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1
Qin, Wei, Beibei Xu, and Shenqiang Ren. "An organic approach for nanostructured multiferroics." Nanoscale 7, no. 20 (2015): 9122–32. http://dx.doi.org/10.1039/c5nr01435b.
Повний текст джерела
2
Sando, D., A. Agbelele, C. Daumont, D. Rahmedov, W. Ren, I. C. Infante, S. Lisenkov, et al. "Control of ferroelectricity and magnetism in multi-ferroic BiFeO 3 by epitaxial strain." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, no. 2009 (February 28, 2014): 20120438. http://dx.doi.org/10.1098/rsta.2012.0438.
Повний текст джерелаАнотація:
Recently, strain engineering has been shown to be a powerful and flexible means of tailoring the properties of ABO 3 perovskite thin films. The effect of epitaxial strain on the structure of the perovskite unit cell can induce a host of interesting effects, these arising from either polar cation shifts or rotation of the oxygen octahedra, or both. In the multi-ferroic perovskite bismuth ferrite (BiFeO 3 –BFO), both degrees of freedom exist, and thus a complex behaviour may be expected as one plays with epitaxial strain. In this paper, we review our results on the role of strain on the ferroic transition temperatures and ferroic order parameters. We find that, while the Néel temperature is almost unchanged by strain, the ferroelectric Curie temperature strongly decreases as strain increases in both the tensile and compressive ranges. Also unexpected is the very weak influence of strain on the ferroelectric polarization value. Using effective Hamiltonian calculations, we show that these peculiar behaviours arise from the competition between antiferrodistortive and polar instabilities. Finally, we present results on the magnetic order: while the cycloidal spin modulation present in the bulk survives in weakly strained films, it is destroyed at large strain and replaced by pseudo-collinear antiferromagnetic ordering. We discuss the origin of this effect and give perspectives for devices based on strain-engineered BiFeO 3 .
3
Aroor Rao, Badari Narayana, Shintaro Yasui, Tsukasa Katayama, and Mitsuru Itoh. "Fabrication and Characterization of Multiferroic Al0.5Fe1.5O3 Epitaxial Thin Films." MRS Advances 4, no. 09 (2019): 539–44. http://dx.doi.org/10.1557/adv.2019.121.
Повний текст джерелаАнотація:
ABSTRACTSingle-phase multiferroic materials have attracted considerable attention among scientists, due to the strong drive in industry towards device miniaturization, addition of new functionalities, etc. Currently, most of the discovered materials have at-least one ferroic order active only at low temperatures, thereby hindering their induction into practical devices. κ-Al2O3-type AlxFe2-xO3 (x-AFO) oxides belong to a new class of metastable multiferroic compounds (space group: Pna21), with relatively high Curie temperatures. The current work investigates the effect of thin film deposition conditions on the ferroelectric and ferrimagnetic properties of Al0.5Fe1.5O3 (0.5-AFO). Substrate temperature and oxygen partial pressure during deposition were found to be the critical parameters in obtaining high quality films. Optimizing the deposition conditions of 0.5-AFO enabled observation of both ferroelectricity and ferrimagnetism at room temperature.
4
Hutanu, Vladimir, Andrew Sazonov, Georg Roth, In-Hwan Oh, Max Baum, Jonas Stein, Markus Braden, et al. "Spherical neutron polarimetry in multiferroics under external stimuli." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C151. http://dx.doi.org/10.1107/s2053273314098489.
Повний текст джерелаАнотація:
Study of multiferroics, materials simultaneously having more than one primary ferroic order parameter, is a hot topic of material sciences. The most extensively studied class of these compounds is the family of magnetoelectric multiferroics, where ferroelectricity can be induced by various types of magnetic orderings via the relativistic spin-orbit interaction. As a consequence of the cross coupling between spins and electric polarization, the spectacular control of the ferroelectric polarization by external magnetic field and the manipulation of the magnetic order via electric field can often be realized in these systems. Depending on the symmetry and microscopic mechanism of the multiferroicity the coupling energy between magnetic and electric ordering parameters can significantly vary. Classical neutron diffraction often fails in the precise determining of the complex magnetic structure in the multiferroics due to the presence of the statistically distributed domains in the macroscopic sample. Using spherical neutron polarimetry (SNP), known also as 3D polarization analysis, it is possible not only to precisely determine the complex magnetic structure, but also to investigate in-situ its evolution with external parameters and to control the magnetic domains distribution under the influence of the external electric or/and magnetic field. Here we will present some SNP results on few different multiferroic materials. In some of them, e.g. square lattice 2D antiferromagnet Ba2CoGe2O7, even strong electric field does not change the magnetic order. However rater week magnetic field is sufficient to create a mono-domain structure and to rotate spins in the plane. In other e.g. incommensurate (spiral) magnetic structure of the TbMnO3, solely electric field is sufficient to fully control the chirality of the magnetic structure. In the case of Cr2O3 both electric and magnetic fields should be applied in parallel in order to switch between the different antiferromagnetic domains.
5
Vysochanskii, Yu, and O. Derzhko. "About this special issue ``Ferroelectricity and Multiferroics''." Condensed Matter Physics 25, no. 4 (2022): 40101. http://dx.doi.org/10.5488/cmp.25.40101.
Повний текст джерелаАнотація:
The special issue of the CMP journal Ferroelectricity and Multiferroics contains the papers of theoretical and experimental investigations in a wide range covering physical effects, properties and applications of ferroics–crystalline oxide, chalcogenide and hydrogen bonded materials with a long- range order parameter–spontaneous polarization, magnetization or strain. The order parameter arises due to the phase transition taking place with the temperature decrease, and at pressure or chemical composition variation. The phase transitions on the temperature–pressure–composition diagrams are investigated using different methods (first principles and model calculations, molecular dynamics simulations, mean-field analysis of thermodynamic properties) with the aim to search for the materials (monocrystals, ceramics and nanoparticles) having effective functional parameters, especially for multiferroics that have more than one of the interacting long-range orders. The fundamental physical research of nonlinear processes in ferroics on the nanoscale, with controlling the size effects, provides a background for developing nanostructures favourably applied in nanoelectronics and information technologies.
6
Venegas-García, Deysi J., and Lee D. Wilson. "Kinetics and Thermodynamics of Adsorption for Aromatic Hydrocarbon Model Systems via a Coagulation Process with a Ferric Sulfate–Lime Softening System." Materials 16, no. 2 (January 10, 2023): 655. http://dx.doi.org/10.3390/ma16020655.
Повний текст джерелаАнотація:
The adsorption mechanisms for model hydrocarbons, 4-nitrophenol (PNP), and naphthalene were studied in a coagulation-based process using a ferric sulfate–lime softening system. Kinetic and thermodynamic adsorption parameters for this system were obtained under variable ionic strength and temperature. An in situ method was used to investigate kinetic adsorption profiles for PNP and naphthalene, where a pseudo-first order kinetic model adequately described the process. Thermodynamic parameters for the coagulation of PNP and naphthalene reveal an endothermic and spontaneous process. River water was compared against lab water samples at optimized conditions, where the results reveal that ions in the river water decrease the removal efficiency (RE; %) for PNP (RE = 28 to 20.3%) and naphthalene (RE = 89.0 to 80.2%). An aluminum sulfate (alum) coagulant was compared against the ferric system. The removal of PNP with alum decreased from RE = 20.5% in lab water and to RE = 16.8% in river water. Naphthalene removal decreased from RE = 89.0% with ferric sulfate to RE = 83.2% with alum in lab water and from RE = 80.2% for the ferric system to RE = 75.1% for alum in river water. Optical microscopy and dynamic light scattering of isolated flocs corroborated the role of ions in river water, according to variable RE and floc size distribution.
7
Yao, Minghai, Long Cheng, Shenglan Hao, Samir Salmanov, Mojca Otonicar, Frédéric Mazaleyrat, and Brahim Dkhil. "Great multiferroic properties in BiFeO3/BaTiO3 system with composite-like structure." Applied Physics Letters 122, no. 15 (April 10, 2023): 152904. http://dx.doi.org/10.1063/5.0139017.
Повний текст джерелаАнотація:
Multiferroic materials have attracted significant research attention due to their technological potential for applications as multifunctional devices. The scarcity of single-phase multiferroics and their low inherent coupling between multiferroic order parameters above room temperature pose a challenge to their further applications. We propose a 3BiFeO3/7BaTiO3 perovskite–perovskite composite that combines ferroelectricity and ferromagnetism. We demonstrate that the sintering temperature can tailor the ferroelectricity and ferromagnetism of the composites. The multiferroicity can be achieved at a low sintering temperature in the composite-like structure ceramics, and its multiferroic properties, especially the ferromagnetism, are superior to those of solid solutions. We also investigate the dynamic evolution of multiferroicity with sintering temperature. We adopt a nano–micro strategy to construct a composite-like microstructure, which results in optimized ferroelectric (1.62 μC cm−2) and ferromagnetic (0.16 emu/g) characteristics at a sintering temperature of 750 °C. We also found experimental evidence of the competition between antiferromagnetic and ferromagnetic interactions in the transition metal cation sublattice. Multiferroic BiFeO3/BaTiO3 composites with combined ferroelectric and ferromagnetic properties have significant potential for various applications.
8
Arrieta, Alberto Albis, Ever Ortiz Muñoz, Ismael Piñeres Ariza, Juan Osorio Cardozo, and Jennifer Monsalvo Morales. "Catalytic effect of ferric sulfate and zinc sulfate on lignin pyrolysis." Applied Chemical Engineering 5, no. 1 (April 26, 2022): 59. http://dx.doi.org/10.24294/ace.v5i1.1449.
