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1
Yeo, In Hwan, Kyu Jae Hwang, Jae Hong An und Jong Ho Lee. „A Study on Heat Transfer Analysis and Experiment of Reinforced Concrete Columns Using 500°C Isotherm Method“. Advanced Materials Research 905 (April 2014): 249–53. http://dx.doi.org/10.4028/www.scientific.net/amr.905.249.
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This study aims to assess heat transfer analysis of RC columns and unstressed test by applying 500°C isotherm method, which is the strength deterioration estimation method of Eurocode, inorder to use it as basic data for fire engineering design. According to the heat transfer analysis and fire resistance experiment, it was decided an appropriate axial ratio of RC columns that have cross sections of 300 and 350 can be anticipated as 0.49 and 0.59.
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ARAÚJO, D. L., und G. D. C. PINTO. „Fire behavior of shallow prestressed hollow core slabs from computational modeling“. Revista IBRACON de Estruturas e Materiais 13, Nr. 2 (April 2020): 398–432. http://dx.doi.org/10.1590/s1983-41952020000200011.
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Abstract Prestressed hollow core slabs are one of the structural systems whose use has increased the most in recent years in Brazil due to its efficiency and versatility. They can be used in many types of structural systems, such as masonry, precast concrete, cast-in-place concrete and steel structures. However, there are few analytical models to evaluate the fire behavior of hollow core slabs. In a simplified way, the fire resistance is evaluated indirectly through the minimum distance of the surface in contact with fire to the reinforcement axis. In this paper, some numerical models in finite element software were developed to analyze the variation of temperature with fire exposure time of shallow hollow core slabs, focusing on the presence of voids in the transversal section of the slab. The 500 °C isotherm method applied to 20 cm high slabs confirmed the Standard Fire Resistance obtained from the tabular method. However, when applied to shallow prestressed hollow core slabs that are 16 cm high, the 500 °C isotherm method indicated that the Standard Fire Resistance of these slabs is lower than values obtained from tabular methods.
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SUAZNABAR, J. S., und V. P. SILVA. „Combined axial and flexural loads in short reinforced concrete columns in fire: ultimate limit state curves using 500 °C isotherm method“. Revista IBRACON de Estruturas e Materiais 11, Nr. 1 (Februar 2018): 163–82. http://dx.doi.org/10.1590/s1983-41952018000100009.
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Abstract Ultimate limit state curves of short reinforced concrete columns in fire situation are going to be presented in this paper. The authors created a code developed in Matlab. It makes a discretization of the cross sections of the columns and calculates the equilibrium integrals of them. The curves were plotted with the code considering the 500 °C isotherm method.
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Maciąg, Michał, und Szymon Spodzieja. „Designing reinforced concrete slabs under fire condition“. MATEC Web of Conferences 196 (2018): 02036. http://dx.doi.org/10.1051/matecconf/201819602036.
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In this article the capacity of reinforced concrete slabs of thickness larger than 15 cm was calculated with Isotherm 500 Method. For designed elements were analysed the support and span zone. There have been proposed tables for designers, on which basis it is possible to design slab of demanded fire capacity.
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Jaszczak, Bogusz, Mieczysław Kuczma und Wojciech Szymkuć. „Comparison of the load-bearing capacity of reinforced concrete columns under fire conditions using the method A, zone method and isotherm 500 method“. Fire Safety Journal 124 (September 2021): 103396. http://dx.doi.org/10.1016/j.firesaf.2021.103396.
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Dinh Du, Pham, Nguyen Trung Hieu, Thuy Chau To, Long Giang Bach, Mai Xuan Tinh, Tran Xuan Mau und Dinh Quang Khieu. „Aminopropyl Functionalised MCM-41: Synthesis and Application for Adsorption of Pb(II) and Cd(II)“. Advances in Materials Science and Engineering 2019 (19.02.2019): 1–15. http://dx.doi.org/10.1155/2019/8573451.
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This paper shows a comparison of porous properties of aminopropyl-MCM-41 materials functionalised via the direct and indirect methods. The obtained materials were characterised using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis-differential scanning calorimeter (TGA-DSC), adsorption/desorption isotherms of nitrogen, and Fourier-transfer infrared (FT-IR) spectroscopy. The results showed that the direct method provided the aminopropyl-MCM-41 material with well-ordered pores and high surface areas but with a lower quantity of grafted 3-aminopropyltriethoxysilane than the indirect method. To remove the organic template in the indirect method, solvent extraction with HCl/C2H5OH and calcination at 500°C were used, and the former gave a higher quantity of grafted 3-aminopropyltriethoxysilane in the resulting aminopropyl-MCM-41 materials. The experimental data were applied to the isotherm models of adsorption including Langmuir, Freundlich, Redlich–Peterson, and Sips either in the linear or nonlinear form. In order to avoid the bias of the determination coefficient and the error function method, the paired-samples t-test as an alternative method was first proposed to look for the most appropriate adsorption isotherms. The maximum adsorption capacity of Cd(II) and Pb(II) was 14.08 mg·g−1 and 64.21 mg·g−1, respectively. The mechanism of complexation and isoelectric interaction was suggested to explain the adsorption of Pb(II) and Cd(II) from aqueous solutions on aminopropyl functionalised MCM-41 in the range of pH from 2 to 9.
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Xu, Shun Jian, Guan Jun Qiao, Di Chen Li, Hong Jie Wang und Tian Jian Lu. „Using of Ethylene Glycol as Pore-Form Agent to Form Interconnected Mesopores in Carbonized Phenol Resin“. Materials Science Forum 569 (Januar 2008): 265–68. http://dx.doi.org/10.4028/www.scientific.net/msf.569.265.
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We used ethylene glycol as pore-forming agent to prepare porous carbon with interconnected pores derived from phenol–formaldehyde resin. The mixture of resins and glycol was by polymerization and pyrolysis monolithic material of porous carbon with interconnected mesopores and a narrow pore size range. The average pore size of the porous carbon obtained was 28.2 nm. The nitrogen adsorption isotherm for the porous carbon exhibited type IV isotherm, which corresponded to mesoporous adsorption. The method could endow porous carbon with BET surface area and pore volume about 500 m2/g and 0.607 cm3/g, respectively. The mesopores in porous carbon formed as a result of phase separation of resin-rich phase and glycol-rich phase at polymerization and remove of glycol-rich at subsequent pyrolysis.
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Romatschke, Ulrike. „Melting Layer Detection and Observation with the NCAR Airborne W-Band Radar“. Remote Sensing 13, Nr. 9 (24.04.2021): 1660. http://dx.doi.org/10.3390/rs13091660.
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A melting layer detection algorithm is developed for the NCAR 94 GHz airborne cloud radar (HIAPER CloudRadar, HCR). The detection method is based on maxima in the linear depolarization ratio and a discontinuity in the radial velocity field. A melting layer field is added to the radar data, which provides detected, interpolated, and estimated altitudes of the melting layer and the altitude of the 0 °C isotherm detected in model temperature data. The icing level is defined as the lowest melting layer, and the cloud data are flagged as either above (cold) or below (warm) the icing level. Analysis of the detected melting layer shows that the offset between the 0 °C isotherm and the actual melting layer varies with cloud type: in heavy convection sampled in the tropics, the melting layer is found up to 500 m below the 0 °C isotherm, while in shallow clouds, the offset is much smaller or sometimes vanishes completely. A relationship between the offset and the particle fall speed both above and below the melting layer is established. Special phenomena, such as a lowering of the melting layer towards the center of storms or split melting layers, were observed.
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Novakovic, Tatjana, Ljiljana Rozic, Srdjan Petrovic, Zorica Vukovic und Vera Dondur. „Pore surface fractal analysis of PEG and La(III)-doped mesoporous alumina obtained by the sol-gel method“. Journal of the Serbian Chemical Society 75, Nr. 6 (2010): 833–43. http://dx.doi.org/10.2298/jsc090922053n.
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Active porous alumina was prepared via a sol-gel method and subjected to thermal treatment in the temperature range 500-1200 ?C. The addition of lanthanum effectively inhibited the surface area loss of the aluminas. Fractal analysis from nitrogen adsorption isotherm was used to study the pore surface roughness of alumina samples with different chemical compositions (PEG, PEG and lanthanum) and calcinations conditions in terms of the surface fractal dimension, d. The Mahnke and M?gel (MM) model was used to determine the value of d of La(III)-doped alumina. Following the MM model, the d value of the activated aluminas increased as the calcination temperature increased from 500 to 700 ?C but decreased after calcination at 1000, 1100 and 1200 ?C. The addition of polyethylene glycol (PEG 5600) to the boehmite sol reduced the surface fractal of the activated alumina due to the heterogeneous distribution of the pores. With increasing La(III) concentration from 0.015 to 0.045 mol La(III)/mol Al(III), the d value of La-modified alumina samples decreased, indicating a smoother surface. The obtained PEG+La-doped boehmite sol can be used as a precursor dispersion for the deposition of mesoporous alumina coatings on stainless steel foil, by the spray pyrrolysis method.
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Putri, Fami Amalia, Nur Fala Hamadi, Ajeng Y. D. Lestari, Achmad Chafidz und Tintin Mutiara. „Potential of Modified Corn Cob (Zea mays L.) and Petai Hull (Parkia hassk) as New Biosorbent for Removal of Lead Waste“. Key Engineering Materials 783 (Oktober 2018): 126–31. http://dx.doi.org/10.4028/www.scientific.net/kem.783.126.
