JP2017213553A - Harmful ion removal method, harmful ion removal apparatus and harmful ion adsorbent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a harmful ion removal method and removal apparatus for drinking water, allowing for removal of a harmful ion and suppression of an increase in pH of the drinking water.SOLUTION: The harmful ion removal method for drinking water comprises: a step S1 of bringing water to be treated containing a harmful ion into contact with a hydrotalcite-like compound to remove the harmful ion in the water to be treated; and a step S2 of bringing the water to be treated having contacted with the hydrotalcite-like compound into contact with a pH adjustment member to adjust pH of the water to be treated having contacted with the hydrotalcite-like compound.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a method for removing harmful ions for drinking water, a harmful ion removing device, and a harmful ion adsorbing material.

  Conventionally, there has been a demand for safe water supply that does not cause health damage to the human body. Arsenic and fluorine are examples of harmful elements that cause health damage to the human body.

  However, depending on the region, the above-mentioned harmful elements are contained in the natural strata and may be eluted from the strata into the groundwater. In addition, when waste liquid containing the above harmful elements is generated due to development of a mine or the like, the harmful elements in the waste liquid may flow into the groundwater. Therefore, when such groundwater is used as drinking water, it is necessary to remove harmful elements in the water.

  Harmful elements arsenic and fluorine exist as anions in water. Therefore, a method of removing harmful elements for drinking water by adsorbing them on a material having anion adsorption characteristics can be considered. For example, Mg—Al based minerals such as hydrotalcite-like compounds are known as materials having excellent anion adsorption performance.

JP 2009-178682 A JP 2006-334456 A

  However, water in contact with the hydrotalcite-like compound has a problem that the pH increases. Such water with increased pH becomes alkaline and is not suitable for drinking water.

  An object of the present invention is to provide a method for removing harmful ions for drinking water, a harmful ion removing device, and a harmful ion adsorbing material capable of removing harmful ions and suppressing an increase in pH of drinking water. .

  The method for removing harmful ions for drinking water according to an embodiment includes the step of contacting the water to be treated containing harmful ions with a hydrotalcite-like compound to remove the harmful ions in the water to be treated, and the hydrotalcite And a step of bringing the water to be treated in contact with the like compound into contact with a pH adjuster to adjust the pH of the water to be treated in contact with the hydrotalcite-like compound.

  The harmful ion removing device for drinking water according to the embodiment includes a harmful ion removing unit that removes the harmful ions in the water to be treated by bringing the water to be treated and the hydrotalcite-like compound into contact with each other. A pH adjusting unit that adjusts the pH of the water to be treated in contact with the hydrotalcite-like compound by bringing the water to be treated in contact with the hydrotalcite-like compound in contact with the hydrotalcite-like compound.

  The harmful ion adsorbent for drinking water of the embodiment adjusts the pH of the hydrotalcite-like compound that adsorbs harmful ions in the water to be treated containing harmful ions, and the water to be treated that comes into contact with the hydrotalcite-like compound. The pH adjusting material to be mixed is mixed.

  It is possible to provide a harmful ion removal method, a harmful ion removal device, and a harmful ion adsorbent for drinking water that can remove harmful ions and suppress an increase in pH of drinking water.

It is a flowchart showing the harmful ion removal method for drinking water which concerns on 1st Embodiment. It is a figure which represents roughly the harmful ion removal apparatus for drinking water which concerns on 2nd Embodiment. It is sectional drawing which represents roughly the harmful ion removal tower and pH adjustment tower which comprise the harmful ion removal apparatus for drinking water which concerns on 2nd Embodiment. It is a figure which represents roughly the harmful ion removal apparatus for drinking water which concerns on 3rd Embodiment. It is a figure which represents roughly the harmful ion removal apparatus for drinking water which concerns on 4th Embodiment. It is a figure which represents roughly the harmful ion removal apparatus for drinking water which concerns on 5th Embodiment. It is a figure which represents roughly the harmful ion removal apparatus for drinking water which concerns on 6th Embodiment. It is a graph showing the relationship between the mass ratio of a hydrotalcite-like compound and metakaolin, and the pH of immersion liquid. It is a graph showing the relationship between the mass ratio of a hydrotalcite-like compound and aluminum silicate, and the pH of immersion liquid. It is a graph showing the relationship between the mass ratio of a hydrotalcite-like compound and a strongly acidic cation exchange resin, and the pH of immersion liquid. It is a graph showing the relationship between the accumulated washing water amount of the hydrotalcite-like compound and the pH of the immersion liquid. It is a graph showing the X-ray fluorescence (XRF) analysis result of the hydrotalcite-like compound immersed in NaCl aqueous solution. It is a graph showing the X-ray-diffraction (XRD) analysis result of the hydrotalcite-like compound obtained by the synthesis | combination. It is a graph showing the removal performance of arsenic in water by a hydrotalcite-like compound. It is a graph showing the removal performance of the fluorine in water by a hydrotalcite-like compound. It is a graph showing the relationship between the pH of the simulated treated water after passing and the passing time of the simulated treated water. It is a graph showing the relationship between the pH of the simulated treated water after immersion and the immersion time of the pH adjusting material.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

(First embodiment)
As shown in FIG. 1, the harmful ion removal method according to the first embodiment includes a step S1 of removing harmful ions in the treatment target water by bringing the treatment target water containing the harmful ions into contact with the hydrotalcite-like compound. The process target water that has contacted the hydrotalcite-like compound is brought into contact with the pH adjuster to adjust the pH of the process target water that has contacted the hydrotalcite-like compound.

  The water to be treated in the present embodiment contains harmful elements that cause health damage to the human body as ions. The treatment target water treated by the harmful ion removal method of this embodiment is used as drinking water. Examples of harmful elements include, but are not limited to, arsenic, fluorine, nitric acid, sulfuric acid, boric acid, selenium, and the like. The harmful element contained in the water to be treated may be one type or two or more types. Especially, in the harmful ion removal method of this embodiment, a great effect can be obtained when the water to be treated contains arsenic and fluorine as harmful elements.

  In the harmful ion removal method of the present embodiment, water to be treated containing ions (harmful ions) composed of harmful elements as described above is brought into contact with the hydrotalcite-like compound (S1). Thereby, harmful ions in the water to be treated are adsorbed and removed by the hydrotalcite-like compound.

  The hydrotalcite-like compound has a layered structure in which a base material containing Mg and Al is used as a layer, and can take in and adsorb an anion between the layers. In addition to Mg and Al, the hydrotalcite-like compound may contain an alkali metal or an alkaline earth metal such as calcium (Ca) as impurities. When the hydrotalcite-like compound is brought into contact with the water to be treated, impurities such as Ca ions contained in the hydrotalcite-like compound are leached into the water to be treated, thereby increasing the pH of the water to be treated.

  Therefore, in the harmful ion removal method of this embodiment, the water to be treated that has contacted the hydrotalcite-like compound is brought into contact with the pH adjuster. By bringing the water to be treated into contact with the pH adjuster, the impurity ions leached into the water to be treated are removed. For this reason, the raise of pH of process target water can be suppressed and it can adjust to pH suitable for drinking.

  The pH adjusting material has cation adsorption performance. The pH adjuster adsorbs a cation such as Ca that is leached from the hydrotalcite-like compound, thereby suppressing an increase in pH of the water to be treated that has come into contact with the hydrotalcite-like compound. Examples of the pH adjusting material include a cation exchange resin, metakaolin, and aluminum silicate, but are not limited thereto. A pH adjuster may be used individually by 1 type, and may use 2 or more types together.

