• Membrane and Water Treatment
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• v.11 no.1
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• pp.1-10
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• 2020

An understanding of particle-particle interactions in filtration requires studying the detachment as well as the attachment of nanoparticles. Nanoparticles captured in a granular media filter can be released by changing the physicochemical factors. In this study, the detachment of captured silver nanoparticles (AgNPs) in granular media filtration was examined under different ionic strengths, ion type, and the presence or absence of natural organic matter (NOM). Filtration velocity and ionic strength were chosen as the physical and chemical factors to cause the detachment. Increasing filtration velocity caused a negligible amount of AgNP detachment. On the other hand, lowering ionic strength showed different release amounts depending on the background ions, implying a population of loosely captured particles inside the filter bed. Overall detachment was affected by ionic strength and ion type, and to a lesser degree by NOM coating which resulted in slightly more detachment (in otherwise identical conditions) than in the absence of that coating, possibly by steric effects. The secondary energy minimum with Na ions was deeper and wider than with Ca ions, probably due to the lack of complexation with citrate and charge neutralization that would be caused by Ca ions. This result implies that the change in chemical force by reducing ionic strength of Na ions could significantly enhance the detachment compared to that caused by a change in physical force, due to a weak electrostatic deposition between nanoparticles and filter media. A modification of the 1-D filtration model to incorporate a detachment term showed good agreement with experimental data; estimating the detachment coefficients for that model suggested that the detachment rate could be similar regardless of the amount of previously captured AgNPs.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2791-2796
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• 2014

The capture of $SO_2$ at or close to the temperatures of real flue gas is much more attractive in application. In this work, two kinds of ionic liquids (ILs) based on lactate anion were used to absorb $SO_2$ at high temperatures from 100 to $120^{\circ}C$. The ILs show high absorption capacities of over one mol $SO_2$ per mol IL at $110^{\circ}C$. The absorption of $SO_2$ by the ILs based on lactate anion is reversible and the ILs can be reused for the capture of $SO_2$ at high temperatures with high absorption capacity and thermal stability. Furthermore, the absorption mechanism of $SO_2$ by the ILs was studied by FT-IR, $^1H$ NMR and $^{13}C$ NMR spectra. It has been found that there are strong chemical interactions between the ILs and $SO_2$. Also the absorption mechanism is different when there is water present in ILs compared to when there is not.

• Macromolecular Research
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• v.17 no.12
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• pp.987-994
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• 2009

Palladium nanoparticles having cubic silsesquioxanes (POSS) (Pd-POSS) were produced by the reaction of palladium (II) acetate and octa(3-aminopropyl)octasilsesquioxane octahydrochloride (POSS-${NH_3}^+$ in methanol at room temperature. Functionalized multiwalled carbon nanotubes (MWNT-COOH) were prepared by acid treatment of pristine MWNTs. The hybrid nanocomposites of Pd-POSS and MWNT-COOH (Pd-MWNT nanocomposites) were synthesized by self-assembly method via ionic interaction between positively charged Pd-POSS and negatively charged MWNT-$COO^-$. The spherical aggregates of Pd-POSS with a diameter of 40-60 urn were well attached to the surfaces of MWNT-COOH on Silicon wafer. The composition, structure, and surface morphology of Pd-MWNT nanocomposites were studied by UV-vis spectrophotometer, energy dispersive spectrum (EDX), scanning electron microscopy (SEM), and atomic force microscope (AFM).

• Membrane and Water Treatment
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• v.1 no.2
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• pp.93-101
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• 2010

This study examined the effects of feed water chemistry and membrane fouling on the rejection of trace organics by a loose nanofiltration membrane. One ionisable and one non-ionisable trace organics were selected for investigation. Results reported here indicate that the solution pH and ionic strength can markedly influence the removal of the ionisable trace organic compound sulfamethoxazole. These observations were explained by electrostatic interactions between the solutes and the membrane surface and by the speciation of the ionisable compound. On the other hand, no appreciable effects of solution pH and ionic strength on the rejection of the neutral compound carbamazepine were observed in this study. In addition, membrane fouling has also been shown to exert some considerable impact on the rejection of trace organics. However, the underlying mechanisms remain somewhat unclear and are subject to on-going investigation.

• Bulletin of the Korean Chemical Society
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• v.3 no.1
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• pp.34-36
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• 1982

N-Methacryloyl-L-histidine and N-methacryloyl-L-histidine methyl ester were synthesized and polymerized to obtain polymeric catalysts with different functions. In the presence of each of these polymers the solvolytic reactions of p-nitrophenyl acetate (PNPA), 3-nitro-4-acetoxybenzoic acid(NABA), 3-acetoxy-N-trimethylanilinium iodide(ANTI) and 3-nitro-4-decanoyloxybenzoic acid(NDBA) were performed in 20% aqueous ethanol. For the purpose of comparison the low molecular weight analogs(LMWA's), L-histidine, L-histidine methyl ester and N-acetyl-L-histidine were also subjected to catalyze the solvolyses of above substrates. In the solvolysis of PNPA the polymeric catalysts exhibited lower activities than the LMWA's. However the ionic substrates, NABA and ANTI were solvolyzed at anomalous rate by polymeric catalyst, indicating that electrostatic effects are operative in the catalysis by polymers. Furthermore in the solvolysis of hydrophobic monomer NDBA, polymeric catalysts exhibited highly enhanced activities compared with the LMWA's implying that hydrophobic interaction can be the most important contribution to the high catalytic activity of imidazole-containing polymers.