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Lead metal is one type of heavy metal that has high toxicity levels in the aquatic waste environment. The adsorption method is one of the alternatives in reducing heavy metal waste, by utilizing biosorbent. The purpose of this research is to study the process of making new biosorbent and to know the absorption of new biosorbent from corn cob (Zea mays L.) and petai hull (Parkia hassk) to dissolve lead metal waste (Pb). There are two types of biosorbents are ordinary (simplicia) biosorbents and modified biosorbents with nitric acid (HNO3). Synthetic waste is used in the form of Pb (II) metal ions from the Pb (NO3)2 solution using initial concentrations of 100, 200, 300, 400, and 500 mg / L. Biosorbents tested the concentration of metal ions with AAS and characterized using FTIR to determine functional groups. Maximum adsorption capacity was obtained by biosorbents D (simplicia) and H (HNO3) with Pb (II) adsorbed metal ion capacity of respectively 1.4175 mg/g and 2.230 mg/g at a concentration of 400 mg / l. The isotherm adsorption showed that the adsorption mechanism of Pb(II) ion fit for this study is seen from the values of R2 on C biosorbents is better with other adsorbents and respectively are followed Langmuir, Dubinin Radushkevich, Freundlich, and Langmuir isotherm adsorption.
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Hu, Jian-ying, Takako Aizawa und Yasumoto Magara. „Evaluation of adsorbability of pesticides in water on powdered activated carbon using octanol-water partition coefficient“. Water Science and Technology 35, Nr. 7 (01.04.1997): 219–26. http://dx.doi.org/10.2166/wst.1997.0280.
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The 1-octanol-water partition coefficients (logPow) of seven pesticides, i.e., Hymexazol, methomyl, imidacloprid, thiophanatemethyl, carbaryl, linuron, thiobencarb, were determined by RPHPLC method. The relation between these estimated logPow and adsorption isotherm parameters on powdered activated carbon was studied by correlating their logPow values with the Freundlich adsorption parameters. The adsorption parameter, logk, was found to increase with the increase of logPow for the pesticides examined. The activated carbon amount needed for lowering pesticide concentration from 500 μg/l to 50 μg/l was calculated. The amount of activated carbon needed for hymexazol (logPow, 0.11) was 688.5 mg/l, while that for thiobencarb (logPow, 3.78) was 5.1 mg/l, which suggests that pesticides with a high polarity, i.e., a low Pow, are difficult to remove by powdered activated carbon.
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Deng, Hua, Qiuyan Li, Meijia Huang, Anyu Li, Junyu Zhang, Yafen Li, Shuangli Li, Caiyan Kang und Weiming Mo. „Removal of Zn(II), Mn(II) and Cu(II) by adsorption onto banana stalk biochar: adsorption process and mechanisms“. Water Science and Technology 82, Nr. 12 (10.11.2020): 2962–74. http://dx.doi.org/10.2166/wst.2020.543.
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Abstract Low-cost banana stalk (Musa nana Lour.) biochar was prepared using oxygen-limited pyrolysis (at 500 °C and used), to remove heavy metal ions (including Zn(II), Mn(II) and Cu(II)) from aqueous solution. Adsorption experiments showed that the initial solution pH affected the ability of the biochar to adsorb heavy metal ions in single- and polymetal systems. Compared to Mn(II) and Zn(II), the biochar exhibited highly selective Cu(II) adsorption. The adsorption kinetics of all three metal ions followed the pseudo-second-order kinetic equation. The isotherm data demonstrated the Langmuir model fit for Zn(II), Mn(II) and Cu(II). The results showed that the chemical adsorption of single molecules was the main heavy metal removal mechanism. The maximum adsorption capacities (mg·g−1) were ranked as Cu(II) (134.88) > Mn(II) (109.10) > Zn(II) (108.10)) by the single-metal adsorption isotherms at 298 K. Moreover, characterization analysis was performed using Fourier transform infrared spectroscopy, the Brunauer-Emmett-Teller method, scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results revealed that ion exchange was likely crucial in Mn(II) and Zn(II) removal, while C-O, O-H and C = O possibly were key to Cu(II) removal by complexing or other reactions.
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Khumnuan, Chutima, Amornrat Moungon, Karine Mougin und Pornsawan Amornsakchai. „Effect of Preparation Conditions on Heavy Metal Adsorption Characteristics of Activated Carbon Prepared from Non-Fibrous Material of Pineapple Leaves“. Key Engineering Materials 824 (Oktober 2019): 114–20. http://dx.doi.org/10.4028/www.scientific.net/kem.824.114.
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Activated carbon can be prepared from any kind of hydrocarbon-based material, and that from agricultural wastes is attractive for many reasons. The use of natural fiber in various industries gives rise to some associated waste streams. In this work, activated carbon, produced from the non-fibrous material waste from pineapple leaf fiber production, was studied for its heavy metal adsorption behavior. The material was carbonized at different temperatures and chemical activation was carried out using phosphoric acid. Pore size and pore volume of the adsorbent were determined using the Brunauer–Emmett–Teller (BET) method, and surface morphology by scanning electron microscopy (SEM). Fourier Transform Infrared Spectrophotometry (FT-IR) was used to identify the functional groups in the material. It was found that the surface area, pore volume and morphology of the surface depended on the carbonization temperature. The best adsorbent was obtained using a carbonization temperature of 500 °C and an activation temperature of 600 °C. Adsorptions of several heavy metals were studied over the concentration range of 4 - 800 mg L−1 and pH 2-10. The optimum amount of the adsorbent was found to be 1.20 g per 100 ml of solution, removing up to 92.67% of lead ions. The adsorption behaviour was closer to the Freundlich isotherm than to the Langmuir isotherm. So this waste could be a useful bio-source for activated carbon production.
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Hernández-Pichardo, Marcello L., J. A. Montoya, P. Del Angel und S. P. Paredes. „Phase Stabilization of Mesoporous Mn-Promoted ZrO2: Influence of the Precursor“. Advanced Materials Research 132 (August 2010): 68–75. http://dx.doi.org/10.4028/www.scientific.net/amr.132.68.
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Mesoporous zirconia-Mn oxides were prepared by surfactant-assisted precipitation using different zirconia precursors and cetyl-trimethyl-ammonium bromide (CTAB) as a synthetic template. The objective of this work was to find out the influence of the zirconia precursors over the structural and textural characteristics of Mn-doped mesoporous zirconia solids. A series of syntheses were carried out by two methods using different zirconia precursors, modifying the Zr:surfactant ratio and the hydrolysis rate of the precipitate. After calcination at 500 °C, the samples were characterized by XRD, DTA, TEM and nitrogen adsorption-desorption isotherm. The use of the zirconium nitrate leads to materials having higher surface areas and narrow pore size distributions in the range of mesoporous materials; however, the preferential formation of the zirconia in the metaestable tetragonal phase was identified as the effect of the particle size allowed by the preparation method rather than the effect of the precursor. It was also found that the Mn and surfactant addition enhances the stabilization of the tetragonal crystalline phase and porosity.
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Akhtar, US, MK Hossain, MS Miran und MYA Mollah. „Synthesis and characterization of porous silica and polyaniline-porous silica composite materials with high surface area“. Bangladesh Journal of Scientific and Industrial Research 49, Nr. 1 (08.05.2014): 1–8. http://dx.doi.org/10.3329/bjsir.v49i1.18847.
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Porous silica materials were synthesized from tetraethyl orthosilicate (TEOS) using Pluronic P123 (non-ionic triblock copolymer, EO20PO70O20) as template under acidic conditions which was then used to prepare polyaniline (PAni) and porous silica composites (PAnisilica) at a fixed molar ratio. These materials were characterized by nitrogen adsorption-desorption isotherm measured by Barrett-Joyner- Halenda (BJH) method and pore size distribution from desorption branch and surface area measured by the Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), transmission electron microscopy (TEM), TEM-energy dispersive X-ray (EDX) and Fourier transform infrared (FT-IR) spectroscopy. The composite maintains its structure even after the polymerization and the polymer is dispersed on the inorganic matrix. The rod-like porous silica was about 1?m to 1.5 ?m long and on an average the diameter was in the range of 300- 500 nm. The SEM and TEM images show well ordered 2d hexagonal pore, high specific surface area (850 m2g-1) and uniform pore size of ca. 6.5 nm in diameter. After incorporation of PAni inside the silica pore, framework of porous silica did not collapse and the surface area of the composite was as high as 434 m2g-1 which was 5.5 time higher than our previous report of 78.3 m2g-1. Due to shrinkage of the framework during the incorporation of aniline inside the silica, the pore diameter slightly increase to 7.5 nm but still showing Type IV isotherm and typical hysteresis loop H1 implying a uniform cylindrical pore geometry. DOI: http://dx.doi.org/10.3329/bjsir.v49i1.18847 Bangladesh J. Sci. Ind. Res. 49(1), 1-8, 2014
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Doi, Koichi, Satoshi Hino, Hiroki Miyaoka, Takayuki Ichikawa und Yoshitsugu Kojima. „Thermodynamic Characterization on Hydrogen Absorption and Desorption Reactions of Lithium – Silicon Alloy“. Materials Science Forum 654-656 (Juni 2010): 2815–18. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2815.
