JP6332412B2 - Regeneration method of multi-layer anion exchange tower - Google Patents

Description

  The present invention comprises a weakly basic anion exchange resin layer and a strongly basic anion exchange resin layer, and the water to be treated is passed through the weakly basic anion exchange resin layer to the strongly basic anion exchange resin layer in this order. The present invention also relates to a method for regenerating a multilayer anion exchange column.

Anion exchange resins used for the production of pure water and the like are strongly basic anion exchange resins (hereinafter "SA") for adsorbing and removing some strong acid components and weak acid components such as silica, boron and carbonic acid. And a weakly basic anion exchange resin (hereinafter sometimes abbreviated as “WA”) for adsorbing and removing strong acid components such as sulfate ions and chloride ions. Broadly divided.
SA and WA differ in the holding power of the adsorbed ions depending on the nature of the ion exchange group in the structure. SA has a strong holding power and WA has a low holding power.

As anion exchange towers, there are a single-layer system using a tower equipped with only SA and a multi-layer system using a tower equipped with both WA and SA resins. Of these, the multi-layer anion exchange tower first passes the water to be treated (treated water after being passed through the cation exchange tower) through the WA layer and then through the SA layer. It is a watering device.
As the multi-layer type anion exchange tower, there are a two-column system in which WA and SA are packed in separate towers, and a single-column system in which the same tower is packed so that WA and SA are layered. is there. In the case of a single tower type, the WA layer and the SA layer are usually partitioned by a water-permeable partition plate.

  After collecting pure water with such a multi-layer type anion exchange tower, regeneration is performed. At that time, the SA layer is not adsorbed by weak acid components such as silica, boron, carbonic acid and the WA layer. A strong acid component leaked from a part of the WA layer is adsorbed on the surface. Also, most of the strong acid load is adsorbed on the WA layer.

The multi-layered anion exchange tower is usually regenerated by passing a sodium hydroxide (NaOH) aqueous solution as a regenerant in the order of SA layer → WA layer. This is due to the following reason.
That is, the holding power of the adsorbed ions is different between SA and WA, but the regeneration efficiency differs depending on the strength of the holding power, and WA having a weak holding power is regenerated with a small amount of regenerant. The regenerant is passed through in order, and the regenerant not used in the SA layer is used in the WA layer.

  When regenerating SA, a regenerant heated to 40 to 50 ° C. is often used in order to increase the desorption rate of silica adsorbed on the resin. At this time, the regeneration waste liquid of the SA layer contains a high concentration of silica. However, when the WA layer is regenerated using a regeneration waste liquid containing silica at a high concentration, gelation of silica occurs in the WA layer (Non-patent Document 1). This is because when the WA is regenerated, the strong acid component that has been adsorbed is desorbed, whereby the pH of the regenerated solution is drastically lowered and the solubility of silica is lowered.

As a method for preventing gelation of silica, there is a method in which the concentration of desorbed silica is changed by adjusting the sodium hydroxide concentration of the regenerant during regeneration (Patent Document 1). However, in this method, even a 1% NaOH aqueous solution, which is said to have a low concentration, has a silica solubility of about 7.5 g-SiO ₂ / L. Is drastically reduced and the silica is gelled.

  There is also known a method of changing the concentration of desorbed silica by gradually increasing the temperature of the regenerant from a low temperature. However, even if the silica concentration can be reduced by this method, strong acid can be removed in the WA layer. Separation cannot be controlled, and there is no change in causing gelation. In addition, the timing for changing the temperature is not clear, and if the timing is late, there is a risk that the reproduction is insufficient and potentially a reproduction failure is caused. Furthermore, the amount of pure water used for regeneration increases, which is not economical.

Japanese Patent Publication No.46-33926 Japanese Patent No. 3150836

Diaion Manual (4th revised edition), 78-79, February 26, 2010, Mitsubishi Chemical Corporation

  This invention is made | formed in view of the said situation, and makes it a subject to suppress the gelatinization of the silica at the time of reproducing | regenerating a multilayer type anion exchange tower, and to perform efficient reproduction | regeneration.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention can prevent gelation of silica in the WA layer by performing the predetermined first regeneration step and second regeneration step. I found it.
The present invention has been achieved based on such findings, and the gist thereof is as follows.