Повний текст джерелаАнотація:
The effect of zinc sulfate and ferric sulfate on the pyrolysis process of lignin was studied at three different heating rates by using the thermogravimetric analysis technique. It was found that the pyrolysis of pure lignin is barely affected with the change of heating rates between 10 to 100 °C/min, which is unexpected because of the kinetic nature of pyrolysis. The pyrolysis kinetics of this major component of biomass was studied by using three fitting methods: the differential method with reaction order model n, the isoconversional method, and the distribution of activation energies model, DAEM. The best fit, which allowed calculating acceptable kinetic parameters, was obtained using the last method. The results show the influence of the catalysts and the heating rate on the lignin pyrolysis processes in the presence of the sulfates under study, which is confirmed by obtaining different kinetic parameters. The results suggest that zinc sulfate and ferric sulfate change the kinetic mechanism of lignin pyrolysis.
9
Nagano, Tetsushi, Hiroshi Isobe, Satoru Nakashima, and Midori Ashizaki. "Characterization of Iron Hydroxides in a Weathered Rock Surface by Visible Microspectroscopy." Applied Spectroscopy 56, no. 5 (May 2002): 651–57. http://dx.doi.org/10.1366/0003702021955222.
Повний текст джерелаАнотація:
In order to nondestructively characterize chemical forms of ferric hydroxides in weathered rock, charge-coupled device type visible microspectroscopy was applied to brown stains produced in weathered granite surfaces. The combination of visible microspectra and color parameters ( a* and b*) was effective in examining chemical forms of ferric hydroxides in the analytical area. Color parameters in an a*– b* diagram of the brown stains, mostly lying between goethite and ferrihydrite trends, indicated that the brown stains contain ferrihydrite or hematite in addition to goethite. Similarity of the visible microspectra of the brown stains and their first derivatives to those of goethite or ferrihydrite suggests that goethite and/or ferrihydrite are the main weathering products of the granite. Occurrence of ferrihydrite as well as goethite in the brown stains implies that crystallization of ferrihydrite to goethite might be hindered during the granite weathering. This fact suggests the possibility of toxic metal retention in ferrihydrite by its long-term persistence during water–rock interactions at the earth's surface.
10
Kim, Su-Chan, and Hyun M. Jang. "Pb()O3-type Perovskites: Part II. Short-range Order Parameter as a Criterion of the Distinction Between Relaxor and Normal Ferroelectrics." Journal of Materials Research 12, no. 8 (August 1997): 2127–33. http://dx.doi.org/10.1557/jmr.1997.0285.
Повний текст джерелаАнотація:
A classification scheme of Pb()O3-type perovskites with respect to the B-site order parameters was proposed based on the theoretical calculation of the short-range order parameter (σ) using the pair-correlation model. The calculated order parameters predict that a Pb()O3-type perovskite without any charge difference between B′ and B″ cations [e.g., Pb(Zr1/2Ti1/2)O3 (PZT)] is represented by a completely disordered state with the absence of a finite coherence length. On the other hand, a Pb()O3-type perovskite system having different ionic charges is characterized either by the short-range ordering with a nanoscale coherence length or by the macroscopic long-range ordering, depending on the magnitude of ionic charge difference between B′ and B″ ions. The normal ferroelectricity in Pb()O3-type complex perovskites was then correlated either with a completely disordered state (σ = 0) or with a perfectly ordered state (σ = 0), whereas the relaxor behavior was attributed to the nanoscale short-range ordering (0 < σ < 1) in the configuration of the B-site cations.
11
Zhu, Weixiao, Jianduo Wang, Yili Wang, and Hongjie Wang. "Study on sulfadimethoxine removal from aqueous solutions by hydrous ferric oxides." Water Science and Technology 74, no. 5 (June 21, 2016): 1136–42. http://dx.doi.org/10.2166/wst.2016.246.
Повний текст джерелаАнотація:
Significant concerns have been raised over the presence of antibiotics including sulfadimethoxine (SDMO) in aquatic environments. This study investigated the removal capability and mechanism involved in the removal of SDMO by hydrous ferric oxides (HFO). Results showed that SDMO removal was highly pH and ionic strength dependent. The pseudo-first-order model fitted well the kinetic results, and the value of the calculated activation energy for SDMO adsorption onto HFO was 8.6 kJ mol−1. Adsorption isotherms at varied temperatures were well described by the Langmuir model. Thermodynamic parameters (change in enthalpy > 0, change in entropy > 0, and change in Gibbs free energy < 0) calculated from the temperature-dependent sorption data revealed spontaneous and endothermic process. The exchange of the surface hydroxyl groups of HFO and the negative anions of SDMO− and the electrostatic interaction between the positively charged surface of HFO and the deprotonated imino (–N−–) accounted for the uptake of SDMO by HFO.
12
Jafari, Shila, Benjamin Wilson, Minna Hakalahti, Tekla Tammelin, Eero Kontturi, Mari Lundström, and Mika Sillanpää. "Recovery of Gold from Chloride Solution by TEMPO-Oxidized Cellulose Nanofiber Adsorbent." Sustainability 11, no. 5 (March 6, 2019): 1406. http://dx.doi.org/10.3390/su11051406.
Повний текст джерелаАнотація:
The goal of this study was to assess the sustainability of a modified cellulose nanofiber material for the recovery of precious gold from chloride solution, with a special focus on gold recovery from acidic solutions generated by cupric and ferric chloride leaching processes. TEMPO-oxidized cellulose nanofiber in hydrogel (TOCN), dry (H-TOCN, F-TOCN) and sheet form (S-TOCN) was examined for gold adsorptivity from chloride solution. Additionally, this work describes the optimum conditions and parameters for gold recovery. The data obtained in this investigation are also modeled using kinetic (pseudo first-order and pseudo second-order), isotherm best fit (Freundlich, Langmuir and Langmuir-Freundlich), and thermodynamic (endothermic process) parameters. Results demonstrate that high levels of gold removal can be achieved with TEMPO-oxidized cellulose nanofibers (98% by H-TOCNF) and the interaction characteristics of H-TOCN with gold suggests that other precious metals could also be efficiently recovered.
13
Hou, R. Z., and X. M. Chen. "Synthesis and Dielectric Properties of Layer-structured Compounds An−3Bi4TinO3n+3 (A = Ba, Sr, Ca) with n > 4." Journal of Materials Research 20, no. 9 (September 2005): 2354–59. http://dx.doi.org/10.1557/jmr.2005.0287.
Повний текст джерелаАнотація:
Several bismuth layer-structured compounds An−3Bi4TinO3n+3 (A = Ba, Sr, Ca) with n > 4 were synthesized and investigated. The average radius of A-site cations was found to be closely related to the lattice parameters in the a–b plane and, therefore, closely related to the stability of the layer structure. For Ba2Bi4Ti5O18 ceramics, there was a diffused phase transition centered at approximately 330 °C, which should be due to the cation redistribution of A-site Ba2+ and Bi3+ in the (Bi2O2)2+ layer. For Sr2Bi4Ti5O18 ceramics, a sharp dielectric constant peak was found at 325 °C. Ceramics of five-layered Ca2Bi4Ti5O18 and six-layered Ca3Bi4Ti6O21 showed temperature-stable dielectric constants up to 800 °C, and ferroelectricity was observed. In addition, as ferroelectrics, these Ca-containing bismuth layer-structured compounds showed frequency-independent dielectric constants >150 and small tan δ on the order of 10−3–10−4 in the frequency range of 1 kHz to 1 MHz.
14
Drathen, Christina, Kirill Yusenko, and Serena Margadonna. "Structural modulations in multiferroic tetragonal tungsten bronze KxMnxFe1+xF3." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C52. http://dx.doi.org/10.1107/s2053273314099471.
Повний текст джерелаАнотація:
Multiferroic materials showing coupling of the different order parameters (ferroelectric, ferromagnetic, ferroelastic) are interesting not only from a fundamental perspective, but also from a technological point of view, e.g. for to the development of new storage technologies. However, the coexistence of (ferro)magnetism and ferroelectricity is considered a rare phenomenon. Whilst this may be true for perovskite oxides, where emptyd-shells favor the off-centering of ions but counteract magnetism, this intrinsic limitation can be avoided by moving to different structure types, and/or away from oxides. An example of non-perovskite, non-oxide multiferroic systems are the tetragonal tungsten bronze (TTB) fluorides KxM2+xM3+1+xF3(x= 0.4 – 0.6), which show coexistence of electric and magnetic ordering 1. Here we present a detailed structural study on a series of TTB fluorides, KxMnxFe1+xF3(x = 0.4 – 0.55). KMnFeF6has been previously described as tetragonalP42bcand orders ferrimagnetically belowT = 148 K 2. Additional satellite reflections were found in transmission electron microscopy experiments and attributed to ferroelastic domains arising from tilting ofMF6octahedra, but the reported bulk powder XRD measurements indicated only tetragonal symmetry 3. We used high-resolution powder diffraction techniques to reinvestigate the crystal structure as a function of temperature in comparison with DSC data. Our results reveal a structural distortion to orthorhombic symmetry (Ccc2) at room temperature, which diminished when moving to the end members of the series (x → 0.4 andx → 0.6). Although structurally subtle, this distortion may indicate a ferroelectric state, similar to KxFeF3, where ferroelectricity is observed only in the orthorhombic phase. On heating, an anomaly in thec-axis lattice parameter accompanies a phase transition to centrosymmetricP42/mbcaround 320 – 350 K, marking the transition from ferroelectric – paraelectric state.
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Bhattarai, Pushpa, Khagendra Prasad Bohra, and Megh Raj Pokhrel. "Adsorptive Removal of As(III) from Aqueous Solution." Journal of Institute of Science and Technology 19, no. 1 (November 8, 2015): 150–54. http://dx.doi.org/10.3126/jist.v19i1.13841.
