• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.4 no.4
• /
• pp.298-304
• /
• 1999

Toxic effect of landfill leachate on the larvae and juvenile stage of the river puffer fish, Takifugu obscurus, were investigated in order to assess severity of environmental impact of leachate effluent on the general population of estuarine fishes. A short-term toxic experiment was designed to test both laboratory hatched larvae and juveniles (5, 10 and 15 mm in length) and in-situ juveniles (30 and 45 mm in length) using the leachate concentrations between 0 and 16%. Lethal concentrations of 50% mortality ($LC_{50}$) were observed using Spearman-karber Method. 24hr-$LC_{50}$ appeared at the leachate concentrations ranging from 3.03 to 8.57%, 48hr-$LC_{50}$ at 2.73 to 6.21 %, 72hr-$LC_{50}$o at 2.45 to 5.53%, and 96hr-$LC_{50}$ at 2.38 to 4.93%, respectively. Leachate concentrations between 0.69 and 1.51% induced 96hr-$LC_1$. Respiratory frequency was significantly affected even at low leachate concentrations between 0.5 and 1.0% (P < 0.05). These results suggest that the leachate effluents may cause a harmful impact on the physiology of river puffer fish, especially for younger cohorts.

• Korean Journal of Organic Agriculture
• /
• v.24 no.3
• /
• pp.557-570
• /
• 2016

Growth of 6-year old 'Niitaka' pear (Pyrus pyrifolia Nakai) trees and control of insect and disease occurrences were compared between fermented soybean extracts and rain-shelter system for two years. Foliar application of fermented soybean extracts was applied at 6 times as a pre-experiment in the open-field in 2013, with a rain-shelter system in 2014. Fermented soybean extract treatment increased foliar concentrations of approximately 0.46% T-N, 0.17% K, 0.19% Ca, and 0.06% Mg in 2013 compared to the control, with similar macro-nutrients between the control and soybean extract treatment observed in 2014. Rain-shelter system increased foliar concentrations of T-N, Ca, and Mg compared to the open-field. There were no significantly different between the control and soybean extract treatment for number of leaves per fruit, leaf dry weight, phytotoxicity, and completed shoot growth on August during the two years. Rain-shelter system increased leaf dry weight and did not affect phytotoxicity in the leaves. Fruit quality parameters were mostly similar to control and soybean extract treatment for two years, with higher fruit firmness observed for soybean extract treatment. Rain-shelter system advanced 4 days of harvest dates, and increased approximately 7.0 ton fruit yield per ha, 20 g mean fruit weight, and fruit soluble solid contents compared to open-field in 2014. Soybean extract treatment little suppressed occurrence of disease and insect on the leaves and fruits in both years. Rain-shelter system increased occurrence of Venturia nashicola on the leaves and to 63.8% of Gymnosporangium asiaticum on the fruits in 2014. Strong winds and storms in May elevated relative humidity in the rain-shelter system and caused high infection of the disease occurrence, requiring for an additional green control method. Soybean extract treatment little affected tree growth and would have initiated for a long-term study to evaluate tree physiological characteristics. Rain-shelter system improved fruit productivity and advanced harvest dates, which could have been more effective facility at a Thanks Giving Day between middle and end of September.

• Korean Journal of Soil Science and Fertilizer
• /
• v.40 no.2
• /
• pp.156-163
• /
• 2007