  In the harmful ion removal method for drinking water of this embodiment, it is preferable to further comprise a step of washing the hydrotalcite-like compound with water before bringing the hydrotalcite-like compound into contact with the water to be treated. By washing the hydrotalcite-like compound with water as washing water, impurities that raise the pH of the water can be eluted and removed in the washing water. Thereby, the raise inhibitory effect of the water for process made to contact with a hydrotalcite-like compound can be improved.

  In the harmful ion removal method for drinking water of the present embodiment, the method further comprises the step of adsorbing anions on the hydrotalcite-like compound before the step of bringing the hydrotalcite-like compound into contact with the water to be treated. Good.

  Here, the hydrotalcite-like compound has a property of exhibiting pH buffering properties when immersed in water. When the hydrotalcite-like compound is immersed in water, Mg and Al constituting the base material of the hydrotalcite-like compound are dissolved into water as cations, and the eluted cations of Mg and Al are in the base material. The phenomenon of precipitation occurs simultaneously. Similarly, for ions existing between layers of a hydrotalcite-like compound (hereinafter referred to as interlayer ions), elution into water and precipitation between layers occur simultaneously. Since elution and precipitation of cations and interlayer ions derived from the substrate are balanced, the hydrotalcite-like compound exhibits pH buffering properties when immersed in water. The pH buffer range varies depending on the type of interlayer ions of the hydrotalcite-like compound.

In other words, by adsorbing anions between the layers of the hydrotalcite-like compound, the elution and precipitation of the cations derived from the base material and the anions between the layers are balanced, so the water to be treated that has come into contact with the hydrotalcite-like compound An increase in pH can be suppressed. Hereinafter, the anion artificially adsorbed between the layers of the hydrotalcite-like compound is referred to as an exchange anion. The exchange anion is, for example, chloride ion (Cl ⁻ ), but is not limited thereto.

As a method of adsorbing the exchange anion on the hydrotalcite-like compound, a method of immersing the hydrotalcite-like compound in an aqueous solution in which the exchange anion is dissolved, or contacting the hydrotalcite-like compound with a gas that generates the exchange anion There are methods. Replacement anions Cl ^- in the case of the sodium chloride or a method of immersing the aqueous hydrotalcite-like compounds (NaCl), in a manner of contacting the hydrotalcite-like compound in chlorine gas, hydrotalcite-like compound Cl ⁻ can be adsorbed between these layers.

The hydrotalcite-like compound may be a naturally occurring mineral or may be obtained by synthesis. When synthesizing a hydrotalcite-like compound, a hydrotalcite-like compound can be obtained as a precipitate by mixing a mixed metal salt aqueous solution of magnesium salt and aluminum salt and an alkaline aqueous solution. Specifically, a hydrotalcite-like compound precipitate is obtained by mixing and stirring a sodium hydroxide (NaOH) aqueous solution in a mixed metal salt aqueous solution of magnesium chloride (MgCl ₂ ) and aluminum chloride (AlCl ₃ ). be able to. At this time, the NaOH aqueous solution is added, for example, so that the pH of the aqueous solution after the addition is about 10. As described above, by using the hydrotalcite-like compound synthesized from the chlorides of Mg and Al, the same effect as that obtained when Cl ⁻ is adsorbed between the above-described layers can be obtained. For this reason, the increase suppression effect of pH of process target water can be improved.

  Moreover, in the harmful ion removal method for drinking water of this embodiment, the composition (Mg / Al molar ratio) of the hydrotalcite-like compound is adjusted before the step of bringing the hydrotalcite-like compound into contact with the water to be treated. You may further comprise the process to do. The pH buffer region of the hydrotalcite-like compound described above also varies depending on the ratio of Mg and Al constituting the hydrotalcite-like compound. Therefore, by adjusting the composition (Mg / Al molar ratio) of the hydrotalcite-like compound that is brought into contact with the water to be treated, the pH of the water to be treated that has come into contact with the hydrotalcite-like compound can be appropriately adjusted. When adjusting the composition of the hydrotalcite-like compound, the composition of the hydrotalcite-like compound is adjusted to 2 to 4 in terms of a molar ratio expressed by Mg / Al, in order to obtain an excellent pH increase inhibiting effect. Is preferred. The composition of the hydrotalcite-like compound can be adjusted by changing Mg / Al in the mixed metal salt aqueous solution when synthesizing the hydrotalcite-like compound.

  The hydrotalcite-like compound is preferably heat-treated before being brought into contact with the water to be treated. Hydrotalcite-like compounds tend to take up carbonate ions between layers. By performing the heat treatment of the hydrotalcite-like compound, the carbonate ions are released from the interlayer as carbon dioxide gas, whereby the anion adsorption performance of the hydrotalcite-like compound can be improved. The conditions for the heat treatment are, for example, about 500 ° C. for about 3 hours.

  The contact between the water to be treated and the hydrotalcite-like compound (step S1) may be performed continuously or batchwise. In the case of a continuous method, the hydrotalcite-like compound can be filled inside the column-type adsorption tower, and the water to be treated can be passed through the adsorption tower and brought into contact with the hydrotalcite-like compound. In the case of performing the batch process, the hydrotalcite-like compound is immersed in the water to be treated, and then subjected to solid-liquid separation, whereby the water to be treated from which harmful ions are removed can be obtained as a liquid phase. The liquid-solid ratio (treatment target water (mL) / hydrotalcite like compound (g)) when the hydrotalcite-like compound is immersed in the treatment target water is, for example, about 20 mL / g.

  The contact between the water to be treated and the pH adjuster (step S2) may be performed continuously or batchwise. In the case of performing continuously, the column-type adsorption tower is filled with a pH adjusting material, and the water to be treated is allowed to flow through the adsorption tower so that the water to be treated can be brought into contact with the pH adjusting material. When performing by a batch type, the pH adjustment material can be obtained as a liquid phase by immersing the pH adjusting material in the treatment target water and then performing solid-liquid separation. The liquid-solid ratio (processing target water (mL) / pH adjusting material (g)) at the time of immersing the pH adjusting material in the processing target water is, for example, about 20 mL / g.

  The step S1 of bringing the water to be treated into contact with the hydrotalcite-like compound and the step S2 of bringing the water to be treated into contact with the pH adjuster may be performed sequentially or simultaneously.

  When performing step S1 and step S2 at the same time, a pH adjuster is added to the hydrotalcite-like compound and then filled into a column-type adsorption tower or the like, and the water to be treated is brought into contact in the same manner as described above. Just do it. In this case, for example, after adding a pH adjuster to the hydrotalcite-like compound, they are mixed. The mixed hydrotalcite-like compound and the pH adjusting material are granulated to obtain a harmful ion adsorbing material. Thereafter, the obtained harmful ion adsorbent is brought into contact with the water to be treated. Therefore, from the viewpoint of facilitating mixing, the pH adjuster preferably has the same shape as the hydrotalcite-like compound.

  After the step S1 of bringing into contact with the hydrotalcite-like compound, the pH of the water to be treated whose pH has been adjusted through the step S2 of bringing into contact with the pH adjusting material is 5.8 to 8.6. Is suitable.

(Second Embodiment)
Next, an embodiment of a harmful ion removing apparatus for drinking water that realizes the method for removing harmful ions for drinking water according to the above-described embodiment will be described. FIG. 2 is a diagram schematically showing the harmful ion removing apparatus 1 for drinking water according to this embodiment.

