This study presents a novel method for addressing the issue of high-concentration contaminants (ammonium, phosphate, antibiotics) in leachate arising from decomposing livestock carcasses. Antibiotics, developed to eliminate microorganisms, often have low biodegradability and can persist in the ecosystem. This research proposes design elements to prevent contamination spread from carcass burial sites. The adsorbents used were low-grade charcoal (an industrial by-product), Alum-based Adsorbent (ABA), and Zeolite, a natural substance. These effectively removed the main leachate contaminants: low-grade charcoal for antibiotics (initial concentration 1.05 mg/L, removal rate 73.4%), ABA for phosphate (initial concentration 2.53 mg/L, removal rate 99.9%), and zeolite for ammonium (initial concentration 38.92 mg/L, removal rate 100.0%). The optimal mix ratio for purifying leachate is 1:1:10 of low-grade charcoal, ABA, and zeolite. The average adsorbent usage per burial site was 1,800 kg, costing KRW 2,000,000 per ton. The cost for the minimum leachate volume (about 12.4 m3) per site is KRW 2,880,000, and for the maximum volume (about 19.7 m3) is KRW 4,620,000. These findings contribute to resolving issues related to livestock carcass burial sites and suggest post-management strategies by advocating for the effective use of adsorbents in leachate purification.

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 highefficiency recycling and quality improvement of tungsten-based materials have been developed.

Cobalt (Co) is mainly used to prepare cathode materials for lithium-ion batteries (LIBs) and binder metals for WC-Co hard metals. Developing an effective method for recovering Co from WC-Co waste sludge is of immense significance. In this study, Co is extracted from waste cemented carbide soft scrap via mechanochemical milling. The leaching ratio of Co reaches approximately 93%, and the leached solution, from which impurities except nickel are removed by pH titration, exhibits a purity of approximately 97%. The titrated aqueous Co salts are precipitated using oxalic acid and hydroxide precipitation, and the effects of the precipitating agent (oxalic acid and hydroxide) on the cobalt microstructure are investigated. It is confirmed that the type of Co compound and the crystal growth direction change according to the precipitation method, both of which affect the microstructure of the cobalt powders. This novel mechanochemical process is of significant importance for the recovery of Co from waste WC-Co hard metal. The recycled Co can be applied as a cemented carbide binder or a cathode material for lithium secondary batteries.

This study aimed to investigate the effect of storage temperature and pressure plate treatment on chemical composition in Prunus mume sugar extracts (PSEs). Green Prunus mume fruit was mixed with an equal amount of commercial sugar and stored at 4 or 25oC for 9 mon with or without a pressure plate. The alcohol contents in PSEs stored at 4oC were lower than those stored at 25oC. The amygdalin contents in PSEs stored at 25oC with pressure plate were significantly low. The sucrose in PSEs was converted into glucose and fructose during storage. The glucose, fructose and total phenol contents in PSEs stored at 25oC were higher compared with those at 4oC. The total soluble solid and polyphenol contents in PSEs were increased at 25oC until 90 d and 4oC until 150 d and then the contents were constant. The total acidity in PSEs stored at 4oC were higher than those at 25oC. These results indicate that storage temperature plays an important role in controlling the alcohol, amygdalin and sucrose contents in Prunus mume sugar extracts (PSEs).

This study was conducted to investigate changes on the quality characteristics of Prunus davidiana sugar extracts (PSEs) by processing conditions. The PSEs were prepared by extraction with commercial sucrose at 4°C or 25°C for 9 months with or without a pressure plate. The quality characteristics of PSEs were analyzed for Bxo, pH, total acidity, Hunter color value, alcohol content, polyphenol content, DPPH radical scaveging activity, and free sugar content. Bxo increased significantly while pH decreased with increased storage period (p<0.05). The PSEs stored at 4oC scored lower than those stored at 25oC for total acidity, alcohol content, and polyphenol contents. The PSEs with pressure plate possessed lower alcohol content and higher polyphenol content and DPPH free radical scavenging activity than those without pressure plate. The sucrose content in PSEs decreased with increased storage period, while glucose and fructose contents increased. These results indicate that by increasing storage period, sucrose in PSEs is decomposed into glucose and fructose, and the quality characteristics of PSEs such as total acidity, alcohol, and polyphenol content depend on processing conditions.