[1] A weakly basic anion exchange resin layer and a strongly basic anion exchange resin layer are provided, and water to be treated is passed from the weakly basic anion exchange resin layer to the strongly basic anion exchange resin layer in this order. In the method for regenerating the weakly basic anion exchange resin and the strongly basic anion exchange resin by passing a regenerant through a multilayer anion exchange column, (a) the regenerant is the multilayer anion. introduced from between the weakly basic anion exchange resin layer and the strongly basic anion exchange resin layer of the exchange column, step to flow out from the tower is passed through a weakly basic anion exchange resin layer, or (b) A regenerant is introduced from the strong base anion exchange resin layer side of the multilayer anion exchange column and passed through the strong base anion exchange resin layer to the weak base anion exchange resin layer in this order. The step of letting out the water from the column becomes alkaline with a pH of the tower effluent of pH 9 or higher. A first regeneration step that continues until the second regeneration step, in which after the first regeneration step, the strongly basic anion exchange resin layer is regenerated by immersing it in a regenerant at 5 ° C. or higher and lower than 35 ° C. for 20 minutes or longer. And a method for regenerating a multi-layered anion exchange column.

[ 2 ] A weakly basic anion exchange resin layer and a strongly basic anion exchange resin layer are provided, and water to be treated is passed through the weakly basic anion exchange resin layer to the strongly basic anion exchange resin layer in this order. In the method for regenerating the weakly basic anion exchange resin and the strongly basic anion exchange resin by passing a regenerant through a multilayer anion exchange column, (a) the regenerant is the multilayer anion. introduced from between the exchange column of weakly basic anion exchange resin layer and the strongly basic anion exchange resin layer, the step of flowing out the tower is passed through a weakly basic anion exchange resin layer, column effluent A first regeneration step that continues until the pH of the aqueous solution becomes alkaline of pH 9 or higher, and a second regeneration by immersing the strongly basic anion exchange resin layer in a regenerant of 5 ° C. or higher and lower than 35 ° C. for 20 minutes or longer . In the regeneration method of the multilayer anion exchange tower that performs the regeneration process Thus, the first regeneration step and the second regeneration step are performed simultaneously, and in the second regeneration step, the regenerant used for the regeneration of the strong base anion exchange resin layer is used as the weak base anion exchange resin. A method for regenerating a multi-layer anion exchange column, wherein the multi-layer anion exchange column is discharged without passing through the layer.

[3] Oite to [1] or [2], wherein the strongly basic anion exchange resin in the regenerant multilayer type anion exchange column in which liquid passing the adsorption of silica, holds, the weak A method for regenerating a multilayer anion exchange column, wherein the basic anion exchange resin adsorbs and retains a strong acid.

[ 4 ] In any one of [1] to [ 3 ], the temperature when the water to be treated is passed is maintained in the range of 5 to 20 ° C. prior to the first regeneration step. Regeneration method of anion exchange tower.

  According to the present invention, it is possible to suppress the gelation of silica at the time of regenerating the multi-layered anion exchange tower and perform efficient regeneration.

4 is a graph showing changes in Cl ion concentration, ionic silica concentration, colloidal silica concentration, and pH with time of a regeneration waste liquid in Experimental Example 1.

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

[Multi-layer anion exchange tower]
In the present invention, a multilayer anion exchange tower for regeneration comprises a weakly basic anion exchange resin (WA) layer and a strongly basic anion exchange resin (SA) layer. The single-column type in which the layers are provided in one tower may be used, or the double-column type in which WA and SA are packed in different towers may be used.

  In the case of collecting water by passing water to be treated through such a multi-layer anion exchange tower, the water to be treated is passed in the order of WA layer to SA layer.

  In the present invention, by passing the water to be treated in this way, the strong acid component is adsorbed and retained in the WA layer, and the SA layer can be removed by the weak acid component such as silica, boron, carbonic acid and the WA layer. The multi-layer anion exchange tower that adsorbs and holds the strong acid component that has flowed into the SA layer instead is regenerated.

