JP2015193001A - Arsenic adsorption device and arsenic adsorption method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arsenic adsorption device and an arsenic adsorption method capable of adsorbing away arsenic in the liquid to be treated efficiently and also at a high degree using a cation exchange resin.SOLUTION: When the liquid to be treated is contacted with an arsenic absorbent, and arsenic in the liquid to be treated is removed away into the arsenic adsorbent, as the arsenic adsorbent, a cation exchange resin with an Fe ion as a counter ion is used. Preferably, the liquid to be treated is contacted with the cation exchange resin in which a Ca ion is used as a counter ions, and thereafter, the same is contacted with the cation exchange resin in which an Fe ion is used as a counter ions and is next contacted with a cation exchange resin in which an Na ion is used as a counter ion.

Description

  The present invention relates to an arsenic adsorption device and an arsenic adsorption method for efficiently adsorbing and removing arsenic in a liquid to be treated.

  Arsenic and arsenic compounds are contained in pyrite, phosphorus ore, etc., and there is a possibility that a large amount of arsenic is contained in wastewater from phosphorus, phosphorus compound manufacturing plants, sulfuric acid manufacturing plants, etc. that use these as raw materials. In addition, since arsenic is used as a semiconductor raw material, there is a possibility that a large amount of arsenic is also contained in wastewater from semiconductor manufacturing / processing plants. Furthermore, arsenic may be contained in mine wastewater and hot spring water.

  Arsenic is a highly toxic environmental pollutant. For example, when arsenic is contained in groundwater, arsenic may be concentrated in agricultural products, or arsenic may be concentrated in fishery products such as fish, which may adversely affect human bodies. For this reason, there are strict regulations on arsenic in wastewater.

  As a method for recovering arsenic contained in wastewater, etc., a coprecipitation collection method in which arsenic is precipitated together with hydroxides of metals such as iron, aluminum, calcium, magnesium, etc. A method of adsorbing and recovering arsenic by adding an arsenic adsorbent supported on a molecular porous carrier (Patent Document 1) or an arsenic adsorbent consisting of a phenol resin and a metal hydroxide (Patent Document 2), an anion exchange resin A method of using and adsorbing is known.

However, in the coprecipitation collection method and the method using the arsenic adsorbent described in Patent Document 1 or Patent Document 2, in order to reduce arsenic to a wastewater standard value of 0.1 mg / L or less, a large amount of metal Hydroxides and adsorbents must be added, and there is a problem in that post-treatment of the large amount of sludge to be generated is not easy.
In addition, the method of using a rare earth element hydrous oxide as an adsorbent is because the rare earth element used as a raw material for the adsorbent is expensive and the adsorbent is small in particle size. When used, there is a problem that pressure loss becomes large and practicability is poor. Further, the ion exchange method using an anion exchange resin has a problem that the arsenic adsorption effect is remarkably reduced if a coexisting salt is present.

  Patent Document 3 proposes an arsenic adsorption resin in which iron and hydroxyl ions are supported on a cation exchange resin and / or a chelate resin to solve such problems. It is described that the resin is excellent in the ability to recover arsenic from an arsenic-containing solution, and that such a resin can be produced inexpensively and easily and can be adsorbed and recovered effectively.

JP-A 61-187931 JP 59-69151 JP-A-9-225298

  In Patent Document 3, there is a description that a cation exchange resin is used as a base resin of an arsenic adsorption resin. However, in Examples of Patent Document 3, a chelate resin is used. That is, Patent Document 3 discloses an example in which iron is supported on a chelate resin and then alkali-treated with sodium hydroxide or the like, and iron is supported as iron hydroxide. Actually, a cation exchange resin was used. There is no example, and the arsenic adsorption ability of the cation exchange resin supporting iron and hydroxyl ions is not clarified. In addition, an arsenic adsorption device and an arsenic adsorption method for effectively adsorbing and removing arsenic in the liquid to be treated have not been studied.

  The present invention has been made in view of the above-described conventional situation, and uses cation exchange resin that is cheaper and more versatile than chelate resin to efficiently and highly remove arsenic in the liquid to be treated. An object of the present invention is to provide an arsenic adsorption device and an arsenic adsorption method that can be performed.

  As a result of repeated studies to solve the above problems, the present inventors have found that a cation exchange resin using Fe ions as a counter ion can efficiently adsorb and remove arsenic in the liquid to be treated.

  That is, the gist of the present invention is as follows.

[1] An arsenic adsorbing device comprising an arsenic adsorbent that comes into contact with a liquid to be treated and adsorbs arsenic in the liquid to be treated, the cation exchange resin using Fe ions as the arsenic adsorbent as a counter ion; A cation exchange resin with a Ca ion as a counter ion, and before the liquid to be treated comes into contact with a cation exchange resin with a Fe ion as a counter ion, the cation exchange resin with a Ca ion as a counter ion An arsenic adsorption device characterized by having a structure to be used.

[2] The arsenic adsorption apparatus according to [1], wherein the cation exchange resin using the Fe ion as a counter ion is a gel type.

[3] The arsenic adsorption apparatus according to [1] or [2], wherein an average particle size of the cation exchange resin using Fe ions as a counter ion is 800 μm or less.

[4] The arsenic adsorption apparatus according to any one of [1] to [3], wherein a uniformity coefficient of a particle size of the cation exchange resin using Fe ions as a counter ion is 1.2 or less.

[5] An arsenic adsorption method in which a liquid to be treated is brought into contact with an arsenic adsorbent and arsenic in the liquid to be treated is adsorbed to the arsenic adsorbent, wherein Fe ions as the arsenic adsorbent are used as counter ions. Using a cation exchange resin and a cation exchange resin having a Ca ion as a counter ion, and before contacting the liquid to be treated with a cation exchange resin having a Fe ion as a counter ion, the Ca ion is changed to a counter ion. A method of adsorbing arsenic, comprising contacting with a cation exchange resin prepared.

[6] The arsenic adsorption method according to [5], wherein the cation exchange resin using the Fe ion as a counter ion is a gel type.

[7] The arsenic adsorption method according to [5] or [6], wherein an average particle size of the cation exchange resin using the Fe ion as a counter ion is 800 μm or less.

