Magnetized manganese oxide nanocomposite for effective decontamination of Cd(II) from wastewaters

2016 ◽  
Vol 74 (12) ◽  
pp. 2762-2772 ◽  
Author(s):  
Ana Pacheli Heitmann ◽  
Gabriela C. Silva ◽  
Paulo Renato P. Paiva ◽  
Maria Sylvia S. Dantas ◽  
Virginia S. T. Ciminelli ◽  
...  
Keyword(s):  
Manganese Oxide ◽  
Large Scale ◽  
Transmission Electron Microscopy Image ◽  
Hysteresis Curve ◽  
A Value ◽  
Transmission Electron ◽  
Microscopy Image ◽  
Pseudo Second Order ◽  
Solid Liquid ◽  
Solid Liquid Separation

In this study, a composite with magnetic properties has been successfully synthesized by a novel and environmentally friendly route and is applied to Cd(II) adsorption for water decontamination. The quantification of the phases obtained by Rietveld refinement has shown the presence of 84% of Mn3O4 and 16% of Fe3O4. Transmission electron microscopy image shows an aggregate of Mn3O4 nanoparticles without specific orientation and the predominance of octahedral morphology with nanoparticles size estimated around 25–30 nm. The Cd(II) adsorption isotherm is fitted using the Langmuir–Freundlich model. The estimated maximum adsorption capacities of Cd(II) at pH 6 and 7 are similar (0.28 ± 0.02 and 0.31 ± 0.02 mg/m2, respectively). The kinetic results show that the studied system follows the pseudo-second-order model. The Raman results indicate that Cd is being specifically adsorbed by the Mn3O4 in the composite. The hysteresis curve of the composite Mn3O4/Fe3O4 has changed when compared to the pure magnetite; however, the coercive field after the addition of manganese oxide remains unaltered and does not change with a value around 158 Oe. The turbidity tests showed that the magnetic sedimentation was efficient and promising for wastewater treatment in large scale. These materials can be conveniently recovered by magnetic separation, avoiding the filtration steps, which will make easier the solid–liquid separation operation that follows the adsorption process.

Investigations on the filtration of natural aquatic suspensions supported by dosing small amounts of Fe(III)-salts (βFe ≤ 0.1 mg.L-1): mode of action and basic design criteria

2002 ◽  
Vol 2 (2) ◽  
pp. 91-98
Author(s):  
R. Winzenbacher ◽  
R. Schick ◽  
H.-H. Stabel ◽  
M. Jekel
Keyword(s):  
Large Scale ◽  
Suspended Solids ◽  
Iron Hydroxides ◽  
Essential Step ◽  
Iron Salts ◽  
Alkaline Earths ◽  
Co Precipitation ◽  
Solid Liquid ◽  
Solid Liquid Separation

Improved removal of particles during the treatment of natural aquatic suspensions has been achieved by pre-ozonation and the addition of small quantities of iron salts (βFe ≤ 0.1 mg.L-1; “Fe(III)-assisted filtration”) followed by rapid filtration. As shown by investigations on a large-scale installation at Lake Constance Water Supply, this procedure reliably reduces suspended solids by at least 2-3 powers of ten in long-term use. However, the high efficacy of Fe(III)-assisted filtration cannot be explained on the basis of known coagulation mechanisms (like adsorption-charge neutralization, co-precipitation). Instead, the essential step was found to be the conditioning of the filter medium by coating it with colloids containing Fe(OH)3, and this “Fe coating” process occurs only in the presence of alkaline earths (especially Ca2+). According to further experiments, the enhanced solid-liquid separation was ultimately traced to chemical interactions such as the formation of calcium-organic association structures between the iron hydroxides and other solids. For design of Fe(III)-assisted filtration steps, finally, a βCa/DOC ratio above 40 mg.mg-1 and pre-oxidation with ozone dosages not exceeding 2 mg O3/mg DOC was recommended.

Ferroelectric domains in PZT ceramics at the morphotropic phase boundary. Can the splitting of reflections in SAED patterns be used for the distinction of different pseudo-cubic phases?

2012 ◽  
Vol 45 (4) ◽  
pp. 766-777 ◽  
Author(s):  
Roland Schierholz ◽  
Hartmut Fuess
Keyword(s):  
Domain Wall ◽  
Transmission Electron Microscopy Image ◽  
Monoclinic Structure ◽  
Monoclinic Symmetry ◽  
Pzt Ceramics ◽  
Selected Area Electron Diffraction ◽  
Cubic Phases ◽  
Transmission Electron ◽  
Microscopy Image ◽  
Ferroelectric Domains

Tetragonal, rhombohedral and monoclinic ferroelectric domains can all occur in morphotropic PbZr1−xTixO3(PZT) ceramics. In this article, the influence of these domains on the splitting of reflections in selected area electron diffraction (SAED) patterns along the main pseudo-cubic zone axes is reported. The orientation of the domain wall in a transmission electron microscopy image with respect to the splitting of reflections in the diffraction pattern has to be considered for the interpretation. The distinction of tetragonal and rhombohedral splitting is achieved for a pronounced splitting except for 〈111〉 with the domain wall edge on. As the monoclinic structure contains tetragonal as well as rhombohedral distortions, the distinction of monoclinic symmetry from tetragonal and rhombohedral based only on the splitting of reflections is not possible. Conceivable models of configurations of monoclinic subdomains inside the existing tetragonal or rhombohedral microdomains are derived from group–subgroup relations. Some experimental observations are given, which can only be explained by these models.

Calculation and Analysis of Multifractal Spectrum of Sinter Surface

2013 ◽  
Vol 750-752 ◽  
pp. 2267-2270
Author(s):  
Zhi Min Cui ◽  
Rong Li Sang ◽  
Yuan Liang Li ◽  
Qing Jun Zhang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Pore Structure ◽  
Multifractal Spectrum ◽  
Transmission Electron Microscopy Image ◽  
Structure Change ◽  
Electron Microscopy Image ◽  
Transmission Electron ◽  
Microscopy Image ◽  
Fractal Spectrum

Multifractal spectrums of sinter with different alkalinity were analyzed by multifractal software. The results show that sinter pore structure change from uniform to non-uniform with the improvement of alkalinity, Δα increases from 0.53 to 0.55. The structure of sinter pore is mainly microscopic by competition between macropores and micropores, Δf changes from 0.14 to-0.44. The distribution of sinter pores is quantitatively characterized by multi-fractal spectrum, which is consistent with transmission electron microscopy image.

Synthesis of Ultrafine MgAl2O4 Powders by Nitrate-Citrate Sol-Gel Combustion Process

2008 ◽  
Vol 368-372 ◽  
pp. 407-408
Author(s):  
Long Chen ◽  
Qi Zhang ◽  
Wen Ping Chen ◽  
Yao Gang Li ◽  
Yan Mo Chen ◽  
...  
Keyword(s):  
Sol Gel ◽  
Combustion Process ◽  
Xrd Analysis ◽  
Transmission Electron Microscopy Image ◽  
Solid State Reactions ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Microscopy Image ◽  
Gel Combustion ◽  
Lower Temperature

Ultrafine MgAl2O4 powders were synthesized by a nitrate-citrate sol-gel combustion process using Al(NO3)3·9H2O, Mg(NO3)2·6H2O and C6H8O7·H2O as initial materials. The result of X-ray diffraction (XRD) analysis indicated that single-phase MgAl2O4 powder could be obtained at 850 oC, which is much lower than that needed in solid-state reactions. Transmission electron microscopy image showed that the as-prepared powder was in the nano scale and little agglomerate exited. It is concluded that this process need shorter time, lower temperature, and simple equipments.

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