• Geomechanics and Engineering
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• 제19권1호
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• pp.37-47
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• 2019

The main objective of this study is to evaluate and compare the efficiency of ordinary Portland cement (OPC) in enhancing the unconfined compressive strength of soft soil alone and soft soil mixed with recycled tiles. The recycled tiles have been used to treat soft soil in a previous research by Al-Bared et al. (2019) and the results showed significant improvement, but the improved strength value was for samples treated with low cement content (2%). Hence, OPC is added alone in this research in various proportions and together with the optimum value of recycled tiles in order to investigate the improvement in the strength. The results of the compaction tests of the soft soil treated with recycled tiles and 2, 4, and 6% OPC revealed an increment in the maximum dry density and a decrement in the optimum moisture content. The optimum value of OPC was found to be 6%, at which the strength was the highest for both samples treated with OPC alone and samples treated with OPC and 20% recycled tiles. Under similar curing time, the strength of samples treated with recycled tiles and OPC was higher than the treated soil with the same percentage of OPC alone. The stress-strain curves showed ductile plastic behaviour for the untreated soft clay and brittle behaviour for almost all treated samples with OPC alone and OPC with recycled tiles. The microstructural tests indicated the formation of new cementitious products that were responsible for the improvement of the strength, such as calcium aluminium silicate hydrate. This research promotes recycled tiles as a green stabiliser for soil stabilisation capable of reducing the amount of OPC required for ground improvement. The replacement of OPC with recycled tiles resulted in higher strength compared to the control mix and this achievement may results in reducing both OPC in soil stabilisation and the disposal of recycled tiles into landfills.

• 한국화재소방학회논문지
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• 제33권1호
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• pp.156-163
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• 2019

이 연구에서는 국외 폐 소화기 재활용 제도를 분석하고 국내 재활용 운영실태의 문제점을 도출하여 폐 소화기 재활용 제도를 촉진할 수 있는 방안을 중심으로 제안하였다. 폐 소화기 재활용 촉진 방안은 첫째, 폐 소화기의 재활용 처리에 대한 제도 마련이다. 둘째, 폐 소화기 재활용처리 시스템 구축, 소화기의 회수 및 수집 운반 재활용 홍보 교육 등 전문성을 고려한 매뉴얼 개발이다. 셋째, 폐 소화기 수거에 대한 체계적이고 안전한 처리를 위한 다각적인 홍보 및 기술지원을 위한 교육 상담체계 확립이 필요하다. 넷째, 정부와 소화기 관련기관 차원에서 폐 소화기 재활용 촉진을 통해 환경의 오염을 막고 재활용이 가능한 부품들이 재생산되어 자원의 낭비를 줄이고 소방안전산업의 육성을 통해 소화기 품질 강국이라는 목적을 달성할 수 있도록 기술 및 정책적 지원이 필요하다.

• 한국물환경학회지
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• 제37권5호
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• pp.398-404
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• 2021

The use of water purifiers has been increasing every year due to increased drinking water safety concerns raised by the water pollution accidents occasionally reported. Currently, more than 10 million water purifiers have been distributed in Korea, and the estimation of the purifier sales reaches two million units per year. As a result, the number of used water purifier filters that must be replaced on a regular basis has gradually increased. However, regardless of the considerations for the capacity of used filters remaining, water purifier filters were replaced and collected at regular intervals. The high cost of disposal of the used filters by landfill or incineration were required. Thus, in this study, the current status and trends of recycling technologies for used water purifier filters were reviewed. It is noted that there was insufficient statistical data to understand the current status of the difference between the number of used water filters discarded and the number of those recycled. Most studies on the recycling of old water purifier filters have concentrated on pretreatment and cleaning methods for sediment filters and membrane filters, with the goal of extending the lifespan of used filters. Further, the study suggested future study directions on the recycling of used water purifier filters, which could be useful information on establishing environmental policy to promote the recycling of used filters.

