JPS5933121B2 - Manufacturing method of heavy metal ion adsorbent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heavy metal ion adsorbent having a selective adsorption ability for heavy metal ions dissolved in water as cations and complex ions.

Conventional metal ion adsorbents include cation or anion exchange resins, polyamine-based chelate resins, and iminoacetic acid-based chelate resins. These resins adsorb many types of metals indiscriminately and have poor selective adsorption properties for specific useful metals.For example, when collecting uranium dissolved in seawater by adsorption,
It has no adsorption capacity at all.

Recently, titanic acid, resorcinol-arsenic acid resin, triaminophenol glyoxal resin, etc. have been proposed as having adsorption ability for uranium, but their adsorption ability is small and their shape retention in water is unstable. It has not been put into practical use for some reason.

The present inventors have completed the present invention by diligently and extensively conducting systematic research to solve the above-mentioned problems. However, it is an object of the present invention to provide a method for producing a heavy metal ion adsorbent having excellent selectivity and adsorption ability, especially for uranium. That is, the present invention provides 4-hydroxybenzimidazole and 4-hydroxybenzoxazole represented by the general formula (1) , 4-hydroxybenzothiazole or its derivatives and formaldehyde are polycondensed at 40° C. or higher in the presence of an alkaline or acidic catalyst.

Examples of the compound represented by the general formula (1) used in the present invention include 4-hydroxybenzimidazole, 4.6
-dihydroxypenzimidazole, 4-hydroxybenzoxazole, 4,6-dihydroxybenzoxazole, 4-hydroxybenzothiazole, 4,6-hydroxybenzothiazole, and the like.

Examples of formaldehyde include formalin and paraformaldehyde. To polycondensate the compound represented by the general formula (1) with formaldehyde, use the general formula (1)
At least 0.8 mol of formaldehyde, preferably 1 to 20 mol, per 1 mol of the compound represented by 0.00
Heat and stir in the presence of 1 to 1 mol of an acidic catalyst such as hydrochloric acid, phosphoric acid, or sulfuric acid or an alkaline catalyst such as caustic soda at a temperature of 40°C or higher, preferably 60 to 120°C, for about 5 minutes to 15 hours. It is done. In this case, water or an organic solvent such as alcohol or acetone may be used as the reaction medium.
The reaction product after the condensation polymerization reaction is concentrated by heating, or the resin precipitated during the reaction is separated and collected by washing with water.

The water-insoluble resin obtained by this reaction exhibits a light brown to blackish brown color and is infusible. The adsorbent, which is a polycondensation reaction product of the compound represented by the general formula (1) and formaldehyde, contains 4-hydroxybenzimidazole and its derivatives>4-hydroxybenzoxazole and Derivatives>4-hydroxybenzothiazole and the derivatives have the highest adsorption capacity in this order. The heavy metal ion adsorbent obtained by the method of the present invention can absorb iron, copper, zinc, cadmium, lead, nickel, chromium, etc. in an aqueous solution.
It adsorbs heavy metals such as uranium and is particularly selective towards uranyl ions.

When adsorbing heavy metal ions using the adsorbent obtained by the method of the present invention, the adsorbent is packed in a column and brought into contact with heavy metal ion-containing water in the form of fibers, thin films, etc. for an appropriate period of time. . Further, when the heavy metal ion-containing water contains a large amount of alkali or acid, it is desirable to adjust the pH to 4 to 9.5 before use. For example, when removing and recovering heavy metals from industrial wastewater, it is preferable to remove water-insoluble substances and then adjust the pH to 5 to 9 before use.
The adsorbent that has been brought into contact with water containing heavy metal ions may contain acids (e.g. mineral acids such as sulfuric acid, nitric acid, hydrochloric acid, etc.), alkalis (e.g. caustic soda, aqueous ammonia, etc.) depending on the metal, water-soluble carbonates (e.g. sodium carbonate), etc. , ammonium carbonate, etc.) and a water-soluble bicarbonate (e.g., sodium bicarbonate, etc.), the adsorbed heavy metal ions can be desorbed and dissolved and recovered.

The adsorbent obtained by the method of the present invention has extremely high industrial utility value, such as wastewater treatment or recovery of useful heavy metals, especially uranium, from seawater. Examples will be described below.
Example 1 4,6-dihydroxybenzimidazole 57 (0.0
333 mol), 37% formalin 1.57 (0.050
mol) was added with 10 CC of ethyl alcohol, 10 CC of water, and 0.5 Y of hydrochloric acid, and stirred at 80°C for 6 hours to cause a condensation reaction, resulting in a dark brown 4,6-dihydroxybenzimidazole.
A formaldehyde resin was obtained.

