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>

Novel hierarchically dispersed mesoporous silica spheres: effective adsorbents for mercury from wastewater and a thermodynamic study

Ravi, Seenu,Selvaraj, Manickam,Park, Hyun,Chun, Ho-Hwan,Ha, Chang-Sik The Royal Society of Chemistry 2014 NEW JOURNAL OF CHEMISTRY Vol.38 No.8

<P>Novel hierarchically dispersed spherical mesoporous silica (HSMS) was synthesized using a surfactant mixture of fluorocarbon (FC-4), cetyl-trimethyl ammonium bromide (CTAB), and block copolymer Pluronic F127 (PF127). To prepare the thiol-functionalized HSMS (T-HSMS), the synthesized HSMS was functionalized by a co-condensation method using 3-mercaptotrimethoxysilane (3-MPS) as a thiol reagent. The obtained HSMS and T-HSMS possess a cubic morphology with a <I>lm</I>3&cmb.macr;<I>m</I> space group and a particle diameter of 75–200 nm. The HSMS and T-HSMS materials exhibit large free surface areas exceeding 844 and 663 m<SUP>2</SUP> g<SUP>−1</SUP> and pore radii of approximately 3.2 and 3.1 nm, respectively. The synthesized materials were characterized using small angle X-ray scattering, N<SUB>2</SUB>-physisorption studies, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy studies. The efficacy of mercury adsorption by T-HSMS was studied at different temperatures, 283, 298, and 313 K. The obtained results were fitted with a Langmuir adsorption isothermal plot. The changes in the negative Gibbs free energy values for the spontaneity of the process were calculated. Mercury could be successfully desorbed using thiourea in a 2 M HCl solution, and the adsorbents could be subsequently reused without severe loss of their activity after repeated adsorption tests.</P> <P>Graphic Abstract</P><P>Hierarchically dispersed spherical mesoporous silica (HSMS) was easily synthesized using three surfactants (CTAB, PF127 and FC-4). This is then successfully modified with thiol groups and used for mercury adsorption studies. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4nj00418c'> </P>

Facile synthesis of a mesoporous organic polymer grafted with 2-aminoethanethiol for Hg²⁺ removal

Ravi, Seenu,Ahn, Wha-Seung Elsevier 2018 Microporous and mesoporous materials Vol.271 No.-

<P><B>Abstract</B></P> <P>By varying the amount of AlCl<SUB>3</SUB> catalyst, highly interconnected lamella-shaped (IPOP) and spherically structured porous organic polymers (SPOP) were synthesized from terephthaloyl chloride and <I>p</I>-quaterphenyl via the Friedel–Crafts benzoylation reaction. The newly prepared materials were characterized by scanning electron microscopy, N<SUB>2</SUB> adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and tested for Hg<SUP>2+</SUP> removal in water after functionalization with 2-aminoethanethiol (NS). The stability under different pH and temperature conditions was confirmed, and the equilibrium and kinetics of Hg<SUP>2+</SUP> adsorption were examined by varying the contact time, adsorbate concentration, and pH. The maximum adsorption capacities for Hg<SUP>2+</SUP> by IPOP-NS and SPOP-NS were 769 and 526 mg g<SUP>−1</SUP>, respectively, at 25 °C and pH 5, and the adsorption isotherm data conformed well to the Langmuir model. Adsorption equilibrium for IPOP-NS was reached within 10 min and exhibited a remarkable distribution coefficient of 1.06 × 10<SUP>8</SUP> mL g<SUP>−1</SUP>. The kinetics of Hg<SUP>2+</SUP> adsorption followed the pseudo-second-order model. The influence of co-existing ions such as Na<SUP>+</SUP>, K<SUP>+</SUP>, Ca<SUP>2+</SUP>, Pb<SUP>2+</SUP>, Mg<SUP>2+</SUP>, and Fe<SUP>3+</SUP> was also examined. IPOP-NS was superior in overall performance when compared to SPOP-NS and most of the other reported materials. IPOP-NS could be reused for a minimum of 10 consecutive runs without any detectable loss in adsorption capacity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel mesoporous polymers were synthesized (IPOP/SPOP) and grafted with 2-aminoethanethiol (NS). </LI> <LI> IPOP-NS exhibited exceptional Hg<SUP>2+</SUP> capture of 769 mg g<SUP>−1</SUP> in water with fast kinetics. </LI> <LI> IPOP-NS showed high stability in boiling water, aqueous HCl, and NaOH. </LI> <LI> IPOP-NS was reusable 10 cycles without deterioration in adsorption capacities. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

EDTA-functionalized KCC-1 and KIT-6 mesoporous silicas for Nd3+ ion recovery from aqueous solutions