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Lithium hydride LiH is one of the attractive hydrogen storage materials, because it stores 12.7 mass% of H2. However, H2 desorption reaction occurs over 600 °C due to the large enthalpy change of H2 desorption Ho = 181 kJ/mol H2. The purpose of this work is to control the enthalpy change of LiH to much lower value by a mechanical alloying with Si, where the Li-Si alloy is thermodynamically more stable than Li. The alloy was synthesized from Li granule and Si powder by a mechanical alloying method. The H2 absorption and desorption properties were characterized by High-Pressure Differential Scanning Calorimetry and Thermogravimetry - Differential Thermal Analysis - Mass Spectroscopy, and X-ray diffraction measurement. Pressure - Composition - Isotherm measurements were performed at 400, 450, and 500 °C to estimate the enthalpy change. From the results, it was confirmed that reversible H2 ab/desorption reactions of the Li-Si alloy were expressed as 7LiH + 3Si ↔ (3/7)Li12Si7 + (13/7)LiH + (18/7)H2 ↔ Li7Si3 + (7/2)H2 (theoretically 5.0 mass% H2) at 400 °C. From van’t Hoff plot obtained by the results of PCI measurements, the enthalpy change of the former reaction was estimated to be Ho = 103 kJ/mol H2, which is lower than that of LiH.
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Cho, Hae-Chang, Sun-Jin Han, Inwook Heo, Hyun Kang, Won-Hee Kang und Kang Su Kim. „Heating Temperature Prediction of Concrete Structure Damaged by Fire Using a Bayesian Approach“. Sustainability 12, Nr. 10 (21.05.2020): 4225. http://dx.doi.org/10.3390/su12104225.
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A fire that occurs in a reinforced concrete (RC) structure accompanies a heating temperature, and this negatively affects the concrete material properties, such as the compressive strength, the bond between cement paste and aggregate, and the cracking and spalling of concrete. To appropriately measure the reduced structural performance and durability of fire-damaged RC structures, it is important to accurately estimate the heating temperature of the structure. However, studies in the literature on RC structures damaged by fire have focused mostly on structural member tests at elevated temperatures to ensure the fire resistance or fire protection material development; studies on estimating the heating temperature are very limited except for the very few existing models. Therefore, in this study, a heating temperature estimation model for a reinforced concrete (RC) structure damaged by fire was developed using a statistical Bayesian parameter estimation approach. For the model development, a total of 77 concrete test specimens were utilized; based on them, a statistically highly accurate model has been developed. The usage of the proposed method in the framework of the 500 °C isotherm method in Eurocode 2 has been illustrated through an RC column resistance estimation application.
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Wan, Dong Jin, Dan Qu, Hua Xiao, Yong De Liu, Ting Lu und Wen Qing Xu. „Adsorption of Chloride Anion from Aqueous Solution by Calcined (Mg-Al) Hydrotalcites of Different Mg/Al Ratio“. Advanced Materials Research 233-235 (Mai 2011): 420–26. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.420.
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Hydrotalcites (HT-X) of different Mg/Al ratio (X is Mg/Al molar ratio, 3 and 4) was synthesized by co-precipitation method. Calcined HTLCs (CHT-X) at 500°C have been shown to recover their original layered structure by taking up chloride ion from aqueous solution. Adsorption of chloride by CHT-X was investigated in batch mode. The kinetics study showed that the pseudo-second-order kinetics model could be used to describe the adsorption process satisfactorily. The equilibrium isotherm showed that the Langmuir model gave a better fit to the experimental data than the Freundlich model. The maximum adsorption capacity of CHT-3 was 83.33 mg/g; CHT-4 was 90.09 mg/g .The samples of different Mg/Al ratio have different crystallite size, thus showing different adsorption capacity. As the Mg/Al ratio increases from 3 to 4; the electric charge density between the layers becomes weaker; the interlayer spacing increases; the sample shows greater adsorption capacity. The HT-X where characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDX).
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Fegade, Umesh, Sachin Kolate, Rajesh Dhake, Inamuddin, Tariq Altalhi und Suvardhan Kanchi. „Adsorption of Congo Red on Pb doped FexOy: experimental study and theoretical modeling via double-layer statistical physics models“. Water Science and Technology 83, Nr. 7 (22.02.2021): 1714–27. http://dx.doi.org/10.2166/wst.2021.077.
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Abstract Size-controlled Pb0.06Fe0.7O3 nanoparticles (Pb-FeONPs) were fabricated by the thermal co-precipitation method and characterized by FE-SEM, EDX, XRD, and IR techniques. The SEM and XRD images showed the average size distribution and average crystallite size of 19.21 nm and 4.9 nm, respectively. The kinetic model of Congo Red (CR) adsorption onto Pb-FeONPs was verified and found to be a pseudo-second-order reaction. The Langmuir plot was better fitted (R2 = 0.990) than other isotherm models with a Qmax (mg/g) of 500 for Congo Red (CR) dye in 40 min. The double-layer statistical physics model based on two energies was used to calculate the significant parameters. The n (stoichiometric coefficient) values obtained from the statistical physics double-layer model were found to be 0.599, 0.593, and 0.565, which are less than 1, indicating the multi-docking process. The regeneration of Pb-FeONPs was used for up to 5 cycles effectively, making the material highly economical. The Pb-FeONPs were fruitfully applied for the removal of CR dye from wastewater on a laboratory and industrial scale.
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Pluangklang, Chutima, und Kunwadee Rangsriwatananon. „Facile Method by Bentonite Treated with Heat and Acid to Enhance Pesticide Adsorption“. Applied Sciences 11, Nr. 11 (01.06.2021): 5147. http://dx.doi.org/10.3390/app11115147.
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In this work, simple conditions were applied to modify bentonite for the removal of pesticides from aqueous solution. Bentonite was modified in a single step as BA0.5 (with HCl 0.5 M) and BC500 (calcined at 500 °C) and combined steps with different sequences (BA0.5C500 and BC500A0.5). These adsorbents were characterised by XRD, XRF, FT-IR, 27Al MAS NMR, BET, NH3-TPD, TGA, HPLC, particle size analysis and zeta potential. Single-component adsorption with atrazine, diuron, 2,4-D and paraquat was used in aqueous solution at various pesticide concentrations, contact times and pH levels. It was found that the sequence of the treatment significantly affected atrazine adsorption. BC500A0.5 exhibited the highest efficiency for atrazine adsorption in a broad pH range of 3.0–9.0. Its adsorption at pH 6.0 was about 12 times greater than that of other adsorbents with an initial atrazine concentration of 50 mg L−1, which indicates BC500A0.5 specifically for the adsorption of atrazine. In addition, for the simultaneous adsorption of all four pesticides, BC500A0.5 was found to remove the maximum total amount of the pesticides, indicating that it could be used as a good multifunctional adsorbent. All modified bentonites showed similar diuron adsorption better than that of unmodified bentonite. The greatest adsorption of 2,4-D prefers BA0.5C500, occurring at pH 2–4. In the case of paraquat adsorption, all adsorbents are good at absorbing paraquat, but bentonite had the highest rate of paraquat removal, whereas BA0.5C500 was found to have the lowest, and the adsorption increased with increasing pH. Furthermore, the adsorption process on the adsorbents fits well with the Langmuir isotherm and pseudo-second-order kinetics models, as the thermodynamic parameters showed a spontaneous and endothermic process.
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Önal, Emel Simla, Tolga Yatkın, Tural Aslanov, Memduha Ergüt und Ayla Özer. „Biosynthesis and Characterization of Iron Nanoparticles for Effective Adsorption of Cr(VI)“. International Journal of Chemical Engineering 2019 (02.05.2019): 1–13. http://dx.doi.org/10.1155/2019/2716423.
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In this study, iron nanoparticles (FeNPs) were synthesized via a green method using loquat (Eriobotrya japonica) leaves aqueous extract as a renewable reducing agent. The synthesized FeNPs were characterized by DLS, XRD, FT-IR, SEM/EDX, and TEM analysis, and then, they were used as an adsorbent for Cr(VI) removal from aqueous solutions. Batch adsorption experiments were carried out to investigate the optimum adsorption parameters such as the initial pH of the solution, temperature, initial Cr(VI) concentration, and adsorbent concentration. The optimum adsorption conditions were determined as initial pH 3.0, temperature 45°C, and adsorbent concentration 1 g/L. Also, a linear increase was observed in adsorbed Cr(VI) amounts with the increasing initial Cr(VI) concentrations. The biosynthesized FeNPs showed the high removal levels higher than 90% for Cr(VI) adsorption at a wide range of initial Cr(VI) concentrations (50–500 mg/L). The experimental equilibrium data were modelled with Langmuir and Freundlich isotherm models, and it was found that experimental equilibrium data could be well described by the Langmuir isotherm model. The maximum monolayer coverage capacity of FeNPs for Cr(VI) adsorption was found to be 312.5 mg/g. The pseudo-first-order and the pseudo-second-order kinetic models were applied to the experimental adsorption data, and it was concluded that the data were defined as the best agreement with the pseudo-second-order kinetic model. Weber–Morris model was used to investigate the effect of mass transfer on the adsorption of Cr(VI) onto FeNPs; it was observed that both the film (boundary layer) and intraparticle diffusion affected the studied adsorption process. The thermodynamic studies suggested that Cr(VI) adsorption onto FeNPs was endothermic and nonspontaneous, and the positive ΔS value indicated increased disorder at the solid-solution interface during the adsorption.