  The harmful ion removal apparatus 1 for drinking water includes a harmful ion removal tower 11 (hazardous ion removal section) in which a hydrotalcite-like compound is packed inside a column type adsorption tower and the like, and a pH inside the column type adsorption tower and the like. And a pH adjusting tower 12 (pH adjusting unit) filled with the adjusting material. The harmful ion removal tower 11 removes harmful ions in the water to be treated by bringing the water to be treated containing the harmful ions into contact with the hydrotalcite-like compound. Further, the pH adjusting tower 12 adjusts the pH of the water to be treated that has contacted the hydrotalcite-like compound by bringing the water to be treated in contact with the hydrotalcite-like compound in the harmful ion removal tower 11 into contact with the pH adjuster. To do.

  A first supply pipe 14 that supplies water to be treated to the harmful ion removal tower 11 is connected to the upper portion of the harmful ion removal tower 11. The lower part of the wall surface of the harmful ion removing tower 11 and the upper part of the pH adjusting tower 12 are connected by a second supply pipe 15 that supplies water to be treated to the pH adjusting tower 12. In FIG. 2, the harmful ion removing unit and the pH adjusting unit are configured as separate towers, but the hydrotalcite-like compound and the pH adjusting material are mixed and packed in one adsorption tower, You may comprise a removal part and a pH adjustment part in the same tower.

  The water to be treated containing harmful ions pumped from the well 13 by the pump 16 is supplied to the harmful ion removing tower 11 through the first supply pipe 14. The water to be treated flows through the harmful ion removal tower 11 in a downward flow, and harmful ions are adsorbed and removed by the hydrotalcite-like compound in the process (S1). The water to be treated that has come into contact with the hydrotalcite-like compound is supplied to the pH adjusting tower 12 via the second supply pipe 15. Thereafter, the water to be treated flows through the pH adjusting tower 12 in a downward flow, and impurity ions in the water to be treated are adsorbed on the pH adjusting material in the process. Thereby, pH of process target water is adjusted (S2). For example, the water to be treated whose pH is adjusted is stored in the water storage tank 17 via the third supply pipe 17a connecting the pH adjustment tower 12 and the water storage tank 17, and supplied as drinking water.

  Here, compared with the treatment time (hereinafter also referred to as harmful ion removal time) for removing harmful ions in the water to be treated, which is carried out in the harmful ion removal tower 11, it is in contact with the hydrotalcite-like compound carried out in the pH adjustment tower 12. The treatment time for adjusting the pH of the treated water (also referred to as pH adjustment time) is very long. Therefore, the pH adjustment tower 12 contacts the water to be treated and the pH adjuster in contact with the hydrotalcite-like compound as compared to the time for bringing the water to be treated and the hydrotalcite-like compound in the harmful ion removal tower 11 into contact with each other. It is preferable to have a configuration in which the time is long.

  FIG. 3 is a cross-sectional view schematically showing the harmful ion removing tower 11 and the pH adjusting tower 12 constituting the harmful ion removing apparatus 1 for drinking water according to the second embodiment.

  The harmful ion removal tower 11 is a continuous harmful ion removal tower in which water to be treated and a hydrotalcite-like compound are brought into contact with each other in a continuous treatment system. Inside the harmful ion removal tower 11, a tube 21 filled with a hydrotalcite-like compound (not shown) is provided. The upstream end of the pipe 21 is connected to the first supply pipe 14, and the downstream end of the pipe 21 is connected to the second supply pipe 15. The tube 21 is provided, for example, so as to reciprocate between the upper surface and the lower surface of the harmful ion removal tower 11 along the central axis of the cylindrical harmful ion removal tower 11.

  Moreover, the pH adjustment tower 12 is a continuous pH adjustment tower in which the water to be treated that has contacted the hydrotalcite-like compound is brought into contact with the pH adjuster in a continuous treatment manner. Inside the pH adjusting tower 12, a pipe 22 filled with a pH adjusting material (not shown) is provided. The upstream end of the pipe 22 is connected to the second supply pipe 15, and the downstream end of the pipe 22 is connected to the third supply pipe 17a. The tube 22 is provided so as to reciprocate between the upper surface and the lower surface of the pH adjustment tower 12 along the central axis of the cylindrical pH adjustment tower 12, for example.

  The water to be treated that has come into contact with the hydrotalcite-like compound in the pipe 21 of the harmful ion removal tower 11 is supplied to the pipe 22 in the pH adjustment tower 12 through the second supply pipe 15.

  In addition, harmful ions contained in the water to be treated react with the hydrotalcite-like compound filled in the tube 21 to remove harmful ions from the water to be treated. Therefore, the channel cross-sectional area and the channel length of the tube 21 are appropriately selected in consideration of the reaction time between harmful ions and the hydrotalcite-like compound.

  Further, impurities that are contained in the water to be treated and increase the pH of the water to be treated react with the pH adjusting material that is filled in the pipe 22, whereby the impurities are removed from the water to be treated. Therefore, the channel cross-sectional area and the channel length of the tube 22 are appropriately selected in consideration of the reaction time between the impurities and the pH adjusting material.

  In addition, as shown in FIG. 3, an example in which the tube 21 is provided so as to reciprocate between the upper surface and the lower surface of the harmful ion removal tower 11 is shown here, but the shape of the tube 21 is not particularly limited. Absent. For example, the tube 21 may be provided in a spiral shape along the central axis of the harmful ion removal tower 11. Similarly to the tube 21, the shape of the tube 22 is not particularly limited, and may be provided spirally along the central axis of the pH adjusting tower 12.

  As described above, according to the harmful ion removing apparatus 1 for drinking water according to the second embodiment, the continuous harmful ion removing tower 11 for bringing the water to be treated and the hydrotalcite-like compound into contact with each other in a continuous treatment system, And a continuous pH adjusting tower 12 for bringing the water to be treated and the pH adjusting material into contact with each other by a continuous processing method. Therefore, harmful ions can be continuously removed from the water to be treated containing harmful ions. Moreover, the pH of the water to be treated that has come into contact with the hydrotalcite-like compound can be continuously adjusted.

(Third embodiment)
FIG. 4 is a diagram schematically illustrating a harmful ion removing device 30 for drinking water according to the third embodiment. In the harmful ion removal apparatus 30 for drinking water of the third embodiment, the harmful substance for drinking water of the second embodiment is different except that the pH adjusting material supply unit 38 is added and the configuration of the pH adjusting tower 32 is different. The configuration is basically the same as that of the ion removing apparatus 1. Therefore, here, the different configuration will be mainly described. In the embodiment described below, the same components as those in the harmful ion removing apparatus 1 for drinking water according to the second embodiment are denoted by the same reference numerals, and redundant description is omitted or simplified. .

  As shown in FIG. 4, the harmful ion removing device 30 for drinking water includes a harmful ion removing tower 11 and a pH adjusting tower 32. The pH adjustment tower 32 is a batch-type pH adjustment tower in which water to be treated that has come into contact with the hydrotalcite-like compound is brought into contact with a pH adjuster in a batch treatment manner. Here, an example in which the pH adjustment tower 32 includes three towers of a first pH adjustment tower 32a, a second pH adjustment tower 32b, and a third pH adjustment tower 32c will be described. There are no particular restrictions on the number of towers that constitute the structure.

  The second supply pipe 35 is connected to the harmful ion removing tower 11 and the pH adjusting tower 32. Specifically, the upstream end of the second supply pipe 35 is connected to the harmful ion removal tower 11. And the 2nd supply pipe | tube 35 has a branch part, and the downstream end of the 2nd supply pipe | tube 35 is connected with pH adjustment towers 32a, 32b, 32c.

