JP4637737B2 - Regeneration method of boron adsorbent - Google Patents

Description

  The present invention relates to a method for regenerating a high boron-containing boron adsorbent used as a boron adsorbent.

  The water may contain boron. Boron is widely distributed in nature and may be contained in seawater, volcanic groundwater, hot spring water, and the like. Recently, boron and fluorine have been added as environmental standard items for the protection of human health related to water pollution in public water areas and groundwater related to drainage. Boron is an essential element for the growth of plants, but it has been found that excessive amounts have an adverse effect on plant growth. Furthermore, although it is not necessarily clear for the human body, it has been pointed out that it may cause health problems such as decreased reproductive function when continuously ingested even at low concentrations. There is a place that establishes an allowable concentration in wastewater of 0.5 to 2 mg / l or less according to the regulations of the mechanism.

  In Japan, the “Soil Contamination Countermeasures Law” was promulgated on May 29, 2002 and came into effect on February 15, 2003. Boron is one of the substances subject to this countermeasure, and Article 5 of them states that the soil content standard is 400 mg or less per 1 kg of soil, the soil elution amount standard is 1 mg or less per 1 liter of test solution, and the soil environment standard A strict standard of 1 mg or less per liter of test solution was established. Since 1 mg / l or less has been announced and implemented as an environmental standard for boron, boron removal from wastewater such as industrial wastewater, waste incineration sewage wastewater, and geothermal power generation wastewater containing these boron has become necessary. .

  Up to now, as a method for treating boron-containing wastewater, a method of removing it as an insoluble precipitate by adding aluminum sulfate or slaked lime to the wastewater as a remover, a boron-selective chelate resin or a rare earth hydroxide compound-containing material, etc. A method of adsorbing with an adsorbent, a method of treating with a reverse osmosis membrane, and the like are known. Although each has advantages, there is no suitable method for regenerating these removers and adsorbents, and they have not been widely used.

  An adsorbent made of a boron selective adsorption resin having an N-methylglucamine group, which is a representative resin of a boron-selective chelate resin, is definitely desired to be recycled, and Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-094051). In the case of performing a regeneration treatment in which boron adsorbed on a boron selective adsorption resin having an N-methylglucamine group is eluted with a mineral acid and then passed through an NaOH solution to convert the boron selective adsorption resin into a free form. The pH of the NaOH solution is controlled so that the pH of the solution surrounding the boron selective adsorption resin is 7.5 to 8.5 after washing and back washing after the NaOH solution is passed. A method for regenerating a boron selective adsorption resin characterized by the above has been proposed. However, since it is not easy to perform the above-mentioned operation, it has become a big problem in use.

  As an improved method of the above method, Patent Document 2 (Japanese Patent Laid-Open No. 2002-233864) discloses a mineral acid on a boron selective adsorption resin having an N-methylglucamine group obtained by treating waste water containing boron. In recovering the boron eluent by passing the solution, the period for performing the recovery is divided into at least two, and the period during which there is less impurities is determined by the pH fluctuation of the eluent, and only the eluent is used as the boron recovery solution. A method for treating a boron-containing eluent eluted from a boron selective adsorption resin, characterized in that it precipitates as a hydroxide by reacting with a hydroxide ion of Patent Document 3 (Japanese Patent Laid-Open No. 2003-326251) A method of removing boron from a solution containing a metal that produces succinate and boron, a metal that precipitates as a hydroxide by reacting with the hydroxide ions, By making the solution containing elemental alkaline, the metal in the solution is precipitated as a hydroxide, and a precipitation step for removing the metal from the solution and using an adsorbent, after the completion of the precipitation step A boron adsorption step for adsorbing boron in the solution of the solution, a boron elution step for eluting boron from the adsorbent on which the boron is adsorbed using an acid solution, and an boron solution using the alkaline solution And an adsorbent regeneration step for making the adsorbent eluted with adsorbent usable in the boron adsorption step, the adsorbent has at least two OH groups and is insoluble in water, It is an organic compound having a property of adsorbing boron, eluting boron adsorbed by an acid solution, and regenerating into an adsorbent capable of adsorbing boron by an alkaline solution. Ho There is an element removal method. However, although there are differences in usage and advantages, the disadvantage of complicated pH adjustment has not been solved.