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Paapla, Neza Rahayu, Normah Normah, Tarmizi Taher, Risfidian Mohadi, Addy Rachmat und Aldes Lesbani. „Effectivity of Indonesian Rice Husk as an Adsorbent for Removing Congo Red from Aqueous Solutions“. Environment and Natural Resources Journal 19, Nr. 4 (17.05.2021): 255–65. http://dx.doi.org/10.32526/ennrj/19/2020232.
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Indonesian rice husk biochar (RH-BC) was prepared by pyrolysis method at 500°C and characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, surface-area-specific analysis by Brunauer-Emmett-Teller, and scanning electron microscopy. The RH-BC were used as adsorbents for enhancing the adsorption of Congo red compared to pristine rice husk (RH) in aqueous solutions. The results of characterization through surface-area-specific analysis showed the surface area of RH-BC (72.25 m2/g) was ten times higher than RH (7.08 m2/g) owing to high-temperature treatment. The results of the adsorption study showed that the RH and RH-BC followed the pseudo-second-order kinetic model and the Freundlich isotherm equation with maximum adsorption capacities of 85.470 mg/g and 72.993 mg/g for the RH-BC and RH, respectively. The thermodynamic parameters of adsorption indicated spontaneous and endothermic processes. The reusability of the adsorbents (RH and RH-BC) showed that they are potentially suitable for extracting Congo red from aqueous solution up to three adsorption-desorption cycles. Their performance sharply decreases after the fourth and fifth cycles.
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Silva, Mariana, Sonia Morante-Zarcero, Damián Pérez-Quintanilla, María Luisa Marina und Isabel Sierra. „Environmental chiral analysis of β-blockers: evaluation of different n-alkyl-modified SBA-15 mesoporous silicas as sorbents in solid-phase extraction“. Environmental Chemistry 15, Nr. 6 (2018): 362. http://dx.doi.org/10.1071/en18030.
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Environmental contextβ-Blockers are important chiral pharmaceuticals found as micropollutants in environmental waters as a result of incomplete removal during wastewater treatment. Because they display enantioselective toxicity, it is necessary to include chiral information in an environmental risk assessment. We have developed an analytical method using mesoporous silica for extracting β-blockers in water samples before their specific chiral analysis. AbstractThe extraction and preconcentration of chiral β-blockers in environmental water was evaluated by solid-phase extraction (SPE) employing an SBA-15 ordered mesoporous silica functionalised with alkyl chains of different length. The materials were characterised by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption–desorption isotherm measurements and elemental analysis. Important parameters influencing extraction efficiency, including the type and amount of sorbent and the breakthrough volume, were optimised. The results obtained showed that the organic chain length played an important role in the behaviour of these sorbents. Under optimised conditions, using 200 mg SBA-15-C8 as sorbent, a simple analytical method based on off-line SPE coupled to chiral capillary electrophoresis with diode array detection (SPE-chiral CE-DAD) was developed. Method detection and quantification limits were lower than 0.6 and 1.9 µg L −1 respectively for all enantiomers, with a preconcentration factor of 500-fold. The method was successfully applied to the chiral analysis of atenolol, metoprolol, pindolol and propranolol in river and sewage water samples. Satisfactory recoveries (between 86 ± 2 and 98 ± 1 %) and repeatability (relative standard deviation (RSD) < 9 %, n = 3) were obtained. Metoprolol was detected in sewage water at a concentration of 10.7 and 9.9 µg L−1 and an enantiomeric fraction of 0.52 and 0.48 for the first- and the second-migrating enantiomers respectively. These results emphasise the importance of enantioselective analysis for environmental risk assessment.
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Cheng, Shan Shan, Chao Hua Zhang, Xi Hong Yang und Wan Cui Xie. „Study on the Adsorption of Mixed Cd(II) and Pb(II) Ions by N,O-Carboxymethyl-Chitosan“. Advanced Materials Research 236-238 (Mai 2011): 2523–28. http://dx.doi.org/10.4028/www.scientific.net/amr.236-238.2523.
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TheN,O-carboxymethyl-chitosan (N,O-CMC) was used to investigate the adsorptions of two metals of Cd(Ⅱ) and Pb(Ⅱ) ions in an mixed aqueous solution. The effects on adsorption capacities such as pH value, temperature, adsorbent dose and initial metal ion concentrations were investigated, and the dialysis method was applied to separate the materials after adsorption. The results revealed that the better adsorption ofN,O-CMC for Cd(Ⅱ) and Pb(Ⅱ) ions at the pH 7-8; the effect of temperature on the adsorption was not significant; the absorption of Cd(Ⅱ) and Pb(Ⅱ) ions was enhanced with the increase ofN,O-CMC amount; the adsorption capacity increasesed with the addition of the concentration of initial metal ions in the aqueous phase. The adsorption of Pb(Ⅱ) ion in Cd-Pb mixed solution on theN,O-CMC was well followed as the Langmuir isotherm equation under the concentration range studied, and Cd(Ⅱ) ion was corresponding to Langmuir adsorption equation in 100-200 mg/L and 200-500 mg/L, respectively. Conclusion:N,O-CMC was suitable for adsorbent to removal Cd(Ⅱ) and Pb(Ⅱ) ions, but it can selectively adsorption ions from the mixed solution, the adsorption capacity (Qm) for two metal ions was as follows: Pb(Ⅱ) > Cd(Ⅱ).
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Eyenubo, O. B., O. Peretomode und S. A. Osakwe. „Biosorption of Cu(II) Ions from Aqueous Solution using Plantain Stalk (Musa Paradisiaca L.)“. Nigerian Journal of Environmental Sciences and Technology 4, Nr. 2 (Oktober 2020): 226–36. http://dx.doi.org/10.36263/nijest.2020.02.0202.
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The study presents the adsorption of Cu (II) ions from aqueous solution by plantain stalk (musa paradisiacal) in relation to its equilibrium and kinetics characteristics, using batch adsorption method. The adsorbent was characterized using FTIR Spectrometry. The following functional groups were observed; hydroxyl, carbonyl, amine and phosphate groups which confirms the potential capability of sorption of the biosorbent. The study shows that there was optimum adsorption at pH 6.0 (75.41%) for Cu (II) ions. There was significant adsorption from the lowest to the highest time (5-180mins) and also there is a significant removal of the metal ions from the lowest to the highest concentration (10 mg/l-500 mg/l). The study also revealed that adsorption of Cu(II) ions by plantain stalk from aqueous solution is best described by Langmuir isotherm due to its R2 values of 0.950. When both order rate equations were tested, data showed a good compliance with the pseudo-second-order rate constant for Cu(II) ions due to its R2 value of 0.999, while the data for pseudo-first-order did not show a good compliance with Cu(II) ions due to its R2 value of 0.549. The results obtained from this study show that plantain stalk is a good adsorbent for the removal of Cu (II) ions from aqueous solution.
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Machalová, Linda, Martin Pipíška, Zuzana Trajteľová und Miroslav Horník. „Comparison Of Cd2+ Biosorption And Bioaccumulation By Bacteria – A Radiometric Study“. Nova Biotechnologica et Chimica 14, Nr. 2 (01.12.2015): 158–75. http://dx.doi.org/10.1515/nbec-2015-0024.
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Abstract In this work, bioaccumulation and biosorption characteristics of Cd2+ ions by both dead and living non-growing biomass of gram-positive bacteria Kocuria palustris and Micrococcus luteus isolated from spent nuclear fuel pools were compared. The radioindicator method with radionuclide 109Cd was used to obtain precise and reliable data characterizing Cd compartmentalization in bacterial cells. The following cellular distribution of Cd in living non-growing biomass after 4 h incubation in solutions containing different concentration of Cd2+ ions (100, 250, 500, 750 and 1000 µmol/L) spiked with 109CdCl2 under aeration at 30 °C were obtained: in M. luteus almost 85 % of Cd was localized on the cell surface and 15 % in cytoplasm. Similarly, in K. palustris 83 % of Cd was localized on the cell surface and 17 % in cytoplasm. The data were obtained by gamma spectrometry of extracts and solids after sequential extraction of biomass with 5 mM Ca(NO3)2 and 20 mM EDTA. Biosorption of Cd by non-living bacterial biomass is a rapid process strongly affected by solution pH and as was confirmed by FTIR analysis beside carboxylate ions also other functional groups such as amino and phosphate contribute to Cd binding by bacterial cell surfaces. Maximum sorption capacities Qmax (μmol/g) calculated from the Langmuir isotherm were 444 ± 15 μmol/g for M. luteus and 381 ± 1 μmol/g for K. palustris.
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Aldalbahi, Ali, Mostafizur Rahaman, Mohammed Almoiqli, Al Yahya Meriey und Govindasami Periyasami. „Efficiency Improvement of a Capacitive Deionization (CDI) System by Modifying 3D SWCNT/RVC Electrodes Using Microwave-Irradiated Graphene Oxide (mwGO) for Effective Desalination“. Journal of Nanomaterials 2020 (07.09.2020): 1–14. http://dx.doi.org/10.1155/2020/5165281.