Повний текст джерелаАнотація:
The iron-modified Dalbergia sissoo sawdust was synthesized by loading iron (III) onto phosphorylated Dalbergia sissoo sawdust via soaking in a ferric salt solution. Batch studies were performed at an initial concentration of 1 mg/l to evaluate the effect of parameters such as pH, equilibrium time, adsorbent dose and concentration of adsorbate. Kinetics and isotherm modeling studies demonstrated that the experimental data best fit a pseudo-first order and Langmuir isotherm model, respectively. The maximum adsorption capacity was found to be 1.33 mg/g for As(III) onto FePDSD suggesting the suitability of chemically modified Dalbergia sissoo sawdust for the adsorptive removal of As(III) from aqueous solution.Journal of Institute of Science and Technology, 2014, 19(1): 150-154
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Morin, Mickael, Denis Scheptyakov, Lukas Keller, Juan Rodríguez-Carvajal, Andrea Scaramucci, Nicola Spaldin, Michel Kenzelmann, Ekaterina Pomjakushina, Kazimierz Conder, and Marisa Medarde. "Electric polarization from spiral order below 200K in multiferroic YBaCuFeO5." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C388. http://dx.doi.org/10.1107/s2053273314096119.
Повний текст джерелаАнотація:
Ferroelectric materials have been known for almost one century [1]. While their potential for applications was rapidly recognized, the possibility of combining ferroelectricity with magnetic order -preferably with ferromagnetism- has resulted in an enormous deal of interest during the last decade. Several new materials combining both types of order have been recently reported, although their promising multifunctionalities have been obscured by two facts: on one side, most of them are antiferromagnetic; on the other, their transition temperatures, typically below 40K, are too low for most practical applications. The oxygen-defficient double perovskite YBaFeCuO5 constitutes a remarkable exception. Spontaneous electric polarization has been recently reported to exist below an unusually high temperature of TC ≍ 200K [2] coinciding with the occurrence of a commensurate - to - incommensurate reorientation of the Fe3+ and Cu2+ magnetic moments [3,4]. From a more fundamental point of view the observation of incommensurable magnetic order in a tetragonal material at such high temperatures is rather surprising. In particular, the nature of the relevant competing magnetic interactions and its possible link to low dimensionality or geometrical frustration is not understood at present. Although the existence of the spin reorientation in this material is known since 1995 [3] the low temperature magnetic structure has not yet been solved. Using neutron powder diffraction we have recently been able to propose a spiral model which satisfactorily describes the measured magnetic intensities below TC. Further, investigation of the crystal structure showed the existence of small anomalies in the lattice parameters and some interatomic distances at TC. The relevance of these findings for the magnetoelectric coupling, the direction of the polarization, the modification of the different exchange paths in the structure and the stabilization of the incommensurate magnetic order below TC is discussed.
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Harrat, Zouaoui R., Mohammed Chatbi, Baghdad Krour, Marijana Hadzima-Nyarko, Dorin Radu, Sofiane Amziane, and Mohamed Bachir Bouiadjra. "Modeling the Thermoelastic Bending of Ferric Oxide (Fe2O3) Nanoparticles-Enhanced RC Slabs." Materials 16, no. 8 (April 12, 2023): 3043. http://dx.doi.org/10.3390/ma16083043.
Повний текст джерелаАнотація:
Nanoparticles, by virtue of their amorphous nature and high specific surface area, exhibit ideal pozzolanic activity which leads to the formation of additional C-S-H gel by reacting with calcium hydroxide, resulting in a denser matrix. The proportions of ferric oxide (Fe2O3), silicon dioxide (SiO2), and aluminum oxide (Al2O3) in the clay, which interact chemically with the calcium oxide (CaO) during the clinkering reactions, influence the final properties of the cement and, therefore, of the concrete. Through the phases of this article, a refined trigonometric shear deformation theory (RTSDT), taking into account transverse shear deformation effects, is presented for the thermoelastic bending analysis of concrete slabs reinforced with ferric oxide (Fe2O3) nanoparticles. Thermoelastic properties are generated using Eshelby’s model in order to determine the equivalent Young’s modulus and thermal expansion of the nano-reinforced concrete slab. For an extended use of this study, the concrete plate is subjected to various mechanical and thermal loads. The governing equations of equilibrium are obtained using the principle of virtual work and solved using Navier’s technique for simply supported plates. Numerical results are presented considering the effect of different variations such as volume percent of Fe2O3 nanoparticles, mechanical loads, thermal loads, and geometrical parameters on the thermoelastic bending of the plate. According to the results, the transverse displacement of concrete slabs subjected to mechanical loading and containing 30% nano-Fe2O3 was almost 45% lower than that of a slab without reinforcement, while the transverse displacement under thermal loadings increased by 10%.
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Ahmed, S., and S. K. Saha. "Electrochemical study of the reaction between progressively alkylated thiazine leucodyes and Fe(III) on a glassy carbon electrode." Canadian Journal of Chemistry 74, no. 10 (October 1, 1996): 1896–902. http://dx.doi.org/10.1139/v96-213.
Повний текст джерелаАнотація:
An electrochemical investigation on five progressively alkylated thiazine dyes in the presence of Fe(III) ions is reported. The theory of the catalytic regeneration mechanism involving an electrode reaction followed by a coupled chemical reaction is applied to derive kinetic parameters of homogeneous reaction. The second-order rate constant for the reaction of thiazine leucodyes with Fe(III) ions was found to increase from 0.25 × 104 to 1.6 × 104 dm3 mol−1 s−1 upon monomethylation and to vary from 0.7 × 104 for the dimethyl derivative to 1.4 × 104 dm3mol−1 s−1 for the tetramethyl one. The electron-donating nature as well as the hydrophobic characteristics of the methyl group influence the kinetics of the homogeneous reaction. Key words: cyclic voltammetry, thiazine dyes, ferric ion, catalytic regeneration, kinetics
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Jiang, Zhen Zhen, Yang Chen, and Jun Ren Zhu. "Optimization of the Coagulation Process for Kaolin and Humic Acid Removal Using Polymeric Aluminum Ferric Sulfate." Advanced Materials Research 1088 (February 2015): 353–57. http://dx.doi.org/10.4028/www.scientific.net/amr.1088.353.
Повний текст джерелаАнотація:
In the paper, the optimization of the coagulation process for Kaolin and humic acid removal using polymeric aluminum ferric sulfate (PAFS) was studied. In order to obtain the maximum turbidity and humic acid removal efficiency of Kaolin and humic acid simulated wastewater, the optimum coagulation conditions was investigated with the factors of mixing speed and time. Furthermore, mixing speed and time including parameters affecting the coagulation performance such as rapid mixing speed, rapid mixing time, slow mixing speed and slow mixing time using single factor and orthogonal array L9 (34) analysis were examined. The results showed that the optimum single factor of mixing speed and time indicated rapid mixing speed of 350 rpm, rapid mixing time of 1.0 min, slow mixing speed of 60 rpm and slow mixing time of 20 min. Then the orthogonal optimization experiment of mixing speed and time indicated maximum HA removal efficiency was 97.5% at rapid mixing speed of 350 rpm, rapid mixing time of 1.25 min, slow mixing speed of 60 rpm, and slow mixing time of 20 min.
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Malki, Fatiha, Ali Alouache, and Soumia Krimat. "Effects of Various Parameters on the Antioxidant Activities of the Synthesized Heterocyclic Pyrimidinium Betaines." Indonesian Journal of Chemistry 23, no. 1 (December 27, 2022): 90. http://dx.doi.org/10.22146/ijc.74803.
Повний текст джерелаАнотація:
Betaine derivatives are widely used in cosmetic, industrial uses, biology and other scientific fields. Pyrimidinium betaine is a special class of bioactive heterocyclics. They have interesting antioxidant and free radical scavenging activities. This work aims to examine the influence of some parameters on the antioxidant activity of some synthesized betaines containing pyrimidine ring. Four pyrimidinium betaines: monocyclic, bicyclics, and one with a fatty alkyl chain were synthesized from condensation of 2-aminopyrimidine or amidine derivatives with malonic esters, and their antioxidant capacity was evaluated. The effects of concentration, reaction time and temperature on their antioxidant activities were investigated by three common methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, ferric reducing antioxidant power (FRAP) and β-carotene bleaching. The results showed that all pyrimidinium betaines exhibited antioxidant activities in different assays. In the DPPH and reducing power assays, antioxidant activity increased with concentration, whereas in the β-carotene/linoleic acid system, it increased with temperature. On the other hand, the DPPH assay showed an increase in antioxidant capacity over time, while the β-carotene bleaching assay showed a decrease. These results indicate that the antioxidant activity differs depending on the method used and that the various factors affect the antioxidant activity in a different order.
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Murtic, Senad, Rodoljub Oljaca, Ivana Koleska, Lutvija Karic, and Vida Todorovic. "Response of cherry tomato seedlings to liquid fertiliser application under water stress." Horticultural Science 45, No. 1 (February 21, 2018): 22–28. http://dx.doi.org/10.17221/17/2017-hortsci.
Повний текст джерелаАнотація:
The aim of this study was to examine the impact of different liquid fertilisers on selected physiological parameters in order to evaluate the drought tolerance of cherry tomato seedlings. The following physiological parameters were investigated: total phenolic and flavonoid content, total antioxidant capacity and proline content of leaf extracts. Total phenolic and flavonoid content were determined using the Folin-Ciocalteu and aluminium chloride colorimetric methods, respectively. The ferric-reducing/antioxidant power (FRAP assay) was used to measure the total antioxidant capacity, while proline content was evaluated according to the method of Bates. The contents of proline, total phenolics and flavonoids were significantly higher in the leaves of cherry tomato seedlings exposed to water stress, which suggests that the higher synthesis of these substances by plants represents an important defence mechanism of drought tolerance. The results also indicate that the application of all the used fertilisers in accordance with the manufacturer’s instructions can significantly increase the content of phenol compounds and total antioxidant capacity of plants under normal growth conditions, thus improving survival under subsequent stress.