[8] The arsenic adsorption method according to any one of [5] to [7], wherein a uniformity coefficient of a particle size of the cation exchange resin using Fe ions as a counter ion is 1.2 or less.

[9] The arsenic adsorption method according to any one of [5] to [8], wherein the liquid to be treated has a pH of 2 to 4.

[10] A method of passing the liquid to be treated through a packed bed of a cation exchange resin using the Fe ions as counter ions, wherein the liquid SV of the liquid to be treated is ¹ to 200 hr ^−1. The arsenic adsorption method according to any one of [5] to [9].

  According to the present invention, by using a cation exchange resin with Fe ions as counter ions, arsenic in the liquid to be treated can be efficiently adsorbed and removed, and high-quality treated water from which arsenic is highly removed is obtained. be able to.

10 is a graph showing a breakthrough curve of As (V) obtained in Reference Example 9. It is a graph which shows the metal concentration of the treated water of the comparative example 4.

  Hereinafter, embodiments of the present invention will be described in detail.

The arsenic adsorption apparatus and the arsenic adsorption method of the present invention may be referred to as a cation exchange resin (hereinafter referred to as “Fe-supported cation exchange resin”) using Fe ions as counter ions as an arsenic adsorbent that adsorbs arsenic in a liquid to be treated. And a cation exchange resin using Ca ions as a counter ion (hereinafter sometimes referred to as “Ca-supported cation exchange resin”), and the liquid to be treated is brought into contact with the Ca-supported cation exchange resin. And contacting with an Fe-supporting cation exchange resin.
The Fe-supported cation exchange resin has excellent arsenic adsorption performance and can efficiently adsorb and remove arsenic in the liquid to be treated.

  In the present invention, for the following reasons, together with an Fe-supported cation exchange resin as an arsenic adsorbent, a Ca-supported cation exchange resin, and further, a cation exchange resin using Na ions as a counter ion (hereinafter referred to as “Na-supported cation exchange resin”). Is sometimes used in combination.).

That is, the Fe-supported cation exchange resin can efficiently adsorb and capture arsenic ions, but when the amount of arsenic adsorption increases, Fe ions tend to leak from the Fe-supported cation exchange resin. Therefore, in order to capture Fe ions leaked from the Fe-supported cation exchange resin, a cation exchange resin (ordinary cation exchange resin. That is, a cation exchange resin having a Na ion having a lower selectivity than Fe ions as a counter ion) In general, it is commercially available as Na form carrying Na ions.) Is mixed with the Fe-supported cation exchange resin or provided downstream of the Fe-supported cation exchange resin, and the Fe ions leaked from the Fe-supported cation exchange resin. Is preferably adsorbed and captured by Na-supported cation exchange resin.
In particular, when the electrolyte concentration (ionic strength) of the liquid to be treated is high, Fe ions easily leak out from the Fe-supported cation exchange resin. Therefore, the Na-supported cation exchange resin is used together, and the amount of Na-supported cation exchange resin used together It is preferable to increase the number.

  Further, in the Fe-supported cation exchange resin as an arsenic adsorbent, phosphate ions act as interfering ions in the presence of phosphate ions, and the ability to adsorb and trap arsenic ions is reduced. Therefore, when phosphate ions coexist in the liquid to be treated, a Ca-supported cation exchange resin is used in combination, and a Ca-supported cation exchange resin is provided on the upstream side of the Fe-supported cation exchange resin. It is preferable to perform adsorption treatment of arsenic ions with Fe-supported cation exchange resin after capturing and removing acid ions with Ca-supported cation exchange resin.

[Cation exchange resin]
Characteristics of Cation Exchange Resin Suitable as Fe-Supported Cation Exchange Resin Used in the Present Invention, and Cation Exchange Resin that Becomes Resin Base of Ca-Supported Cation Exchange Resin (hereinafter referred to as “Cation Exchange Resin of the Present Invention”) The physical properties are as follows. As will be described later, the cation exchange resin of the present invention is a Na-type cation exchange resin and corresponds to a Na-supported cation exchange resin.

<Chemical structure and form>
The cation exchange resin of the present invention preferably has a crosslinked structure skeleton obtained by copolymerization of a monovinyl aromatic monomer and a crosslinkable aromatic monomer from the viewpoint of durability and rationality of the production method. Here, examples of the monovinyl aromatic monomer include alkyl-substituted styrenes such as styrene, methylstyrene, and ethylstyrene, and halogen-substituted styrenes such as bromostyrene. Among these, styrene or a monomer mainly composed of styrene is preferable.

Moreover, as a crosslinkable aromatic monomer, divinylbenzene, trivinylbenzene, divinyltoluene, divinylnaphthalene, divinylxylene, etc. are mentioned. Of these, divinylbenzene is preferred.
Industrially produced divinylbenzene usually contains a large amount of by-product ethyl vinyl benzene (ethyl styrene). In the present invention, such divinyl benzene is purified in advance and contains such impurities. It is preferable to use after reducing the amount.

  Specific examples of the cation exchange resin of the present invention include a styrene-divinylbenzene copolymer.

  The main forms of the cation exchange resin of the present invention include a gel type and a porous type, but a gel type is preferable from the viewpoint of exchange capacity and cost. In addition, a porous type (a porous type, a high porous type, or a macroporous type) is also preferable from the viewpoint of ensuring material diffusibility, resin durability, and strength.

  Further, the cation exchange resin of the present invention is usually in a particle shape (granular). Specific shapes include various shapes such as a spherical shape, a substantially spherical shape, a polyhedral shape, and an aggregate shape, but are not particularly limited.

<Average particle size>
The cation exchange resin of the present invention preferably has an average particle size (weight average particle size) of 800 μm or less. In particular, the cation exchange resin preferably has an average particle size of 500 μm or less, 3 μm or more, particularly 5 μm or more. Preferably there is.

  If the average particle size of the cation exchange resin is too large, the reaction activity and reaction rate are low and the adsorption performance of arsenic ions and the like tends to be low. If it is too small, the liquid to be treated in the reactor filled with the cation exchange resin When the liquid is passed, the pressure loss tends to increase. When the reaction is performed in a suspended state, the operability may be deteriorated, for example, the filterability is deteriorated. By using a cation exchange resin having an average particle size in the above range, it is possible to improve high adsorption performance and processing efficiency.

