• Membrane and Water Treatment
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• 제8권3호
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• pp.259-277
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• 2017

Adsorption is a widely used technique for the removal of dyes from wastewaters by variety of adsorbents. In this work, the main focus is on the potential assessment of anion exchange membrane for the removal of different dyes using batch system and investigation of experimental data by applying various kinetic and thermodynamic models. The removal of anionic dyes i.e., Eosin-B, Eriochrome Black-T and Congo Red by anion exchange membrane BII from aqueous solution was carried out and effect of various parameters such as contact time, membrane dosage, temperature and ionic strength on the percentage removal of anionic dyes was studied. The experimental data was assessed by kinetic models namely pseudo-first-order, pseudo-second-order, Elovich liquid film diffusion, Bangham and the modified Freundlich models equation have been used to analyze the experimental data. These results indicate that the adsorption of these anionic dyes on BII follows pseudo-second-order kinetics with maximum values of regression coefficient (0.992-0.998) for all the systems. The adsorption of dyes was more suitable to be controlled by a liquid film diffusion mechanism. The adsorptive removal of dye Eosin-B and Eriochrome Black-T were decreased with temperature and thermodynamic parameters such as free energy (${\Delta}G^o$), enthalpy (${\Delta}H^o$) and entropy (${\Delta}S^o$) for adsorption of dyes on membrane BII were calculated at 298 K, 308 K and 318 K. The values of enthalpy and entropy were negative for EB and EBT representing that the adsorption of these dyes on BII is physiosorptive and exothermic in nature. Whereas the positive values of enthalpy and entropy for CR adsorption on BII, indicating that its adsorption is endothermic and spontaneous in nature. It is evident from this study that anion exchange membrane has shown good potential for the removal of dyes from aqueous solution and it can be used as adsorbent for dues removal on commercial levels.

• Journal of Pharmaceutical Investigation
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• 제20권3호spc1호
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• pp.51-76
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• 1990

It is sometimes said lately that the pH of the human gastric juice is significantly different among individuals. Thus, the dissolution behavior of coated solid dosage forms should preferably be independent of the pH of the test solution. With these points as a background, the effect of pH on the dissolution velocity of coated tablets was studied to compare that of Pharmacoat with other gastric soluble film coating materials. Three viscosity types of Pharmacoat have been available(3, 6 and 15cP) until now. the 6cP type has been considered to be the most suitable for a tablet coating amongst the three types. The 3 cP type with a low degree of polymerization, is capable of providing high concentration, but the film strength is so inferior that sometimes cracking of the film may occur. On the other hand, in the case of the 15cP type, high polymer concentration cannot be achieved because of the high dgree of polymerization, and thus it is uneconomical for coating. Now, there is a strong demand to reduce the coating time even when HPMC is used in the 6cP type in order to reduce the coating cost. In order to improve this problem, we have concentrated our attention on reducing the viscosity value of HPMC to an allowable lower limit from 6cP. As a result of this study, it was found that the reduction of the viscosity value to around 4.5cP enabled the use of a higher solution concentration and an incidental shorter coating time without giving any substantial adverse effects on the properties of coated preparations. These experiment results are presented in the later part of this presentation. Based on this study, we have added the viscosity type of 4.5cP as one of the Pharmacoat products as Pharmacoat-645.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2011년도 춘계학술발표회 논문집
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• pp.169-169
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• 2011

Xylans are polysaccharides present in large amounts in cell walls of land plants. However, during kraft cooking, a high portion of hemicelluloses including xylans are dissolved in the cooking liquor. In the current trend for a more effective utilization of biomass, attention has been paid to the exploitation of xylans as strength-enhancing additives for paper. It is believed that surface xylan adds flexibility to the cell wall/fiber surface, resulting in stronger fiber-fiber joints or greater contact area between the fibers. Accordingly, there is proposal for a new pulping process involving the extraction of xylan prior to pulping, followed by their re-adsorption on the unbleached pulp. A suitable bleaching process should be employed then, which ought to does not only improve the brightness of the pulp, but also remain the effect of the adsorption of xylan on pulp fibers. The objective of this research was to investigate the impact of hydrogen peroxide bleaching on the properties of unbleached hardwood kraft pulp pretreated with birchwood xylan by measuring optical properties (brightness, post color number, opacity) as well as physical properties (tensile index, tearing index, bulk) of handsheets made from the bleached pulp. In the meantime, the influence of process variables of peroxide bleaching including bleaching temperature, time, initial pH and $MgSO_4$ dosage were studied.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.919-922
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• 2008

