• Journal of Powder Materials
• /
• v.29 no.1
• /
• pp.47-55
• /
• 2022

Tungsten carbide is widely used in carbide tools. However, its production process generates a significant number of end-of-life products and by-products. Therefore, it is necessary to develop efficient recycling methods and investigate the remanufacturing of tungsten carbide using recycled materials. Herein, we have recovered 99.9% of the tungsten in cemented carbide hard scrap as tungsten oxide via an alkali leaching process. Subsequently, using the recovered tungsten oxide as a starting material, tungsten carbide has been produced by employing a self-propagating high-temperature synthesis (SHS) method. SHS is advantageous as it reduces the reaction time and is energy-efficient. Tungsten carbide with a carbon content of 6.18 wt % and a particle size of 116 nm has been successfully synthesized by optimizing the SHS process parameters, pulverization, and mixing. In this study, a series of processes for the high-efficiency recycling and quality improvement of tungsten-based materials have been developed.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.31 no.3
• /
• pp.27-34
• /
• 2023

In this study, various plant-based biomass are recycled into carbon materials to employ as anode materials for lithium-ion batteries. Firstly, various biomass of rice husk, chestnut, tea bag, and coffee ground are collected, washed, and ground. The carbonization process is followed under a nitrogen atmosphere at 850℃. The morphological and chemical properties of materials are investigated using FE-SEM, EDS, and FT-IR to compare the characteristic differences between various biomass. It is noticeable that biomass-derived carbon materials vary in shape and degree of carbonization depending on their precursor materials. These materials are applied as anode materials to measure the electrochemical performance. The specific capacities of rice husk-, chetnut-, tea bag-, and coffee ground-derived carbon materials are evaluated as 65.8, 80.2, 90.6, and 104.7 mAh g^-1 at 0.2C. Notably, coffee ground-based carbon exhibited the highest specific capacity owing to the difference in elemental composition and the degree of carbonization. Conclusively, this study suggests the possibility of utilizing as energy storage devices by employing various plant-based biomass into active materials for anodes.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.31 no.1
• /
• pp.57-68
• /
• 2023

In this study, coffee waste was recycled into nitrogen-doped porous carbon fibers as an active material for high-energy EDLC (Electric Double Layer Capacitors). The coffee waste was mixed with polyvinylpyrrolidone and dissolved into dimethylformamide. The mixture was then electrospun to fabricate coffee waste-derived nanofibers (Bare-CWNF), and carbonization process was followed under a nitrogen atmosphere at 900℃. Similar to Bare-CWNF, the as-synthesized carbonized coffee waste-derived nanofibers (Carbonized-CWNF) maintained its fibrous form while preserving the composition of nitrogen. The electrochemical performance was analyzed for carbonized coffee waste (Carbonized-CW)-, carbonized PAN-derived nanofibers (Carbonized-PNF)-, and Carbonized-CWNF-based electrodes in the operating voltage window of -1.0-0.0V, Among the electrodes, Carbonized-CWNF-based electrodes exhibited the highest specific capacitance of 123.8F g^-1 at 1A g^-1 owing to presence of nitrogen and porous structure. As a result, nitrogen-contained porous carbon fibers synthesized from coffee waste showed excellent electrochemical performance as electrodes for high-energy EDLC. The experimental designed in this study successfully demonstrated the recycling of the coffee waste, one of the plant-based biomass that causes the environmental pollution into high-energy materials, also, attaining the ecofriendliness.

• Economic and Environmental Geology
• /
• v.57 no.1
• /
• pp.83-91
• /
• 2024

According to the IEA (2022), global rechargeable battery demand is expected to reach 1.3 TWh in 2040. EV batteries will account for about 80% of this demand, and used EV batteries are expected to be discharged after 30 years. Used EV batteries can be recycled and reused to create new value. They can also resolve one of the most vulnerable parts of the battery supply chain: raw material insecurity. In this study, we analyzed the amount of used batteries generated by EV in Korea and their potential for reuse and recycling. As a result, it was estimated that the annual generation of used batteries for EV began to increase to more than 100,000 in '31 and expanded to 810,000 in '45. In addition, it was found that the market for recycling EV batteries in '45 could be expected to be equivalent to the production of 1 million batteries, and the market for reuse could be expected to be equivalent to the production of 36 Gwh of batteries. On the other hand, according to the plan standard disclosed by the recycling company, domestic used EV batteries can account for 11% of the domestic recycling processing capacity (pre-treatment) ('30). So it will be important to manage the import and export of used batteries in terms of securing raw materials.

