JP2018118211A - Liquid purifying method, and adsorbent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid purifying method that selectively adsorbs a specific material in liquid to remove it from the liquid.SOLUTION: A liquid purifying method includes the step of bringing a liquid containing a target material into contact with an adsorbent, to make the adsorbent selectively adsorb the target material contained in the liquid, so that it is removed from the liquid. The adsorbent has a metal organic structure of a zeolite imidazolate skeleton comprising zinc or cobalt ions and 2-methyl imidazolate ligands.SELECTED DRAWING: None

Description

  The present invention relates to a liquid cleaning method and an adsorbent. More specifically, the present invention relates to a method for cleaning a liquid by adsorbing and removing a specific substance in the liquid, and an adsorbent used in the method.

  Conventionally, a large number of metal organic structures in which a metal complex composed of a central metal and a multidentate organic ligand coordinated thereto are accumulated to form a porous three-dimensional structure have been known. Since these metal organic structures can form uniform pores compared to other porous materials such as zeolite and activated carbon, adsorption materials such as hydrogen, carbon dioxide, carbon monoxide, oxygen, nitrogen, hydrocarbons, etc. The use as an occlusion material is expected, and research on its structure and synthesis method is underway (for example, Patent Document 1).

  A technique using such an organometallic structure as an adsorbent is described in Patent Document 2, for example. Patent Document 2 proposes a technique of paying attention to the adsorption ability of a zeolite-like imidazolate structure ZIF-8 to a specific gas and utilizing this in a gas sensor device or the like.

JP 2014-28792 A JP 2014-156434 A

  The techniques disclosed in Patent Documents 1 and 2 treat a specific substance in an object to be processed, which is a gas, with a metal organic structure.

  The present inventors have found a new use of the metal organic structures ZIF-8 and ZIF-67 as adsorbents that selectively adsorb specific substances in a liquid, and have completed the present invention.

According to the present invention, the method includes a step of bringing a liquid containing a target substance into contact with an adsorbent, selectively adsorbing the target substance contained in the liquid to the adsorbent, and removing the liquid from the liquid. A liquid cleaning method comprising:
There is provided a liquid cleaning method in which the adsorbent includes a metal organic structure that is a zeolite type imidazolate skeleton composed of zinc ions or cobalt ions and a 2-methylimidazolate ligand.

Moreover, according to the present invention, an adsorbent comprising a metal organic structure,
The metal organic structure is a zeolitic imidazolate skeleton composed of zinc ions or cobalt ions and a 2-methylimidazolate ligand;
An adsorbent is provided in which the adsorbent selectively adsorbs a target substance in a liquid.

  ADVANTAGE OF THE INVENTION According to this invention, the specific substance contained in to-be-processed liquids, such as a waste_water | drain, can selectively, simply, efficiently and cheaply adsorb and remove the specific substance using such an adsorbent. A method for cleaning the liquid to be removed is provided.

In Example A1-A4, it is a calibration curve which shows the relationship of the 1, 4- dioxane density | concentration of the aqueous solution after processing with ZIF-8 with respect to the 1, 4- dioxane density | concentration of the aqueous solution before a process. It is a calibration curve which shows the relationship of the 1, 4- dioxane density | concentration of the organic solution after a process with ZIF-8 with respect to the 1, 4- dioxane density | concentration of the organic solution before the process in Example B1-B4. FIG. 5 is an adsorption isotherm at 25 ° C. of ZIF-8 for 1,4-dioxane, tetrahydropyran, and cyclohexane in Example C. FIG. 2 is an adsorption isotherm at 25 ° C. of ZIF-8 for benzene, toluene, methylcyclohexane and mesitylene (1,3,5-trimethylbenzene) in Example E. 2 is an adsorption isotherm of ZIF-8 at 25 ° C. for 1,4-dioxane and water. 2 is an adsorption isotherm at 25 ° C. of activated carbon for 1,4-dioxane and water. 2 is an adsorption isotherm at 25 ° C. of zeolite for 1,4-dioxane and water.

