Disposable masks manufactured in response to the COVID-19 pandemic have caused environmental problems due to improper disposal methods such as landfilling or incineration. To mitigate environmental pollution, we suggest a new process for recycling these disposable masks for ultimate application as a conductive material in lithium-ion batteries (LIBs). In our work, the masks were chemically processed via amine functionalization and sulfonation, followed by carbonization in a tube furnace in the Ar atmosphere. The residual weight percentages, as evaluated by thermogravimetric analysis (TGA), of the chemically modified masks were 30.6% (600 °C, C-600), 24.5% (750 °C, C-750), and 24.1% (900 °C, C-900), respectively, thereby demonstrating the possibility of using our proposed method to recycle masks intended for disposal. The electrochemical performance of the fabricated carbonized materials was assessed by fabricating silicon/graphite (20:80) anodes incorporating these materials as additives for use in LIBs. Using a coin-type half-cell system, cells with the aforementioned carbonized materials exhibited initial capacities of 553 mAh/g, 607 mAh/g, and 571 mAh/g, respectively, which are comparable to those of commercial Super P (591 mAh/g). Cell cycled at the rate of 0.33 C with C-600, C-750, and C-900 as additives demonstrated capacity retention of 53.2%, 47.4%, and 51.1%, respectively, compared with that of Super P (48.3%). In addition, when cycled at rates from 0.2 to 5 C, the cells with anodes containing the respective additives exhibited rate capabilities similar to those of Super P. These results might be attributable to the unique surface properties and morphologies of the carbonized materials derived from the new recycling procedure, such as the size and number of heteroatoms on the surface.

본 연구에서는 용매로 침액되었을 시 전반적으로 더 균일한 상전이법 기반 평막 제조 시 주로 사용되는 부직포 지지체의 영향을 분석하였다. 도프용액의 점도가 낮을 경우 용액이 부직포층으로 쉽게 침투하여 불균일한 막이 형성되는 것 을 확인하였으며, 이를 방지하기 위해 부직포층을 유기용매로 침액하는 기법을 도입하였다. 부직포층이 유기 분리막이 생성 되는 것을 확인하였으며, 수투과 및 용매투과율도 향상하는 것을 알 수 있었다. 부직포 침액의 영향은 낮은 점도에서 확연하 게 나타났으며, 고분자용액의 점도가 높은 경우 침액 여부에 관계없이 동일한 성능을 얻을 수 있었다.

Amine-functionalized graphene was synthesized via a one-step solvothermal method and used as a metal-free cathode for non-aqueous lithium–oxygen batteries. The material delivered an outstanding specific capacity of 19,789 mAh/g at a current density of 200 mA/g as well as better cycling stability than graphene without the amine functional group. This improvement was attributed to the electron-donating effect of the amine groups and appropriate mesopore volume, which can promote the penetration of oxygen, electrons, and lithium ions, as well as accommodate more discharge products, Li2O2 in Li–O2 batteries. Amine-functionalized graphene has an amine functional group on the carbon surface, which improves the electrical conductivity of carbon and provides electrochemical active sites for oxygen absorption reactions.

본 논문에서는 범용유한요소해석 프로그램인 ABAQUS를 사용하여 국내에서 사용되는 콘크리트벽돌을 조적채움벽으로 가진 철근콘크리트 골조를 대상으로 유한요소해석을 실시하였다. 해석대상은 순수골조, 채움벽의 두께가 0.5B인 골조, 두께가 1.0B인 골조의 3종류이다. 철근콘크리트 골조 및 채움벽의 재료특성은 재료시험 결과로부터 구하였으나 두께가 1.0B인 채움벽의 경우 벽돌의 쌓기방법의 차이에 의해 0.5B 두께의 실험체보다 4배 정도 증가된 인장강도를 사용하였다. 유한요소해석결과는 실험을 통해 구한 하중-변위관계 및 변위각에 따른 균열양상을 상당히 정확하게 예측하였다. 유한요소해석 결과의 분석을 통해 조적채움벽과 골조사이의 접촉응력 및 골조의 전단력과 휨모멘트를 산정하였다.

Temperature correction trans-membrane pressure (TC-TMP) is frequently used as a fouling index in membrane water treatment plants. TC-TMP equation is derived based on an assumption that the total membrane resistance (i.e. the sum of the intrinsic membrane resistance and fouling resistance) is not affected by temperature. This work verified the validity of this assumption using microfiltration (MF) and ultrafiltration (UF) membranes with and without fouling. The foulants used in the work were kaolin (inorganic) and humic acid (organic). The intrinsic resistances of MF and UF membranes remains at constant values regardless of temperature change. When the same amount of foulants were accumulated on the membrane, inorganic fouling resistance with kaolin was constant regardless of temperature change while organic fouling resistance with humic acid decreased at higher temperatures, which means that TC-TMP cannot be used as a fouling index when organic fouling occurs in a real field application. Since TC-TMP underestimates the amount of fouling at higher temperatures, more attention should be necessary in the operation of membrane water treatment plant in a hotter season like summer.

In this study, in order to improve the thermal and electrical properties of epoxy/graphene nanoplatelets (GNPs), surface modifications of GNPs are conducted using silane coupling agents. Three silane coupling agents, i.e. 2-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane (ETMOS), 3-glycidoxypropyltriethoxysilane (GPTS), and 3-glycidoxypropyltrimethoxysilane (GPTMS), were used. Among theses, GPTMS exhibits the best modification performance for fabricating GNP-incorporated epoxy composites. The effect of the silanization is evaluated using transmission electron microscopy (TEM), scanning electron microscopy, thermogravimetric analysis, and energy dispersive X-ray spectroscopy. The electrical and thermal conductivities are characterized. The epoxy/silanized GNPs exhibits higher thermal and electrical properties than the epoxy/raw GNPs due to the improved dispersion state of the GNPs in the epoxy matrix. The TEM microphotographs and Turbiscan data demonstrate that the silane molecules grafted onto the GNP surface improve the GNP dispersion in the epoxy.

