• 산업기술연구
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• 제28권B호
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• pp.47-52
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• 2008

In this study, GAC adsorption, ozonation and $O_3/GAC$ hybrid processes were investigated for treatment of humic acid. The degradation characteristics and efficiencies of humic acid in each process were evaluated through pH variation, $UV_{254}$ decrease, DOC removal, change of molecular size distribution and by-products formation. DOC removal rate in $O_3/GAC$ hybrid process (80%) was higher than arithmetic sum of ozonation (38%) and GAC adsorption process (19%) by synergism. $UV_{254}$ decrease rate of humic acid was also the highest than any other processes when treated in $O_3/GAC$ hybrid process. Molecular size distribution was not significantly changed in the GAC adsorption process. Main distribution of molecular size of humic acid was converted from 3 k~30 kDa into 0.5 k~3 kDa in ozonation. But the most of large molecular sizes of humic acid converted into small molecules(smaller than 0.5 kDa) in $O_3/GAC$ hybrid process. Quantities of formaldehyde and glyoxal formed in $O_3/GAC$ hybrid process were less than the ones in ozonation.

• Environmental Engineering Research
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• 제23권2호
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• pp.181-188
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• 2018

Photocatalytic oxidation in the presence of Fe-doped, Zn-doped or Fe-Zn co-doped $TiO_2$ was used to effectively decompose humic acids (HAs) in water. The highest HAs removal efficiency (65.7%) was achieved in the presence of $500^{\circ}C$ calcined 0.0010% Fe-Zn co-doped $TiO_2$ with the Fe:Zn ratio of 3:2. The initial solution pH value, inorganic cations and anions also affected the catalyst photocatalytic ability. The HAs removal for the initial pH of 2 was the highest, and for the pH of 6 was the lowest. The photocatalytic oxidation of HAs was enhanced with the increase of the $Ca^{2+}$ or $Mg^{2+}$ concentration, and reduced when concentrations of some anions increased. The inhibition order of the anions on $TiO_2$ photocatalytic activities was $CO{_3}^{2-}$ > $HCO_3{^-}$ > $Cl^-$, but a slightly promotion was achieved when $SO{_4}^{2-}$ was added. Total organic carbon (TOC) removal was used to evaluate the actual HAs mineralization degree caused by the $500^{\circ}C$ calcined 0.0010% Fe-Zn (3:2) co-doped $TiO_2$. For tap water added with HAs, the $UV_{254}$ and TOC removal rates were 57.2% and 49.9%, respectively. The $UV_{254}$ removal efficiency was higher than that of TOC because of the generation of intermediates that could significantly reduce the $UV_{254}$, but not the TOC.

• Tribology and Lubricants
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• 제38권6호
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• pp.247-254
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• 2022

Chemical mechanical polishing (CMP) is a hybrid surface-polishing process that utilizes both mechanical and chemical energy. However, the recently emerging semiconductor substrate and thin film materials are challenging to process using the existing CMP. Therefore, previous researchers have conducted studies to increase the material removal rate (MRR) of CMP. Most materials studied to improve MRR have high hardness and chemical stability. Methods for enhancing the material removal efficiency of CMP include additional provision of electric, thermal, light, mechanical, and chemical energies. This study aims to introduce research trends on CMP using ultraviolet (UV) light to these methods to improve the material removal efficiency of CMP. This method, photocatalysis-assisted chemical mechanical polishing (PCMP), utilizes photocatalytic oxidation using UV light. In this study, the target materials of the PCMP application include SiC, GaN, GaAs, and Ru. This study explains the photocatalytic reaction, which is the basic principle of PCMP, and reviews studies on PCMP according to materials. Additionally, the researchers classified the PCMP system used in existing studies and presented the course for further investigation of PCMP. This study aims to aid in understanding PCMP and set the direction of future research. Lastly, since there have not been many studies on the tribology characteristics in PCMP, research on this is expected to be required.