  In the present invention, the multilayer anion exchange column is regenerated in a regeneration step comprising a first regeneration step and a second regeneration step, which will be described later, and after the regeneration step, pure water is supplied in the same direction as the flow direction of the regenerant. An extrusion cleaning process for passing liquid is performed. Extrusion washing is performed until the pH of the column effluent during extrusion washing reaches about 10-12. If necessary, after the extrusion washing process, in order to increase the purity of the tower effluent and start sampling, the water to be treated and pure water are washed in the same direction as the water flow direction during sampling. For the purpose of reducing washing waste liquid, the tower effluent is treated with a cation exchange tower and a decarboxylation tower, and then circulated and passed to obtain a tower effluent with a desired purity. A series of processes for regeneration is completed, and water sampling, that is, production of pure water is resumed.

Prior to the regeneration of the multi-layer anion exchange tower according to the present invention, the water to be treated is set to a low temperature of 5 to 20 ° C., preferably 5 to 15 ° C. at the time of sampling, and is passed through the multi-layer anion exchange tower. Thus, it is preferable to carry out the step of maintaining the inside of the multilayer anion exchange column at such a low temperature. This is due to the following reason.
Since the silica adsorbed on SA is more easily polymerized at higher temperatures, the water sampling step is performed at such a low temperature to suppress the polymerization of silica in the multi-layer anion exchange tower, and the silica in the regeneration step Increases detachability and enables efficient regeneration. For this reason, when the temperature of to-be-processed water is high, it is preferable to lower the temperature of to-be-processed water to the said range, and to flow through a multilayer anion exchange tower.

[Regeneration process]
<Regenerant>
For the regeneration of WA and SA, an aqueous solution of sodium hydroxide (NaOH) is used as a regenerant.
The NaOH aqueous solution that is a regenerative agent preferably has a NaOH concentration of 0.5 to 5.0% by weight (usually pH 13 or more) from the viewpoint of regeneration efficiency. If the NaOH concentration is lower than the above upper limit, it is inefficient because OH ions having a small selection coefficient are exchanged with OH ions having a small selection coefficient as a regenerative agent, and even if it is high, the speed increases from the viewpoint of penetration into the resin. There is no inefficiency.

<Flow direction>
Although there is no restriction | limiting in particular in the liquid flow direction at the time of flowing a regenerant, It is preferable to set it as the reverse direction to the water flow direction (water flow direction at the time of sampling) of to-be-processed water.
In normal cases, the water flow direction at the time of sampling is often a downward flow, and therefore the liquid flow direction at the time of regeneration is preferably an upward flow. The liquid passing direction at the time of the above-described extrusion cleaning is preferably the same as the liquid passing direction of the regenerant.

<Temperature>
The temperature of the regenerant is as follows.
The temperature of the regenerant that is passed through only the WA layer may be 5 ° C. or more and 55 ° C. or less, which is a range heated from room temperature, and is usually 5 ° C. or more and less than 35 ° C. (water temperature in cold regions or summer). ), Preferably 20 ° C. or higher and 30 ° C. or lower. Further, the temperature of the regenerant that is passed through only the SA layer may be 5 ° C. or higher and 55 ° C. or lower, which is a range warmed from normal temperature, and is usually preferably 35 ° C. or higher and 55 ° C. or lower when heated. Most preferably, it is at least 45 ° C. Furthermore, the regenerant that is continuously passed from the SA layer to the WA layer is preferably 5 ° C. or higher and 55 ° C. or lower. However, when the immersion process described below is performed on the SA layer, a regenerant at room temperature (5 ° C. or more and less than 35 ° C., preferably 20 ° C. or more and 30 ° C. or less) is used by setting the immersion time to 30 minutes or more. Can do.

<Flow rate>
The flow rate of the regenerant is preferably set to the following amount based on the load of the multilayer anion exchange tower to be regenerated or the pH of the tower effluent (regeneration waste liquid).
That is, the flow rate of the regenerant is such that the molar ratio of NaOH passed is 100% or more, preferably 110 to 135%, with respect to the design load (the amount of ions to be desorbed) of the multilayer anion exchange tower to be regenerated. It is preferable that the amount is as follows.
The NaOH molar ratio with respect to the design load may be set for the overall design load of the WA layer and the SA layer, or may be set for the design load of each layer individually. Also, the actual operational load may be analyzed and set for this value.