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This work is aimed at improving the electrosorption capacity of carbon nanotube/reticulated vitreous carbon- (CNT/RVC-) based 3D electrodes and decreasing the duration of electrosorption-desorption cycles by facilitating the ions’ adsorption and desorption on the electrode surface. This was achieved by preparing composites of microwave-irradiated graphene oxide (mwGO) with CNT. All composite materials were coated on RVC by the dip-coating method. The highest loading level was 50 mg. This is because it exhibited the maximum electrosorption capacity when tested in terms of geometric volume. The results showed that the 9-CNT/mwGO/RVC electrode exhibited 100% capacitive deionization (CDI) cyclic stability within its 1st five cycles. Moreover, 27.78% time was saved for one adsorption-desorption cycle using this electrode compared to the CNT/RVC electrode. In addition, the ion removal capacity of NaCl by the 9-CNT/mwGO/RVC electrode with respect to the mass of the electrode (3.82 mg/g) has increased by 18.27% compared to the CNT/RVC electrode (3.23 mg/g) when measured at the optimum conditions. In a complete desalination process, the water production per day for the 9-CNT/mwGO/RVC electrode was increased by 67.78% compared to the CNT/RVC electrode when measured within the same CDI cell using NaCl solution of concentration less than 1 mg/L. When considered volume of 1 m3, this optimum 9-CNT/mwGO/RVC electrode produces water 29,958 L per day. The highest electrosorption capacity, when measured experimentally at 500 mg/L NaCl feed concentration, was 10.84 mg/g for this optimum electrode, whereas Langmuir isotherm gave the theoretically calculated highest value as 16.59 mg/g. The results for the 9-CNT/mwGO/RVC composite electrode demonstrate that it can be an important electrode material for desalination in CDI technology.
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Sulastri, Siti, Nuryono Nuryono, Indriana Kartini und Eko Sri Kunarti. „ADSORPTION OF Ca(II), Pb(II) AND Ag(I) ON SULFONATO-SILICA HYBRID PREPARED FROM RICE HULL ASH“. Indonesian Journal of Chemistry 11, Nr. 3 (20.12.2011): 273–78. http://dx.doi.org/10.22146/ijc.21392.
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In this research, adsorption of Ca(II), Pb(II) and Ag(I) in aqueous solution onto sulfonato-silica hybrid (SSH) prepared from rice hull ash (RHA) has been studied. The preparation of SSH adsorbent was carried out by oxidation of mercapto-silica hybrid (MSH) with hydrogen peroxide (H2O2) solution 33%. MSH was prepared, via sol-gel process, by adding 3 M hydrochloric acid solution to mixture of sodium silicate (Na2SiO3) solution and 3(trimethoxysilyl)-1-propanthiol (MPTS) to reach pH of 7.0. Solution of Na2SiO3 was generated from destruction of RHA with sodium hydroxide solution followed with heating at 500 °C for 30 min. The SSH produced was characterized with Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analyzer, energy dispersive X-ray (EDX) spectroscopy and determination of ion-exchange capacity for sodium ion (Na+). The adsorption of Ag(I) and Ca(II) were conducted in a batch system in various concentrations for one hour. The adsorbent ion was calculated based on difference of concentrations before and after adsorption process determined using atomic absorbance spectrophotometric (AAS) method. The adsorption character was evaluated using model of isotherm Langmuir and Freundlich adsorption to calculate the capacity, constants and energy of adsorption. Result of characterization by EDX and FTIR showed qualitatively that SSH has been successfully synthesized which were indicated by appearance of characteristic absorbance of functional group namely silanol (Si-OH), siloxane (Si-O-Si), methylene (-CH2-) and disappearance of mercapto group (SH). The XRD data showed amorphous structure of SSH, similar to silica gel (SG) and MSH. The study of adsorption thermodynamics showed that oxidation of MSH into SSH increases the ion-exchange capacity for Na+ from 0.123 to 0.575 mmol/g. The change in functional group from silanol to mercapto and from mercapto to sulfonato increases the adsorption capacity of Ca(II). However, the capacity order of adsorbents for both ions of Pb(II) and Ag(I) in aqueous solution is MSH > SG > SSH.
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Xia, Hong Yun, Chang Qun Duan, Wei Zhang und Ke Diao He. „Adsorption Mechanism of Sodium Dodecyl Sulfate on Coagulating Precipitate in Treatment of Vat Dark Blue BO by Coagulation and Air-Flotation“. Advanced Materials Research 1033-1034 (Oktober 2014): 364–68. http://dx.doi.org/10.4028/www.scientific.net/amr.1033-1034.364.
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Vat dark blue BO simulated wastewater was treated by Dissovled air flolation (DAF), the interaction of sodium dodecyl sulfate (SDS) and precipitate in the DAF process was investigated by thermodynamic methods. The adsorption isotherms of SDS on precipitate at pH 5.00 were determined at 30,35,40 and 45°C. The isosteric heat of sorption was calculated by the Clausius-Clapeyron equation. The results show that the isotherm of SDS on coagulation precipitate is not the normal style, the adsorption of SDS on precipitate is exothermic in nature and the isosteric heat of adsorption decreases with a increase in the equilibrium uptake of SDS on precipitate. The isosteric heat of sorption varies between-16.266 and-21.719kJ/mol as surface loading is between 3 and 11 mg/g. The values of isosteric heat of adsorption proves the primary adsorption of SDS on precipitation is physisorption.
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Stanković, Maja N., Nenad S. Krstić, Ian J. Slipper, Jelena Z. Mitrović, Miljana D. Radović, Danijela V. Bojić und Aleksandar Lj Bojić. „Chemically Modified Lagenaria vulgaris as a Biosorbent for the Removal of CuII from Water“. Australian Journal of Chemistry 66, Nr. 2 (2013): 227. http://dx.doi.org/10.1071/ch12422.
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The ability of a biosorbent based on a chemically modified Lagenaria vulgaris shell for CuII ion removal from aqueous solution was studied in batch conditions. The biosorbent was characterized by Fourier-transform infrared spectroscopy and the effect of relevant parameters such as contact time, pH, biomass dosage, and initial metal ion concentration was evaluated. The sorption process was found to be fast, attaining equilibrium within 40 min, and results were found to be best fitted by a pseudo-second order kinetic model. Experimental data showed that the biosorption is highly pH dependent, and the optimal pH was 5.0. Results were analyzed in terms of the following adsorption isotherms: Langmuir, Freundlich, Temkin, and Flory–Huggins, by a linear regression method. The CuII biosorption followed the Langmuir isotherm model (r2 = 0.998) with the maximum sorption capacity of 14.95 mg g–1. The methyl-sulfonated Lagenaria vulgaris biomass investigated in this study exhibited a high potential for the removal of CuII from aqueous solution.
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Lim, Soh Fong, Nur Amalina Naimah Hamidon, Sukinah Abdul Karim, S. N. David Chua und Bee Huah Lim. „Preparation of Sago Bark-Derived Magnetic Adsorbent by Impregnation and Carbonation for Lead and Copper Ions Removal“. Materials Science Forum 1030 (Mai 2021): 159–68. http://dx.doi.org/10.4028/www.scientific.net/msf.1030.159.
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This paper presents an alternative utilisation of sago barks from the sago industry. In this study, a sago bark-derived magnetic adsorbent was developed by impregnation with ferric chloride hexahydrate (FeCl3H2O) and carbonisation method. The potential of the sago bark-derived magnetic adsorbent to remove lead ion (Pb2+) and copper ion (Cu2+) from aqueous solution was assessed in a batch system. Adsorption experiments were performed as a function of initial concentration (5.0 – 15.0 mg/L). The magnetic adsorbent displayed good ferromagnetic property which aids the separation of the adsorbent after the decontamination process. The magnetic adsorbent was characterised by Fourier Transform Infrared (FTIR) Spectroscopy and Scanning Electron Microscopy embedded with an Energy Dispersive X-ray Spectrometer (SEM-EDX). The FT-IR spectra analysis revealed the surface functional groups of the magnetic adsorbent are C−O−C, C−OH, C− H, −C−C−O, Fe-O, O-H, and C-O. The maximum monolayer adsorption capacities were discovered to be 172.414 and 12500 mg/g for lead and copper ions, respectively. The batch adsorption isotherms were analysed using Langmuir, Freundlich, Jovanovic and Temkin isotherm models. The experimental data perfectly fitted with Langmuir isotherm modelling. The results indicated that the sago bark-derived magnetic adsorbent potentially to be an alternative in replacing more high-priced adsorbents for its application in heavy metal ions removal.
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Maigalura, K. A., und J. Suleiman. „MOISTURE SORPTION ISOTHERM CHARACTERISTICS OF AWARA FOOD“. FUDMA JOURNAL OF SCIENCES 4, Nr. 2 (13.07.2020): 620–26. http://dx.doi.org/10.33003/fjs-2020-0402-247.