• 상하수도학회지
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• 제26권2호
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• pp.229-236
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• 2012

염기도를 달리하여 제조된 PACl에 대한 Al(III)종 분포는 염기도가 높을수록 monomeric Al(III)종은 적어지고, precipitate Al(III)종은 증가하는 것으로 나타났다. 염기도 13.6%의 경우에서는 monomeric Al(III)종이 81%, polymeric Al(III)종이 19%, precipitate Al(III)종은 0%로 monomeric Al(III)종이 주종을 이루고 있었다. 염기도 13.6%의 경우에서 재안정화 없이 80% 정도의 탁도제거 효율을 유지하고 있었으며, $UV_{254}$ 제거효율이 향상되는 것은 낮은 응집 pH 범위에서 유기물 응집효과가 우수하게 나타나기 때문으로 판단된다. 그리고 13.6% 염기도를 가진 PACl이 T-P 제거효율 및 $PO_{4}-P$의 제거효율이 가장 우수한 것으로 나타났으며 이는 높은 monomeric Al 성분에 기인하리라 판단된다.

• 상하수도학회지
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• 제11권4호
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• pp.118-125
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• 1997

Conventional sedimentation method has some limitations for turbidity removal in water treatment because drinking water sources are getting polluted. Removal rates of turbidity using DAF and sedimentation process were compared for various water conditions to know whether DAF is effective to improve sedimentation process. Water samples were clay(gravity 2.65) water 100mg/l, H raw water, mixed water of H raw water and clay 100mg/l, and mixed water of HA(Humic Acid) 5mg/l and clay 100mg/l. Other parameters were temperature, coagulants(Alum, $FeCl_3$), and treatment time. Water temperature greatly affected in removal rates of turbidity for sedimentation and DAF. Generally DAF was more effective in removal rates of turbidity than sedimentation at the same experimental condition. Removal rates of $UV_{254}$ were high to over 90%, and independent of temperature and coagulant.

• 산업기술연구
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• 제32권A호
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• pp.95-102
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• 2012

To advance luminance efficiency of Titania at visible range, N-doped $TiO_2$ was prepared by using ammonium hydroxide as a source of nitrogen. The photoactivities of the synthesized $TiO_2$ were evaluated on the basis of degradation of humic acid in aqueous solutions with different light sources, UV-C, UV-A and fluorescent lamp. As a result, at UV-C is high efficiency $UV_{254}$ decrease and TOC removal. In this study, the best synthetic conditions of N-doped $TiO_2$ were 5.0 M of ammonium hydroxide concentration and calcination temperature of $550^{\circ}C$. The degradation rate of humic acid as an evaluation of photoactivities of the catalysts were conducted with pH variation, decrease rate of molecular absorption, removal rate of total organic carbon and fluorescece evolution for humic acid solution. XRD and SEM were applied for analysis of surface analysis of the catalysts.

• 대한환경공학회지
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• 제27권9호
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• pp.989-994
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• 2005

본 연구에서는 활성탄 흡착, 오존 단독, 오존/활성탄 혼합공정을 이용하여 부식산을 처리하고 부식산의 처리효율을 $UV_{254}$와 DOC를 통해 살펴보았으며, 부식산의 분해특성은 분자량 크기분포의 변화와 활성탄 표면변화를 통해 관찰하였다. 각 공정에서의 DOC 제거효율을 살펴본 결과, 활성탄 흡착공정은 약 19%, 오존 단독공정은 38%이었으나, 오존/활성탄 혼합공정에서는 약 80%로 활성탄 흡착공정과 오존 단독공정의 DOC 처리효율을 합한 것보다 훨씬 높아, 혼합공정을 도입함으로써 시너지 효과를 얻을 수 있는 것으로 나타났다. 기리고 $UV_{254}$ 감소율 역시 오존/활성탄 혼합공정에서 가장 크게 나타났다. 오존/활성탄 혼합공정에서 활성탄은 고유의 흡착제 역할뿐만 아니라 흡착된 유기물과 오존의 접촉을 촉진시키는 반응자리를 제공하는 역할을 하는 것으로 사료된다. 각 공정에서의 분자량크기분포 변화를 살펴본 결과, 활성탄 흡착공정에의 분자량 크기분포는 반응 전후에 큰 차이가 없었으며, 오존 단독공정에서는 30 kDa 이상의 분자량이 반응시간 10분 이후에는 거의 감소하지 않고 일정하였으나, 0.5 kDa 이하의 저분자량은 초기 4.8%에서 120분 처리시 12.3%로 증가하였다. 한편 오존/활성탄 혼합공정에서는 120분 처리시 30 kDa 이상 분자량이 초기 36.3%에서 3.9%로 뚜렷하게 감소하였으며, 0.5 kDa 이하의 저분자량은 초기 4.8%에서 40.1%로 크게 증가하였다.