  Alternatively, the flow rate of the regenerant is, when only the SA layer is passed, the pH of the tower effluent (regeneration waste liquid) that has passed only the SA layer is 9 or more, preferably 10 or more, more preferably 13 or more. It is preferable to make such an amount. In addition, when water is passed through only the WA layer, the amount of the tower effluent (recycled waste liquid) that has passed through the WA layer is adjusted to 9 or more, preferably 10 or more, more preferably 13 or more. preferable. In addition, when the regenerant is continuously passed through the SA layer and the WA layer, the tower effluent (regeneration discharged from the WA layer) passes through the SA layer → WA layer and is discharged from the WA layer side. The pH of the waste liquid is preferably 9 or more, preferably 10-13.

<Immersion process>
In the present invention, after the regenerant is passed, an immersion step may be performed in which the flow is stopped and held for a predetermined time.

  In this case, it is preferable that the timing of starting the immersion is the time when the flow rate of the regenerant reaches the aforementioned amount.

  The soaking temperature (the temperature of the regenerant held in the tower in the soaking step) varies depending on the soaking time, but is usually from 5 ° C. to 55 ° C., preferably normal temperature (5 ° C. to less than 35 ° C., preferably 20 ° C. ° C to 30 ° C). The dipping step is usually 20 minutes or longer, preferably about 30 to 120 minutes. When the immersion temperature is high within the above temperature and time range, the immersion time is preferably shortened, and when the immersion temperature is low, the immersion time is preferably increased.

  By performing such an immersion step, it is possible to promote desorption of silica or the like adsorbed on SA, or a strong acid component adsorbed on WA.

<Playback operation>
Hereinafter, a specific reproduction operation in the present invention will be described.
In the present invention, (a) a step of introducing the regenerant from between the WA layer and the SA layer of the multi-layered anion exchange tower and allowing only the WA layer to pass through, or (b) a regenerant The step of introducing from the SA layer side of the multi-layered anion exchange tower and passing it through the SA layer to the WA layer in order is carried out, and the pH of the tower effluent is alkaline, preferably pH 9 or higher, more preferably pH 10 or higher. A first regeneration process that continues until the first regeneration process is performed, and a second regeneration process that regenerates the SA layer after the first regeneration process is performed.

Examples of the method for regenerating the SA layer in the second regeneration step include the following methods.
(i) The regenerant is introduced from between the WA layer and the SA layer of the multi-layered anion exchange tower, and only the SA layer is allowed to flow out from the SA layer side of the tower, or the regenerant is multi-layered. It introduce | transduces from the SA layer side of an anion exchange column, and it is made to flow out between between the SA layer and WA layer of a column.
(ii) The regenerant is introduced from the SA layer side of the multi-layered anion exchange column, passed through the SA layer and the WA layer in this order, and then flows out from the WA layer side of the column.
(iii) A regenerant is introduced from the SA layer side of the multi-layered anion exchange tower to regenerate the SA layer by immersion.

When the regenerant is passed through only the SA layer and the regenerant used to regenerate the SA layer is discharged outside the tower without passing through the WA layer as in (i) above, the first regeneration step is performed. By adopting the step (a), the first regeneration step and the second regeneration step can be performed simultaneously.
Such regeneration of only the SA layer and regeneration of only the WA layer are performed using a multi-layer anion exchange tower provided with a regenerant introduction pipe and a regeneration waste liquid discharge pipe between the WA layer and the SA layer. be able to.

In the present invention, in the first regeneration step, the regenerant is passed through until the pH of the column effluent becomes alkaline, preferably pH 9 or more, more preferably pH 10 or more, and then the SA layer is regenerated, so that WA Silica gelation in the layer can be prevented.
That is, whether it is step (a) or step (b), the pH of the tower effluent that has passed through the WA layer is alkaline, preferably pH 9 or higher, more preferably pH 10 or higher. This means that the strong acid component adsorbed on the WA layer has been completely desorbed and removed. Therefore, in the first regeneration step, the strong acid component in the WA layer is completely removed, and then the SA layer is regenerated, so that the regeneration waste liquid containing silica eluted from the SA layer in the regeneration of the SA layer Even if it passes, the pH of the regenerated waste liquid does not drop while passing through the WA layer, and silica gelation and precipitation do not occur.