  In addition, although the average particle diameter of a cation exchange resin is normally measured with a microscope picture and a particle size distribution measuring apparatus, a catalog value is employable about a commercial item.

<Uniformity coefficient>
The cation exchange resin of the present invention preferably has a sharp particle size distribution, and the uniformity coefficient is usually 1.2 or less, particularly 1.1 or less, particularly 1.05 or less. A uniformity coefficient of 1.2 or less is preferable in that the reaction activity and reaction rate are improved, and the pressure loss during the flow of the liquid to be treated to the reactor filled with the cation exchange resin is alleviated. A smaller uniformity coefficient is desirable, but if it is too large, the reaction activity and reaction rate tend to decrease. The lower limit of the uniformity coefficient is 1.0. By using a cation exchange resin having a uniformity coefficient in the above range, it is possible to improve high adsorption performance and processing efficiency.

  The uniformity coefficient of the cation exchange resin is usually measured and calculated by a particle size distribution analyzer, but catalog values can be adopted for commercially available products.

<Degree of crosslinking>
The degree of crosslinking of the cation exchange resin of the present invention is preferably 25% or less, more preferably 15% or less, further preferably 10% or less, more preferably 1% or more, and further preferably 2% or more. The term “crosslinking degree” as used herein refers to the concentration of the crosslinkable monomer in the polymerizable monomer to be subjected to polymerization, and is the same as the definition used in this field.

  If the degree of crosslinking is too large, the adsorption performance tends to decrease due to diffusion resistance in the cation exchange resin, and if it is too small, it becomes difficult to maintain the strength of the cation exchange resin, and further, the treatment is reduced. Therefore, the cation exchange resin is crushed and the like due to swelling and shrinkage during handling such as adsorption treatment, which is not preferable.

<Amount of sulfonic acid group>
The cation exchange resin of the present invention preferably contains 3.0 milliequivalents or more of sulfonic acid groups per gram of resin.
In particular, the cation exchange resin of the present invention is preferably a sulfonic acid type strongly acidic cation exchange resin. In this case, the cation exchange resin corresponds to the neutral salt decomposition capacity of the sulfonic acid group per 1 g of the dry resin based on the Na form. The exchange capacity is usually 3 meq / g-resin or more, preferably 4.0 meq / g-resin or more, more preferably 4.5 meq / g-resin or more, and usually 6.0 meq / g-resin or less. preferable.

[Fe-supported cation exchange resin]
The Fe-supported cation exchange resin used in the present invention is obtained by supporting Fe ions on the cation exchange resin of the present invention as described above. As the cation exchange resin used for supporting Fe ions, commercially available products having the above-mentioned suitable characteristics or physical properties can be used.

  There is no restriction | limiting in particular as the support method of Fe ion to a cation exchange resin, According to a conventional method, it can carry out.

  Examples of iron compounds used for Fe support include ferrous oxide, ferrous hydroxide, ferrous sulfide, ferrous fluoride, ferrous chloride, ferrous bromide, ferrous iodide, nitric acid Ferrous sulfate, ferrous sulfate, ferrous carbonate, ferric oxide, ferric fluoride, ferric chloride, ferric bromide, ferric nitrate, ferric sulfate, etc. Two or more kinds can be used. Of these, ferric chloride, ferric sulfate, ferric nitrate, ferrous chloride, ferrous sulfate, and ferrous nitrate are preferred.

Usually, by treatment with an aqueous solution containing the above iron compound, that is, for example, by adding a cation exchange resin to the iron compound aqueous solution and stirring and mixing, or in a column packed with the cation exchange resin, the aqueous iron compound solution By passing the solution, Fe ions can be supported on the cation exchange resin.
By treating the cation exchange resin with such an aqueous solution of an iron compound, Fe ions having a higher selectivity than Na ions of a commercially available Na-type cation exchange resin are easily replaced with Na ions. An exchange resin can be obtained.

  In this Fe carrying treatment, after carrying Fe, a mineral acid such as nitric acid, hydrochloric acid, sulfuric acid or the like is added to maintain strong acidity, and an alkali such as potassium hydroxide or sodium hydroxide is added to adjust the pH of the treatment liquid. By adjusting the value to 2 or less, a large amount of Fe ions can be supported without precipitation.

The amount of Fe supported on the Fe-supported cation exchange resin thus obtained is preferably about 0.5 to 2.5 meq / g-resin, particularly about 1.0 to 2.5 eq / g-resin. If the Fe loading is too small, sufficient arsenic adsorption ability cannot be obtained.
In addition, you may perform processes, such as a grinding | pulverization and a classification, in order to adjust the average particle diameter and uniformity coefficient of a cation exchange resin after the said Fe carrying process.

[Na-supported cation exchange resin]
As described above, since the commercially available cation exchange resin is usually a Na-type cation exchange resin, the average particle size and uniformity coefficient are adjusted as it is or as needed as the Na-supported cation exchange resin. In order to achieve this, it can be used after being subjected to processing such as pulverization and classification.

[Ca-supported cation exchange resin]
The Ca-supported cation exchange resin used in the present invention is obtained by supporting Ca ions on the cation exchange resin of the present invention as described above. As the cation exchange resin used for supporting Ca ions, commercially available products having the above-mentioned suitable characteristics or physical properties can be used.
There is no restriction | limiting in particular as a support method of Ca ion to a cation exchange resin, According to a conventional method, it can carry out.

As a calcium compound used for Ca carrying | support, 1 type (s) or 2 or more types, such as calcium hydroxide, calcium chloride, calcium nitrate, can be used, for example.
Of these, calcium chloride is preferred.

Usually, by treatment with an aqueous solution containing the above calcium compound, that is, for example, by adding a cation exchange resin to the calcium compound aqueous solution and stirring and mixing, or in a column packed with the cation exchange resin, the aqueous calcium compound solution By passing the solution, Ca ions can be supported on the cation exchange resin.
By treating the cation exchange resin with such an aqueous solution of a calcium compound, Ca ions having a higher selectivity than Na ions of a commercially available Na-type cation exchange resin are easily replaced with Na ions. An exchange resin can be obtained.

