A new extractant, [di-(2-ethylhexyl)amino]acetic acid (DEHAA), was synthesized for the mutual separation of In(III), Ga(III), and Zn(II). The extraction selectivity for the metal ions in a 1 M aqueous ammonium nitrate solution with DEHAA was In(III)>Ga(III)>Cu(II)>Zn(II), while Co(II), Cd(II), Se(IV), Se(VI), and Ni(II) were not extracted. The extraction behavior of DEHAA for In(III) and Ga(III) is different from the commercial extractant Versatic 10. The results indicate that the amino moieties in DEHAA play an important role in the selective extraction of In(III), Ga(III), and Zn(II). The extraction equilibria of In(III) and Ga(III) with DEHAA were also discussed. It is observed that In(III) and Ga(III) were extracted as 1:4 complexes, with extraction equilibria constants of K_In = 8.03×10^-2 [(mol dm^-3)^-1] and K_Ga = 9.52×10^-4 [(mol dm^-3)^-1] respectively.

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Solvent extraction of indium (In³⁺), gallium (Ga³⁺), and zinc (Zn²⁺) was investigated using N-[N,N-di(2- ethylhexyl)aminocarbonylmethyl]glycine (D2EHAG) and N-[N,N-di(2-ethylhexyl)aminocarbonylmethyl]- sarcosine (D2EHAS) which we have developed recently. Indium and gallium were selectively extracted from zinc under high acid conditions (0 < pH ≤ 2.0), and easily stripped using an acidic solution such as 2 mol dm^-3 HNO₃. The extraction behavior was compared to that of N,N-dioctyldiglycol amic acid (DODGAA), which has a similar molecular structure to D2EHAG, a commercial alkyl monocarboxylic acid extractant, neodecanoic acid (Versatic 10), or an organophosphorus extractant, di(2-ethylhexyl) phosphoric acid (D2EHPA). Based on the results, D2EHAG and D2EHAS were found to be useful for the separation of In³⁺ and Ga³⁺ from Zn²⁺. The extraction mechanisms of these ions with D2EHAG were investigated through slope analysis and loading tests.

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A solvent extraction spectrophotometric determination method was developed for cerium(IV) using o-methoxy phenylthiourea (OMePT) as a selective reagent. A ternary complex was formed after liquid-liquid extraction from 0.05 mol L^-1 potassium iodide aqueous media using 2.0×10^-4 mol L^-1 OMePT in chloroform and is measured spectrophotometrically at 318 nm. The validity of Beer’s law was in the concentration range up to 22.5 μg mL^-1, with molar absorptivity and Sandell’s sensitivity values of 3.38×10³ L mol^-1 cm^-1 and 0.041 μg cm^-2 respectively. The stoichiometry of the cerium(IV)-OMePT-iodide complex was determined by the slope ratio method and verified by the mole ratio method. The complex was stable for more than 48 h. The method is free from interferences from large number of cations and anions. The developed method was successfully employed for the determination of cerium(IV) from binary synthetic mixtures, ternary synthetic mixtures, soil, tap water and sea water samples.

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Benzothiaoxacrown compounds with different numbers of sulfur and oxygen donor atoms (between 4 to 7 donors) dissolved in an organic diluent selectively extract the soft metal ions Ag(I) and Hg(II) from a mixture of Co(II), Ni(II), Cu(II), Zn(II), Ag(I) and Hg(II) present in an aqueous phase. Generally, the extraction efficiency depends on the specific structure of the benzothiaoxacrowns, on the organic diluent employed, as well as on the counter ion present in the aqueous phase. High extractions of Ag(I) and Hg(II) were achieved with all ligands from perchlorate and picrate aqueous media into nitrobenzene organic solutions. In the case of Cu(I) the extraction is significant lower; only ligand 5 with the O₂S₄ donor atom set gives a moderate extractability. The composition of the extracted complexes depends on the crown ring size and ranges from 1:1 to 1:2 (M:L). Polarographic, UV-Vis and ESI mass spectrometric studies provide a further insight into the complex formation behavior.

