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Torrejos, Rey Eliseo C.,Nisola, Grace M.,Song, Ho Seong,Han, Jeong Woo,Lawagon, Chosel P.,Seo, Jeong Gil,Koo, Sangho,Kim, Hern,Chung, Wook-Jin Elsevier 2016 Hydrometallurgy Vol.164 No.-
<P><B>Abstract</B></P> <P>A green liquid-liquid extraction (LLE) system was developed for the recovery of lithium (Li<SUP>+</SUP>) from sodium and potassium ions, which are typically present at high concentrations in seawater. Dibenzo-14-crown-4ether (DB14C4) was functionalized with a long lipophilic alkyl C18 chain and a pendent proton ionizable carboxylic acid group to obtain a lithium (Li<SUP>+</SUP>) carrier system (DB14C4-C18-COOH) with high Li<SUP>+</SUP> extraction performance and good stability in the room temperature ionic liquid diluent, CYPHOSIL 109. The Li<SUP>+</SUP> extraction efficiency of DB14C4-C18-COOH/CYPHOSIL 109 can be enhanced by increasing the solution pH and DB14C4-C18-COOH concentration. Further examination of extraction results reveal 1:1 coordination between DB14C4-C18-COOH and Li<SUP>+</SUP> which was also supported by density functional theory calculations. At room temperature, the developed LLE system effectively extracted dilute Li<SUP>+</SUP> from Na<SUP>+</SUP> (selectivity α<SUB>Li</SUB> <SUP>+</SUP> <SUB>/Na</SUB> <SUP>+</SUP> =1954) and K<SUP>+</SUP> (α<SUB>Li</SUB> <SUP>+</SUP> <SUB>/K</SUB> <SUP>+</SUP> =138). Kinetic and thermodynamic parameters were evaluated for optimum Li<SUP>+</SUP> extraction conditions. Sequestered Li<SUP>+</SUP> can be easily recovered from the LLE system using dilute hydrochloric acid. Results from recycling tests showed stable Li<SUP>+</SUP> extraction performance hence it can be used for long term application. Overall results indicate the potential application of DB14C4-C18-COOH/CYPHOSIL 109 as a treatment step to recover Li<SUP>+</SUP> from brine or seawater.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Crown ether in RTIL CYPHOSIL 109 LLE system was developed for Li<SUP>+</SUP> recovery. </LI> <LI> Ligand lipophilic dibenzo14C4 crown ether with ionizable COOH group was synthesized. </LI> <LI> Highly selective LLE towards Li<SUP>+</SUP> in the presence of high Na<SUP>+</SUP> and K<SUP>+</SUP> concentration </LI> <LI> Ligand concentration, solution pH and temperature affected Li<SUP>+</SUP> extraction. </LI> <LI> Convenient Li<SUP>+</SUP> recovery and LLE reusability via dilute acid stripping treatment </LI> </UL> </P>
Limjuco, Lawrence A.,Nisola, Grace M.,Torrejos, Rey Eliseo C.,Han, Jeong Woo,Song, Ho Seong,Parohinog, Khino J.,Koo, Sangho,Lee, Seong-Poong,Chung, Wook-Jin American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.49
<P>Crown ether (CE)-based Li+ adsorbent micro fibers (MFs) were successfully fabricated through a combined use of CE diols, electrospinning, and aerosol cross-linking. The 14- to 16-membered CEs, with varied ring subunits and cavity dimensions, have two hydroxyl groups for covalent attachments to poly(vinyl alcohol) (PVA) as the chosen matrix. The CE diols were blended with PVA and transformed into microfibers via electrospinning, a highly effective technique in minimizing CE loss during MF fabrication. Subsequent aerosol glutaraldehyde (GA) cross-linking of the electrospun CE/PVA MFs stabilized the adsorbents in water. The aerosol technique is highly effective in cross-linking the MFs at short time (5 h) with minimal volume requirement of GA solution (2.4 mL g(-1) MF). GA cross-linking alleviated CE leakage from the fibers as the CEs were securely attached with PVA through covalent CE GA PVA linkages. Three types of CE/PVA MFs were fabricated and characterized through Fourier transform infrared-attenuated total reflection, C-13 cross-polarization magic angle spinning NMR, field emission scanning electron microscope, N-2 adsorption/desorption, and universal testing machine. The MFs exhibited pseudo-second-order rate and Langmuir-type Li+ adsorption. At their saturated states, the MFs were able to use 90-99% CEs for 1:1 Li+ complexation, suggesting favorability of their microfibrous structures for CE accessibility to Lit. The MFs were highly Li+ selective in seawater. Neopentyl-bearing CE was most effective in blocking larger monovalents Na+ and K+, whereas the dibenzo CE was best in discriminating divalents Mg2+ and Ca2+. Experimental selectivity trends concur with the reaction enthalpies from density functional theory calculations, confirming the influence of CE structures and cavity dimensions in their 'size-match' Li+ selectivity.</P>