• Economic and Environmental Geology
• /
• v.30 no.3
• /
• pp.249-262
• /
• 1997

The Sr and Nd isotopic compositions of two foliated granitic plutons located in the Chonju and Sunchang area were determined in order to reconfirm the intrusion ages of granitoids and to study the sources of granitic magmas. The best defined Rb-Sr isochron for the whole rock samples of the Chonju foliated granite (CFGR) give an age of $284{\pm}12Ma$, suggesting early Permian intrusion age. In contrast, the whole rock Rb-Sr data of the Sunchang foliated granite (SFGR) scatter widely on the isochron diagram with very little variation in the $^{87}Rb/^{86}Sr$ ratios and, therefore, yield no reliable age information. Futhermore they show the concordance of mineral and whole rock Rb-Sr isochron and divide into two linear groups with roughly the same slopes and significantly different $^{87}Sr/^{86}Sr$ ratios, indicating some kind of Rb-Sr distortion in whole rock scale and a difference in source material and/or magmatic evolution between two subsets. The reconstructed isochrons of 243 Ma, which was defined from the proposed data by the omission of one sample point with significantly higher $^{87}Rb/^{86}Sr$ ratio than the others, and 252 Ma, from the combined data of it and some of this study, strongly suggest the possibility that the SFGR was intruded appreciably earlier than had previously been proposed, although the reliability of these ages still questionable owing to high scatter of data points and, therefore, further study is necessary. All mineral isochrons for the investigated granites show the Jurassic to early Cretaceous thermal episode ranging from 160 Ma to 120 Ma Their corresponding initial $^{87}Sr/^{86}Sr$ ratios correlate well with their whole rock data, indicating that the mineral Rb-Sr system of the investigated granites was redistributed by the postmagmatic thermal event during Jurassic to early Cretaceous. The initial ${\varepsilon}Sr$ values for the CFGR (64.27 to 94.81) tend to be significantly lower than those for the SFGR (125.43 to 167.09). Thus it is likely that there is a marked difference in the magma source characteristics between the CFGR and the SFGR, although the possibility of an isotopic resetting event giving rise to a high apparent initial ${\varepsilon}Sr$ in the SFGR can not be ruled out. In contrast to ${\varepsilon}Sr$, both batholiths show a highly resticted and negative values of initial ${\varepsilon}Nd$, which is -14.73 to -19.53 with an average $-16.13{\pm}1.47$ in the CFGR and -14.78 to -18.59 with an average $-17.17{\pm}1.01$ in the SFGR. The highly negative initial ${\varepsilon}Nd$ values in the investigated granitoids strongly suggest that large amounts of recycled old continental components have taken part in their evolution. Furthermore, this highly resticted variation in ${\varepsilon}Nd$ is significant because it requires that the old crustal source material, from which the granitoid-producing melts were generated, should have a reasonably uniform Nd isotopic composition and also quit similar age. Calculated T2DM model ages give an average of $1.83{\pm}0.25Ga$ for CFGR and $1.96{\pm}0.19Ga$ for SFGR, suggesting the importance of a mid-Proterozoic episode for the genesis of two foliated granites. Although it is not possible to determine precisely the source rock compositions for the investigated foliatic granites, the Sr-Nd isotopic evidences indicate that midcrustal or less probably, a lower crustal granulitic source could be the most likely candidate.

