pISSN : 1598-9712 / eISSN : 2288-0690

한국연구재단 등재학술지

Editor-in-Chief : Kim, Jaehoon

Aims and Scope

Clean technology or cleantech includes a broad range of technologies related to reducing energy consumption, waste or environmental pollution through improvements of performance, productivity or energy efficiency. “Clean Technology” was launched in 1995 in order to provide a forum for scientific progress and innovation in cleantech and diffuse them to industries. The Journal covers clean technologies including cleaner production processes, cleaner materials and products, cleaner parts/products design, recycle and reuse of waste materials, cleaner environments, clean energy, industrial ecology, and sustainable management. The Journal is issued quarterly, and also regularly publishes featured reviews on emerging and important industrial subjects of clean technology.

Latest Publication   (Vol. 30, No. 1, Mar.  2024)

Current Status and Management of Nanoplastics Exposed in Environment
Ha-neul Park  Jeonggue Park  Younghun Kim
Nanoplastics (NP) exhibit distinct material properties compared to microplastics (MP), necessitating their separate recognition. Review of research outcomes and policy documents on NP reveals that most policy frameworks predominantly define MPs as solid synthetic polymer materials measuring 5 mm or less, but do not distinguish them from NP. However, recent revisions in regulations by the EU classify NPs as particles that range in size from 1 to 1,000 nm, as confirmed by some academic studies. Research on NPs often relies on experimental investigations centered around water systems, with a focus on high-concentration experimental conditions using spherical polystyrene-based NPs in behavior and impact studies. Notably, the environmental behavior characteristics of NP show differences in influence depending on the NP type, emphasizing the need for field simulation research. These challenges are mirrored in Korean society, so it is necessary to redefine NP to be distinct from MP in both research and policy. This study aimed to assess the current state of NP management globally and domestically and highlight policy considerations and issues in the existing response to NP. Upon comprehensive review, it becomes apparent that reaching an international agreement on MP faces methodological limitations, which could potentially burden efforts to precisely define NP size. Therefore, referencing the EU’s recent regulatory revisions is crucial in domestic policy. Specific adjustments should commence from the MP concept through insights from the domestic industry, guidance from the academic community, and thorough discussions to ensure social acceptance.
Effects of Blended TIPS-pentacene:ph-BTBT-10 Organic Semiconductors on the Photoresponse Characteristics of Organic Field-effect Transistors
Chae Min Park  Eun Kwang Lee
In this study, blended 6,13-Bis(triisopropylsilylethynyl)pentacene (TP):2-Decyl-7-phenyl[1]benzothieno[3,2-b][1] benzothiophene (BT):Poly styrene (PS) TFT at different ratios were explored for their potential application as light absorption sensors. Due to the mixing of BT, both off current reduction and on/off ratio improvement were achieved at the same time. In particular, the TP:BT:PS (1:0.25:1 w/w) sample showed excellent light absorption characteristics, which proved that it is possible to manufacture a high-performance light absorption device. Through analysis of the crystal structure and electrical properties of the various mixing ratios, it was confirmed that the TP:BT:PS (1:0.25:1 w/w) sample was optimal. The results of this study outline the expected effects of this innovation not only for the development of light absorption devices but also for the development of mixed organic semiconductor (OSC) optoelectronic systems. Through this study, the potential to create a multipurpose platform that overcomes the limitations of using a single OSC and the potential to fabricate a high-performance OSC TFT with a fine-tuned optical response were confirmed.
Development of Bismuth Alloy-Based Anode Material for Lithium-Ion Battery
Chi Rong Sun  Jae Hoon Kim
Bismuth is a promising anodic for Li-ion batteries (LIBs) due to its adequate operating voltage and high-volume capacity (3,765 mAh cm-3). Nevertheless, inevitable volume expansion during Bi alloy reactions leads to severe capacity loss and cell destruction. To address this, a complex of bismuth alloy nanoparticles (Bi@NC) embedded in an N doping-carbon coating is fabricated via a simple pyrolysis method. Nano-sized bismuth alloys can improve the reaction dynamics through a shortened Li+- ion diffusion path. In addition, the N-doped carbon coating effectively buffers the volume change of bismuth during the extended alloy/dealloy reaction with Li+ ions and maintains an effective conductive network. Based on the Thermogravimetric analysis (TGA) showed high bismuth alloy loading (80.9 wt%) and maintained a high gravimetric capacity of 315 mAh g-1 up to 100 cycles with high volumetric capacity of 845.6 mAh cm-3.
Pre-leaching of Lithium and Individual Separation/Recovery of Phosphorus and Iron from Waste Lithium Iron Phosphate Cathode Materials
Hee-Seon Kim  Boram Kim  Dae-Weon Kim
As demand for electric vehicles increases, the market for lithium-ion batteries is also rapidly increasing. The battery life of lithium-ion batteries is limited, so waste lithium-ion batteries are inevitably generated. Accordingly, lithium was selectively pre- leached from waste lithium iron phosphate (LiFePO4, hereafter referred to as the LFP) cathode material powder among lithium ion batteries, and iron phosphate (FePO4) powder was recovered. The recovered iron phosphate powder was mixed with alkaline sodium carbonate (Na2CO3) powder and heat treated to confirm its crystalline phase. The heat treatment temperature was set as a variable, and then the leaching rate and powder characteristics of each ingredient were compared after water leaching using Di-water. In this study, lithium showed a leaching rate of approximately 100%, and in the case of powder heat-treated at 800 oC, phosphorus was leached by approximately 99%, and the leaching residue was confirmed to be a single crystal phase of Fe2O3. Therefore, in this study, lithium, phosphorus, and iron components were individually separated and recovered from waste LFP powder.
