Korea’s technical assistance for better governance

노트 : - Paper for International Conference on U.S.-Korea Dialogue on Strategies for Effective Development Cooperation - Organized by Asia Foundation October 17-18, 2011 Seoul, Korea 행사명 : International Conference on U.S.-Korea Dialogue on Strategies for Effective Development Cooperatio

Implementation of concurrent electrolytic generation of two homogeneous mediators under widened potential conditions to facilitate removal of air-pollutants

AbstractElectro-scrubbing is being developed as a futuristic technology for the removal of air-pollutants. To date, only one homogeneous mediator for the removal of air pollutants has been generated in each experiment using a divided electrolytic flow cell in an acidic medium. This paper reports the concurrent generation of two homogenous mediators, one at the anodic half-cell containing an acidic solution and the other at the cathodic half-cell containing a basic solution. The concept was inspired by the change in pH that occurs during water electrolysis in a divided cell. A 10 M KOH electrolyte medium assisted in the electrochemical generation of low valent 14% Co1+ ([CoI(CN)5]4−) mediator formed from reduction of [CoII(CN)5]3− which was accompanied by a change in the solution 'oxidation reduction potential' (ORP) of −1.05 V Simultaneously, 41% of Co3+ was generated from oxidation of CoIISO4 in the anodic half-cell. No change in the solution ORP was observed at the cathodic half-cell when both half-cells contain 5 M H2SO4, and Co3+ was formed in the anodic half-cell. An electro-scrubbing approach based on the above principles was developed and tested on gaseous-pollutants, CH3CHO and CCl4, by Co3+ and Co1+, respectively, with 90 and 96% removal achieved, respectively.</jats:p

Direct Contact Membrane Distillation (DCMD): Experimental Study on the Commercial PTFE Membrane and Modelling

Membrane distillation (MD) is an alternative technology for the separation of mixtures through porous hydrophobic membranes. A commercially available PTFE (polytetrafluoroethylene) membrane was used in direct contact membrane distillation (DCMD) to investigate the effect of module dimensions on performance. Membrane properties, such as liquid entry pressure (LEP), contact angle (CA), pore diameter, effective porosity and pore size distribution, were characterized and used in analysis. A two dimensional (2D) model containing mass, energy, and momentum balance was developed for predicting permeate flux production. Different flow modes including co-current and counter-current flow mode were studied. The effect of linear velocity on permeation flux for both wide and short, and long and narrow module designs was investigated. The mass transfer coefficients for each condition were calculated for comparison of the module designs. The effects of operating parameters such as flow mode, temperature difference, and NaCl concentration were also considered. The simulated results were validated by comparing with experimental results. Good agreement was found between the numerical simulation and the experiments

Electrochemical Analysis of Aqueous Benzalkonium Chloride Micellar Solution and Its Mediated Electrocatalytic De-Chlorination Application

The physicochemical properties of biologically important benzalkonium chlorides (BKCs) and the effects of its structure on the de-chlorination of allyl chloride was studied by electrogenerated [Co(I)(bipyridine)3]+ (Co(I)) using an electrochemical technique. The results of [Co(II)(bipyridine)3]2+ (Co(II)) cyclic voltammetry in the presence of BKC demonstrates Co(II)/Co(III) redox couple for physicochemical analysis of BKC and Co(II)/Co(I) redox couple for catalytic application. Cyclic voltammetry over a range of scan rates and BKC concentrations revealed the BKC-bound Co(II)/Co(III) micelles showed that the identification of cmc and association of the probe Co(II) species, associated more in the hydrophobic region. In addition, change in diffusion coefficient value of Co(II)/Co(III) with BKC concentration demonstrates the association of Co(II) in micellar hydrophobic region. The beneficial effects of BKC could be accounted for by considering the benzyl headgroup-Co (II) precatalyst-volatile organic compounds (VOCs) (allyl chloride here) substrate interaction. Chromatography/mass spectroscopy (GC/MS) revealed 100% complete de-chlorination of allyl chloride accompanied by three non-chloro products. This is the first report of benzyl headgroup-induced micellar enhancement by an electrochemical method, showing that it is possible to use hydrophobic benzyl headgroup-substitution to tune the properties of micelles for various applications

Simple Technical Approach for Perpetual Use of Electrogenerated Ag(II) at Semipilot Scale: Removal of NO and SO₂ as a Model System

