas desulfurization effluent of a coal-fired power plant is shown. According to this, F, SO4, Cl, Ca, Mg, Al, and B exist. Here, Al and B are substances that may have a buffering action near neutrality, and the thermal nuclear power generation, Vol. 35, No. 10 (1984), p.
m and B are shown to be present at 10 to 130 ppm. This amount is sufficient to exhibit a buffering action near neutrality, and the present invention indicates that this component inhibits removal of selenium compounds from flue gas desulfurization effluent by contact with a selenium removing agent. The people have found it.

Then, after removing a boron compound and / or an aluminum compound from the wastewater containing selenium, which exhibits a buffering action near neutrality and is generally contained in the waste liquid, A treatment agent capable of reducing and removing selenium compounds from neutral to acidic side, that is, a method capable of efficiently removing selenium compounds by contacting with a ferrous metal was established.

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 a coexisting salt.
Specific examples include Diaion CRBO2 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.
H is preferably contacted in the vicinity of 4 to 12, and the contact is carried out at a normal temperature and a flow rate of SV = 1 to 50.

As for the removal of the aluminum compound, removal by a chelating resin, removal by coagulation sedimentation, and the like can be considered, but removal by coagulation precipitation is effective. In the coagulation sedimentation method, it suffices to neutralize with an acid or an alkali, precipitate an aluminum compound as a hydroxide, and perform solid-liquid separation. The solution obtained above is subsequently subjected to a step of removing a selenium compound. In the present invention, the selenium compound is removed by bringing the selenium compound into contact with a treating agent capable of reducing and removing the selenium compound from the neutral to acidic side. Treatment agents having the ability to reduce and remove selenium compounds from neutral to acidic side include iron-based metals, hydrazine, thiourea, borohydride compounds, reducing agents such as anthrahydroquinone and its supporting resin, zinc And other metals such as copper, and reducing salts such as copper (I) salt and Fe (II) salt. In the present invention, it is preferable to use an iron-based metal.
When the contact with the iron-based metal is performed, in this step, the type of the iron-based metal, the contact method, and the like can be used without particular limitation. For example, the pH of the solution obtained in the previous step is adjusted as necessary. However, a column method in which this is added to a column filled with an iron-based metal as described above can be employed.

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 incineration. This incineration method is not particularly limited, and any type of selenium can be used as long as selenium can be easily recovered from incineration residues such as a rotary incinerator such as a rotary kiln and a crucible-type incinerator. Can be. Further, a method in which a dilute acid is brought into contact with a metal surface on which selenium has been deposited, and selenium which has come off is recovered as a solid can also be employed. In this case, 0.01 to 6N hydrochloric acid may be passed through the column to separate solid selenium that is separated with the dissolution of iron from the column.

It is also possible to adopt a method in which the metal adsorbing selenium is taken out of the column and brought into contact with 0.01 to 6N HCl by a batch method to separate and collect solid selenium that is peeled off 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 simple substance, but only by dissolving a part of the iron component, solid selenium peels off, Can be recovered. Generally, if 1% by weight or more of the iron component is dissolved, solid selenium can be peeled off and recovered. Since the solid selenium to be separated is powdery, the iron-based metal and the solid selenium may be separated from each other by separating fibrous or other massive iron from a mixture of both, and a magnetic separation method can also be used.

In addition, a method of separating selenium coming off by subjecting the metal on which selenium is precipitated to ultrasonic treatment,
A method of separating selenium separated by passing hot water through a metal on which selenium has been deposited is used. In the ultrasonic treatment, there is no particular limitation, but the transmission frequency is 20 to 10.
0 KHz and a processing time of 1 to 30 minutes are preferably used. The higher the temperature is, the more effective it is, but it is not particularly limited. Since selenium does not have a strong adsorption force on the metal surface, a method of removing selenium by some physical action is also used without limitation.

It is known that the reactivity of the iron-based metal used for treating the selenium-containing waste liquid gradually decreases. This is because the reaction is caused by a surface reaction,
This is because the surface of the iron-based metal is covered with an inert reactant due to the precipitation of solid selenium on the surface of the iron-based metal and the formation of iron oxide on the surface of the iron-based metal. Therefore, the reactivity of the iron-based metal is increased by contacting the iron-based metal with the selenium adsorbed with the dilute acid or removing the solid selenium by ultrasonic treatment or the like. Therefore, the method of recovering selenium by contact with a dilute acid, ultrasonic treatment, and the like also have the effect of regenerating the iron-based metal at the same time. In particular, contact with a dilute acid is effective for regenerating an iron-based metal.

