JP3814263B2 - Separation and recovery of iron and manganese coexisting in water - Google Patents

Description

【００２５】
試験番号３〜５が本発明に相当する方法である。いずれの試験でも除鉄塔で鉄分は除去されるがマンガンは除去されずに通過し、最終的に除マンガン塔では鉄もマンガンもほぼ完全に除去されていることが分かる。特に試験番号３〜４のように、ｐＨを５．５〜６．０に調整するのが最適である。このようにすると、除鉄塔出口での被処理水中での鉄分濃度は極めて小さく（大部分の鉄分が除去されている）且つマンガン濃度には殆ど変化がない（大部分のマンガンは捕捉されていない）ことが分かる。つまり、鉄分は除鉄塔で、マンガンは除マンガン塔で、それぞれ別々に吸着除去されており、分離の目的が達成されている。
【００２６】
それに対して、試験番号１〜２では、除鉄塔で鉄分とともにかなりの量のマンガンも除去されてしまい、分離回収の目的が達成されていない。逆に試験番号６〜７では、除鉄塔で鉄分の除去が不十分であり、残った鉄分が除マンガン塔で除去されており、同様に、分離回収の目的が十分には達成されていない。なお、試験番号５〜７で除鉄塔出口液のマンガン濃度が入口液（被処理水）のそれよりも増加したのは、過去の試験で除鉄用濾過材に付着していたマンガン分が溶出したためと考えられる。
【００２７】
この実施例ではラジウムを用いた例は示していないが、前述のように、マンガン及びラジウムを含む水に、酸化目的で次亜塩素酸ナトリウム溶液を加え、酸化マンガンが被着している濾過材に接触させると、濾過材表面に酸化マンガンを付着させつつラジウムを選択的に吸着除去できるのであるから、本発明方法によって被処理水から先ず鉄分のみを分離除去し、その後、マンガン及びラジウムを吸着除去できることになる。
【００２８】
【発明の効果】
本発明は上記のように、水のｐＨ５．０〜６．０に調整し、空気吹き込みにより鉄のみを空気酸化さながら除鉄用濾過材と接触させることにより、鉄を吸着除去し、次に水のｐＨを中性付近に調整し、塩素系酸化剤を加えてマンガンを酸化さながら除マンガン用濾過材と接触させてマンガンを除去する方法であるから、鉄とマンガン（及びラジウム）とを容易にしかも確実に分離することができ、長期間にわたって安価に操業できる。
【００２９】
また本発明は、鉄が付着した除鉄用濾過材とマンガンが付着した除マンガン用濾過材とに対して、それぞれ清水により逆洗操作を行い、逆洗水に含まれる成分をそれぞれ分別回収する方法であるから、鉄とマンガンを分離回収することができる。特に被処理水が、鉄とマンガン及びラジウムを含む場合には、鉄を含むスラリーとマンガン及びラジウムを含むスラリーに分離回収できる。そのため、ラジウムを含む放射性廃棄物量を低減することができ、保管に係わる負担の軽減化を図ることができる。
【図面の簡単な説明】
【図１】本発明に係る鉄とマンガンの分離回収方法の一例を示すフロー図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for separating and recovering iron and manganese coexisting in water, and more specifically, first, only iron content is removed by a iron removal tower by pH control and an appropriate oxidation method of water to be treated. The present invention relates to a method for separating and recovering iron and manganese coexisting in water, in which manganese is removed by a manganese removal tower so that iron and manganese can be reliably separated and recovered separately. This technique is useful for reducing the amount of waste containing radioactive substances, particularly in the treatment of wastewater containing radium.
[0002]
[Prior art]
For example, in the treatment of uranium slag, the treatment of uranium waste containing radium, the treatment of contaminated soil containing radium, or the treatment of uranium waste containing radium, it is inevitably or contrary to the treated water. A state containing radium may occur. The discharge standard for radium concentration in the treated water is currently regulated to 3.0 Bq / L by the Reactor Regulation Law. However, depending on the region, there are some establishments that are regulated to stricter emission standards (for example, 0.037 Bq / L or less) by additional standards with local governments.
