• 한국재료학회지
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• 제28권5호
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• pp.301-307
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• 2018

A boron-doped diamond(BDD) electrode is attractive for many electrochemical applications due to its distinctive properties: an extremely wide potential window in aqueous and non-aqueous electrolytes, a very low and stable background current and a high resistance to surface fouling. An Ar gas mixture of $H_2$, $CH_4$ and trimethylboron (TMB, 0.1 % $C_3H_9B$ in $H_2$) is used in a hot filament chemical vapor deposition(HFCVD) reactor. The effect of argon addition on quality, structure and electrochemical property is investigated by scanning electron microscope(SEM), X-ray diffraction(XRD) and cyclic voltammetry(CV). In this study, BDD electrodes are manufactured using different $Ar/CH_4$ ratios ($Ar/CH_4$ = 0, 1, 2 and 4). The results of this study show that the diamond grain size decreases with increasing $Ar/CH_4$ ratios. On the other hand, the samples with an $Ar/CH_4$ ratio above 5 fail to produce a BDD electrode. In addition, the BDD electrodes manufactured by introducing different $Ar/CH_4$ ratios result in the most inclined to (111) preferential growth when the $Ar/CH_4$ ratio is 2. It is also noted that the electrochemical properties of the BDD electrode improve with the process of adding argon.

• 상하수도학회지
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• 제31권4호
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• pp.311-319
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• 2017

Scale formation is inevitable problem when seawater is treated by vacuum membrane distillation. The reason is the high concentration of calcium ion($Ca^{2+}$), sulfate ion(${SO_4}^{2-}$) and bicarbonate ion(${HCO_3}^-$). These ions form calcium sulfate($CaSO_4$) and calcium carbonate($CaCO_3$) on the membrane. The scale formed on membrane has to be removed, because the flux can be severely reduced and membrane wetting can be incurred. This study was carried out to investigate scale formation and effectiveness of acid cleaning in vacuum membrane distillation for SWRO brine treatment. It was found that permeate flux gradually declined until volume concentration factor(VCF) reached around 1.55 and membrane wetting started over VCF over 1.6 in the formation of precipitates containing $CaSO_4$ during VMD operation. In contrast, when calcium carbonate formed on membrane, permeate flux was gradually reduced until VCF 3.0. The precipitates containing both $CaSO_4$ and $CaCO_3$ were formed on the membrane surface and in the membrane pore.

• 멤브레인
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• 제9권4호
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• pp.202-208
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• 1999

오일과 세척제가 다량함유되어 있는 자동차 세척배수를 한외여과막으로 처리하였다 세차배수 처리에 적절한 분리막과 투과현상을 평가하기 위하여 분획분자량이 10, 30 및 100k dalton인 한회여과막과 dead-end 방식의 stirred cell (Amicon 8050)을 사용하여 투과유고과 제거율을 측정하였다 분획분자량이 작은 막에 경우 막오염현상이 미약하였으나 분획분자량이 큰 YM100 (100k dalton)인 경우에는 분리막 표면에 오일층을 형성 뿐만 아니라 막 세공 중 일부는 운전압력 조건에 따라서 변형이 가능한 오일 입자가 막을 가능성이 있다 그러나 오일 및 입자 배제율 95% 이상이며 세척제를 포함한 투과수를 재활용할 수 있어 수질오염을 최소화할 수 있을 것으로 판단된다. 또한 분획분자량이 50k dalton인 중공사형 한외여과막을 이용한 세차배수의 연속적 처리실험을 하였으며 케이크 여과모델이 잘 적용굄을 확인할수하였다.

• Membrane and Water Treatment
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• 제11권5호
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• pp.323-331
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• 2020

With the increasing demand on reverse osmosis (RO) membranes for water purification worldwide, the number of disposed membrane elements is expected to increase accordingly. Thus, recycling and reuse of end-of-life RO membranes should be a global environmental action. In this work, we aim to reuse the spent RO membrane for nanofiltration (NF) and ultrafiltration (UF) process by subjecting the spent membrane to solvent and oxidizing solution treatment, respectively. Our results showed that solvent-treated RO membrane could perform as good as commercial NF membrane by achieving similar separation efficiencies, but with reduced water permeability due to membrane surface fouling. By degrading the polyamide layer of RO membrane, the transformed membrane could achieve high water permeability (85.6 L/㎡.h.bar) and excellent rejection against macromolecules (at least 87.4%), suggesting its reuse potential as UF membrane. More importantly, our findings showed that in-situ transformation on the spent RO membrane using solvent and oxidizing solution could be safely conducted as the properties of the entire spiral wound element did not show significant changes upon prolonged exposure of these two solutions. Our findings are important to open up new possibilities for the discarded RO membranes for reuse in NF and UF process, prolonging the lifespan of spent membranes and promoting the sustainability of the membrane process.