  Therefore, among the adsorbents, a method of adsorbing with a boron adsorbent without the above-described drawbacks is attracting attention. Regarding the adsorbent regeneration method, Patent Document 4 (Japanese Patent Laid-Open No. 59-132986) discloses that the regeneration method of the special resin adsorbent comprising the boron selective adsorption resin having the N-methylglucamine group is desorbed by acid. A regeneration method is described in which boron is eliminated using an alkaline aqueous solution opposite to the method. However, in this method, it has been confirmed that the adsorption of boron at the time of regeneration occurs slowly, and there is a problem that a large amount of water is required to wash out boron from the adsorbent.

  Further, as an improved method of the above method, Patent Document 5 (Japanese Patent Application Laid-Open No. 2004-057870) discloses an adsorption step in which boron-containing water is brought into contact with a granule carrying a rare earth element hydroxide to adsorb and remove boron. And a boron-containing water treatment method having a desorption step of desorbing boron by bringing the granulated body adsorbing boron into contact with an alkaline aqueous solution, or before contacting the granulated body with the alkaline aqueous solution A method for treating boron-containing water, characterized by having a neutralizing acid treatment step in which the granulated body is brought into contact with a strong acid aqueous solution after being made, has been proposed. Although this method provides a treatment method for boron-containing water that can continue the treatment stably without deteriorating the boron adsorption performance of the granulated body, if the operation having a strong acid treatment step has too much acid, If there is little acid that affects boron desorption, the improvement of the method including the inside of the particulate adsorbent becomes insufficient, so there is a disadvantage of complicated pH adjustment in the sense that the operation is complicated, and the initial stage of the drainage Adjustment from which pH = 7 to 8 must be maintained on the basis of drainage is also complicated.

  In addition, the above-mentioned problems have not been solved in the regenerating operation, and the granule supporting the rare earth element hydroxide adsorbed with boron is desorbed with an alkaline aqueous solution, and then the granulation is performed with a large amount of water. Even after washing the granules, it was found that boron leaked out from the granules little by little, and it took a considerable amount of time to carry out water washing to below the discharge standard of 10 mg / l. In addition to the time required, a considerable amount of water is required to pass water, and the water used at the time of regeneration is a high-concentration boron solution, so it is extraneous to treat a huge amount of wastewater. It will take time and effort. In other words, it can be seen that the remaining adsorbed boron elutes without stopping even if it is washed for a long time (for example, 5 hours or more and the water flow rate is 15 times or more) with a large amount of washing water, and the adsorption operation is performed until the elution stops. I can't.

Therefore, it is conceivable to take out the granulated product and neutralize it with a small amount of strong acid after alkali removal as a countermeasure. However, it seems difficult to neutralize the granulated product for some reason. It was found that neutralization cannot prevent boron from leaking into the waste water little by little, and has the same disadvantage as the large amount of washing water described above.
JP 2003-094051 A JP 2002-233864 A JP 2003-326251 A JP 59-132986 A JP 2004-057870 A

  Under such circumstances, the present invention is a boron adsorbent which has been used as a boron adsorbent and has adsorbed boron at a high concentration. It is an object of the present invention to provide a method for regenerating a boron adsorbent capable of suppressing the above in a short time.

  The present inventors diligently researched the above problems, and after treating a boron adsorbent used as a boron adsorbent with an alkaline aqueous solution, it was further treated with a compound comprising at least one of an alkaline earth metal salt or an ammonium salt. As a result, the present invention has been found.

That is, the present invention relates to the following (1) to (7).
(1) a boron adsorbent containing spent rare earth hydroxides and / or hydrated oxide is contacted with an alkaline aqueous solution, after elimination of boron to a predetermined concentration range, the first alkaline earth metal salts A method for regenerating a boron adsorbent, comprising contacting with an aqueous solution of a compound comprising at least species.
(2) The method for regenerating a boron adsorbent according to (1), wherein the concentration range is 10 to 1000 mg / l.
(3) (1) or (2) reproducing the method of the boron adsorbent, wherein the said alkaline earth metal salt is magnesium chloride.
( 4 ) The boron adsorbent is an aggregate of rare earth element hydroxides and / or hydrated oxides having an average secondary particle size of 0.2 to 25 microns, and has a polymer concentration on the surface of the granules. The method for regenerating a boron adsorbent according to any one of (1) to ( 3 ) above, comprising a high layer.
( 5 ) After passing an alkaline solution into a boron adsorbent-filled container having a boron adsorbent containing a used rare earth element hydroxide and / or a hydrated oxide, it is composed of one or more alkaline earth metal salts. A method for regenerating a boron adsorbent, comprising adding a compound and passing a boron-containing liquid at a water flow rate of 15 times or less so that the boron concentration per volume of the contained water is 10 mg / l or less.
( 6 ) The method for regenerating a boron adsorbent according to any one of (1) to (5), wherein the boron-containing agent is for wastewater treatment.