  Embodiments of the present invention will be described below.

  The liquid cleaning method of the present embodiment includes a step of bringing a liquid containing a target substance into contact with an adsorbent, selectively adsorbing the target substance contained in the liquid onto the adsorbent, and removing the target substance from the liquid. Including.

  In the method of the present embodiment, the adsorbent is a metal organic structure, and the metal organic structure is a zeolite type imidazolate skeleton (in the present specification, composed of a zinc ion and a 2-methylimidazolate ligand). Or a zeolite type imidazolate skeleton (referred to herein as “ZIF-67”) composed of a cobalt ion and a 2-methylimidazolate ligand. By using ZIF-8 or ZIF-67 as the adsorbent, a specific substance can be selectively and efficiently adsorbed.

  The inventors have found that ZIF-8 and ZIF-67 adsorb specific organic compounds but hardly adsorb water molecules. The inventors have determined that ZIF-8 and ZIF-67 are oxygenated organic compounds or aromatic compounds, particularly oxygenated six-membered ring compounds or aromatic compounds having a phenolic hydroxyl group, such as 1,4-dioxane, It was found to selectively adsorb tetrahydropyran, phenol, benzene and toluene.

  5, 6 and 7 are adsorption isotherms at 25 ° C. for 1,4-dioxane and water molecules of ZIF-8, activated carbon and zeolite. Activated carbon adsorbs both 1,4-dioxane and water molecules (FIG. 6), while zeolite adsorbs none of these (FIG. 7), whereas ZIF-8 adsorbs 1,4-dioxane. Thus, water molecules are not adsorbed (FIG. 5). Therefore, ZIF-8 can be used as an adsorbent for purifying an aqueous solution such as waste water. The present inventors have also found that ZIF-8 hardly adsorbs molecules having a molecular diameter larger than the pore diameter of the ZIF-8. As a result, according to the method of the present embodiment, for example, specific harmful substances existing in an organic waste liquid containing an organic solvent having a molecular diameter larger than the pores of ZIF-8, such as mesitylene, are efficiently adsorbed and removed. can do.

  Moreover, since ZIF-67 has the same structure as ZIF-8, it has the same specific adsorptivity as this.

  In the present embodiment, ZIF-8 and ZIF-67 used as adsorbents are prepared by known methods or are commercially available.

  The form of the adsorbent of the present embodiment can be, for example, powder, granule, granule, pellet, fiber, membrane, film or the like. The adsorbent may contain additional components, such as resins, inorganic particles, and other porous materials, if desired.

  The adsorbent of the present embodiment can be used by any known method, and may be immersed in an object to be processed as it is, or it may be filled with granular materials or pellets in a column, or a film-like material. The liquid can be used by attaching to the filter cartridge.

  In one embodiment, the liquid that can be purified is an aqueous solution or an organic solution, such as waste water, organic waste liquid, and the like.

  As mentioned above, although embodiment of this invention was described, these are illustrations of this invention and can employ | adopt various structures other than the above.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example, this invention is not limited to these illustrations.

(Examples A1 to A4)
In Examples A1 to A4, 0.10 g of ZIF-8 was mixed with 4.0 ml of an aqueous solution in which 1,4-dioxane of the amount shown in the following table was dissolved, and the mixture was stirred at 60 ° C. for 40 hours. Thereafter, the aqueous solution was recovered by centrifugation, and the amount of 1,4-dioxane in the aqueous solution was measured using gas chromatography. Moreover, the calibration curve of the post-treatment equilibrium concentration with respect to the pre-treatment concentration was prepared from the results of Examples A1 to A4 (FIG. 1). The results are also shown in Table 1 below.