In the treatment of selenium-containing wastewater, when the reactivity decreases, the reactivity can be prevented from decreasing by changing the reaction conditions over time. Regarding the reaction conditions, at the stage where the reactivity decreases, that is, at the stage where the leaked selenium concentration increases, the reactivity can be increased by increasing the temperature after treatment, decreasing the pH of the treatment solution, or decreasing the SV. The reactivity can be raised to the same level as before the reduction. Changing these conditions is more effective when used in combination, thereby extending the life of the iron-based metal and increasing the amount of processing solution per weight of the iron-based metal. Also, at this time, since decreasing the pH also has the effect of regenerating the iron-based metal, a method of temporarily lowering the pH to remove selenium while regenerating the iron-based metal, and then returning to the original pH again. Can also be employed.

In the method of the present invention, iron ions are eluted in the solution after the treatment. If iron ion elution is a problem,
A method of removing as a precipitate by adding an alkali, a method of removing with a chelate resin, a method of removing with an ion exchange membrane, a method of removing with manganese sand, and the like can be used. Further, by making the pH of the selenium-containing solution relatively high, elution of iron ions can be suppressed. In addition, there is a method of separating selenium that separates by subjecting selenium-precipitated metal to ultrasonic treatment, and a method of separating selenium that separates by passing hot water through the selenium-precipitated metal. No. Since selenium does not have a strong adsorption force on the metal surface, a method of removing selenium by some physical action is also used without limitation. The treatment method of the present invention is carried out in combination with a conventional method such as a neutralization precipitation method for recovering selenium, an iron hydroxide precipitation method, a ferrite precipitation method, an ion exchange membrane treatment method, and an activated carbon adsorption method, if necessary. be able to.

[0043]

EXAMPLES 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 of the present invention is not exceeded.

Example 1 1.65 g of steel wool (φ0.04 mm, trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) was packed in a jacketed glass column (inner diameter 11 mm, height 120 mm, column volume 12 ml) ( Iron surface area: 0.0127 m ² / g iron, per iron column volume: 0.00175 m ² / ml, iron column loading: 0.138 g / ml), 3000 ppm sodium sulfate adjusted to pH 4 (sulfuric acid equivalent) and selenic acid A solution containing 5 ppm of sodium (in terms of selenium) was passed through the column in an upward flow at a flow rate of SV = 5. The jacket temperature was maintained at 50 ° C. during the passage. 10B. V. The concentration of selenium in the solution after the passage was 3.2 ppm. The selenium concentration was measured by an ICP emission method.

Example 2 The procedure of Example 1 was repeated, except that the temperature of the jacket was kept at 80 ° C. As a result, 10B.
V. The concentration of selenium in the solution after the passage was 0.7 ppm.

Comparative Example 1 The procedure of Example 1 was repeated except that the temperature of the jacket was maintained at 20 ° C. As a result, 10B.
V. The concentration of selenium in the solution after the passage was 5.0 ppm, and selenium in the solution was hardly removed.

Example 3 A jacketed glass column (inner diameter 11 mm, height 100 mm, column volume 10 ml) was filled with 1.0 g of steel wool (φ0.025 mm, trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.). Iron surface area: 0.021 m ² / g-iron, per iron column volume: 0.0021 m ² / ml, iron column loading: 0.10 g / ml), 5000 ppm sodium sulfate adjusted to pH 4 (sulfuric acid equivalent) and selenic acid sodium
A solution containing 0.5 ppm (in terms of selenium) was passed through the column in an upward flow at a flow rate SV = 2. The jacket temperature was maintained at 50 ° C. during the passage. 20B. V. The concentration of selenium in the solution after the passage was 0.01 ppm or less. The selenium concentration was measured by an ICP emission method.

Example 4 Example 4 was repeated except that the diameter of the steel wool was changed to φ0.04 mm (surface area of iron: 0.013 m ^2).
/ G-iron, per iron column volume: 0.0013 m ² / ml, iron column loading: 0.10 g / ml). 20B. V. The concentration of selenium in the solution after the passage was 0.10 ppm.

