Activity Coefficients and Coulombic Correction Factor for Surface Complexation Modeling

In Hyoung Rhee 한국산학기술학회 2002 한국산학기술학회논문지 Vol.3 No.2

Surface complexation models employ mass taw equations to describe the reaction of surface functional groups with ions in the solution and also Gouy-Chapman theory to consider the electrostatic effects in the surface reactions. In current surface complexation models, however, the coulombic factors used are not wholly consistent with the Gouy-Chapman model of the surface. This study was to provide the derivation of the coulombic term usually employed and then a revised coulombic term completely consistent with Gouy-Chapman Theory. The electrical potential energy, zFΨ, in current surface complexation models is not consistent with the Gouy-Chapman theory with the potential gradient close to the charged surface but with the Donnan model with the uniform potential. Even though the new coulombic factor yielded lower surface potential, it provided worse fits for acid-base titration data of the goethite suspensions.

공동주택 단지의 구성요소와 3차원 물리적 환경이지표온도에 미치는 영향 분석- 서울시 340개 공동주택 단지를 중심으로

문현빈,이수기 한국도시설계학회 2018 도시설계 : 한국도시설계학회지 Vol.19 No.6

This study examined the impacts of compositional factors and three-dimensional physical environments on surface temperature in the 340 apartment complexes in Seoul, Korea, using the satellite image data of Landsat8. The results indicated that compositional and three-dimensional physical elements are important factors that affect surface temperatures in apartment complex. The lower building footprint, the higher proportion of green space, and more shadows were critical factors for the lower surface temperature. In addition, natural environment such as wind speeds, slope, hillshade, and building direction showed statistically significant relationships with surface temperatures. Regarding three- dimensional variables, layout variables of apartment complex showed statistically significant relationships. In particular, apartment complexes with a closed layout were more likely to show higher surface temperatures than those with an open layout. In addition, this study found that surrounding environments of apartment complex such as built area ratio and distance to green space are strongly associated with surface temperatures. The analysis results will be helpful to develop mitigation strategies for the lower surface temperature and to improve thermal environment of residential apartment complexes. 본 연구는 Landsat8 고해상도 영상을 활용하여 서울시 340개 공동주택 단지의 구성요소와 3차원 물리적 환경이 공동주택 단지 내 지표온도에 미치는 영향을 분석하였다. 분석 결과, 공동주택 단지의 구성요소 및 3차원 물리적 환경이 공동주택 단지의 지표온도에 영향을 미치는 중요한 요인으로 나타났다. 우선, 건폐율이 낮을수록, 녹지율과 지표면에 생기는 그림자 면적이 높을수록 지표온도가 낮아지는 것을 확인하였다. 또한, 바람, 경사, 표고, 향 등의 자연환경과 관련된 변수 역시 지표온도에 영향을 미치는 중요한 요인으로 나타났다. 3차원 물리적 환경 변수와 관련하여 공동주택 단지의 배치 형태가 중요하게 나타났고, 외부환경에 개방된 형태보다 폐쇄된 형태에 가까울수록 지표온도가 높은 것으로 나타났다. 그리고 공동주택 단지의 내부요소뿐만 아니라 주변의 건물 비율, 녹지와의 거리 등도 지표온도와 밀접한 관계가 있음을 확인하였다. 본 연구의 결과는 여름철 공동주택 단지의 지표온도 저감과 열환경 개선을 위한 대책을 수립하는데 기여할 것으로 판단된다.

pH 4와 10에서의 3가 비소와 Two-Line Ferrihydrite의 표면반응에 대한 X선 흡수 분광 연구

이우춘 ( Woo Chun Lee ),최선희 ( Sun Hee Choi ),조현구 ( Hyen Goo Cho ),김순오 ( Soon Oh Kim ) 한국광물학회 2011 광물과 암석 (J.Miner.Soc.Korea) Vol.24 No.2

