Daejeon Technopark

The rapid increase in electronic waste poses a significant environmental issue, with copper-rich residues considered among the most valuable fractions. Extracting copper of high purity from these materials is critical for advancing sustainable resource utilization. In this work, an oxidative refining approach employing a FeO-CaO-SiO2 slag matrix was investigated to purify copper-bearing sludge. The method facilitated stable slag generation and ensured distinct separation between the metallic phase and slag. Although Fe and Si were removed effectively at relatively low processing temperatures, complete removal of Sn and S occurred only at 1300 °C, with traces of copper oxides persisting in the refined alloy. Overall, the findings suggest that the proposed slag system offers a reliable strategy for producing high-purity copper from secondary sources, underscoring its relevance in sustainable recycling of copper-enriched wastes.

We have developed a remanufacturing process technology that can restore the original performance of the toque converters for passenger car 6-speed automatic transmissions. The suitability of this remanufacturing process technology for performance restoration was verified by comparing the maximum performance efficiency values for three remanufactured torque converters and two original products. In the performance efficiency test, the maximum performance efficiency values of the remanufactured torque converters were 89.00 %, 88.98 %, and 88.51 %, respectively, with an average value of 88.83 %, and the maximum performance efficiency values for the original torque converters were 88.49 % and 88.32 %, respectively, with an average value of 88.41 %. As a result of comparing the maximum performance efficiency values of the remanufactured torque converters with those of the original torque converters, the average maximum efficiency value of the remanufactured products was 0.42 % points higher than that of the original products. Therefore, the suitability of the torque converter remanufacturing process technology developed through this study was verified, and it was found that the remanufactured torque converter was restored to the same or better performance than the original torque converter.

The most general photocatalyst, <TEX>$TiO_2$</TEX> and <TEX>$WO_3$</TEX>, are acknowledged to be ineffective in range of visible light. Therefore, many efforts have been directed at improving their activity such as: band-gap narrowing with non-metal element doping and making composites with high specific surface area to effectively separate electrons and holes. In this paper, the method was introduced to prepare a photo-active catalyst to visible irradiation by making a mixture with <TEX>$TiO_2$</TEX> and <TEX>$WO_3$</TEX>. In the <TEX>$TiO_2-WO_3$</TEX> composite, <TEX>$WO_3$</TEX> absorbs visible light creating excited electrons and holes while some of the excited electrons move to <TEX>$TiO_2$</TEX> and the holes remain in <TEX>$WO_3$</TEX>. This charge separation reduces electron-hole recombination resulting in an enhancement of photocatalytic activity. Added Ag plays the role of electron acceptor, retarding the recombination rate of excited electrons and holes. In making a mixture of <TEX>$TiO_2-WO_3$</TEX> composite, the mixing route affects the photocatalytic activity. The planetary ball-mill method is more effective than magnetic stirring route, owing to a more effective dispersion of aggregated powders. The volume ratio of <TEX>$TiO_2(4)$</TEX> and <TEX>$WO_3(6)$</TEX> shows the most effective photocatalytic activity in the range of visible light in the view point of effective separation of electrons and holes.