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Moisture sorption and storage stability of Awara were evaluated using gravimetric method. Guggenhein-Anderson-de boer (GAB) and Brunauer Emmett and Teller (BET) were used in evaluating sorption and desorption isotherm at temperature range of 30, 40 and 50oc in the range of water activity (0.1-0.9).Sigmoid moisture isotherm shapes were obtained at various temperatures. Lowest level EMC was obtained at highest temperature (500c).A non-linear regression analysis was used to fit both BET and GAB. GAB was found to generate higher coefficient of determination R2 (0.9986, 0.9959 and 0.9933) and lowest mean of relative percentage p% (0.231, 0.0061 and 0.0017) at temperature range (30, 40 and 500c) respectively. Safe % water and storage stability were all predicted from adsorption isotherm curve. 3.14, 3.19 and 3.10 were found to be the safe % water which corresponds to the 3.8aw for GAB adsorption graphs at 30, 40 and 500c temperatures respectively. This safe % water will be useful in packaging and determination of shelf- life of Awara.
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Li, Xiaoming, Xinyi Zhang, Yi Li und Xiangdong Xing. „Isothermal oxidation kinetics and oxidation behavior of nickel slag“. Metallurgical Research & Technology 117, Nr. 6 (2020): 603. http://dx.doi.org/10.1051/metal/2020056.
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To improve the reduction effect of nickel slag in preparing Fe–Co–Ni–Cu alloy, an oxidization pretreatment was carried out to changing the structure and phase of silicate and sulfide for the nickel slag before the reducing process. The oxidation behavior and kinetics of nickel slag under different temperature and time conditions were discussed. The results shown that in the oxidation process of nickel slag, the part of Fe2SiO4 was oxidized to Fe3O4 and further to Fe2O3, and the other part of Fe2SiO4 directly oxidized to Fe2O3. Meanwhile, the nickel, cobalt and copper in the form of silicate and sulfide were changed into oxides. The changes of the phases are beneficial to the subsequent reduction of nickel slag. The oxidation degree of nickel slag reached 98% under suitable oxidation conditions (900 °C, 15 min). The oxidation kinetic model of nickel slag obtained by Ln–Ln analysis and Model-fitting method was three-dimensional diffusion at lower temperature (300 °C, 400 °C and 500 °C) and random nucleation at higher temperature (700 °C, 900 °C and 1000 °C) respectively. The activation energies obtained by the model method and the model-free method were 28.58 kJ.mol−1 and 26.28 kJ.mol−1 at lower temperature (300 °C, 400 °C and 500 °C) respectively, and the corresponding value were 81.98 kJ.mol−1 and 78.36 kJ.mol−1 at higher temperature (700 °C, 900 °C and 1000 °C) respectively. The activation energy calculated by the two methods was relatively close, and both can be used to calculate the activation energy.
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Li, Jie, Lei Wang, Bao Wei Li und Bang Wen Zhang. „Kinetics of Reduction Roasting of Hematite to Magnetite in Crude Niobium Concentrate under Microwave Irradiation“. Advanced Materials Research 201-203 (Februar 2011): 1714–20. http://dx.doi.org/10.4028/www.scientific.net/amr.201-203.1714.
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In this paper, the method of microwave reduction roasting was applied to investigate the heating and weight loss process from hematite to magnetite in crude niobium concentrate under the protection of argon. The kinetics of microwave reduction roasting of hematite in crude niobium concentrate were analyzed and calculated at the temperature range of 500°C ~850°C by way of non-isothermal thermogravimetry and isothermal gravimetric analysis. Results from this investigation demonstrated that the activation energy of microwave reduction roasting calculated by non-isothermal thermogravimetry was 26.5769kJ•mol-1, and the activation energy calculated by isothermal gravimetric analysis was 64.1203kJ•mol-1. Compared with the method of reduction roasting under resistance heating, the activation energy of microwave reduction roasting was small, and the reaction rate was fast.
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Asman, Saliza, Sharifah Mohamad und Mohd Kamarulzaki Mustafa. „Sol-gel Approach in Molecular Imprinting for Crystal Violet Selective Recognition“. Sains Malaysiana 50, Nr. 7 (31.07.2021): 1921–33. http://dx.doi.org/10.17576/jsm-2021-5007-08.
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A limitation of conventional MIP in thermal and mechanical stabilities condition, improper porosity and low adsorption capacity, give a reason to introduce a sol-gel method in molecular imprinting process recently. In this study, a synthesis of new sol-gel molecularly imprinted polymer (SG-MIP) was studied for crystal violet (CV) selective recognition. The control non-molecularly imprinted polymer (SG-NIP) was also synthesized as reference. The preparation of SG-MIP was introduced by a combination of the organic and inorganic mixture. The organic solution included the methacrylic acid, trimethylolpropane trimethacrylate, and benzoyl peroxide which are monomer, crosslinker, and initiator, respectively. The inorganic solution involved the ratio of tetraethyl orthosilicate: ethanol (1:1 v/v). The functional group analysis proved the successful synthesized SG-MIP and SG-NIP. The thermal analysis indicated high thermal stability for SG-MIP and SG-NIP, respectively. The morphology and surface analyses showed the respective different structures, surface, and porosity values between SG-MIP and SG-NIP, which influence the selectivity study and adsorption behaviour of SG-MIP toward CV adsorption. The result verified that the SG-MIP (4.900 mgg-1) has higher adsorption and higher selectivity characteristics compared to SG-NIP (4.432 mgg-1). The equilibrium data of kinetic and isotherm studies for SG-MIP and SG-NIP were well-fitted to the pseudo-second order model (R2 = 0.9997 and R2 = 0.9996) and Freundlich isotherm model (R2 = 0.9500 and R2 = 0.9764), respectively. The Freundlich isotherm was supported by the Scatchard plot instead of the Langmuir isotherm model.
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Liang, Z. R., P. C. Philippi, C. P. Fernandes und F. S. Magnani. „Prediction of Permeability from the Skeleton of Three-Dimensional Pore Structure“. SPE Reservoir Evaluation & Engineering 2, Nr. 02 (01.04.1999): 161–68. http://dx.doi.org/10.2118/56006-pa.
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Summary The main purpose of the present work is to predict the permeability of a porous medium from its three-dimensional (3D) porous structure network. In this work, 3D porous structure is reconstructed by the truncated Gaussian method using Fourier transform and starting from a 2D binary image obtained from a thin section of a porous sample. The skeleton of the 3D porous structure provides a way of visualizing the graph of the pore network. It is determined using a thinning algorithm, which is conceived to preserve topology. It gives both visual and quantitative information about the connectivity of the pore space, the coordination number for every node and local hydraulic radius. Once the network of the pore structure is obtained, the macroscopic transport properties, such as the permeability, can be predicted. The method is applied to a 500 mD Berea sandstone and the predicted permeability is in good agreement with the experimental value and empirical correlations. Introduction The prediction of equilibrium and transport properties of porous media is a long-standing problem of great theoretical and practical interest, particularly in petroleum reservoir engineering.1 Past theoretical attempts to derive macroscopic transport coefficients from the microstructure of porous media entailed a simplified representation of the pore space, often as a bundle of capillary tubes.1–3 These models have been widely applied because of their convenience and familiarity to the engineers. But they do have some limitations. For example, they are not well suited for describing the effect of the pore space interconnectivity and long range correlation in the system. Network models have been advanced to describe phenomena at the microscopic level and have been extended in the last few years to describe various phenomena at the macroscopic level. These models are mostly based on a network representation of the porous media in which larger pores (pore bodies) are connected by narrower pores (pore throats). Network models represent the most important and widely used class of geometric models for porous media.2 A network is a graph consisting of a set of nodes or sites connected by a set of links or bonds. The nodes can be chosen deterministically or randomly as in the realization of a Poisson or other stochastic point process. Similarly the links connecting different nodes may be chosen according to some deterministic or random procedure. Finally, the nodes are dressed with convex sets such as spheres representing pore bodies, and the bonds are dressed with tubes providing a connecting path between the pore bodies. The original idea of representing a porous structure by a network is rather old, but it was only in the early 1980s that systematic and rigorous procedures were developed to map, in principle, any disordered rock onto an equivalent random network of bonds and sites. Once this mapping is complete one can study a given phenomenon in porous media in great detail.3 Dullien1 reviewed the details of various pore-scale processes, including detailed descriptions of many aspects of network models. The most important features of pore network geometry and topology that affect fluid distribution and flow in reservoir rocks are the pore throat and pore body size distributions, the pore body-to-pore throat size aspect ratio and the pore body coordination number.4 These data have been tentatively assumed in the previous works. The extension of these techniques to real porous media has been complicated by the difficulty in describing the complex three-dimensional (3D) pore structure of real porous rocks. Information about the pore structure of reservoir rocks is often obtained from mercury intrusion and sorption isotherm. Mercury intrusion and sorption isotherm data provide statistical information about the pore throat size distribution, or, more correctly, the distribution of the volumes that may be invaded within specified pore throat sizes. Advanced techniques such as microcomputed tomography5 and serial sectioning6,7 do provide a detailed description of the 3D pore structures of rocks. Recently, image analysis methods used over pictures of highly polished surfaces of porous materials (e.g., Refs. 8-10), taken with an electron scanning microscope have been used to describe the porous structure. Image analysis techniques such as opening (2D and 3D)11,13 and median line graphs (2D)13 were developed. Information on porous structure is obtained from the analysis of 2D binary images. For isotropic media, a 3D microstructure may be reconstructed from any statistically homogeneous 2D section. The general objective of a reconstructed porous structure is to mimic more closely the geometry of real media. This method has been previously applied to the prediction of important petrophysical and reservoir engineering properties, such as permeability8 and formation factor14 with reasonable success. Thovert et al.15 used the reconstructed porous structure and developed thinning algorithms to obtain the graph of the 3D pore structure. Some topological characteristics such as the number of loops were derived. Bakke and O/ren16 generated 3D pore networks based on numerical modeling of the main sandstone forming geological processes. Absolute and relative permeability were computed for a Bentheimer sandstone. However, although their algorithms worked well on their models, the problem of connectivity preservation for a 3D thinning algorithm appears to be only correctly taken into account by Ma,17 who proposed sufficient conditions for providing a 3D thinning algorithm to preserve connectivity.