• Korean Journal of Mineralogy and Petrology
• /
• v.33 no.4
• /
• pp.407-417
• /
• 2020

The capacity of the designated landfill site for asbestos-containing waste is approaching its limit because the amount of asbestos-containing slate is increasing every year. There is a need for a method that can safely and inexpensively treat asbestos-containing slate in large capacity and at the same time recycle it. A cement kiln can be an alternative for heat treatment of asbestos-containing slate. We intend to develop a pilot scale device that can simulate the high temperature environment of a cement kiln using a high temperature plasma reactor in this study. In addition, this reactor can be used to inactivate asbestos in the slate and to synthesize one of the minerals of cement, to confirm the possibility of recycling as a cement raw material. The high-temperature plasma reactor as a pilot scale experimental apparatus was manufactured by downsizing to 1/50 the size of an actual cement kiln. The experimental conditions for the deactivation test of the asbestos-containing slate are the same as the firing time of the cement kiln, increasing the temperature to 200-2,000℃ at 100℃ intervals for 20 minutes. XRD, PLM, and TEM-EDS analyses were used to characterize mineralogical characteristics of the slate before and after treatment. It was confirmed that chrysotile [Mg3Si2O5(OH)4] and calcite (CaCO3) in the slate was transformed into forsterite (Mg2SiO4) and calcium silicate (Ca2SiO4), a cement constituent mineral, at 1,500℃ or higher. Therefore, this study may be suggested the economically and safely inactivating large capacity asbestos-containing slate using a cement kiln and the inactivated slate via heat treatment can be recycled as a cement raw material.

• Korean Journal of Environmental Agriculture
• /
• v.19 no.1
• /
• pp.51-57
• /
• 2000

Waste newspapers was used as an amendment to adjust the moisture of household food wastes for composting. The mixture of household food wastes and waste newspapers was composted in an especially designed small home composter, where the early fed composting materials were discharged early. The temperature inside composting materials was influenced very much by that of outside, because the composter was not insulated. Accordingly, the higher the outside temperature was, the higher the decomposition rate was. The temperature inside composting materials did not reach to optimum, because the amount of composting materials added in the composter everyday was too little, and it caused too high water content of discharged compost after 15 weeks. Therefore, it was required that the composter must be insulated to maintain the higher temperature. The inorganic compounds$(K_2O,\;CaO,\;MgO,\;P_2O_5)$ and heavy metals(Zn, Cu, Cr, Cd, Hg, As) were accumulated obviously in produced compost, when dry recycled compost was reused as the amendment for adjusting the moisture.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.28 no.2
• /
• pp.139-154
• /
• 2008

The nearly 75% of animal feed materials used for livestock production are imported every year in Korea. Most of imported feed ingredients are concentrated feeds such as com, wheat, soybean, soybean meal, etc. and they are used as the source materials for the production of assorted feed. The imported concentrated feeds are high in nitrogen and phosphorus. Therefore, the consistent import of feed ingredients may cause an increase of nutrient deposit in our agricultural ecosystem. In the current review, it was discussed with the situation of the feed importation and its nutritional composition to evaluate the nutrient load by the imported feeds onto agricultural ecosystem. The nutrient load caused by imported feeds in agricultural environment was compared with the nutrient demand for crop production. The amounts of N, $P_2O_5\;and\;K_2O$ introduced by the imported fteds in Korea were 371, 140 and 143 Ktons. And, the N, $P_2O_5\;and\;K_2O$ loads excreted from imported feeds in livestock were 148, 84 and 86 Ktons of N, $P_2O_5\;and\;K_2O$ and These nutrient loads by the imported feeds are at the percentage of N 52%, $P_2O_5$ 52% and $K_2O$ 42% in the comparison of total nutrient amounts excreted from livestock animals in Korea. The 82.3% of nutrients excreted from livestock was recycled to crop land as compost and liquid fertilizer, and the others were discharged to river after water treatment processing or disposed to ocean. Also, passing through the recycling process far the production of compost and liquid fertilizer, the amount of nutrients was reduced by the ammonia vaporization of livestock feces and urine. Accordingly, N 81, $P_2O_5$ 74 and $K_2O$ 76 Ktons in the nutrients excreted from livestock were estimated to be utilized in the crop land. Consequently, it was estimated that 44, 48 and 69 Ktons of N, $P_2O_5\;and\;K_2O$ were taken up with crops in the consideration of the ratio of mineralization, and the amounts of leached or deposited N, $P_2O_5\;and\;K_2O$ in crop land were estimated to be 37, 27 and 7 Ktons, respectively. It is estimated that 12%, 34% and 48% of N, $P_2O_5\;and\;K_2O$ introduced by the imported feeds were used by crops, and 10%, 34% and 5% of N, $P_2O_5\;and\;K_2O$ were leached or deposited in agricultural ecosystem. Therefore, considering the leached and deposited amounts of N, $P_2O_5\;and\;K_2O$ originated from the imported feed ingredients, the consistent import of feeds may gradually increase the nutrient load onto agricultural ecosystem.