Two entomopathogenic bacteria, Xenorhabdus nematophila (Xn) and Photorhabdus temperata temperata (Ptt), are symbionts of nematodes, Steinernema carpocapsae and Heterorhabditis megidis, respectively. When the nematodes enter host insect hemocoel, the bacteria are released from the nematode intestine to insect hemocoel and cause immunosuppression, which results in septicemia. Culture broth of both bacteria had insecticidal effects when injected into hemocoel of Plutella xylostella larvae, but did not when orally administered. However, either mixture of Xn or Ptt with Bacillus thuringiensis (Bt) significantly enhanced the Bt pathogenicity against P. xylostella. The culture broth was fractionated with hexane and diethylacetate extracts. Diethylacetate extract had potent factor (s) to increase Bt pathogenicity. A compound, benzylideneacetone, identified from the diethylacetate fraction had oral toxicity against P. xylostella. This compound also showed high acaricidal effect on the two spotted spider mite, Tetranychus urticae

Two entomopathogenic bacteria, Xenorhabdus nematophila (Xn) and Photorhabdus temperata temperata (Ptt), maintain monoxenic condition within host insect cadaver by synthesizing and releasing various antibiotics. These two bacteria were cultured in tryptic soy broth during different times, which were screened in their antibacterial activities. Both bacterial culture broth had high antibacterial activities against Escherichia coli at their stationary growth phase. The potent culture broth was used to screen target plant bacterial pathogens using both inhibition zone assay and liquid culture assay. Ralstonia sp. was most susceptible, while Xanthomonas sp. was highly resistant. Pseudomonas sp. and Bacillus sp. showed hemi-susceptible. The culture broth was further fractionated into hexane and diethylether extracts. Significant antibacterial effect was found in the diethylether extract

This study evaluated the biochemical methane potential (BMP) of primary sludge, secondary sludge, and food waste in batch anaerobic mono-digestion tests, and investigated the effects of mixture ratio of those organic wastes on methane yield and production rate in batch anaerobic co-digestion tests, that were designed based on a simplex mixture design method. The BMP of primary sludge, secondary sludge and food waste were determined as 234.2, 172.7, and 379.1 mL CH4/g COD, respectively. The relationships between the mixing ratio of those organic wastes with methane yield and methane production rate were successfully expressed in special cubic models. Both methane yield and methane production rate were estimated as higher when the mixture ratio of food waste was higher. At a mixing ratio of 0.5 and 0.5 for primary sludge and food waste, the methane yield of 297.9 mL CH4/g COD was expected; this was 19.4% higher than that obtained at a mixing ratio of 0.3333, 0.3333 and 0.3333 for primary sludge, secondary sludge, and food waste (249.5 mL CH4/g COD). These findings could be useful when designing field-scale anaerobic digersters for mono- and co-digestion of sewage sludges and food waste.

This study investigated microbial communities and their diversity in a full-scale mesophilic anaerobic digester treating sewage sludge. Influent sewage sludge and anaerobic digester samples collected from a wastewater treatment plant in Busan were analyzed using high-throughput sequencing. It was found that the microbial community structure and diversity in the anaerobic digester could be affected by inoculation effect with influent sewage sludge. Nevertheless, distinct microbial communities were identified as the dominant microbial communities in the anaerobic digester. Twelve genera were identified as abundant bacterial communities, which included several groups of syntrophic bacteria communities, such as Candidatus Cloacimonas, Cloacimonadaceae W5, Smithella, which are (potential) syntrophic-propionate-oxidizing bacteria and Mesotoga and Thermovigra, which are (potential) syntrophic-acetate-oxidizing bacteria. Lentimicrobium, the most abundant genus in the anaerobic digester, may contribute to the decomposition of carbohydrates and the production of volatile fatty acids during the anaerobic digestion of sewage sludge. Of the methanogens identified, Methanollinea, Candidatus Methanofastidiosum, Methanospirillum, and Methanoculleus were the dominant hydrogenotrophic methanogens, and Methanosaeta was the dominant aceticlastic methanogens. The findings may be used as a reference for developing microbial indicators to evaluate the process stability and process efficiency of the anaerobic digestion of sewage sludge.

In this study, the inhibition of ammonia on anaerobic digestion of butyric acid was evaluated and the potential alleviating effects of such ammonia inhibition by the addition of magnetite particles were investigated. Independent anaerobic batch tests fed with butyric acid as a sole organic source were conducted in twenty 60-mL glass bottles with 10 different treatment conditions, comprising ammonia: 0.5, 2.0, 4.0, 6.0, and 7.0 g total ammonia nitrogen (TAN)/L and magnetite particles: 0 mM and 20 mM. The increase in ammonia concentration did not cause significant inhibition on methane yield; however, a significant inhibition on lag time and specific methane production rate was observed. The IC50 in the control treatments (without magnetite addition) was estimated as 6.2654 g TAN/L. A similar inhibition trend was observed in magnetite-added treatments; however, the inhibition effect by ammonia was significantly alleviated in lag time and specific methane production rate when compared to those in the control treatments. The lag time was shortened by 1.6–46.3%, specific methane production rate was improved by 6.0–69.0%. In the magnetite-added treatments, IC50 was estimated as 8.5361 g TAN/L. This study successfully demonstrated the potential of magnetite particles as an enhancer in anaerobic digestion of butyric acid under conditions of ammonia stress.