This study was conducted to evaluate the liquefying efficiency of mixed organic fertilizer in different conditions. The organic fertilizer was composed of sesame oil cake, rice bran, fish meal, ground bone meal etc, and made by fermenting process. It included $23g\;kg^{-1}$, $17.0g\;kg^{-1}$, $23.9g\;kg^{-1}$, $290g\;kg^{-1}$ of N, $P_2O_5$, $K_2O$, organic matter, respectively. In one test, the mixed organic fertilizer was added in the proportion of 10% to water 90% and aerated continuously, for 2, 8 hours per day, and not aerated as control. In the other test, ratios of organic fertilizer to water were 5%, 10%, 20% and aerated for 2 hours a day. With the increase of liquefying time, pH, EC and $NH_4-N$ increased without relation to aeration time. After 10 days, liquid organic fertilizer aerated for 2 hours a day contained $634mg\;N\;kg^{-1}$, $68.1mg\;P_2O_5\;kg^{-1}$, $453mg\;K_2O\;kg^{-1}$, which was not significantly different from 8 hours a day or continuous aeration. Then extraction ratios of inorganic contents were 27.6%, 4.0% and 18.9%, respectively. Continuous aeration resulted in increasing the viable number of aerobic bacteria, spore forming bacteria and fungi in liquefied solution. Higher ratio of organic fertilizer to water increased EC, $NH_4-N$ and other inorganic matter contents, but decreased extraction ratio of nutrients in liquid fertilizer. The liquid organic fertilizer of 20% contained $1,140mg\;N\;kg^{-1}$, $35.4mg\;P_2O_5\;kg^{-1}$, $544mg\;K_2O\;kg^{-1}$ after 10 days. Then extraction ratios were 24.8%, 2.4% and 13.6%, respectively. The ratio of organic fertilizer to water was positively correlated with only spore forming bacteria, Pseudomonas spp. among microorganisms.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.28 no.2
• /
• pp.85-90
• /
• 2018

For the recovering rare earths in the spent nickel-metal hydride batteries, 10 M NaOH is added to the solution leached with sulfuric acid. The rare earth powders were precipitated at rate of 98 % at the condition of pH 2.0 or less. The recovered rare earth complex precipitate increased the leaching rate to nitric acid by heat treatment at $800^{\circ}C$ for 4 hours. Subsequently secondary precipitation was performed by adding oxalic acid to the solution in which the rare earth complex precipitate was dissolved. The re-precipitated rare earth powders were converted into oxide form through heat treatment at $800^{\circ}C$ for 4 hours with purity of 99.5 %.

• Resources Recycling
• /
• v.33 no.1
• /
• pp.15-21
• /
• 2024

The demand for electric vehicles powered by lithium-ion batteries is continuously increasing. Recovery of valuable metals from waste lithium-ion batteries will be necessary in the future. This research investigated the effect of reaction temperature on the lithium recovery ratio from hydrogen reduction followed by water leaching from lithium-ion battery NCM-based cathode materials. As the reaction temperature increased, the weight loss ratio observed after initiation increased rapidly owing to hydrogen reduction of NiO and CoO; at the same time, the H₂O amount generated increased. Above 602 ℃, the anode materials Ni and Co were reduced and existed in the metallic phases. As the hydrogen reduction temperature was increased, the Li recovery ratio also increased; at 704 ℃ and above, the Li recovery ratio reached a maximum of approximately 92%. Therefore, it is expected that Li can be selectively recovered by hydrogen reduction as a waste lithium-ion battery pretreatment, and the residue can be reprocessed to efficiently separate and recover valuable metals.

• Journal of the Mineralogical Society of Korea
• /
• v.31 no.2
• /
• pp.67-73
• /
• 2018

The objective of this study was to investigate the application of sulfate solvents for the economic and eco-friendly leaching of valuable metals from Au concentrate using an acid bake-water leaching system (AWS). AWS experiments were performed using an electric furnace with various baking temperatures ($100-500^{\circ}C$) and sulfate solvents ($H_2SO_4$, $K_2SO_4$, $(NH_4)_2SO_4$, $MgSO_4$, and $CaSO_4$). The efficiency of the valuable metal leaching increased as the baking temperature was increased to $400^{\circ}C$. Based on the AWS leaching time experiments, the maximum leaching rate occurred with the aqueous $(NH_4)_2SO_4$ solvent. This study demonstrates that aqueous $(NH_4)_2SO_4$ could be used as an effective solvent for valuable metal leaching using an AWS.