  By the regeneration method of the present invention, the boron adsorbent in which boron is adsorbed at a high concentration hardly recovers the boron adsorbent during the regeneration process in a short time without substantially reducing the original boron adsorption capacity and recovers the boron adsorbent. In addition, the boron adsorbent can be regenerated without the boron leaking beyond the standard in the waste water during the regeneration process.

The present invention will be specifically described below.
The boron adsorbent used in the present invention is a mixture particle of a polymer resin and a rare earth element hydroxide and / or a hydrated oxide, and the surface of the particle has a high concentration of thin porous polymer resin. Adsorbent with a layer.
The mixture particles contain rare earth element hydroxide and / or hydrated oxide at a ratio of 600 parts by weight or more per 100 parts by weight of the polymer resin. When the rare earth element content is less than 600 parts by weight, the amount of boron adsorbed is small, and even if the boron adsorbent is regenerated, the adsorptivity of the prior art level cannot be exceeded.

  The mixture particles may be in the form of particles and shaped so that water can pass through. Any structure may be used as long as the mixture can be filled in a column or the like without causing any trouble in passing water. A net-like molded body may satisfy the object of the present invention. Moreover, if it is a substantially uniform round granular body, the average particle diameter of 0.2 mm-5.0 mm is used preferably. If the particle size is 0.2 mm or less, the packing density becomes high and the water flow resistance becomes high, and the regeneration workability tends to be inferior. As a result, recovery of boron adsorption ability tends to be slow.

  In addition, a preferable internal cross-sectional structure of the adsorbent mixed particle body of the present invention is that a porous skin layer of a polymer resin is formed as schematically shown in FIG. It has a structure with a polymer resin layer with a very high concentration, with a cavity in the center, radial thin voids from the cavity toward the surface, and in the vicinity of the inside of the surface layer with a high resin concentration. A cross-sectional structure in which a large number of fine voids are present densely than the inside is preferable. Although the reason is not clear, it is presumed that this structure makes the reproduction state very good.

  The polymer resin of the present invention is an organic polymer resin, a natural polymer, or a derivative of these resins that has higher heat resistance than an anion exchange resin or a chelate resin and does not elute into water. The number average molecular weight may be 500 or more, preferably 2000 or more. The molecular weight is too low or the water-soluble hydrophilic resin is not preferable in terms of elution, and the elution is further increased and the heat resistance is low at a high temperature.

  Preferable resins include fluorine resins such as acetalized polyvinyl alcohol resins, polyvinylidene fluoride resins, polytetrafluoroethylene resins, and the like. For example, a polyvinylidene fluoride resin and a polyvinylidene fluoride hexafluoride propylene copolymer resin can be said to be preferable because they can easily contain a rare earth element hydroxide and / or a hydrated oxide at a high concentration and are excellent in water resistance and chemical resistance. The same applies to polytetrafluoroethylene resin and its (co) polymer. In addition, organic polymers having excellent water resistance, natural polymers, and derivatives thereof can be said to be useful resins that meet the object of the present invention.

  The rare earth element hydroxide and / or hydrated oxide of the present invention is a 3 (3A) group rare earth element according to the periodic table of elements of 1991, and is scandium Sc, yttrium Y, lanthanoid element, lanthanum La, cerium Ce. , Praseodymium Pr, neodymium Nd, promethium Pm, samarium Sm, europium Eu, cadmiumium Gd, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, ytterbium Yb, lutetium Lu. Among these, Ce is a preferable element in accordance with the object of the present invention, and tetravalent Ce is preferable. Mixtures of these rare earth element hydroxides and / or hydrated oxides are also useful.

