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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.
( Hiluf Tekle Fissaha ),( Grace M. Nisola ),( Wook-jin Chung ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-
Global electronic waste (E-waste) is increasing due to the fast-technological advancement of electrical and electronic devices with short life cycles, and lack of suitable recycling technologies. Inappropriate disposal of these waste materials causes severe environmental impacts. Furthermore, E-waste is attractive for recycling of precious metals like gold and silver, even compared to their mineral ore sources. Many lixiviants and adsorbents have been developed for the recycling of these valuable metals. However, most of the adsorbents are not selective towards specific precious metal ions. Crown ethers (CEs) are attractive macrocyclic complexing agents as their cavity structures can be tailored to accommodate the ionic size of a precious metal and their heteroatoms (i.e. O, N, or S) can be selected to afford the right affinity towards the target ion. In this work, CEs with sulfur donor atoms or thia-CEs (TCEs) were synthesized and proved to form stable complexes with Au<sup>3+</sup> and Ag<sup>+</sup>. The TCEs were prepared by intermolecular cyclization of bulky epoxides with 1,2-benzenedithiol. The TCEs were immobilized on porous polypropylene membrane (PPM) and silica (SBA-15) to enhance their reusability. Different types of composite adsorbents were fabricated containing TCEs with different cavity sizes to render them metal-ion specific.The composite adsorbents were prepared through immobilization of TCEs onto the surface of PPM and SBA-15, respectively. The developed composite adsorbents (TCE@PPMs and TCE@SBA-15) were thoroughly characterized by high-resolution spectroscopic methods such as NMR, HRMS,FTIR,TGA, SEM, XRD and BET. Adsorption experiments reveal the high selectivity of the composite adsorbents towards Au<sup>3+</sup>((αAu<sup>3+</sup>/Pd<sup>2+</sup>= 1.22)and Ag<sup>+</sup>(αAg<sup>+</sup>/M<sup>n+</sup>= 8 - 177) as compared to other cations (M<sup>n+</sup>) present in leached spent mobile PCBs, such as Cu<sup>2+</sup>, Ni<sup>2+</sup>, Zn<sup>2+</sup>, and Pb<sup>2+</sup>. Overall results demonstrate the suitability of the composite adsorbents (TCE@PPM and TCE@SBA-15) for valuable metal recovery applications. This work was supported by National Research Foundation of Korea (NRF) funded by the Ministry of Education (2009-0093816 and 22A20130012051 (BK21Plus)).
( Khino J. Parohinog ),( Hiluf Fissaha ),( Erwin C. Escobar ),( John Edward L. Sio ),( Hern Kim ),( Grace M. Nisola ),( Wook-jin Chung ) 한국폐기물자원순환학회 2022 ISSE 초록집 Vol.2022 No.-
The temperature-responsive Pd<sup>2+</sup>-selective crown ether (Dithia-B18CE6) and N-Isopropylacrylamide (NIPAM) polymer brushes were grafted via SI-ATRP on the acid-stable multi-walled carbon nanotube (MWCNT) support material and was utilized as a Pd<sup>2+</sup>-selective adsorbent. The temperature-responsive composite adsorbent was characterized and tested to determine its Pd<sup>2+</sup> adsorption capacity and kinetics. The adsorbent has high selectivity towards Pd<sup>2+</sup> as compared to other cations present in the simulated catalytic converter leachate solution. Recyclability experiment was done by temperature-swing adsorption-desorption cycles for the capture and release of Pd<sup>2+</sup>. The results demonstrate that the Pd<sup>2+</sup>-selective temperature-responsive adsorbent is effective and suitable for the recovery of Pd<sup>2+</sup> from highly acidic sources.