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Comprehensive Outlook for Liquid–Liquid Separation of Rare Earth Elements
Published in Abhilash, Ata Akcil, Critical and Rare Earth Elements, 2019
The extent of extraction of rare earths shows the trend: R4N+ > R3NH+ > R2NH2+ > RNH3+. In thiocyanate medium, the extraction increases with increase in atomic number, whereas in nitrate medium it declines with increase in atomic number, as observed by Preston and du Preez [26]. They ascribed this observation to the coactions of electrostatic as well as steric effects determining the stability of several RE complexes and the tendencies to get extracted. Aliquat 336 nitrate extracts lighter rare earths in preference to the heavier in nitrate medium. It is different to that of acidic and neutral extractants which extract heavier rare earths more efficiently because of their smaller size. Aliquat 336 has been employed profitably for the separation of yttrium in pure form. This is based on the diverse extraction abilities of rare earths from thiocyanate and nitrate medium [27]. It is fascinating to note that Aliquat 336 was used as extractant for REs prior to its recognition as a room temperature ionic liquid (IL). Across the lanthanide series, with increase in atomic number, the extraction decreases. Because the distribution ratios for the LREE (La–Nd) are higher when extracted by [A336][NO3−], it is beneficial to consider high nitrate concentrations for the extraction. The stripping of REE from the loaded IL phase is easily carried out by water, which is highly advantageous [28].
Evaluation of alginate hydrogel stabilized Pickering emulsion liquid membrane for methylene blue extraction from aqueous solutions
Published in Journal of Dispersion Science and Technology, 2023
The carrier Aliquat 336 (tricaprylmethylammonium chloride) is used in Figure 1 to depict the PELM transport mechanism for methylene blue. The pKa of methylene blue is 3.8. When the pH is kept high, methylene blue is found in a neutral protonated form. The gradient of various anionic and cationic counter-ions between the two water phases, as well as the cationic extractant Aliquat 336, enable methylene blue to be transferred in its cationic state. Aliquat 336 can be produced by third-phase synthesis (or a second organic phase) in systems that use aliphatic diluents. However, the current study did not detect this development. The following is a list of the chemical reactions that occur during the extraction process on the feed and stripping solution sides of the emulsion liquid membrane (ELM):
Recovery of metals from waste electrical and electronic equipment (WEEE) using unconventional solvents based on ionic liquids
Published in Critical Reviews in Environmental Science and Technology, 2018
Nicolas Schaeffer, Helena Passos, Isabelle Billard, Nicolas Papaiconomou, João A.P. Coutinho
Trihexyl(tetradecyl)phosphonium chloride ([P66614]Cl) is a commercially available, non-fluorinated IL consisting of an organophosphorous-based cation with a chloride anion – cf.Figure 5. Due to the four long alkyl chains, [P66614]Cl has no reported surfactant properties, in contrast to some of the shorter alkyl chain quartenary phosphonium salts alternatives, thereby enhancing phase separation (Bradaric, Downard, Kennedy, Robertson, & Yuehui Zhou, 2003). [P66614]Cl functions by an anion exchange mechanism; and it can be used undiluted, eliminating the need for molecular solvents. The extraction experiments have primarily been conducted from aqueous chloride medium. [P66614]Cl IL shows great promise for the extraction of metal ions and has been studied for the extraction of Zn(II), Fe(II/III), Co(II) as well as REE(III), Au(III), Hg(II), Pd(II), Pt(IV), Bi(III), Re(IV) and U(IV). For example [P66614]Cl, or [P66614]Br, extract almost quantitatively Pd(II) and Pt(IV) from aqueous solutions of HCl (Papaiconomou et al., 2015; Kubota et al., 2017). Distribution coefficients as high as 200 for Rh(III) are obtained in aqueous solution containing 1 mol.L−1 HCl, while Rh(III) remains preferentially in the aqueous phases when the concentration of HCl exceeds 6 mol.L−1 (Svecova et al., 2016). Aliquat 336 ([N1888]Cl) is a well-established quaternary ammonium extractant capable of extracting a range of metal ions through anion exchange or formation of a neutral extraction complex (Černá, Volaufová, & Rod, 1992).
Reactive extraction of lactic and acetic acids from leached bed reactor leachate and process optimization by response surface methodology
Published in Environmental Technology, 2023
Debkumar Chakraborty, Sankar Ganesh Palani, Makarand M. Ghangrekar, Jonathan W.C. Wong
Additionally, the acetate and lactate can be back extracted from the extractant-solute complex, thereby regenerating Aliquat 336-MIBK, which can be recycled for the RE process. The results are promising to scale up the in-situ product recovery process for industrial production of AA and LA. Simultaneously, LA and AA extraction from high solid FW increases the economic value due to the various applications described below and the market potential. Extraction of lactate from LBR leachate could decrease the requirement of chemical buffers and enhance the acidogenesis rate and energy recovery efficiency by regulating the redox environment and improving leachate characteristics.