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The solvent extraction of Ag(I) from nitrate solutions has been studied using a mixture of LIX84I and PC88A. The mixture showed significant synergism at a LIX84I/PC88A ratio of 0.8:0.2. In order to identify the extraction reaction, the effects of various parameters, such as the equilibrium pH value and extractant concentration, were studied based on the slope analysis method. From stripping studies, 3 mol/L of nitric acid was found to be the best stripping agent. This mixed extractant can be applied for the separation of Ag from a nitrate solution containing Ca, Si, Al, Re, and Ni.

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The solvent extraction of lanthanum(III) and europium(III) by aminooctyldimethylene diphosphonic acid from nitrate media was investigated. The extraction percent of lanthanum(III) and europium(III) was measured as a function of various parameters such as: volume ratio, shaking time, the concentration of aminooctyldimethylene diphosphonic acid, ionic strength and media pH. The metal concentration in the aqueous phase before and after extraction was determined spectrophotometrically by the Arsenazo III method. The extracted species and equilibrium extraction equations were determined by the slope analysis method. It was found that adding KNO₃ at a concentration of 0.1 M significantly enhances the extraction yield for lanthanum(III) and europium(III). Decreasing the media pH caused a gradual decrease of extraction yields. The obtained results showed that extraction of lanthanum(III) and europium(III) from nitrate media using aminooctyldimethylene diphosphonic acid in chloroform is quantitative under well-defined conditions.

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The feasibility to recover indium (In) from discarded liquid crystal display (LCDs) panels by solvent extraction (SX) and a hollow fiber supported liquid membrane with strip dispersion (SLM-SD) system was investigated in this study. Di-(2-ethylhexyl)phosphoric acid (D₂EHPA) was used as the extractant and the mobile carrier in SX and SLM-SD. The effect of different parameters such as pH, concentration of D₂EHPA and stripping agents has been investigated for indium extraction. The average amount of indium in LCD screen was found to be 330 mg/kg and 70% of this indium was easily leached out by 3 M HCl in 30 min. An increase in the D₂EHPA concentration from 0.025 to 0.25 M increased the extraction of indium and 79% of indium can be recovered by back-extraction with 2 M hydrochloric acid. For the SLM-SD system, more than 94% of indium can be recovered within 20 min under the same operating conditions. This indicates that the SLM-SD was more efficient for indium extraction than SX. However, a poor separation of iron and indium resulted on increasing the extraction time. Hence, process optimization for iron removal must be explored in a future work.

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The effect of the addition of diethanolamine (DEA) on the extraction of water and bovine serum albumin (BSA) with the reverse micellar system, sodium bis(2-ethylhexyl)sulfosuccinate (AOT), was investigated using the two phase partition method. The addition of DEA in the aqueous phase affected the extraction of water in the organic reverse micellar phase which increased significantly with a decrease in pH reaching a constant value at pH values lower than 8. This behavior is in good agreement with the extraction behavior of DEA into the organic phase under changing pH. Furthermore, the increase in the water extracted in the organic phase was proportional to the DEA concentration extracted in the organic phase. The increase in water extraction with DEA can be explained by the pH change extraction model taking into consideration DEA dissociation equilibria and the extraction of DEA plus water by the formation of an ion-pair between the DEA ammonium ion and the anionic AOT molecule. The extraction of BSA is enhanced by the addition of DEA at low concentration. With an increase in the quantity of added DEA, the pH range for BSA extraction is extended to a higher pH range. BSA extraction increased with an increase in the DEA concentration over a low concentration range, but decreased with concentration over the high concentration range. The back-extraction of BSA was achieved at approximately 90% by the addition of a high concentration of DEA. The extraction and back-extraction of BSA can be controlled by the concentration of DEA.

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From a green chemical point of view, techniques for extracting organic substances employing conventional solvents must be replaced with novel environment-friendly techniques. Dimethyl ether (DME) may be one of such alternative solvents to be used. Rice bran is a co-product of rice milling, which is rich in oil content. Theoretically, around 20-25% of the total weight of rice bran must be oily components known as rice bran oil (RBO). In the present study, liquefied DME was used as a low temperature solvent for extracting RBO. From 10 g of fully dried rice bran used in a single batch extraction with DME, ca. 0.90 g of RBO were recovered (efficiency, 9.0%). Although the efficiency of total RBO extraction by batch extraction with DME was lower than the conventional solvent extraction system using acetone, lipid-pigment complexes potentially beneficial for human health such as ferulic acid-conjugated lipids were efficiently extracted. Fatty acid compositions found in RBO prepared by DME extraction and conventional solvent extraction did not differ. Lastly, improvement of the extraction efficiency was attempted by designing a column-based flow system allowing extraction of RBO with an optimized amount of liquefied DME. By this approach, the efficiency of RBO extraction attained ca. 24% (ca. 0.24 g of RBO extracted and recovered from 1 g of dried rice bran), using 10 to 20 g of liquefied DME applied to 1 g of rice bran packed in the column-type extraction chamber.

