JP-2026075887-A - Method and apparatus for producing layered double hydroxides

Abstract

[Problem] To provide a method for producing layered double hydroxides with high water permeability. [Solution] The method for producing layered double hydroxide includes a production step of mixing an acidic solution and an alkaline solution to produce a slurry-like layered double hydroxide, and a filtration step of filtering the slurry-like layered double hydroxide, wherein the temperature of the layered double hydroxide in the production step is maintained at 30°C or lower and within a temperature range that does not freeze. [Selection Diagram] Figure 4

Inventors

• 小林 裕
• 有江 駿
• 大平 薫乃

Assignees

• 日本国土開発株式会社

Dates

Publication Date

20260511

Application Date

20241023

Claims (10)

1. A production step involves mixing an acidic solution and an alkaline solution to produce a slurry-like layered double hydroxide, The process includes a filtration step of filtering the slurry-like layered double hydroxide, A method for producing layered double hydroxide, comprising maintaining the temperature of the layered double hydroxide in the production step at 30°C or lower and within a temperature range that does not freeze.
2. The filtration step includes a washing step of washing the layered double hydroxide, The method for producing a layered double hydroxide according to claim 1, wherein the temperature of the layered double hydroxide in the washing step is maintained at 30°C or lower and within a temperature range that does not freeze.
3. The process includes a pressing step in which the layered double hydroxide is pressed after the washing step, The method for producing a layered double hydroxide according to claim 2, wherein the temperature of the layered double hydroxide in the pressing step is maintained at 30°C or lower and within a temperature range that does not freeze.
4. The method for producing a layered double hydroxide according to claim 1, wherein the temperature of the layered double hydroxide in the production step is maintained at 30°C or lower and within a temperature range that does not freeze, by adjusting the temperature of at least one of the acidic solution, the alkaline solution, and the liquid mixed in the mixture of the acidic solution and the alkaline solution during the production step.
5. The method for producing layered double hydroxide according to claim 2, wherein the temperature of the washing water used in the washing step is adjusted to maintain the temperature of the layered double hydroxide in the washing step at 30°C or lower and within a temperature range that does not freeze.
6. The method for producing layered double hydroxide according to claim 3, wherein the temperature of the pressing step is maintained at 30°C or lower and within a temperature range that does not freeze, by adjusting the temperature of at least one of the acidic solution, the alkaline solution, and the liquid mixed in the mixture of the acidic solution and the alkaline solution during the production step.
7. A production step involves mixing an acidic solution and an alkaline solution to produce a slurry-like layered double hydroxide, The process includes a filtration step of filtering the slurry-like layered double hydroxide, Based on information showing the relationship between the temperature of the slurry-like layered double hydroxide when producing the layered double hydroxide and the arsenic adsorption performance when water is passed through the produced layered double hydroxide, a temperature range for the slurry-like layered double hydroxide is set such that the arsenic adsorption performance is above a predetermined level. A method for producing layered double hydroxide, comprising maintaining the temperature of the layered double hydroxide in the production step within the set temperature range.
8. The filtration step includes a washing step of washing the layered double hydroxide, The method for producing a layered double hydroxide according to claim 7, wherein the temperature of the layered double hydroxide in the washing step is maintained within the set temperature range.
9. The process includes a pressing step in which the layered double hydroxide is pressed after the washing step, The method for producing a layered double hydroxide according to claim 8, wherein the temperature of the layered double hydroxide in the pressing step is maintained within the set temperature range.
10. A processing unit that mixes an acidic solution and an alkaline solution to produce a slurry-like layered double hydroxide, and filters the slurry-like layered double hydroxide, A apparatus for producing layered double hydroxide, comprising, in the processing unit, a maintenance unit that maintains the temperature of the slurry-like layered double hydroxide and the layered double hydroxide until filtration at a temperature range of 30°C or lower and that does not freeze.