Currently, the Korea Atomic Energy Research Institute (KAERI) is planning to build the Ki-Jang Research Reactor (KJRR) in Ki-Jang, Busan. It is important to safely dispose of low-level radioactive waste from the operation of the reactor. The most efficient way to treat radioactive waste is cement solidification. For a radioactive waste disposal facility, cement solidification is performed based on specific waste acceptance criteria such as compressive strength, free-standing water, immersion and leaching tests. Above all, the leaching test is important to final disposal. The leakage of radioactive waste such as 137Cs causes not only regional problems but also serious global ones. The cement solidification method is simple, and cheaper than other solidification methods, but has a lower leaching resistance. Thus, this study was focused on the development of cement solidification for an enhancement of cesium leaching resistance. We used Zeolite and Loess to improve the cesium leaching resistance of KJRR cement solidification containing simulated KJRR liquid waste. Based on an SEM-EDS spectrum analysis, we confirmed that Zeolite and Loess successfully isolated KJRR cement solidification. A leaching test was carried out according to the ANS 16.1 test method. The ANS 16.1 test is performed to analyze cesium ion concentration in leachate of KJRR cement for 90 days. Thus, a leaching test was carried out using simulated KJRR liquid waste containing 3000 mg·L-1 of cesium for 90 days. KJRR cement solidification with Zeolite and Loess led to cesium leaching resistance values that were 27.90% and 21.08% higher than the control values. In addition, in several tests such as free-standing water, compressive strength, immersion, and leaching tests, all KJRR cement solidification met the waste acceptance or satisfied the waste acceptance criteria for final disposal.

본 연구는 저장기간동안 변화하는 매실주의 아미그달린의 함량 변화를 알아보고자 매실 와인과 매실 침출주를 제조하였다. 매실 와인은 매실과 설탕(1:1)을 섞어 3개월간 숙성한 후 (21°Brix)로 맞춘 뒤, 매실의 유무로 나누어 Saccharomyces cereviea를 첨가해 발효를 진행하여 숙성시켰다. 매실 침출주는 매실과 담금주(30도)를 1:1 비율로 섞어 매실, 매실과 씨를 모두 제거, 씨만 제거한 것으로 나누어 3개월 동안 숙성을 하였다. 매실 와인의 아미그달린 함량은 초기 매실청의 상태로 3개월 저장하였을 때 증가한 것을 볼 수 있었다. 이후 12일 동안의 1차 발효 동안 매실을 제거한 와인은 아미그달린 함량이 감소하였지만, 매실이 남아있는 와인은 아미그달린 함량이 증가하였다. 저장기간이 늘어 16일 동안의 2차 발효 이후에는 아미그달린 함량이 두 와인 모두 감소하였다. 또한 병입 후 3개월 동안 숙성과정에서는 더욱더 감소하였다. 매실 침출주의 아미그달린 함량은 3개월의 침출 과정에서 1개월 이후 크게 증가하였으나 점차 감소하였고, 숙성 과정에서는 매실의 유무에 관계없이 아미그달린 함량은 모두 감소하였다. 일반적으로 저장기간이 길수록 아미그달린의 함량은 줄어들었으나 그 속도를 더욱 줄이기 위해 전처리 연구가 필요하다고 사려된다.

During the decay process of food waste, odor and leachate are generally produced because food is easily decomposed due to its high organic and moisture contents. In this study, various food waste samples, including samples artificially prepared and collected from actual waste containers, were tested to determine odor and leachate production as the samples were decomposed at a constant temperature of 35°C. In the air phase, total volatile organic compounds (TVOCs), acetaldehyde (AA), methyl mercaptan (MM), hydrogen sulfide (H2S), and dimethyl sulfide (DMS) were measured as a function of the decay period for four days. The results of the experiment showed that TVOC and AA were produced at higher concentrations in the actual food waste than in all artificial wastes. The AA concentration accounted for about 90% of the TVOC in all of the waste samples except for the food waste containing meat and fish only. The concentrations of volatile sulfur compounds (VSCs) were generally lower than 100 μg/kg, and the concentration of DMS was the highest among the VSCs. In the waste sample containing meat and fish only; however, the concentration of VSCs increased up to 1,700 μg/kg, and mostly consisted of MM and DMS. Complex odor concentrations were found to be the highest after a decay period of 12-48 hours. In addition, the complex odor was mostly related to VSCs with low odor thresholds rather than the TVOC. The pH values mostly decreased from 5 to 3.5 as the waste samples were in the decomposition periods, while the pH value increased to 6 in the food waste containing meat and fish only. Consequently, odor intensity and leachate production were the highest in the 12-48 hour range as the decomposition started, and thus an appropriate control strategy needs to be implemented based on the waste composition and the decay period.

