• Membrane and Water Treatment
• /
• 제14권3호
• /
• pp.115-120
• /
• 2023

The design theory for nanoporous filtration membranes needs to be established. The present study shows that the performance and technical advancement of nanoporous filtration membranes are determined by the fundamental parameter I (in the unit Watt^1/2) which is formulated as a function of the shear strength of the liquid-pore wall interface, the radius of the filtration pore, the membrane thickness, and the bulk dynamic viscosity of the flowing liquid. This parameter determines the critical power loss on a single filtration pore for initiating the wall slippage, which is important for the flux of the membrane. It also relates the membrane permeability to the power cost by the filtration pore. It is shown that for biological cellular membranes its values are on the scale 1.0E-8Watt^1/2, for mono-layer graphene membranes its values are on the scale 1.0E-9Watt^1/2, and for nanoporous membranes made of silica, silicon nitride or silicon carbonized its values are on the scale 1.0E-5Watt^1/2. The scale of the value of this parameter directly measures the level of the performance of a nanoporous filtration membrane. The carbon nanotube membrane has the similar performance with biological cellular membranes, as it also has the value of I on the scale 1.0E-8Watt^1/2.

• 한국산업보건학회지
• /
• 제27권2호
• /
• pp.115-122
• /
• 2017

Objectives: This study was designed to evaluate the changes in the particle filtration efficiencies of five cloth masks (4 plate types, 1 cup type) with an increasing number of machine washings and the degree of cloth expansion. Methods: NaCl aerosols were generated using an atomizer and passed through cloth masks in a dynamic aerosol chamber. Particle concentrations were measured both before and after for the cloth masks using an optical particle counter (OPC) in the size range of $0.3{\sim}10{\mu}m$. Results: In the original condition, the filtration efficiencies of the five cloth masks were A: 20.1%, B:30.9%, C: 25.0%, D: 26.5%, and E: 40.9%. As the number of washings increased in the order of one, two, and four times, the filtration efficiencies of cloth mask C increased. The filtration efficiency of A, D, and E increased after the first washing. With the exception of B, the filtration efficiency of cloth masks increased after the second washing and those of all cloth masks increased after the fourth washing. This might be caused by the fibers untangling from the yarn and being freed at one end. In this status, the packing density of the textile will not change, but the distances between fibers will increase, which might bring about an increase in filtration efficiency. When the cloth masks were extended by 10% and 20% in one direction, the filtration efficiencies of cloth masks B, D, and E decreased at 10% extension, and those of all cloth masks decreased at 20% extension. When the cloth masks were expanded by 10% and 20% in two directions, the filtration efficiencies of all cloth masks decreased by at least 34.7% at 10% extension, and by at least 60.9% at 20% extension Conclusions: The filtration efficiency of cloth masks could decrease after one to two machine washings, but will increase after four washings in comparison with their original performances. The filtration efficiency of cloth masks will decrease when they are expanded, such as when stretching over the nose during wearing status.

• 한국막학회:학술대회논문집
• /
• 한국막학회 1999년도 The 7th Summer Workshop of the Membrane Society of Korea
• /
• pp.95-96
• /
• 1999

The ultrafiltration behavior of dilute colloidal solution containing Si particles has been investigated. The experiments in cross flow mode have been performed at different operating condition by using the membrane with 20 kDa cut-off. The flux decline was due to the development of membrane fouling which was a dynamic process of two distinctive stages. For the high trans-membrane pressure, the pore blocking resistance was dominant at the initial period of filtraion and was followed by the cake resistance. And for the low cross flow velocity, the membrane fouling was governed by the cake filtration model at the initial stage of filtration process. Flux jump was observed temporally during the membrane filtration of mixed feed solution.