[0003]
Conventionally, as a method for treating wastewater containing radium, there is a method in which barium chloride and sulfuric acid or sulfate are added to the wastewater, and coprecipitation is removed by the generated barium sulfate. However, this coprecipitation method has problems such as large environmental load such as handling chemicals designated as deleterious substances, large space for sedimentation basins and filtration facilities, and a large amount of solid waste containing radium. is there.
[0004]
As another treatment method, a method of selectively adsorbing and removing radium using an ion exchange resin is known. However, ion exchange resins used as adsorbents are expensive. Therefore, in order to reduce the cost, the adsorbent (ion exchange resin) is generally regenerated and used repeatedly. However, since radium has low utility value as a resource, the radium eluent generated in the regeneration process is treated as waste by being treated by a coprecipitation method using barium sulfate or the like. Therefore, a processing facility for that purpose is required separately, and it is not a satisfactory problem solving method.
[0005]
As a technique that can solve such problems, the inventors previously added a sodium hypochlorite solution to water containing manganese and radium for the purpose of oxidation, and contacted the filter medium on which manganese oxide was deposited. Then, it was found that radium can be selectively adsorbed and removed while adhering manganese oxide to the surface of the filter medium, and a method for removing radium in water based on this was proposed (see Japanese Patent Application No. 2001-389244). This method has an advantage that radium can be adsorbed and removed efficiently over a long period of time because manganese oxide continues to adhere to the particle surface.
[0006]
However, when iron is contained in the water to be treated, iron is also adsorbed by the filter medium together with manganese and radium. For this reason, the amount of adsorbed material on the filter medium increases, and the pressure loss during water flow to the filter device (column) increases. Therefore, in such a case, it is desirable to previously remove iron from the water to be treated as a pretreatment for removing the manganese and radium in the water.
[0007]
[Problems to be solved by the invention]
In adsorption removal of manganese and radium in water, it has been proved that it is desirable to remove iron existing in water in advance as described above. Various methods for removing iron in water are known, and no particular problem arises in a small-scale implementation such as a laboratory scale. However, in a large-scale and long-term implementation, a method for efficiently removing only iron has not been developed yet.
[0008]
As a simple method for removing iron present in water, there is an adsorption removal method using an oxidation catalytic action of a filter medium. For example, iron is air-oxidized by blowing air into the water to be treated, or iron is oxidized by adding an oxidizing agent (such as sodium hypochlorite solution) to the filter medium or particle surface made of ferric hydroxide. This is a method of adsorbing with a filter medium coated with iron oxyhydroxide. This method can also be applied to large scale implementations.
[0009]
However, in this treatment method, when manganese coexists in water, not only iron but also manganese is adsorbed simultaneously. Therefore, if adsorption removal of iron in the water to be treated containing manganese and radium is continued for a long period of time, manganese oxide adheres to the surface of the filter material for iron removal, and therefore radium is also adsorbed together. .
[0010]
However, since radium is a radioactive substance, waste generated in the process is managed separately from general waste, so that the burden on storage is required to be reduced. However, in the above method, manganese and radium are adsorbed on the same filter medium together with iron, so that they cannot be separated and recovered, so that the amount of waste increases and disposal / storage becomes difficult.
[0011]
An object of the present invention is to provide a method capable of easily and reliably separating and recovering iron and manganese contained in water. Another object of the present invention is to provide a method capable of reducing the amount of waste containing radium and reducing the burden on storage by making it possible to separate iron, manganese and radium. It is.
[0012]
[Means for Solving the Problems]
The present inventors do not add an oxidizing agent to the water to be treated in which iron and manganese coexist, but blow air (oxygen) and oxidize the air while removing the air (filtering material that adsorbs iron). )
(A) The degree of adsorption of iron and manganese differs depending on the pH of the water to be treated;
(B) When the pH of the water to be treated is adjusted to the range of 5.0 to 6.0, manganese is hardly adsorbed and remains dissolved in water, but only iron is adsorbed to the filter material for removing iron. thing,
And the present invention has been completed based on this.
