SU706334A1 - Method of purifying nitric acid solutions - Google Patents

Description

I

This invention relates to an improved method for cleaning solutions from diethylene. Triaminepentaacetic acid.

Diethylenetriaminepentaacetic acid. (DTPA) is widely used in extrusion and ion-exchange technology for the isolation of transluorinium elements, especially in group operations for the separation of trans-plutonium and rare-earth elements. The presence of DTPA in solutions of transplutonium elements interferes with further technological operations, such as additional cleaning cycles.

A known method of cleaning solutions from DTPA radiolysis. In this method, a solution containing curium and DTPA is acidified with nitric acid and left to stand for 16 hours. In this case, DTPA is destroyed radiolytically. However, the implementation of this method is possible only with a high specific activity of the solution. The time of complete destruction of DTPA depends on the acidity of the solution, the concentration of transplutonium elements, and their isotopic composition 1.

The purpose of the invention is to simplify the process.

The goal is achieved by destroying DTPA with ozone. The ozonation process is carried out by bubbling the ozone-oxygen and ozone-air mixture through the working solution at 60-90 C.

Concentrations of ozone in the ozone-oxygen mixture of 50-100 mg / l. DTPA degradation products are volatile organic amines, carbon dioxide and water. With a decrease in the ozone concentration in the gas (for example, 2 times) and the same increase in consumption, the rate of destruction of DTPA does not change. The rate also remains constant as the pH of the solution varies from 3.5 to 0.4.

Example. 10 ml of a nitric acid solution containing 0.1 M DTPA and having a pH of 2 is ozonated in a bubbling vessel with a porous bottom. The ozone concentration in the ozone-oxygen mixture is mg / l, the oxygen consumption is zl / h. The concentration of DTPA is determined by titration of a thorium solution with an acidity of 0.1 M HMOe with an xylenol orange indicator.

The destruction of DTPA by ozone as a percentage of the initial content in the solution is given

Example 2. The distribution coefficients of americium are determined by extraction with 80% THF solution in decane from an aqueous phase, which is a sample of an ozonized DTPA solution in 4 M NaNOa containing 300 mg / l Am, pH 2. Condition the ozonation as in example 1. The distribution coefficient (D) of americium from a similar solution that does not contain DTPA is 17.0.

Coefficient of distribution ozonization, laziness americium min

0.002 5.0

11.4 16.1

From the examples it is clear that for complete destruction of DTPA in the solution, 2-2.5 hours of ozonization at 90 ° C is sufficient. Since the technological solutions can contain significant amounts of nitrate salts, experiments on the ozonation of solutions containing from 0 to 6 M sodium nitrate were carried out. The rate of DTPA destruction is constant.

Thus, the rate of destruction of the complexone depends mainly on the temperature of the process and on the amount of ozone fed to the reactor.

The described advantages provide the following advantages: the method is applicable to solutions of any composition; no prior adjustment of the solution is required; the possibility of continuous process.

Claims (2)

1. A method for purifying nitric acid solutions from diethylenetriaminepentaacetic acid by destroying it, characterized in that, in order to simplify the process, the initial nitric acid solution is treated with ozone-oxygen or ozone-air mixture at 60-90C. 2. The method according to claim 1, wherein the concentration of ozone in the ozone-oxygen mixture is 50-100 mg / l. Sources of information taken into account in the examination 1. Atomic Energy Reviw, vol. 10. No. 3, 1972, p. 379-399 (prototype).