  Moreover, the harmful ion removing device 30 for drinking water includes a pH adjusting material supply unit 38 for supplying a pH adjusting material to the pH adjusting towers 32a, 32b, and 32c through a fourth supply pipe 38a. The fourth supply pipe 38a has a branch part, the upstream end of the fourth supply pipe 38a is connected to the pH adjusting material supply part 38, and the downstream end of the fourth supply pipe 38a is pH adjusted. The towers 32a, 32b, and 32c are connected.

  The pH adjustment column 32 accommodates the water to be treated that has contacted the hydrotalcite-like compound supplied from the harmful ion removal column 11 and the pH adjustment material supplied from the pH adjustment material supply unit 38. The pH adjustment tower 32 is composed of a tank, for example.

  Moreover, the harmful ion removing device 30 for drinking water may include a transport device (not shown) such as a conveyor that can transport the pH adjusting towers 32a, 32b, and 32c. For example, the transport device (not shown) has a pH adjustment tower 32a at the downstream end of the second supply pipe 35 that is the supply location of the water to be treated and the downstream end of the fourth supply pipe 38a that is the supply location of the pH adjusting material. , 32b, 32c are moved and stopped. And the 2nd supply pipe | tube 35 and the 4th supply pipe | tube 38a are connected to the pH adjustment towers 32a, 32b, 32c, and the water to be processed to the pH adjustment towers 32a, 32b, 32c via the second supply pipe 35 And the supply of the pH adjusting material to the pH adjusting towers 32a, 32b, and 32c through the fourth supply pipe 38a are completed, the second adjusting pipe 35 and the second supplying pipe 35 and the second adjusting pipe are supplied from the pH adjusting towers 32a, 32b, and 32c. 4 is removed, and the transport device moves the pH adjusting towers 32a, 32b, and 32c from the supply location of the water to be treated and the pH adjusting material. Subsequently, the transport device moves the new pH adjusting tower to the supply location of the water to be treated and the pH adjusting material and stops it. Then, the series of operations described above are repeated.

  Next, the process flow of the harmful ion removing device 30 for drinking water will be described.

  The water to be treated containing harmful ions pumped from the well 13 by the pump 16 is supplied to the harmful ion removal tower 11 via the first supply pipe 14. The water to be treated containing harmful ions flows in the tube 21 of the harmful ion removing tower 11. At this time, when the water to be treated containing harmful ions comes into contact with the hydrotalcite-like compound, the harmful ions contained in the water to be treated are adsorbed and removed by the hydrotalcite-like compound.

  Subsequently, the water to be treated that has come into contact with the hydrotalcite-like compound is supplied to the pH adjusting towers 32 a, 32 b, and 32 c through the second supply pipe 35. It should be noted that the water to be treated that has come into contact with the hydrotalcite-like compound is supplied to the first pH adjusting tower 32a, the second pH adjusting tower 32b, or the third by a not-shown changeover switch or the like provided in the second supply pipe 35. May be selectively supplied to the pH adjusting column 32c.

  Subsequently, the pH adjustment material discharged from the pH adjustment material supply unit 38 is in contact with the hydrotalcite-like compound stored in the pH adjustment towers 32a, 32b, and 32c via the fourth supply pipe 38a. Supplied to water. Then, the pH of the water to be treated is adjusted by bringing the water to be treated in contact with the hydrotalcite-like compound into contact with the pH adjuster. The pH adjusting material is selectively supplied to the first pH adjusting tower 32a, the second pH adjusting tower 32b, or the third pH adjusting tower 32c by a changeover switch (not shown) provided in the fourth supply pipe 38a. May be supplied.

  Moreover, before the water to be treated that has come into contact with the hydrotalcite-like compound is supplied to the pH adjusting towers 32a, 32b, and 32c, the pH adjusting material may be supplied in advance to the pH adjusting towers 32a, 32b, and 32c. Further, in addition to the supply of the pH adjusting material from the pH adjusting material supply unit 38 or not the supply of the pH adjusting material from the pH adjusting material supply unit 38, the pH adjusting material is placed in the pH adjusting towers 32a, 32b, 32c. It may be installed in advance.

  Moreover, although shown about the example which the supply place of the process target water which contacted the hydrotalcite-like compound and the supply place of the pH adjusting material were the same, these supply places may differ.

  Further, the water to be treated in the pH adjusting towers 32a, 32b, 32c may be stirred by a stirring device (not shown). When the water to be treated is stirred, the pH adjusting material is uniformly dispersed in the water to be treated. Therefore, the reaction between the impurities that raise the pH of the water to be treated and the pH adjusting material is promoted, and the time for adjusting the pH of the water to be treated is shortened.

  After adjusting the pH of the water to be treated, the pH adjusting towers 32a, 32b, and 32c are distributed to homes, for example, and the water to be treated whose pH has been adjusted is used as drinking water.

  As described above, according to the harmful ion removing device 30 for drinking water of the third embodiment, the continuous harmful ion removing tower 11 that makes the water to be treated and the hydrotalcite-like compound contact in a continuous treatment system, And a batch-type pH adjusting tower 32 for bringing the water to be treated and the pH adjusting material into contact with each other by a batch processing method. Therefore, harmful ions can be continuously removed from the water to be treated containing harmful ions. Moreover, the pH of the water to be treated that has come into contact with the hydrotalcite-like compound can be individually adjusted for each of the pH adjustment towers 32a, 32b, and 32c.

(Fourth embodiment)
FIG. 5 is a diagram schematically illustrating a harmful ion removing device 40 for drinking water according to the fourth embodiment. In the harmful ion removal apparatus 40 for drinking water of the fourth embodiment, the drinking water of the second embodiment is different except that a hydrotalcite-like compound supply unit 49 is added and the configuration of the harmful ion removal tower 41 is different. This is basically the same as the configuration of the harmful ion removal apparatus 1 for use. Therefore, here, the different configuration will be mainly described.

  As shown in FIG. 5, the harmful ion removing device 40 for drinking water includes a harmful ion removing tower 41 and a pH adjusting tower 12. The harmful ion removal tower 41 is a batch-type harmful ion removal tower in which water to be treated and a hydrotalcite-like compound are brought into contact with each other by a batch treatment system. Here, an example in which the harmful ion removal tower 41 includes three towers of the first harmful ion removal tower 41a, the second harmful ion removal tower 41b, and the third harmful ion removal tower 41c will be described. The number of towers constituting the harmful ion removing tower 41 is not particularly limited.

  The first supply pipe 44 is connected to the well 13 and the harmful ion removal tower 41. Specifically, the upstream end of the first supply pipe 44 is connected to the well 13. The first supply pipe 44 has a branch portion, and the downstream end of the first supply pipe 44 is connected to harmful ion removal towers 41a, 41b, 41c.

  Moreover, the harmful ion removal apparatus 40 for drinking water has a hydrotalcite-like compound supply unit 49 for supplying a hydrotalcite-like compound to the harmful ion removal towers 41a, 41b, 41c via the fifth supply pipe 49a. Prepare. The fifth supply pipe 49a has a branch part, the upstream end of the fifth supply pipe 49a is connected to the hydrotalcite-like compound supply part 49, and the downstream end of the fifth supply pipe 49a is It is connected to harmful ion removal towers 41a, 41b, 41c.

  The harmful ion removal tower 41 accommodates the water to be treated containing harmful ions supplied from the well 13 and the hydrotalcite-like compound supplied from the hydrotalcite-like compound supply unit 49. The harmful ion removal tower 41 is composed of a tank, for example.