Example 5 In Example 3, the fiber diameter was changed to 0,0 instead of steel wool.
The procedure was the same except that a 5 mm iron wire (0.5 mm metal wire: manufactured by Mitsui Chemicals, Inc.) was used (surface area of iron: 0.001 m ² / g-iron, per column volume of iron: 0.000).
1 m ² / ml, iron column loading: 0.10 g / ml). 20
B. V. The concentration of selenium in the solution after passage is 0.47 ppm
Met.

Example 6 1.50 g of steel wool (φ0.04 mm, trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) was packed in a jacketed glass column (inner diameter 11 mm, height 120 mm, column volume 12 ml) (iron-free). Surface area: 0.0127 m ² / g-iron, per iron column volume; 0.00158 m ² / ml, iron column loading: 0.125 g / ml,
A solution containing 5000 ppm of sodium sulfate (converted to sulfuric acid) and 0.5 ppm of sodium selenate (converted to selenium) adjusted to pH 4 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 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 quantified by ICP emission. Table 1 shows the results. After passing the solution up to 800 BV, the leak of selenium was reduced by lowering the pH to 3, and the leak of selenium remained lowered even after the pH was returned to 4.

[0051]

[Table 1]

Example 7 1.50 g of steel wool (φ0.04 mm, trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) was packed in a jacketed glass column (inner diameter: 11 mm, height: 120 mm, column volume: 12 ml). Surface area: 0.0127 m ² / g-iron, per iron column volume; 0.00158 m ² / ml, iron column loading: 0.125 g / ml,
A solution containing 5000 ppm of sodium sulfate (converted to sulfuric acid) and 0.5 ppm of sodium selenate (converted to selenium) adjusted to pH 3 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 80 ° C. In this test, 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. Table 2 shows the results.

[0053]

[Table 2]

Example 8 1.50 g of steel wool (φ0.04 mm, trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) was packed in a jacketed glass column (inner diameter: 11 mm, height: 120 mm, column volume: 12 ml). Surface area: 0.0127 m ² / g-iron, per iron column volume; 0.00158 m ² / ml, iron column loading: 0.125 g / ml,
A solution containing 100 ppm of sodium sulfate (converted to sulfuric acid) and 5 ppm of sodium selenate (converted to selenium) adjusted to p4 was passed through the column at an upward flow rate of SV = 5. During the passage, the temperature of the jacket was maintained at 50 ° C. 20 in this test
The solution was passed until 00B.V. The selenium concentration in the solution after passing through 2000 B.V. was 0.37 ppm. The selenium concentration was determined by ICP
The light emission method was used. 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 HCl, and shaken at 50 spm for 30 minutes. At this time, a red-brown solid component was released from the steel wool. Magnetic separation of iron component from this liquid,
The remaining precipitate 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. In addition, regarding the filtered component, 10% with a Dimroth condenser
Put in 0 ml eggplant type flask, add 5 ml of concentrated nitric acid and stir at 90 ° C
For 30 minutes 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. As a result, the selenium concentration was 14.9 ppm and the iron concentration was 11.2 ppm.

Example 9 A part of the steel wool having a weight of about 1/6 was extracted with respect to the steel wool after the passage of the selenium solution carried out in Example 8, and 10 parts thereof were removed.
0 ml Erlenmeyer flask, add 50 ml of 1N HCl,
Shake at 50 spm for 30 minutes. At this time, a red-brown solid component was released from the steel wool. The iron component was magnetically separated from this solution, and the remaining precipitate component was filtered with a 0.45 μm nitrocellulose membrane filter. The selenium concentration in the filtrate was 0.1 ppm or less, and the iron concentration was 1580 ppm. In addition, about the filtered component, put in a 100 ml eggplant type flask with a Dimroth condenser, 5 ml of concentrated nitric acid.
Was added and 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. The reaction solution was cooled and 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 1/6 of the weight of the steel wool after passing through the selenium solution carried out in Example 8 was removed and
The mixture was placed in a 0 ml Erlenmeyer flask and further added with 50 ml of demineralized water, and treated with an ultrasonic cleaner (frequency: 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 precipitate component was filtered with a 0.45 μm nitrocellulose membrane filter. The selenium concentration in this filtrate is 0.1p
pm or less, and the iron concentration was 0.1 ppm or less. In addition, about filtered component, 100 ml with Dimroth condenser
Put into a eggplant-shaped flask, add 5 ml of concentrated nitric acid, and stir at 90 ° C under stirring.
Reaction was carried out for 0 minutes 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 20.6 ppm and the iron concentration was 76.8 ppm.