• 한국환경농학회지
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• 제39권4호
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• pp.281-288
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• 2020

BACKGROUND: Generally, ammonia occurs from agricultural waste disposal. Ammonia is known as a harmful substance to the human body and has a bad influence such as eutrophication on the ecosystem. It is possible to remove the ammonia by ammonia adsorption method using natural zeolite, without external influence. However, due to the natural zeolite shape, it is hard to reuse. METHODS AND RESULTS: Electrospinning method can produce fiber with constant diameter. Moreover, electrospinning method has no limitation for selecting the material to make the fiber, and thus, it is valuable to reform the surface of adsorbent. In this study, reusable membrane was made by electrospinning method. The highest removal efficiency was shown from the membrane with 20% of zeolite included, and it has been verified that it is possible to reuse the membrane through chemical treatment. The highest ammonia removal efficiency was about 92.4%. CONCLUSION: In this study, ammonia adsorption characteristics of zeolite fibers were studied. Electrospinning method can produce zeolite fiber with even distribution. Ammonia can be removed efficiently from ion exchange ability of the natural zeolite. The result of adsorption isotherm indicated that both Freundlich model and Langmuir model provided the best fit for equilibrium data. And study on desorption has demonstrated that the ion exchange from zeolite was reversible when 0.01 M NaCl and KCl solution were used.

• Advances in environmental research
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• 제10권1호
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• pp.59-86
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• 2021

Landfilling is the most commonly adopted method for a large quantity of waste disposal. But, the main concern related to landfills is the generation of leachate. The leachate is high strength wastewater that is usually characterized by the presence of high molecular recalcitrant organics. Several conventional methods are adopted for leachate treatment. However, these methods are only suitable for young leachate, having high biodegradability and low toxicity levels. The mature and stabilized leachate needs advanced technologies for its effective treatment. Advanced oxidation processes (AOPs) are very suitable for such complex wastewater treatment as reported in the literature. After going through the literature survey, it can be concluded that Fenton-based approaches are effective for the treatment of various high/low strength wastewaters treatment. The applications of the Fenton-based approaches are widely adopted and well recognized due to their simplicity, cost-effectiveness, and reliability for the reduction of high chemical oxygen demand (COD) as reported in several studies. Besides, the process is relatively economical due to fewer chemical, non-sophisticated instruments, and low energy requirements. In this review, the conventional and advanced Fenton's approaches are explained with their detailed reaction mechanisms and applications for landfill leachate treatment. The effect of influencing factors like pH, the dosage of chemicals, nature of reaction matrix, and reagent ratio on the treatment efficiencies are also emphasized. Furthermore, the discussion regarding the reduction of chemical oxygen demand (COD) and color, increase in biodegradability, removal of humic acids from leachate, combined processes, and the pre/post-treatment options are highlighted. The scope of future studies is summarized to attain sustainable solutions for restrictions associated with these methods for effective leachate treatment.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.234-243
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• 2022

This study aims to characterize the irradiated RBMK-1500 nuclear graphite in terms of both structural and radiological properties. The experimental results of morphological and structural analysis of the irradiated graphite samples by using SEM, Raman spectroscopy as well as the theoretical evaluation of primary displacement damage are presented. Moreover, the experimental and theoretical evaluation of the neutron flux is provided and the presence of several γ emitters in the analyzed graphite samples is assessed. Furthermore, the improved version of rapid analysis method for ¹⁴C activity determination is applied and the experimentally obtained results are compared with calculated ones. Results indicate that structural changes are uniform enough in all the analyzed samples. However, the distribution of radionuclides is non-homogeneous in the irradiated RBMK-1500 reactor graphite matrix. The comprehensive understanding of both structural and radiological characteristics of nuclear graphite is very important when dealing with decision about irradiated graphite waste management strategy or treatment options prior to its final disposal.

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3631-3640
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• 2022

Uranium mill tailing ponds (UMTPs) are risk source of debris flow and a critical source of environmental U and Rn pollution. The technology of microbial induced calcium carbonate precipitation (MICP) has been extensively studied on reinforcement of UMTs, while little attention has been paid to the effects of MICP on U & Rn release, especially when incorporation of metakaolin and bacillus subtilis (MBS). In this study, the reinforcement and U & Rn immobilization role of MBS -MICP solidification in different grouting cycle for uranium mill tailings (UMTs) was comprehensively investigated. The results showed that under the action of about 166.7 g/L metakaolin and ~50% bacillus subtilis, the solidification cycle of MICP was shortened by 50%, the solidified bodies became brittle, and the axial stress increased by up to 7.9%, and U immobilization rates and Rn exhalation rates decrease by 12.6% and 0.8%, respectively. Therefore, the incorporation of MBS can enhance the triaxial compressive strength and improve the immobilization capacity of U and Rn of the UMTs bodies solidified during MICP, due to the reduction of pore volume and surface area, the formation of more crystals general gypsum and gismondine, as well as the enhancing of coprecipitation and encapsulation capacity.