Seenu Ravi,Siqian Zhang,이유리,강경구,김지만,안지환,안화승 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.67 No.-

Ethylenediaminetetraacetic acid (EDTA)-functionalized KIT-6 and KCC-1 mesoporous silicas were prepared via post-synthesis grafting and examined for their ability to promote the recovery of rare earth metal ions such as Nd3+ from an aqueous medium. The obtained adsorption isotherms were fitted to the Langmuir model, which gave a maximum adsorption of Nd3+ ions of 109.8 and 96.5 mg/g for KIT-6-EDTA and KCC-1-EDTA, respectively, at 25 °C and pH 6. The adsorption kinetic profile of KIT-6 was faster than KCC-1. KIT-6 was also proved to be more stable against desorption under acidic regeneration conditions.

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>

Cyclic carbonate synthesis from CO₂ and epoxides over diamine-functionalized porous organic frameworks

Ravi, Seenu,Puthiaraj, Pillaiyar,Ahn, Wha-Seung Elsevier 2017 Journal of CO₂ utilization Vol.21 No.-

<P><B>Abstract</B></P> <P>Porous aromatic polymers functionalized with ethylenediamine (CBAP-1(EDA)) and then complexed with Zn<SUP>2+</SUP> or Co<SUP>2+</SUP> ions (CBAP-1(EDA-Zn)) and (CBAP-1(EDA-Co) were synthesized and applied as a catalyst for the solventless synthesis of cyclic carbonates from CO<SUB>2</SUB> and epoxides. The properties of the catalysts were examined by various analytical techniques. CBAP-1(EDA) alone enabled the high catalytic conversion of epoxides (>98%) to five-membered cyclic carbonates at 130°C under solvent-, metal-, and co-catalyst-free conditions with high selectivity. The catalytic activity of CBAP-1(EDA) was enhanced in the presence of a nucleophile and Lewis acidic metal ion sites. Thus, CBAP-1(EDA) with tetrabutylammonium bromide (TBAB) had shown 98% conversion of epoxide at 80°C and 1MPa CO<SUB>2</SUB> in 8h, whereas CBAP-1(EDA-Zn) and CBAP-1(EDA-Co) with TBAB achieved 96% epoxide conversion in 36h at room temperature (RT). The stability of the catalysts was confirmed by hot-filtering and reusability tests, which demonstrated that the catalysts could be reused for up to five consecutive runs without any noticeable decline in catalytic activity. The synergism between the basic catalytic sites in CBAP-1(EDA) and TBAB and the Lewis metallic sites was explained by the proposed reaction mechanistic pathway covering both high temperature (metal- and halogen-free) and RT conditions (with metal and halogen).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Diamine-functionalized porous polymer and its Zn<SUP>2+</SUP>/Co<SUP>2+</SUP> complexed forms were prepared. </LI> <LI> These catalysts were applied for the CO<SUB>2</SUB> cycloaddition under mild reaction conditions. </LI> <LI> High activity, stability, and reusability of the catalysts were demonstrated. </LI> <LI> Mechanistic pathway was proposed covering different reaction temperature conditions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

EDTA-functionalized KCC-1 and KIT-6 mesoporous silicas for Nd³⁺ ion recovery from aqueous solutions

Ravi, Seenu,Zhang, Siqian,Lee, Yu-Ri,Kang, Kyoung-Ku,Kim, Ji-Man,Ahn, Ji-Whan,Ahn, Wha-Seung Elsevier 2018 Journal of industrial and engineering chemistry Vol.67 No.-

<P><B>Abstract</B></P> <P>Ethylenediaminetetraacetic acid (EDTA)-functionalized KIT-6 and KCC-1 mesoporous silicas were prepared via post-synthesis grafting and examined for their ability to promote the recovery of rare earth metal ions such as Nd<SUP>3+</SUP> from an aqueous medium. The obtained adsorption isotherms were fitted to the Langmuir model, which gave a maximum adsorption of Nd<SUP>3+</SUP> ions of 109.8 and 96.5mg/g for KIT-6-EDTA and KCC-1-EDTA, respectively, at 25°C and pH 6. The adsorption kinetic profile of KIT-6 was faster than KCC-1. KIT-6 was also proved to be more stable against desorption under acidic regeneration conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ethylenediaminetetraacetic acid (EDTA) grafted KIT-6 and KCC-1 was prepared. </LI> <LI> KIT-6-EDTA showed high adsorption capacities for Nd<SUP>3+</SUP> ions in water. </LI> <LI> Adsorption equilibrium, isotherm, and kinetics were investigated. </LI> <LI> KIT-6-EDTA reused for 5 cycles without deterioration in adsorption capacities. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Aminoethanethiol-Grafted Porous Organic Polymer for Hg²⁺ Removal in Aqueous Solution