COMPARATIVE EXAMPLE 2 About one sixth of the weight of the steel wool after the passage of the selenium solution carried out in Example 8 was extracted, and
In a 0 ml Erlenmeyer flask, 50 ml of 0.001N HCl was further added, and the mixture was shaken at 50 spm for 30 minutes. At this time, no solid component was released from the steel wool. The iron component was magnetically separated from this solution, and the remaining precipitate component was 0.45 μm
The solution was filtered through a nitrocellulose membrane filter. The selenium concentration in this filtrate is 0.1 ppm or less, and the iron concentration is 37.6 ppm
Met.

Example 11 1.0 g of steel wool (φ0.04 mm, trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) was filled into a jacketed glass column (inner diameter 11 mm, height 100 mm, column volume 10 ml) ( Iron surface area: 0.0068 m ² / g-iron, per iron column volume: 0.00063 m ² / ml, iron column loading: 0.05 g / ml), and 0.50 ppm of sodium selenate adjusted to pH 4 (in terms of selenium). A 50 mM phosphate buffer (selenium-containing solution) was passed through the column at an upward flow rate at a flow rate of 50 ml / hour. The jacket temperature was maintained at 50 ° C. during the passage. 20B. V. The concentration of selenium in the solution after the passage was 0.25 ppm. The pH at this time was 6.5.

Example 12 As a primary treatment, the same method as in Example 11 was performed. This outlet liquid (selenium concentration: 0.25 ppm) was adjusted to pH 4 with hydrochloric acid, used as a secondary treatment liquid to be added to the column, and passed through the same column again in the same manner as in Example 3. 20B.
V. The selenium concentration in the solution after the passage was 0.08 ppm.
The pH at this time was 6.3.

Example 13 The columns used in Example 11 were connected in series in two stages and adjusted to pH 4 with 0.50 ppm of sodium selenate (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 passage. 20B.
V. The concentration and pH of selenium in the solution after the passage were 0.25 ppm of selenium and pH 6.5 at the outlet of the first column, and 0.21 ppm and pH 7.8 of selenium at the outlet of the second column.

Comparative Example 3 The columns used in Example 11 were connected in series in three stages and adjusted to pH 4 with 0.50 ppm of sodium selenate (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 passage. 20B.
V. The concentration and pH of selenium in the solution after the passage were as follows: the selenium concentration of 0.25 ppm and pH 6.5 at the outlet of the first column, the selenium concentration of 0.21 ppm and pH 7.7 at the outlet of the second column, and the selenium concentration at the outlet of the third stage. It was 0.21 ppm and pH 8.1.

Example 14 In Example 13, at the inlet of the second stage column, 0.5 ml / hour of 0.1 N HCl was continuously added in addition to the treatment solution. 20B.
V. The selenium concentration and pH in the solution after the passage were 0.25 ppm and pH 6.3 at the outlet of the first column and 0.09 ppm and pH 6.6 at the outlet of the second column.

Example 15 Steel wool (φ0.04 mm:
Product name Bonstar: Nippon Steel Wool Co., Ltd.)
0 g and distilled water (50 ml) were added, and 50 rpm
m. Here, sodium selenate 0.50pp
m (in terms of selenium), a mixture of sodium sulfate 1000 ppm (in terms of sulfuric acid) was added at 50 ml / hour, and
The reaction solution was removed from the system at 1 / hour. Here, the pH in the reactor was adjusted to 4 to 4 by appropriately adding 0.1N HCl.
A range of 6 was maintained. One liter of the solution was treated and its selenium concentration was 0.06 ppm.

Comparative Example 4 In Example 15, the pH in the reactor was changed to 0.1N HCl and 0.1%.
A method similar to that of Example 15 was performed, except that the pH value was maintained at 9 to 10 by appropriately adding 1NNaOH. One liter of the solution was treated and its selenium concentration was 0.50 ppm.

Example 16 200 ml of a solution containing 10 ppm of sodium selenate (in terms of selenium) and 500 ppm of sodium tetraborate (in terms of boron)
H7) boric acid selective resin DIAION CRBO2
(Mitsubishi Chemical Corporation) 100 ml packed column (26 m inner diameter)
The liquid was passed through m) at SV = 2. The concentration of boron in the solution after passage is 1
ppm or less. The solution was adjusted to pH 3 with hydrochloric acid,
0ml into a four-necked flask, and add steel wool (φ
0.04mm: Product name Bonstar: Nippon Steel Wool Co., Ltd.
0.20 g), heated to 50 ° C. in a water bath, and reacted with 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 0.3 ppm. The selenium concentration was measured by an ICP emission method.