  Further, the harmful ion removing device 40 for drinking water may include a transport device (not shown) such as a conveyor capable of transporting the harmful ion removing towers 41a, 41b, 41c. For example, the transport device (not shown) has harmful ions at the downstream end of the first supply pipe 44 that is the supply location of the water to be treated and the downstream end of the fifth supply pipe 49a that is the supply location of the hydrotalcite-like compound. The removal towers 41a, 41b, 41c are moved and stopped. Then, the first supply pipe 44 and the fifth supply pipe 49a are connected to the harmful ion removal towers 41a, 41b, 41c, and the processing to the harmful ion removal towers 41a, 41b, 41c via the first supply pipe 44 is performed. After the supply of the target water and the supply of the hydrotalcite-like compound to the harmful ion removal towers 41a, 41b, 41c through the fifth supply pipe 49a are completed, the first from the harmful ion removal towers 41a, 41b, 41c. The supply pipe 44 and the fifth supply pipe 49a are removed, and the transfer device moves the harmful ion removal towers 41a, 41b, and 41c from the supply location of the water to be treated and the hydrotalcite-like compound. Subsequently, the transport device moves and stops the new harmful ion removal tower to the supply location of the water to be treated and the hydrotalcite-like compound. Then, the series of operations described above are repeated.

  Next, the process flow of the harmful ion removing device 40 for drinking water will be described.

  Water to be treated containing harmful ions pumped from the well 13 by the pump 16 is supplied to the harmful ion removal towers 41a, 41b, and 41c through the first supply pipe 44. It should be noted that the water to be treated containing harmful ions is removed from the first harmful ion removal tower 41a, the second harmful ion removal tower 41b, or the third harmful water by a switch (not shown) provided in the first supply pipe 44 or the like. You may selectively supply to the ion removal tower 41c.

  Subsequently, the hydrotalcite-like compound discharged from the hydrotalcite-like compound supply unit 49 is supplied to the treatment target water stored in the harmful ion removal towers 41a, 41b, 41c through the fifth supply pipe 49a. Is done. Then, when the treatment target water containing harmful ions comes into contact with the hydrotalcite-like compound, the harmful ions contained in the treatment target water are removed. The hydrotalcite-like compound is removed from the first harmful ion removal tower 41a, the second harmful ion removal tower 41b, or the third harmful ion removal by a changeover switch (not shown) provided in the fifth supply pipe 49a. It may be selectively supplied to the tower 41c.

  In addition, the hydrotalcite-like compound may be supplied in advance to the harmful ion removal towers 41a, 41b, and 41c before the water to be treated containing harmful ions is supplied to the harmful ion removal towers 41a, 41b, and 41c. In addition to the supply of the hydrotalcite-like compound from the hydrotalcite-like compound supply unit 49 or the supply of the hydrotalcite-like compound from the hydrotalcite-like compound supply unit 49, You may install beforehand in the harmful ion removal towers 41a, 41b, 41c.

  Moreover, although shown about the example which the supply place of the process target water which contacted the hydrotalcite-like compound and the supply place of the pH adjusting material were the same, these supply places may differ.

  Further, the water to be treated in the harmful ion removal towers 41a, 41b, 41c may be stirred by a stirring device (not shown). When the water to be treated is stirred, the hydrotalcite-like compound is uniformly dispersed in the water to be treated. Therefore, the reaction between the hydrotalcite-like compound and harmful ions is promoted, and the time for removing harmful ions contained in the water to be treated is shortened.

  Subsequently, the water to be treated that has come into contact with the hydrotalcite-like compound is supplied to the pH adjustment tower 12 via the second supply pipe 15. Then, the pH of the water to be treated is adjusted by bringing the water to be treated in contact with the hydrotalcite-like compound into contact with the pH adjuster.

  For example, the water to be treated whose pH is adjusted is stored in the water storage tank 17 through the third supply pipe 17a and used as drinking water.

  As described above, according to the harmful ion removing device 40 for drinking water of the fourth embodiment, the batch-type harmful ion removing tower 41 that makes the water to be treated and the hydrotalcite-like compound contact in a batch processing manner, And a continuous pH adjusting tower 12 for bringing the water to be treated and the pH adjusting material into contact with each other by a continuous processing method. Therefore, harmful ions can be individually removed from the water to be treated containing harmful ions for each of the harmful ion removal towers 41a, 41b, 41c. Moreover, the pH of the water to be treated that has come into contact with the hydrotalcite-like compound can be continuously adjusted.

(Fifth embodiment)
FIG. 6 is a diagram schematically illustrating a harmful ion removing device 50 for drinking water according to the fifth embodiment. In the harmful ion removing device 50 for drinking water according to the fifth embodiment, a hydrotalcite-like compound supply unit 49 and a pH adjusting material supply unit 38 are added, and the harmful ion removing column 41 and the pH adjusting column 32 are configured. Except for the difference, the configuration is basically the same as the configuration of the harmful ion removing apparatus 1 for drinking water according to the second embodiment. Therefore, here, the different configuration will be mainly described.

  As shown in FIG. 6, the harmful ion removing apparatus 50 for drinking water includes a harmful ion removing tower 41 (41a, 41b, 41c) and a pH adjusting tower 32 (32a, 32b, 32c). As described above, the harmful ion removal tower 41 is a batch-type harmful ion removal tower in which the water to be treated and the hydrotalcite-like compound are brought into contact with each other by a batch treatment system, and the pH adjustment tower 32 is composed of a hydrotalcite-like compound and a hydrotalcite-like compound. It is a batch type pH adjusting tower in which the water to be treated is brought into contact with the pH adjusting material by a batch processing method.

  Further, the harmful ion removing device 50 for drinking water has a hydrotalcite-like compound supply unit 49 for supplying a hydrotalcite-like compound to the harmful ion removal towers 41a, 41b, 41c via the fifth supply pipe 49a. Prepare. Moreover, the harmful ion removing apparatus 50 for drinking water includes a pH adjusting material supply unit 38 that supplies a pH adjusting material to the pH adjusting towers 32a, 32b, and 32c through a fourth supply pipe 38a.

  Next, the process flow of the harmful ion removing device 50 for drinking water will be described.

  As described above, the water to be treated containing harmful ions pumped from the well 13 by the pump 16 is supplied to the harmful ion removing towers 41a, 41b, and 41c through the first supply pipe 44. Subsequently, the hydrotalcite-like compound discharged from the hydrotalcite-like compound supply unit 49 is supplied to the treatment target water stored in the harmful ion removal towers 41a, 41b, 41c through the fifth supply pipe 49a. Is done. Then, when the treatment target water containing harmful ions comes into contact with the hydrotalcite-like compound, the harmful ions contained in the treatment target water are removed.

  Subsequently, the water to be treated that has come into contact with the hydrotalcite-like compound is supplied to the pH adjusting towers 32 a, 32 b, and 32 c through the second supply pipe 35. The pH adjusting material discharged from the pH adjusting material supply unit 38 is supplied to the water to be treated that has come into contact with the hydrotalcite-like compound stored in the pH adjusting towers 32a, 32b, and 32c via the fourth supply pipe 38a. Is done. Then, the pH of the water to be treated is adjusted by bringing the water to be treated in contact with the hydrotalcite-like compound into contact with the pH adjuster.

  After adjusting the pH of the water to be treated, the pH adjusting towers 32a, 32b, and 32c are distributed to homes, for example, and the water to be treated whose pH has been adjusted is used as drinking water.

  As described above, according to the harmful ion removing device 50 for drinking water of the fifth embodiment, the batch-type harmful ion removing tower 41 for bringing the water to be treated and the hydrotalcite-like compound into contact with each other in a batch processing manner, And a batch-type pH adjusting tower 32 for bringing the water to be treated and the pH adjusting material into contact with each other by a batch processing method. Therefore, harmful ions can be individually removed from the water to be treated containing harmful ions for each of the harmful ion removal towers 41a, 41b, 41c. Moreover, the pH of the water to be treated that has come into contact with the hydrotalcite-like compound can be individually adjusted for each of the pH adjustment towers 32a, 32b, and 32c.