  The rare earth element hydroxide and / or hydrated oxide of the present invention preferably contains water, and this moisture content is a conventional level of 600 parts by weight or more per 100 parts by weight of a polymer resin, which has been considered impossible. The adsorption performance of boron adsorbents made by a technology containing a high content of rare earth element hydroxide and / or hydrated oxide far exceeding (400 parts by weight per 100 parts by weight of resin) 4 times astonishing value.

  The reason for this is not clear, but the water content improves the fluidity of the rare earth element hydroxide and / or the hydrous oxide, so that appropriate mixing with the resin is performed, and the rare earth element in which the water is secondarily aggregated The effect of making the hydroxide and / or hydroxide a suitable particle size, creating voids in the secondary particles to allow contact with moderate boron-containing water, and the hydroxide into the oxide It is presumed that the boron adsorption ability is increased as a result of preventing the return.

  This moisture content is measured by placing a hydrous rare earth element hydroxide and / or a hydrous oxide in a crucible and leaving it at a high temperature of 800 ° C. for 1 hour, and then evaporating the evaporated rare earth element hydroxide and / or Or the value which remove | divided with the amount of hydrated oxide is expressed by the moisture content.

  The secondary particles of the rare earth element hydroxide and / or hydrated oxide are aggregates of primary particles having an average particle diameter of 0.01 to 0.1 μm, and the average particle diameter of the secondary particles is 0. 2 to 25 microns is preferable, and 0.5 to 10.0 microns is preferable. If it is 2 microns or less, it may be wrapped with resin mixing and contact with the boron-containing water may be insufficient, and if it is 15 microns or more, mixing with the resin may be poor.

  In the regeneration method of the present invention, the compound consisting of one or more of alkaline earth metal salt or ammonium salt (hereinafter referred to as additive) to which boron is added after alkali elimination is preferably magnesium, calcium, strontium, barium, rubidium, It is a salt of a metal such as cesium such as hydrochloric acid, nitric acid or sulfuric acid, or a salt of ammonium such as hydrochloric acid, nitric acid or sulfuric acid. Among these, calcium chloride, ammonium chloride, ammonium nitrate, and magnesium chloride can change the pH to a neutral range in a relatively short time, and are more preferable in conformity with the object of the present invention.

  The amount of the compound consisting of one or more of the alkaline earth metal salt or ammonium salt may be 10 g / l or less, preferably 5 g / l or less in terms of aqueous solution concentration. In the case of a hydrated salt, the mass calculation is performed without the hydrated content.

  The regeneration of the adsorbent for boron is carried out by removing boron from the adsorbent with an alkaline aqueous solution and then passing an aqueous solution containing a compound composed of at least one of an alkaline earth metal salt or an ammonium salt at a concentration of 10 g / l or less. It is carried out by passing the liquid at a water magnification in the range of 3-15. The aqueous salt solution may be passed immediately after the elimination of boron by the alkaline aqueous solution in the regeneration step, or may be passed along with the actual solution after the regeneration step. By this operation, it is possible to reduce the boron concentration per volume of contained water to 10 mg / l or less by passing the liquid normally within the range of 3 to 5 and more surely 3 to 10. .

It is not clear what mechanism the effect of this additive is manifested, but it reacts with the alkali remaining in the resin to quickly lower the pH to the neutral range, thereby reducing the amount of boron released. It is inferred that it is suppressed.
The used adsorbent is, for example, an adsorbent that adsorbs 5 g or more of boron per 1 l of adsorbent. Further, desorbing boron to a low concentration with an alkaline aqueous solution is to wash the adsorbent adsorbing boron with an alkaline aqueous solution having a pH = 12 or more, preferably pH = 13 or more. The boron adsorbed by the above can be desorbed from the adsorbent, and the amount of boron adsorbed per liter of the adsorbent can be desorbed to, for example, 1 g or less, preferably 0.5 g or less.
Moreover, the aqueous alkaline solution used in the present invention is preferably an aqueous solution of sodium hydroxide, for example.
The boron adsorbent regenerated by the method of the present invention has an adsorption capacity even when used in combination with other batch, fixed bed, fluidized bed, moving bed, osmotic, reverse osmotic, and coprecipitation methods. It is preferable to maintain the activation.