• 한국환경농학회지
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• 제21권3호
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• pp.189-196
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• 2002

낙동강 상수원수를 대상으로 연속적 오존처리에서 오존주입농도에 따른 유기물 분해 특성을 조사하기 위하여 오존처리에 의한 DOE성분변화, UV254/DOC의 변화와 소비오존에 따른 DOC 제거효율을 조사한 결과는 다음과 같다. 유입원수의 수질변화에 따라 다소 차이는 있었으나 전반적으로 오존주입농도가 증가할수록 DOC 처리효율도 증가되었다. 오존처리에 따른 DOC 성분변화는 전오존을 3 mg/L 농도로 처리시 TDOC, ADOC, A &BDOC 및 NRDOC는 각각 0.6, 0.2, 0.1 및 1.0 mg/L 정도 오존처리에 의하여 감소되었으나 BDOC는 0.8 mg/L 증가하였다. UV254/DOC의 분율은 오존주입농도를 1, 3 및 5 mg/L처리하였을 때 전오존의 경우는 각각 0.048, 0.044 및 0.037 이였고, 후오존의 경우는 각각 0.018, 0.015 및 0.012로 나타나 오존주입농도가 증가할수록 감소하는 경향을 보였다. 초기 DOC mg당 소비되는 오존량에 대한 DOC 제거율은 전오존과 후오존처리의 초기 DOC에 대한 소비오존량이 각각 약 1.5와 2.3일 때 각각 25%와 32%로 서 최대의 DOC 처리효율을 나타내었다. 낙동강 상수원수에 전오존을 처리할 경우 오존주입량은 초기 DOC mg당 소비된 오존이 1.5 mg 이내의 농도가 되도록 주입하구 후오존은 유입수인 모래여과수의 초기 DOC mg당 소비된 오존이 2.3 mg 이내의 농도가 되도록 조절하여 주입하면 적당할 것으로 생각되었다.

• 상하수도학회지
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• 제18권1호
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• pp.73-80
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• 2004

This study investigated the phenomena of membrane fouling by NOM and the effect of the fouling on removal of micro-pollutants. NOM has a great effect on decline of permeate flux. Permeate flow rate was reduced by 88% in RO and 34.8% in NF for 323hr operation period. Removal rate of $UV_{254}$, is 87.4% in RO and 78.5% in NF and removal rate of DOC is 42.7% in RO and 32.9% in NF for 2mg/l humic acid. Removal efficiency of the micro-pollutants by the RO and NF membranes fouled by humic acid was mostly lower than that by the new membrane. The concentration polarization which affects the flux and the rejection was thought to occur in the active layer of the membrane, as the membrane was getting fouled.

• 상하수도학회지
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• 제26권5호
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• pp.659-668
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• 2012

In Korea, almost every water treatment plant suffers from seasonal problem of algae and turbidity which result from eutrophication and heavy rainfall. To relieve this problem, experimental investigation was performed to study the applicability of a floating-media and sand filter to preliminary water treatment in terms of algae and turbidity removal. Experimental results using pure-cultured algae influent showed that the shape of algae species as well as filtration velocity affects the removal efficiency. From the experiments using natural river water, it was concluded that algae removal is more sensitive to floating-media depth but turbidity more sensitive to sand depth. As the filtration velocity increased, the removal of turbidity decreased but that of algae was not affected. The floating-media and sand filter removed more than 30 % of TP, TN, turbidity, Chl-a and CODcr, and less than 20 % of DOC and $UV_{254}$.