(Sixth embodiment)
FIG. 7 is a diagram schematically illustrating a harmful ion removing device 60 for drinking water according to the sixth embodiment. In the harmful ion removing device 60 for drinking water of the sixth embodiment, a tower 61 is added and the constitution of the harmful ion removing tower 11 and the pH adjusting tower 12 is different, except for the drinking water of the second embodiment. This is basically the same as the configuration of the harmful ion removing apparatus 1. Therefore, here, the different configuration will be mainly described.

  As shown in FIG. 7, the harmful ion removing device 60 for drinking water includes a harmful ion removing tower 11 and a pH adjusting tower 12. In the harmful ion removing device 60 for drinking water, the harmful ion removing tower 11 and the pH adjusting tower 12 are not provided in separate towers, but are provided in a single tower 61. The harmful ion removing device 60 may be a size that can be easily carried by a person or a size that cannot be carried by a person. For example, a gripping portion 61 a is provided on the outer side of the tower 61.

  Here, an example in which the harmful ion removing tower 11 is a continuous harmful ion removing tower and the pH adjusting tower 12 is a continuous pH adjusting tower will be described. However, the harmful ion removing tower 11 is a batch-type harmful tower. The ion removing tower may be used, and the pH adjusting tower 12 may be a batch type pH adjusting tower. For example, the harmful ion removing tower 11 may be a continuous harmful ion removing tower, and the pH adjusting tower 12 may be a batch type pH adjusting tower.

  A harmful ion removal tower 11 is provided in the upper part of the tower 61. A pH adjusting tower 12 is provided below the harmful ion removing tower 11 in the tower 61. For example, the harmful ion removing tower 11 and the pH adjusting tower 12 may be provided so as to be removable from the tower 61. In the lower part of the pH adjusting tower 12 in the tower 61, a storage unit 63 for storing the water to be treated whose pH has been adjusted is provided. The upper part of the harmful ion removing tower 11 may be closed by a lid 65 or may be opened without being closed by the lid 65. Further, the harmful ion removing tower 11 may communicate with the first supply pipe 14.

  On the lower surface 11 a of the harmful ion removal tower 11, a through hole (not shown) for supplying the water to be treated that has come into contact with the hydrotalcite-like compound to the pH adjustment tower 12 is provided. The lower surface 12 a of the pH adjusting tower 12 is provided with a through hole (not shown) that supplies the water to be treated whose pH has been adjusted to the reservoir 63.

  In the space other than the harmful ion removal tower 11, the pH adjustment tower 12, and the storage section 63 in the tower 61, a connecting section 64 extends along the longitudinal direction of the tower 61. The connecting part 64 communicates the upper end part of the tower 61 where the harmful ion removing tower 11 is not provided and the storage part 63. The upper portion of the tower 61 communicating with the connecting portion 64 may be closed with a lid 65, or may be opened without being closed with the lid 65. In addition, the upper part of the tower 61 that communicates with the connection part 64 may communicate with the third supply pipe 17a that distributes the water to be treated whose pH has been adjusted.

  Next, the process flow of the harmful ion removing device 60 for drinking water will be described.

  The water to be treated containing harmful ions is supplied to the harmful ion removing tower 11. For example, thereafter, the upper portion of the tower 61 is closed with a lid 65. The water to be treated containing harmful ions comes into contact with the hydrotalcite-like compound in the harmful ion removal tower 11. Then, harmful ions contained in the water to be treated are adsorbed and removed by the hydrotalcite-like compound.

  The water to be treated that has come into contact with the hydrotalcite-like compound is supplied to the pH adjusting tower 12 by gravity through a through hole provided in the lower surface 11a of the harmful ion removing tower 11. The water to be treated that has come into contact with the hydrotalcite-like compound comes into contact with the pH adjusting material in the pH adjusting tower 12. Then, the pH of the water to be treated in contact with the hydrotalcite-like compound is adjusted.

  The water to be treated whose pH has been adjusted is supplied to the storage unit 63 by gravity through a through hole provided in the lower surface 12a of the pH adjusting tower 12. The water to be treated supplied to the storage unit 63 is supplied from the storage unit 63 to the tower 61 via a spout 61b provided at the upper end of the tower 61, for example, when a person grips the gripping part 61a and tilts the tower 61. It is discharged outside and supplied as drinking water.

  For example, when the harmful ion removing device 60 for drinking water is put in a cold place such as a refrigerator, the water to be treated is cooled while the process performed in the harmful ion removing device 60 for drinking water is performed. . Therefore, the harmful ion removing device 60 for drinking water can supply the treatment target water that has been subjected to the pH treatment as cold drinking water. Furthermore, by distributing the harmful ion removing device 60 for drinking water to the household, the harmful ion removing device 60 for drinking water can individually produce the treatment target water that has been subjected to the pH treatment.

  As described above, the harmful ion removing device 60 for drinking water according to the sixth embodiment includes the harmful ion removing tower 11 and the pH adjusting tower 12 provided in the single tower 61. The harmful ion removing tower 11 and the pH adjusting tower 12 are arranged in the vertical direction. When the treatment target water containing harmful ions is supplied to the harmful ion removal device 60 for drinking water, a downward force due to gravity acts on the treatment target water. Therefore, when the water to be treated containing harmful ions is supplied to the harmful ion removing tower 11, the harmful ion removing device 60 for drinking water can supply drinking water if left untreated.

  According to at least one embodiment described above, harmful ions that are ions composed of at least one selected from arsenic, fluorine, nitric acid, sulfuric acid, boric acid, and selenium are removed, and an increase in pH of drinking water is suppressed. It is possible to provide a method for removing harmful ions for drinking water, a device for removing harmful ions, and a harmful ion adsorbing material.

  Hereinafter, a detailed description will be given with reference to examples. In addition, this invention is not limited at all by these Examples.

  In Examples 1 to 3, it was confirmed that an increase in pH of the water to be treated can be suppressed by removing an element that is leached when the hydrotalcite-like compound comes into contact with the water to be treated with a pH adjuster. Moreover, it tested as follows using the H-type strong acidic cation exchange resin which uses a metakaolin, aluminum silicate, or a styrene- divinylbenzene copolymer as an ion exchange resin frame | skeleton as a pH adjuster, respectively.

Example 1
1 g, 3 g, and 5 g of metakaolin as a pH adjuster were added to 1 g of the hydrotalcite-like compound that was heat-treated. This was immersed in 20 mL of pure water for 6 days, and then the pH of the immersion liquid was measured. The relationship between the mass ratio of the hydrotalcite-like compound and metakaolin and the pH of the immersion liquid is shown in the graph of FIG. The heat treatment conditions for the hydrotalcite-like compound are 500 ° C. and 3 hours.

The pH of the immersion liquid was 11.57 when no metakaolin was added, 9.84 when metakaolin was 1 g, 9.3 when 3 g, and 9 when 5 g. From this, it can be seen that the higher the amount of metakaolin, the more the increase in the pH of the immersion liquid was suppressed. This is because Ca (OH) ₂ produced by hydration of Ca, which is an impurity, and metakaolin undergo a pozzolanic reaction to alleviate an increase in pH due to ionization of Ca (OH) _{2 in} water. Conceivable.

