• Carbon letters
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• 제16권3호
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• pp.183-191
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• 2015

Gas transport through graphene-derived membranes has gained much interest recently due to its promising potential in filtration and separation applications. In this work, we explore Kr-85 gas radionuclide sequestration from natural air in nanoporous graphene oxide membranes in which different sizes and geometries of pores were modeled on the graphene oxide sheet. This was done using atomistic simulations considering mean-squared displacement, diffusion coefficient, number of crossed species of gases through nanoporous graphene oxide, and flow through interlayer galleries. The results showed that the gas features have the densest adsorbed zone in nanoporous graphene oxide, compared with a graphene membrane, and that graphene oxide was more favorable than graphene for Kr separation. The aim of this paper is to show that for the well-defined pore size called P-7, it is possible to separate Kr-85 from a gas mixture containing Kr-85, O₂ and N₂. The results would benefit the oil industry among others.

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

• Membrane and Water Treatment
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• 제8권6호
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• pp.553-562
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• 2017

In the present study, the water desalination across the penta-graphene has been explored by using molecular dynamics simulation. The penta-graphene, a new carbon allotrope, introduced theoretically in 2015. It was shown that this carbon nanostructure is slightly stiffer against buckling in comparison with the graphene nanoribbons. The effect of radius of curvature (ROC) of the membrane, pore size, and applied pressure, on water flow rate, and salt rejection is investigated. It is shown that salt rejection, and the shape of the oxygen density distribution inside the pore can be influenced by the ROC of membrane. Finally, it is shown that the ROC, and pore size of 2D membranes, play an important role in the salt rejection.

• Korean Membrane Journal
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• 제6권1호
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• pp.16-23
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• 2004

The silica containing carbon (C-SiO$_2$) membranes were fabricated using poly(imide siloxane) (PIS) having -CO- swivel group. The characteristics of porous C-SiO$_2$ structures prepared by the pyrolysis of poly(imide siloxane) were related with the micro-phase separation between the imide block and the siloxane block. Furthermore, the nitrogen adsorption isotherms of the CMS and the C-SiO$_2$ membranes were investigated to define the characteristics of porous structures. The C-SiO$_2$ membranes derived from PIS showed the type IV isotherm and possessed the hysteresis loop, which was associated with the mesoporous carbon structures, while the CMS membranes derived from PI showed the type I isotherm. For the molecular sieving probe, the C-SiO$_2$ membranes pyrolyzed at 550, 600, and 700$^{\circ}C$ showed the O$_2$ permeability of 924, 1076, and 367 Barrer (1 ${\times}$ 10$\^$-10/㎤(STP)cm/$\textrm{cm}^2$$.$s$.$cmHg) and O$_2$/N$_2$ selectivity of 9, 8, and 12.

• Korean Membrane Journal
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• 제5권1호
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• pp.43-53
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• 2003

The selectivity of a gas in the carbon molecular sieve membrane (CMSM) can be expressed as the ratio of the product of the diffusivity and the solubility of two different gases. The diffusivity is also expressed as the product of the entropy and the total energy (kinetic and potential energy) in the nano-sized pore of the membrane. The present study calculates the entropic-energy and selectivity of penetrant gases such as H$_2$, O$_2$, N$_2$, and CO$_2$ from the gas-in-a box theory to physically analyze the diffusivity of penetrant gas in slit-shaped pore of CMSM focusing on the restriction of gas motion based on the size difference between penetrant gas pairs. The contribution of each energy term is converted to entropic term separately. By the conjugated calculation for each entropic-energy, the entropic effects on diffusivity-selectivity for gas pairs such as H$_2$/N$_2$, CO$_2$/N$_2$, and O$_2$/N$_2$ were analyzed within active pore of CMSM. In the activated diffusion domain, the calculated value of entropic-selectivity lies between 9.25 and 111.6 for H$_2$/N$_2$, between 3.36 and 6.0 for CO$_2$/N$_2$, and between 1.25 and 16.94 for O$_2$/N$_2$, respectively. The size decrement of active pore in CMSM had the direct effect on the reduction of translational entropic-energy and the contribution of vibrational entropic-energy for N$_2$, O$_2$, and H$_2$ was almost negligible. However, the vibrational entropic term of CO$_2$ might extravagantly affect on the entropic-selectivity.

• 멤브레인
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• 제33권4호
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• pp.149-157
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• 2023

공유 유기 프레임워크(COF)는 분자 분리, 염료 분리, 가스 분리, 여과 및 담수화를 포함한 다양한 응용 분야에서 가능성을 보여주었습니다. COF를 막에 통합하면 투과성, 선택성 및 안정성이 향상되어 분리 공정이 향상됩니다. 단일 벽 탄소 나노튜브(SWCNT)와 COF를 결합하면 염료 분리에 이상적인 높은 투과성과 안정성을 가진 나노 복합막을 생성합니다. COF를 폴리아미드(PA) 막에 통합하면 합성 계면 전략을 통해 투과성과 선택성이 향상됩니다. 혼합 매트릭스 막(MMM)의 3차원 COF 필러는 CO₂/CH₄ 분리를 향상시켜 바이오가스 업그레이드에 적합합니다. COF와 금속 유기 프레임워크(MOF) 막을 결합한 모든 나노 다공성 복합재(ANC) 막은 투과성-선택성 트레이드오프를 극복하여 가스 투과성을 크게 향상시킵니다. 가상 COF (hypoCOF)를 사용한 계산 시뮬레이션은 CO₂ 분리 및 H₂ 정제와 관련하여 우수한 CO₂ 선택성과 작업 능력을 입증합니다. 박막 복합재(TFC) 및 폴리술폰아미드(PSA) 막에 통합된 COF는 유기 오염물, 염 오염물 및 중금속 이온에 대한 거부 성능을 향상시켜 분리 능력을 향상시킵니다. TpPa-SO₃H/PAN 공유 유기 프레임워크 막(COFM)은 대전된 그룹을 활용하여 정전기적 반발을 통해 효율적인 담수화를 가능하게 함으로써 기존의 폴리아미드 막에 비해 우수한 담수화 성능을 보여 이온 및 분자 분리의 잠재력을 제시했습니다. 이러한 연구 결과는 투과성, 선택성 및 안정성을 향상시켜 향상된 분리 공정을 위한 막 기술에서 COF의 잠재력을 강조합니다. 이 검토에서는 분리 공정에 적용된 COF에 대해 논의합니다.