(Comparative Example A1)
The same steps as in Examples A1 to A4 were performed except that ZIF-8 was replaced with 0.10 g of activated carbon. The 1,4-dioxane concentration in the aqueous solution after treatment is shown in Table 1 below.

(Comparative Example A2)
The same steps as in Examples A1 to A4 were performed except that ZIF-8 was changed to 0.10 g of zeolite. The 1,4-dioxane concentration in the aqueous solution after treatment is shown in Table 1 below.

(Examples B1 to B4)
In Examples B1 to B4, 0.1 g of ZIF-8 was mixed with 4.0 ml of a mesitylene solution in which 1,4-dioxane in an amount shown in the following table was dissolved, and the mixture was stirred at 40 ° C. for 6 hours. Thereafter, the organic layer was recovered by centrifugation, and the amount of 1,4-dioxane in the organic layer was measured using gas chromatography. Moreover, the calibration curve of the post-treatment equilibrium concentration with respect to the pre-treatment concentration was created from the results of Examples B1 to B4 (FIG. 2). The results are also shown in Table 2 below.

(Comparative Example B1)
The same steps as in Examples B1 to B4 were performed except that ZIF-8 was replaced with 0.1 g of activated carbon. The concentration of 1,4-dioxane in the aqueous solution after treatment is shown in Table 2 below.

(Comparative Example B2)
The same steps as in Examples B1 to B4 were performed except that ZIF-8 was replaced with 0.1 g of zeolite. The concentration of 1,4-dioxane in the aqueous solution after treatment is shown in Table 2 below.

(Example C)
For 1,4-dioxane, tetrahydropyran, and cyclohexane, an adsorption isotherm at 25 ° C. was prepared using ZIF-8 as the adsorbent. The results are shown in FIG. From the results shown in FIG. 3, it was found that ZIF-8 exhibits specific adsorption characteristics for 1,4-dioxane and tetrahydropyran.

(Example E)
For benzene, toluene, methylcyclohexane, and 1,3,5-trimethylbenzene, an adsorption isotherm at 25 ° C. was prepared using ZIF-8 as the adsorbent. The results are shown in FIG. From the results shown in FIG. 4, it was found that ZIF-8 exhibits specific adsorption characteristics for benzene and toluene.

(Example D1)
0.10 g of ZIF-67 was mixed with 4.0 ml of a 1,4-dioxane aqueous solution having a concentration of 19.0 g / L, and the mixture was stirred at 60 ° C. for 40 hours. Thereafter, the aqueous solution was recovered by centrifugation, and the amount of 1,4-dioxane in the aqueous solution was measured using gas chromatography. The results are shown in Table 3.

  As can be seen from the above examples, ZIF-8 and ZIF-67 specifically adsorbed specific organic compounds in aqueous solution or mesitylene solution.

Claims (6)

A liquid cleaning method comprising a step of bringing a liquid containing a target substance into contact with an adsorbent, selectively adsorbing the target substance contained in the liquid to the adsorbent, and removing the target substance from the liquid. There,
A method for cleaning a liquid, wherein the adsorbent includes a metal organic structure that is a zeolite type imidazolate skeleton composed of zinc ions or cobalt ions and a 2-methylimidazolate ligand.   The method for cleaning a liquid according to claim 1, wherein the target substance is an oxygen-containing organic compound or an aromatic compound.   The method for cleaning a liquid according to claim 1 or 2, wherein the target substance is an oxygen-containing six-membered ring compound or an aromatic compound having a phenolic hydroxyl group.   The liquid cleaning method according to claim 1, wherein the target substance is 1,4-dioxane, tetrahydropyran, phenol, benzene, or toluene.   The liquid cleaning method according to claim 1, wherein the liquid is an aqueous solution or an organic solution. An adsorbent comprising a metal-organic structure,
The metal organic structure is a zeolite type imidazolate skeleton composed of zinc ions and 2-methylimidazolate ligands;
An adsorbent that selectively adsorbs a target substance in a liquid.

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