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Revankar, Harish N., Prasanna S. Koujalagi, Vijayendra R. Gurjar, and Raviraj M. Kulkarni. "Adsorption of Chromium(VI) from Aqueous Solution using Iron Oxide Loaded Strong Base Anion Exchange Resin." Asian Journal of Chemistry 35, no. 2 (2023): 397–405. http://dx.doi.org/10.14233/ajchem.2023.26935.
Повний текст джерелаАнотація:
A hybrid adsorbent (FO-Tulsion) was prepared by altering Tulsion A-62(MP), a commercial strongly basic anion-exchanging resin, with hydrated ferric oxide (HFO) particles of average crystallite size 49.6 nm and the removal of Cr6+ from water on Tulsion A-62(MP) and HFO-Tulsion was observed under optimized parameters. This study examines the effectiveness of chromium(VI) removal from water utilizing Tulsion A-62(MP) and Fe-loaded Tulsion A-62(MP) as selective sorbent materials. As the resin and HFO-ion-exchange Tulsion’s mechanism was rather easy and after 210 min of Cr6+ solution interaction, the optimum equilibrium was reached. Almost all the chromium ions was removed by the sorption process when the pH was between 4.0 and 5.0. The Freundlich and Langmuir adsorption isotherms were used to compare the equilibrium data for Cr6+ adsorption and it was found that both are highly suitable for Cr6+ adsorption. Under the same conditions, evaluation of the adsorption attainment of the prepared HFO-Tulsion and the anion resin indicated that the HFO-Tulsion had an elevated adsorption capability with a value of 207.18 mg/g than the anion resin (181.55 mg/g). The resulting hybrid resin was studied using spectroscopic and solid-state methods. Adsorption is governed by first-order reversible kinetics. It is possible that modifying anion resin with hydrated ferric oxide can greatly pick up the adsorption performance in the elimination of Cr6+ from drinking water and polluted water.
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Aguirre, Paulina, Esvar Diaz, and Juan C. Gentina. "Evaluation of Parameters in the Bio-Oxidation Process of Refractory Gold Minerals." Advanced Materials Research 825 (October 2013): 364–67. http://dx.doi.org/10.4028/www.scientific.net/amr.825.364.
Повний текст джерелаАнотація:
The mining districts located in the western mountain range in the south of Ecuador have gold minerals with refractory characteristics, which do not allow gold recovery by traditional methods used in Ecuador. Therefore, it is necessary to apply some technology that permits to obtain greater metal recovery. Bio-oxidation, as treatment of refractory ores that contain low grade of gold, offers an economic and sustainable alternative for this purpose. The objective of this research was to evaluate the effect of particle size, pulp density and concentration of inoculum and inducer (Fe+2) on the bio-oxidation of refractory gold minerals in order to maximize gold recovery of the bioleached minerals by means of a cyanidation process. The microbial consortium used in this work was collected and isolated from the Portovelo mining district corresponding mostly toAcidithiobacillus ferrooxidansandLeptospirillum ferrooxidansspecies. The Eh, final concentration of ferric ion, total iron and sulfates were measured. Finally, the bio-oxidized material was tested using cyanidation to determine the gold recovery. The results after the cyanidation tests showed that the highest gold recovery was obtained when the bio-oxidation step was conducted with 68-91 µm particle size, 15% pulp density, 20% v/v inoculum and 2 g/L of Fe2+as inducer. At those conditions, gold recovery was 68% compared to 26% obtained when no bio-oxidation step was performed, demonstrating that this process was favorable compared with traditional gold recovery processes
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Carbajal-De la Torre, G., N. N. Zurita-Mendez, M. A. Espinosa-Medina, A. B. Martinez-Valencia, and A. Sanchez-Castillo. "Synthesis of Synthetic Hematite with Substituted Aluminum by Sol-Gel Method." Materials Science Forum 793 (May 2014): 119–25. http://dx.doi.org/10.4028/www.scientific.net/msf.793.119.
Повний текст джерелаАнотація:
In this work, synthetic hematite with isomorphically substituted aluminum contents were obtained by the sol-gel chemical synthesis. Nanomaterials with Fe and Al contains were obtained by the sol-gel method mixing stoichiometric mixtures of ferric chloride (FeCl3) and aluminum isopropoxide Al (OC3H7)3at 75°C. The obtained sol-gel was dried at 60 oC followed by calcinations at 400, 800 and 1100 oC. The resulting powders were characterized by X-Ray diffraction and Scanning Electron Microscopy (SEM). Preliminary results showed α-Fe2O3particles into amorphous Al-O-Fe structure, and the formation of alumina with sintering temperature. SEM characterization results, showed small size particle formation in the order of 100-200 nm, however nanosize particles could be improve by chemical parameters control and ultrasonic dispersion. Also SEM observation showed the formation and homogenous distribution of minority Fe-O phase particles between Al-O-Fe phase particles.
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da Silva, Estelina Lora, Adeleh Mokhles Gerami, P. Neenu Lekshmi, Michel L. Marcondes, Lucy V. C. Assali, Helena M. Petrilli, Joao Guilherme Correia, Armandina M. L. Lopes, and João P. Araújo. "Group Theory Analysis to Study Phase Transitions of Quasi-2D Sr3Hf2O7." Nanomaterials 11, no. 4 (March 31, 2021): 897. http://dx.doi.org/10.3390/nano11040897.
Повний текст джерелаАнотація:
We present an ab-initio study performed in the framework of density functional theory, group-subgroup symmetry analysis and lattice dynamics, to probe the octahedral distortions, which occur during the structural phase transitions of the quasi-2D layered perovskite Sr3Hf2O7 compound. Such a system is characterized by a high-temperature I4/mmm centrosymmetric structure and a ground-state Cmc21 ferroelectric phase. We have probed potential candidate polymorphs that may form the I4/mmm → Cmc21 transition pathways, namely Fmm2, Ccce, Cmca and Cmcm. We found that the band gap widths increase as the symmetry decreases, with the ground-state structure presenting the largest gap width (∼5.95 eV). By probing the Partial Density of States, we observe a direct relation regarding the tilts and rotations of the oxygen perovskite cages as the transition occurs; these show large variations mostly of the O p-states which contribute mostly to the valence band maximum. Moreover, by analyzing the hyperfine parameters, namely the Electric Field Gradients and asymmetric parameters, we observe variations as the transition occurs, from which it is possible to identify the most plausible intermediate phases. We have also computed the macroscopic polarization and confirm that the Cmc21 phase is ferroelectric with a value of spontaneous polarization of 0.0478 C/m2. The ferroelectricity of the ground-state Cmc21 system arises due to a second order parameter related to the coupling of the rotation and tilts of the O perovskite cages together with the Sr displacements.
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Rodríguez Madrera, Roberto, Ana Campa Negrillo, Belén Suárez Valles, and Juan José Ferreira Fernández. "Phenolic Content and Antioxidant Activity in Seeds of Common Bean (Phaseolus vulgaris L.)." Foods 10, no. 4 (April 15, 2021): 864. http://dx.doi.org/10.3390/foods10040864.
Повний текст джерелаАнотація:
Dry bean (Phaseolus vulgaris L.) is one of the most important pulses consumed in the world. Total phenolic content, total flavonoid content, total monomeric anthocyanin content and antioxidant capacity were determined, using ferric reducing antioxidant power and free radical scavenging activity, in 255 lines grown under the same environmental conditions. For all parameters analysed, there was a wide range of variability, with differences always above one order of magnitude. Phenolic compounds in beans with coloured coats were found to be more efficient antioxidants than those with completely white coats, and samples with more strongly coloured coats (red, cream, black, pink and brown) showed the highest antioxidant capacities. Based on the strong correlation detected between the variables, total phenolic content can be considered an appropriate indicator of antioxidant activity. The results provide a robust database for selecting those lines of greater functional and nutritional interest in terms of cultivation for direct consumption, for inclusions in food formulations or for use in future breeding programs.
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Dhanasekaran, P., P. M. Satya Sai, C. Anandbabu, and K. K. Rajan. "Defluoridation of water by chemical impregnated Artocarpus hirsutus sawdust." Water Supply 16, no. 5 (April 13, 2016): 1297–312. http://dx.doi.org/10.2166/ws.2016.032.
Повний текст джерелаАнотація:
Sawdust of Artocarpus hirsutus impregnated with ferric hydroxide and activated alumina (SFAA) has been studied for defluoridation of water. This paper presents a detailed surface characterization of the adsorbent by studying pore size distribution and surface morphology. By combining the constituents in the right proportion, an adsorbent with a well-developed pore size distribution could be synthesized. The effects of various parameters on fluoride adsorption by SFAA are investigated. The adsorption capacity of SFAA is considerably higher than that of many adsorbents including activated alumina. More importantly, the adsorption capacity remains unchanged for the pH range of 1 to 9, which also makes it attractive for wastewater treatment. Besides a higher efficiency supported by the results of column studies, this adsorbent is economic as the sawdust constitutes 40% by weight of the total adsorbent. Kinetic studies indicate that fluoride adsorption on SFAA follows pseudo second-order model. Breakthrough adsorption capacity of SFAA is 1.21 mg/g, as compared with 0.41 mg/g for activated alumina.