(Example 2)
1 g of aluminum silicate was added as a pH adjuster to 1 g of the hydrotalcite-like compound heat-treated in the same manner as described above. This was immersed in 20 mL of pure water for 1 day, and then the pH of the immersion liquid was measured with a portable pH meter. The relationship between the mass ratio of the hydrotalcite-like compound and aluminum silicate and the pH of the immersion liquid is shown in the graph of FIG.

  The pH of the immersion liquid was 11.57 when no aluminum silicate was added, 10.71 when the aluminum silicate was 1 g, and 8.88 when the aluminum silicate was 3 g. From this, it can be seen that the higher the amount of aluminum silicate, the more the pH of the immersion liquid was suppressed.

(Example 3)
1 g and 3 g of the above strongly acidic cation exchange resin were added as a pH adjuster to 1 g of the hydrotalcite-like compound heat-treated as described above. This was immersed in 20 mL of pure water for 1 hour, and then the pH of the immersion liquid was measured. The relationship between the mass ratio of the hydrotalcite-like compound and the strongly acidic cation exchange resin and the pH of the immersion liquid is shown in the graph of FIG.

  The pH of the immersion liquid was 11.57 when no strongly acidic cation exchange resin was added, 8.19 when the strongly acidic cation exchange resin was 1 g, and 7.45 when 3 g. . From this, it can be seen that as the amount of the strongly acidic cation exchange resin increases, the pH increase of the immersion liquid is suppressed.

  By contacting the hydrotalcite-like compound with the water to be treated, the anions in the water to be treated are adsorbed and removed by the hydrotalcite-like compound. On the other hand, Mg and impurities constituting the base material of the hydrotalcite-like compound It is considered that the pH of the water to be treated rises due to the leaching of Ca, which is As shown in the above results, by adding metakaolin, aluminum silicate, and H-type cation exchange resin capable of adsorbing leached Ca and Mg ions to the hydrotalcite-like compound, It can be seen that the increase in pH of the can be suppressed.

Example 4
In the present Example, the pH increase inhibitory effect of the water to be treated when the hydrotalcite-like compound was washed with water was examined.

  For the purpose of removing impurities contained in the hydrotalcite-like compound, the hydrotalcite-like compound was washed with water as follows. At a liquid-solid ratio of 20 (mL / g), a hydrotalcite-like compound that was heat-treated as described above and a hydrotalcite-like compound that was not heat-treated were each immersed in pure water.

  While measuring the pH of the immersion liquid, it was allowed to stand for 1 to 3 days. When the pH of the immersion liquid was stabilized, the supernatant liquid was taken out and pure water was newly added to exchange the supernatant liquid. The operation of changing the supernatant was repeated. The relationship between the total amount of washing water per unit mass of hydrotalcite-like compound (cumulative washing water amount (mL / g-hydrotalcite-like compound)) and the pH of the immersion liquid, The graph of FIG. 11 shows the pH on the vertical axis.

  As shown in the graph of FIG. 11, in the hydrotalcite-like compound subjected to the heat treatment, it can be seen that the pH of the immersion liquid was lowered from 11.82 at the initial immersion to 10.39. This is presumably because Ca, which is an impurity contained in the hydrotalcite-like compound, was leached into the immersion liquid. Moreover, it turns out from this result that the pH increase inhibitory effect of the process target water which contacted the hydrotalcite-like compound is acquired by performing water washing of the hydrotalcite-like compound. In the hydrotalcite-like compound that is not heat-treated, as shown in the graph of FIG. 11, the pH at the initial stage of immersion is 8.73, and the increase in pH is small. Smaller than heat-treated hydrotalcite-like compound.

(Example 5)
In this example, the effect of suppressing the increase in pH of the water to be treated when an anion was adsorbed to the hydrotalcite-like compound was examined.

  The hydrotalcite-like compound heat-treated in the same manner as described above at a liquid-solid ratio of 20 (mL / g) was immersed in a 10% by mass aqueous sodium chloride (NaCl) solution for 1 hour, and then the solid phase was recovered. The recovered solid phase was dried and then immersed in pure water for 2 days at a liquid-solid ratio of 20 (mL / g). Thereafter, the pH of the immersion liquid was measured. The pH of the immersion liquid was 7.5. Moreover, the XRF analysis of the hydrotalcite-like compound before immersion in NaCl aqueous solution and the solid phase obtained above (hydrotalcite-like compound after immersion in NaCl aqueous solution) was performed. The XRF analysis results are shown in FIG.

  Similarly, the hydrotalcite-like compound not immersed in the NaCl aqueous solution was immersed in pure water, and then the pH of the immersion liquid was measured. The pH of the immersion liquid was 11.6.

From this result, it is understood that an increase in the pH of the water to be treated that has come into contact with the hydrotalcite-like compound can be suppressed by immersing it in an aqueous NaCl solution before the hydrotalcite-like compound is brought into contact with the water to be treated. Further, according to the XRF analysis result of FIG. 12, the Cl content in the hydrotalcite-like compound immersed in the NaCl aqueous solution is increased. From this, it can be seen that by immersing the hydrotalcite-like compound in an aqueous NaCl solution, Cl ⁻ was adsorbed between the layers of the hydrotalcite-like compound and changed to a Cl-type hydrotalcite-like compound.

(Example 6)
In the present Example, the pH increase inhibitory effect of the water to be treated when the Mg / Al molar ratio of the hydrotalcite-like compound was adjusted was examined.

A MgCl ₂ aqueous solution and an AlCl ₃ aqueous solution were mixed, and an aqueous NaOH solution was further added and stirred so that the pH was 10. The solid phase was recovered, dried and subjected to XRD analysis. The results are shown in FIG. From the XRD peak of FIG. 13, it was confirmed that the obtained solid phase was a hydrotalcite-like compound. 1 g of this hydrotalcite-like compound after drying was immersed in 20 mL of pure water, and then the pH of the immersion liquid was measured.

A plurality of hydrotalcite-like compounds having different Mg / Al molar ratios were synthesized by changing the amounts of MgCl ₂ and AlCl ₃ . The synthesized hydrotalcite-like compound has a Mg / Al molar ratio of 2.3 and 3. The pH of the immersion liquid was 5.7 to 6.8 with a hydrotalcite-like compound having a Mg / Al molar ratio of 3 and a Mg / Al molar ratio of 2.3. Here, both the effect of changing the Mg / Al ratio and the effect of Cl-type are obtained.

  Thus, it turns out that the raise of pH of process target water can be suppressed by adjusting Mg / Al molar ratio of a hydrotalcite-like compound.

(Example 7)
In this example, the adsorption performance of the heat-treated hydrotalcite-like compound for arsenic and fluorine was examined. As the simulation target water, water containing 5 mg / L of fluorine and 0.05 mg / L of trivalent arsenic (arsenic trioxide: As ₂ O ₃ ) was prepared. A hydrotalcite-like compound that has been heat-treated in the same manner as described above at a liquid / solid ratio of 100 mL / g is immersed in the simulated treatment target water, and the supernatant liquid at the initial stage of immersion (0 days), 1 day, 3 days, and 7 days later The arsenic concentration and fluorine concentration were measured. The arsenic concentration was measured by hydride generation ICP emission spectroscopy in accordance with JIS K 0102 61.3 (2013). The fluorine concentration was measured by a flow analysis method according to JIS K 0102 34.4 (2013). The results are shown in the graph of FIG. 14 and the concentration of fluorine in the graph of FIG. 15 with the concentration of each element as the vertical axis and the immersion period as the horizontal axis.