There has been much interest in recycling electronic wastes in order to mitigate environmental problems and to recover the large amount of constituent metals. Silver recovery from electronic waste is extensively studied because of environmental and economic benefits and the use of silver in fabricating nanodevices. Hydrometallurgical processing is often used for silver recovery because it has the advantages of low cost and ease of control. Research on synthesis recovered silver into nanoparticles is needed for application to transistors and solar cells. In this study, silver is selectively recovered from the by-product of electrodes. Silver precursors are prepared using the dissolution characteristics of the leaching solution. In the liquid reduction process, silver nanoparticles are synthesized under various surfactant conditions and then analyzed. The purity of the recovered silver is 99.24%, and the average particle size of the silver nanoparticles is 68 nm.

Phosphorus is an essential and irreplaceable element for all living organisms and its resource is limited. Significant amount of used phosphorus is collected in sewage treatment plant as sludge. Sludge ash after incineration contains about 10% of phosphorus in dry mass basis, which is comparable to phosphate rocks, and it is an important source of phosphorus recovery. Acid and alkali were used to leach phosphorus from sludge ash and compared for their leaching kinetics and performance. Phosphorus leaching by NaOH was fast and 0.2 N and 2 N NaOH leached 49% and 56% of the total phosphorus in the sludge ash at the L/S ratio of 100. Phosphorus leaching by sulphuric acid and hydrochloric were very fast and most of the phosphorus was leached in 5 minutes. In case of sulphuric acid 95% of the total phosphorus in the sludge ash was leached by 0.2 N at the L/S ratio of 100 and 93% was leached by 1 N at the L/S ratio of 10. 1 N hydrochloric acid leached 99% of the total phosphorus at the L/S ratio of 10. The results showed acids were more effective than alkali for phosphorus leaching from sludge ash and hydrochloric acid leached more phosphorus than sulphuric acid.

This study focuses on the development of an alkaline leaching hydrometallurgy process for the recovery of tungsten from WC/Co hardmetal sludge, and an examination of the effect of the process parameters on tungsten recovery. The alkaline leaching hydrometallurgy process has four stages, i.e., oxidation of the sludge, leaching of tungsten by NaOH, refinement of the leaching solution, and precipitation of tungsten. The WC/Co hardmetal sludge oxide consists of WO3 and CoWO4. The leaching of tungsten is most affected by the leaching temperature, followed by the NaOH concentration and the leaching time. About 99% of tungsten in the WC/Co hardmetal sludge is leached at temperatures above 90oC and a NaOH concentration above 15%. For refinement of the leaching solution, pH control of the solution using HCl is more effective than the addition of Na2S·9H2O. The tungsten is precipitated as high-purity H2WO4·H2O by pH control using HCl. With decreasing pH of the solution, the tungsten recovery rate increases and then decrease. About 93% of tungsten in the WC/Co hardmetal sludge is recovered by the alkaline leaching hydrometallurgy process.

스캐폴드는 손상된 조직을 보호, 지지하고, 세포분화 및 증식을 위한 공간을 임시로 제공하여 조직의 회복을 유도한다. 이에, 스캐폴드막은 생체친화성과 생분해성을을 지녀야 한다. 본 연구에서는 Poly(L-lactide)를 사용하였고, 상전이법을 기초로 하여 스캐폴드막을 제조하였으며, 대형공극을 형성하기 위하여 염 침출법을 복합하여 사용하였다. 그 결과 높은 공극률의 다공성 스캐폴드막을 얻을 수 있었으며, 기존의 여타 방식에 비해 월등히 간단한 방식으로 스캐폴드를 제조할 수 있다는 결론을 얻을 수 있었다.

조직공학이란 손상된 조직에 대한 대체재를 개발, 제조하는 분야이며, 기증자로부터의 조직을 직접 이식하는 방법이 가장 널리 사용되어 왔으나, 최근에는 함성소재로부터의 캐폴드막 제조에 대한 연구가 진행되고 있다. 스캐폴드막은 공극률, 공극직경 및 공극간의 높은 연결성이 요구된다. 이에 대하여 용융주조에 이은 염 침출법이 알려져 있다. 본 연구에서는 용매주조에 이은 염 침출법을 사용하였으며, 이를 통하여 높은 공극률과 공극간의 연결성은 물룬 적합한 공극직경의 우수한 스캐폴드막을 제조하였다.