본 연구에서는 자연에서 산출빈도가 높은 3가 비소(아비산염)와 two-line ferrihydrite와의 표면흡착 반응의 기작을 살펴보기 위하여 3가 비소를 흡착시킨 two-line ferrihydrite에 대한 X선 흡수분광 분석을 수행하였다. 연구에 사용된 two-line ferrihydrite는 실험실에서 합성하여 사용하였으며, 산성과 염기성 환경에서의 표면반응 기작을 비교하기 위하여 pH 4와 10에서 연구를 수행하였다. 또한 각 pH 조건별 3가 비소의 흡착농도에 따른 표면반응의 차이를 비교 평가하였다. X선 흡수분광 분석결과에서 얻은 EXAFS영역에서의 비소 3가에 대한 구조 변수들을 살펴보면 As-O 배위수는 3.1~3.3개, 거리는 1.74~1.79 Å으로 two-line ferrihydrite 표면에 흡착된 As(III) complex의 구조 단위체가 AsO3임이 확인되었다. As(Ⅲ)-Fe쌍은 주로 안정된 형태의 bidentate binuclear corner-sharing (2C)의 결합구조를 갖는 것으로 나타났으며, bidentate mononuclear edge-sharin g(2E)와 2C가 혼합된 결합구조도 공존하는 것으로 조사되었다. pH 4에서는 흡착 농도에 따라 다른 표면구조를 가지는 반면, pH 10에서는 흡착 농도에 상관없이 동일한 표면구조를 보이는 것으로 나타났다. 이러한 결과는 3가 비소와 two-line ferrihydrite의 표면반응은 pH와 농도에 의해서 영향을 받는다는 거시적인(macroscopic) 흡착실험 연구결과가 미시적인(microscopic) X선 흡수분광 결과에 의해서 해석될 수 있음을 의미한다. X-ray absorption spectroscopy (XAS) study was conducted using arsenite-sorbed two-line ferrihydrite to investigate the mechanism of surface interactions between two-line ferrihydrite and As(III) (arsenite) which are ubiquitous in nature. The two-line ferrihydrite used was synthesized in the laboratory and the study was undertaken at pHs 4 and 10 to compare the difference in mechanisms of surface interaction between acidic and alkaline environments. The effect of arsenite-adsorbed concentrations on surface complexation was investigated at each pH condition as well. From the results of XAS analyses, the structural parameters of arsenite in the EXAFS revealed that the coordination number and distanceof As-O were 3.1~3.3 and 1.74~1.79 Å, respectively, which indicate that the unit structure of arsenite complex formed on the surface of two-line ferrihydrite is AsO3. The dominant structures of As(III)-Fe complex were examined to be bidentate binuclear corner-sharing (2C) and the mixture of bidentate mononuclear edge sharing (2E) and 2C appeared as well. At pH 4, arsenite complex showed different structures on the surface of two-line ferrihydrite, depending on the adsorbed concentrations. At pH 10, on the contrary, the surface structures of arsenite complexes were interpreted to be almost identical, irrespective of the adsorbed concentrations of arsenite. Consequently, this microscopic XAS results support the results of macroscopic adsorption experiments in which the surface interaction between arsenite and two-line ferrihydrite is significantly influenced by pH conditions as well as arsenite concentrations.

Adsorption of uranyl tricarbonate and calcium uranyl carbonate onto γ-alumina

Jo, Yongheum,Lee, Jun-Yeop,Yun, Jong-Il Elsevier 2018 Applied geochemistry Vol.94 No.-

<P><B>Abstract</B></P> <P>The uranyl tricarbonate moiety, exemplified by UO<SUB>2</SUB>(CO<SUB>3</SUB>)<SUB>3</SUB> <SUP>4−</SUP>, CaUO<SUB>2</SUB>(CO<SUB>3</SUB>)<SUB>3</SUB> <SUP>2−</SUP>, and Ca<SUB>2</SUB>UO<SUB>2</SUB>(CO<SUB>3</SUB>)<SUB>3</SUB>(aq), is potentially expected to consist of mobile uranyl(VI) species in the aquifer of a deep geological repository for spent nuclear fuel. Time-resolved laser fluorescence spectroscopy (TRLFS) for the U(VI) surface speciation on γ-alumina was utilized to investigate the effect of various uranyl tricarbonate species on U(VI) adsorption. Under the prevailing carbonate conditions, the emission bands of the species of U(VI) adsorbed onto γ-alumina were found at 467.6 ± 0.1, 487.1 ± 0.1, 507.5 ± 0.1, 530.0 ± 0.1, and 552.8 ± 0.2 nm and were blueshifted compared with those of the U(VI)-hydroxo surface complexes. The shift to the shorter wavelengths was attributed to the spectral feature of bis- and/or tris-carbonato U(VI) complexes found in aqueous uranyl(VI) species and uranium(VI) minerals with two to three carbonate ions. The results obtained from attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy have confirmed the formation of U(VI)-carbonato surface complexation on γ-alumina in a bidentate manner. Based on identical spectroscopic properties, which were observed independently of the presence or absence of calcium ions in the uranyl tricarbonate system, a similar manner of U(VI) tricarbonate adsorption can be assumed, regardless of the absence or presence of calcium. According to the results from this work and comparison with previous studies, U(VI)-carbonato surface complexation tends to be favorable on mineral surfaces with a higher point of zero charge (pH<SUB>PZC</SUB>) such as alumina. Regarding the retention of U(VI) in the aquifer, the results presented in this work provide new insight and interpretation of U(VI) adsorption in carbonate-rich groundwater.</P> <P><B>Highlights</B></P> <P> <UL> <LI> U(VI) surface speciation on γ-alumina is identified. </LI> <LI> TRLFS, ATR-FTIR, and electrophoretic mobility measurements are carried out. </LI> <LI> Blue-shifted spectra of bi/tricarbonate-like U(VI)-carbonato species are obtained. </LI> <LI> U(VI)-carbonato surface complexation on γ-alumina is revealed. </LI> </UL> </P>