본 연구는 최근 국내 공동주택 지하주차장 등에 설치하는 지연 조인트에 적용할 콘크리트의 수축저감을 위한 연구로서, 팽창재와 3가지의 수축저감제를 단독 또는 병용하여 혼입할 경우 콘크리트의 물리적 특성 및 수축 특성에 대해 검토하기 위해 수행되었다. 실험 결과, 팽창재는 굳지않은 콘크리트의 유동성에 큰 영향을 미치지 않으나, 수축저감제의 경우콘크리트의 유동성을 증진시켜 고성능 감수제의 혼입량을 0.05$\sim$0.1% 정도 감소시킬 수 있다. 또한 팽창재를 혼입할 경우 경화 콘크리트의 압축, 인장 및 휨강도는 다소 증가하는 경향을 보였지만, 수축저감제를 단독 또는 팽창재와 병용 혼입한 경우에는 압축, 인장 및 휨강도가 다소 감소하는 경향을 보였다. 건조수축에 의한 길이변화율 측정결과, 수축저감제 중 SRA3을 2.0% 혼입한 경우 길이변화율 감소 효과가 가장 우수하였으며, 팽창재를 단독으로 사용하거나 팽창재와 SRA1, 2, 3을 병용 혼입한 경우에는 비슷한 감소 효과를 보였다.

• 콘크리트학회논문집
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• 제28권1호
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• pp.41-48
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• 2016

본 연구는 두 종류의 수축저감제를 혼입한 변형경화형 시멘트 복합체(SHCC)의 압축, 인장 및 휨 특성을 평가하기 위하여 계획되었으며, 재령과 수축저감제의 종류 및 혼입률을 변수로 진행되었다. SHCC는 설계기준압축강도 50 MPa이며, 섬유는 PVA 섬유를 2.2% 혼입하였다. 배합에 혼입된 수축저감제는 상변이 물질로 수화현상으로 발생되는 열을 흡수 또는 방출하여 급격한 수축 및 팽창을 제어하는 물질이다. 수축저감제의 혼입에 대한 영향은 선변형 길이변화 실험과 압축, 인장 및 휨 성능의 측면에서 평가되었으며, 수축저감제를 혼입할 경우 초기 재령에서의 수축량이 감소되었다. 또한 수축저감제를 혼입함에 따라 균열 분산 성능과 인장 및 휨 성능이 개선되었다.

• 한국환경과학회지
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• 제22권8호
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• pp.1009-1017
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• 2013

Perfluorooctanoic acid (PFOA) and perfluorooctyl sulfonate (PFOS) is a new persistent organic pollutants of substantial environmental concern. This study investigated the potential of magnetic ion exchange resin (MIEX$^{(R)}$) as the adsorbent for the removal of PFOA and PFOS from Nakdong River water. In our batch experiments, we studied the effect of some parameters (pH, temperature, sulfate concentration) on the removal of PFOA and PFOS. The results of sorption kinetics on MIEX$^{(R)}$ show that it takes 90 min to reach equilibrium but the economical contact time and dosage were 30 min and 10 mL/L. An increase in pH (pH 6~10) leads to a decrease in PFOA (2.0%) and PFOS (3.6%) sorption on MIEX$^{(R)}$. The sorption of both PFOA and PFOS decreases with an increase in ionic strength for sulfate ion (${SO_4}^{2-}$), due to the competition phenomenon. An increase in water temperature ($8^{\circ}C{\sim}28^{\circ}C$) in water leads to a increase in PFOA (2.8%) and PFOS (4.3%) sorption on MIEX$^{(R)}$. Based on the sorption behaviors and characteristics of the adsorbents and adsorbates, ion exchange and hydrophobic interaction were deduced to be involved in the sorption, and hemi-micelles possibly formed in the intraparticle pores.

• 한국건설순환자원학회논문집
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• 제1권3호
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• pp.181-188
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• 2013

본 연구에서는 CASB-SP가 블랙 콘크리트의 기초적 물성 및 발색도에 미치는 영향을 실험적으로 고찰하고자 하였다. 실험변수로서 CASB-SP와 기존 Carbon black의 두 착색제 종류에 따라 치환율을 변화시키고 이후 백화방지를 위해 4수준의 발색제를 변수로 설정하였다. 연구결과에 따르면, 전반적으로 CASB-SP 혼입율이 증가할수록 슬럼프 및 공기량이 증가하는 경향으로 나타났고, 응결시간은 0.75% 이상 사용시 기존 Plain에 비해서 현저히 지연되는 것으로 나타났으며 블리딩은 CASB-SP 혼입율이 증가 할수록 감소되었다. 압축강도는 CASB-SP 혼입율이 증가할수록 압축강도가 증가하였고, 발색도는 CASB-SP 혼입율이 증가할수록 검정색 발현이 선명해지는 것으로 나타났고, 발색제의 사용에 따라 백화가 방지되어 안정적인 색상유지가 가능해졌다. 이상을 종합하면, 블랙 콘크리트에 CASB-SP를 사용할 경우 Carbon Black에 비해 콘크리트의 품질향상 차원에서 유리한 것으로 나타났고, CASB-SP 혼입율은 콘크리트의 품질을 고려하여 0.5% 혼입하는 것이 가장 양호한 것으로 분석된다.