Specific operation procedures of the regeneration step in the present invention include the following (1) to (6).
(1) After performing the first regeneration step of passing the regenerant through only the WA layer of (a), the second regeneration step of passing the regenerant through only the SA layer is performed.
(2) The first regeneration step in which the regenerant is passed through only the WA layer in (a) and the second regeneration step in which the regenerant is passed through only the SA layer are simultaneously performed.
(3) After performing the first regeneration step in which the regenerant is passed through only the WA layer in (a), the second regeneration step in which the regenerant is passed through from the SA layer to the WA layer is performed.
(4) After performing the first regeneration step in which the regenerant is passed through only the WA layer of (a), the regenerative agent is introduced into the tower from the SA layer side and retained for a predetermined time. 2 Perform the regeneration process. In this case, if the multi-layered anion exchange tower is a single tower type, the regenerant is introduced into the tower from the SA layer side, and the entire SA layer and WA layer are immersed in the regenerator. If the multi-layer type anion exchange tower is a double tower type, only the SA layer can be dipped and regenerated.
(5) After performing the first regeneration step of passing the regenerant in the order of SA layer → WA layer in (a), the second regeneration step of passing the regenerant through the SA layer → WA layer is performed.
(6) After performing the first regeneration step in which the regenerant is passed in the order of SA layer → WA layer in (a), the second regeneration step is performed by immersion regeneration that retains the regenerant for a predetermined time. This regeneration step (a) is usually employed when the multi-layered anion exchange tower is of a single tower type.

When the SA layer is regenerated in the second regeneration step, it is preferable to use a regenerated agent that has been heated to 35 ° C. or more and 55 ° C. or less as described above. This is because if the regenerator is heated, NaOH can quickly diffuse into the resin and silica can be effectively eluted.
The regenerant used in the first regeneration step may be warmed or warmed, whether it is passed through the WA layer alone or from the SA layer to the WA layer. Or higher and lower than 35 ° C, preferably 20 ° C or higher and 30 ° C or lower).

  When immersion regeneration of the SA layer is performed in the second regeneration step, the immersion temperature (the temperature of the regenerant retained in the tower in the immersion step) varies depending on the immersion time, but is usually 5 ° C. or more and 55 ° C. or less, preferably It is normal temperature (5 degreeC or more and less than 35 degreeC, Preferably it is 20 degreeC or more and 30 degrees C or less). The dipping step is usually 20 minutes or longer, preferably about 30 to 120 minutes. When the immersion temperature is high within the above temperature and time range, the immersion time is preferably shortened, and when the immersion temperature is low, the immersion time is preferably increased.

  In the case of immersion regeneration, by setting the immersion time to 30 minutes or longer, a regenerant at room temperature (5 ° C. or higher and lower than 35 ° C., preferably 20 ° C. or higher and 30 ° C. or lower) can be used. That is, in the case of immersion regeneration, since NaOH can be diffused in the resin without depending on the temperature of the regenerant, a regenerant at room temperature (5 ° C. or more and less than 35 ° C., preferably 20 ° C. or more and 30 ° C. or less) is used. be able to. Silica is polymerized and adsorbed inside the SA resin, but immersion regeneration also has an effect of ensuring a reaction time for decomposing and eluting the polymer of silica.

Hereinafter, the present invention will be described more specifically with reference to examples.
In the following experimental examples, examples and comparative examples, the followings were used as the strong basic anion exchange resin and the weak basic anion exchange resin.
Strongly basic anion exchange resin (SA): “Diaion SA10ALOH” manufactured by Mitsubishi Chemical Corporation
Weakly basic anion exchange resin (WA): “Diaion WA30C” manufactured by Mitsubishi Chemical Corporation

Further, “silica elution rate” was defined as follows, and this was used as an index to evaluate the regeneration efficiency. A silica elution rate of less than 100% indicates that silica gelation is occurring. The upper limit of the elution rate of silica is theoretically 100%. However, in the case of a resin that has been repeatedly sampled, there may be a case where it exceeds 100% due to the residual silica load during the previous regeneration.
Elution rate of silica (%) = (total amount of silica in the regenerated waste liquid from the column / total amount of silica loading of feed water) × 100
Total amount of silica in the reclaimed waste liquid = average silica concentration in the reclaimed waste liquid x amount of reclaimed waste liquid Total amount of silica in the feed water = silica concentration in the feed water x feed water flow rate x feed time The analysis of silica is performed according to JIS as follows: It was.
Ionic silica: JIS 44.1.2 Molybdenum blue method All silica: JIS 44.3
Gel silica: (total silica analysis value according to JIS 44.3)-(ionic silica analysis value according to JIS 44.1.2)

