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Hiluf T. Fissaha,Grace M. Nisola,Francis Kirby Burnea,Jin Yong Lee,Sangho Koo,Soong-Peong Lee,Kim Hern,Wook-Jin Chung 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.81 No.-
Selective recovery of silver ions Ag+ has been a big challenge due to its difficult separation from complexaqueous feed streams. Herein, four novel highly selective 13- to 19-membered thia-crown ethers (TCEs)were successfully developed by intermolecular cyclization of S- and O-containing intermediates. TheTCEs have reactive hydroxyl group(s) for coating on solid supports. To evaluate their ability to captureAg+, the TCEs were coated on polypropylene (PP) membrane (TCE@PP) at high loading ( 280 wt%) viawet-incipient technique with glutaraldehyde acetalization. Adsorption results of all TCE@PP reveal highAg+ capacities with qe 124–179 mg g 1, excellent Ag+ selectivities with Kd 291–778 L g 1 and rapiduptake rate within 1 h. But DH19-TCE4 or 19TCE@PP is the most effective as it achieved 96% Ag+complexation compared with others53–86% at feed Co = 1.5 mM. Density functional theory calculationsreveal that DH19-TCE4 had the closest cavity size (;c = 2.35 Å) with Ag+ (;Ag+ = 2.30 Å), the most negativebinding energy (BE =65.76 kcal mol 1), and the least cavity distortion during Ag+ complexation. Alladsorbents are reusable and stable with consistent performance even afterfive cycles of adsorption/desorption runs. Overall results demonstrate the effectiveness of the synthesis strategies for TCEs andtheir high potential as adsorbents, especially DH19-TCE4, for selective Ag+ recovery from aqueoussources.
( John Edward L. Sio ),( Grace M. Nisola ),( Rosemarie Ann I. Cuevas ),( Khino J. Parohinog ),( Hiluf T. Fissaha ),( Lawrence A. Limjuco ),( Seong-poong Lee ),( Wook-jin Chung ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-
The continuous increase in the number of electronic wastes(e-waste) worldwide has caused awareness to salvage these materials as secondary sources of critical metals. Spent lithium-ion batteries (LIBs) in E-waste, used mobile phones and computers contain Li, Ni, Co, Al, and Mn.Cobalt is considered as a critical metal thatcan be recycled into other materials such as magnets, alloys, electroplating, andin LIB and printed circuit boards (PCBs). Thus, selective Co(II) extraction and recovery from secondary sources is of great importance.Schiff base ligands have so far been used as extractants in liquid-liquid extraction (LLE) for Co(II) recovery. Some examples of Schiff bases are synthesized via condensation of 2-aminothiazoles with substituted benzaldehydes. Synthesis of the ligand for Co(II) adsorption is relatively cheap and convenient. However, Schiff bases are susceptible to acid hydrolysis, especially during desorption of Co(II). Thus, slight modification of the imine group to amine by mild reduction was required to render the ligand acid-resistant while it retains its complexing ability with Co(II). Two starting materials for the synthesis of the Schiff base ligand were prepared, 4-allyloxy-2-hydroxybenzaldehyde (AHB) and 2-amino-4-methylthiazole (ATZ). Condensation reaction between AHB and ATZ was carried out to form the Schiff base product (AHB-ATZ), which was further reduced by NaBH4 (r-AHB-ATZ). All synthetic compounds were confirmed via infrared spectroscopy (FTIR), proton and carbon nuclear magnetic resonance spectroscopy (1H-NMR and <sup>13</sup>C-NMR). While LLE is the conventional system of application, a more practical approach to minimize reagent use and simplify the process is to incorporate r-AHB-ATZ in ion-imprinted polymers (IIPs). IIPs have recently attracted considerable attention in the recovery of metal ions including Co(II). Integration of IIPs with magnetic particles provides the recyclability and reusability of the extracting material after selective adsorption and desorption of Co(II).For the material support, bare magnetite (Fe<sub>3</sub>O<sub>4</sub>) was prepared by co-precipitation method of FeCl<sub>3</sub>/FeCl<sub>2</sub> (2/1) under basic conditions. Its surface was modified with silica by tetraethylorthosilicate(Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>) and alkene by 3- methacryloyloxypropyltrimethoxysilane (Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>-MATES). Then, radical polymerization between the Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>-MATES and r-AHB-ATZ was carried out using azobisisobutyronitrile (AIBN) as radical initiator and ethylene glycol dimethacrylate(EGDMA) as cross-linker in the presence and absence of Co(II) to produce Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>-MATES-IIP and non-ion-imprinted material (Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>-MATES-NIP), espectively.Fe<sub>3</sub>O<sub>4</sub> and its functionalization were characterized by FTIR. Further material characterization and adsorption tests for the selective extraction and recovery of Co(II)are on-going.This work was supported by National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (2017R1D1A1B03028102 and 2017R1A2B2002109) and Ministry of Education (2009-0093816 and 22A20130012051 (BK21Plus)).