• 대한토목학회논문집
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• 제2권2호
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• pp.47-59
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• 1982

콘크리트공학 분야에서는 된반죽콘크리트의 시공성(施工性)을 개선(改善)하며 묽은반죽콘크리트의 품질향상(品質向上)을 위한 목적으로 유동화제(流動化劑)를 사용한 콘크리트에 관한 연구(硏究)가 활발히 진행되고 있다. 본(本) 논문(論文)에서는 단위시멘트량 400kg, 슬럼프 $19{\pm}1cm$의 범위에 있는 유동화콘크리트의 최적배합(最適配合)을 구하기 위하여 잔골재율, 단위수량 및 유동화제의 사용량을 변화시킨 콘크리트에 대하여 굳지않은 콘크리트 및 경화한 콘크리트의 제(諸) 성질(性質)로써 비교 검토하였다. 또한 이 실험에서 구한 유동화(流動化)콘크리트와 동일 슬럼프의 묽은 반죽콘크리트, 그리고 베이스콘크리트의 제 성질을 비교 고찰해 봄으로써 유동화콘크리트의 배합 및 강도 등에 관한 유익(有益)한 기초자료(基礎資料)를 얻었다. 한편 유동화콘크리트의 시공시 문제점으로 지적되고 있는 믹싱후 경과시간(經過時間)에 따른 슬럼프저하(低下)의 방지(防止)에 대해서도 고찰 했다.

• Advances in concrete construction
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• 제9권2호
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• pp.195-205
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• 2020

In this study, effect of recycled aggregates and polypropylene fibers on the response of conventionally reinforced concrete element subjected to tensile loading in terms of tension stiffening and strain development was experimentally investigated. For this purpose, concrete prisms of 100 × 100 mm cross section and 500 mm length having one central deformed steel re-bar were cast using fibrous and non-fibrous Recycled Aggregate Concrete (RAC) with varying percentages of recycled aggregates (0%, 25%, 50%, 75% and 100%) and tested under uniaxial tensile load. For all fibrous RAC mixes, polypropylene fibers were used at constant dosage of 3.15 kg/㎥. Effect of recycled aggregates and fibers on the compressive strength of concrete was also explored in this study. Through studying tensile load versus global axial deformation of composite and strain development in concrete and steel, it was found that replacement of natural aggregates with recycled aggregates in concrete negatively affected the cracking load, tension stiffening and strain development, and this negative effect was observed to be increased with increasing contents of recycled aggregates in concrete. The results of this study showed that it was possible to minimize the negative effect of recycled aggregates in concrete by the addition of polypropylene fibers. Reinforced concrete element constructed using concrete containing 50% recycled aggregates and polypropylene fibers exhibited cracking behavior, tension stiffening and strain development response almost similar to that of concrete element constructed using natural aggregate concrete without fiber.

• 한국도로학회논문집
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• 제19권1호
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• pp.53-62
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• 2017

PURPOSES : This research was a fundamental study on the application of an integral $TiO_2$ solution to asphalt concrete pavement. The integral $TiO_2$ solution was produced in pilot production equipment; application of the integral $TiO_2$ solution to asphalt pavement was conducted to examine the pollution-reducing capability of photocatalytic compounds such as $TiO_2$. The photocatalytic $TiO_2$ reacted with air pollutants, converting them into small amounts of relatively benign molecules. METHODS : In this study, laboratory experiments were conducted using five various testing methods. Tensile strength ratio (TSR) and British pendulum test (BPT) were conducted in order to evaluate the properties of asphalt pavement subsequent to the integral $TiO_2$ solution coating. In addition, methylene blue testing, a measurement of nitrate on the coated pavement, and nitrogen oxide (NOx) reduction testing were conducted in order to evaluate photocatalytic reaction. Lastly, a UV-A lamp was used as a light source for photocatalytic reactions. RESULTS : Test results indicated no change in the properties of asphalt pavement following the integral $TiO_2$ solution coating. In order to evaluate the performance of asphalt pavement as a function of $TiO_2$, the moisture susceptibility and skid resistance were investigated. The moisture susceptibility and skid resistance satisfied there quirements related to pavement quality and safety specification. Furthermore, the effects of reduction of air pollution were significantly improved as determined via the methylene blue test and NOx reduction test. The $TiO_2$-paved asphalt specimen exhibited approximately 43% reduction of NOx. CONCLUSIONS : This study has suggested that applying $TiO_2$ rarely impacts asphalt pavement performance measures such as moisture susceptibility and skid resistance, and that its application may be a better means of reducing air pollution. Further studies, such as proper $TiO_2$ dosage rates and compatibility with various pavement types, are required to broaden and generalize its application.