[0013]
The present invention relates to an iron removal step of adsorbing iron by adjusting water containing iron and manganese to pH 5.0 to 6.0 and bringing the iron into contact with a filter medium for iron removal while oxidizing only air by air blowing. ,
A manganese removal step of adsorbing manganese by adjusting the pH of the water from which iron has been removed to near neutrality and contacting the filter material for manganese removal while oxidizing manganese by adding a chlorine-based oxidant;
Co-existing in water characterized by performing back-washing operation on the filter material for iron removal and the filter material for manganese removal on which manganese is adhered, and separating and collecting the deposits on each filter medium This is a method for separating and recovering iron and manganese.
[0014]
Further, the present invention adjusts the water containing iron, manganese and radium to pH 5.0 to 6.0, and removes the iron by adsorbing the iron by bringing it into contact with the filter medium for removing iron while air-oxidizing only the iron. Iron process,
A manganese removal step of adsorbing manganese and radium by adjusting the pH of water from which iron has been removed to near neutrality and contacting the filter material for manganese removal while oxidizing manganese by adding a chlorine-based oxidizing agent;
The filter media for removing iron with iron and the filter media for removing manganese with manganese and radium are back-washed with fresh water, and the deposits of each filter media are separated and recovered as a slurry. This is a method for separating and recovering iron and manganese coexisting in water.
[0015]
In these separation and recovery methods, the pH of the water in the iron removal step is in the range of 5.0 to 6.0, but is particularly preferably adjusted to 5.5 to 6.0. As the filter material for removing iron, for example, a filter material in which iron oxyhydroxide is deposited on the particle surface is used. Further, as the filtering material for removing manganese, for example, a filtering material in which manganese oxide is deposited on the particle surface is used.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a flowchart showing an example of a method for separating and recovering iron and manganese according to the present invention. The water to be treated is, for example, mine water generated by past exploration activities, and contains iron in addition to manganese and radium. To this treated water, sulfuric acid or sodium hydroxide solution is added to adjust the pH to 5.0 to 6.0. Next, air is blown into the pipe through which the water to be treated is passed, and the liquid is passed through the iron removal tower to be brought into contact with the filled iron filter material. As a result, only iron is adsorbed to the filter material for removing iron while being oxidized by air. To the water to be treated from which iron has been removed, a sodium hydroxide solution is added to adjust the pH to near neutrality (for example, the pH is 5.8 to 8.6 according to various standards) A chlorinated oxidant (sodium hypochlorite solution or the like) is added, and the solution is passed through a manganese removal tower and brought into contact with the filled filter material for manganese removal. As a result, manganese is adsorbed to the filter material for removing manganese while being oxidized. At the same time, radium is also adsorbed on the filter material for removing manganese. Therefore, iron is first removed by the iron removal tower, then manganese and radium are removed by the manganese removal tower, and finally the treated water from which they have been removed is discharged. Since this treated water has a pH adjusted to around neutral, it can be drained as it is.
[0017]
After a long period of iron removal operation and manganese removal operation, the iron removal filter medium of the iron removal tower has a large amount of iron, and the manganese removal filter medium of the manganese removal tower has a large amount of manganese and radium. Alternatively, the pressure loss increases when the liquid is passed through the manganese removal tower. Accordingly, fresh water is supplied to the iron removal tower and the manganese removal tower, respectively, and the backwashing operation is performed on the iron removal filter medium to which iron is adhered and the manganese removal filter medium to which manganese and radium are adhered. When backwashing operation is performed using fresh water, an iron starch slurry and a manganese / radium starch slurry can be obtained and collected separately. They can be solidified by removing moisture. In addition, since the treated water finally discharged | emitted as mentioned above has removed iron, manganese, and radium, it is preferable to use it for backwash operation as fresh water.
[0018]
By the way, in this invention, it is in order to isolate | separate the iron and manganese contained in to-be-processed water that it is oxidizing in the air at the iron removal process. When air (actually oxygen) is blown into water to be treated whose pH is adjusted to 5.0 to 6.0, the oxidation reaction of manganese proceeds only very slowly, so even if iron is oxidized, most of the manganese is present. The state dissolved in water without being oxidized is maintained. Therefore, manganese is not captured by the filter material for iron removal, and passes through the iron removal tower as it is. The present invention utilizes this phenomenon. The reason why manganese is less likely to be oxidized than iron is that the potential of manganese redox system is higher than the potential of iron redox system. If a chlorine-based oxidant is added instead of air, not only iron but also manganese is rapidly oxidized and deposited as a solid in the iron removal tower, and separation cannot be performed.