In addition, liquid flow and water flow through the column (φ40 mm acrylic column) were performed under the following common conditions, resin amount, supply water temperature, and ion concentration according to the purpose.
Feed water flow: LV = 40 m / hr water regenerative agent flow: Reverse direction of feed water flow, LV = 10 m / hr water reflow agent The amount was determined so as to be 110% in terms of molar ratio with respect to the total amount of loaded ions.

[Experimental Example 1]
One of the two columns was filled with SA so that the resin layer height was 500 mm, and the other was filled with WA so that the resin layer height was 500 mm. This column is connected in series, and in the order of WA column → SA column, feed water having a chloride ion concentration of 80 mg / L and a silica concentration of 43 mg / L becomes 15 g-SiO ₂ / LR (SA) per liter of resin. The water passed through.
As a regenerant, 45 ° C. and 2 wt% NaOH aqueous solution (pH 13 or more) were used, and the solution was passed in the order of SA layer → WA layer.
Changes in the Cl ion concentration, ionic silica concentration, colloidal silica concentration, and pH of the tower effluent (recycled waste liquid) discharged from the WA packed column were examined, and the results are shown in FIG.
As is clear from FIG. 1, while Cl ions are being discharged (contained in the regenerated waste liquid), the pH is low and silica is not discharged (period shown by the arrow in FIG. 1).
Thereafter, ionic silica is discharged.
As shown in FIG. 1, since the silica is discharged in an ionic state under a condition that exceeds pH 9, preferably pH 10, the column effluent of the anion exchange tower is regenerated under a condition that exceeds pH 9, preferably pH 10. It can be seen that silica does not gel even if it flows into this WA layer.

[Example 1]
One of the two columns was filled with SA so that the resin layer height was 500 mm, and the other was filled with WA so that the resin layer height was 500 mm. This column is connected in series, and in the order of WA column → SA column, feed water having a chloride ion concentration of 80 mg / L and a silica concentration of 43 mg / L becomes 15 g-SiO ₂ / LR (SA) per liter of resin. The water passed through.
As the regenerant, normal temperature (25 ° C.) and an aqueous NaOH solution having a NaOH concentration of 1 wt% were used. The tower effluent was discharged out of the system. Thereafter, the regenerant was heated (45 ° C.), and the regeneration was conducted by continuously passing the column effluent until the pH reached 14 in the order of the SA column → WA column, followed by extrusion with pure water alone.
After repeating the water flow and regeneration of the above feed water 5 times, the elution rate of the sixth silica was calculated and found to be 110%.

[Comparative Example 1]
In Example 1, regeneration was performed by continuously passing in the order of the SA column → WA column without performing prior regeneration of the WA column, and then extrusion was performed only with pure water. After repeating the above-mentioned feed water flow and regeneration 5 times, the elution rate of the sixth silica was calculated and found to be 97%.

  From the results of Example 1 and Comparative Example 1 above, it can be seen that by performing the preceding regeneration of the WA layer, the silica can be prevented from gelling and efficiently regenerated by eluting the silica.

[Example 2]
One of the two columns was filled with SA so that the resin layer height was 500 mm, and the other was filled with WA so that the resin layer height was 500 mm. This column is connected in series, and in the order of WA column → SA column, feed water having a chloride ion concentration of 80 mg / L and a silica concentration of 43 mg / L becomes 15 g-SiO ₂ / LR (SA) per liter of resin. The water passed through.
A NaOH aqueous solution having a NaOH concentration of 1% by weight was used as the regenerant, and the regenerant was added to each of the SA column and WA column so that the amount of ions loaded on each resin was 110%. Were individually passed until each became 14, and the tower effluent was discharged out of the system. Thereafter, extrusion with pure water alone was similarly performed. The regenerant was passed through the WA column at room temperature (25 ° C.) and through the SA column at warm (45 ° C.).
After repeating the above-mentioned feed water flow and regeneration 5 times, the elution rate of the sixth silica was calculated and found to be 105%.