Ravi, Seenu,Puthiaraj, Pillaiyar,Row, Kyung Ho,Park, Dong-Wha,Ahn, Wha-Seung American Chemical Society 2017 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.56 No.36

<P>A highly porous organic polymer, CBAP-1, was synthesized from terephthaloyl chloride and 1,3,5triphenylbenzene via the Friedel Crafts reaction, and functionalized with either ethylenediamine (EDA) or 2-aminoethanethiol (AET) for Hg2+ removal from water. Both materials were characterized by X-ray diffraction, N-2 adsorption desorption isotherms, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma and elemental analysis, and the stability of the porous polymers under different pH and temperature conditions was examined. The adsorption experiments were carried out by varying contact time, Hg2+ concentration, and system pH to study the adsorption equilibrium and kinetics. The Hg2+ ion -adsorption capacities of CBAP-1(EDA) and CBAP-1(AET) were 181 and 232 mg/g, respectively, at room temperature and pH 5, and the observed adsorption isotherms could be fitted well to the Langmuir model (correlation factor R-2 > 0.99). Under the optimum set of conditions, the adsorption equilibrium for CBAP-1(AET) was reached within a contact time of 10 min; CBAP-1(AET) exhibited an excellent distribution coefficient of greater than 2.41 x 107 mL/g. The adsorption kinetics could be satisfactorily described by a pseudo-second-order model. Hg2+ recovery in the presence of commonly coexisting metal ions such as Nat, Ca+, Mg2+, Pb+, and Fe+ was also investigated. CBAP-1(AET) showed high Hg' selectivity against other ions except Pb'. CBAP-1(AET) was superior to CBAP-1(EDA) in terms of overall performance; it could efficiently remove >96% of Hg' ions in 2 min from a 100 ppm of Hg2+ solution. The material could be reused for 10 consecutive runs with negligible loss in adsorption capacity.</P>

Cycloaddition of CO₂ and epoxides over a porous covalent triazine-based polymer incorporated with Fe₃O₄

Ravi, Seenu,Puthiaraj, Pillaiyar,Park, Dong-Wha,Ahn, Wha-Seung The Royal Society of Chemistry 2018 New journal of chemistry Vol.42 No.15

<P>A highly porous quaterphenyl-containing covalent triazine polymer (QP-CTP) incorporated with iron oxide nanoparticles (Fe3O4@QP-CTP) was synthesized and applied as a catalyst for the cycloaddition of CO2 and epoxides under mild conditions. The synthesized materials were characterized using X-ray powder diffraction, N2 adsorption-desorption isotherm, X-ray photoelectron spectroscopy, transmission electron microscopy, and elemental analysis. The Fe3O4@QP-CTP composite in the presence of tetrabutylammonium bromide showed 95% conversion of epoxides with high selectivity to cyclic carbonates at 50 °C, 0.1 MPa CO2 in 12 h. The reaction kinetics was further improved upon increasing the temperature to 80 °C. The catalyst was easily recovered using a magnet, and its stability was confirmed using a recycle test, which showed that the catalyst could be re-used for a minimum of eight consecutive runs without a noticeable decline in catalytic activity. A plausible mechanistic pathway of the cycloaddition reaction over Fe3O4@QP-CTP was also proposed.</P>

Novel triazine carbonyl polymer with large surface area and its polyethylimine functionalization for CO2 capture

SEENU RAVI,최유진,Wanje Park,Hyug Hee Han,Shiliang Wu,Rui Xiao,배윤상 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.108 No.-

Incorporating high density of nitrogen and amine sites into a proper porous structure is a major considerationfor developing CO2 adsorbents. Herein, a novel triazine carbonyl polymer (TCP) was synthesizedvia one pot Friedel-Crafts reaction and then was post-synthetically functionalized with polyethylimine(PEI) to develop TCP-PEI. The successful syntheses of TCP and TCP-PEI were verified by various characterizations,including FT-IR, XPS, SEM/EDS, and N2 adsorption isotherms at 77 K. The pristine TCP displayedhierarchical pores and a significantly large BET surface area (1940 m2/g), which verified its propriety ofbeing utilized as a support for PEI functionalization. As reasoned, TCP-PEI showed significantly strongerCO2 adsorption than the pristine TCP because of the special interaction between CO2 and PEI. As a result,TCP-PEI exhibited considerably higher CO2/N2 and CO2/CH4 selectivities than TCP. Moreover, it showedalmost identical CO2 adsorption isotherms for 5 consecutive cycles. Developing covalent porous polymerswith both triazine and carbonyl groups and follow-up PEI functionalization would be an efficient strategyfor developing CO2 adsorbents.