Example 17 A 200 ml solution containing 10 ppm of sodium selenate (in terms of selenium) and 500 ppm of sodium tetraborate (in terms of boron) was adjusted to pH 3 with hydrochloric acid, and placed in a 300 ml four-necked flask. (Φ0.04mm: trade name Bonstar: manufactured by Nippon Steel Wool Co., Ltd.)
C. and reacted under stirring. The selenium concentration at a reaction time of 4 hours was 7.8 ppm. The selenium concentration was measured by an ICP emission method.

Example 18 A 500 ml solution (adjusted to pH 7) containing 0.5 ppm of sodium selenate (in terms of selenium), 5000 ppm of sodium sulfate (in terms of sulfate ion), and 250 ppm of boric acid (in terms of boron) was prepared using boric acid-selective resin Diaion. CRBO2 (Mitsubishi Chemical Corporation) 5
The solution was passed through a column packed with 00 ml (inner diameter: 45 mm) at SV = 1.
The boron concentration in the solution after the passage was 10 ppm or less. The pH of this solution was adjusted to 4 with hydrochloric acid, and steel wool (φ0.0
4mm: Product name Bonstar: Nippon Steel Wool Co., Ltd.
Column with a jacket filled with 1.0 g
The solution was passed through an upward flow at a height of 100 mm and a column volume of 10 ml) at SV = 2. During the passage, the temperature of the jacket was set to 50 ° C. 500ml
The selenium concentration during the passage was 0.1 ppm.

Example 19 A 500 ml solution containing 0.5 ppm of sodium selenate (in terms of selenium), 5000 ppm of sodium sulfate (in terms of sulfate ion) and 250 ppm of boric acid (in terms of boron) was adjusted to pH 4 with hydrochloric acid.
Liquid is passed through a jacketed column (inner diameter 11 mm, height 100 mm, column volume 10 ml) filled with 1.0 g of steel wool (φ0.04 mm, trade name: Bonstar: manufactured by Nippon Steel Wool Co., Ltd.) at SV = 2 in an upward flow. did. During the flow, the jacket temperature is
50 ° C. The selenium concentration at the time of passing 500 ml of liquid was 0.13 ppm.

[0069]

According to the method of the present invention, wastewater containing other inorganic acid salts such as alkali metal sulfates, boron compounds and other compounds having a buffering action near neutrality in a solution can be easily prepared. Processing can be performed efficiently by the processing operation, and the selenium concentration can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing titration curves of NaCl and NH ₄ Cl.

 ──────────────────────────────────────────────────続 き Continuation of the front page (31) Priority claim number Japanese Patent Application No. 9-296872 (32) Priority date Hei 9 (1997) October 29 (33) Priority claim country Japan (JP) (31) Priority Claim No. Japanese Patent Application No. 9-321021 (32) Priority Date Hei 9 (1997) November 21 (33) Priority Country Japan (JP) (72) Inventor Koji Kusaba 1 Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kawasaki, Kanagawa Prefecture No. 2 Kawasaki Chemical Industry Co., Ltd. (72) Inventor Tatsuya Sakurai No. 1-2 Chidoricho, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Kawasaki Chemical Industry Co., Ltd.

Claims (32)

