Extraction and separation of uranium, thorium and rare earth by TBP-HNO3 system

First, the principle of the process

Extraction of thorium and uranium from a nitric acid solution using TBP is one of the most effective methods. During the extraction process, Th(NO ₃ ) ₄ and TBP generate Th(NO ₃ ) ₄ · 2TBP, and silicate silicate and TBP generate UO ₂ (NO ₃ ) ₂ · 2TBP can be extracted. However, the distribution ratio of uranium is higher than that of strontium and is more easily extracted. Since the separation coefficient of uranium and thorium varies with the concentration of TBP, that is, the separation coefficient at low concentration is higher than that at high concentration. Therefore, the separation process uses a method of preferentially extracting uranium at a concentration of 5% TBP, followed by extraction of lanthanum and rare earth with 40% TBP (see Figure 1). It is also possible to extract ruthenium, uranium and rare earth by first 30% TBP extraction, and then extract and separate uranium and plutonium with 5% TBP concentration, followed by extraction and purification of ruthenium by 40% TBP (see Figure 2).

FIG 2 TBP- kerosine Extraction RE / Th / U Process

In addition, the distribution ratio of hydrazine is related to the concentration of hydrazine in the aqueous phase and the concentration of nitric acid. When the concentration of rhodium in the aqueous phase is low and the concentration of TBP in the organic phase is high, the concentration of D _th nitric acid increases. Conversely, if the concentration of rhodium in the aqueous phase is high, D _th is not affected much by the acidity.

If the solution contains tetravalent cerium , it is difficult to separate because it is similar to hydrazine. When extracting hydrazine, hydrogen peroxide can be added to reduce tetravalent cerium to trivalent, and the separation coefficient of cerium and lanthanum can be increased to enhance the separation effect of cerium and lanthanum.

In this process, uranium is extracted with 5% TBP, and the uranyl nitrate-containing solution obtained by back-extracting is purified by oxalic acid precipitation to remove strontium and rare earth, and then ammonia gas is introduced to precipitate uranium ammonium urate. The remaining uranium extract contains antimony, rare earth and impurities such as iron and titanium . The solution is extracted with 40% TBP, and the anti-extraction solution is subjected to concentrated crystallization to recover cerium nitrate. The residual liquid of the extracted ruthenium can be used to recover rare earth.

Second, the process

The process flow of extracting and separating uranium, thorium and rare earth by TBP-HNO ₃ system is shown in Fig. 1.

Figure 1 Process of extracting and separating uranium, thorium and rare earth from TBP-HNO ₃ system

The movement of a tumbler screening machine is usually compared with simple hand screening similar to the [gold washing pan". Basic rotary motion is similar to hand screening. The eccentricity is adjustable from 25 to 40mm, low speed V belt drive is adjustable from 120 to 360rpm. Each product` dwell time can be adjusted in a radial and tangential angle, towards the drive axis.Therefore, establishing the horizontal and throwing three dimensional rolling movement,  materials are evenly dispersed on the entire sieve surface from the center to the  outer edge, and thus spread towards the axis by spiral movement. Small particles are then finished in the whole sieving process. The horizontal and vertical acceleration are increased with the movement of the particles, and then the particles which are close to mesh size will be successfully separated; The larger particles are transported to the exit, the flow can be  controlled by a regulated oriented device at the exit, the oriented device is another factor  which controls the dwell time of the materials.