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Hoffmeister, D., M. Herbrecht, T. Kramm, and P. Schulte. "EVALUATION OF RANDOM FOREST–BASED ANALYSIS FOR THE GYPSUM DISTRIBUTION IN THE ATACAMA DESERT." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-3/W2-2020 (October 29, 2020): 25–28. http://dx.doi.org/10.5194/isprs-annals-iv-3-w2-2020-25-2020.
Повний текст джерелаАнотація:
Abstract. Gypsum-rich material covers the hillslopes above ∼ 1000 m of the Atacama and forms the particular landscape. In this contribution, we evaluate random forest-based analysis in order to predict the gypsum distribution in a specific area of ∼ 3000 km2, located in the hyperarid core of the Atacama. Therefore, three different sets of input variables were chosen. These variables reflect the different factors forming soil properties, according to digital soil mapping. The variables are derived from indices based on imagery of the ASTER and Landsat-8 satellite, geomorphometric parameters based on the Tandem-X World DEM™, as well as selected climate variables and geologic units. These three different models were used to evaluate the Ca-content derived from soil surface samples, reflecting gypsum content. All three different models derived high values of explained variation (r2 > 0.886), the RMSE is ∼ 4500 mg∙kg−1 and the NRMSE is ∼ 6%. Overall, this approach shows promising results in order to derive a gypsum content prediction for the whole Atacama. However, further investigation on the independent variables need to be conducted. In this case, the ferric oxides index (representing magnetite content), slope and a temperature gradient are the most important factors for predicting gypsum content.
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Xu, Rui, Xiaolong Nan, Feiyu Meng, Qian Li, Xuling Chen, Yongbin Yang, Bin Xu, and Tao Jiang. "Analysis and Prediction of the Thiourea Gold Leaching Process Using Grey Relational Analysis and Artificial Neural Networks." Minerals 10, no. 9 (September 15, 2020): 811. http://dx.doi.org/10.3390/min10090811.
Повний текст джерелаАнотація:
The thiourea (TU) leaching of gold from refractory ores can be considered an alternative to cyanidation. However, the high reagent consumption causes an increase in cost, which seriously limits its use. In order to effectively reduce the TU consumption, it is necessary to analyze the influencing parameters of gold recovery and TU consumption and apply them to the prediction of the TU leaching process. This paper investigated six potential influencing parameters and used grey relational analysis (GRA) to analyze the relational degree between each parameter and gold recovery and TU consumption. Then, the artificial neural network (ANN) model was established to simultaneously predict the gold recovery and TU consumption in the TU gold leaching process. The results of the GRA indicated that the leaching time, initial pH, temperature, TU dosage, stirring speed, and ferric iron concentration were all well related to the gold recovery and TU consumption. Therefore, the incorporation of these parameters can significantly improve the ANN model validation. The predictive results noted that the prediction accuracy of gold recovery varied from 94.46% to 98.06%, and the TU consumption varied from 95.15% to 99.20%. Thus, the predicted values corresponded closely to the experimental results, which suggested that the ANN model can accurately reflect the relationship between the operational conditions and the gold recovery and TU consumption. This prediction method can be used as an auxiliary decision-making tool in the TU gold leaching process, and it has broad engineering application prospects in engineering.
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Čutović, Natalija, Petar Batinić, Tatjana Marković, Dragoja Radanović, Aleksandar Marinković, Branko Bugarski, and Aleksandra Jovanović. "Physicochemical properties of winter savory extracts prepared using ultrasound-assisted extraction." Lekovite sirovine, no. 42 (2022): 34–42. http://dx.doi.org/10.5937/leksir2242034c.
Повний текст джерелаАнотація:
This study aimed to assess the optimal extraction parameters, solvent-to-solid ratio, and extraction time, for ultrasound-assisted extraction of Satureja montana L. (winter savory) harvested from a 6-year-old experimental plantation. The optimization was performed in order to acquire extracts that are rich in the content of polyphenols (TPC), flavonoids (TFC), and proteins, and also exhibit strong antioxidant activity, while maintaining satisfactory physical characteristics. Besides this, the influence of UV irradiation on the physicochemical properties of the selected extracts was also analyzed. The TPC values increased with longer extraction time and higher ratio (ranging from 41.4 to 56.9 mg gallic acid equivalent (GAE)/g for the ratio 30:1, and 52.4-58.4 mg GAE/g for 40:1), and the TFC followed the same trend. Total protein content values increased with the increase in the solvent-to-solid ratio, while the extraction time had no significant influence. All used antioxidant assays showed better activities when a higher solvent-to-solid ratio has been performed. pH values ranged from 6.00 to 6.46. The extraction time and solvent-to-solid ratio did not significantly influence the conductivity, whereas the zeta potential was significantly affected. The highest density was detected in the extract acquired at a 40:1 ratio after 30 min (0.994 g/mL), and higher viscosity of the extracts attained at a 30:1 ratio compared to the parallels at a 40:1 ratio. According to the results of UV stability, UV light significantly affected the TPC, TFC, total proteins, ABTS radical scavenging, cupric, and ferric ion-reducing activities, with a positive effect on ferric ion-reducing potential, and the denisty. In conclusion, the extraction conditions that yielded the best phenolic-rich extract with good antioxidant potential and satisfactory physical properties were a 40:1 solvent-to-solid ratio and a 30 minute extraction time.
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Starowicz, Małgorzata, Anita Ostaszyk, and Henryk Zieliński. "The Relationship between the Browning Index, Total Phenolics, Color, and Antioxidant Activity of Polish-Originated Honey Samples." Foods 10, no. 5 (April 28, 2021): 967. http://dx.doi.org/10.3390/foods10050967.
Повний текст джерелаАнотація:
Honey is a source of sugars, amino acids/proteins, and polyphenols, which are the main substrates and reactants in the Maillard reaction. Several bioactive molecules are formed and sequestered to the brown polymeric melanoidins, resulting in a gain and loss of antioxidant function in honey. Therefore, the relationships between the browning index and total phenolic contents, color, and antioxidant activity of Polish-originated honeys, namely acacia, buckwheat, heather, linden, multiflorous, and rapeseed, obtained from three local beekeepers, were addressed in this study. The Total Phenolic Content data showed the following order: buckwheat > heather > acacia > multiflorous > linden > rapeseed. The buckwheat honey also had the highest ability to scavenge free radicals in the range of 207.1–289.3 and 40.9–52.3 µmol Trolox g−1, provided by Antioxidant Compounds Water-soluble and Ferric Reducing Antioxidant Power assays, respectively. Furthermore, a higher degree of browning was observed in dark-colored honey, such as buckwheat (3.1) and heather (1.35 mAU), than in light ones. Moreover, L* and b* parameters had a greater value in the honey of multiflorous, linden, and rapeseed, and a* was higher in buckwheat and heather. The variables of browning and TPC, ACW, and FRAP were positively correlated with each other. It can be concluded that the browning index strongly contributed to parameters of honey appearance, bioactive compound content, and antioxidant activity.
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Lee, Kang Hyun, Ye Won Jang, Hansol Kim, Jang-Seu Ki, and Hah Young Yoo. "Optimization of Lutein Recovery from Tetraselmis suecica by Response Surface Methodology." Biomolecules 11, no. 2 (January 28, 2021): 182. http://dx.doi.org/10.3390/biom11020182.
Повний текст джерелаАнотація:
Microalgae have been attracting attention as feedstock for biorefinery because they have various advantages, such as carbon fixation, high growth rate and high energy yield. The bioactive compounds and lutein contained in microalgae are known to be beneficial for human health, especially eye and brain health. In this study, in order to improve the recovery of bioactive extracts including lutein from Tetraselmis suecica with higher efficiency, an effective solvent was selected, and the extraction parameters such as temperature, time and solid loading were optimized by response surface methodology. The most effective solvent for lutein recovery was identified as 100% methanol, and the optimum condition was determined (42.4 °C, 4.0 h and 125 g/L biomass loading) by calculation of the multiple regression model. The maximum content of recovered lutein was found to be 2.79 mg/mL, and the ABTS radical scavenging activity (IC50) and ferric reducing antioxidant power (FRAP) value were about 3.36 mg/mL and 561.9 μmol/L, respectively. Finally, the maximum lutein recovery from T. suecica through statistical optimization was estimated to be 22.3 mg/g biomass, which was 3.1-fold improved compared to the control group.
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Plastina, Pierluigi, Rosa Tundis, Chiara La Torre, Vincenzo Sicari, Angelo Maria Giuffré, Alessandro Neri, Marco Bonesi, et al. "The addition of Capsicum baccatum to Calabrian monovarietal extra virgin olive oils leads to flavoured olive oils with enhanced oxidative stability." Italian Journal of Food Science 33, no. 1 (February 6, 2021): 61–72. http://dx.doi.org/10.15586/ijfs.v33i1.1937.
Повний текст джерелаАнотація:
This study aimed to evaluate the influence of Capsicum baccatum L. Aji Angelo and Bishop crown cultivars to the quality parameters of flavoured olive oils (FOOs) obtained by the addition of both fresh and dried pepper powders (1%) to Dolce di Rossano and Roggianella monovarietal extra virgin olive oils (EVOOs). First, pepper extracts were investigated for their total phenolic, flavonoid, carotenoid content as well as phenolic acids, fatty acid profile, and vitamin C and E content. In order to evaluate the impact of both fresh and dried peppers on the oxidative stability of FOOs, the Rancimat test was applied. 2,2-Azinobis(3-ethylbenzothiazoline-6-sulfonic) acid (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), ?-carotene bleaching (B-CB) and ferric reducing antioxidant power (FRAP) assays were used to investigate the antioxidant potential. Bishop crown dried extracts showed the highest phenolic, carotenoid and vitamin content, whereas Aji Angelo had the highest amount of capsaicinoids. Among EVOOs, Roggianella EVOO showed the highest antioxidant activity as well as the highest induction time (39.6 h). Remarkably, FOO obtained by the addition of Bishop crown dried pepper extract to Roggianella EVOO showed a higher induction time (44.9 h) with respect to the corresponding EVOO.
