JPS598175B2 - 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 high adsorption capacity and durability for heavy metal ions, particularly uranium, dissolved in water.

Conventionally, organic adsorbents such as ion exchange resins or polyamine chelate resins have been used as adsorbents for heavy metal ions dissolved in wastewater, but these adsorbents are used to absorb the vast uranium resources dissolved in natural water, especially seawater. The total adsorption capacity for collecting
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Recently, titanic acid has been proposed as an inorganic adsorbent having the ability to adsorb uranium.

This adsorbent has a particularly excellent ability to adsorb uranium, but powdered titanic acid leaks out when it comes into contact with seawater or during the recovery process.
It is difficult to put it to practical use, and as a method to improve the adsorbent, titanium can be obtained by applying an aqueous solution of titanic acid or titanium salt uniformly dissolved on activated carbon or glass coolant, and drying it as it is or after neutralizing it in aqueous ammonia. A method has been proposed in which acid is supported in the form of a thin film, but the adhesion to the titanic acid carrier is weak, and the film tends to become fine and fall off, making it unsatisfactory in practice.

The present inventors completed the present invention as a result of intensive research to solve such problems.

An object of the present invention is to provide a method for producing a durable heavy metal ion adsorbent that has excellent adsorption ability for heavy metal ions dissolved in water, especially uranium in seawater, and has extremely low dropout and leakage into seawater. It is in.

That is, the present invention is a method for producing a heavy metal ion adsorbent, which is characterized by impregnating a hydrosol of titanic acid into a substance having fine voids and drying the material to support at least 10% by weight of titanic acid.

The titanic acid hydrosol shown in the present invention has a particle size of 1 to 10
0 mμ preferably << is 10 to 50 mμ titanic acid 5 to 70
The hydrosol preferably contains 10 to 50% by weight.

It is difficult to produce a sol with a particle size of less than 1 mμ, and
If it exceeds mμ, it is not preferable because it tends to fall off from the carrier.

Furthermore, if the concentration of titanic acid in the hydrosol is less than 5% by weight, it is necessary to repeat dipping and drying to ensure that the carrier supports at least 10% by weight, and if it exceeds 70% by weight, it becomes difficult to prepare the hydrosol and the viscosity increases. It is desirable to follow the above range because when impregnated into the carrier, the micropores are blocked and the contact efficiency with seawater and adsorption capacity are reduced.

Further, the material having microscopic voids suitable for the present invention is polyvinyl acetal. Polyurethane. Polyvinegar e-vinyl. polyamide. polyethylene. polypropylene. A porous synthetic resin material such as polystyrene, particularly a material having a porosity of 40 to 95%, is suitable for supporting titanic acid.

Among the substances having microscopic voids, those having an average pore diameter of 10μ
The synthetic resin porous body with ~1 mm communicating pores has a high contact efficiency with seawater, so the adsorption speed of heavy metal ions of titanic acid that it can support is extremely fast, especially for collecting uranium from seawater. Suitable as an adsorbent.

Among these, polyvinyl acetal foam firmly supports titanic acid, and even when immersed in seawater for a long period of time, there is very little shedding (providing a highly durable adsorbent).

The method for preparing the hydrosol of titanic acid and supporting titanic acid on the carrier having microscopic voids is to uniformly stir and mix titanic acid into an acidic aqueous solution (PH: 1.0 to 2.5) according to the above range, and then peptize the titanic acid. A hydrosol is prepared and impregnated into the carrier.

As for the impregnation method, it is difficult to impregnate the inside of the fine pores of the carrier by dipping alone, and an effective method is to immerse the carrier in a hydrosol of titanic acid and depressurize it, thereby deaerating the fine pores and impregnating the carrier. .

The impregnation rate of the hydrosol in the carrier is preferably adjusted by appropriate means such as compression or centrifugal dehydration, and the impregnation rate is in the range of 100 to 1000 by weight in order to remove excess hydrosol and at the same time prevent clogging of micropores. is suitable.

Next, the carrier impregnated with titanic acid hydrosol is air-dried.
Drying is carried out at a temperature of 100° C. or less to firmly support titanic acid inside the fine pores of the material.

The amount of titanic acid that can be supported is at least 10% by weight, and if it is less than this range, the performance as an adsorbent is insufficient and it is not suitable for practical use.

The adsorbent produced by the method of the present invention has a high ability to adsorb heavy metal ions, especially uranium, and the titanic acid will not be removed during the process of recovering uranium from the adsorbent using an alkaline aqueous solution or outflow of titanic acid due to contact with seawater. It is an adsorbent with excellent durability.

In addition, the adsorbent is easy to manufacture and process, and is shaped like a plate.
Strip-like. It can be processed into any shape such as a cylindrical shape.

Moreover, the adsorbent has an extremely large utility value in terms of pollution prevention, such as when it is applied to factory wastewater or exhaust treatment to remove heavy metal ions.

The method of the present invention will be explained in more detail below with reference to Examples.

Example 1 Aqueous ammonia is added dropwise to a hydrochloric acid solution containing titanium tetrachloride, neutralized at 5 to 20°C, and the precipitated titanic acid is purified by filtering and washing with water, followed by an aqueous hydrochloric acid solution (PH:
1.5) A hydrosol containing 40% by weight of titanic acid was prepared.

