Selective Adsorption of Rare Earth Elements over Functionalized Cr-MIL-101

Lee, Yu-Ri,Yu, Kwangsun,Ravi, Seenu,Ahn, Wha-Seung American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.28

<P>Efficient rare earth elements (REEs) separation and recovery are crucial to meet the ever-increasing demand for REEs extensively used in various high technology devices. Herein, we synthesized a highly stable chromium-based metal-organic framework (MOF) structure, Cr-MIL-101, and its derivatives with different organic functional groups (MIL-101-NH<SUB>2</SUB>, MIL-101-ED (ED: ethylenediamine), MIL-101-DETA (DETA: diethylenetriamine), and MIL-101-PMIDA (PMIDA: <I>N</I>-(phosphonomethyl)iminodiacetic acid)) and explored their effectiveness in the separation and recovery of La<SUP>3+</SUP>, Ce<SUP>3+</SUP>, Nd<SUP>3+</SUP>, Sm<SUP>3+</SUP>, and Gd<SUP>3+</SUP> in aqueous solutions. The prepared materials were characterized using various analytical instrumentation. These MOFs showed increasing REE adsorption capacities in the sequence MIL-101 < MIL-101-NH<SUB>2</SUB> < MIL-101-ED < MIL-101-DETA < MIL-101-PMIDA. MIL-101-PMIDA showed superior REE adsorption capacities compared to other MOFs, with Gd<SUP>3+</SUP> being the element most efficiently adsorbed by the material. The adsorption of Gd<SUP>3+</SUP> onto MIL-101-PMIDA was examined in detail as a function of the solution pH, initial REE concentration, and contact time. The obtained adsorption equilibrium data were well represented by the Langmuir model, and the kinetics were treated with a pseudo-second-order model. A plausible mechanism for the adsorption of Gd<SUP>3+</SUP> on MIL-101-PMIDA was proposed by considering the surface complexation and electrostatic interaction between the functional groups and Gd<SUP>3+</SUP> ions under different pH conditions. Finally, recycling tests were carried out and demonstrated the higher structural stability of MIL-101-PMIDA during the five adsorption-regeneration runs.</P> [FIG OMISSION]</BR>

Pd nanoparticles on a dual acid-functionalized porous polymer for direct synthesis of H2O2: Contribution by enhanced H2 storage capacity

Pillaiyar Puthiaraj,Kwangsun Yu,Wha-Seung Ahn,정영민 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.81 No.-

Direct synthesis of H2O2 from H2 and O2 can avoid the energy and environmental problems of currentmulti-step anthraquinone oxidation process by enabling high atom utilization and generating only awater by-product. However, the direct process suffers a low H2O2 yield, and it is challenging to suppressthe unfavorable side-reactions in the absence of corrosive additives under the restriction of explosionlimits. In this study, an efficient new catalyst was prepared by immobilizing Pd nanoparticles (NPs) on anacidic hyper-crosslinked porous polymer (HCPP). The Pd catalyst supported on HCPP functionalized withboth carboxylic and sulfonic acids (Pd/c-s-HCPP) achieved as high as 3130 mmol H2O2/g Pd.h with 82%selectivity to H2O2, which corresponded to one of the best catalysts reported so far. Pd/c-s-HCPP showedsuperior catalytic performance when compared with ones by Pd NPs supported on unfunctionalizedHCPP (Pd/HCPP), or sulfonated resin (Pd/SO3H-resin). Extensive characterizations and H2 adsorptionmeasurements indicated that the c-s-HCPP provided (i) selective adsorption sites for Pd precursors, (ii)acted as an efficient H2 reservoir in the proximity of the small Pd NPs formed, and (iii) imparts solidacidity to enhance H2O2 selectivity, which offered a new direction in the catalyst design for the directsynthesis of H2O2.

Porous Covalent Organic Polymers Comprising a Phosphite Skeleton for Aqueous Nd(III) Capture

Ravi, Seenu,Puthiaraj, Pillaiyar,Yu, Kwangsun,Ahn, Wha-Seung American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.12

<P>In order to meet the ever-increasing industrial demand for rare-earth elements (REEs), it is desirable to separate and recycle them at low concentrations from various sources including industrial and urban wastes. Here, we introduced phosphorus binding sites on the hydrophobic surface of a robust and high-surface area porous polymer backbone for environmentally benign and selective recovery of REEs via adsorption. For this purpose, two porous covalent organic polymer (COP) materials incorporated with in-built phosphite functionality (P-COP-1 and P-COP-2) were synthesized and applied for the adsorptive separation of Nd(III) ions from aqueous solution. A strategy to develop a series of P-COPs via a simple Friedel-Crafts reaction was introduced, and their application to the selective adsorption of REEs was explored for the first time. The newly synthesized P-COPs were amorphous and/or weakly crystalline and showed excellent chemical stability and large specific surface area with sufficient mesoporosity for enhanced diffusion of REE ions. P-COP-1 exhibited an exceptionally high Nd(III) adsorption capacity of 321.0 mg/g, corresponding to the stoichiometric ratio of P/Nd(III) = 1:0.7 and high selectivity of >86% over other competing transition and alkaline earth metal ions, whereas P-COP-2 gave a Nd(III) adsorption capacity of 175.6 mg/g at 25 °C and pH 5. Moreover, P-COP-1 showed a distribution coefficient value of 5.45 × 10<SUP>5</SUP> mL/g, which is superior to other benchmark adsorbent materials reported so far. Finally, the P-COPs were reusable for a minimum of 10 cycles without deterioration in adsorption capacities.</P> [FIG OMISSION]</BR>

