JP6444701B2 - Method and apparatus for purifying muddy water containing arsenic - Google Patents

Description

  The present invention relates to a purification method and a purification device for mud water containing arsenic.

  In particular, the present invention addresses the problem of naturally occurring arsenic, that is, arsenic originally contained in the ground due to natural causes, manifesting at the surface due to large-scale underground development such as shield excavation work. Is. Since this is a naturally derived pollution, the content standard of the Soil Contamination Countermeasures Law originally intended for surface layer pollution in urban areas such as chemical factories is sufficiently satisfied, but there are construction soils that exceed the elution standard several times. It is a ground environmental problem that occurs in large quantities.

  Until now, the following conventional technique 1 or conventional technique 2 has dealt with the soil containing natural arsenic generated in construction work in Japan. In both cases, the project could be carried out in the construction area without taking any special measures against hazardous metals.

<Prior art 1: Sea surface reclamation as construction soil>
"Ministerial Ordinance Establishing Judgment Criteria for Waste Containing Metals, etc. to be Released to Landfill Sites, etc. Specified in Article 5, Paragraph 1 of the Law Enforcement Ordinance on the Prevention of Marine Pollution and Marine Disasters" On the 17th General Order No. 6, final revision: Ministry of the Environment Ordinance No. 19 on May 30, 2014), the so-called “judgment standards related to bottom sediment” It is generally allowed up to 10 times the soil environment standard. Regarding arsenic, the soil elution amount standard is 0.01 mg / L, whereas the bottom sediment determination standard is 0.1 mg / L. Therefore, it is possible to clear the elution concentration of almost all naturally-derived arsenic-contaminated soil, and if there is a receiving destination for sea land reclamation, it was possible to carry out arsenic as it is without processing ( In the Tokyo metropolitan area, new sea surface disposal sites and Minamimotomaki Pier are examples.)

<Prior art 2: Dispose as sludge if the heavy metal elution amount standard is exceeded>
Based on the concentration control during construction or judgment in the pre-investigation, there was a method of transporting the generated soil exceeding the heavy metal elution standard to the designated contractor as construction sludge and converting it to cement raw material or disposal site.

  However, although the prior art 1 has a track record in a relatively large-scale business, the disposal location and the disposal capacity are tight, and the public works of the local government are prioritized. For conventional technology 2, the disposal capacity (acceptable amount) is also limited, and against the amount of naturally-derived contaminated soil expected to be generated from large-scale projects implemented in the Tokyo metropolitan area and Chukyo area in the future, This is an overwhelming situation.

  As a conventional technique, a method for treating arsenic using an adsorbent has also been reported. When adsorbents are used, groundwater, water from which solid content has been removed from mud water, and the like are targeted for treatment, and many methods of passing these contaminated water through columns filled with adsorbents are employed. For example, Patent Document 1 uses, as an adsorbent, an arsenic-trapping fiber in which iron is chelate-bonded to a chelate-forming fiber in which a functional group having a metal chelate-forming ability is introduced into a fiber molecule, and the adsorbent is filled. Disclosed is a method for passing arsenic-containing hot spring water through a container.

JP 2004-68182 A

  As described above, in the conventional arsenic treatment method using an adsorbent, in many cases, contaminated water that does not contain solid content is treated. Therefore, when processing muddy water containing arsenic, the muddy water is separated into solids and arsenic-containing water, and the arsenic-containing water is treated with the adsorbent. Thereby, arsenic containing water can be purified. However, since the arsenic-containing water remains in the separated solid content, it is necessary to wash the solid content multiple times, and the operation becomes complicated.

  The present invention has been made in view of the problems of the prior art, and an object thereof is to provide a method and apparatus for purifying muddy water containing arsenic by a simple operation.

  The inventors have directly injected the adsorbent into the mud containing arsenic, and again separated the mud from the adsorbent using the difference between the size of the solid particles in the mud and the size of the adsorbent. It was found that muddy water containing arsenic can be purified easily.