• Geomechanics and Engineering
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• 제28권3호
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• pp.255-263
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• 2022

Lime stabilization has conventionally been listed amid the key techniques of chemical stabilization. Replacing lime with sustainable agro-based by-products have gained prominence in recent decades. Bagasse ash (BA) is one such potential alternatives, an industrial waste with abundance in production, and industries exploring sustainable solutions for its safe disposal. Supplementing BA with lime could be an ideal approach to reduce lime consumption. However, suitability of BA and lime for the stabilization of expansive clays, such as black cotton (BC) soil is yet to be explored. This paper therefore aims to investigate the suitability of BA-lime mixtures to stabilize BC soil with emphasis to compaction behaviors and unconfined compressive strength (UCS) using standard laboratory procedures. Suitability of BA-lime mixture is then assessed against addition of calcium sulphate which, from previous experience, is detrimental with lime stabilization. Experimental outcomes nominate 15% BA as the optimum value observed from both compaction and UCS data, while addition of 4% lime to 15% BA showed the best results. Mineralogical and microstructural analysis show the presence of cementitious compounds with addition of lime and calcium sulphate with curing periods. While, formation of Ettringite needles were noted with the addition of calcium sulphate in BA-lime mixtures (at optimum values) after 90-day curing, and UCS results showed a decrease at this point. To this end, addition of BA in lime stabilization showed encouraging results as assessed from the compaction and UCS results. Nonetheless usage of calcium salts, with utmost emphasis on calcium sulphate and equivalent should be avoided.

• 터널과지하공간
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• 제32권6호
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• pp.397-410
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• 2022

불연속면 분포, 수정 암질 지수 KURT, 적용성 평가방사성폐기물처분장은 장기간에 걸쳐 그 안전성이 보장되어야 하며, 따라서 정밀한 수준의 안정성 평가가 수행되어야 한다. 처분장 부지의 불연속면 특성 평가는 공학적방벽과 천연방벽을 포함한 처분장의 안전한 설계에 있어 매우 중요한 요소이다. 암반 불연속면은 역학적으로는 연약면으로 작용하며 수리적으로는 지하수 유동의 통로가 되기 때문에 그 분포와 특성에 대한 정밀한 조사가 요구된다. 다양한 불연속면 특성화 방안 중 암질지수(RQD)는 그 편이성으로 인해 널리 적용되어왔으나, 방향성이 있고, 측정 기준 길이의 영향을 받는 등 적용상의 한계가 있기 때문에, 이를 보완한 형태의 수정 암질지수들이 제안되어왔다. 본 논문은 KURT 주변 암반의 불연속면 정보를 활용하여 수정 암질지수들의 적용성을 평가하고, 동시에 해당 암반의 불연속면 특성을 평가하여 향후 연구에 활용할 수 있는 기반자료를 생성하기 위해 작성되었다.

• 한국산업융합학회 논문집
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• 제25권6_2호
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• pp.1119-1125
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• 2022

The depletion of resources and waste disposal caused by the continuous development of industry have emphasized the need to reduce consumption and production, recycle and reuse, and the importance of remanufacturing has increased in recent years. The spindle part of the aging planner miller, which is currently being remanufactured, is one of the factors that has the greatest impact on the performance of the machine tool. When designing the spindle part of the spindle shaft, there are considerations such as the configuration size bearing performance of the main shaft, but the diameter of the main shaft, the dangerous speed bearing, and the arrangement that affect the machining accuracy should be basically considered. As such, various studies have been conducted on the design of machine tool spindle spindles, but research on the reverse engineering of existing aging machine tool spindle spindles is poor. Reverse engineering is designing in the direction of improving performance by extracting specifications from already finished products, and first scanning the reverse engineered object through a 3D scanner, 3D modeling is performed based on the collected data, and then the process of deriving improvement plans by reverberating to improve performance by identifying wear and damage conditions is followed. Therefore, in this study, the purpose of this study is to provide data on reverse engineering by deriving improvement plans through optimal design for the bearing position of the aging planar Miller spindle spindle using central composite programming.