Benzene triamido-tetraphosphonic acid immobilized on mesoporous silica for adsorption of Nd³⁺ ions in aqueous solution

Ravi, Seenu,Lee, Yu-Ri,Yu, Kwangsun,Ahn, Ji-Whan,Ahn, Wha-Seung Elsevier 2018 Microporous and mesoporous materials Vol.258 No.-

<P><B>Abstract</B></P> <P>Mesoporous silica SBA-15 grafted with benzene-1,3,5-triamido-tetraphosphonic acid (SBA-15-BTATPA) was synthesized. After detailed characterization of the material using various analytical instrumentation, it was applied for the recovery of Nd<SUP>3+</SUP> as a function of the contact time, ion concentration, and pH. The adsorption equilibria and kinetics were also examined. Under the optimal conditions, adsorption equilibrium was reached within 60 min of contact time, and the adsorption capacity of Nd<SUP>3+</SUP> at room temperature and pH 6 was 129.8 mg g<SUP>−1</SUP>, which was higher than that by other rare earth element (REE) ions tested for comparison (Y<SUP>3+</SUP>, La<SUP>3+</SUP>, and Ce<SUP>3+</SUP>). The adsorbent showed excellent distribution coefficient for Nd<SUP>3+</SUP> greater than 1.0 × 10<SUP>5</SUP> mL/g. The preferential order of adsorption in the ion mixture with equal ion concentrations was Y<SUP>3+</SUP>>Nd<SUP>3+</SUP>>Ce<SUP>3+</SUP>>La<SUP>3+</SUP>, which followed the sequence of their decreasing atomic size and increasing stability constant. The competing adsorption by transition metal ions, such as Cu<SUP>2+</SUP>, Ni<SUP>2+</SUP>, Co<SUP>2+</SUP>, and Zn<SUP>2+</SUP>, on the REEs recovery was negligible (<2%). The observed adsorption isotherms could be fitted well to a Langmuir model (correlation factor R<SUP>2</SUP> > 0.99), whereas the adsorption kinetics could be described satisfactorily by a pseudo second order kinetic model. The material was reusable for up to 5 consecutive times with only a slight decrease in adsorption capacity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Benzene triamido-tetraphosphonic acid grafted SBA-15 (SBA-15-BTATPA) was prepared. </LI> <LI> SBA-15-BTATPA showed high adsorption capacities for Nd<SUP>3+</SUP> ions in water. </LI> <LI> Adsorption equilibrium, kinetics, and ion selectivity were investigated. </LI> <LI> SBA-15-BTATPA reused for 5 cycles without deterioration in adsorption capacities. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Gd³⁺ Adsorption over Carboxylic- and Amino-Group Dual-Functionalized UiO-66

Ahmed, Imteaz,Lee, Yu-Ri,Yu, Kwangsun,Bhattacharjee, Samiran,Ahn, Wha-Seung American Chemical Society 2019 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.58 No.6

<P>Owing to the growing industrial demand worldwide and limited mineral deposits, the recovery of low-concentration rare earth elements (REEs) from waste sources is being considered, which also helps to reduce water pollution. In this work, the adsorption of gadolinium ions (Gd<SUP>3+</SUP>) in aqueous solutions over a functionalized metal-organic framework (MOF), UiO-66, was investigated. Initially, the MOF structure was synthesized solvothermally using a ligand mixture of terephthalic and trimellitic acids to produce coordination-free −COOH groups on the UiO-66 framework. Subsequently, the −COOH group was reacted with ethylenediamine to introduce additional −NH<SUB>2</SUB> groups onto the MOF. The optimized product (denoted as UiO-66-COOH-ED) showed an equilibrium adsorption capacity of 79 mg/g for Gd<SUP>3+</SUP> compared with 16 mg/g by pristine UiO-66. This improvement in adsorption by a factor of 4.9 was a consequence of the coordination of Gd<SUP>3+</SUP> ions with the electron-abundant oxygen and nitrogen atoms of −COOH and −NH<SUB>2</SUB> groups. A solution pH between 6.0 and 7.0 was found to be the best for Gd<SUP>3+</SUP> capture, and a selectivity of 75% toward Gd<SUP>3+</SUP> was observed against other competing alkali or transition metal ions coexisting in the solution. UiO-66-COOH-ED was reusable for at least five cycles without any noticeable deterioration in its adsorption capacity.</P> [FIG OMISSION]</BR>

A Study of Pd Doped V-W/TiO₂ Catalyst for Simultaneous Removal of NO<SUB>x</SUB> and CO

Jeongtak Kim(김정탁),Sun-Mi Hwang(황선미),Kwangsun Yu(유광선),Hermawan Prajitno(프라짓노 헤르마완),Kyuchul Shin(신규철),Soon Kwan Jeong(정순관) 한국에너지기후변화학회 2022 한국에너지기후변화학회 학술대회 Vol.2022 No.10

미세먼지 저감을 위한 광역온도 대응 질소산화물 저감 촉매 기술

황선미(Sun-Mi Hwang),김정탁(Jeongtak Kim),유광선(Kwangsun Yu),정순관(Soon Kwan Jeong) 한국에너지기후변화학회 2022 한국에너지기후변화학회 학술대회 Vol.2022 No.10

러번(Rurban) 지역 실태와 발전 과제

정문수(Jung Moonsoo),심재헌(Sim Jaehun),김광선(Kim Kwangsun),유은영(Yu Eunyoung) 한국농촌경제연구원 2022 한국농촌경제연구원 기본연구보고서 Vol.2022 No.-