That is, the present invention includes the following.
[1] An adsorption process in which mud containing arsenic and an adsorbent larger than solid particles in the mud are mixed to adsorb arsenic on the adsorbent; and the mixture obtained in the adsorption process is classified by classification A separation step of separating into
A method for purifying muddy water containing arsenic.
[2] The purification method according to [1], wherein the adsorbent includes a base material and an adsorbing component supported on the base material, and the base material includes a fiber material.
[3] The purification method according to [2], wherein the base material contains cellulose fiber as a fiber material.
[4] The purification method according to [3], wherein the base material is a nonwoven fabric containing cellulose fibers.
[5] The adsorption component according to any one of [2] to [4], wherein the adsorption component includes at least one selected from the group consisting of iron hydroxide, aluminum hydroxide, iron oxide, and aluminum oxide. Purification method.
[6] If necessary, further includes a recovery step of recovering the adsorption ability of the adsorbent separated in the separation step with respect to arsenic,
The purification method according to any one of [1] to [5], wherein the adsorbent separated in the separation step or the adsorbent whose adsorptivity to arsenic has been recovered in the recovery step is reused in the adsorption step.
[7] A device for purifying muddy water containing arsenic,
Mixing tank containing arsenic and adsorbent larger than solid particles in mud, adsorbing arsenic to adsorbent; and separating the mixture obtained in the mixing tank into mud and adsorbent by classification Classifier to do;
A purification device comprising:
[8] The purification apparatus according to [7], further including a first return line for returning the adsorbent separated by the classifier to the mixing tank.
[9] A recovery device that recovers the arsenic adsorption ability of the adsorbent separated by the classifier as necessary; and a second return that returns the adsorbent that has recovered the arsenic adsorption ability in the recovery device to the mixing tank. line;
The purification device according to [7] or [8], further comprising:

  According to the present invention, mud containing arsenic can be purified by a simple operation.

An example of the purification procedure of contaminated mud water is shown. The outline of the purification device of a 1st embodiment is shown. The outline of the purification apparatus of 2nd Embodiment is shown. The outline of the purification apparatus of 3rd Embodiment is shown. The relationship between shaking time and arsenic concentration is shown. The amount of arsenic adsorption per unit weight of the adsorbent is shown.

<Method for purifying muddy water containing arsenic>
The present invention relates to a method for purifying muddy water containing arsenic (hereinafter also referred to as “contaminated muddy water”), including an adsorption step and a separation step. The purification method according to the present invention may further include an arsenic elution step. Moreover, the purification method according to the present invention may further include a recovery step. An example of the contaminated mud water purification procedure is shown in FIG. Hereinafter, each step will be described.

[1. Adsorption process]
The adsorption process is a process in which contaminated mud and adsorbent are mixed to adsorb arsenic to the adsorbent. Here, the adsorbent is larger than the solid particles in the muddy water. In this invention, the problem that arsenic containing water remains in the solid content isolate | separated from the muddy water can be solved by throwing the adsorbent directly into the contaminated muddy water.

  The contaminated muddy water in the present invention is not particularly limited as long as it contains arsenic, but in particular, surplus muddy water containing natural arsenic generated by muddy-type shield excavation work is targeted. In the muddy water shield excavation work, the muddy water after excavation is generally used for excavation after removing 74 μm or more of earth and sand by primary classification treatment, and surplus muddy water is generated. Therefore, the size of the solid particles in the excess mud is usually less than 74 μm. Since excess muddy water is continuously generated during muddy shield excavation work, it is preferable to purify the excess muddy water continuously.

  The management value of muddy water used for general muddy water type shield construction is about 1.4, and the specific gravity of surplus muddy water recovered after excavation and less than 74 μm is considered to be about 1.1 to 1.4.

  The adsorbent in the present invention preferably contains a base material and an adsorbing component supported on the base material.

  The substrate is not particularly limited as long as it is larger than the solid particles in the muddy water. Further, the shape of the substrate is not particularly limited. For example, base materials, such as cloth form, thread form, needle form, and powder form, can be mentioned.