• Membrane and Water Treatment
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• 제2권4호
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• pp.251-266
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• 2011

This work deals with the use of High Resolution Scanning Electron Microscopy (HRSEM) to verify ultrafiltration membrane selectivity at the end of the production line as well as membrane ageing. The first part of this work is focused on new membranes. It is shown that it is better to use sputtering metallization than vacuum deposition, as this latter technique entails thermal damage to the skin layer. Moreover, the impact of the metallization layer on the determination of the membrane pore size is studied and it is observed that no impact of the metallization step can be clearly defined for a metallization layer ranging from 3 to 12 nm. For example, an average pore size of 16.9 nm and a recovery rate of 6.5 % are observed for a 150 kDa cellulose acetate membrane. These results are in agreement with those given by the manufacturer: pore size ranging from 10 to 15 nm and recovery rate ranging from 5 to 10 %. The second part of this work focuses on the study of membrane ageing. A PVDF hollow fibre membrane is studied. It is shown that a 65 % decrease in the permeate flux can be linked to a decrease in the number of pores at the surface of the membrane and a decrease in the recovery rate. In conclusion, a mapping of the pores is performed for several new hollow fibre membranes used to produce drinking water, made of different materials, with different geometries and molecular weight cut-off. These results provide reference data that will help better understand the phenomena of membrane fouling and membrane ageing.

• 상하수도학회지
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• 제24권1호
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• pp.93-101
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• 2010

Reverse osmosis (RO) membranes have been widely used for desalination as well as water and wastewater treatment facilities. Cleaning process is important to maintain stable operation as well as prevention of membrane fouling. Purpose of this research is to analyze electrostatistic and chemical characteristics after cleaning of RO membrane against $SiO_2$ scale. Four RO membranes of polyamide are used and examined about effect of chemical cleaning. EDTA (ethylene diamine tetraacetic acid) and SDS (sodium dodecil sulfate) and NaOH are applied for cleaning process after operation in synthetic water. Then, cleaning was performed with chemicals such concentration as 6hr, 12hr and 24hr, respectively. As a result, transmittances of FT-IR of four membranes are compared at each cleaning concentration. Ta/Tv shows difference of chemical composition between new membrane and cleaning membrane after cleaning. Type B of RO membrane is turned out to be most vulnerable to cleaning among four membranes. In terms of zeta potential, new membrane has -16 mV to +6 mV on pH while scaled membrane has -18 mV to 2 mV. However, it changed -23mV to 0.9 mV after cleaning. In comparison with existing salt rejection of RO membranes after cleaning, the rejection of the membranes goes down 0.7% maximum. Though cleaning changes the characteristics of membrane surface, it does not greatly affect salt rejection. pH is a critical factor to flux change in PA (polyamide) membrane.

• 한국해양바이오학회지
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• 제9권1호
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• pp.14-21
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• 2017

The purpose of this study was to inhibit biofouling on a selectively permeable membrane (SPM) and increase biomass productivity in marine photobioreactors (PBRs) for microalgal cultivation by chemical treatment. Surfaces of a SPM, composed of polyethylene terephthalate (PET), was sulfonated to decrease hydrophobicity through attaching negatively charged sulfonic groups. Reaction time of sulfonation was varied from 0 min to 60 min. As the reaction time increased, the water contact angle value of SPM surface was decreased from $75.5^{\circ}$ to $44.5^{\circ}$, indicating decrease of surface hydrophobicity. Furthermore, the water permeability of sulfonated SPM was increased from $5.42mL/m^2/s$ to $10.58mL/m^2/s$, which reflects higher nutrients transfer rates through the membranes, due to decreased hydrophobicity. When cultivating Tetraselmis sp. using 100-mL floating PBRs with sulfonated SPMs, biomass productivity was improved by 34% compared with the control group (non-reacted SPMs). In addition, scanning electron microscopic observation of SPMs used for cultivation clearly revealed lower degree of cell attachment on the sulfonated SPMs. These results suggest that sulfornation of a PET SPM could improve microalgal biomass productivity by increasing nutrients transfer rates and inhibiting biofouling by algal cells.