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Krezhov, Kiril. "Effects of Substitution in Barium Hexaferrites BaFe12-xXxO19 (X=Co,Ti; Sc)." Solid State Phenomena 159 (January 2010): 175–80. http://dx.doi.org/10.4028/www.scientific.net/ssp.159.175.
Повний текст джерелаАнотація:
The short and long-range atomic and magnetic order in BaFe12-xCoxTixO19 (x=0.4, 0.7, 0.8) and BaFe10.4Sc1.6O19 prepared by soft chemistry routes were studied and compared with parent BaFe12O19 prepared by solid-state reaction. For BaFe10.3Co0.85Ti0.85O19 neutron diffraction and magnetic measurements revealed that (Co2+, Ti4+) substitution causes significant distortions in the local oxygen surrounding of ferric cation sites, while the grain-size effect on the structural parameters is considerably smaller. The thermal expansion coefficient exhibits a strong anisotropy. The refined magnetic moments for x=0.45 and 0.7 based on the five-cation sublattice block-type collinear ferrimagnetic structure of uniaxial type known as Gorter type for BaFe12O19, are considerably lower than the theoretical spin only moments, especially for the 4e and 12k sites, indicating for x = 0.7 a local noncollinearity with short-range ordering. For x = 0.85, at 10 K a block-type conical magnetic structure sets in. For BaFe10.4Sc1.6O19, combined neutron diffraction, field-dependent 57Fe Mössbauer studies and magnetic measurements show that the collinear block-type structure remains effective at 300 K and below it down to about 190 K. In the 190 – 1.6 K range we observe a temperature dependent incommensurate complex block-type conical structure.
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Kolodziej, Barbara, Sugier Danuta, and Luchowska Katarzyna. "Changes of antioxidant activity and active compounds content in selected teas." Foods and Raw Materials 8, no. 1 (February 26, 2020): 91–97. http://dx.doi.org/10.21603/2308-4057-2020-1-91-97.
Повний текст джерелаАнотація:
Our study tested 45 tea infusions classified into five groups (white, green, red, black, and other teas) for the content of total polyphenols and flavonoids, as well as antioxidant properties, by the FRAP and DPPH methods. We examined these parameters after prolongation of the brewing time from 10 to 30 min and overnight storage. The results showed that the capacity of the teas to bind free radicals was differentiated and the amount of anti-oxidant compounds depended on their nature. In terms of antioxidant activity and total polyphenol content, the tested tea types were ranked in the following order: white > green > black > red > other teas (yerba mate > rooibos). Our experiment demonstrated a positive correlation between the polyphenol content and antioxidant activity of the analyzed teas. Also, the DPPH antiradical efficiency was comparable to their ability to reduce ferric ions. The extended brewing time had a significant effect on the antioxidant activity of the infusions and the polyphenolic compounds analyzed therein. In contrast, storage of the infusions for 24 h at room temperature changed their antioxidant activity and affected the total polyphenol content.
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Manzur-Valdespino, Salvador, Esther Ramírez-Moreno, José Arias-Rico, Osmar Antonio Jaramillo-Morales, Zuli Guadalupe Calderón-Ramos, Luis Delgado-Olivares, Manuel Córdoba-Díaz, Damián Córdoba-Díaz, and Nelly del Socorro Cruz-Cansino. "Opuntia ficus-indica L. Mill Residues—Properties and Application Possibilities in Food Supplements." Applied Sciences 10, no. 9 (May 7, 2020): 3260. http://dx.doi.org/10.3390/app10093260.
Повний текст джерелаАнотація:
Recently, industry has been focusing on the development of new products made from food by-products in order to reduce and take advantage of food wastes. The objective of this study was to evaluate tablet formulations developed by mixing two commercial excipients, microcrystalline cellulose (M) and α-lactose-monohydrate (L), added with powder from residues (mesocarp and pericarp) of green and red (G and R) cactus pear fruit (Opuntia ficus-indica L. Mill), having the following formulations: green with microcrystalline cellulose (GM), green with lactose (GL), red with microcrystalline cellulose (RM), and red with lactose (RL). The results showed lower disintegration times for the tablets with microcrystalline cellulose. The fiber functional properties presented good values for lipid and water holding capacity. There was a higher total phenolic content (TPC) in formulations with green cactus pear residue powder with microcrystalline cellulose and lactose (GM and GL, respectively), but the DPPH and ferric reducing/antioxidant power (FRAP) values were higher in the formulations with red cactus pear residues (RM and RL), while ABTS values were similar among all formulations. In conclusion, tablets made from Opuntia residues are proposed as a product of interest for the food supplement industry because of the good quality parameters and the functional and antioxidant properties that they provide.
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Gul, Melek, and Serpil Eryılmaz. "Synthesis, Antioxidant Activity and Theoretical Investigation of Isoxazolines Derivatives of Monoterpenoids." Letters in Organic Chemistry 16, no. 6 (April 23, 2019): 501–10. http://dx.doi.org/10.2174/1570178616666181226154540.
Повний текст джерелаАнотація:
The 3+2 cycloaddition reactions are important to generate five-membered heterocyclic compounds as well as altering biological activity effects based on structure. In the study, we synthesized new isoxazoline derivatives of different monoterpenoids and examined the structure analysis using spectroscopical analysis methods, reveal changes in the theoretical analysis related to the biological activity. These new compounds exhibit antioxidant activities; DPPH radical scavenging, ferric reducing, metal chelating activities which are significantly higher than the related commercial monoterpenoids. Theoretical approaches on the compounds containing isoxazole moiety have been performed by the DFT/B3LYP/method, 6-31G(d,p) basis set in the ground state. The global and local chemical reactivity properties of the compounds were investigated by considering the values of electronegativity, global hardness-softness, electronic chemical potential, electrophilicity index and condensed Fukui functions, local softness and local electrophilicity index. Furthermore, total energy, FMOs energy values and the dipole moment (µ), mean polarizability (α), and first order hyperpolarizability (β) values were analysed at the theoretical level to examine the polarizability characteristics of the compounds. The antioxidant activity values of the newly synthesized compounds were compared with a finding of the computational study. The results obtained exhibited good correlation on some parameters.
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Lotito, V., G. Mininni, and L. Spinosa. "Models of Sewage Sludge Conditioning." Water Science and Technology 22, no. 12 (December 1, 1990): 163–72. http://dx.doi.org/10.2166/wst.1990.0111.
Повний текст джерелаАнотація:
Models of sewage sludge conditioning are needed in order to assess the type of chemicals to be preferred and the optimal dosages. Laboratory and pilot tests were carried out with organic and inorganic chemicals for determining their influence on sludge parameters and equipment performance. A new parameter, named “Specific Resistance to Centrifugation”, for evaluating sludge centrifugability was developed. The pilot tests confirmed that satisfactory solids recoveries can be obtained when the value of this parameter is of 20-30 s. A correlation was also found between the “Specific Resistance to Centrifugation” and dosage, molecular weight and charge density of polyelectrolytes. Other correlations were determined for Specific Resistance to Filtration and compressibility coefficient. In conditioning by inorganic chemicals it was found that ferric chloride mainly influences the specific resistance, while lime the compressibility coefficient. Due to some discrepancies between the classical theory of filtration and actual results of pilot tests, a new parameter called “Average Specific Resistance to Filtration” was proposed. As far as beltpress operation is concerned, a laboratory test was defined thus allowing the drainage phase and the compression one to be simulated. The final cake concentration can be also predicted and it was found a good agreement with the actual experimental values.
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BARRIUSO, E., J. M. PORTAL, and F. ANDREUX. "CINÉTIQUE ET MÉCANISME DE L'HYDROLYSE ACIDE DE LA MATIÈRE ORGANIQUE D'UN SOL HUMIFÈRE DE MONTAGNE." Canadian Journal of Soil Science 67, no. 3 (August 1, 1987): 647–58. http://dx.doi.org/10.4141/cjss87-061.
Повний текст джерелаАнотація:
From the surface horizon of an organic-rich mountain soil, humic and fulvic acids, and organo-mineral compounds including clay and hydroxy-metal colloids, were separated and purified. Each of these fractions was hydrolyzed in 3.0 M HCl under reflux, then the reaction parameters related to the solubilization of carbon and nitrogen and to the kinetics of hydrolysis were calculated. Acid hydrolysis was interpreted as the result of two successive steps: first a rapid electrophilic attack of heteroatomic C-O and C-N bonds by protons, then a slow nucleophilic hydration of the protonated bonds. Electron delocalization in these bonds, which increased with the polycondensation degree of organic compounds, and with their adsoprtion on mineral surfaces, resulted in an increase in their stability to hydrolysis. Fulvic acids were found to be the less stable material, and lead to predominantly anionic hydrolysis products. Clay-sized humin was the most stable material and yielded mainly cationic hydrolysates. The stability to hydrolysis and the humification degree of organic matter in the fractions generally coincided, and decreased in the following order: fine clay-sized humin > alkali dispersible organo-mineral colloids > > humic acids > hydroxy-ferric organic colloids > hydroxy-aluminium organic colloids = fulvic acids. Key words: Organo-mineral complex, humic substances, acid hydrolysis, carbon, nitrogen
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Opalić, M., Z. Domitran, D. Komes, A. Belščak, D. Horžić, and D. Karlović. "The Effect of Ultrasound Pre-Treatment and Air-Drying on the Quality of Dried Apples." Czech Journal of Food Sciences 27, Special Issue 1 (June 24, 2009): S297—S300. http://dx.doi.org/10.17221/606-cjfs.