  The size of the base material should be relatively determined by the size of the solid particles in the mud and the type of classifier used in the separation process described below. That is, a base material having a size that can be separated from solid particles in the muddy water by a classifier is used. However, as described above, since the size of the solid particles in the excess mud is usually less than 74 μm, the size of the base material is preferably 74 μm or more. As an example, the lower limit of the size of the substrate may be 100 μm, 200 μm, or the like. For example, the upper limit of the size of the base material may be 10 mm, 100 mm, or the like. An appropriate range of the substrate size can be set by appropriately combining these lower and upper limits.

  Here, the lower limit of the size of the substrate means the length at the shortest point in the shape of the substrate. Moreover, the upper limit of the magnitude | size of a base material means the length in the longest location in the shape of a base material.

  It is preferable that the base material contains a fiber material. Examples of the fiber material include plant fibers such as cotton, hemp and cellulose fibers; animal fibers such as hair and silk; chemical fibers such as rayon and acrylic. Although it does not specifically limit, it is preferable to use a cloth-like cellulose fiber as a base material, especially the nonwoven fabric of a cellulose fiber. Substrates containing such fiber materials are cheaper than conventional activated carbon substrates, are light in weight and easy to transport, and can be processed into any shape and size. Therefore, there are advantages such as easy separation by classification and a large amount of adsorbable component that can be supported.

  Examples of the adsorbing component include metal hydroxides, metal oxides, chelating agents, and ion exchange resins.

  Metal hydroxide and metal oxide include iron hydroxide, aluminum hydroxide, a combination of iron hydroxide and aluminum hydroxide, iron oxide, aluminum oxide, iron oxide and aluminum oxide, And a combination of iron hydroxide, aluminum hydroxide, iron oxide, and aluminum oxide (see, for example, Japanese Patent No. 4681384).

  Examples of the chelating agent include ethylenediaminetetraacetic acid (EDTA) and L-aspartic acid-N, N-diacetic acid (ASDA) (see Japanese Patent Application Laid-Open No. 2004-181303), and organic polymers having aminopolyol groups (special (See JP 2012-016667 A).

  Examples of the ion exchange resin include a hydroxide type weakly basic anion exchange resin (see JP-A-2005-351881).

  The adsorbent preferably settles in muddy water. For example, an adsorbent having a specific gravity of 0.85 to 2.85 is preferable. Alternatively, an adsorbent that contains water and has a specific gravity of 0.85 to 2.85 is preferable. Since the specific gravity of general sand is about 2.85, when the specific gravity of the adsorbent is within the above range, the adsorbent and the muddy water can be efficiently stirred.

  In the present invention, the adsorbent can be used repeatedly. Further, in the recovery step described below, the adsorptive capacity of the adsorbent for arsenic can be recovered. Therefore, a large amount of contaminated mud water can be purified by repeatedly using a small amount of adsorbent. For example, the adsorbent can be used in an amount of 5% by weight or less, more specifically 0.2 to 5% by weight, 1 to 3% by weight, or the like based on the weight of the contaminated mud water. By reducing the amount of adsorbent used, the material cost and the amount of secondary waste can be reduced.

  The mixing time of the adsorbent and the contaminated mud is appropriately changed depending on the nature of the soil, the concentration of arsenic, the amount of adsorbent used, etc., for example, 5-60 minutes, 10-50 minutes, 20-40 minutes, etc. be able to.

[2. Separation process]
The separation step is a step of separating the mixture obtained in the adsorption step into muddy water and an adsorbent by classification. The separation step utilizes the difference between the size of the solid particles in the muddy water and the size of the adsorbent. The separation step can be performed using a classifier. The classifier is not particularly limited as long as it can separate solid particles and adsorbent in muddy water. For example, a classifier that allows solid particles in the muddy water to pass but does not allow the adsorbent to pass through. More specifically, a classifier including a sieve having an opening larger than the solid particles in the muddy water and smaller than the adsorbent. Can be mentioned. By using such a classifier, the adsorbent can be easily separated from the muddy water.

  The adsorbent separated in the separation step can be reused in the adsorption step. By reusing the adsorbent, the amount of adsorbent used is reduced, and the material cost and the amount of secondary waste can be reduced. It is also possible to reuse muddy water from which arsenic has been removed.