• Polymer(Korea)
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• v.36 no.5
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• pp.656-661
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• 2012

The palladium nanoparticles were self-assembled to make Pd-POSS using POSS-$NH_3{^+}$ (polyhedral oligomeric silsesquioxane) as a crosslinker. Graphene oxide (GO) was produced by the reaction of graphite under a strong acid and oxidizer and poly(acrylic acid) (PAA) was covalently grafted on the surface of graphene to make PAA-grafted graphene through the radical polymerization of acrylic acid and GO along with a reduction process under $NaBH_4$. The nanocomposites of Pd-POSS and PAA-grafted graphene were fabricated via ionic interactions between positively charged Pd-POSS and negatively charged PAA-grafted graphene. Pd-POSS nanoparticles were attached to the surface of PAA-grafted graphene through ionic interactions. The thermal stability of Pd-POSS/PAA-grafted graphene was higher than that of PAA and PAA-grafted graphene. The composition, structure, surface morphology, and thermal stability of the Pd-POSS/PAA-grafted graphene were studied by FE-SEM, AFM, TEM, FTIR, and TGA.

• Journal of the Korean Magnetic Resonance Society
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• v.5 no.2
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• pp.118-129
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• 2001

Binding interactions of cationic porphyrins, T4MPyP and TMAP with DNA oligomer d(CGCGAATTCGCG), were studied with NMR spectroscopy, W and CD spectroscopic method. Two porphyrins showed significant differences in NMR, UV and CD data upon binding to DNA. T4MPyP was considered to position more closely to DNA bases through partial intercalation as well as ionic intercalation between the positive charges of porphyrin and phosphate group of DNA at 5’-GC-3’steps. Contrast to this, TMAP was thought to bind to phosphate of DNA more or less outside of the groove.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.1
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• pp.1-5
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• 2002

A fusion protein, consisting of a human epidermal growth factor (hEGF) as the recognition domain and human angiogenin as the toxin domain, can be used as a targeted therapeutic against breast cancer cells among others. The fusion protein was expressed as inclusion body in recombinant E. coli, and when the conventional, solution-phase refolding process was used the refolding yield was very low due to severe aggregation. It was probably because of the opposite electric charge at a neutral pH resulting from the vastly different pI values of each domain. The solid-phase refolding process that exploited the ionic interactions between ionic exchanger surface and the fusion protein was tried, but the adsorption yield was also very low, below $ 30\%$, regardless of the resins and pH conditions used. Therefore, to provide a higher ionic affinity toward the solid matrix, six lysine residues were tagged to the N-terminus of the hEGF domain. When heparin-Sepharose was used as the matrix, the adsorption capacity increased 2.5-3 times to about $88\%$. Besides the intrinsic affinity of angiogenin to heparin, the poly-lysine tag provided additional ionic affinity. And the subsequent refolding yield increased nearly 13-fold, from ca. $4.8\%$ in the conventional refolding of the untagged fusion protein to $63.6\%$. The process was highly reproducible. The refolded protein in the column eluate retained RNase bioactivity of angiogenin.

• Membrane Journal
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• v.33 no.5
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• pp.240-247
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• 2023

Even among gas separation methods, CO₂ capture and separation via membranes is an ever-growing field, with many different membrane compositions continually being developed. Ionic liquid (IL) based composite membranes show excellent performance values in separating CO₂. Similarly, various copolymer/IL composite membranes also display improved performance. The addition of fillers such as graphene oxide to these copolymer/IL composite membranes shows a further enhanced version of these fillers, most likely due to the strong interactions that occur between ILs and organic fillers, which consequently improves factors such as the affinity, selectivity, and adsorption of CO₂. Copolymer/IL composite membranes utilizing a metal-organic framework (MOF) showed improved CO₂ permeability. This review discusses the study of various combinations of ionic liquid and copolymer composite membranes for carbon dioxide separation.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1519-1526
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• 2010

The behavior of peptide or protein solutes in saline aqueous solution is a fundamental topic in physical chemistry. Addition of ions can strongly alter the thermodynamic and physical properties of peptide molecules in solution. In order to study the effects of added ionic salts on protein conformation and dynamics, we have used the molecular dynamics (MD) simulations to investigate the behavior of Staphylococcus aureus Hfq protein under two different ionic concentrations: 0.1 M NaCl and 1.0 M NaCl in presence and absence of RNA (a hepta-oligoribonucleotide AU5G). Hfq, a global regulator of gene expression is highly conserved and abundant RNA-binding protein. It is already reported that in vivo the increase of ionic strength results in a drastic reduction of Hfq affinity for $Q{\beta}$ RNA and reduces the tendency of aggregation of Escherichia coli host factor hexamers. Our results revealed the crucial role of 0.1 M NaCl Hfq system on the bases with strong hydrogen bonding interactions and by stabilizing the aromatic stacking of Tyr42 residue of the adjacent subunits/monomers with the adenine and uridine nucleobases. An increase in RNA pore diameter and weakened compactness of the Hfq-RNA complex was clearly observed in 1.0 M NaCl Hfq system with bound RNA. Aggregation of monomers in Hfq and the interaction of Hfq with RNA are greatly affected due to the presence of high ionic strength. Higher the ionic concentration, weaker is the aggregation and interaction. Our results were compatible with the experimental data and this is the first theoretical report for the experimental study done in 1980 by Uhlenbeck group for the present system.