Examples of the present invention and comparative examples are shown below.
The SV in the sentence is the superficial velocity (space velocity), the amount of water flow per adsorbent, and the water flow rate per liter of adsorbent. For example, when SV = 20, it means that water was passed at 20 l / hr.
Further, the water flow rate means how many times the amount of water has flowed per adsorbent volume. For example, when the water flow rate is 200 with 1 l of adsorbent, it means that 200 l of water has flowed.
The saturated adsorption amount is a value indicating the maximum amount of adsorption when boron is adsorbed to the adsorbent with a boron solution of a specific concentration, and varies depending on the boron concentration.

(Example 1, Comparative Example 1, Example 2, Comparative Example 2)
A solution was prepared by dissolving H ₃ BO ₃ reagent grade 1 in tap water to a (initial) concentration of 200 mg / l, and pH = 7 was confirmed. This is hereinafter referred to as tap water boron-containing liquid. Further, a solution was prepared by dissolving H ₃ BO ₃ reagent grade 1 in pure water to an (initial) concentration of 200 mg / l, and pH = 7 was confirmed. Hereinafter, this is referred to as pure water boron-containing liquid. Separately, a cerium hydroxide-containing powder was obtained with cerium hydroxide at a moisture content of 20% by weight with a low-temperature dryer at 70 ° C. This powder, a copolymer resin of vinylidene fluoride and propylene hexafluoride were dispersed in a solvent N-methyl-2-pyrrolidone to obtain a dispersion. Next, a rounded particle body (granulated body) having an average particle diameter of 0.70 mm having a ratio of 700 parts by weight of hydrous cerium hydroxide to 100 parts by weight of the resin was obtained from this dispersion using a granulator. There was a high concentration layer of the resin on the surface of the particles. Hereinafter, these particles are referred to as READ-B.

Examination of regeneration conditions Outline Check whether the behavior of boron is affected by passing an actual liquid (referred to as a treatment liquid containing boron) during washing with water during regeneration.
The water washing I in the table below refers to a water washing treatment in which water is replaced by passing through an adsorbent particle layer filled with a real liquid and adsorbed with high concentration boron.
The term “alkali” means that the adsorbent after the washing I is passed through an alkali solution (aqueous sodium hydroxide solution) having a pH of 13 or more to desorb boron.
Washing II refers to washing and washing of the adsorbent particles after boron is desorbed with an alkaline solution having a pH of 13 or higher.
B is boron.
The aqueous salt solution is an aqueous solution of alkaline earth metal salt or ammonium salt. In the examples, as shown in the figure, aqueous solutions of calcium chloride and magnesium chloride were used.

2. Details of experiment The column uses one tower (resin amount: 15 ml) and the resin is READ-B.
(1) Preparation: Creation of a saturated adsorption column A solution having a B concentration of 200 mg / l and pH = 7 was passed through the column at 3 l / hr, and the time when the outlet concentration reached 200 mg / l was regarded as saturation of adsorption. The test is performed using this saturated adsorption column.
(2) Experiment: Investigation of influencing factors Add factors considered to affect B concentration 200mg / l such as alkali metal salt, alkaline earth metal salt or ammonium salt, regenerate and pass water, The behavior was confirmed.
The regeneration conditions are as shown in Table 1, and sampling was performed in a test tube every 10 min.
As a method of adding the above factors, (a) a method of passing an aqueous solution of the above-mentioned salts while washing with water at the stage of washing II in the regeneration step, and (b) a regeneration step comprising washing I, alkali treatment, and washing II. Two methods of passing the aqueous solution of the above-mentioned salts after completion were adopted.
After completion of the regeneration step and passage of the aqueous salt solution, the actual solution (B concentration 200 mg / l, pH = 7) was passed through.