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Microwave-assisted three-liquid-phase extraction (MATLPE) was applied to extract diosgenin and untransformed saponins in Dioscorea zingiberensis C. H. Wright (DZW) fermentation broth from Trichoderma harzianum. The partitioning behaviours of various steroids were investigated, and the removal of soluble protein, microbial cells and raw herb residuals were studied. A three-liquid-phase system (TLPS) consisting of 30% (w/w) ethanol, 15% (w/w) (NH₄)₂SO₄, 40% (w/w) petroleum ether and water was selected. The optimal microwave extraction parameters were as follows: liquid/solid ratio, 80:1; microwave time, 120 s; and microwave power, 380 W. MATLPE integrated the extraction and separation of diosgenin and the untransformed saponins, the separation of solids and liquids, and the removal of soluble impurities (reducing sugars and proteins) in one step. Compared with other methods, MATLPE consumed smaller amounts of reagents, achieved higher recoveries, and resulted in several-fold higher concentrations of diosgenin and saponin extracts.

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When homogeneous solutions that feature two-phase separation properties, such as a ternary mixed solvent solution of water-acetonitrile-ethyl acetate, are fed into a microspace, such as a capillary tube and a microchannel, the solvent molecules are radially distributed into the microspace, generating inner and outer phases. This is called “tube radial distribution phenomenon” (TRDP). In this study, microflow extraction for the Fe(III)-8-hydroxyquinoline complex was carried out using a microchip incorporating microchannels based on the TRDP. A microchip in which one wide channel was separated into three narrow channels was designed and manufactured. When the ternary mixed solvent solutions of water (acetic acid aqueous solution, pH3.5)-acetonitrile-ethyl acetate (volume ratio 40:45:15) containing Fe(III) and 8-hydroxyquinoline were fed into the wide channel under laminar flow conditions, the solvent molecules were radially distributed in the channel, generating inner (organic solvent-rich) and outer (water-rich) phases. The Fe(III)-8-hydroxyquinoline complex in the carrier solution was distributed between the inner and outer phases due to its hydrophilic nature, and then collected through the three narrow channels. The concentration of Fe(III) in the center narrow channel was greater than those in the two outer narrow channels through extraction with 8-hydroxyquinoline.

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Previously, we investigated bead-type silica gel adsorbents bearing immobilized diglycolamic acid ligands for the recovery of rare earth elements (REEs). Although the ligand-bearing silica gel selectively adsorbs REEs, the ligand loading is limited by the specific surface area of the silica gel. To increase the ligand loading, we have prepared a film-type adsorbent by immobilizing diglycolamic acid ligands on a nonwoven poly(vinyl alcohol) fabric by means of grafting polymerization. Compared with the silica gel adsorbent, the film-type adsorbent showed similar selectivity for a heavy REE, but the adsorption capacity of the film-type adsorbent was 3–4 times that of the silica gel adsorbent because the ligand loading on the former was 3.81 times that on the latter.

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Dimethyl ether (DME), the simplest ether with the formula CH₃OCH₃, is a low-temperature solvent and extraction agent applicable to specialized laboratory procedures as recently demonstrated for extraction of biologically active, flavoring or pungent organic compounds from some biological materials. Due to its low boiling point, DME facilitates the removal of solvent from the samples after extraction. In the present study, we demonstrated the extraction of proteins from juicy or relatively dry vegetable tissues and the distribution of proteins in the dry phase and separated aqueous phase were compared. It is notable that a series of proteins from carrot roots, sized between 84.7 and 33.1 kDa, were detected in the liquid sample extracted by DME, suggesting that DME could be used as an effective extraction solvent for separating the hydrophilic (water soluble) proteins from the crude protein samples. Extraction of water-soluble proteins largely depends on the de-watering action of DME.

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