  In this Ca supporting treatment, after supporting Ca, a mineral acid such as nitric acid, hydrochloric acid, sulfuric acid, etc. is added to keep it below weak alkalinity, and an alkali such as potassium hydroxide, sodium hydroxide is added. By adjusting the pH to 2 to 4, a large amount of Ca ions can be supported without precipitation.

The amount of Ca supported on the Ca-supported cation exchange resin thus obtained is preferably about 0.5 to 2.5 meq / g-resin, particularly about 1.0 to 2.5 meq / g-resin. If the amount of Ca supported is too small, sufficient phosphate ion adsorption ability cannot be obtained.
In addition, you may perform processes, such as a grinding | pulverization and classification, in order to adjust the average particle diameter and uniformity coefficient of a cation exchange resin after the said Ca carrying | support process.

[Processed liquid]
The liquid to be treated for arsenic adsorption treatment in the present invention is water containing arsenic ions, for example, waste water from a manufacturing plant of phosphorus or a phosphorus compound using the above-mentioned pyrite or phosphorus ore as a raw material, a sulfuric acid manufacturing plant, Examples include, but are not limited to, wastewater from semiconductor manufacturing and processing factories, mine wastewater, and hot spring water.
The arsenic concentration of such arsenic-containing water is not particularly limited, but is usually about 1 μg / L to 100 mg / L. By treating such a liquid to be treated according to the present invention, the arsenic concentration is determined based on wastewater standards. It is necessary to treat the value to 0.1 mg / L or less, preferably 0.01 mg / L or less.

Moreover, in this invention, the to-be-processed liquid containing an arsenic and a phosphate ion can also be processed suitably by using together Ca carrying | support cation exchange resin with Fe carrying | support cation exchange resin. Examples of liquids containing arsenic and phosphate ions include semiconductor wastewater, groundwater, river / lake water, etc., and the phosphate ion concentration is usually about 0.5 to 500 mg / L in terms of PO ₄ -P. is there.

[Arsenic adsorption treatment with Fe-supported cation exchange resin]
The method of adsorbing and removing the arsenic in the liquid to be treated by treating the liquid to be treated with the Fe-supported cation exchange resin is a batch processing method in which the Fe-supported cation exchange resin is added to the liquid to be treated and mixed by stirring. It may be a continuous processing method in which a liquid to be processed is passed through a column filled with Fe-supported cation exchange resin.

  In any case, the higher the water temperature during the arsenic adsorption treatment, the higher the adsorption rate. Therefore, the water temperature during the treatment is preferably 0 to 99 ° C., particularly 20 to 50 ° C. When the water temperature is equal to or higher than the above lower limit, the treatment can be performed with high adsorption efficiency. If the water temperature becomes excessively high, the liquid to be treated cannot maintain the liquid phase.

  Further, if the pH of the liquid to be treated at the time of arsenic adsorption treatment is high, precipitation of Fe ions is generated, and if it is too low, Fe ions leak and the amount of adsorption decreases, so that the liquid to be treated at the time of arsenic adsorption treatment has a pH of 2 It is preferable that it is in the range of ˜4, particularly 2.5 to 3.5. Therefore, when the pH of the liquid to be treated falls outside this range, it is preferable to adjust the pH with an acid or an alkali. Examples of the alkali used for adjusting the pH of the liquid to be treated include lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, and ammonium hydroxide. Is preferred. Examples of the acid include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, oxalic acid and the like, and hydrochloric acid and sulfuric acid are particularly preferable.

  When performing an arsenic adsorption treatment in a batch processing method in which an Fe-supported cation exchange resin is added to the liquid to be treated and mixed by stirring, the amount of Fe-supported cation exchange resin used varies depending on the arsenic concentration in the liquid to be treated. Usually, the arsenic adsorption capacity (arsenic adsorption amount) of the Fe-supported cation exchange resin obtained by the above-described Fe-supporting treatment is about 0.1 to 1.5 mmol / g-dry resin. It is preferable to determine the amount of Fe-supported cation exchange resin in consideration of the performance. The stirring and mixing time is usually preferably about 0.1 to 3 hours.

On the other hand, when the liquid to be treated is passed through a column packed with Fe-supported cation exchange resin, the liquid passing SV is preferably ¹ to 200 hr ⁻¹ , particularly preferably 2 to 50 hr ⁻¹ . If the SV is too low, the processing efficiency is poor, and it takes a long time to process a predetermined amount of the liquid to be processed. However, if the SV is excessively high, the arsenic in the liquid to be processed may not be sufficiently adsorbed. .

  The liquid to be treated may be an upward flowing liquid or a downward flowing liquid.

The Fe-supported cation exchange resin used for the arsenic adsorption treatment of the liquid to be treated is treated with an alkali having a pH of 10 or more, more preferably pH 13 or more to recover the arsenic adsorbed on the resin and regenerate the Fe-supported cation exchange resin. can do.
The Fe ions supported on the cation exchange resin are not eluted by such an alkali treatment. Therefore, the recycled Fe-supported cation exchange resin can be reused for arsenic adsorption treatment by washing with pure water. can do.

[Fe ion capture treatment with Na-supported cation exchange resin]
As described above, when the arsenic adsorption amount of the Fe-supported cation exchange resin increases, Fe ions may leak out. In particular, when the electrolyte concentration of the liquid to be treated is high and the ionic strength I is 0.5 mol / L or more, the tendency of Fe ions to leak out increases. Therefore, in this case, it is preferable to capture the leaked Fe ions in combination with the Na-supported cation exchange resin.

  When the Na-supported cation exchange resin is used in combination, the Na-supported cation exchange resin may be used in combination with the Fe-supported cation exchange resin. It may be used as is. That is, in the case of the batch processing method described above, the Na-supported cation exchange resin may be added together with the Fe-supported cation exchange resin in the liquid to be treated and mixed with stirring, and the Fe-supported cation exchange resin may be added to the liquid to be treated. After stirring and mixing, the Fe-supported cation exchange resin may be subjected to solid-liquid separation, and then the Na-supported cation exchange resin may be added to the separated liquid and stirred and mixed.