Повний текст джерелаАнотація:
In order to develop environmentally sound, energy inexpensive and well scalable drying techniques that maintain high quality of dried fruit, optimisation of integrated process (ultrasound and air-drying) in the production of dried apples was conducted. Selected quality parameters of fresh and dried apples (variety Goldparmâne) resulting from different duration of ultrasonic pre-treatment and air-drying were compared. Sugars were determined spectrophotometrically using an enzymatic method. Content of total phenols and flavonoids was determined spectrophotometrically with the Folin-Ciocalteau assay, while the antioxidant capacity was evaluated by using ABTS (2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) and FRAP (Ferric Reducing/Antioxidant Power) assays. Sensory properties of dried apples were investigated according to the Quantitative Descriptive Analysis. In combination with the same air-drying conditions, prolonged ultrasound pre-treatment led to a decrease in total phenols and flavonoids, as well as in the antioxidant capacity of dried apples. Difference in drying time had no significant effect on the content of total phenols and flavonoids, as well as antioxidant capacity. The sample dried without the ultrasound pre-treatment was evaluated as the most sensory acceptable. The content of glucose and fructose correlated well with total phenols and flavonoids, as well as with antioxidant capacity of apple samples.
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Sarkar, Atreyi, and Uma Ghosh. "Optimization of the extraction of natural phenolic antioxidants from the seeds of Tamarindus indica L. - an undervalued by product of food processing - using response surface methodology." Acta Biologica Szegediensis 62, no. 1 (August 23, 2018): 67–74. http://dx.doi.org/10.14232/abs.2018.1.67-74.
Повний текст джерелаАнотація:
The seeds of Tamarindus indica are known to possess a wide range of phenolic compounds with high antioxidant activity as measured by the ferric reducing antioxidant power (FRAP). In the present study, the optimum conditions for the extraction of crude phenolic antioxidants from Tamarind seed were determined using response surface methodology (RSM). A central composite design (CCD) was used to investigate the effects of four independent variables, namely concentration of extractable solids in solvent (g/ml; X1), extraction time (h; X2), extraction temperature (°C; X3) and solvent concentration (%, v/v; X4) on the responses of total polyphenol content (TPC) and FRAP. The CCD consisted of 30 experimental runs. A second-order polynomial model was used for predicting the responses. Canonical analysis of the surface responses revealed that the predicted optimal conditions for the maximal yield of TPC and FRAP were concentration of extractable solids in solvent of 0.049 g/ml, extraction time of 3.24 h, extraction temperature of 45 °C and a solvent concentration of 50%. The experimental values in the optimised condition coincided with the predicted ones within a 95% confidence interval, hence indicating the suitability of the model and the success of RSM in optimizing the extraction parameters.
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Chiavola, Agostina, Emilio D’Amato, and Camilla Di Marcantonio. "Comparison of Adsorptive Removal of Fluoride from Water by Different Adsorbents under Laboratory and Real Conditions." Water 14, no. 9 (April 29, 2022): 1423. http://dx.doi.org/10.3390/w14091423.
Повний текст джерелаАнотація:
The fluoride removal capability of six different adsorbents (four commercial, i.e., titanium dioxide-TiO2, ArsenXPnp-A33E, granular activated carbon (GAC) and granular ferric hydroxide (GFH), and two laboratory media, i.e., nano-fine media and nano-granular media) was determined under batch conditions using synthetic and real contaminated water containing arsenic and vanadium. The kinetic and equilibrium characteristics of the adsorption process under different operating conditions (pH value, initial fluoride concentration, adsorbent dosage, water composition) were obtained. Among the tested adsorbents, TiO2 showed the highest adsorption capacity; it was also capable of reducing fluoride concentration below the limit set for drinking water without pH control. TiO2 still remained the best adsorbent in the treatment of real contaminated groundwater, where it was also capable of efficiently removing both arsenic and vanadium. The other adsorbents were capable of achieving the same fluoride reduction, although only for acid pH. The nano-sized laboratory media showed an adsorption removal efficiency below that of TiO2 but superior to that of A33E, GAC and GFH. Among the investigated parameters, the removal efficiency was mainly affected by adsorbent dosage and pH. The pseudo-second order model best fitted the kinetic experimental data of all the media. The maximum adsorption capacity predicted by this model was in the following decreasing order: TiO2 > A33E > GAC > GFH. The removal capability of all the media drastically decreased due to the presence of competitive ions and unfavorable pH conditions. The best isotherm model changed depending on the type of adsorbent and pH conditions.
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Krouma, Abdelmajid. "Differential response of pea (Pisum sativum L.) genotypes to iron deficiency in relation to the growth, rhizosphere acidification and ferric chelate reductase activities." June 2021, no. 15(06):2021 (June 10, 2021): 925–32. http://dx.doi.org/10.21475/ajcs.21.15.06.p3171.
Повний текст джерелаАнотація:
Calcareous soils are known problematic lands for agricultural systems because of the low availability of nutrients, particularly iron (Fe). The so-called strategy I plant (e. g. Pea, Pisum sativum L.) which groups dicotyledons and monocots other than grasses, developed root membrane activities that contribute to the improvement of Fe availability. Among the functions considered to be a critical phase in iron absorption is rhizosphere acidification by H-ATPase and Fe(III) reduced by Fe(III) chelate reducctase (FeCR). In order to experimentally investigate the importance of root FeCR in Fe nutrition, its relationship with rhizosphere acidification and the genotypic differences in response to iron deficiency in pea (Pisum sativum L.), a glasshouse experiment was conducted hydroponically on four genotypes Merveille de Kelvedon (MK); Lincoln (Lin); Douce de Provence (DP) and Alexandra (Alex). Plants of each genotype were distributed into two plots, the first one received full nutrient solution (+ Fe), the second one received nutrient solution devoid of iron (- Fe). Plant growth, Fe distribution, SPAD index and root acidification and ferric chelate reductase activities were evaluated. Fe deficiency decreased plant growth and SPAD index along with the significant increase of H-ATPase and FeCR activities. Some genotypic differences were observed as follows; Alex showed high tolerance to Fe deprivation as compared to other genotypes. Important H-ATPase and FeCR activities, high Fe use efficiency and adequate membrane efficiency are the main reasons for this tolerance. These physiological parameters could be used as tools of tolerance for further breeding programs
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Villota, Natalia, Luis Miguel Camarero, Jose Maria Lomas, and Mikel Legaristi. "Kinetic Modelling of Photoconversion of Phenol by a Photo-Fenton Reagent and UV." International Journal of Chemical Reactor Engineering 12, no. 1 (January 1, 2014): 405–16. http://dx.doi.org/10.1515/ijcre-2013-0130.
Повний текст джерелаАнотація:
Abstract This study analyses the oxidation of phenol using Fenton reagent in presence of ultraviolet light, enhancing the mineralization capacity of the treatment. Phenol oxidation generates reaction intermediates more toxic and refractory than phenol itself. Thus, the reaction must be carried out under harder conditions, leading these compounds to biodegradable acids that can be dumped into public sewages. Then, this paper considers a complete kinetic modelling of the phenol oxidation stages, differentiating the formation rate of species generated through ortho, meta and para pathways. The model is based on a mechanism of series reactions, wherein a first step degrades into dihydroxylated intermediates (catechol, resorcinol and hydroquinone). A second stage leads to tri-hydroxylated rings (pyrogallol) and benzoquinones (o-benzoquinone and p-benzoquinone), and both species may coexist in the reaction mixture. Next, if conditions are sufficiently oxidizing, they decompose into biodegradable organic acids (muconic, formic or acetic acids). In this mechanism, the parallel reactions, due to the presence of the metal catalyst, are considered. So, on one hand, there is a formation of metal complexes between species ortho-substituted and ferric ions from the catalyst. On the other hand, there is a precipitation of part of the initial catalyst as ferric hydroxide, due to the presence of ultraviolet light, which is determined by the operation pH. Studies have been performed on the selectivity of the oxidation in function of the reaction conditions. Then, when operating with pH = 3.0, oxidation was favoured via ortho-substituted compounds. Treatment is advisable within Pho = 100–300 mg/L, being necessary to apply molar ratios of oxidant above R = 6.0 mol H2O2/mol C6H5OH to degrade these intermediates. Moreover, kinetic constants of formation of generated species are estimated, supposing that follows an evolution comparable to first-order reactions. Analysis checks that these kinetic constants present some relation to the operating conditions. In this way, a mathematical estimation is presented, showing the dependence of the kinetics on the parameters controlling the process (pH, initial concentration of phenol, oxidant molar ratio, catalyst dosage and temperature). As a result, the behaviour of the system can be predicted within the considered range.
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Mahmoud, Ahmed S., Mohamed K. Mostafa, and Robert W. Peters. "A prototype of textile wastewater treatment using coagulation and adsorption by Fe/Cu nanoparticles: Techno-economic and scaling-up studies." Nanomaterials and Nanotechnology 11 (January 2021): 184798042110411. http://dx.doi.org/10.1177/18479804211041181.