[0019]
The waste generated in the separation treatment according to the method of the present invention is a solid separated from the surface of the filter medium generated by backwashing the iron removal tower and the manganese removal tower, and a filter medium that needs to be replaced as performance deteriorates. As described above, since radium is a radioactive substance, it is managed separately from general waste, so that it is required to reduce the burden on storage. In the present invention, since only the iron component is separated and removed in advance by the iron removal tower, the slurry containing iron does not contain a radioactive substance, so that it can be easily disposed of.
[0020]
The filter material for removing iron is, for example, particles in which the surface of filter sand (natural hard quartz sand that has been screened to obtain a particle size distribution suitable for filtration while being washed with water) is coated with iron oxyhydroxide. It is. Filter sand also has a function of capturing suspended substances suspended in water. When water containing iron is filtered through the filter sand, iron oxide is gradually generated on the surface of the filter sand due to dissolved oxygen in the water. This becomes an oxidation accelerator and facilitates removal of iron in water. Therefore, as a filtering material that can efficiently remove iron, particles whose surface is filtered with iron oxyhydroxide are commercially available as a filtering material for iron removal (for example, “Toyolex” manufactured by Tokemi Co., Ltd.). Then, this commercial product can be used as it is.
[0021]
The filter material for removing manganese is, for example, particles in which the surface of filter sand (the hard silica sand produced naturally is sieved to have a particle size distribution suitable for filtration while being washed) is coated with manganese oxide. . In this case, the filter sand also has a function of capturing suspended substances suspended in water. When chlorine is added to water containing manganese and filtered through the filter sand, manganese in the water is oxidized, and manganese oxide is gradually formed on the surface of the filter sand. This becomes an oxidation accelerator and facilitates removal of manganese in the water. This is generally called “manganese sand”. However, depending on the manganese content, it may take several months to several years to become manganese sand. Accordingly, particles obtained by repeatedly treating the filtration sand with manganese chloride and potassium permanganate and coating the surface of the filtration sand with manganese oxide are commercially available as filter media for removing manganese (for example, “Manganese Sand” manufactured by Tochemi Corporation). In the present invention, this commercially available product can be used as it is.
[0022]
The amount of deposits on the filter medium increases with long-term use. As a result, the filtration resistance (pressure loss) increases, so it is necessary to remove and remove flocs and the like adhering to the filter medium by collision or friction between the filter mediums. The operation is backwashing. Deposits can be collected by this backwashing operation. Examples of the backwashing method include surface backwashing, air backwashing, mechanical stirring, and backwashing with a strong water flow. The present invention may be backwashed by any of these methods, but here the backwashing is performed using treated water, and the deposits are recovered as a slurry. That is, iron is recovered as an iron starch slurry by backwashing the iron removal tower, and manganese and radium are recovered as manganese / radium starch slurry by backwashing the manganese removal tower.
[0023]
【Example】
A commercially available filter material for iron removal and a filter material for manganese removal were each packed into a plastic column having an inner diameter of 150 mmφ to constitute a filter device in which two towers of an iron removal tower and a manganese removal tower were connected in series. Sulfuric acid is added to the water to be treated (raw water) containing iron and manganese, the pH is changed in seven stages within the range of 4.0 to 7.3, and the water is passed through. The concentration at the outlet of the iron removal tower and the manganese removal tower The test which measures was performed. In any of the tests, liquid was passed through the iron removal tower at a flow rate of 3 L / min while sending compressed air through the pipe. After adjusting the pH to 7.3 by adding a sodium hydroxide solution to the iron removal tower outlet liquid, the solution was passed through the manganese removal tower at a flow rate of 3 L / min while adding the sodium hypochlorite solution with a pump. The test results are shown in Table 1.