  In the case of the continuous processing method, the column is filled with a mixture of Fe-supported cation exchange resin and Na-supported cation exchange resin, and a mixed bed of Fe-supported cation exchange resin and Na-supported cation exchange resin is formed in the column to be treated. The liquid may be passed, or a two-layer system in which an Fe-supported cation exchange resin bed is formed on the inlet side of the liquid to be treated in one column and an Na-supported cation exchange resin bed is formed on the outlet side. Alternatively, using a column packed with Fe-supported cation exchange resin and a column packed with Na-supported cation exchange resin, the liquid to be treated was passed through the Fe-supported cation exchange resin-filled column, and then passed through the Na-supported cation-exchange resin packed column. May be.

  The amount of Na-supported cation exchange resin used in combination with the Fe-supported cation exchange resin is appropriately determined depending on the degree of leakage of Fe ions from the Fe-supported cation exchange resin.

  The Na-supported cation exchange resin that captures and adsorbs Fe ions can be regenerated by passing hydrochloric acid, sulfuric acid, or nitric acid solution and eluting As and Fe ions.

  In addition, when the Fe loading treatment was performed on the commercially available Na-type cation exchange resin by the above-described method, some of the cation exchange resins were not substituted with Na ions and Fe ions, and the Fe-supported cations were used as Na-supported cation exchange resins. It is mixed in exchange resin. However, only the Na-supported cation exchange resin mixed in the Fe-supported cation exchange resin as described above can adsorb other cations in the process liquid when the electrolyte concentration of the process liquid is high. Since the Na-supported cation exchange resin mixed in the treatment is used and Fe ions leaked from the Fe-supported cation exchange resin cannot be captured, it is preferable to use a Na-supported cation exchange resin separately.

[Phosphate ion capture treatment with Ca-supported cation exchange resin]
As described above, when phosphate ions are present in the liquid to be treated, the phosphate ions inhibit the arsenic adsorption action of the Fe-supported cation exchange resin. In this case, the Ca-supported cation exchange resin is used in advance. It is preferable to adsorb and remove phosphate ions in the treatment liquid.

  When the Ca-supported cation exchange resin is used in combination, the Ca-supported cation exchange resin is used so that the liquid to be treated comes into contact with the Fe-supported cation exchange resin after contacting with the Ca-supported cation exchange resin. Therefore, in the case of the batch processing method, for example, the Ca-supported cation exchange resin is added to the liquid to be treated, and the mixture is stirred and mixed, and then the Ca-supported cation exchange resin is solid-liquid separated. Add and mix with stirring.

  In the case of a continuous processing method, the liquid to be processed is passed as a two-layer system in which a Ca-supported cation exchange resin bed is formed on the inlet side of the liquid to be processed in one column and an Fe-supported cation exchange resin bed is formed on the outlet side. Liquid. Alternatively, using a column packed with a Ca-supported cation exchange resin and a column packed with an Fe-supported cation exchange resin, water to be treated is passed through the Ca-supported cation exchange resin-filled column and then passed through the Fe-supported cation exchange resin-filled column. To do.

  The amount of Ca-supported cation exchange resin used in combination with the Fe-supported cation exchange resin is appropriately determined depending on the amount of phosphate ions in the liquid to be treated.

  The Ca-supported cation exchange resin that has captured and adsorbed phosphate ions can be regenerated by passing a hydrochloric acid, sulfuric acid, or nitric acid solution and eluting As and phosphate ions.

  The arsenic adsorption device of the present invention that uses both a Ca-supported cation exchange resin and a Na-supported cation exchange resin together with an Fe-supported cation exchange resin is, for example, a Ca-supported cation exchange resin-filled column, an Fe-supported cation exchange, in terms of industrial practical use. The resin packed column and the Na-supported cation exchange resin packed column can be connected in series.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded.

[Cation exchange resin]
The details of the cation exchange resins (all of which are Na-type cation exchange resins) used in the following examples, comparative examples, and reference examples are as shown in Table 1 below.

[Reference Examples 1 to 7, Comparative Example 1]
[Processed liquid]
In Reference Examples 1 to 7 and Comparative Example 1, the arsenic aqueous solution used as the liquid to be treated in the arsenic adsorption experiment was 1N nitric acid aqueous solution and 1N potassium hydroxide aqueous solution, disodium hydrogen arsenate · 7 crystal water (Na ₂ HAsO ₄ 7H ₂ O) is added to adjust the arsenic concentration to 10 mg / L, the ionic strength I to 0.05 mol / L, and the pH to 3.0.

[Analysis of Fe loading of cation exchange resin]
The amount of Fe supported on the cation exchange resin was analyzed by high frequency inductively coupled plasma emission spectroscopy (ICP).

[Analysis of arsenic concentration]
The arsenic concentration in the treated water was determined by high frequency inductively coupled plasma optical emission spectrometry (ICP). The detection limit of arsenic concentration by ICP is 0.01 mg / L.

[Reference Example 1]
And stirred for 1 hour at room temperature added to an aqueous solution 1L of cation exchange resin (Diaion SK104) 10 mL 0.2 wt% ferric nitrate-9 crystal water _{(Fe (NO 3) 3 ·} 9H 2 O). A nitric acid aqueous solution and a potassium hydroxide aqueous solution were added thereto to adjust the pH of the solution to 2.0.
The Fe carrying amount of the cation exchange resin thus subjected to Fe carrying treatment was 1.73 meq / g-resin.
The Fe-supported cation exchange resin was packed in a column having an inner diameter of 9 mm and a length of 15 cm as a dry resin amount of 1.0 g (about 2.4 mL), and then demineralized water was passed at room temperature at SV10 hr ⁻¹ for 1 hour. Washed with water.
The arsenic aqueous solution was passed therethrough at 30 ° C. with SV 20.7 hr ⁻¹ in a downward flow.

Arsenic leaks were not observed in the treated water (column effluent) for 72 hours from the start of liquid flow (below the detection limit), but arsenic began to be detected in the treated water after 72 hours. After 120 hours from the start, the arsenic concentration of the treated water was 9 mg / L.
The arsenic adsorption amount of the cation exchange resin at this time was 0.799 mmol / g-resin and 59.9 mg-As / g-resin.

