JPS603388B2 - Recovery method for diethylenetriaminepentaacetic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the use of diethylene triamine pentaacetic acid (hereinafter referred to as DTPA) dissolved in an aqueous solution.

) is related to a method for efficiently recovering DTP
A forms many metal ions and bell ions in an aqueous solution.

In particular, it is used to separate rare earth elements because it has a high ability to form a flange on rare earth elements and there is a large difference in flange formation constant between rare earth elements. For example, the present inventors have developed a method for separating yttrium from an aqueous solution in which yttrium and lanthanide elements are dissolved by using an organic phosphate ester as an extraction solvent and DTPA as a curing agent, and have already filed an application ( Tokuiso Sho 51-6
8332).

In this method, the DTPA used is dissolved at a fairly high concentration, and DTPA is relatively expensive, so if it is implemented industrially, the used DTPA must be recovered and reused. . Traditionally, DTPA has been used as an analytical reagent,
DTP is used for applications such as masking agents for metal ions, but in these cases DTP is used at low concentrations and there is no need for recovery.
Little was known about the solubility of A.

As a result of various studies regarding the solubility of DTPA, the present inventors found that the solubility of DTPA in water decreases significantly in a specific pH range. This method has been developed to recover DTPA with high yield. DTPA
The relationship between the solubility in water and pH or temperature will be explained with reference to the drawings.

Figure 1 shows the solubility of DTPA in water (mo/t/t;
The vertical axis) is a plot of the results measured at room temperature (approximately 190) while changing the pH (axis) of the aqueous solution.

As is clear from FIG. 1, the solubility of DTPA in water is extremely high at pH 2.0 to 2.5. Figure 2 is p
It is a graph showing the relationship between the solubility of DTPA in water (vertical axis) and the temperature of the aqueous solution (° C.: horizontal axis) in H2.2. The solubility of DTPA in water decreases as the temperature decreases, but the pH at which the solubility reaches pole 4 is approximately constant between pH 2.0 and 2.5 regardless of temperature.

In the method of the present invention, the pH of the aqueous solution in which DTPA is dissolved is adjusted to 2.0 to 2.5, and then the precipitated DT
D can be obtained by simply separating PA crystals using a conventional method.
DTPA can be recovered from an aqueous TPA solution. p
The temperature of the DTPA aqueous solution during H adjustment is preferably lower, but the purpose of recovery can be sufficiently achieved at room temperature.

In the method of the present invention, after pH adjustment, in order to sufficiently precipitate DTPA crystals, an aging period is usually allowed for 30 minutes or more, preferably 1 hour or more, after the DTPA crystals begin to precipitate.

Furthermore, precipitation of DTPA can be promoted by adding DTPA powder as a seed crystal to the DTPA aqueous solution after pH adjustment. When recovering DTPA according to the method of the present invention, in some cases DTPA may be added to the DTPA aqueous solution.
In some cases, metal ions that form DTPA are dissolved, but in such cases, it is necessary to separate the metal ions by extraction or precipitation prior to recovery of DTPA. desirable.

The method of the present invention can generally be applied to the recovery of DTPA in an aqueous solution, but it is also a method for extracting and separating a specific diluted compound from a mixed diluted diluted compound using DTPA as a complexing agent and an organic phosphate ester as a citrus agent. It can be particularly advantageously applied when recovering DTPA.

Next, the present invention will be explained in more detail with reference to examples; however, the present invention is not limited to the following examples unless the gist thereof is exceeded.

Example DTPAO-58h〇zo/So, Yttrium 0.1m.

pHi. The aqueous solution of No. 0 was mixed with a kerosene solution of di(2-ethylhexyl) phosphoric acid having a concentration of lmo, and yttrium was extracted and removed from the aqueous phase. After oil and water separation, ammonia water is added to the DTPA aqueous solution to
The temperature was adjusted to 2.2, and DTPA powder was added as a 0.01 ta seed crystal. After 4 hours of fermentation to extract DTPA, the precipitated DTPA was collected in a furnace.

As a result, the amount of DTPA dissolved and remaining in the aqueous solution was 0.13 mm, and the recovery rate of DTPA was 99.4%.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the solubility of DTPA in water (mo〆/〆; vertical axis) and the pH of the aqueous solution (horizontal axis) at room temperature (approximately 15 oo), and Figure 2 shows the relationship between the solubility of DTPA in water at room temperature (approximately 15 ooohs) and the pH of the aqueous solution (horizontal axis). Solubility in water (mozo/so; vertical axis)
It is a graph showing the relationship between the temperature of the aqueous solution and the temperature of the aqueous solution. Illustration of spear 2

Claims (1)

[Claims] 1 In recovering diethylenetriaminepentaacetic acid from an aqueous solution in which diethylenetriaminepentaacetic acid is dissolved,
A method for recovering diethylenetriaminepentaacetic acid, which comprises adjusting the pH of the aqueous solution to 2.0 to 2.5 to precipitate diethylenetriaminepentaacetic acid.