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Rahman, Mustafizur, M. A. Alim, Suman Saha und M. K. Chowdhury. „Mixed Convection in a Vented Square Cavity with a Heat Conducting Horizontal Solid Circular Cylinder“. Journal of Naval Architecture and Marine Engineering 5, Nr. 2 (15.06.2009): 37–46. http://dx.doi.org/10.3329/jname.v5i2.2504.
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A finite element method based computational study of steady laminar mixed convection flow inside a vented square cavity with a heat conducting horizontal solid circular cylinder placed at the center of the cavity is carried out in this paper. The developed mathematical model is governed by the coupled equations of continuity, momentum and energy. The present work simulates practical systems such as cooling of electronic devices, ventilation of building etc. The effects of cylinder size and Richardson number on fluid flow and heat transfer performance are investigated. Richardson number is varied from 0.0 to 5.0 and the cylinder diameter is varied from 0.0 to 0.6. The results for the case of without cylinder are compared to those with cylinder to observe the effects cylinder on the flow and heat transfer inside the cavity. The phenomenon inside the cavity for the case of with and without cylinder is analyzed through streamline and isotherm patterns. It is found that the streamlines, isotherms, average Nusselt number at the heated surface, average temperature of the fluid in the cavity and dimensionless temperature at the cylinder center strongly depend on the Richardson number as well as the diameter of the cylinder.Keywords: Mixed convection, finite element method, Richardson number, cylinder diameter, vented cavity and diffusion.DOI: 10.3329/jname.v5i2.2504Journal of Naval Architecture and Marine Engineering 5(2)(2008) 37-46
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Vuppala, Aditya, Alexander Krämer, Johannes Lohmar und Gerhard Hirt. „FepiM: A Novel Inverse Piecewise Method to Determine Isothermal Flow Curves for Hot Working“. Metals 11, Nr. 4 (07.04.2021): 602. http://dx.doi.org/10.3390/met11040602.
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In forming simulations, flow curves are cardinal inputs to predict features, such as forming forces and material flow. The laboratory-scale experiments to determine them, like compression or tensile tests, are affected by deformation heating, restricting direct flow curve determination. In principle, the current analytical and inverse methods determine flow curves from these tests, but while the analytical methods assume a simplified temperature profile, the inverse methods require a closed-form flow curve equation, which mostly cannot capture complex material behavior like multiple recrystallization cycles. Therefore, the inverse piecewise flow curve determination method “FepiM” previously developed and published by the current authors is extended by introducing a two-step procedure to obtain isothermal flow curves at elevated temperatures and different strain rates. Thereby, the flow curve is represented as tabular data instead of an equation to reproduce complex flow curve shapes while also compensating the effect of inhomogeneous temperature profiles on the flow stress. First, a flow curve at the highest temperature is determined. In the second step, using this first flow curve as a reference, the flow curves at lower temperatures are obtained via interpolation. Flow curves from conventional compression tests for aluminum and copper in the temperature range of 20–500 °C are predicted, and it is shown that these flow curves can reproduce the experimental forces with a maximum deviation of less than 1%. Therefore, the proposed new piecewise method accurately predicts isothermal flow curves for compression tests, and the method could be further extended to highly inhomogeneous methods in the future.
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Abdul Rahman, Nurashina, Anita Ramli und Chong Fai Kait. „Preliminary Study on Effect of Hydrothermal Temperature during TiO2 Synthesis on the Biodiesel Production from Waste Cooking Oil“. Sains Malaysiana 50, Nr. 6 (30.06.2021): 1685–95. http://dx.doi.org/10.17576/jsm-2021-5006-15.
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In the present work, effect of hydrothermal temperature from 120 to 160 °C on TiO2 physicochemical properties as well as its photocatalytic activity towards biodiesel production using waste cooking oil (WCO) was investigated. TiO2was synthesized via hydrothermal method using Titanium butoxide, Ti(OBu)4 as the precursor and nitric acid, HNO3 as the peptizing agent. Next, the synthesized photocatalyst was dried at 60 °C for 24 h and later calcined at 400 °Cfor 2 h. The synthesized TiO2 was characterized using X-ray diffraction (XRD) and Burnauer- Emmet- Teller (BET) to determine their crystallinity and textural properties. Results showed that all synthesized TiO2 have a mixture of anatase and rutile phase and N2 adsorption- desorption isotherm for all catalyst possess Type IV isotherm according to IUPACclassification with hysteresis loop of type H1. Then, all the synthesized catalysts were tested for biodiesel production using esterified waste cooking oil under visible light irradiation for 1 h and 10 min. Percentage of fatty acid methyl ester (FAMEs) present in the synthesized biodiesel was determined using gas chromatography with flame ionization detector (GC-FID). The synthesized catalyst (T24_160) showed a good photocatalytic activity as the percentage of biodiesel yield was higher (3.41%) compared to the other catalyst.
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Zhao, Hai Jing, Dong Lin Zhao, Ji Ming Zhang und Dong Dong Zhang. „Ordered Mesoporous Carbon Nano Spheres as Electrode Material for Supercapacitors“. Applied Mechanics and Materials 320 (Mai 2013): 661–64. http://dx.doi.org/10.4028/www.scientific.net/amm.320.661.
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Ordered mesoporous carbon nanospheres with uniformly penetrating channels have been successfully synthesized by a nanocasting method using mesoporous silica as a template. The ordered mesoporous carbon nanospheres were investigated as electrode materials for supercapacitors via high-resolution transmission electron microscopy, nitrogen adsorption and desorption isotherms and a variety of electrochemical testing techniques. The electrodes with ordered mesoporous carbon nanospheres prepared by coating method exhibited good rate capability and reversibility at high scan rates in electrochemical performances. Ordered mesoporous carbon nanosphere electrode with specific surface area of 904 m2/g maintained a stable specific capacitance of 210 F g-1under specific current of 0.1 A g-1for 500 cycles of charge/discharge.
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Wen, Shaw-Bing, Nan-Chung Wu, Sheng Yang und Moo-Chin Wang. „Effect of TiO2 addition on the crystallization of Li2O–Al2O3–4SiO2 precursor powders by a sol-gel process“. Journal of Materials Research 14, Nr. 9 (September 1999): 3559–66. http://dx.doi.org/10.1557/jmr.1999.0482.
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The activation energy for crystallization of β-spodumene in TiO2 added Li2O–Al2O3–4SiO2 (LAS) precursor powders by a sol-gel process was studied by using isothermal and nonisothermal methods. Nonisothermal kinetics for the LAS precursor powder system were investigated using differential thermal analysis (DTA) and quantitative x-ray diffraction (XRD) analysis. The rate of crystallization of LAS precursor powders decreased as the TiO2 content increased. For samples with addition of 0, 5.0, and 10.0 wt% TiO2, the activation energies for crystallization by DTA evaluation were 165.06, 194.46, and 205.38 kJ/mol, respectively. According to the quantitative XRD method, the values computed by the Johnson–Mehl–Avrami equation were 162.54, 189.42, and 196.14 kJ/mol, respectively. The values obtained by isothermal and nonisothermal kinetic methods from DTA and XRD analyses were in good agreement. The growth morphology parameters were 0.59, 0.70, and 0.76, respectively, for the LAS precursor powder with TiO2 addition of 0, 5.0, and 10.0 wt%, showing a rodlike growth. In the LAS precursor powder system, TiO2 did not act as the nucleative agent.
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Martínez-de-Guereñu, Ane, M. Oyarzabal, F. Arizti und Isabel Gutiérrez. „Application of Coercive Field Measurements to the Evaluation of Recovery and Recrystallization in Cold Rolled Interstitial Free (IF) Steel“. Materials Science Forum 500-501 (November 2005): 647–54. http://dx.doi.org/10.4028/www.scientific.net/msf.500-501.647.
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The recovery and recrystallization kinetics of a cold rolled interstitial free (IF) steel were studied during isothermal annealing. Magnetic methods based on coercive field measurements, hardness tests and metallography were applied so as to follow the kinetics experimentally. The coercive field measurement technique reveals a higher degree of resolution for monitoring recovery than conventional hardness determination and also allows the recrystallization progress to be monitored. The results obtained are compared to those previously determined for a non-stabilized extra low carbon (ELC) steel. The observed differences are discussed in terms of the presence of microalloying elements, Ti and Nb, which slow down recovery and delay recrystallization.
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Shewen, E. C., K. G. T. Hollands und G. D. Raithby. „The Measurement of Surface Heat Flux Using the Peltier Effect“. Journal of Heat Transfer 111, Nr. 3 (01.08.1989): 798–803. http://dx.doi.org/10.1115/1.3250754.