Description

This invention relates to a method and apparatus for producing layered double hydroxides. Layered double hydroxides are known to possess anion exchange properties. It is expected that by immobilizing arsenic, fluorine, boron, selenium, hexavalent chromium, nitrite ions, and other anionic hazardous substances through this anion exchange, these substances can contribute to improving waste safety and detoxification environmental improvement technologies, such as improving the water quality of contaminated water, preventing the leaching of hazardous substances, soil remediation, and promoting the stabilization of hazardous substances at waste disposal sites. Several proposals have been made regarding the production of layered double hydroxides (for example, Patent Document 1). International Publication No. 2009/072488 Figure 1 is a schematic diagram showing a manufacturing line according to one embodiment.Figure 2 is a flowchart of the manufacturing line process.Figure 3 is a graph showing the relationship between the temperature of the slurry-like layered double hydroxide measured during the manufacturing process of the layered double hydroxide product and the water permeability ratio of the layered double hydroxide product.Figure 4 shows the production line with temperature control devices installed at each part. (First embodiment) The first embodiment will be described in detail below with reference to Figures 1 to 4. However, the present invention is not limited to the embodiments described below. The manufacturing line 1 for producing layered double hydroxides in this embodiment includes a production unit 10 for generating layered double hydroxides, a liquid supply unit 30 for supplying a liquid for washing the generated layered double hydroxides, and a processing unit 50 for performing various treatments on the generated layered double hydroxides. Production line 1 manufactures granular layered double hydroxide. The granular layered double hydroxide produced in production line 1 is filled into containers. Contaminated water is supplied to these containers, and harmful substances are removed from the contaminated water by the granular layered double hydroxide, allowing it to be used as industrial water or drinking water. The applicant disclosed in International Application No. PCT/JP2017/046943 (International Publication No. 2018/124190) that harmful substances such as arsenic, iron, and manganese can be removed to drinking water standards using layered double hydroxide. In this embodiment, in addition to removing these harmful substances, even if salt is generated during the production of granular layered double hydroxide, the granular layered double hydroxide is washed to remove the salt, making it suitable for drinking. While details will be described later, it is preferable to keep the electrical conductivity below 5.7 mS/cm. In other words, it is desirable to keep the chloride ion concentration below 200 mg/L. (Generation unit 10) The production unit 10 is for producing layered double hydroxides by mixing an acidic solution containing divalent and trivalent metal ions with an alkaline solution, and mainly consists of a first supply unit 11 for supplying the acidic solution, a second supply unit 12 for supplying the alkaline solution, a rotating stirring unit 15 having a rotating shaft 13 and blades 14 to stir the acidic and alkaline solutions to form a mixture, and a pH adjustment unit 16 located below the rotating stirring unit 15 to adjust the hydrogen ion concentration of the mixture to stop the maturation of the produced layered double hydroxide. Here, layered double hydroxides refer to compounds whose general formula is M²⁺¹ -x M³⁺x (OH) ₂ (A n- ) x/n・mH₂O (where M²⁺ is a divalent metal, M³⁺ is a trivalent metal, A n- is an n-valent anion, 0 < x < 1, m > 0). Layered double hydroxides are sometimes called hydrotalcite-like compounds. Examples of divalent metals include Mg²⁺ , Fe²⁺ , Zn²⁺ , Ca²⁺ , Li²⁺ , Ni²⁺ , Co²⁺ , and Cu²⁺ . Examples of trivalent metals include Al³⁺ , Fe³⁺ , and Mn³⁺ . Examples of anions include HCO₃⁻ , PO₄³⁻ , SO₄²⁻ , Cl⁻ , NO₂²⁻ , NO₃⁻ , etc. Any acid that makes an aqueous solution acidic can be used as the acid in the solution; for example, nitric acid or hydrochloric acid can be used. Furthermore, the alkali included in the alkaline solution can be any substance that makes the aqueous solution alkaline; for example, sodium hydroxide and calcium hydroxide can be used. Sodium carbonate, potassium carbonate, ammonium carbonate, aqueous ammonia, sodium borate, and potassium borate can also be used. These alkalis may be used individually or in combination of two or more types. Specifically, examples include layered double hydroxides represented by the general formula Mg²⁺ 1-x Al³⁺ x (OH) ₂ (A n- ) x/n・mH₂O , and layered double hydroxides represented by the general formula Zn²⁺ 1-x Al³⁺ x (OH) ₂ (A n- ) x/n・mH₂O (where A n- is an n-valent anion, m>0). The first supply unit 11 is