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메틸렌 블루 흡착능 향상을 위한 할로이사이트 기반 튜브형 담체 연구
전준영(Junyeong Jeon),조예빈(Yebin Cho),김종욱(Jongwook Kim),신승구(Seung Gu Shin),전종록(Jong-Rok Jeon),이윤기(Younki Lee) 한국청정기술학회 2021 청정기술 Vol.27 No.4
할로이사이트(Al₂Si₂O5(OH)₄∙nH₂O)는 다층벽 나노 튜브 구조의 저단가 천연 점토 분말로, 상대적으로 우수한 비표면적으로 인해 수처리용 염료 흡착 소재로 연구되어왔다. 분말형 점토 소재는 수처리 시 응집으로 인한 관막음 현상을 억제하기 위해서 흡착 담체로의 사용이 검토되나, 강도 확보를 위한 높은 소성 온도 및 분말 대비 낮은 소재 활용률로 인해 흡착능 구현에 난점이 있다. 본 연구에서는 750 ℃에서 대기 소성에 따른 할로이사이트의 메틸렌블루(MB) 흡착능 유지율을 평가하였으며, 소재활용율 향상을 위한 관형의 할로이사이트 담체를 제조하였다. 할로이사이트의 높은 열적 구조 안정성은 투과전자현미경 이미지를 통해 평가되었으며, 할로이사이트는 각각 22% (7.65 mg g<SUP>-1</SUP>), 6% (11.7 mg g<SUP>-1</SUP>)의 유지율을 보인 규조토 및 마그네솔<SUP>®</SUP>XL대비 우수한 MB 흡착능 유지율 및 흡착능(93%, 18.5 mg g<SUP>-1</SUP>) 나타내었다. 또한, 성형 시 리그닌과의 복합화는 기존 소성체 대비흡착능이 향상되었으며, 수소 분위기 하 소성 시 초기 MB 흡착을 촉진했다. 관형의 할로이사이트 담체는 접촉면적의 증가를 통해 막대형 담체 대비 빠른 초기 흡착량의 증가 및 우수한 질량 당 흡착능(7.36 mg g<SUP>-1</SUP>)을 구현하였다. Halloysite nanotubes (HNTs), the multiwalled clay mineral with the composition of Al₂Si₂O5(OH)₄∙nH₂O, have been highlighted as a low-cost adsorbent for the removal of dyes from wastewater. Although a powder of halloysite presents a high specific surface area, forming media are significantly considered due to sludge-clogging induced by the water-bound agglomeration. However, higher firing temperature to achieve the structural durability of the media and lower utilization rate due to longer penetration depth into the media act as hurdles to increase the dye-adsorption capacity. In this work, the retention of the adsorption capacity of halloysite was evaluated with methylene blue solution after the heat treatment at 750 ℃. In order to improve the utilization rate, tubular media were fabricated by extrusion. The images taken by transmission electron microscopy show that HNTs present excellent structural stability under heat treatment. The HNTs also provide superb capacity retention for MB adsorption (93%, 18.5 mg g<SUP>-1</SUP>), while the diatomite and Magnesol<SUP>®</SUP> XL show 22% (7.65 mg g<SUP>-1</SUP>) and 6% (11.7 mg g<SUP>-1</SUP>), respectively. Additionally, compositing with lignin enhances adsorption capacity, and the heat treatment under the hydrogen atmosphere accelerates the adsorption in the early stage. Compared to the rod-type, the tubular halloysite media rapidly increases methylene blue adsorption capacity.
이익의 품질과 자본시장의 이례현상 : 수익-비용 대응의 원칙과 주가표류현상
최국현 ( Kuk-hyun Choe ),전종록 ( Jong-rok Jeon ) 한국생산성학회 2016 生産性論集 Vol.30 No.3
The matching principle in conventional accrual basis accounting, rather than cash basis accounting, recognizes accounting income by recording related expenses at the period when revenues are recognized. Accounting methods with high level of matching principle can be defined as neutrality in accounting in the sense that an impartial point of view is maintained in revenue and expense recognition. According to previous studies, it has been reported that the higher the level of matching principle is, the higher the quality of accounting income becomes. Thus, by analyzing the effects of the level of matching principle on the firm specific stock returns, post-earnings-announcement drift, this study examines earnings quality of matching principle is attributable to post-earnings-announcement drift. Previous studies find that earnings quality of earnings persistence is positively correlated with post-earnings-announcement drift. Thus, another estimate of earnings quality, the degree of matching revenues to expenses, is hypothesized to have the positive effect on post-earnings-announcement drift. Our results are generally consistent with the hypothesis. Findings show that firms with higher degree of revenue-expense matching have abnormal stock returns 10 days post-earnings announcement. Whereas over 10 days post-earnings announcement fail to show excessive stock returns. Some caveats can be attributable to these findings. The way we measure the degree of matching principle by the adjusted R² from revenue to expenses may not be adequate, and random walk model to estimate expected earnings may capture the properties with considerable errors. Nonetheless, over 2,000 observations in the period of 8 years can alleviate such errors in our results.