  From this Example 2, it can be seen that by separately regenerating the SA layer and the WA layer, it is possible to regenerate by preventing silica gelation and efficiently eluting silica.

[Example 3]
Two columns were packed with SA so that the resin layer height was 500 mm. Through these two columns, feed water having a silica concentration of 43 mg / L was passed so as to be 15 g-SiO ₂ / L-R per liter of resin.
One column was regenerated by passing a NaOH aqueous solution (pH 14 or higher) having a temperature of 25 ° C. and a NaOH concentration of 1% by weight. After confirming that the pH of the tower effluent was 13, the solution was sealed for 30 minutes. . A predetermined amount of the remaining NaOH aqueous solution was passed through after the immersion process for 30 minutes, and extrusion was performed only with pure water after completion. After the feed water was passed and regenerated five times, the sixth elution rate of silica was calculated and found to be 103%.
Through the other column, the whole amount of NaOH aqueous solution having a temperature of 25 ° C. and a NaOH concentration of 1% by weight was passed through, and thereafter, regeneration was performed by extruding only with pure water. The pH of the tower effluent during regeneration was 13. Thereafter, the elution rate of silica was calculated to be 85%.
From this result, it is understood that silica can be efficiently eluted from SA even by a NaOH aqueous solution at room temperature by performing the dipping process.

Claims (4)

A multi-layer system that includes a weakly basic anion exchange resin layer and a strongly basic anion exchange resin layer, and water to be treated is passed in the order of weakly basic anion exchange resin layer to strong basic anion exchange resin layer. In a method for regenerating the weakly basic anion exchange resin and the strongly basic anion exchange resin by passing a regenerant through an anion exchange tower,
(A) a regenerant is introduced from between the plurality bed anionic weakly basic anion exchange resin layer of the ion exchange column and a strongly basic anion exchange resin layer, it passes through the weakly basic anion exchange resin layer Or (b) a regenerant is introduced from the strong base anion exchange resin layer side of the multi-layer anion exchange column to weak base from the strong base anion exchange resin layer. A first regeneration step of continuing the step of passing through the order of the functional anion exchange resin layer and letting it flow out of the tower until the pH of the tower effluent becomes alkaline of pH 9 or higher ;
And a second regeneration step in which the strongly basic anion exchange resin layer is regenerated by immersing the strongly basic anion exchange resin layer in a regenerant having a temperature of 5 ° C. or higher and lower than 35 ° C. for 20 minutes or longer after the first regeneration step. A method for regenerating an anion exchanger. A multi-layer system that includes a weakly basic anion exchange resin layer and a strongly basic anion exchange resin layer, and water to be treated is passed in the order of weakly basic anion exchange resin layer to strong basic anion exchange resin layer. In a method for regenerating the weakly basic anion exchange resin and the strongly basic anion exchange resin by passing a regenerant through an anion exchange tower,
(A) a regenerant is introduced from between the plurality bed anionic weakly basic anion exchange resin layer of the ion exchange column and a strongly basic anion exchange resin layer, it passes through the weakly basic anion exchange resin layer A first regeneration step in which the step of allowing the column effluent to flow out from the column is continued until the pH of the column effluent becomes alkaline of pH 9 or higher ,
A method for regenerating a multi-layer anion exchange column, comprising performing a second regeneration step of regenerating the strongly basic anion exchange resin layer by immersing it in a regenerant having a temperature of 5 ° C or higher and lower than 35 ° C for 20 minutes or longer. ,
The first regeneration step and the second regeneration step are performed simultaneously, and in the second regeneration step, the regenerant used to regenerate the strongly basic anion exchange resin layer passes through the weakly basic anion exchange resin layer. A method for regenerating a multi-layer anion exchange column, wherein the multi-layer anion exchange column is discharged outside the multi-layer anion exchange column. In Claim 1 or 2 , the strongly basic anion exchange resin in the multilayer anion exchange tower through which the regenerant is passed adsorbs and holds silica, and the weakly basic anion exchange resin is A method for regenerating a multi-layer anion exchange column, characterized by adsorbing and holding a strong acid. The multilayer anion exchange according to any one of claims 1 to 3 , wherein the temperature when the treated water is passed is maintained in a range of 5 to 20 ° C prior to the first regeneration step. How to regenerate the tower.

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