• 한국막학회:학술대회논문집
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• 한국막학회 2002년도 제10회 하계 Workshop
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• pp.59-101
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• 2002

PVDF is good material for a hollow fiber membrane with high porosity and excellent hydrophobicity. Asymmetric PVDF hollow fiber membranes were prepared by the Loeb-Sourirajan phase inversion method. Asymmetric PVDF hollow fiber membranes could be controlled in pore size and porosity using various additives(LiCl, ZnCl$_2$) and internal coagulants (water, EtOH/water, and DMAc/water mixture). $CO_2$removal efficiency of asymmetric PVDF hollow fiber membranes was 1.2 times high than that of commercialized PP hollow fiber membranes at MEA 5wt% solution. $CO_2$flux of asymmetric PVDF hollow fiber membranes was 2.5 times higher than that of commercialized PP hollow fiber membranes. $CO_2$removal efficiency and absorption rate of asymmetric PVDF hollow fiber membranes were 30 times higher than those of packed column at absorbent $H_2O$. $CO_2$flux of asymmetric PVDF hollow fiber membranes at MEA 5wt% solution was 48 times higher than that of pure water. In the case of MEA 5wt% solution used as an absorbent, the $CO_2$absorption rate and removal efficiency of PVDF hollow fiber membrane were 2.3 times higher than that of a packed column.

• Membrane and Water Treatment
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• 제5권2호
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• pp.109-122
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• 2014

Polyvinylidene fluoride (PVDF) hollow fiber membrane is widely used for water treatment. However, the weak mechanical strength of PVDF limits its application. To enhance its tensile strength, a double-layer composite hollow fiber membrane, with PVDF and polyetherimide as the external and inner layers, respectively, was successfully prepared through phase inversion technique. The effects of additive content, air gap distance, N,N-dimethyl-acetamide content in the inner core liquid, and the temperature of external coagulation bath on the membrane structure, permeation flux, rejection, tensile strength, and porosity were determined. Experimental results showed that the optimum preparation conditions for the double-layer composite hollow fiber membrane were as follows: PEG-400 and PEG-600, 5 wt%; air gap distance, 10 cm; inner core liquid and the external coagulation bath should be water; and temperature of the external coagulation bath, 40 C. A single layer PVDF hollow fiber membrane (without PEI layer) was also prepared under optimum conditions. The double-layer composite membrane remarkably improved the tensile strength compared with the single-layer PVDF hollow fiber membrane. The permeation flux, rejection, and porosity were also slightly enhanced. High-tensile strength hollow fiber PVDF ultrafiltration membrane can be fabricated using the proposed technique.

• 멤브레인
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• 제24권2호
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• pp.158-166
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• 2014

본 연구에서는 PVDF 중공사막을 열유도상분리와 연신의 복합공정에 의해 제조하였으며, 연신비에 따른 분리막의 구조 및 물성을 분석하였다. 이 분리막 제조의 메카니즘은 액-액 상분리에 기초하며, 최종 중공사막은 bicontinuous한 구조와 연신에 의해 fibrill 구조를 가지게 되어, 구정(spherulite)구조를 갖는 고-액 상분리막과 bicontinuous한 구조만을 갖는 액-액상분리막과 차별화된다. 우선, TIPS공정을 통해, gamma-butyrolacton, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) 등을 단일 혹은 이들을 조합한 혼합 diluent로 사용하여, 냉각조건, PVDF와 희석제의 함량을 조절하면서 중공사막 전구체를 제조하고, 후속공정인 연신에 의해 최종적으로 중공사막의 외부표면을 porous하게, 혹은 dense하게 만들 수 있었다. 연신된 중공사막을 에탄올에 추출, 건조한 후 SEM을 통하여 pore 구조의 변화를 관찰하였으며, 수투과량, 다공도, 기공 크기, 표면 거칠기, 인장강도 등의 변화를 분석하였다.

• 한국막학회:학술대회논문집
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• 한국막학회 2003년도 The 4th Korea-Italy Workshop
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• pp.133-135
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• 2003

The removal of dissolved oxygen(DO) from water was studied using a poly(vinyliene fluoride)(PVDF) hollow fiber membrane contactor(HFMC) with the vacuum degassing process(VDP), Asymmetric porous PVDF hollow fiber membranes (HFM) for membrane contactor were prepared by a wet phase inversion method. In spinning of these PVDF hollow fibers, dimethy lacetamide (DMAc), LiCl and pure water were used as a solvent, a pore-forming additive and internal/external coagulant, respectively. The characteristics of the structure(pore size, porosity etc.) of the prepared PVDF HFMs as a function of concentration of pore-forming additive in polymer dope solution were studied. Also, the removal efficiency of DO from water according to flow rates of water, using PVDF HFMC with VDP, was studied. The performance of the asymmetric porous PVDF HFMC and a symmetric porous PP HFMC commercialized were compared. As a result, the asymmetric porous PVDF HFMC showed higher removal efficiency of DO than that of a symmetric porous PP HFMC.