Surface Complexation Model 을 이용한 양이온 중금속(Pb,Cd) 흡착반응의 모델화 연구

신용일,박상원 한국환경과학회 1999 한국환경과학회지 Vol.8 No.2

Surface complexation models(SCMs) have been performed to predict metal ion adsorption behavior onto the mineral surface. Application of SCMs, however, requires a self-consistent approach to determine model parameter values. In this paper, in order to determine the metal ion adsorption parameters for the triple layer model(TLM) version of the SCM, we used the zeta potential data for Zeolite and Kaolinite, and the metal ion adsorption data for Pb(Ⅱ) and Cd(Ⅱ). Fitting parameters determined for the modeling were as follows ; total site concentration, site density, specific surface area, surface acidity constants, etc. Zeta potential as a new approach other than the acidic-alkalimetric titration method was adopted for simulation of adsorption phenomena. Some fitting parameters were determined by the trial and error method. Modeling approach was successful in quantitatively simulating adsorption behavior under various geochemical conditions.

Enhancing the Wettability of Fibre Surface: A Comparative Experimental Study of Different Surface Activation Principles on Single Polyamide Fibre

Carolin Gleissner,Thomas Bechtold,Tung Pham 한국섬유공학회 2023 Fibers and polymers Vol.24 No.12

In this study, we have compared three different principles of surface activation with regard to their effects on the properties of single polyamide fibres. The techniques used include the complexation-mediated surface treatment using CaCl2/EtOH/H2O solution (CEW), the atmospheric pressure plasma treatment with air (APPA) and grafting polymerisation process with 2- hydroxyethyl methacrylate (HEMA). The CEW modification, the plasma treatment and the grafting process induced a decrease in advancing contact angle and thus led to an improved wettability of the polyamide fibre. While for the CEW treatment, the decrease was solely due to a change in topography such as increased surface roughness leading to increased capillary effect, for the APPA and grafting technique the decrease was attributed to a combination of increased surface roughness and increased amount of oxygen or nitrogen-containing groups as detected by XPS. In addition, the fibre fineness decreased in the case of CEW treatment due to a dissolution of polyamide segments during the modification, while it increased in the grafting process due to an additional grafted layer. However, an increase in wetted length was observed for most samples, which was attributed to the increased waviness of the fibres. All treatments induced a decrease in fibre tensile strength that decreased with increasing treatment intensity.

Land Surface Temperatures of Industrial Complexes in Jeonnam Using Landsat 7 ETM+ Satellite Images

Nguyen Truong Linh,Tran Quang Huy,허정원,한동엽 한국지역학회 2015 지역연구 Vol.31 No.3

Observation of land surface temperature in industrial areas is problematic, as it is not possible to construct a network of weather stations with sufficiently high density and continuous operation in such zones. Multiphase remote sensing data that cover a wide area and take a short time to process can enable the user to precisely and continuously measure the current and changing land surface temperatures in a certain region. Jeollanam-Do in South Korea is undergoing rapid industrialization, with the establishment of a number of industrial complexes, such as the Gwangyang Steelworks, Yeosu Industrial Complex, Yulchon Industrial complex, and Daebul Industrial Complex. To look into the properties of industrial complex’s temperature, this study uses the thermal band of Landsat 7 ETM+ images acquired under thermal infrared wavelengths in order to calculate and compare the surface temperatures of the four above-named industrial complexes. From this, it is possible to obtain the basic information about industrial complex for environmental and natural resource management, which will aid industrial complex planners in developing methods of addressing environmental problems.