  In the separation step, bubbles may be introduced into the mixture. In particular, when a material containing a fiber material is used as the base material of the adsorbent, the adsorbent can be floated in the mixture by introducing bubbles. Thereby, it becomes possible to separate muddy water and the adsorbent more easily.

[3. Arsenic elution process]
The arsenic elution step is a step of eluting arsenic contained in the solid content of the contaminated mud water into the water before or simultaneously with the adsorption step as necessary. The arsenic content in the muddy water can be further reduced by adsorbing arsenic with an adsorbent after positively eluting arsenic contained in the solid content.

  The arsenic elution step can be carried out by treating the contaminated mud with acid or alkali. Specifically, acid or alkali may be added to the contaminated mud and stirred. The stirring time can be, for example, 5 to 30 minutes.

  Examples of the acid include sulfuric acid, phosphoric acid, and oxalic acid. Examples of the alkali include sodium hydroxide and potassium hydroxide.

[4. Recovery process]
The recovery step is a step of recovering the adsorption ability of the adsorbent separated in the separation step with respect to arsenic as necessary. The recovery step can be performed, for example, by treating the adsorbent with an alkali.

  Usually, the adsorbent separated in the separation step is reused in the adsorption step as it is, but arsenic is adsorbed to the adsorbent to the limit by repeating the reuse. As a result, the adsorbent cannot adsorb arsenic. In this case, when a new adsorbent is used, the amount of adsorbent used increases, and the material cost and the amount of secondary waste increase. Here, if necessary, the use of a new adsorbent can be avoided by restoring the adsorption capacity of the used adsorbent to arsenic.

  In the arsenic elution step and recovery step of the present invention, “as necessary” means that a person who implements the present invention determines as appropriate. That is, the presence or absence of the arsenic elution step and the recovery step and the timing of the execution can be appropriately determined by the person who implements the present invention from the cost-effectiveness and the like. Therefore, it is not always necessary that arsenic is adsorbed to the adsorbent before the recovery step.

  For example, the arsenic concentration of contaminated mud water is investigated, the number of reuses of the adsorbent that is assumed to be able to sufficiently adsorb arsenic is set in advance, and the recovery process is performed after the number of reuses. May be. Alternatively, arsenic may be adsorbed by an adsorbent, the arsenic concentration of muddy water may be measured, and the recovery step may be performed when it is determined that the arsenic concentration has not sufficiently decreased.

  The recovery step can be performed, for example, by treating the adsorbent with an alkali. Examples of the alkali include sodium hydroxide, potassium hydroxide, calcium hydroxide, and alkaline waste liquid of concrete.

  The alkali is used at a concentration of 0.1 to 10 mol / L, for example. By performing the recovery process at such a concentration, it is possible to prevent the adsorbent from deteriorating.

  As a method of treating the adsorbent with alkali, it is not necessary to use a special method, and the adsorbent and the alkali may be brought into contact with each other. For example, a method of immersing the adsorbent in an alkali can be used. What is necessary is just to set immersion time in consideration of the quantity of an adsorbent, the density | concentration of an alkali, and the quantity of an alkaline solution, for example, can be 15-30 minutes, 60-120 minutes, etc.

  Two groups of adsorbents may be prepared, and the other group of adsorbents may be used in the adsorption process while the recovery process is being performed on one group of adsorbents. Thereby, it can prevent that purification | cleaning of contaminated mud water is interrupted in the case of a recovery process.

  As described above, the purification method according to the present invention includes an adsorption step and a separation step, and preferably further includes an arsenic elution step and / or a recovery step. Note that the steps included in the purification method according to the present invention are not limited to those described above, and may include additional steps as necessary. For example, a solid-liquid separation step of solid-liquid separation of muddy water from which the adsorbent has been separated in the separation step may be included. In the present invention, since the adsorbent is directly put into the contaminated mud, the problem that the arsenic-containing water remains in the solid content separated by the solid-liquid separation process can be solved. Thereby, both the separated solid content and water can be reused, and the disposal costs can be reduced.

