Songling Wang

Clean separation technologies of rare earth resources in China

Abstract After a review on the conventional separation process of rare earths (RE), hyperlink extraction technology was introduced and a potential process was proposed for clean separation of RE. A great amount of acid, base and water was consumed in the conventional RE separation process which included the procedures of raw material dissolving, extraction separation and precipitation. Therefore hyperlink extraction technology had been developed, by which the repeated consumption of acid and base could be avoided during the extraction process. And based on the theory and successful applications of the hyperlink extraction technology, we proposed the integral hyperlink process in which the intermediate acid resulted in individual procedures would be recycled and reused after being treated. The proposed process would make it feasible to consume no chemicals except for oxalic acid, and so could be a promising clean separation technology with a significant reduction on consumption and emission.

Minimum amount of extracting solvent of AB/BC countercurrent extraction separation using organic feed

Abstract For an AB/BC countercurrent extraction separation using organic feed, the conditions to have minimum amount of extracting solvent ( S min ) and minimum amount of scrubbing agent solution ( W min ) were discussed, and the formulae of both S min and W min were deduced. It was shown that only when the ratio of flowrate of central component B leaving aqueous outlet to that leaving organic outlet took a certain optimal value, the AB/BC separation could have S min as well as W min , and this optimal ratio was decided by the separation factors between the three components but independent of feed composition. S min was only relative to the separation factor of A/C pair but regardless of the separation factors of other pairs as well as feed composition, whereas W min was determined by the separation factors between the components together with feed composition. Meanwhile it was also found that the organic stream out of feed stage was same composition as the initial organic feed when the separation system was given by the two minimum amounts and its steady state was achieved. Finally the results above were used to design a LuYb/YbTm separation case and the stage-wise compositions of each component in both the organic and the aqueous phase at steady state were given by computer simulation.

Preparation of ceria with large particle size and high appearance density

Abstract Cerium is one of the most abundant rare earth elements in both bastnasite and monazite. Ceria has been widely used in optical, catalytic, electrolyte, and sensor materials, with unique performances. With the development of functional materials, great interest has been focused on the synthesis and characterization of specific fine/mesoporous ceria powder. In this study, the modified precipitation and recrys-tallization processes combined with a controlled calcination process for fabricating the ceria with large particle size and high appearance density was reported. During precipitation, a certain amount of mineral acid such as nitric acid served as an additive, to adjust the precipitation and crystallization processes of cerium oxalates. An appropriate acidic condition could lead the process into the Oswald ripening stage and made the particles become bigger. Thus, the appearance density of powder was increased. The optimized conditions, such as the temperature, feeding speed, type and concentration of mineral acids, and the concentration of cerium-contained stock solution, were investigated and evaluated.

Extraction of Rare Earth Sulfates Using Saponified HEH (EHP) with Mg2+ Ion as Barrier Agent

As one kind of the most important intermediate materials in rare earth (RE) industry, RE sulfates have been considered difficult to be extracted and separated directly by saponified extractants due to the dissolubility of RE double sulfate of cation. By introducing a barrier agent such as Mg2+ ion in the present work, we proposed and developed a process to extract RE cations in sulfate medium with saponified HEH(EHP). Further, a selection criterion of the barrier agent was discussed. The results have revealed that the natural distribution of the univalent ion , RE3+ and Mg2+ ions, as determined by their extraction sequence in the cascade, hinders the contact between cation and RE ions, and thereby RE double sulfate precipitate does not form during the extraction. Consequently, the study can provide us a strong possibility for extracting and even separating RE using saponified extractants directly from sulfate solution in no need of any transformation of the RE salts employed.

MATLAB simulation of preparation of Sm-loaded extractant directly from HEH（EHP）

Abstract Computer simulation of the preparation process loading rare earth (RE) directly from acidic extractant and RE chloride was established using MATLAB software. The mechanism of the extraction reaction was assumed, and then an experiment was conducted to confirm the mechanism and the apparent equilibrium constant of the reaction was determined as well. Owing to the involvement of H+ ion in the reaction between acidic extractant and RE chloride, the computer simulation of the process was more complicated than that of the extraction only between different rare earths. In the present work, MATLAB software was therefore introduced to handle the resolution of the complicated processing equation, and the simulation was performed by varying some key parameters including feed composition and phase ratio, etc. Consequently this work presented a simple method to simulate the H+ ion involved countercurrent extraction process of rare earths and also provided the practical references for the relative process designing.