[Reference Example 2]
To 5 g of cation exchange resin (Diaion SK104), 100 mL of 0.2 wt% aqueous ferric nitrate solution was added and stirred at room temperature for 1 hour. A nitric acid aqueous solution and a potassium hydroxide aqueous solution were added thereto to adjust the pH of the solution to 2.0 to obtain an Fe-supported cation exchange resin. The amount of Fe supported on the obtained Fe-supported cation exchange resin was 1.659 meq / g-resin.
0.5 g of this Fe-supported cation exchange resin is put in 200 mL of an arsenic aqueous solution as a dry resin amount, shaken with a shaker for 1 hour, and the arsenic adsorption amount of Fe-supported cation exchange resin is determined from the analysis result of the arsenic concentration of the supernatant after shaking. Was 0.037 mmol / g-resin, 2.77 mg-As / g-resin. The arsenic concentration in the supernatant was 3.1 mg / L.

[Reference Example 3]
In Reference Example 2, an adsorption experiment was conducted in the same manner except that the shaking time was 96 hours and the resin addition amount was 0.02 g. As a result, the arsenic concentration of the supernatant was 4.5 mg / L, Fe The arsenic adsorption amount of the supported cation exchange resin was 0.73 mmol / g-resin and 54.7 mg-As / g-resin.

[Reference Example 4]
In Reference Example 2, the Fe-supported cation exchange resin obtained by Fe-supporting treatment was pulverized using a mortar, and the pulverized resin was classified using a sieve having an opening of 75 μm to 150 μm (average particle size 150 μm, uniformity coefficient 1.6). As a result of analyzing the Fe carrying amount of the Fe carrying cation exchange resin after pulverization and classification, it was 1.659 meq / g-resin.
When an adsorption experiment was conducted in the same manner as in Reference Example 2 using the Fe-supported cation exchange resin after pulverization and classification, when the resin addition amount was 0.03 g, the arsenic concentration of the supernatant was 3.0 mg / L, the arsenic adsorption amount of the Fe-supported cation exchange resin was 0.63 mmol / g-resin, 46.9 mg-As / g-resin.

[Reference Example 5]
Except that Diaion MCI-GEL CK04S was used as the cation exchange resin, the Fe carrying treatment was performed in the same manner as in Reference Example 2. As a result, the Fe carrying amount of the obtained Fe carrying cation exchange resin was 2.285 meq / g-resin.
Using this Fe-supported cation exchange resin, an adsorption experiment was conducted in the same manner as in Reference Example 2. When the amount of resin added was 0.02 g, the arsenic concentration of the supernatant was 4.6 mg / L, and Fe-supported cation exchange was performed. The arsenic adsorption amount of the resin was 0.72 mmol / g-resin and 53.9 mg-As / g-resin.

[Reference Example 6]
Except that Diaion PK208 was used as the cation exchange resin, the Fe carrying treatment was performed in the same manner as in Reference Example 2, and the Fe carrying amount of the obtained Fe carrying cation exchange resin was 1.50 meq / g-resin. Met.
When an adsorption experiment was performed using this Fe-supported cation exchange resin in the same manner as in Reference Example 2, the arsenic concentration of the supernatant was 1.6 mg / L, and the arsenic adsorption amount of the Fe-supported cation exchange resin was 0.045 mmol / g. -Resin, 3.4 mg-As / g-resin.

[Reference Example 7]
Except that Diaion RCR160M was used as the cation exchange resin, the Fe carrying treatment was carried out in the same manner as in Reference Example 2, and the Fe carrying amount of the obtained Fe carrying cation exchange resin was 1.309 meq / g-resin. Met.
Using this Fe-supported cation exchange resin, an adsorption experiment was conducted in the same manner as in Reference Example 2. When the resin addition amount was 0.2 g, the arsenic concentration of the supernatant was 2.6 mg / L, and Fe-supported cation exchange was performed. The arsenic adsorption amount of the resin was 0.10 mmol / g-resin and 7.5 mg-As / g-resin.

[Comparative Example 1]
In Reference Example 1, when the adsorption experiment was conducted in the same manner except that the dry resin amount was 0.5 g (about 1.2 mL) and the flow rate of the arsenic aqueous solution was SV78.6 hr ⁻¹ , the flow start was started. Arsenic of about 0.5 mg / L leaked into the treated water from the beginning.

[Reference Example 8]
<Processed liquid>
The liquids to be treated used in the adsorption experiment are as follows.

(Phosphorus adsorption experiment)
The phosphorus aqueous solution used as the liquid to be treated in the phosphorus adsorption experiment was obtained by adding 1N nitric acid aqueous solution and 1N sodium hydroxide aqueous solution and disodium hydrogen phosphate (Na ₂ HPO ₄ · 7H ₂ O) to obtain a phosphorous concentration = 10 mg / L, ionic strength I = 0.05 mol / L, and pH = 9.0.

(Arsenic adsorption experiment)
The arsenic aqueous solution used as the treatment liquid in the arsenic adsorption experiment was added with 1N nitric acid aqueous solution and 1N sodium hydroxide aqueous solution, and disodium hydrogen arsenate · 7 crystal water (Na ₂ HAsO ₄ · 7H ₂ O) to obtain an arsenic concentration. = 10 mg / L, ionic strength I = 0.05 mol / L, and pH was adjusted to 11.0.

<Analysis of Ca loading of cation exchange resin>
The amount of Ca supported on the cation exchange resin was analyzed by high frequency inductively coupled plasma emission spectroscopy (ICP).

<Analysis of phosphorus concentration>
The phosphorus concentration in the treated water was developed using the molybdenum blue method, and the analysis was performed by the absorbance measurement method.

<Production of Ca-supported cation exchange resin>
To a dry weight of 5.0 g of cation exchange resin (Diaion SK104), 1000 mL of a 0.1 wt% aqueous solution of calcium chloride was added and stirred at room temperature for 1 hour. A nitric acid aqueous solution and a potassium hydroxide aqueous solution were added thereto to adjust the pH of the solution to 3.0 to obtain a Ca ion-supporting cation exchange resin. The amount of Ca supported on the obtained Ca supported cation exchange resin was 2.045 meq / g-resin.