<Purification device for muddy water containing arsenic>
A purification apparatus according to the present invention for carrying out the above purification method will be described below with reference to the drawings. However, the following embodiment is only an example, and the embodiment of the purification apparatus according to the present invention is not limited thereto. In the range which does not deviate from the meaning of this invention, the apparatus which consists of a further structure is included by this invention. In addition, the overlapping part is abbreviate | omitted suitably in description of each following embodiment.

[First Embodiment]
The 1st Embodiment of this invention is related with the purification apparatus provided with the mixing tank 101 and the classifier 102, as shown in FIG.

  The mixing tank 101 mixes contaminated mud and an adsorbent larger than solid particles in the contaminated mud to adsorb arsenic on the adsorbent. The mixing tank 101 has a stirrer 103 that mixes the contaminated mud water and the adsorbent, and includes a mixture delivery line 104 that delivers the mixture obtained by mixing to the classifier 102.

  The classifier 102 separates the mixture obtained in the mixing tank 101 into muddy water and an adsorbent by classification. In the lower part of the classifier 102, a purified muddy water storage container 105 for storing the purified muddy water is disposed. The purification device may include a solid-liquid separation device (not shown) for solid-liquid separation of the purified muddy water stored in the purified muddy water storage container 105. Further, the purification device may include a bubble introduction device (not shown) that introduces bubbles into the classifier 102.

  The classifier is not particularly limited as long as it can separate solid particles and adsorbent in muddy water. For example, a classifier that allows solid particles in the muddy water to pass but does not allow the adsorbent to pass through. More specifically, a classifier including a sieve having an opening larger than the solid particles in the muddy water and smaller than the adsorbent. Can be mentioned.

  In the purification apparatus according to the first embodiment configured as described above, the contaminated mud water and the adsorbent are mixed in the mixing tank 101, and arsenic is adsorbed by the adsorbent in the mixture. The mixture is sent to the classifier 102 via the mixture delivery line 104 and separated into muddy water and adsorbent by classification. The purified muddy water from which the adsorbent is separated is stored in the purified muddy water storage container 105.

  According to the purification apparatus of the first embodiment, contaminated mud water can be purified by a simple operation.

[Second Embodiment]
The 2nd Embodiment of this invention is related with the purification apparatus provided with the mixing tank 201, the classifier 202, and the 1st return line 206, as shown in FIG.

  The second embodiment is different from the first embodiment in that a first return line 206 is provided.

  The first return line 206 returns the adsorbent separated by the classifier 202 to the mixing tank 201.

  In the purification apparatus of the second embodiment configured as described above, the adsorbent separated by the classifier 202 is returned to the mixing tank 201 via the first return line 206.

  According to the purification device of the second embodiment, the contaminated mud can be purified by a simple operation. Moreover, according to the purification apparatus of 2nd Embodiment, material cost and the amount of secondary waste can be reduced by reusing an adsorbent.

[Third Embodiment]
As shown in FIG. 4, the third embodiment of the present invention relates to a purification apparatus including a mixing tank 301, a classifier 302, a first return line 306, a recovery device 307, and a second return line 309.

  The third embodiment is different from the second embodiment in that a recovery device 307 and a second return line 309 are provided.

  The recovery device 307 recovers the arsenic adsorption ability of the adsorbent separated by the classifier 302 as necessary. The recovery device 307 includes a recovery adsorbent delivery line 310 that delivers the adsorbent whose adsorption capacity has been recovered to the filter 308.

  The filter 308 collects the adsorbent whose adsorption capacity has been recovered by the recovery device 307. An arsenic-containing solution storage container 311 that stores a solution containing arsenic removed from the adsorbent is disposed below the filter 308. Since the arsenic-containing solution can be used multiple times in the recovery device 307, the purification device may include a line (not shown) for returning the solution from the arsenic-containing solution storage container 311 to the recovery device 307.

  The second return line 309 returns the adsorbent recovered by the filter 308 and recovered to the mixing tank 301.

  Examples of the recovery device include a container containing an alkali for recovering the adsorption capacity of the adsorbent.

  In the purification device of the third embodiment configured as described above, the adsorbent separated by the classifier 302 is sent to the recovery device 307 as needed to recover the adsorption capacity. The adsorbent whose adsorptive capacity has been recovered is returned to the mixing tank 301 via the second return line 309.