• 멤브레인
• /
• 제13권3호
• /
• pp.131-142
• /
• 2003

원통형 회전 역삼투법은 높은 전단력과 유체의 불안정성을 결합시켜 막오염을 감소시키는 동적 여과방법이다. 이 논문은, 회전여과의 물리적 특성, 물질전달과 농도분극 현상, 이론적 및 실험적 해석, 사례연구 등 회전역삼투법에 대한 최근의 연구를 요약해서 보여준다.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제11권2호
• /
• pp.45-55
• /
• 2006

강변여과수 취수 방식의 도입이 고려되었던 경상북도 고령군 낙동강변의 충적대수층을 대상으로 2차원 지하수 유동모사를 수행하여, 취수정 및 주변 대수층에서의 지하수위와 하천수 유입량의 계절적 변화를 분석하였다. 개념모델의 하천 경계조건은 연평균 하천수위를 고정 수두로 설정하는 경우와 실제 관측된 시계열 자료를 이용하여 변동 수두로 설정하는 경우로 구분하여 모사를 수행하였다. 모사 결과 산정된 하천수 유입 비율은 고정하천수두 모사의 경우 연중 $74.3{\sim}87.0%$의 범위를 보이며 연평균 82.4%인 반면, 변동하천수두 모사의 경우 $52.7{\sim}98.1%$, 연평균 78.5%로 나타났다. 따라서 시기별로 변동하는 하천수위가 하천수 유입 비율에 큰 영향을 미치며, 하천수 유입 비율을 정확하게 산정하기 위해서는 변동하천수두 조건을 이용해야 하는 것으로 해석된다. 강변으로부터 취수정까지의 이격거리를 변화시키면서 모사를 반복 수행한 결과 취수정 이격거리가 커질수록 하천수 혼합 비율은 다소 감소하지만 그 영향이 수 % 정도로 매우 작게 나타났다. 강변여과 취수 시 지하수위 및 하천수 혼합비율에 영향을 미치는 인자인 대수층의 수리전도도 및 저유계수, 지하수 함양량, 취수량 등에 대한 민감도 분석을 수행하였다. 대수층의 평균 지하수위와 하천수 유입 비율은 취수량과 지하수 함양량 변화에 민감한 반면, 취수정의 지하수위는 수리전도도와 취수량에 민감한 것으로 나타났다.

• 한국산학기술학회논문지
• /
• 제16권3호
• /
• pp.2314-2320
• /
• 2015

MBR (Membrane Bio-Reactor) 공정은 막 오염을 해결하기 위해 막대한 에너지 소비를 하는 공정으로 알려져 있다. 이를 해결하기 위한 일환으로 전기응집 기술을 MBR에 적용하는 시도가 보고되고 있다. 본 연구에서는 전류밀도를 변화시켜가며 활성슬러지의 막 여과를 수행하여 전기응집이 막 오염 저감에 미치는 영향과 메커니즘을 파악하고자 하였다. 활성슬러지 혼합액을 전기응집한 후 회분식교반셀로 분리 막의 여과성능을 평가하였다. 전류밀도(A/m2)를 10에서 40으로 증가시켰을 때 총 오염 저항 (Rc+Rf) 값이 18%에서 79%까지 감소하여 전기응집으로 인해 분리 막의 여과성능이 향상됨을 확인할 수 있었다. 전기응집 전후로 유기물 농도와 활성슬러지 입도분포 변화는 거의 일어나지 않았다. 여과 성능의 향상은 수산화알루미늄, Al(OH)3이 생성되어 막 표면에 부착되면서 오염물질이 쌓이게 됨을 방지하는 역할, 즉 dynamic membrane 으로 작용하였기 때문인 것으로 판단되었다.

