Fukiko Kubota

Selective extraction and recovery of rare earth metals from phosphor powders in waste fluorescent lamps using an ionic liquid system

The recycling of rare earth metals from phosphor powders in waste fluorescent lamps by solvent extraction using ionic liquids was studied. Acid leaching of rare earth metals from the waste phosphor powder was examined first. Yttrium (Y) and europium (Eu) dissolved readily in the acid solution; however, the leaching of other rare earth metals required substantial energy input. Ionization of target rare earth metals from the waste phosphor powders into the leach solution was critical for their successful recovery. As a high temperature was required for the complete leaching of all rare earth metals, ionic liquids, for which vapor pressure is negligible, were used as an alternative extracting phase to the conventional organic diluent. An extractant, N, N-dioctyldiglycol amic acid (DODGAA), which was recently developed, showed a high affinity for rare earth metal ions in liquid-liquid extraction although a conventional commercial phosphonic extractant did not. An effective recovery of the rare earth metals, Y, Eu, La and Ce, from the metal impurities, Fe, Al and Zn, was achieved from the acidic leach solution of phosphor powders using an ionic liquid containing DODGAA as novel extractant system.

Extraction of lactic acid from fermented broth with microporous hollow fiber membranes

Non-dispersive solvent extraction of lactic acid based on anion-exchange reaction with tri-n-octylmethylammonium chloride dissolved in oleyl alcohol, the optimum extraction reagents selected for extractive fermentation of lactic acid with Lactobacillus rhamnosus, was attempted in a microporous hollow fiber membrane device. A satisfactory recovery of lactic acid from both aqueous solution and actual fermented broth was accomplished, signifying the great potential of integrating the membrane extraction with fermentation process. A theoretical model which took into account the mass transfer resistances across organic and aqueous films and membrane was developed to analyze and predict the extraction behavior. The model prediction was found to be in good agreement with the experimentally observed results.

EXTRACTION OF RARE EARTH METALS WITH 2-ETHYLHEXYL PHOSPHONIC ACID MONO-2-ETHYLHEXYL ESTER IN THE PRESENCE OF DIETHYLENETRIAMINEPENTAACETIC ACID IN AQUEOUS PHASE

Abstract The extraction equilibria of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (commercial name, PC-88A, henceforth abbreviated as HR) dissolved in n-heptane were measured at 303 K. It was found that rare earth metals are extracted with the dimer of the extractant, (HR)2, as follows. The extraction equilibrium constants of metals were obtained and compared with the extraction equilibrium constants obtained by di(2-ethylhexyl)phosphoric acid (henceforth D2EHPA). Furthermore, the extraction equilibria of rare earth metals with PC-88A in the presence of diethylenetriaminepentaacetic acid (henceforth DTPA) in an aqueous phase were also measured to discuss the effect of DTPA on the extraction of rare earth metals.

Intermittent partition walls promote solvent extraction of metal ions in a microfluidic device

Liquid–liquid extraction of metal ions was carried out in a microfluidic device which had intermittent partition walls in the center of the confluent microchannel 100 µm wide, 20 µm deep and 3 cm long. The intermittent partition walls (50 µm long) stabilized a two-phase (n-heptane–water) flow and allowed clear phase separation at the end-junction of the microchannel. Using this two-phase flow in the microchannel, yttrium ions were successfully extracted in a complex form with an extractant PC-88A (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) from a feed aqueous phase to a n-heptane phase within a contact time of 1.5 s. Although the apparent interfacial area in the microchannel was reduced by introducing the partition walls, the presence of the partition walls improved the extraction efficiency 2–3 fold at a contact time of 0.12–0.24 s. Flow analyses using fluorescent beads and a computational fluidic dynamics simulation revealed that the partition walls induced a slight turbulence in the two-phase flow in the microchannel. This slight turbulence would result in the mixing of the aqueous phase and promote the transport of yttrium ions from the aqueous feed phase to the organic extractant phase.

Extraction kinetics of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester using a hollow fiber membrane extractor

A kinetic study concerning chemical complexation-based solvent extraction of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester dissolved as an extractant in n-heptane was carried out using a microporous hydrophobic hollow fiber membrane extractor. The effects of concentration of chemical species in aqueous and organic feed solutions on the apparent permeabilities of metal species for extraction and stripping, respectively, were investigated to clarify the permeation mechanism. From the experimental results it was predicted that the permeation rate is controlled by diffusion of the chemical species in aqueous and organic phases and by interfacial chemical reaction. The experimental data were analyzed by the diffusion model accompanied with an interfacial reaction, taking into account the velocity distributions of the aqueous and organic phases through the inner and outer sides of the hollow fiber.