3. Result In FIGS. 1-4, a vertical axis | shaft shows the boron content in the liquid discharged | emitted from a column (logarithmic scale), and a horizontal axis shows a water flow rate. The water flow magnification up to 0 represents the regeneration process. In FIGS. 1 and 2, a salt aqueous solution was passed during the water washing II step, and in FIGS. 3 and 4, a salt aqueous solution was passed after the regeneration step was completed.
The boron concentration increased after the alkali treatment, which indicates that boron desorbed from the adsorbent by the alkali treatment was discharged from the column.
In the case of the above (a), as shown in FIGS. 1 and 2, when the time until the boron elution amount falls below 10 mg / l of the emission standard, when potassium chloride or sodium chloride is added, Compared to the case where some salts are not added, the time shortening effect is not seen. On the other hand, when calcium chloride was added, the time shortening effect was confirmed. From the above, it was found that calcium chloride stopped boron elution relatively quickly, and the elution amount could be made 10 mg / l or less, which is the emission standard value.

In the case of (b) above, as shown in FIGS. 3 to 4, when the time until the boron elution amount falls below 10 mg / l of the emission standard, when hydrochloric acid is added, the conventional salt is added. There is no time reduction effect compared to the case without it. On the other hand, when calcium chloride or magnesium chloride was added, the time shortening effect was confirmed. From the above, it has been found that in addition to calcium chloride, magnesium chloride can also stop boron elution relatively quickly, and the elution amount can be reduced to 10 mg / l or less, which is the emission standard value. In addition, as for calcium chloride, it was also found that a larger amount added has a time shortening effect.
Further, FIGS. 5 to 6 show changes in pH of the post-regeneration boron adsorbent regenerated by the methods (a) and (b). It can be seen that when calcium chloride or magnesium chloride is added to the water solution, the pH approaches the neutral range at an early stage of the water flow rate, that is, in a short time.

  As shown in the examples above, according to the regeneration method of the present invention, regeneration of a boron adsorbent containing high concentration boron can be recovered in a short time without substantially reducing the original boron adsorption capacity, Moreover, during the treatment, the boron adsorbent can be regenerated without the boron leaking beyond the standard in the waste water.

  The regeneration method of the present invention can be used for removing boron in wastewater such as industrial wastewater containing boron, waste incineration smoke washing wastewater, and geothermal power generation wastewater.

FIG. 5 is a diagram showing the relationship between the flow rate (water flow rate) and the boron elution amount when a salt aqueous solution is passed while performing water washing II in the boron adsorbent regeneration step. FIG. 2 is an enlarged view of the initial stage of FIG. 1. FIG. 5 is a graph showing the relationship between the rate of passing (water passing) and the amount of boron eluted when an aqueous salt solution is passed after the completion of the boron adsorbent regeneration step. FIG. 4 is an enlarged view of the initial stage of FIG. 3. These are the relational figures of the passage time (water flow) magnification time-dependent change and pH change at the time of passing aqueous salt solution, performing the water washing II of the boron adsorbent regeneration process. These are the relationship diagrams of the passage time (water passage) magnification time-dependent change and pH change at the time of passing salt aqueous solution after completion | finish of the adsorption agent reproduction | regeneration process for boron. These are sectional drawings of a mixed particle body of the rare earth compound of the present invention and a resin.

Claims (6)

A boron adsorbent containing a used rare earth element hydroxide and / or hydrated oxide is brought into contact with an alkaline aqueous solution, boron is desorbed to a predetermined concentration range, and then from one or more of alkaline earth metal salts. A method for regenerating a boron adsorbent, comprising contacting with an aqueous solution of the compound. The method for regenerating a boron adsorbent according to claim 1, wherein the concentration range is 10 to 1000 mg / l. Reproducing method according to claim 1 or 2 boron adsorbent, characterized in that the alkaline earth metal salt is magnesium chloride. The boron adsorbent is an aggregate of rare earth element hydroxides and / or hydrated oxides having an average secondary particle diameter of 0.2 to 25 microns, and a layer having a high polymer concentration on the surface of the granules The method for regenerating a boron adsorbent according to any one of claims 1 to 3, wherein: After passing an alkaline aqueous solution into a boron adsorbent-filled container having a boron adsorbent containing a used rare earth element hydroxide and / or a hydrous oxide, a compound comprising at least one alkaline earth metal salt is added. A method for regenerating a boron adsorbent, wherein the boron-containing liquid is passed at a water magnification ratio of 15 times or less so that the boron concentration per volume of the contained water is 10 mg / l or less. The method for regenerating a boron adsorbent according to any one of claims 1 to 5 , wherein the boron-containing agent is for wastewater treatment.

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