Mechanisms of antimony adsorption onto soybean stover-derived biochar in aqueous solutions

Vithanage, M.,Rajapaksha, A.U.,Ahmad, M.,Uchimiya, M.,Dou, X.,Alessi, D.S.,Ok, Y.S. Academic Press 2015 Journal of environmental management Vol.151 No.-

Limited mechanistic knowledge is available on the interaction of biochar with trace elements (Sb and As) that exist predominantly as oxoanions. Soybean stover biochars were produced at 300 <SUP>o</SUP>C (SBC300) and 700 <SUP>o</SUP>C (SBC700), and characterized by BET, Boehm titration, FT-IR, NMR and Raman spectroscopy. Bound protons were quantified by potentiometric titration, and two acidic sites were used to model biochar by the surface complexation modeling based on Boehm titration and NMR observations. The zero point of charge was observed at pH 7.20 and 7.75 for SBC300 and SBC700, respectively. Neither antimonate (Sb(V)) nor antimonite (Sb(III)) showed ionic strength dependency (0.1, 0.01 and 0.001 M NaNO<SUB>3</SUB>), indicating inner sphere complexation. Greater adsorption of Sb(III) and Sb(V) was observed for SBC300 having higher -OH content than SBC700. Sb(III) removal (85%) was greater than Sb(V) removal (68%). Maximum adsorption density for Sb(III) was calculated as 1.88 x 10<SUP>-6</SUP> mol m<SUP>-2</SUP>. The Triple Layer Model (TLM) successfully described surface complexation of Sb onto soybean stover-derived biochar at pH 4-9, and suggested the formation of monodentate mononuclear and binuclear complexes. Spectroscopic investigations by Raman, FT-IR and XPS further confirmed strong chemisorptive binding of Sb to biochar surfaces.

Synthesis and use of new porous metal complexes containing a fusidate moiety as gas storage media

Zinah Nazih Mahmood,Mahasin Alias,Gamal Abdel-Rahman El-Hiti,Dina Saadi Ahmed,Emad Yousif 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.1

The burning of fossil fuels produces carbon dioxide emissions, increased levels of which cause serious environmental problems. Therefore, the design and use of new materials as media for capturing carbon dioxide and other gases, such as hydrogen and methane, has attracted significant research attention. In this work, three metal complexes containing a fusidate moiety were synthesized and tested as storage media for gases. By reacting sodium fusidate and metal chlorides in boiling ethanol, the corresponding metal complexes were obtained with 69-76% yields. The fusidate moiety acts as a bidentate ligand with variable geometry (distortion octahedral, square planner, or tetrahedral) depending on the metal (manganese, copper, or zinc, respectively) it is associated with. The elemental composition of the metal complexes was confirmed via energy dispersive X-ray spectroscopy and their surface morphology was inspected via field emission scanning electron microscopy. The Brunauer-Emmett-Teller surface area of the metal complexes varied from 31.2 to 46.9m2/g, with pore volume and diameters of 0.035-0.049 cm3/g and 3.02-3.18 nm, respectively. The gas uptake at 323 K for carbon dioxide, hydrogen, and methane depended on the metal, gas, surface pore volume, and pore diameter. Reasonable carbon dioxide uptake (6.3-7.2wt%) was achieved with fusidate metal complexes at high temperature and pressure, whereas hydrogen and methane slowly permeated throughout the complexes.

Anionic Indicators on the Surface of Submicrospheres Consisting of Ionic Palladium(II) Complex

Cho Rong Kim,노태환,유경호,유복렬,정옥상 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

Ionic palladium(II) complex, [(Me4en)Pd(L)]2(ClO4)4 (Me4en = N,N,N’,N’-tetramethylethylenediamine; L = bis- (4-(4-pyridylcarboxyl)phenyl)methane), allows to form a monodisperse submicrosphere without any template or additive. Surface-perchlorates on the submicrosphere have been exchanged by anionic pH indicators such as thymol blue, bromothymol blue, and bromocresol green. The ionic and amphiphilic properties of the palladium(II) complex appear to be primarily associated with the formation and easy surface-anion exchange of submicrosphere. The surface-anion exchange through the electrostatic interaction is a very good tool for the surface-modification. The color of the pH indicator-exchanged submicrospheres is very sensitive to pH and Hg2+ cation, and thus they are promising to submicrospherical indicators.