• 공업화학
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• 제25권4호
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• pp.401-408
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• 2014

분리막 생물반응기에서 산기량 제어는 반응기 내 유체흐름과 특히 막표면 근방에서의 전단응력을 변화시켜 막오염 감소 및 에너지 절약을 구현하는 중요 독립변수 중 하나이다. 본 연구에서는 원통형 생물 반응기 중심에 침지형 평막을 장착하고 하부에서 공기가 공급되는 3차원적 시스템에 대하여 "COMSOL"프로그램을 사용하여 수치해석하였다. 용액의 점도, 온도는 일정하다고 가정했으며 투과액 부피와 산기량의 비인 $SAD_p$를 변수로 사용하였다. 유속센서, 동영상 이미지분석으로 측정한 유속과 수치해석 결과는 11% 이내에서 일치함을 확인하였다. 반응기 내 유체의 흐름은 산기관과 막모듈 구간에서 급격하게 증가하였으나 막모듈을 지나면서 감소하였으며 반응조 벽에서 중심축 방향으로 갈수록 유속이 증가하는 경향을 보였다. 막 표면에서 계산된 전단응력은 하단 중앙부가 가장 크게 나타났으며 산기량이 증가할수록 전단응력이 증가하였다. 특히 산기량을 0.15에서 0.25 L/min로 증가할 경우 크게 증가함을 확인할 수 있었다.

• 현장농수산연구지
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• 제4권1호
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• pp.119-127
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• 2002

지하수의 열(15℃)을 농업시설의 난방과 냉방에 사용하기 위하여, 관에 종방향으로 부착되는 plat fin tube 형 알루미늄(Al 6063) 열교환기를 개발하여 알루히트(의장등록 : 0247164)로 명명하였다. 열교환 핀을 관에 종방향으로 배치하여 송풍과 대류에 유체 흐름저항을 최소화 하였으며, 핀표면에 돌기를 만들어 결로와 fouling factor를 감소시켰다. 1. 알루히트의 제원은 관 내경 0.03m, 외경 0.036m, 두께 0.003m이며, 냉각핀의 두께 0.0012m, 핀 길이 0.032m로 하였다. 2. 단위 길이당 관 외부의 전열면적은 1.3946m²이며, 관내부 전열면적은 0.0942m²였고, 내외면적비 R_a = 14.805였다. 3. 핀의 길이 0.032m로 하였을 때, 핀의 효율이 93%정도인 것으로 나타났으며, 핀두께 0.0012m는 h^𝛿/k<0.2를 만족하여 적합한 것으로 판단된다. 4. 알루히트의 온수 방열 성능실험에서 열매체의 온도가 높고 유량이 많을수록 방열 열량이 많은 것으로 나타났고, 열매체의 온도 60℃, 유량 10 𝑙/min일 때 방열열량은 504kJ/h·m 였으며, 80℃, 40 𝑙/min일 때는 방열열량이 6,048kJ/h·m로 나타났다. 5. 방열성능에서 각각의 열매체 온도간 상관계수 $R^2_1=0.9898$, 유량간 상관계수 $R^2_2=0.9721$로 실험 데이터를 신뢰할 수 있었다.

• 멤브레인
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• 제16권3호
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• pp.182-187
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• 2006

본 연구에서는 침지형 MBR 공정에서 인제거를 위해 주입되는 응집제가 분리막의 여과성능에 미치는 영향을 알아보고자 하였고, 침지형 MBR에서 분리막 표면의 오염을 방지하기 위해 연속적으로 행하는 폭기가 응집 플록에 미치는 영향을 조사하고자 하였다. 이를 위해 MBR공정의 폭기조 슬러지를 채취하여 jar-test를 실시한 결과와 비교하였다. 실험 결과는 플록 크기와 슬러지 탈수성의 지표로서 비여과저항(SRF, Specific Resistance of Filtration)을 측정하여 비교하였다. 응집제 주입량이 증가할수록 $10{\mu}m$ 이하의 플록의 비율이 저감되었으며 탈수성이 증가하였다. 그러나 jar-test 결과와 비교하였을 때, 폭기의 전단력에 의해 그 효과가 저감된 것을 알 수 있었다. 응집제를 주입한 경우 주입하지 않은 경우보다 운전지속시간이 연장되었다 운전지속시간이 응집제 주입량에 비례하여 증가하지는 않았는데, 이는 연속적인 폭기의 전단력으로 인해 $10{\mu}m$ 이하의 입자가 충분히 저감되지 않았기 때문인 것으로 생각된다. 또한 응집제 주입량이 과도하면 오히려 여과저항을 증가시키는 결과를 초래하는 것을 알 수 있었다.