[Claims] 1. 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. 2. The method for treating a selenium-containing solution according to claim 1, wherein the selenium-containing solution is brought into contact with an iron-based metal. 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 according to claim 1, wherein the solution containing selenium and another metal inorganic acid salt flows through the packed bed of the iron-based metal in an upward flow. A method for treating a selenium-containing solution. 5. When a solution containing selenium and another metal inorganic acid salt is brought into contact with a packed bed of an iron-based metal, the contact is carried out while maintaining the pH value of the solution in the packed bed at 3 to 7. A method for treating a selenium-containing solution according to any one of claims 1 to 4. 6. A process comprising adjusting a pH value of a solution containing selenium and another metal inorganic acid salt to 3 to 7 and bringing the solution after the pH adjustment into contact with a packed bed of an iron-based metal. The method for treating a selenium-containing solution according to claim 1, wherein the method is repeated a plurality of times. 7. When flowing a solution containing selenium and another metal inorganic acid salt through a packed bed of an iron-based metal, an acid is added to the packed bed to adjust the pH value of the solution in the bed to 3 to 7. The method for treating a selenium-containing solution according to claim 1, wherein the selenium-containing solution is retained. 8. A reaction vessel containing an iron-based metal, a solution containing selenium and another metal inorganic acid salt and a dilute acid are added, and p is added.
A method for treating a selenium-containing solution, wherein a contact reaction is performed at a temperature of 30 ° C. or more while stirring while maintaining the H value at 3 to 7. 9. The method 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.
The method for treating a selenium-containing solution according to any one of claims 8 to 10. 10. The method for treating a selenium-containing solution according to claim 9, wherein the iron-based metal is fibrous. 11. The method for treating a selenium-containing solution according to claim 9, wherein the iron-based metal is formed into a fibrous shape by a cutting method. 12. The method for treating a selenium-containing solution according to claim 9, wherein the iron-based metal is fibrous having a diameter of 0.01 to 0.3 mm. 13. 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. 15. The iron-based metal has a surface area of 0.001 m ^2.
The method for treating a selenium-containing solution according to any one of claims 1 to 14, wherein the iron is not less than / g. 16. The iron-based metal according to claim 1, wherein the iron has a surface area per column volume of iron of 0.0001 m ² / ml or more. For treating a selenium-containing solution. 17. An iron-based metal having a loading on a column of 0.1.
The method for treating a selenium-containing solution according to any one of claims 1 to 7, and 9 to 16, wherein the concentration is from 01 g / ml to 3 g / ml. 18. The method according to claim 1, wherein the solution containing selenium and another metal inorganic acid salt is a solution containing a sulfate ion having a concentration of 100 times or more the selenium concentration. A method for treating a selenium-containing solution as described in the above. 19. The solution according to claim 1, wherein the solution containing selenium and another metal inorganic acid salt 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. The method for treating a selenium-containing solution according to any one of claims 4 to 18. 20. The weak acid strong base salt, strong acid weak base salt, weak acid weak base salt and / or metal complex salt, wherein the ammonium salt, carbonate, phosphate, borate, carboxylate, aluminum complex, copper complex, The method for treating a selenium-containing solution according to claim 19, which is a cobalt complex salt and / or an iron complex salt. 21. 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 more to precipitate selenium on the surface of the iron-based metal; A method for treating a selenium-containing solution, comprising a step of subjecting selenium deposited on the surface of the base metal to incineration or peeling treatment and collecting the selenium. 22. The method for treating a selenium-containing solution according to claim 21, wherein the stripping treatment is a contact with a dilute acid or an ultrasonic treatment. 23. The ferrous metal is regenerated by contact with a dilute acid or ultrasonic treatment.
Or a method for treating a selenium-containing solution according to 22. 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 more to precipitate selenium on the surface of the iron-based metal. A step of recovering the selenium deposited on the surface of the metal by incineration or peeling treatment, and raising the solution temperature in accordance with a decrease in the selenium recovery capacity in the step;
A method for treating a selenium-containing solution, comprising a step of lowering the value and / or lowering the solution passing rate. 25. When treating a solution containing a selenium compound and containing a compound having a buffer action near neutral, the compound having a buffer action near neutral is removed from the solution. A method for treating a selenium-containing solution, comprising: a step of contacting the solution with a treating agent capable of reducing and removing the selenium compound from a neutral to an acidic side to remove the selenium compound. 26. After the step of removing a compound having a buffering action near neutral, the step of removing the selenium compound by contacting with a treating agent capable of reducing and removing the selenium compound from neutral to acidic side. 26. The method according to claim 25, wherein
A method for treating a selenium-containing solution as described in the above. 27. The method for treating a selenium-containing solution according to claim 25, wherein the treating agent having an ability to reduce and remove a selenium compound from a neutral to an acidic side is an iron-based metal. 28. A compound having a buffering action near neutrality,
The method for treating a selenium-containing solution according to any one of claims 25 to 27, wherein the method is a boron compound and / or an aluminum compound. 29. A compound having a buffering action near neutral,
29. A boron compound.
The method for treating a selenium-containing solution according to any one of the above. 30. The method for treating a selenium-containing solution according to claim 29, wherein the compound having a buffer 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 compound having a buffering action near neutrality is an aluminum compound, and the aluminum compound is removed by a coagulation sedimentation treatment.
29. The method for treating a selenium-containing solution according to any one of claims 28 to 28.