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( 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)).
Organic ligands for the development of adsorbents for Cs+ sequestration: A review
Erwin C. Escobar,John Edward L. Sio,Rey Eliseo C. Torrejos,Hern Kim,Wook-Jin Chung,Grace M. Nisola 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.107 No.-
Sorbents utilizing organic molecules as Cs+-selective ionophores have increasingly gained attention overthe years as the need for stable and reusable materials became ever more apparent with the poor performanceof inorganic sorbents in acidic and alkaline aqueous environments. Aside from this, organic moleculesoffer a great degree of flexibility in terms of structure, function, and performance which can beharnessed for sorbent development. As such, various kinds of organic ligands have been employed forsorbent preparation, which include macrocycles like calixarenes and crown ethers, and acyclic moleculeslike tetraphenylborate and resorcinol formaldehyde. In this review, organic-based sorbents and ligandsfor Cs+ are described and compared, and the mechanisms underlying their efficacy for Cs+ sequestrationare discussed. Improvements to ligand and sorbent development are proposed to address issues onadsorption selectivity, capacity, and material reusability. Moreover, a platform for the preparation ofstimuli-responsive ligands and sorbents is presented.
( Erwin C. Escobar ),( Wook-jin Chung ),( John Edward L. Sio ),( Khino J. Parohinog ),( Hern Kim ),( Grace M. Nisola ) 한국폐기물자원순환학회 2022 ISSE 초록집 Vol.2022 No.-
A thia-functionalized polymeric adsorbent was prepared for the recovery of Pd<sup>2+</sup> and Pt<sup>4+</sup>. The adsorbent is hydrophilic with a negative surface charge across a wide pH range, and exhibits a highly porous morphology resulting in a high BET surface area (643.47 ㎡ g<sup>-1</sup>). When applied to autocatalyst leachate, selective recovery of Pd<sup>2+</sup> and Pt<sup>4+</sup> may be achieved at pH 1 and pH 4, respectively. Maximum recovery of Pd<sup>2+</sup> can be achieved within 10 min of adsorption with a very high sequestration capacity of 370 mg g<sup>-1</sup>. On the other hand, 70 mg g<sup>-1</sup> Pt<sup>4+</sup> can be recovered within 60 min. The polymeric adsorbent withstands acid-stripping procedures allowing for its repeated use and regeneration. This study was supported by the National Research Foundation of Korea (NRF) funded by The Ministry of Science and ICT (2021R1A2C2093746 and 2020R1A2C1003560) and Basic Science Research Program through the Ministry of Education (2020R1A6A1A03038817)
( 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.