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Calorimetric methods for measuring surface heat flux use Joulean heating to keep the surface isothermal. This limits them to measuring the heat flux of surfaces that are hotter than their surroundings. Presented in this paper is a method whereby reversible Peltier effect heat transfer is used to maintain this isothermality, making it suitable for surfaces that are either hotter or colder than the surroundings. The paper outlines the theory for the method and describes physical models that have been constructed, calibrated, and tested. The tested physical models were found capable of measuring heat fluxes with an absolute accuracy of 1 percent over a wide range of temperature (5–50°C) and heat flux (15–500 W/m2), while maintaining isothermality to within 0.03 K. A drawback of the method is that it appears to be suited only for measuring the heat flux from thick metallic plates.
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Arockiasamy, P., X. Queen Rosary Sheela, G. Thenmozhi, M. Franco, J. Wilson Sahayaraj und R. Jaya Santhi. „Evaluation of Corrosion Inhibition of Mild Steel in 1 M Hydrochloric Acid Solution byMollugo cerviana“. International Journal of Corrosion 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/679192.
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The inhibiting effect of methanolic extract ofMollugo cervianaplant on the corrosion of mild steel in 1 M HCl solution has been investigated by different techniques like potentiodynamic polarization, electrochemical impedance spectroscopy, and weight loss methods for five different concentrations of plant extract ranging from 25 to 1000 mg/L. The results indicated that the corrosion inhibition efficiency increased on increasing plant extract concentration till 500 mg/L and decreased on further increasing concentration. The extract was a mixed type inhibitor with the optimum inhibition concentration of 500 mg/L in potentiodynamic polarization. The adsorption of the plant extract on the mild steel surface was found to obey Langmuir adsorption isotherm. Surface analysis was also carried out to find out the surface morphology of the mild steel in the presence and in the absence of the inhibitor to find out its efficiency. The obtained results showed that theMollugo cervianaextract acts as a good inhibitor for the corrosion of mild steel in 1 M HCl solution.
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Kupich, Iwona, und Magdalena Madeła. „Determining the possibility of using selected composts to remove aqueous solutions from zinc ions in concentrations of up to 1000 mg.L-1“. E3S Web of Conferences 86 (2019): 00025. http://dx.doi.org/10.1051/e3sconf/20198600025.
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The high sorption capacity of compost indicates that it can be a cheap alternative to the currently used sorbents, also in the case of heavy metals. The sorption of zinc from aqueous solutions with the use of the selected compost types not meeting standards was carried out in accordance with the batch method in the constant contact conditions of a liquid (100 mL) and a solid (5,0 g) when the concentrations of Zn2+ were 100, 250, 500, 750 and 1000 mg·L-1. The efficiency of the process decreased with an increasing Zn2+ concentration and was strongly dependent on the quality of the compost and the composition of the initial compost mixture. For the highest concentration of zinc, the best efficiency (nearly 70%) was obtained in case of the commercial compost, while the lowest one (only 25%) in the case of the compost made only from green waste and prepared in a garden compost bin. The experimental results were described using the Freundlich isotherms and the obtained equation parameters show the adsorption process. It was found that compost can serve as an efficient sorbent with regard to zinc ions.
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Su, Tie Jun, und Ke Hua Li. „Adsorption and Inhibitive Properties of 1-phenylaminomethyl-benzimidazole on Corrosion of Mild Steel in Hydrochloric Acid“. Advanced Materials Research 989-994 (Juli 2014): 536–39. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.536.
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The corrosion inhibition of mild steel in 5.0 M HCl by 1–phenylaminomethyl-benzimidazo -le (PMB) was studied by gravimetric and potentiodynamic polarization methods. Inhibition efficiency of PMB increased with increase in the concentration of inhibitor and decreased with the increase in temperature. PMB acts as anodic-type inhibitor for mild steel. The adsorption of PMB on mild steel surface obeys the Langmuir adsorption isotherm.
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Matallo, M. B., D. A. S. Franco, S. D. B. Almeida und A. L. Cerdeira. „Sorption and desorption of Suflafenacil in two soils in the state of São Paulo with different physical and chemical attributes“. Planta Daninha 32, Nr. 2 (Juni 2014): 393–99. http://dx.doi.org/10.1590/s0100-83582014000200017.
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A study was conducted to evaluate the sorption and desorption of 14C herbicide saflufenacil (pyrimidinedione) in two soils in the State of São Paulo, classified as Red Yellow Latosol with clayey texture (LVA-1) and medium texture (LVA-2), using the batch method through isotherms. The soils were air dried and sieved a 2 mm mesh. The radioactivity was determined by liquid scintillation spectrometry in acclimatized room (25 ± 2 °C). Sorption isotherms were conducted for 5 concentrations of saflufenacil (5.0; 2.5; 1.0; 0.5 and 0.05 μg mL-1) and the results were adjusted to the Freundlich equation, thus obtaining the parameters of sorption followed by two extractions with 0.01 M CaCl2 to determine desorption parameters similarly to sorption. The results showed that saflufenacil sorption was low for both soils studied, being greater for the LVA with higher organic matter content. The desorption coefficients were greater than their sorption coefficients, suggesting the occurrence of hysteresis. The sorption and desorption isotherms (classified as type C isotherms), hysteresis and the t-test between the angular coefficient of the respective isotherms showed that both the sorption and desorption occur with equal intensity.
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Esmaeili, A., P. Beirami und S. Ghasemi. „Evaluation of the Marine AlgaeGracilariaand its Activated Carbon for the Adsorption of Ni(II) from Wastewater“. E-Journal of Chemistry 8, Nr. 4 (2011): 1512–21. http://dx.doi.org/10.1155/2011/137484.
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The batch removal of Ni2+from aqueous solution and wastewater using marine dried (MD) red algaeGracilariaand its activated carbon (AC) was studied. For these experiments, adsorption of Ni2+was used to form two biomasses of AC and MD. Both methods used different pH values, biomass and initial concentration of Ni2+. Subsequently adsorption models and kinetic studies were carried out. The maximum efficiencies of Ni2+removal were 83.55% and 99.04% for MD and AC respectively developed from it. The experimental adsorption data were fitted to the Langmuir adsorption model. The nickel(II) uptake by the biosorbents was best described by pseudo-second order rate model. The kinetic studies showed that the heavy metal uptake was observed more rapidly by the AC with compared to MD. AC method developed from MD biomass exhibited higher biosorption capacity. Adsorption capacity is related to the pH of solution, pH 5.0 is optimal for nickel. The maximum efficiencies of Ni2+removal were for AC method. The capacity is related to the pH of solution, pH 5.0 is optimal for nickel. The equilibrium adsorption data are correlated by Langmuir isotherm equation. The adsorption kinetic data can be described by the second order kinetic models
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Sarwar, Amna, Jin Wang, Muhammad Saqib Khan, Umar Farooq, Nadia Riaz, Abdul Nazir, Qaisar Mahmood et al. „Iron Oxide (Fe3O4)-Supported SiO2 Magnetic Nanocomposites for Efficient Adsorption of Fluoride from Drinking Water: Synthesis, Characterization, and Adsorption Isotherm Analysis“. Water 13, Nr. 11 (27.05.2021): 1514. http://dx.doi.org/10.3390/w13111514.
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This research work reports the magnetic adsorption of fluoride from drinking water through silica-coated Fe3O4 nanoparticles. Chemical precipitation and wet impregnation methods were employed to synthesize the magnetic nanomaterials. Moreover, the synthesized nanomaterials were characterized for physicochemical properties through scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray powder diffraction. Screening studies were conducted to select the best iron oxide loading (0.0–1.5 wt%) and calcination temperature (300–500 °C). The best selected nanomaterial (0.5Fe-Si-500) showed a homogenous FeO distribution with a 23.79 nm crystallite size. Moreover, the optimized reaction parameters were: 10 min of contact time, 0.03 g L−1 adsorbent dose, and 10 mg L−1 fluoride (F−) concentration. Adsorption data were fitted to the Langmuir and Freundlich isotherm models. The Qm and KF (the maximum adsorption capacities) values were 5.5991 mg g−1 and 1.869 L g−1 respectively. Furthermore, accelerated adsorption with shorter contact times and high adsorption capacity at working pH was among the outcomes of this research work.
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Li, Liang Yu, Dong Lin Zhao und Dong Dong Zhang. „Electrochemical Performance of Graphene Nanosheets as Electrode Material for Supercapacitors“. Advanced Materials Research 873 (Dezember 2013): 581–86. http://dx.doi.org/10.4028/www.scientific.net/amr.873.581.
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Graphene nanosheets (GNSs) were prepared from flake natural graphite by oxidation, rapid expansion and ultrasonic treatment. The morphology, structure and electrochemical performance of GNSs as electrode materials for supercapacitors were systematically investigated via high-resolution transmission electron microscopy, X-ray diffraction, nitrogen adsorption and desorption isotherms and a variety of electrochemical testing techniques. The electrodes with freestanding GNSs prepared by coating method exhibited good rate capability and reversibility at high scan rates in electrochemical performances. GNS electrode with specific surface area of 243 m2 g1 maintained a stable specific capacitance of 200 F g1 under specific current of 0.1 A g1 for 500 cycles of charge/discharge.