• Advances in nano research
• /
• 제9권1호
• /
• pp.59-67
• /
• 2020

Filter cake formation during rotary drilling operation is an unavoidable scenario, hence there is need for constant improvement in the approaches used in monitoring the cake thickness growth in order to prevent drill-string sticking. This study proposes an improved model that predicts the growth of mud cake thickness overtime with the consideration of the addition of nanoparticles in the formulated drilling fluid system. Ferric oxide, titanium dioxide and copper oxide nanoparticles were used in varying amounts (2 g, 4 g and 6 g), and filtration data were obtained from the HPHT filtration test. The filter cakes formed were further analyzed with scanning electron microscope to obtain the morphological characteristics. The data obtained was used to validate the new filtrate loss model. This model specifically presents the concept of time variation in filter cake formation as against the previous works of constant and definite time. Regression coefficient which is a statistical measure was used to validate the new model and the predicted results were compared with the API model. The new model showed R² values of 99.9%, and the predictions from the proposed filtration model can be said to be more closely related to the experimental data than that predicted from the API model from the SSE and RMSE results.

• 한국막학회:학술대회논문집
• /
• 한국막학회 1991년도 춘계 총회 및 학술발표회
• /
• pp.13-14
• /
• 1991

본 연구에서는 Tobler[1]가 십자흐름여과 (crossflow filtration)의 개선책으로 제안한 동역학적 여과기를 제작하여 그 특성을 실험적으로 고찰하였다. 이 여과기는 두 개의 동심원통 사이를 유체가 흐를 때 내부원통의 회전속도가 외부원통의 회전속도보다 매우 빠를 경우 발생하는 Taylor 와류를 응용한 것이다.

• Korean Chemical Engineering Research
• /
• 제53권4호
• /
• pp.489-495
• /
• 2015

대기오염물질처리를 위한 생물살수여과법에서 물질전달현상을 이해하기 위한 선행 실험결과를 기초로 각각의 운전조건에서 기체/액체(살수액), 기체/고체(미생물)와 액체/고체에서의 model을 이용하여 물질전달계수를 평가하였다. 생물살수여과법에서 기/액에서는 정상상태물질수지, 그리고 액/고와 기/고에서는 동적물질수지를 이용하여 물질전달 model을 확립하고 그 결과를 고찰하였다. 물질전달 model은 여과탑을 일정크기 구획하여, 각 구획에서 동적 물질수지식을 수치해석 전산코드를 이용해 계산하였다. 동적물질수지식을 이용하여 계산된 결과는 실험결과와 비교하여 생물살수여과법에서 기/액, 기/고, 액/고 각상간의 물질전달계수($K_La$)를 산정하였다. 본 연구에서는 대기오염제어를 위한 생물살수여과법에서 물질전달계수를 결정하기 위한 실험방법개발과 model을 이용하여 물질전달현상을 고찰하였다.

• Composites Research
• /
• 제29권5호
• /
• pp.269-275
• /
• 2016

Multiscale hybrid composites, which consist of polymeric resins, microscale fibers and nanoscale reinforcements, have drawn significant attention in the field of advanced, high-performance materials. Despite their advantages, multiscale hybrid composites show challenges associated with nanomaterial dispersion, viscosity, interfacial bonding and load transfer, and orientation control. In this paper, carbon nanotube(CNT)/carbon fiber(CF)/polycarbonate(PC) multiscale hybrid composite were fabricated by a solution process to overcome the difficulties associated with controlling the melt viscosity of thermoplastic resins. The dependence of CNT loading was studied by varying the method to add CNTs, i.e., impregnation of CF with CNT/PC/solvent solution and impregnation of CNT-coated CF with PC/solvent solution. In addition, hybrid composites were fabricated through surfactant-aided CNT dispersion followed by vacuum filtration. The morphologies of the surfaces of hybrid composites, as analyzed by scanning electron microscopy, revealed the quality of PC impregnation depends on the processing method. Dynamic mechanical analysis was performed to evaluate their mechanical performance. It was analyzed that if the position of the value of tan ${\delta}$ is closer to the ideal line, the adhesion between polymer and carbon fiber is stronger. The effect of mechanical interlocking has a great influence on the dynamic mechanical properties of the composites with CNT-coated CF, which indicates that coating CF with CNTs is a suitable method to fabricate CNT/CF/PC hybrid composites.