The sustainable applicability of Ag(II)/Ag(I) redox mediator was studied in a semipilot-scale system for treatment of model artificial flue gases containing NO and SO₂. Various discontinuous current supplies were tested for their effect on sustainable use of the electrogenerated mediator. Current density, cell volume, number of flow-through cell, and feed flow rates were varied in electrochemical thin layer cells to improve the applicability of the proposed current supply method. Discontinuing current flow every (5/5) min on–off (<i>i</i>_DC5) resulted in improved regeneration capacity of Ag(II) after 15 h. After extended operation (24 h), removal efficiencies of 62% NO and 100% SO₂ were achieved by mediated electrochemical oxidation both individually and simultaneously using the proposed discontinuous current supply, demonstrating the sustainable use of the mediator. This study will be taken as a pretest for long-term sustainability testing of the mediator, Ag(II), during industrial scaling up

Structural and luminescent properties of a tetranuclear cage-type cadmium(II) carboxylate cluster containing a V-shaped water trimer

<p>The structural characterization of tetranuclear cage-type cadmium(II) carboxylate [Cd₄(2-cpida)₂(2,2′-bpy)₆]·(2,2-bpy)·(ClO₄)·3H₂O (<b>1</b>) (2-H₃cpida = <i>N</i>-(2-carboxyphenyl)iminodiacetic acid, 2,2′-bpy = 2,2′-bipyridine) is described. H-bonding interactions between three lattice water molecules form a V-shaped trimer (H₂O)₃, which is stabilized by <b>1</b>. In addition, luminescence investigations revealed that <b>1</b> shows enhanced emissions as compared with free 2-H₃cpida in the liquid state.</p

Studies on Effective Generation of Mediators Simultaneously at Both Half-Cells for VOC Degradation by Mediated Electroreduction and Mediated Electrooxidation

Of the several electrochemical methods for pollutant degradation, the mediated electrooxidation (MEO) process is widely used. However, the MEO process utilizes only one (anodic) compartment toward pollutant degradation. To effectively utilize the full electrochemical cell, an improved electrolytic cell producing both oxidant and reductant mediators at their respective half-cells, which can be employed for treating two pollutants simultaneously, was investigated. The cathodic half-cell was studied first toward maximum [Co^I(CN)₅]^4– (Co⁺) generation (21%) from a [Co^II(CN)₆]^3– precursor by optimizing several experimental factors such as the electrolyte, cathode material, and orientation of the Nafion324 membrane. The anodic half-cell was optimized similarly for higher Co₃(SO₄)₂ (Co³⁺) yields (41%) from a Co^IISO₄ precursor. The practical utility of the newly developed full cell setup, combining the optimized cathodic half-cell and optimized anodic half-cell, was demonstrated by electroscrubbing experiments with simultaneous dichloromethane removal by Co⁺ via the mediated electroreduction process and phenol removal by Co³⁺ via the MEO process, showing not only utilization of the full electrochemical cell, but also degradation of two different pollutants by the same applied current that was used in the conventional cell to remove only one pollutant

Thermal Decomposition Mechanism of Sr(DPM) 2

Barium strontium titanate [(Ba, Sr)TiO 3 : BST] and strontium titanate (SrTiO 3 : STO) are suitable materials for capacitors used in ultralarge-scale dynamic random access memory (DRAM) because they exhibit high dielectric constant and low leakage current. Knowledge of the decomposition mechanism of metal complexes, particularly the sequence of the bond dissociation in the ligand, is important for two reasons. One is because it provides us with basic information to design new metallorganic compounds by modifying the ligand structures so that the compounds are suitable for the MOCVD process. Similarly to our study, Hitchman et al. Experimental Sr(DPM) 2 was purchased from Strem Chemicals and used without further purification. TG behavior of the sample was observed either in N 2 or in the air with Perkin Elmer TGA7. The sample was also analyzed after storage in a desiccator for a year. The cracking patterns of Sr(DPM) 2 were obtained using a mass spectrometer (JEOL, JMS-AX505WA) and the mass signal change was monitored as the sample was heated at the rate of 30ЊC/min. The sample was ionized by the electron impact (EI) method and the scanned mass range was from 1 to 800 m/z. We also monitored the change of the prevailing mass peaks at 130ЊC to understand the oligomerization mechanism of the metal complexes. The FTIR spectrum of the sample was monitored at elevated temperatures in an in situ IR cell which can be evacuated down to 10 Ϫ5 Torr and heated up to 550ЊC. Results and Discussion Thermogravimetric behavior.- When the sample is heated in air, the fall-off temperature of the TG curve is raised by about 60ЊC and the amount of residue at 550ЊC increases to 8% of the initial weight. A close observation of the curve, expanded in an inset, reveals a slight weight loss between 75 and 200ЊC. Accordingly, the sample begins to lose weight at relatively low temperatures in air