(Examples 8 to 10)
Prepare water for simulation treatment containing fluorine and arsenic at the following concentrations, and immerse the heat-treated hydrotalcite-like compound in the same manner as in Example 7 to determine the arsenic concentration in the supernatant after a predetermined period of time. The fluorine concentration was measured in the same manner as in Example 7. The results are shown in FIG. 14 together with Example 7, and the arsenic concentration is shown in FIG.

Example 8: Simulated treatment target water containing 10 mg / L of fluorine and 0.1 mg / L of trivalent arsenic Example 9: 5 mg / L of fluorine and 0 of pentavalent arsenic (arsenic acid: H ₃ AsO ₄ ) Simulated treatment target water containing 05 mg / L Example 10 Simulated treatment target water containing 10 mg / L of fluorine and 0.1 mg / L of pentavalent arsenic

  14 and 15, it can be seen that the heat-treated hydrotalcite-like compound can reduce the arsenic concentration in the water to be treated to less than 0.005 mg / L and the fluorine concentration to less than 0.1 mg / L.

(Example 11)
In Example 11, it was investigated that when the water to be treated that was in contact with the hydrotalcite-like compound was brought into contact with the pH adjuster in a continuous treatment manner, an increase in the pH of the water to be treated could be suppressed.

In the water to be treated after removing harmful anions, that is, the water to be treated that has come into contact with the hydrotalcite-like compound, the pH is increased by alkali ions. Therefore, in order to simulate the water to be treated in contact with the hydrotalcite-like compound, a Ca (OH) ₂ aqueous solution (hereinafter referred to as simulated treated water) adjusted to pH 10 was prepared.

  Then, simulated treated water was passed at a constant rate from the top of a column filled with aluminum silicate as a pH adjuster at room temperature, and the pH of the simulated treated water after passing was measured with a pH meter. FIG. 16 is a graph showing the relationship between the pH of simulated treated water after passing and the passing time of simulated treated water. The vertical axis represents the pH of simulated treated water after passing through, and the horizontal axis represents the passing time of simulated treated water. FIG. 16 also shows the results of measuring the pH of simulated treated water that was passed through a column not filled with aluminum silicate, as a comparative example.

  As shown in FIG. 16, a water quality standard in which the pH of the simulated treated water is 6.5 or more and 8.5 or less by bringing the water to be treated in contact with the hydrotalcite-like compound into contact with the pH adjuster in a continuous treatment manner. It turns out that it was able to adjust in.

(Example 12)
In Example 12, it was investigated that when the water to be treated that was in contact with the hydrotalcite-like compound was brought into contact with the pH adjuster in a batch treatment manner, an increase in the pH of the water to be treated could be suppressed.

  Aluminum silicate was immersed in simulated treated water prepared in the same manner as in Example 11 as a pH adjuster at a liquid-solid ratio of 50:50 at room temperature. Then, the pH of the simulated treated water after the pH adjusting material was immersed in the simulated treated water that was stirred and the simulated treated water that was not stirred was measured with a pH meter. FIG. 17 is a graph showing the relationship between the pH of simulated treated water after immersion and the immersion time of the pH adjusting material. The vertical axis is the pH of simulated treated water after immersion, and the horizontal axis is the immersion time of the pH adjusting material.

  As shown in FIG. 17, the pH of the simulated treated water could be adjusted to 6.5 or more and 8.5 or less by bringing the water to be treated in contact with the hydrotalcite-like compound into contact with the pH adjuster in a batch process. I understand that. Moreover, when the water to be treated and the pH adjusting material were brought into contact with each other by a batch treatment method, the time for adjusting the pH of the simulated treated water within the water quality standard could be shortened by stirring the simulated treated water. Further, the pH of the simulated treated water could be adjusted within the water quality standard within about one day without stirring the simulated treated water.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  1, 30, 40, 50, 60 ... harmful ion removing device, 11, 41 ... harmful ion removing tower, 11a ... lower surface, 12, 32 ... pH adjusting tower, 12a ... lower surface, 13 ... well, 14, 44 ... first Supply pipe, 15, 35 ... second supply pipe, 16 ... pump, 17 ... water tank, 17a ... third supply pipe, 21, 22 ... pipe, 32 ... pH adjustment tower, 32a ... first pH adjustment Tower 32b second pH adjusting tower 32c third pH adjusting tower 38 pH adjusting material supply unit 38a fourth supply pipe 41 harmful ion removing tower 41a first harmful ion Removal tower, 41b ... second harmful ion removal tower, 41c ... third harmful ion removal tower, 49 ... hydrotalcite-like compound supply section, 49a ... fifth supply pipe, 61 ... tower, 61a ... gripping section, 61b ... Spout, 63 ... Storage part, 64 ... Connection part, 65 ... Lid.

Claims (13)

A step of contacting the water to be treated containing harmful ions with a hydrotalcite-like compound to remove the harmful ions in the water to be treated;
A step of bringing the water to be treated in contact with the hydrotalcite-like compound into contact with a pH adjuster, and adjusting the pH of the water to be treated in contact with the hydrotalcite-like compound. Removal method.   The method for removing harmful ions for drinking water according to claim 1, wherein the pH adjusting material is at least one selected from metakaolin, aluminum silicate, and a cation exchange resin. Before the step of contacting the water to be treated and the hydrotalcite-like compound,
The method for removing harmful ions for drinking water according to claim 1 or 2, further comprising a step of washing the hydrotalcite-like compound with water. Before the step of contacting the water to be treated and the hydrotalcite-like compound,
The method for removing harmful ions for drinking water according to any one of claims 1 to 3, further comprising the step of adsorbing anions on the hydrotalcite-like compound. Before the step of contacting the water to be treated and the hydrotalcite-like compound,
The method for removing harmful ions for drinking water according to any one of claims 1 to 4, further comprising a step of adjusting the composition of the hydrotalcite-like compound.   The pot for drinking water according to claim 5, wherein in the step of adjusting the composition of the hydrotalcite-like compound, the composition of the hydrotalcite-like compound is adjusted to 2 to 4 in a molar ratio represented by Mg / Al. How to remove harmful ions.   The method for removing harmful ions for drinking water according to any one of claims 1 to 6, wherein the harmful ions are ions composed of at least one selected from arsenic, fluorine, nitric acid, sulfuric acid, boric acid and selenium. A harmful ion removing unit that removes the harmful ions in the water to be treated by bringing the water to be treated and a hydrotalcite-like compound into contact with each other.
A pH adjusting unit that adjusts the pH of the water to be treated in contact with the hydrotalcite-like compound by contacting the water to be treated in contact with the hydrotalcite-like compound in the harmful ion removing unit; A harmful ion remover for drinking water.   The harmful ion removing device for potable water according to claim 8, wherein the harmful ion removing unit is a continuous harmful ion removing unit that brings the water to be treated and the hydrotalcite-like compound into contact with each other by a continuous treatment method.   The harmful ion removing device for potable water according to claim 8, wherein the harmful ion removing unit is a batch type harmful ion removing unit that brings the water to be treated and the hydrotalcite-like compound into contact with each other by a batch processing method.   The said pH adjustment part is a continuous-type pH adjustment part which makes the process target water which contacted the said hydrotalcite-like compound contact with the said pH adjustment material by a continuous treatment system. The harmful ion removal apparatus for drinking water as described.   The said pH adjustment part is a batch-type pH adjustment part which makes the process target water which contacted the said hydrotalcite-like compound contact with the said pH adjuster by a batch processing system. The harmful ion removal apparatus for drinking water as described.   Harmful for drinking water, which is a mixture of a hydrotalcite-like compound that adsorbs harmful ions in water to be treated containing harmful ions and a pH adjuster that adjusts the pH of water to be treated that has come into contact with the hydrotalcite-like compound. Ion adsorbent.

Images