Yanliang Wang

Extraction behavior of bifunctional ionic liquid [N1888][SOPAA] and TBP for rare earth elements

Abstract Extraction and separation of yttrium in chloride medium using tri-n-octylmethylammonium (2-sec-octylphenoxy) acetate ([N 1888 ][SOPAA]) as an extractant were studied in this article. Tri-n-butyl phosphate (TBP) was used as a phase modifier to accelerate phase separation and improve the stability of organic phase. The addition of TBP contributed to shortening phase separation time, increasing extraction capacity of rare earth elements (REEs) and decreasing viscosity of organic phase. The slope analysis method and infrared spectroscopy were conducted to investigate the ion-association extraction mechanisms. Extraction and stripping performances of the different systems were also compared. The article showed that the extraction performance of mixed [N 1888 ][SOPAA] and TBP is superior to that of [N 1888 ][SOPAA] for heavy rare earth element (HREE).

Extraction kinetics of mixed rare earth elements with bifunctional ionic liquid using a constant interfacial area cell

As a bifunctional ionic liquid used for the extraction of yttrium and heavy rare earth elements (REEs), [methyltrioctyl ammonium][(2,6-dimethylheptyl) phenoxy acetic acid] ([N1888][POAA]) has been synthesized in this paper. The extraction kinetics of REEs including La–Lu plus Y except Pm with [N1888][POAA] using a constant interfacial area cell were reported. Comparing with the conventional (2,6-dimethylheptyl) phenoxy acetic acid (HPOAA) extraction system, the forward extraction rate (kao, mm s−1) of heavy REEs in the [N1888][POAA] extraction system increased significantly with an improvement of 8.44 times for yttrium. The effect of stirring speed on the extraction rate of mixed REEs was studied and 300 rpm was suggested to ensure the extraction regimes were chemical reaction-controlled. The effect of temperature was studied and the extraction reaction was controlled by chemical reaction when the temperature was below 298 K. The effect of specific interfacial area was also evaluated which indicated that the bulk phase was the reaction zone. The average extraction rate equation of REEs has also been obtained as: −d[RE](o)/dt = 0.141[RECl3]([N1888][POAA]).

A separation processing for industrial rare earth feed solution by phosphonium ionic liquid type saponification strategy

Abstract A novel ionic liquid type saponification processing based on quaternary phosphonium type bifunctional IL was developed for yttrium separation from ion-adsorbed rare earth deposit. The extractabilities of ([trihexyl(tetradecyl)phosphonium][sec-octylphenoxy acetate] ([P 6,6,6,14 ][SOPAA]) were pronouncedly higher than those of sec-octylphenoxy acetic acid (HSOPAA), a mixture of HSOPAA and [P 6,6,6,14 ]Cl for rare earth elements (REEs). The ion association extraction mechanism contributed to avoiding the numerous saponification procedures using alkali and resulting in saponification wastewater. After 13 stages of extraction and 6 stages of scrubbing sections, the Y(III) was successfully separated from industrial heavy RREs feed, the purity of Y(III) in raffinate was approximately to be 98.9%. Stripping by distilled water was effectively achieved for REEs, which contributed to the decreased consumption of acid to a considerable extent.

Enrichment of trace rare earth elements from the leaching liquor of ion-absorption minerals using a solid complex centrifugal separation process

A novel solid complex centrifugal separation (SCCS) process has been developed to enrich trace rare earth (RE) elements from the leaching liquor of ion-absorption RE minerals. When compared to liquid–liquid centrifugal extraction (LLCE), the proposed process employed 100% extractant without a volatile diluent for the RE enrichment process, which led to a much shorter equilibrium time of 5 min. Taking into account their ability to form solid complexes with RE ions from an aqueous phase, some alkyl phenoxy carboxylic acid derivatives, including p-tert-octylphenoxy acetic acid (POAA), iso-propanoic acid (POPA) and iso-butyric acid (POBA), were synthesized and used as the solid extractants. The SCCS process included the following steps: first, the solid extractants with a saponification degree of 80% were mixed with 0.5 g L−1 RE solution at a liquid/solid phase ratio of 200/1 to obtain the solid RE complexes. Second, the solid RE complexes were separated from the aqueous phase using a liquid/solid centrifugal separator. Finally, a high concentration of RE solution (>200 g L−1) was obtained by the stripping of solid RE complexes with concentrated HCl. In the SCCS process, a precipitation rate of more than 95.4% and a stripping rate of nearly 100% for RE could be achieved. Water solubilities of the as-prepared solid extractants in raffinate solution were tested to be lower than 32.8 ppm at 25 °C and the mass loss were determined as 0.6% for each cycle. The as-obtained high concentration RE solution with the purity of 96.9 wt% can be used directly as a feed solution for the next individual RE element separation.