Extraction of rare-earth metals by liquid surfactant membranes containing a novel cyclic carrier

Abstract Extraction behavior of three rare-earth metals (Ho, Er and Y), was systematically studied by liquid surfactant membranes (LSMs) containing a novel host compound, a calixarene carboxyl derivative, which is a cyclic compound connected to some phenol rings, as a mobile carrier in a stirred cell. Using the host compound, the extraction equilibrium of the metals in liquid-liquid extraction was also investigated in order to elucidate the complexation mechanism between the metal ions and the cyclic compound. The calixarene carboxyl derivative showed a high extractability for all rare-earth metal ions compared with the analog monomer compound. The extractability for the rare-earth metals was found to increase in the following order: monomer

Selective extraction of scandium from yttrium and lanthanides with amic acid-type extractant containing alkylamide and glycine moieties

The liquid–liquid extraction of rare earth metal ions (scandium (Sc3+), yttrium (Y3+) and the lanthanides (La3+, Nd3+, Eu3+ and Dy3+)) was investigated using N-[N,N-di(2-ethylhexyl)aminocarbonylmethyl]glycine (D2EHAG). Scandium was extracted selectively from lanthanides under highly acidic conditions (0 < pH ≤ 1.5), and stripped easily using a mild acidic solution such as 1 mol dm−3 H2SO4. By comparing the extraction behavior with N,N-dioctyldiglycol amic acid, which has a similar molecular structure to D2EHAG, or the commercial alkyl monocarboxylic acid extractant, Versatic 10, it was concluded that the affinity of D2EHAG to scandium was caused by a chelating effect and the size recognition ability of D2EHAG. The extraction mechanism was examined, and it was proven that the trivalent scandium ion is extracted by forming a stable metal complex with four D2EHAG molecules.

Extraction of rare earth metals by calix[4]arene solubilized in AOT reversed micellar solution

Abstract Extraction of rare earth metals (europium and yttrium) and their separation from zinc were investigated using a novel host compound, p - tert -octylcalix[4]arene carboxyl derivative as an extractant. Extraction behavior of the metals with a typical commercial extractant PC-88A or Versatic 10 was also examined. The cyclic ligand calixarene showed a high selectivity towards rare earth metals compared with PC-88A and Versatic 10. The addition of sodium ion into the feed aqueous solution enhanced the extractability of rare earth metals, and resultantly, improved the selectivity. The drawback of this promising extractant was the poor solubility in organic solvents, especially in nontoxic aliphatic solvents such as isooctane and kerosene. We attempted to solubilize the novel extractant calix[4]arene in isooctane by utilizing reversed micelles formed with an anionic surfactant AOT. p - tert -Butylcalix[4]arene could be dissolved in the AOT–isooctane reversed micellar solution by injecting an adequate amount of water. Furthermore, the extraction of metals from the aqueous solution dissolving sodium ion was conducted by the AOT–isooctane system containing p - tert -butylcalix[4]arene. The excellent extraction and separation of metals was achieved by using calixarene solubilized in the AOT-reversed micellar solution.

Application of cellulose acetate to the selective adsorption and recovery of Au(III)

Cellulose acetyl derivatives were examined for the selective recovery of Au(III) from acidic chloride solutions as an adsorbent, and cellulose acetate fibers (CAF) were found to be effective for the separation of Au(III) from other metal ions, including the precious metal ions Pt(IV) and Pd(II). The amount of Au(III) adsorbed by the fibers increased with an increase in the hydrochloric acid concentration, but decreased with an increase in the ionic strength of the solution. The adsorption of Au(III) onto CAF took place quickly and an adsorption equilibrium was reached within 1h. The maximum adsorption capacity of Au(III) was determined to be 110 mg/g at 2M hydrochloric acid. The loaded Au(III) was readily recovered by incineration.

Effect of sodium ions on the extraction of rare earth metals by liquid surfactant membranes containing a calix[4]arene carboxyl derivative

A novel host compound calixarene has been applied as a mobile carrier for the separation and concentration of rare earth metals by liquid surfactant membranes (LSMs). Using the novel carrier, extraction of rare earth metals (Ho, Er and Y) by LSMs was systematically studied in a stirred cell. Extraction behavior of rare earth metals by the carboxyl derivative of calix[4]arene was found to be extremely sensitive to coexisting sodium ions in the feed solution. The extractability of rare earth metals was remarkably enhanced by the addition of sodium ions. The permeation rate of rare earth metals through the LSMs in the presence of sodium ions was 100-fold higher than that without sodium ions. This enhancement of the permeation rate is attributed to the preferential conformation change in the host compound of calixarene initiated by sodium ions. The permeation mechanism of rare earth metals by LSMs is elucidated by an interfacial reaction model.