<Adsorption experiment of phosphorus>
1.0 g of this Ca-supported cation exchange resin is put in 200 mL of an aqueous phosphorous solution as a dry resin amount, shaken with a shaker for 1 hour, and the phosphorus adsorption of the Ca ion-supported cation exchange resin is determined from the analysis result of the phosphorus concentration of the supernatant after shaking. When the quantity was calculated | required, they were 0.592 mmol / g-resin and 18.33 mg-P / g-resin. The phosphorus concentration in the supernatant was 5.32 mg / L.

<Arsenic adsorption experiment>
In 200 mL of an arsenic aqueous solution, 1.0 g of a Ca ion-supported cation exchange resin as a dry resin amount is added and shaken for 1 hour with a shaker. From the analysis result of the arsenic concentration of the supernatant after shaking, the arsenic of the Ca ion-supported cation exchange resin is obtained. The adsorption amount was determined to be 0.0007 mmol / g-resin and 0.04997 mg-As / g-resin. The arsenic concentration in the supernatant was 9.79 mg / L.

  From the above experiment, from a mixed solution of arsenic and phosphoric acid, phosphoric acid, which becomes an interfering ion during the adsorption of arsenic ions, is pretreated with a Ca ion-supporting exchange resin first, and a solution with a reduced phosphoric acid concentration is Fe ion. It can be seen that arsenic ions can be captured by the supported cation exchange resin.

[Reference Example 9]
<Preparation of Fe (III) solution for Fe support>
An Fe (III) solution was prepared in a 2 L volumetric flask so that the Fe (III) concentration was 1,000 mg / L with ferric nitrate · 9 crystal water. After this Fe (III) solution was transferred to a 3,000 mL beaker, the pH was adjusted to 2 while stirring with an impeller to prepare a Fe (III) solution for supporting Fe. The pH was adjusted by preparing a solution in which 1M HNO ₃ and 1M NaOH were appropriately diluted, and adding each drop with a micropipette. At that time, as much as possible, NaOH was not added to reach the target pH.
When the target pH was reached, the solution was collected using a syringe while stirring and filtered through a membrane filter having a pore size of 0.45 μm. The obtained filtrate was designated as filtrate I.

<Fe (III) loading on cation exchange resin>
A vacuum-dried cation exchange resin (Diaion SK104) was added to the Fe (III) solution for supporting Fe. After stirring for 1 hour, the solution was collected with a syringe in the same manner as in filtrate I, and filtered. The obtained filtrate is designated as Filtrate II.
For the filtrate I and the filtrate II, the Fe (III) concentration was measured with an ICP emission spectroscopic analyzer.
After collecting the filtrate II, suction filtration was performed using an aspirator using a filter paper having a pore size of 0.45 μm in order to collect the cation exchange resin. At that time, in order to avoid adhesion of Fe (III) and precipitation formation on the surface of the cation exchange resin, washing was performed with a solution adjusted to about pH 2 by adding nitric acid. The cation exchange resin obtained by filtration and washing was heated and dried for about 24 hours to obtain a Fe (III) -supported cation exchange resin.
The amount of Fe (III) supported per dry resin weight determined from the Fe (III) concentration and the amount of cation exchange resin in filtrate I and filtrate II was 1.75 meq / g-resin.

<Column test>
An acrylic column having an inner diameter of 9 mm and a length of 150 mm was prepared by filling a non-woven fabric, an Fe (III) -supporting tree cation exchange resin, and a non-woven fabric in this order. The filling amount of the Fe (III) -supported cation exchange resin was 2.0 g-resin or 1.0 g-resin by dry weight.
Using EYELA's MP-2000 type peristaltic tube pump and SMP-21 type cassette tube pump, arsenic aqueous solution is applied to each column at 50 mL / hr (when the resin packing amount of the column is 2.0 g), or 25 mL / hr. The liquid was passed in an upward flow at a constant flow rate (when the resin packing amount of the column was 1.0 g). This flow rate corresponds to 1 BV for 1 hour.
In supplying the arsenic aqueous solution, pure water was passed in advance for about 1 hour for cleaning, and then the arsenic aqueous solution was passed at the same flow rate.
The column effluent was collected at regular time intervals, and the As (V) concentration of the collected liquid was measured with a desktop ICP emission spectroscopic analyzer.
The breakthrough curve of As (V) obtained from the measurement result of As (V) concentration is shown in FIG.
As can be seen from FIG. 1, As (V) ions did not leak up to 192 hours after the start of liquid flow, that is, up to a treatment amount of 192 BV, and arsenic could be adsorbed and removed by the Fe (III) -supported cation exchange resin. .

[Example 1]
As described below, after the first stage batch test was performed on the liquid to be treated, the second stage batch test was performed.

<Processed liquid>
The liquid to be treated was prepared so that the pH was 11, the As (V) concentration was 10.731 ppm, and the P concentration was 4.25 ppm. For the preparation of the liquid to be treated, a 1N nitric acid aqueous solution and a 1N sodium hydroxide aqueous solution, disodium hydrogen phosphate (Na ₂ HPO ₄ · 7H ₂ O), disodium hydrogen arsenate · 7 crystal water (Na ₂ HAsO ₄ · 7H ₂ O) was used. The same applies to Comparative Examples 2 and 3 below.

<First stage batch test>
When 1 g / L of the Ca-supported cation exchange resin produced in the same manner as in Reference Example 8 was added to the above-mentioned liquid to be treated as a dry resin amount and stirred for 1 hour, the residual As (V) concentration in the solution was 9. The residual P concentration was 889 ppm and 1.065 ppm.

  From the results of the first-stage batch test, it can be seen that only P was selectively removed in the Ca-supported cation exchange resin.

<Second stage batch test>
The solution after the first-stage batch test was filtered to remove the Ca-supported cation exchange resin, and a 1N nitric acid aqueous solution was added to adjust the pH to 3. Thereafter, 1 g / L of Fe-supported cation exchange resin produced in the same manner as in Reference Example 9 was added to this filtrate as a dry resin amount and stirred for 1 hour. As a result, the residual As (V) concentration in the solution was 4 372 ppm.