( Rey Eliseo C. Torrejos ),( Grace M. Nisola ),( Sang Hoon Min ),( Jeong Woo Han ),( Khino J. Parohinog ),( Seongpoong Lee ),( Wook-jin Chung ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-
Dihydroxy-dithia-, -trithia-, and -tetrathia-14-crown-4 ether derivatives (2g-2m) were effectively synthesized by bis-epoxide ring-opening cyclization reaction with 1,2-benzenedithiol using a mild base triethylamine and LiCl as template in water. Experimental liquid-liquid extraction (LLE) and density functional theory (DFT) calculations reveal that the cavity size and denticity of the synthesized thiacrown ethers (CEs) affected their selectivity towards palladium (Pd) and platinum (Pt). Among the CE derivatives, bidentate dihydroxy-dibenzo-dioxadithia-14-crown ether (2i) with a calculated cavity size of 1.58-1.65 Ǻ was most selective towards Pd (1.56 Ǻ) whereas tetradentate dihydroxy-benzo-dimethyl-tetrathia-14-crown-4 ether (2m) with a cavity size of 1.31-1.60 Ǻ towards Pt (1.48 Ǻ), due to the CE cavity size-match relationship. The metals, M<sup>n+</sup> (Pd or Pt) are situated perfectly inside the CE cavity with an S4 CE-M<sup>n+</sup>complex coordination geometry and the lowest DFT calculated binding energies (ΔE<sub>CE-M</sub> <sup>n+</sup>).The dihydroxy thiacrown ethers can be further modified by alkylation for LLE application or polymerized via epoxy functionalization for solid-liquid extraction application of Pd or Pt from highly acidic auto-catalyst leachate. LLE performance of 2i in toluene-water system showed 99.99% Pd extraction efficiency with selectivity up to 10<sup>5</sup> in comparison to other competing metals from highly acidic auto-catalyst leachate. Epoxy-polymerization of epoxide functionalized CEs with diamine as curing agent to afford highly selective adsorbents for Pd or Pt separation were also investigated and showed excellent Pd and Pt separation performance. This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2017R1D1A1B03028102).
Rey Eliseo C. Torrejos,Grace M. Nisola,Sang Hoon Min,Jeong Woo Han,Seong-Poong Lee,Wook-Jin Chung 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.89 No.-
Novel macrocyclic extractants were synthesized and employed in liquid–liquid extraction (LLE) forpalladium/platinum (Pd/Pt) separation in aqueous feed source. Dioxadithia-benzo-crown ether diols(BCES2O2) 2g–2i were prepared through bis-epoxide cyclization with aqueous 1,2-benzenedithiol undermild basic conditions. For improved miscibility and stability in the organic diluent (i.e. toluene), 2g–2iwere alkylated to afford dimethoxy-BCES2O2 3g–3i. LLE experiments reveal their high stability,extraction efficiency, and separation performance (bPd2þ=Pt2þ ¼104105) in highly acidic feed solutions( 6 M HCl). The most suitable extractant 3i followed a 1:1 3i-Pd2+ complex with stability constantKex105. Density functional theory calculations reveal that the rigid cavity size (1.58–1.65 Å) of 3i is idealfor Pd2+ (1.56 Å) in forming S4 coordination geometry. The Pd2+ can be repeatedly extracted by 3i [intoluene] and stripped by 1 M HCl + 0.15 M thiourea solution without performance deterioration. Eachcycle can be accomplished <1 h based on the derived extraction (kex = 0.038 min 1) and stripping(kstrip = 0.063 min 1) rate constants. The high extraction efficiency (99.5%) and purity (98.5%) of recoveredPd2+ from simulated acidic spent automobile catalyst liquor demonstrate the potential of 3i [in toluene]LLE system for selective Pd2+ recovery from automotive wastes.