  According to the purification apparatus of the third embodiment, the contaminated mud can be purified by a simple operation. In addition, according to the purification device of the third embodiment, the material cost and the amount of secondary waste can be further reduced by reusing the adsorbent while recovering the adsorption ability for arsenic as necessary.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, the technical scope of this invention is not limited to this.

<Adsorbent>
Adsorbent 1: Adsorbent (MP-C: manufactured by Astec Co., Ltd.) in which iron oxide and aluminum oxide are supported on activated carbon.
Adsorbent 2: Adsorbent in which iron oxide and aluminum oxide are supported on cellulose fibers (nonwoven fabric: width 5 mm × length 20 mm).
Adsorbent 3: An adsorbent in which a chelating agent is supported on cellulose fibers (fine needles).

<Analysis method>
Rapid analysis: Merckant's arsenic ultrasensitive analysis set Official method analysis: Conforms to Environmental Agency Notification No. 55 (JISK0102.61.2)

<Reference Example 1: Examination of shaking time in water containing arsenic>
Disodium hydrogen arsenate heptahydrate was dissolved in distilled water to prepare simulated contaminated water having an arsenic concentration of 0.2 mg-As (V) / L. Adsorbent 1 or 2 (0.5 g) was added to simulated contaminated water (200 mL), and the relationship between shaking time and arsenic concentration was tested. The liquid after shaking was filtered through a 0.45 μm membrane filter, and the arsenic concentration of the filtrate was analyzed. The results are shown in Table 1 and FIG.

N.D.:定量下限値0.005mg/L未満

ND: Lower limit of quantification less than 0.005mg / L

  The adsorbent 2 was able to adsorb arsenic more quickly than the adsorbent 1. This is presumed to be due to the good contact between the adsorbent 2 and the simulated contaminated water and the large amount of adsorbed component supported on the adsorbent.

  Further, the adsorbent 2 had sufficient strength to withstand shaking for a short time (60 minutes). Further, although the adsorbent 2 slightly loosened the fibers by shaking for a long time (1440 minutes), it could be easily separated by filtration.

<Reference Example 2: Examination of reuse of adsorbent in arsenic-containing water>
Adsorbent 2 (0.5 g) was added to the simulated contaminated water (200 mL) prepared in Reference Example 1, and shaken for 30 minutes. The liquid after shaking was filtered through a 0.45 μm membrane filter, and the arsenic concentration of the filtrate was analyzed. The adsorbent collected by filtration was added to new simulated contaminated water, and the same operation was repeated until the arsenic concentration of the filtrate was 2 mg / L by rapid analysis. The results are shown in Table 2 and FIG.

N.D.:定量下限値0.005mg/L未満

ND: Lower limit of quantification less than 0.005mg / L

  From the result of the official method analysis, the amount of arsenic adsorption per unit weight of the adsorbent was calculated (FIG. 6). Even after 25 repeated uses, it was possible to recover the adsorbent 2 with a 75 μm sieve.

<Reference Example 3: Confirmation of Arsenic Adsorption Amount in Arsenic-Containing Water>
The column was packed with adsorbent 2 or 3. Simulated contaminated water containing arsenic was continuously passed through the column in the downward flow direction. The change in arsenic concentration over time was measured at the outlet of the column to confirm the amount of arsenic adsorption. The results are shown in Table 3.

  Adsorbents 2 and 3 were confirmed to have arsenic adsorption ability in simulated contaminated water. In particular, it was confirmed that the adsorbent 3 has a very excellent arsenic adsorption ability in simulated contaminated water.

<Example 1: Purification test of arsenic-containing mud water>
Tap water was added to natural heavy metal actual contaminated soil and stirred to create a suspension. The suspension was passed through a 2 mm sieve to collect coarse particles, and then passed through a 75 μm sieve. The obtained muddy water was used as raw muddy water.

