Dong-Keun Song

Here, we demonstrate a new strategy of air filtration based on an Al-coated conductive fibrous filter for high efficient nanoparticulate removals. The conductive fibrous filter was fabricated by a direct decomposition of Al precursor ink, AlH3{O(C4H9)2}, onto surfaces of a polyester air filter via a cost-effective and scalable solution-dipping process. The prepared conductive filters showed a low sheet resistance (<1.0 Ω sq(-1)), robust mechanical durability and high oxidative stability. By electrostatic force between the charged fibers and particles, the ultrafine particles of 30-400 nm in size were captured with a removal efficiency of ∼99.99%. Moreover, the conductive filters exhibited excellent performances in terms of the pressure drop (∼4.9 Pa at 10 cm s(-1)), quality factor (∼2.2 Pa(-1) at 10 cm s(-1)), and dust holding capacity (12.5 μg mm(-2)). After being cleaned by water, the filtration efficiency and pressure drop of the conductive filter was perfectly recovered, whic...

In recent years, the worldwide use of polyethylene terephthalate (PET) has increased exponentially. PET wastewater contains ethylene glycol (EG) and terephthalic acid (TPA). In this study, we present a unique method for producing combustible gases like CH4 and H2 from PET wastewater by electrochemical reaction of EG and TPA. The non-diaphragm-based electrochemical (NDE) method was used to treat PET wastewater. The electrochemical removal of EG and TPA from PET wastewater was examined and the optimal conditions for their reduction to CH4 and H2 were determined. Using the proposed system, 99.9% of the EG and TPA present in the PET wastewater samples were degraded to produce CH4 and H2, at applied voltages lower than 5 V. The highest Faradaic efficiency achieved for EG and TPA reduction was 62.2% (CH4, 25.6%; H2, 36.6%), at an applied voltage of 0.8 V. Remarkably, CH4 was produced from EG decomposition and H2 from TPA decomposition. To the best of our knowledge, this is the first repor...

The electrostatic precipitator (ESP) technique is a promising method for enhancing the particulate matter (PM) emission reduction efficiency of diesel engines, and is much better than the diesel particulate filter (DPF) technique. However, the ESP's low efficiency in collecting PM with diameters less than several tens of nanometers remains a problem because the particle charging efficiency decreases as the size of the nanoparticles decreases. To improve the collection efficiency of nanosized PM, we used a photoelectric charger to increase the charging efficiency of nanoparticles ahead of the ESP system. Carbon nanoparticles produced using a spark discharge generator were used to evaluate the collection efficiency of the combined photoelectric charger and ESP system. The particle sizes were measured using a scanning mobility particle sizer system at various experimental temperatures similar to the temperature of DPF systems commonly used in diesel engines. We succeeded in obtaining improved collection efficiencies at increased inner temperatures of the photoelectric charging chamber. As the temperature increased from 694 degrees C to 839 degrees C at the inlet of the photoelectric chamber, the efficiency of PM collection improved significantly to 28.5% for a particle diameter of 18.4 nm.

A loosely focused light beam is very useful for separating colloidal particles. For micron size colloidal particles suspended in a fluid and irradiated with a laser beam perpendicular to the direction of fluid flow, particles have a retention distance determined by their size and composition, the flow rate of fluid, and characteristics of the laser. An optical differential mobility analyzer for separating colloidal particles using a loosely focused beam is proposed theoretically and the concept of optical mobility is introduced. For the proposed optical differential mobility analyzer, particle trajectories and retention behavior are discussed and a transfer function described by operational parameters is derived. The possibility of separating particles of various sizes and different chemical compositions is discussed. It is proposed that the analyzer can be integrated into a microfluidic lab-on-a-chip system suitable for separating colloidal particles and biological cells at a very high resolution.

ABSTRACT Zirconium was newly utilized as a post-treatment material for photoelectrodes in dye-sensitized solar cells (DSSCs), and DSSCs with a high energy conversion efficiency were developed. The Zr oxide-post-treated TiO2 photoelectrodes were prepared by dipping Degussa P25 in a Zr butoxide solution, followed by calcination for 30 min at 475 °C. In the prepared sample, the particle size decreased, and the specific surface area increased, leading to improved dye adsorption. Zr oxide-post-treatment formed ZrO2 on TiO2 surfaces and the electron transport increased by the formation. This post-treatment decreased the recombinant ratio of electrons by reducing resistance in the interparticle electrode/dye/electrolyte. The energy conversion efficiency of Zr oxide-post-treated TiO2 photoelectrodes was 7.03%, which is a 61% improvement over P25 photoelectrodes and is similar to that of TiCl4-post-treated TiO2 photoelectrodes (7.28%). This enhanced energy conversion efficiency could be attributed to the increased surface area, which enabled higher dye loading, and to the improved interparticle connections, which enhanced charge transport and reduced charge recombination.

ABSTRACT Performance of a long differential mobility analyzer (LDMA) in measurements of nanoparticles was evaluated experimentally and numerically. In the evaluation of the LDMA measurements, silver particles in a size range of 5–30 nm were used under an increased flow rate. The numerical calculation method was used for calculating the particle trajectory in the LDMA, and the results were used for a comparison with Stolzenburg's transfer function. Using the CFD method, the flow around the aerosol inlet slit was analyzed, and the resulting particle mobility distribution was compared with that for an ideal flow. The resulting flow effect on the penetration efficiency caused by the inlet and exit slits were negligible when a well-designed system was used. The experimental measurements of mobility distributions were in good agreement with the theoretical prediction of particle size ranges over 10 nm, but some discrepancies were observed when particle size ranges were below 10 nm in size. The numerical calculation estimated the discrepancy found below the 10 nm particle size ranges.