• Membrane and Water Treatment
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• 제10권4호
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• pp.287-298
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• 2019

Lotus leaf has a special dual micro and nano surface structure which gives its highly hydrophobic surface characteristics and so-called self cleaning effect. In order to endow PVDF hollow fiber membrane with this special structure and improve the hydrophobicity of membrane surface, PVDF hollow fiber composite membranes was obtained through the immersion coating of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) dilute solution on the outside surface of PVDF support membrane. The prepared PVDF composite membranes were used in the vacuum membrane distillation (VMD) for the desalination. The effects of PVDF-HFP dilute solution concentration in the dope solution and coating time on VMD separation performance was studied. Membranes were characterized by SEM, WCA measurement, porosity, and liquid entry pressure of water. VMD test was carried out using $35g{\cdot}L^{-1}$ NaCl aqueous solution as the feed solution at feed temperature of $30^{\circ}C$ and the permeate pressure of 31.3 kPa. The vapour flux reached a maximum when PVDF-HFP concentration in the dilute solution was 5 wt% and the coating time was kept in the range of 10-60 s. This was attributed to the well configuration of micro-nano rods which was similar with the dual micro-nano structure on the lotus leaf. Compared with the original PVDF membrane, the salt rejection can be well maintained which was greater than 99.99 % meanwhile permeation water conductivity was kept at a low value of $7-9{\mu}S{\cdot}cm^{-1}$ during the continuous testing for 360 h.

• 멤브레인
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• 제25권3호
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• pp.216-222
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• 2015

막증류(membrane distillation, MD)용 분리막의 장기 내구성능에 영향을 미치는 인자인 소수성 분리막의 젖음 현상에 대한 평가 지표로 사용되는 액체투과압력(liquid entry pressure, LEP) 측정 방법을 최적화하였다. PE (polyethylene) 분리막 및 PVDF (polyvinylidene di-fluoride) 중공사 분리막의 LEP를 측정하기 위하여 20 wt%의 고농도 염수를 제조하여 원수로 사용하고 투과수의 전도도를 모니터링하였다. PE와 PVDF 중공사 분리막의 신뢰성 있는 LEP 측정을 위해서는 5 min 이상의 holing time을 두고 주입 압력을 증가시켜야 하며, 증류수 수조의 물량대비 분리막의 면적비 또한 $10m^2/m^3$ 이상으로 부여되어야 함을 확인하였다.

• 상하수도학회지
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• 제31권4호
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• pp.339-346
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• 2017

In this study, thermal performance test of VMD module was performed, prior to the construction of the demonstration plant using the vacuum membrane distillation (VMD) module of the capacity of $400m^3/day$ and to the commercialization of the VMD module. For the thermal performance test, the experimental equipment of capacity of $2m^3/day$ was constructed. The permeate flux test and thermal performance test according to feed water conditions such as temperature and flow rate were conducted. The VMD module used in the study was manufactured by ECONITY Co., LTD with PVDF hollow fiber membrane. As a result, the Performance Ratio (PR) of the VMD module showed the maximum value of 0.904 under the condition of feed water temperature of $75^{\circ}C$ and flow rate of $8m^3/h$. PR value of the VMD module using PVDF hollow fiber membrane showed linearly increasing relationship with feed water temperature and flow rate. Also, The permeate flux of the VMD module was analyzed to have maximum value of 18.25 LMH and the salt rejection was 99.99%.

• Korean Chemical Engineering Research
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• 제46권3호
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• pp.521-528
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• 2008

중공사막 접촉기에 적절한 PVDF 중공사막을 상전이 공정에 의하여 제조하였으며, SEM 과 기체투과도에 의하여 그 특성을 분석하였다. 벤치규모 중공사막 접촉기에서 $SO_2$ 제거를 위한 흡수제는 수산화나트륨 수용액을 사용하였다. 기체는 shell side, 액체는 lumen side로 흐르는 counter-current로 실험하였으며, 흡수제의 농도, 기체의 유속, 액가스비, 유입 $SO_2$ 농도에 따른 영향을 알아보았으며, 수학적 모델링에 의해 막 물질전달계수($k_m$)를 측정하였다. 흡수제의 농도와 액기비가 증가함에 따라 기-액 계면에서 충분한 알칼리도가 제공되므로, 액체막 저항이 감소하며, 총괄물질전달 용량계수는 증가하였다. 기체유속이 증가함에 따라 기체막저항은 감소하게 되므로 총괄물질전달 용량계수는 증가하였다.

• Membrane and Water Treatment
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• 제10권4호
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• pp.251-257
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• 2019

Fabricating hydrophobic porous membrane is important for exploring the applications of membrane distillation (MD). In the present paper, poly(vinylidene fluoride) (PVDF) hollow fiber membrane was modified by coating polydimethylsiloxane (PDMS) on its surface. The effects of PDMS concentration, cross-linking temperature and cross-linking time on the performance of the composite membranes in a vacuum membrane distillation (VMD) process were investigated. It was found that the hydrophobicity and the VMD performance of the PVDF hollow fiber membrane were obviously improved by coating PDMS. The optimal PDMS concentration, cross-linking temperature and cross-linking time were 0.5 wt%, $80^{\circ}C$, and 9 hr, respectively.

• Macromolecular Research
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• 제14권6호
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• pp.596-602
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• 2006

The effect of high-temperature spinning and poly(vinyl pyrrolidone) (PVP) additive on poly(vinylidene fluoride) (PVDF) hollow fiber membranes was investigated using differential scanning calorimetry, X-ray diffraction measurement, and scanning electron microscopy, together with the corresponding microfiltration performances such as water flux, rejection rate, and elongational strength. Using high-temperature spinning, porous hollow fiber membranes with particulate morphology were prepared through PVDF crystallization. The particulate structure of the membranes was further modified by the addition of miscible PVP with PVDF. Due to these effects, the rejection rate and strength of the fibers were increased at the expense of reduced water flux and mean pore size, which indicates that high-temperature spinning and PVP addition are vary effective to control the morphology of PVDF hollow fiber membranes for microfiltration.