• Journal of Food Hygiene and Safety
• /
• v.35 no.2
• /
• pp.162-169
• /
• 2020

This study was conducted to survey levels of heavy metals, benzopyrene and mycotoxins in teas purchased from online markets, supermarkets, and traditional markets in Gwangju, Korea. We examined the arsenic, cadmium and lead content in heavy metals. We also tested for benzo(a)pyrene, which is classified as a carcinogen. In addition, we tested for the mycotoxins aflatoxin (AFB₁, AFB₂, AFG₁, AFG₂), ochratoxin A (OTA), fumonisin (FUB₁, FUB₂), and zearalenone (ZON). According to our results, heavy metals were detected within the allowable range (below 5.0 mg/kg for lead) and all samples met with the standards for tea as presented in the Korean Food Code. The Benzo(a)pyrene showed a detection rate of 12.8% in 16 of 125 samples and mycotoxins showed 23.2% in 29 of 125 samples. However, safe levels regarding benzo(a)pyrene and mycotoxin in tea were not ascertainable since the standards are not set in the Korean Food Code.

• Resources Recycling
• /
• v.29 no.3
• /
• pp.61-74
• /
• 2020

This study was conducted to improve the recycling process of waste fluorescent lamp, and investigate the possibility of using the waste fluorescent lamp glass as a raw material for glass beads, the leaching method of rare earth from the waste phosphor powder, and the possibility of solvent extraction of rare earth from the rare earth leaching solution. The waste phosphor contained 28.9% yttrium oxide, 3.46% cerium oxide, 1.95% europium oxide, 1.76% terbium oxide, and 1.43% lanthanum oxide. As a result of the trial production of glass beads using waste fluorescent lamp glass, it was judged that the production yield and quality were excellent, so that waste fluorescent lamp glass could be used as a raw material for glass beads. The soda roasted waste phosphor was leached in water and thereby the aqueous solution was blown with CO₂ to drop the pH to about 7, Then, Al, Si and residual N₂CO₃ were dissolved, and NaAlCO₃(OH)₂ and SiO₂ were precipitated in the aqueous solution. In the solvent extraction of cyanex272-hydrochloric acid, cyanex272-sulfuric acid, D2EHPA-hydrochloric acid, D2EHPA-sulfuric acid, Ionquest290-hydrochloric acid, Ionquest290-sulfuric acid, p507-hydrochloric acid using xylene as a diluent, the extraction yield of Y, Eu, Ce, La, and Tb are close to 100%. However, in this conditions, the difference in extraction yield for each element, that is, selectivity is 16% or less.

• Resources Recycling
• /
• v.29 no.5
• /
• pp.38-47
• /
• 2020

In this study, factors affecting the adsorption reaction for the separation/recovery of V and W using Lewatit monoplus MP 600, a strong basic anion exchange resin, from the leachate obtained through the soda roasting-water leaching process from the spent SCR DeNO_X catalyst investigated and the adsorption mechanism was discussed based on the results. In the case of the mixed solution of V and W, both ions showed a high adsorption ratio at pH 2-6, but the adsorption of W was greatly reduced at pH 8. In the adsorption isothermal experiment, both V and W were fitted well at the Langmuir adsorption isotherm, and the reaction kinetics were fitted well at pseudo-second-order. As a result of conducting an adsorption experiment by adjusting the pH with H₂SO₄ to remove Si, which inhibits the adsorption of V and W from the leachate, the lowest W adsorption ratio was shown at pH 8.5. Desorption of W was hardly achieved in strongly acidic solutions, and desorption of V was well performed in both strongly acidic and strongly basic solutions.

• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.2
• /
• pp.207-215
• /
• 2006

This study evaluated the effect of ultrasonic irradiation on reducing membrane fouling for the treatment of chemically treated leachate and biologically treated leachate. The experiments on improvement of membrane flux according to the membrane types(MF and UF) and membrane materials were performed with changing frequency(40 kHz and 120 kHz) and intensity(200 W and 400 W) of ultrasound in ultrasonic membrane separation apparatus which ultrasound can be periodically irradiated. Additionally, the effect of dual frequency ultrasound which 40 kHz md 120 kHz are irradiated simultaneously was evaluated. The improvement of membrane flux by periodical ultrasound irradiation was higher in microfiltration(MF) membrane than in ultrafiltration(UF) membrane. It was sustained more in the MF membrane of polyvinylidene fluoride(PVDF) than in that of polysulfon(PS). Ultrasonic improvement of membrane flux was different depending on the characteristics of target wastewater. It was sustainably maintained without reclogging using dual frequency ultrasound although the improvement of membrane flux was lower.