Next, the porosity is 90% with communicating holes. Outer diameter 75m+++inner diameter 25M. with average pore diameter 50μ. A cylindrical porous polyvinyl acetal material with a height of 250 mm was immersed in the above hydrosol and degassed under reduced pressure treatment (8 mmH gL) to impregnate the inside of the voids, followed by centrifugal dehydration treatment and further heat retention at 60 ° C. The mixture was dried in a ventilation dryer to obtain an adsorption slope A carrying 70% titanic acid by weight.

As a comparison, the untreated cylindrical polyvinyl acetal porous body described above was immersed in an aqueous hydrochloric acid solution in which titanium tetrachloride, which has a weight of 40% in terms of titanic acid weight, was uniformly dissolved, and then degassed in the same manner as above. After impregnation, the material was immersed in aqueous ammonia for neutralization, then centrifugally dehydrated, and then dried in the same manner as described above to obtain adsorbent B carrying 75% by weight of titanic acid.

Adsorbents A and B are made by contacting seawater with uranyl nitrate for 20 hours while circulating it through a cylindrical adsorbent, and then carbonating the adsorbent. Uranium was recovered by immersing it in an aqueous sodium solution.

The drop-off rate of titanic acid from the adsorbent due to contact with seawater and the amount of uranium recovered by the adsorbent were quantitatively determined by fluorescent X-ray analysis, and the results shown in Table 1 were obtained.

As shown in the table above, the adsorbent B of the comparative example shows a significant amount of titanic acid falling off, and the amount of uranium recovered is small. It also has an excellent ability to adsorb uranium.

Example 2 The titanic acid hydrosol shown in Example 1 was used to create a porosity of 92% width 100 having communicating pores with an average pore diameter of 100μ.
Using a sheet-like polyvinyl acetal porous material with a length of 200 mm and a thickness of 2 tran, impregnation treatment was performed in the same manner, the impregnation rate was varied in various ways using a squeezing roll, and the amount of titanic acid carried was determined by drying at room temperature. Adsorbents with various changes were obtained.

In addition, as a comparison, the untreated sheet-like polyvinyl acetal was similarly impregnated using the hydrochloric acid aqueous solution of titanium tetrachloride shown in Example 1, and then neutralized by immersing it in aqueous ammonia in the same manner as above. By changing the impregnation rate and drying, adsorbents with varying amounts of titanic acid supported were obtained.

Each of the adsorbents was stirred and immersed in 4 tons of seawater containing 1.2 cm of uranium for one day to adsorb uranium, and measurements were carried out in the same manner as in Example 1. Also, titanic acid falling off from the adsorbents was determined. The results shown in Table 2 were obtained.

As is clear from the table above, the amount of titanic acid supported is small (at least 1
0 weight coefficient is required, and the rate of dropping of titanic acid from the adsorbent by the method of the present invention is extremely small.

Example 3 The sheet-shaped porous polyvinyl acetal adsorbent that can support 150% titanic acid by weight as shown in Example 2 was used as an adsorbent with cupric chloride.
Ferric chloride. Lead dichloride. Chromic anhydride was immersed in 3 tons of aqueous solution containing 10 ppm of each metal ion.
After stirring for a period of time, the adsorbent was immersed in an IN-hydrochloric acid aqueous solution at a temperature of 60°C for 30 minutes to desorb and elute the adsorbed metal ions, and the metal ions in the aqueous solution were quantified. The results shown are obtained.

As shown in the above table, the adsorbent produced by the method of the present invention exhibits excellent adsorption ability for heavy metal ions and is suitable for wastewater treatment.

Example 4 A polyvinyl acetal porous body (100 mm x 200 mm x 2rr
m) Coconut shell activated carbon 8f (20 to 35 mesh) B carrying 50 weight of A and titanic acid was prepared.

The adsorbent is uranium 15TII! 500 tons of seawater containing
After stirring for 1 day in the same manner as in Example 2 to adsorb uranium, uranium was quantified and titanic acid was analyzed according to the method shown in Example 1, and the results shown in Table 4 were obtained.

As shown in the table above, the polyvinyl acetal porous material, which has a relatively macroscopic pore size of 50μ on average, has strong titanic acid support, less shedding, and excellent durability. In comparison, the rate of uranium adsorption from a dilute uranium solution is remarkable and fast.

These results show that polyvinyl acetal is particularly excellent as an adsorbent for collecting uranium dissolved in extremely dilute concentrations in natural seawater.

Claims (1)

[Claims] 1. A method for producing a heavy metal ion adsorbent, which comprises impregnating a hydrosol of titanic acid into a synthetic resin porous body having fine voids and drying the resulting material so that at least 10% of titanic acid is supported by weight. . 2. The method for producing a heavy metal ion adsorbent according to claim 1, wherein the hydrosol contains titanic acid in an amount of 5 to 70% by weight. 3. The method for producing a heavy metal ion adsorbent according to claim 1, wherein the synthetic resin porous body is polyvinyl acetal.