Design of lithium selective crown ethers: Synthesis, extraction and theoretical binding studies
Torrejos, Rey Eliseo C.,Nisola, Grace M.,Song, Ho Seong,Limjuco, Lawrence A.,Lawagon, Chosel P.,Parohinog, Khino J.,Koo, Sangho,Han, Jeong Woo,Chung, Wook-Jin Elsevier 2017 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.326 No.-
<P><B>Abstract</B></P> <P>Lithium-selective (Li<SUP>+</SUP>) di-hydroxy crown ethers (CEs 3a–3h) were efficiently synthesized via intermolecular cyclization of bulky bis-epoxide with 1,2-dihydroxybenzene. Bis-epoxides were produced by etherifying allyl bromides with bulky diols to afford diene intermediates, which were subsequently epoxidized. Optimized cyclization reactions were established by changing the solvent, catalyst, and reaction temperature. Complexation abilities of CEs 3a–3h with Li<SUP>+</SUP> and other alkali metals (Na<SUP>+</SUP>, K<SUP>+</SUP>, Cs<SUP>+</SUP>) were assessed by liquid-liquid extraction in dichloromethane-water system. Among the CEs, the highest Li<SUP>+</SUP>/Na<SUP>+</SUP> selectivities were obtained from 3d (α<SUB>Li/Na</SUB> =2519) and 3e (α<SUB>Li/Na</SUB> =1768). DFT calculations reveal that 3d (1.28–1.37Å) and 3e (1.23–1.38Å) had the closest cavity sizes with Li<SUP>+</SUP> diameter (1.36Å). This result affirms that the size-match selectivity of CEs with Li<SUP>+</SUP> was due to the presence of bulky tetramethyl (3d) or bicyclopentyl (3e) subunits with the rigid benzo groups. Complexation with larger cations like Na<SUP>+</SUP>, K<SUP>+</SUP> and Cs<SUP>+</SUP> greatly distorted the 3d and 3e rings as indicated by the larger O-M<SUP>+</SUP> distances on their bulky sides than on their benzo sides. Thus, their (3d, 3e) superior selectivities were due to their Li<SUP>+</SUP> preference and unstable complexation with larger M<SUP>+</SUP>. Enthalpy exchange reaction mechanisms reveal the tendency of all CEs to form 2:1 CE-M<SUP>+</SUP> complexes with larger cations except for 3d, which mainly forms 1:1 CE-M<SUP>+</SUP> hence it is considered most suitable for Li<SUP>+</SUP>. The efficient synthesis of di-hydroxy CEs widens their application not only as extractants but also as solid-supported Li<SUP>+</SUP> adsorbents given the amenability of their OH– groups to further functionalization.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Li<SUP>+</SUP> selective crown ethers (CEs) with bulky and rigid subunits were efficiently synthesized. </LI> <LI> Suitable solvents, catalysts, and reaction conditions for CE synthesis were determined. </LI> <LI> Rigid subunits prevented preorganization effect while bulky groups acted as blocking moiety for bigger metals. </LI> <LI> Liquid-liquid extraction and DFT calculations provided insights on CE-M<SUP>+</SUP> complexes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>