Non-radioactive scandium oxide receiving out of uranium ISR solutions

The task of the research was to study and determine an effective method for the preparation of non-radioactive scandium compounds from uranium In-Situ Recovery (ISR) solutions. The widespread use of scandium is restrained by the high price due to its small production volumes, low content in the raw materials (scandium is a scattered element and does not form its own deposits), as well as the complexity of technological schemes for its extraction. Scandium receiving out of uranium reverses ISR solutions technological scheme was experimental tested, including sorption on MTS 9580 (Purolite’s production) ion exchanger with recurrent ballast impurities desorption and receiving concentrate that contains scandium. New radiation cleaning technological sequencing based on different solubility of radioactive elements and scandium in carbonate solutions, that accompanied by insoluble macro components complex formation, that contains in deactivated scandium concentrate and allows to get scandium oxide with desired component maintenance more than 94 % and less than 0,3 kilobecquerels/kg specific activity level was developed. The developed technology is based on the ability to form soluble carbonate complexes of scandium and radioactive elements, while the main macro components of the concentrate - ferrum, aluminum, calcium, silicon and others under the conditions of carbonation of the concentrate are inert or form insoluble compounds. Optimal radioactive impurity removing from concentrate conditions and scandium leaching from deactivated residue of scandium and macro impurity were studied and identified in laboratory conditions and during pilot tests.

Maintenance of the Metastable State and Induced Precipitation of Dissolved Neodymium (III) in an Na2CO3 Solution

Rare earths dissolved in carbonate solutions exhibit a metastable state. During the period of metastability, rare earths dissolve stably without precipitation. In this paper, neodymium was chosen as a representative rare earth element. The effects of additional NaCl and CO2 on the metastable state were investigated. The metastable state can be controlled by adding NaCl to the Na2CO3 solution. Molecular dynamics studies indicated that the Cl− provided by the additional NaCl partially occupied the coordination layer of Nd3+, causing the delayed formation of neodymium carbonate precipitation. In addition, the additional NaCl decreased the concentration of free carbonate in the solution, thereby reducing the behavior of free contact between carbonate and Nd, as well as resulting in the delay of Nd precipitate formation. Consequently, the period of the metastable state was prolonged in the case of introduction of NaCl. However, changing the solution environment by introducing CO2 can destroy the metastable state rapidly. Introduction of CO2 gas significantly decreased the CO32− content in the solution and increased its activity, resulting in an increase of the free CO32− concentration of the solution in the opposite direction. As a result, the precipitation process was accelerated and the metastable state was destroyed. It was possible to obtain a large amount of rare earth carbonate precipitation in a short term by introducing CO2 into the solution with dissolved rare earths in the metastable state to achieve rapid separation of rare earths without introducing other precipitants during the process.

Determining the Metal Corrosion Rate by Various Techniques and Comparison of the Results

The paper considers methods for calculating the rate of metals corrosion. A comparative analysis of the experimental data on the steel 10 corrosion rate in carbonate solutions with different pH values (6-12.5) and the concentration of carbonate ions on the disk electrode made of steel 10. The calculation of the corrosion rate by the gravimetric method and the method of polarization resistance is carried out. A detailed description of the calculating the corrosion rate stages index from experimental electrochemical data (I-E) obtained on the potentiostat IPC PRO is given. The advantages and disadvantages of the considered methods are indicated.

Influence of electrode material on the electrochemical behavior of the absorbing solution of the quinhydrone method of gases purification from hydrogen sulfide

The electrochemical behavior of carbonate solutions of the quinhydrone at different concentrations 1, 5, 10, 20, and 30 g/dm3 at the exposure time 0…12 days on different electrode materials – Ni and Au were studied by the cyclic voltammetry (CV) method. The catalytic properties of gold different from nickel in the anodic oxidation reactions of the quinhydrone catalyst are noted.

Experimental study on modeling of Pu sorption onto quartz

Plutonium(IV) sorption onto quartz in carbonate solutions was systematically investigated under anaerobic conditions to analyze the sorption behaviors of Pu(IV) with a non-electrostatic model (NEM). Pu(IV) sorption data was obtained from batch sorption experiments as a function of pH and carbonate concentration. The Pu(IV) sorption onto quartz showed similar tendencies to Th(IV), which is considered to be chemically analogous as a tetravalent actinoid. The distribution coefficient, K d , of Pu(IV) onto quartz showed inverse proportionality to the square of the total carbonate concentration under the investigated pH conditions of 8–11. The modeling study, however, revealed a Th(IV) sorption model, which is ≡SOTh(OH)4 − and ≡SOThOH(CO3)2 2−, could not be applied to simulate the Pu(IV) sorption onto quartz. It was inferred that the electrostatic repulsion between negatively charged ligands limited the formation of ≡SOM(OH)4 − and ≡SOMOH(CO3)2 2− for Pu(IV) with smaller ionic radii than Th(IV). The Pu(IV) sorption model was developed as ≡SOPu(OH)3 and ≡SOPu(OH)4 −. In addition, data of Pu(IV) sorption onto muscovite was obtained in order to be compared with data for quartz.