Sok Kim

Cinnamon zeylanicum bark extract and powder mediated green synthesis of nano-crystalline silver particles and its bactericidal activity

The exploitation of various plant materials for the biosynthesis of nanoparticles is considered a green technology as it does not involve any harmful chemicals. The present study reports the synthesis of silver (Ag) nanoparticles from silver precursor using the bark extract and powder of novel Cinnamon zeylanicum. Water-soluble organics present in the plant materials were mainly responsible for the reduction of silver ions to nano-sized Ag particles. TEM and XRD results confirmed the presence of nano-crystalline Ag particles. The pH played a major role in size control of the particles. Bark extract produced more Ag nanoparticles than the powder did, which was attributed to the large availability of the reducing agents in the extract. Zeta potential studies showed that the surface charge of the formed nanoparticles was highly negative. The EC(50) value of the synthesized nanoparticles against Escherichia coli BL-21 strain was 11+/-1.72 mg/L. Thus C. zeylanicum bark extract and powder are a good bio-resource/biomaterial for the synthesis of Ag nanoparticles with antimicrobial activity.

Selective biosorption behavior of Escherichia coli biomass toward Pd(II) in Pt(IV)–Pd(II) binary solution

This study reports a new finding that the industrial waste biomass of Escherichia coli is capable of selective binding of Pd(II) in the Pd(II)-Pt(IV) bimetal solution. Batch sorption experiments with E. coli were carried out at different initial metal concentrations in single and bimetal systems. In the single metal systems, the maximum sorption capacities of E. coli for Pt(IV) and Pd(II) were found to be 45.65 ± 2.04 and 38.87 ± 2.08 mg/g, respectively. Meanwhile, in the bimetal system, the maximum sorption capacities for Pd(II) and Pt(IV) were 33.16 ± 1.53 and 7.32 ± 0.29 mg/g, respectively, which corresponded to 4.53 times of selective adsorption toward Pd(II). In order to understand the underlying reason, ion exchange resins (TP214 and Amberjet 4200) with different amine types were compared with the E. coli biomass. As a result, it was found that the sorbents containing primary amine groups could selectively adsorb Pd(II) more easily in the binary mixture.

Removal of heavy metals from aqueous phases using chemically modified waste Lyocell fiber.

In this study, an outstanding performance of chemically modified waste Lyocell for heavy metals treatment is reported. The sorbent, which was prepared by a simple and concise method, was able to bind heavy metals such as Pb(II), Cu(II) and Cd(II), with very high efficiencies. The binding mechanisms were studied through adsorption and standard characterization tests such as scanning electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analyses. Adsorption kinetics was very fast and attained equilibrium within 5 min in all metals studied. The maximum single metal uptakes were 531.29±0.28 mg/g, 505.64±0.21 mg/g, and 123.08±0.26 mg/g for Pb(II), Cd(II) and Cu(II), respectively. In ternary metal systems, Cu(II) selectivity was observed and the underlying factors were discussed. The sorbent by its nature, could be very effective in treating large volumes of wastewater with the contact of very little amount.

Cationic polymer-immobilized polysulfone-based fibers as high performance sorbents for Pt(IV) recovery from acidic solutions.

This work reports a novel concept for the development of a polysulfone (PS)-based fiber as a high-performance acid-tolerant adsorbent for the recovery of platinum group metals (PGMs), particularly Pt(IV), in acidic media. Polyethylenimine (PEI)-coated PS-Escherichia coli biomass composite fiber (PEI-PSBF) was prepared by spinning biomass-PS blends in water, coating with PEI and cross-linking with glutaraldehyde. The E. coli biomass on the fiber was executed as a functional group donor for binding PEI. PS fiber (PSF), PS-biomass composite fiber (PSBF), and PEI-modified PSF (PEI-PSF) were also prepared and compared with PEI-PSBF. The results of SEM and FTIR analyses revealed the presence of PEI on the surface of PEI-PSBF. Kinetic and isotherm experiments showed the negligible sorption capacity of PSF. In contrast, adsorption equilibrium on PSBF and PEI-PSBF was attained after 40 min and 6h, respectively. The maximum Pt(IV) uptake of PEI-PSBF was 6.6 times higher than that of PSBF. Pt(IV) ions were completely recovered from loaded PEI-PSBF by 0.1M thiourea in 1M HCl solution. The PEI-PSBF was also stable in 0.1M and 1M HCl solutions. The PEI-PSBF exhibited promising properties as an adsorbent for PGMs-containing acidic wastewaters.