Numerical Study on Thermochemical Conversion of Non-Condensable Pyrolysis Gas of PP and PE Using 0D Reaction Model
Eunji Lee  Won Yang  Uendo Lee  Youngjae Lee
Environmental problems caused by plastic waste have been continuously growing around the world, and plastic waste is increasing even faster after COVID-19. In particular, PP and PE account for more than half of all plastic production, and the amount of waste from these two materials is at a serious level. As a result, researchers are searching for an alternative method to plastic recycling, and plastic pyrolysis is one such alternative. In this paper, a numerical study was conducted on the pyrolysis behavior of non-condensable gas to predict the chemical reaction behavior of the pyrolysis gas. Based on gas products estimated from preceding literature, the behavior of non-condensable gas was analyzed according to temperature and residence time. Numerical analysis showed that as the temperature and residence time increased, the production of H2 and heavy hydrocarbons increased through the conversion of the non-condensable gas, and at the same time, the CH4 and C6H6 species decreased by participating in the reaction. In addition, analysis of the production rate showed that the decomposition reaction of C2H4 was the dominant reaction for H2 generation. Also, it was found that more H2 was produced by PE with higher C2H4 contents. As a future work, an experiment is needed to confirm how to increase the conversion rate of H2 and carbon in plastics through the various operating conditions derived from this study’s numerical analysis results.
A Study on Heterogeneous Catalysts for Transesterification of Nepalese Jatropha Oil
Youngbin Kim  Seunghee Lee  Minseok Sim  Yehee Kim  Rajendra Joshi  Jong-Ki Jeon
Jatropha oil extracted from the seeds of Nepalese Jatropha curcas, a non-edible crop, was used as a raw material and converted to biodiesel through a two-step process consisting of an esterification reaction and a transesterification reaction. Amberlyst-15 catalyst was applied to the esterification reaction between the free fatty acids contained in the Jatropha oil and methanol. The acid value of the Jatropha oil could be lowered from 11.0 to 0.26 mgKOH/g through esterification. Biodiesel was synthesized through a transesterification reaction between Jatropha oil with an acid value of 0.26 mgKOH/g and methanol over NaOH/c-Al2O3 catalysts. As the loading amount of NaOH increased from 3 to 25 wt%, the specific surface area decreased from 129 to 28 m2/g and the pore volume decreased from 0.249 to 0.129 cm3/g. The amount and intensity of base sites over the NaOH/ c-Al2O3 catalysts increased simultaneously with the NaOH loading amount. It was confirmed that the optimal NaOH loading amount for the NaOH/c-Al2O3 catalyst was 12 wt%. The optimal temperature for the transesterification reaction of Jatropha oil using the NaOH/c-Al2O3 catalyst was selected to be 65 oC. In the transesterification reaction of Jatropha oil using the NaOH/c-Al2O3 catalyst, the reaction rate was affected by external diffusion limitation when the stirring speed was below 150 RPM, however the external diffusion limitation was negligible at higher stirring speeds.
Nanostructure Control of PtNiN/C Catalysts for Oxygen Reduction Reaction by Regulating Displacement Rate of Precursor
Dong-gun Kim  Seongseop Kim  Sung Jong Yoo  Pil Kim
Efforts are actively underway to address the issues related to the high cost of Pt-based catalysts for oxygen reduction reactions by designing high-performance Pt-based alloys through the control of their nanostructures. In this study, a method was proposed to control the nanostructure of Pt-based alloys, either hollow or core-shell, by adjusting the pH of the solution during the galvanic replacement reaction between the carbon-supported nickel-nickel nitride composite and the Pt ions. The physical characteristics, including the state, quantity, and morphology of the metal particles under different preparation conditions, were evaluated through X-ray diffraction, transmission electron microscopy, and inductively coupled plasma. When the prepared catalysts were employed for the oxygen reduction reaction, they exhibited an improvement in area specific-activity compared to a commercial Pt/C, with a 1.7 and 1.9-fold enhancement for the hollow and core-shell structured catalysts, respectively.
Advancing the Frontier in Alkaline Promoter Performance Evaluation: Exploring Simplified Adoption Methods
Wonjoong Yoon  Jiyeon Lee  Jaehoon Kim
In this study, an alkali metal Na was introduced into iron-based catalysts used in the carbon dioxide-based Fischer- Tropsch process by wet impregnation and physical mixing methods to compare their performance. The as-prepared catalysts were evaluated for reactivity at 3.5 MPa, 330 oC, feed ratio of H2/CO2 = 3 with a space velocity of 4,000 mL h-1 gcat-1. Comparing the two catalysts, it was found that Na was uniformly distributed throughout the catalyst when wet-impregnated, but Na for physically mixed catalyst was relatively located on the surface of the catalyst. In addition, the wet-impregnated catalyst showed higher liquid hydrocarbon (C5+) yield and lower CO selectivity. In conclusion, the effect of Na distribution in the catalyst on the reaction was identified and can be controlled by the introduction method.