Повний текст джерелаАнотація:
This study aims to investigate the efficiency of a pilot prototype system comprising coagulation/flocculation, filtration, and nano-bimetallic iron/copper (Fe/Cu) degradation and adsorption units for the removal of chemical oxygen demand (COD), biological oxygen demand (BOD), color, total nitrogen (TN), total phosphorus (TP), and TSS from real textile wastewater. The total removal efficiencies of the system were 96, 98, 82, 69, 88, and 97%, respectively, using 0.5 g/L ferric chlorides as a coagulant under an optimum adsorption condition of pH 6.0, nano-dosage 1.4 g/L, contact time 80 min, and stirring rate 250 r/min at room temperature. Adsorption isotherms indicated that the removal of COD and TP obeys both Koble–Corrigan and Freundlich adsorption models, removal of color obeys both Koble–Corrigan and Hill adsorption models, and removal of TN and TSS obeys Koble–Corrigan and Khan models, respectively. Avrami kinetic models adequately describe the adsorption data for COD, BOD, TN, and TSS, while pseudo-second-order and intraparticle models described the removal mechanism of color and TSS, respectively. An artificial neural network (ANN) with r2-value exceeding 0.98 is accurate and can be used with confidence in predicting removal efficiencies of the targeted parameters. Sensitivity analysis results showed that the initial concentration was the most influential parameter for TSS removal with relative importance greater than 25%, while the bimetallic Fe/Cu dosage was the most influential factor for all other studied parameters with relative importance greater than 40%. The total treatment cost of the proposed system per m3 after scaling up was found to be US$4.5 for reuse of the treated water for the irrigation of forest trees.
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Koczka, Noémi, Éva Stefanovits-Bányai, and Attila Ombódi. "Total Polyphenol Content and Antioxidant Capacity of Rosehips of Some Rosa Species." Medicines 5, no. 3 (August 4, 2018): 84. http://dx.doi.org/10.3390/medicines5030084.
Повний текст джерелаАнотація:
Background: Rosehips, the fruits of Rosa species, are well known for their various health benefits like strengthening the immune system and treating digestive disorders. Antioxidant, anti-inflammatory, and cell regenerative effects are also among their health enhancing impacts. Rosehips are rich in compounds having antioxidant properties, like vitamin C, carotenoids, and phenolics. Methods: Total polyphenol content (Folin-Ciocalteu’s method), and in vitro total antioxidant capacity (ferric-reducing ability of plasma, FRAP) in rosehips of four Rosa species (R. canina, R. gallica, R. rugosa, R. spinosissima) were determined and compared. Ripe fruits were harvested at two locations. Water and ethanolic extracts of dried fruit flesh were analyzed. Results:R. spinosissima had the highest total phenolic content and antioxidant capacity, significantly higher than the other investigated Rosa species. Both parameters were reported in decreasing order for R. spinosissima > R. canina > R. rugosa > R. gallica. Ethanolic extracts of rosehips showed higher phenolic content and antioxidant activity than water extracts. Antioxidant properties were influenced by the growing site of Rosa species. Conclusions: This study indicates that R. spinosissima exhibited the greatest phenolic and antioxidant content, and therefore can be used as a reliable source of natural antioxidants, and serve as a suitable species for further plant breeding activities. Furthermore, investigations of various Rosa species for their antioxidant properties may draw more attention to their potential as functional foods.
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Roushdy, Mai Hassan. "Heterogeneous Biodiesel Catalyst from Steel Slag Resulting from an Electric Arc Furnace." Processes 10, no. 3 (February 25, 2022): 465. http://dx.doi.org/10.3390/pr10030465.
Повний текст джерелаАнотація:
Biodiesel is one of the most environmentally friendly and renewable fuels, as it is a non-polluting fuel and is made from living resources, such as vegetable oils. The steel industry generates a variety of solid wastes, including electric arc furnace slag (EAFS). The synthesis of biodiesel from waste sunflower cooking oil was examined in this study, utilizing EAFS as a catalyst, which mainly contains ferric and ferrous oxides, calcium oxide, and silica. To evaluate their impact on biodiesel production, four independent variables were chosen: temperature (50–70 °C), catalyst loading (1–5%), methanol-to-oil (M:O) molar ratio (5–20), and time (1–4 h). The response surface methodology (RSM) was used to examine the impact of independent variables on reaction response, which is the biodiesel yield. This process was carried out using a design expert program by central composite design (CCD). A model was constructed, and showed that the biodiesel yield was directly proportional to all independent reaction parameters. The predicted model’s adequacy was investigated using analysis of variance (ANOVA), which showed that it is an excellent representative of the results. The optimization of reaction conditions was investigated in order to maximize biodiesel yield at minimal reaction temperature and time, achieving a 94% biodiesel yield at a 20:1 M:O molar ratio, 5% catalyst loading, 55.5 °C reaction temperature, and 1 h reaction time.
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Garcia-Vaquero, Marco, Gaurav Rajauria, Brijesh Tiwari, Torres Sweeney, and John O’Doherty. "Extraction and Yield Optimisation of Fucose, Glucans and Associated Antioxidant Activities from Laminaria digitata by Applying Response Surface Methodology to High Intensity Ultrasound-Assisted Extraction." Marine Drugs 16, no. 8 (July 30, 2018): 257. http://dx.doi.org/10.3390/md16080257.
Повний текст джерелаАнотація:
The objectives of this study were to employ response surface methodology (RSM) to investigate and optimize the effect of ultrasound-assisted extraction (UAE) variables, temperature, time and amplitude on the yields of polysaccharides (fucose and total glucans) and antioxidant activities (ferric reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picryl-hydrazyl radical scavenging activity (DPPH)) from Laminaria digitata, and to explore the suitability of applying the optimum UAE conditions for L. digitata to other brown macroalgae (L. hyperborea and Ascophyllum nodosum). The RSM with three-factor, four-level Box-Behnken Design (BBD) was used to study and optimize the extraction variables. A second order polynomial model fitted well to the experimental data with R2 values of 0.79, 0.66, 0.64, 0.73 for fucose, total glucans, FRAP and DPPH, respectively. The UAE parameters studied had a significant influence on the levels of fucose, FRAP and DPPH. The optimised UAE conditions (temperature = 76 °C, time = 10 min and amplitude = 100%) achieved yields of fucose (1060.7 ± 70.6 mg/100 g dried seaweed (ds)), total glucans (968.6 ± 13.3 mg/100 g ds), FRAP (8.7 ± 0.5 µM trolox/mg freeze-dried extract (fde)) and DPPH (11.0 ± 0.2%) in L. digitata. Polysaccharide rich extracts were also attained from L. hyperborea and A. nodosum with variable results when utilizing the optimum UAE conditions for L. digitata.
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Borrajo, Paula, Mirian Pateiro, Mohammed Gagaoua, Daniel Franco, Wangang Zhang, and José Manuel Lorenzo. "Evaluation of the Antioxidant and Antimicrobial Activities of Porcine Liver Protein Hydrolysates Obtained Using Alcalase, Bromelain, and Papain." Applied Sciences 10, no. 7 (March 27, 2020): 2290. http://dx.doi.org/10.3390/app10072290.
Повний текст джерелаАнотація:
In order to make the by-products generated from the porcine industry more valuable, pig livers were used in this trial to obtain protein hydrolysates. Three proteases (alcalase, bromelain, and papain) were utilized for enzymatic hydrolysis with two different durations, 4 and 8 hours. Ultrafiltration process was used for the recovery of the extracts, employing three different membrane pore sizes (30, 10, and 5 kDa). The porcine livers contained considerable amounts of protein (19.0%), considering they are almost composed of water (74.1%). The antioxidant activity of the obtained hydrolysates was investigated using four antioxidant methods (2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, 2-2′-Azino-di-[3-ethylbenzthiazoline sulfonate] (ABTS) radical scavenging activity, ferric reducing antioxidant power assay (FRAP), and oxygen radical absorbance capacity assay (ORAC)). Antibacterial properties were also measured against Gram-negative and Gram-positive bacteria. Results indicated that the three studied factors (type of enzyme, membrane pore size, and time) significantly affected the parameters evaluated. Hydrolysates obtained at 8 hours with alcalase had the best antioxidant properties. The 30 kDa alcalase extracts exhibited the highest DPPH (562 µg Trolox/g), FRAP (82.9 µmol Fe2+/100 g), and ORAC (53.2 mg Trolox/g) activities, while for ABTS the 10 kDa alcalase showed the higher values (1068 mg ascorbic acid/100 g). Concerning the antibacterial activity, 30 kDa hydrolysates obtained with bromelain for 4 hours exhibited the highest antimicrobial capacity, providing an inhibition of 91.7%.
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Liang, Jianjun, Meiling Liu, and Yufei Zhang. "Cd(II) removal on surface-modified activated carbon: equilibrium, kinetics and mechanism." Water Science and Technology 74, no. 8 (July 16, 2016): 1800–1808. http://dx.doi.org/10.2166/wst.2016.338.
Повний текст джерелаАнотація:
Commercial pulverous activated carbon (AC-0) was modified through two steps: oxidize AC-0 acid firstly, impregnate it with iron using ferric chloride secondly. Orthogonal experiment was conducted then to prepare modified activated carbon with high Cd(II) adsorption capacity (ACNF). Batch adsorption experiments were undertaken to determine the adsorption characteristics of Cd(II) from aqueous solution onto AC-0 and ACNF and the effect of pH, contact time and initial Cd(II) concentration. The results indicate that: the adsorption behavior of Cd(II) on ACNF can be well fitted with Langmuir model, and the maximum adsorption capacity of ACNF was 2.3 times higher than that of AC-0, supporting a monolayer coverage of Cd(II) on the surface. The kinetics of the adsorption process can be described by pseudo-second-order rate equation very well, and the adsorption capacity increased from 0.810 mg/g to 0.960 mg/g after modification. Compared with AC-0, the kinetic parameters of ACNF showed a higher adsorption rate through the aqueous solution to the solid surface and a lower intraparticle diffusion rate. Surface modification resulted in a lower Brunauer–Emmett–Teller (BET) surface area and pore size because of the collapse and blockage of pores, according to the X-ray diffraction (XRD) analysis, while the total number of surface oxygen acid groups increased, and this was supposed to contribute to the enhanced adsorption capacity of modified activated carbon.