  From the results of the second batch test, the arsenic adsorption device using the Ca-supported cation exchange resin and the Fe-supported cation exchange resin was almost the same as the removal ability of the As (V) single solution. That is, since P ions (phosphate ions) that are interfering ions are removed by the Ca-supported cation exchange resin, sufficient As (V) ions can be obtained even in a solution in which As (V) ions and P ions coexist. Removal was possible.

[Comparative Example 2]
A batch test was performed on the liquid to be treated as follows.

<Processed liquid>
The liquid to be treated was prepared so that the pH was 3, the As (V) concentration was 11.165 ppm, and the P concentration was 4.375 ppm.

<Batch test>
1 g / L of Fe-supported cation exchange resin produced in the same manner as in Reference Example 9 was added to the liquid to be treated as a dry resin amount and stirred for 1 hour, but both As (V) and P ions were mostly Fe-supported cation exchange. It remained in the solution without being trapped by the resin.

[Comparative Example 3]
A batch test was performed on the liquid to be treated as follows.

<Processed liquid>
A liquid to be treated was prepared so that the pH was 3, the As (V) concentration was 10.78 ppm, and the P concentration was 4.17 ppm.

<Batch test>
A mixture of the Ca-supported cation exchange resin prepared in the same manner as in Reference Example 8 and the Fe-supported cation exchange resin prepared in the same manner as in Reference Example 9 (resin ratio = 1: 1) was dried on the liquid to be treated. 1 g / L of resin was added and stirred for 1 hour.
As a result, the residual As (V) concentration in the solution was 9.134 ppm and the residual P concentration was 3.672 ppm, and both As (V) and P ions were hardly removed.

[Comparative Example 4]
<Preparation of solution>
Arsenic / phosphoric acid mixed aqueous solution used as the liquid to be treated was 1M HNO ₃ and 1M NaOH, disodium hydrogen arsenate · 7 crystal water (Na ₂ HAsO ₄ · 7H ₂ O) and disodium hydrogen phosphate (Na ₂ HPO _4). ) Was added so that the arsenic concentration = 10 mg / L, AsO ₄ / PO ₄ ³⁻ molar ratio = 1.0, ionic strength = 0.05, and pH = 13.

<Preparation of resin>
1M HNO ₃ and 1M NaOH and calcium nitrate tetrahydrate (Ca (NO ₃ ) ₂ .4H ₂ O) were adjusted so that the Ca (II) concentration = 1000 mg / L and pH = 3. Cation exchange resin (Diaion SK104) 7.5g / L was added here, and it stirred at room temperature for 1 hour. In order to collect the resin, suction filtration was performed using an aspirator using 0.45 μm filter paper. After filtering and washing, it was heat-dried for about 24 hours to obtain a Ca (II) -supporting resin. The amount of Ca (II) supported by the cation exchange resin thus subjected to the Ca (II) support treatment was 2.05 mmol-Ca / g-resin.

<Liquid flow method>
After filling 1.9 g of this Ca (II) -supported cation exchange resin into an acrylic column having an inner diameter of 9 mm × length of 150 mm as a dry weight, pure water was flowed at room temperature at a flow rate of 50 ml / hr (SV = 21.8 hr ⁻¹ ). The solution was passed for 1 hour. The above arsenic / phosphoric acid mixed aqueous solution was passed therethrough at a flow rate of 50 ml / hr (SV = 21.8 hr ⁻¹ ) at room temperature.
As a result, no phosphorus leak was observed in the treated water at the beginning of the liquid flow, but 2.1 mg / L of phosphorus leaked after 21 hours and 12.5 mg / L of phosphorus leaked after 44 hours. The phosphorus adsorption amount to the resin at this time was 0.36 mmol / L. At this time, arsenic did not adsorb to the resin, but leaked into the whole treated water. The analysis result of the metal concentration of the treated water is shown in FIG.

Claims (10)

An arsenic adsorbing device comprising an arsenic adsorbent that comes into contact with a liquid to be treated and adsorbs arsenic in the liquid to be treated, comprising a cation exchange resin using Fe ions as a counter ion as the arsenic adsorbent and Ca ions. A cation exchange resin as a counter ion,
An arsenic adsorption apparatus having a structure in which the liquid to be treated comes into contact with a cation exchange resin using Ca ions as a counter ion before coming into contact with the cation exchange resin using Fe ions as a counter ion.   2. The arsenic adsorption apparatus according to claim 1, wherein the cation exchange resin having the Fe ion as a counter ion is a gel type.   3. The arsenic adsorption apparatus according to claim 1, wherein an average particle diameter of the cation exchange resin having Fe ions as a counter ion is 800 μm or less.   The arsenic adsorption apparatus according to any one of claims 1 to 3, wherein a uniformity coefficient of a particle size of the cation exchange resin using the Fe ion as a counter ion is 1.2 or less. An arsenic adsorption method in which a liquid to be treated is brought into contact with an arsenic adsorbent and arsenic in the liquid to be treated is adsorbed on the arsenic adsorbent, wherein the cation exchange resin uses Fe ions as the arsenic adsorbent as a counter ion And a cation exchange resin with a Ca ion as a counter ion,
An arsenic adsorption method comprising contacting the liquid to be treated with a cation exchange resin using Ca ions as a counter ion before contacting with the cation exchange resin using Fe ions as a counter ion.   The arsenic adsorption method according to claim 5, wherein the cation exchange resin having the Fe ion as a counter ion is a gel type.   The arsenic adsorption method according to claim 5 or 6, wherein an average particle diameter of the cation exchange resin using Fe ions as a counter ion is 800 µm or less.   The arsenic adsorption method according to any one of claims 5 to 7, wherein a uniformity coefficient of a particle size of the cation exchange resin using the Fe ion as a counter ion is 1.2 or less.   The arsenic adsorption method according to any one of claims 5 to 8, wherein the pH of the liquid to be treated is 2 to 4. A method of passing the liquid to be treated through a packed bed of a cation exchange resin using Fe ions as a counter ion, wherein the liquid SV of the liquid to be treated is ¹ to 200 hr ^−1. Item 10. The arsenic adsorption method according to any one of Items 5 to 9.

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