The resin does not melt even when heated to 130°C or higher. After immersing 100 watts of the resin in dilute hydrochloric acid for a short time, it was added as an adsorbent to seawater 51 containing 500 μ7 of uranium, stirred at 30°C for 4 days, the resin was separated by sedimentation, and washed with water.
．． The adsorbed uranium was desorbed by immersion in 10 cc of 5N hydrochloric acid at 60°C for 30 minutes, and the uranium in the desorption solution was quantified by measuring ultraviolet fluorescence using the sodium fluoride sphere method. It was found that an equivalent amount of 350 μ7 of uranium was adsorbed.

This means that 3.5 mg of uranium was adsorbed per 7 adsorbents. As a comparative example, an adsorption test was conducted in the same manner as in the above method using 100 m of each of known adsorbents titanic acid and resorcinol-arsenic acid resin as adsorbents. As a result, the amount of uranium adsorbed for each was 1.8 rr19 and 1 per y of adsorbent. .9W was hot.

However, titanic acid is obtained by neutralizing titanium tetrachloride hydrochloric acid solution with caustic soda.

Further, resorcinol-arsenic acid resin is obtained by formalin polymerization of resorcinol-arsenic acid in a conventional manner. The adsorbent according to the method of the present invention showed superior adsorption capacity compared to the known adsorbent. The uranium adsorbed by the adsorbent of the present invention can be easily absorbed using dilute acids such as hydrochloric acid, sulfuric acid, and nitric acid, alkalis such as caustic soda and aqueous ammonia, or carbonates and bicarbonates such as sodium carbonate, ammonium carbonate, and sodium bicarbonate. It is attached and detached.

The desorption process was performed twice by immersing the resin in 10ml of desorption liquid and leaving it for 30 minutes at 50°C.
Shown in the table.

Example 2 In the same manner as in Example 1, the compound represented by the general formula (1) and formaldehyde were polycondensed to obtain a resin.

100 pieces of each of the obtained resins were added to 51 pieces of seawater containing 500μ7 of uranium in the same manner as in Example 1, and stirred at 30°C for 4 hours to adsorb uranium in the seawater. Next, this resin that had adsorbed uranium was subjected to desorption treatment in the same manner as in Example 1, and the results of uranium analysis are summarized in Table 2. From this 4
-Hydroxybenzimidazole derivatives>4-hydroxybenzoxazole derivatives>4-hydroxybenzothiazole derivatives The adsorption amount of uranium by the adsorbent is higher in this order, that is, 4-hydroxybenzimidazole and 4-hydroxybenzothiazole derivatives.
・6-Dihydroxybenzimidazole is found to be a particularly excellent uranium adsorbent.

In addition, commercially available phenyl sulfonic acid-based, aliphatic carboxylic acid-based cation exchange resins, amine-based, quaternary ammonium salt-based anion exchange resins, or polyamine-based and iminodiacetic acid-based cation exchange resins are available. Chelate resin is
Examples with low uranium adsorption capacity 3 Lead nitrate, mercuric nitrate,
Adsorbent 17 produced in the same manner as in Example 1 was added to model wastewater 21 containing 10 ppm of cadmium nitrate and chromic nitrate as metal ions, and stirred at 30°C for 3 hours.
After contact, the adsorbent adsorbing metal ions was separated.

The adsorbent that has adsorbed metal ions is immersed in 1N hydrochloric acid at 60°C for 30 minutes to desorb and elute the adsorbed metal ions, and then the adsorbent is separated and the metal ions in the eluate are separated. Quantification was performed. Specifically, for lead, mercury, and cadmium ions, a portion of the eluate is taken, and after neutralization, an aqueous solution of sodium diethyldithiocarbamate is added to it, and the resulting chelate precipitate is collected on filter paper, which is then analyzed using fluorescent X-rays. Analyzed by. Further, chromium ions were measured according to atomic absorption spectrophotometry. The results are summarized in Table 3. As is clear from the results in Table 3, the adsorbent produced by the method of the present invention has an excellent ability to adsorb heavy metals. Example
4 Adsorbent 100Tf1 produced in the same manner as in Example 1 to seawater 51 to which 0.1 ppm each of uranyl sulfate, cupric chloride, ferric chloride, and nickel chloride were added as non-metallic ions.
9 was added, and the mixture was stirred at 30° C. for 4 days to bring them into contact.

Claims (1)

[Claims] 1 General formula (1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R represents H or OH group and X represents NH, O or S) 4-hydroxybenzo imidazole,
1. A method for producing a heavy metal ion adsorbent, which comprises polycondensing 4-hydroxybenzoxazole, 4-hydroxybenzothiazole, or a derivative thereof with formaldehyde at 40° C. or higher in the presence of an alkaline or acidic catalyst.