• Applied Chemistry for Engineering
• /
• v.5 no.4
• /
• pp.681-697
• /
• 1994

The enzymatic hydrolysate of gelatin extracted from fish skin was fractionated and recycled through the membrane reactor according to the molecular weight for the purpose of using as functional material. In addition, the enzymatic hydrolysis conditions of gelatin, enzyme stability by membrane and mechanical shear, and effect on the long-term operational stability of the recycle membrane reactor were investigated. Using the pH-drop technique, Alcalase, pronase E and collagenase were identified as the most suitable enzymes for the hydrolysis of fish skin gelatin. The optimum hydrolysis conditions in the 1st-step membrane reactor(1st-SMR) by Alcalase were enzyme concentration 0.2mg/ml, substrate-to-enzyme ratio(S/E) 50(w/w), $50^{\circ}C$, pH 8.0, reaction volume 600ml and flow rate 6.14ml/min. In the 2nd-SMR by pronase E were enzyme concentration 0.3mg/ml, S/E 33(w/w), $50^{\circ}C$, pH 8.0, reaction volume 600ml and flow rate 6.14ml/min. In the case of 3rd-SMR, enzyme concentration 0.1mg/ml, S/E 100(w/w), $37^{\circ}C$, pH 7.5, reaction volume 600ml and flow rate 10ml/min. Decreased enzyme activities by mechanical shear and membrane were 30% and 15% in the 1st-SMR, were 14% and 5% in the 2nd-SMR, and 18% and 8% in the 3rd-SMR, respectively. Under the optimum conditions, the degree of hydrolysis in the 1st, 2nd and 3rd-SMR were 3.5%(Kjeldahl method, 87%), 3.1%(77%) and 2.7%(70%), respectively. The productivity of hydrolysate in the continuous three-step membrane reactor was 430mg per enzyme(mg) for 10 times of volume replacements.

• Journal of Korean Home Economics Education Association
• /
• v.22 no.1
• /
• pp.51-65
• /
• 2010

The purpose of this study was to raise the awareness of LOHAS(Lifestyle of Health and Sustainability) in the secondary school students. We extracted the related contents to LOHAS from the unit of 'The choice and maintenance of clothing' in the second-year's textbook of Technology-Home Economics, and selected the learning subjects. We also developed the new teaching-learning process plan on practical problem focused lesson, and applied them to the eight classes located in Siheung, Gyeonggi-do, for 5 hours per each class. The learning subjects of the teaching-learning process plan included five items as followings; general awareness, organic fashion, natural fabric, recycled material fashion, and natural dyeing, which were related to LOHAS consumption. The overall topic of the teaching-learning process plan was 'What should do to raise the awareness of LOHAS in order to practice LOHAS consumption in the choice of clothing'. Consequently, the results were abtained as follow; The general awareness of LOHAS as well as the awareness of LOHAS consumption in the choice of clothing increased after classes significantly, compared to those before. Thirty-four materials including worksheets, reading materials and teacher's guide could help to raise the awareness of LOHAS. Also these classes enabled the students to raise their awareness of LOHAS, to improve their opinions and attitudes on LOHAS consumption in the choice of clothing, and to take an interest in the lesson of Home-Economics. This study might have the educational significance in that it made the students directly participate in the national and social trend of the awareness of LOHAS, and upgrade their quality as good LOHAS consumers. Also further teaching-learning process plan in Home-Economics are necessary to promote the awareness of LOHAS for better health, environment, and society.