Adsorbent 2 or 3 (22.2 g: equivalent to 5% by weight of raw mud water) was added to the raw mud water (444 g) and stirred for 15 minutes. The muddy water and the adsorbent were separated using a sieve having an opening of 75 μm, and the muddy water was allowed to stand for 10 to 30 minutes. The muddy water was centrifuged at 3000 rpm for 20 minutes and filtered through a 0.45 μm membrane filter. The arsenic concentration of the filtrate was analyzed.
Table 4 shows the properties of the raw mud water and the treatment results with the adsorbent 2 or 3.

<Example 2: Arsenic adsorption test in arsenic-containing mud>
The adsorbent 2 or 3 collected in Example 1 was washed with tap water and dehydrated. 100 mL of 1 mol / L NaOH solution was added to the adsorbent and stirred for 15 minutes. The above step (NaOH addition / stirring) was repeated 3 times, and the resulting solution was mixed well. The arsenic concentration of the solution was analyzed. The results are shown in Table 5.

  From the results of Examples 1 and 2, it was confirmed that the adsorbents 2 and 3 have arsenic adsorption ability even in the muddy water, can purify the contaminated muddy water, and can be easily separated from the muddy water by classification. In particular, it was confirmed that the adsorbent 2 has a very excellent arsenic adsorption ability in muddy water. In the case of targeting muddy water, unlike the case of targeting arsenic-containing water (Reference Example 3), the adsorbent 2 had an arsenic adsorption ability superior to that of the adsorbent 3.

  Further, from the results of Example 2, it was confirmed that arsenic adsorbed on the adsorbent could be removed. Thereby, the adsorption ability with respect to the arsenic of the adsorbent is recovered, and the adsorbent can be reused.

<Example 3: Removal test of soil adhering to adsorbent>
Soil (100 g) and distilled water (32.20 g) were mixed to create muddy water (specific gravity 1.4). Under the following conditions 1 to 4, the amount of soil adhering to the adsorbent 2 was measured. The results are shown in Table 6.

Condition 1: After adsorbent 2 was mixed with muddy water, adsorbent 2 was recovered and dried.
Condition 2: After adsorbent 2 was mixed with muddy water, adsorbent 2 was recovered, washed with a small amount of water, and dried.
Condition 3: After adsorbent 2 was mixed with muddy water, adsorbent 2 was recovered, treated with a 0.85 mm sieve, and dried.
Condition 4: After adsorbent 2 was mixed with muddy water, adsorbent 2 was recovered, treated with a 0.85 mm sieve, washed with a small amount of water, and dried.

  From the results of conditions 2 and 4, it was confirmed that the soil adhering to the adsorbent 2 can be easily removed by washing with a small amount of water. It was also confirmed that the strength of the adsorbent after the soil was removed was maintained.

101, 201, 301 ... Mixing tank 102, 202, 302 ... Classifier 103, 203, 303 ... Stirrer 104, 204, 304 ... Mixing line 105, 205, 305 ... Purified mud storage container 206, 306 ··· First return line 307 · · Recovery device 308 · · Filter 309 · · Second return line 310 · · Recovery adsorbent delivery line 311 · · Arsenic-containing solution container

Claims (4)

An adsorption process in which mud containing arsenic and adsorbent larger than solid particles in the mud are mixed to adsorb arsenic on the adsorbent; and the mixture obtained in the adsorption process is separated into mud and adsorbent by classification Separating step to perform;
A method for purifying muddy water containing arsenic ,
The adsorbent includes a base material and an adsorbing component supported on the base material,
The base material is a nonwoven fabric containing cellulose fibers,
The adsorbing component comprises at least one selected from the group consisting of iron hydroxide, aluminum hydroxide, iron oxide, and aluminum oxide,
Purification method. The purification method according to claim 1, wherein the substrate has a size of 100 μm to 100 mm. The purification method according to claim 1 or 2, wherein the amount of the adsorbent is 5% by weight or less based on the weight of the muddy water. If necessary, it further includes a recovery step for recovering the adsorption ability of the adsorbent separated in the separation step to arsenic,
Adsorbent separated in the separation step, or to reuse the adsorbent adsorbing capacity for arsenic is recovered in the adsorption step in the recovery process, the purification method according to any one of claims 1-3.

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