Pain modality and spinal glia expression by streptozotocin induced diabetic peripheral neuropathy in rats

Pain symptoms are a common complication of diabetic peripheral neuropathy or an inflammatory condition. In the most experiments, only one or two evident pain modalities are observed at diabetic peripheral neuropathy according to experimental conditions. Following diabetic peripheral neuropathy or inflammation, spinal glial activation may be considered as an important mediator in the development of pain. For this reason, the present study was aimed to address the induction of pain modalities and spinal glial expression after streptozotocin injection as compared with that of zymosan inflammation in the rat. Evaluation of pain behavior by either thermal or mechanical stimuli was performed at 3 weeks or 5 hours after either intravenous streptozotocin or zymosan. Degrees of pain were divided into 4 groups: severe, moderate, mild, and non-pain induction. On the mechanical allodynia test, zymosan evoked predominantly a severe type of pain, whereas streptozotocin induced a weak degree of pain (severe+moderate: 57.1%). Although zymosan did not evoke cold allodynia, streptozotocin evoked stronger pain behavior, compared with zymosan (severe+moderate: 50.0%). On the other hand, the high incidence of thermal hyperalgesia (severe+moderate: 90.0%) and mechanical hyperalgesia (severe+moderate: 85.7%) by streptozotocin was observed, as similar to that of zymosan. In the spinal cord, the increase of microglia and astrocyte was evident by streptozotocin, only microglia was activated by zymosan. Therefore, it is recommended that the selection of mechanical and thermal hyperalgesia is suitable for the evaluation of streptozotocin induced diabetic peripheral neuropathy. Moreover, spinal glial activation may be considered an important factor.

Reinforcement of carboxyl groups in the surface of Corynebacterium glutamicum biomass for effective removal of basic dyes

The biomass of Corynebacterium glutamicum was treated with poly(amic acid) to improve the biosorption of Basic Blue 3 (BB3) from aqueous solution. The grafting of poly(amic acid) onto the biomass surface increased the density of the carboxyl groups. The UV-spectrum revealed that strong acidic (pH2) and basic conditions (pH11) resulted in the precipitation of BB3. Therefore, pH edge experiments were conducted only within the range 3-10; these results indicated that electrostatic attraction between carboxyl groups of C. glutamicum and BB3 dye cations was favored under alkaline conditions. From the Langmuir model, poly(amic acid)-modified biomass gave a maximum uptake of 173.6 mg/g at pH 9, compared to 52.8 mg/g by the raw biomass. The biosorption kinetics was found to be fast; with equilibrium attained within 10 min. The increase in the ionic strength strongly affected the uptake of BB3 for both forms of C. glutamicum.

Three degradation pathways of 1-octyl-3-methylimidazolium cation by activated sludge from wastewater treatment process.

The biodegradability and degradation pathways of 1-octyl-3-methylimidazolium cation [OMIM](+) by microbial community of wastewater treatment plant in Jeonju city, Korea were investigated. It was found that [OMIM](+) could be easily degraded by the microbial community. New degradation products and pathways of [OMIM](+) were identified, which are partially different from previous results (Green Chem. 2008, 10, 214-224). For the analysis of the degradation pathways and intermediates, the mass peaks observed in the range m/z of 50-300 were screened by using a tandem mass spectrometer (MS), and their fragmentation patterns were investigated by MS/MS. Surprisingly, we found three different degradation pathways of [OMIM](+), which were separated according to the initially oxidized position i.e. middle of the long alkyl chain, end of the long alkyl chain, and end of the short alkyl chain. The degradation pathways showed that the long and short alkyl chains of [OMIM](+) gradually degraded by repeating oxidation and carbon release. The results presented here shows that [OMIM](+) can be easily biodegraded through three different degradation pathways in wastewater treatment plants.

The Preparation of Modified Industrial Waste Polyacrylonitrile for the Adsorptive Recovery of Pt(IV) from Acidic Solutions

Sorption technique is one of the most effective methods for recovering precious metals from wastewater solutions; however, its main drawbacks of the traditional sorbents are the slow kinetics and relatively low sorption capacities. As a solution, thin sorbent fibers have been highlighted because they can lead to fast adsorption kinetics due to their high surface areas and numerous binding sites. In this sense, the applicability of an industrial waste polyacrylonitrile (PAN) textile was examined to recover Pt(IV) from acid solutions. In order to enrich cationic functional groups on the surface of a PAN textile, the textile was chemically modified via polyethylenmine (PEI) coating. Afterwards, using PEI-coated PAN fiber, batch sorption experiments (isotherms and kinetics) and column experiments were conducted to evaluate its sorption performance toward Pt(IV). It was clearly revealed in column experiments that the PEI-coated waste PAN textile (WPAN) has fast kinetics and good performance for Pt(IV) recovery.