[0024]
[Table 1]

[0025]
Test numbers 3 to 5 are methods corresponding to the present invention. In any test, it is understood that iron is removed in the iron removal tower, but manganese passes through without being removed, and finally iron and manganese are almost completely removed in the manganese removal tower. In particular, as shown in Test Nos. 3 to 4, it is optimal to adjust the pH to 5.5 to 6.0. In this way, the iron concentration in the water to be treated at the exit of the iron removal tower is extremely small (most of the iron is removed) and the manganese concentration is almost unchanged (most of the manganese is not trapped). ) That is, the iron content is removed from the iron removal tower and the manganese content is removed from the manganese removal tower separately, thereby achieving the purpose of separation.
[0026]
On the other hand, in Test Nos. 1 and 2, a considerable amount of manganese is removed together with the iron content in the iron removal tower, and the purpose of separation and recovery is not achieved. On the other hand, in Test Nos. 6 to 7, the removal of iron in the iron removal tower is insufficient, and the remaining iron is removed in the manganese removal tower. Similarly, the purpose of separation and recovery is not sufficiently achieved. In addition, the manganese concentration of the iron removal tower outlet liquid increased more than that of the inlet liquid (treated water) in test numbers 5 to 7 because the manganese content adhering to the iron removal filter material in the previous test was eluted. It is thought that it was because.
[0027]
Although the example using radium is not shown in this embodiment, as described above, a filter medium in which a sodium hypochlorite solution is added to water containing manganese and radium for the purpose of oxidation, and manganese oxide is deposited. , It is possible to selectively adsorb and remove radium while adhering manganese oxide to the surface of the filter medium. Therefore, the method of the present invention first separates and removes only iron from the water to be treated, and then adsorbs manganese and radium. It can be removed.
[0028]
【The invention's effect】
In the present invention, as described above, the pH of water is adjusted to 5.0 to 6.0, and the iron is adsorbed and removed by bringing the iron into contact with the filter material for removing iron while only oxidizing iron by air blowing. This is a method that removes manganese by adjusting the pH of the solution to near neutral and adding a chlorinated oxidant to contact manganese with the manganese removal filter while oxidizing manganese, so iron and manganese (and radium) can be easily removed. Moreover, it can be reliably separated and can be operated at low cost over a long period of time.
[0029]
In addition, the present invention performs a backwash operation with fresh water on the filter material for removing iron and the filter media for removing manganese with adhering manganese, respectively, and separately collects components contained in the backwash water. Since this method is used, iron and manganese can be separated and recovered. In particular, when the water to be treated contains iron, manganese and radium, it can be separated and recovered into a slurry containing iron and a slurry containing manganese and radium. Therefore, the amount of radioactive waste containing radium can be reduced, and the burden on storage can be reduced.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an example of a method for separating and recovering iron and manganese according to the present invention.

Claims (3)

Iron removal step of adsorbing iron by adjusting water containing iron and manganese to pH 5.0 to 6.0 and bringing it into contact with a filter medium for iron removal while oxidizing only air by air blowing,
A manganese removal step of adsorbing manganese by adjusting the pH of the water from which iron has been removed to near neutrality and contacting the filter material for manganese removal while oxidizing manganese by adding a chlorine-based oxidant;
Co-existing in water characterized by performing back-washing operation on the filter material for iron removal and the filter material for manganese removal on which manganese is adhered, and separating and collecting the deposits on each filter medium Separating and recovering iron and manganese. Iron removal step of adsorbing iron by adjusting water containing iron, manganese and radium to pH 5.0-6.0, and contacting with the filter material for iron removal while oxidizing only air by air blowing,
A manganese removal step of adsorbing manganese and radium by adjusting the pH of water from which iron has been removed to near neutrality and contacting the filter material for manganese removal while oxidizing manganese by adding a chlorine-based oxidizing agent;
The filter media for removing iron with iron and the filter media for removing manganese with manganese and radium are back-washed with fresh water, and the deposits of each filter media are separated and recovered as a slurry. A method for separating and recovering iron and manganese coexisting in water. The filter medium according to claim 1 or 2, wherein a filter medium with iron oxyhydroxide coated on the particle surface is used as the filter medium for iron removal, and a filter medium with manganese oxide coated on the particle surface is used as the filter medium for manganese removal. Separation and recovery method of iron and manganese coexisting in water.

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