Aerocellulose: New Highly Porous Cellulose Prepared from Cellulose−NaOH Aqueous Solutions

2008 ◽  
Vol 9 (1) ◽  
pp. 269-277 ◽  
Author(s):  
Roxane Gavillon ◽  
Tatiana Budtova
Keyword(s):  
Aqueous Solutions ◽  
Highly Porous

scholarly journals Adsorption of Cu(II) from aqueous solution using raw peat: preliminary results

2019 ◽  
Vol 98 ◽  
pp. 06010 ◽  
Author(s):  
Olga Naymushina ◽  
Olga Gaskova
Keyword(s):  
Aqueous Solutions ◽  
Active Sites ◽  
West Siberia ◽  
Maximum Adsorption Capacity ◽  
Adsorption Data ◽  
Removal Of Heavy Metals ◽  
Freundlich Adsorption Isotherm ◽  
Time Variations ◽  
Highly Porous ◽  
Highly Porous Material

Peat is a polar, highly porous material that could have significant applications as an adsorbent for removal of heavy metals from aqueous solutions. Various functional groups in lignin allow such compounds to bind on active sites of peat. The adsorption of Cu (II) from aqueous solutions on peat from the West Siberia was studied in the concentration range of 10–150 mg/L and time variations of 0.25-12 hours. The pH of the solutions varied over a range of 3.2–4.3. The adsorption data could be fitted to a Freundlich adsorption isotherm and the maximum adsorption capacity of peat was determined to be 2.5⋅10-3 mmol/g when the initial concentration for Cu2+ was at its minimum (0.05 mmol/L), and the time of adsorption was 30 minutes.

Replacement of anhydrite by hydroxyapatite: kinetic and textural characteristics

2020 ◽  
Author(s):  
Ana Roza ◽  
Amalia Jiménez ◽  
Lurdes Fernández-Díaz
Keyword(s):  
Aqueous Solutions ◽  
Molar Volume ◽  
Sedimentary Basins ◽  
Rietveld Analysis ◽  
Calcium Sulphate ◽  
Wide Range ◽  
Polycrystalline Aggregates ◽  
Diagenetic Evolution ◽  
Inner Region ◽  
Highly Porous

<p>Interface-coupled dissolution-precipitation (ICDP) reactions lead to the pseudomorphic replacement of minerals in a wide range of geological settings, exerting a significant impact in geochemical cycles (Putnis 2002). ICDP reactions play a major role in the diagenetic evolution of sedimentary rocks, specially of limestones and evaporites. Recent experimental works have studied ICDP reactions that lead to the formation of CaCO<sub>3</sub> pseudomorphs after anhydrite (CaSO<sub>4</sub>), upon interaction of the latter phase with carbonated aqueous solutions. These pseudomorphs are highly porous polycrystalline aggregates that mainly consist of calcite (Roncal-Herrero et al. 2018; Altree-Williams et al. 2017). The formation of a large volume of interconnected microporosity that balances the molar volume loss associated to the anhydrite-calcite transformation as well as the specific arrangement of this microporosity, influenced by the existence of epitactic relationships between anhydrite and calcite, facilitate the progress of the ICDP reaction.</p><p>Here, we study the ICDP reaction that leads to the formation of hydroxyapatite (Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>(OH)) pseudomorphs after the interaction of anhydrite with phosphate-bearing aqueous solutions at temperatures 90 to180ºC during times that range from one hour to five weeks. The X-ray diffraction Rietveld analysis of the transformed samples indicates that the kinetics of the pseudomorphic transformation of anhydrite into hydroxyapatite strongly depends on temperature.  Thus, while at 180ºC a 100% transformation yield is attained in few hours, it takes five weeks of interaction at 90ºC. Scanning Electron Microscopy imagining of transformed samples shows the very good preservation of both, the original external shape and microtopographic features of anhydrite crystals. On cross-cut sections of partially replaced by hydroxyapatite anhydrite crystals we observe that the transformation advances from the surface inwards, with sharp separating the by replaced layer from the unreacted anhydrite core. Furthermore, this replaced layer is structured into a compact ~ 50 µm thick outer rim, which consists of coalescent small (~ 5 µm) hydroxyapatite crystals, and a progressively thickening inner region formed by hydroxyapatite columnar crystals in a stockade-like arrangement. This latter region is highly porous. We interpret these results taking into consideration the differences in solubility and molar volume between anhydrite and hydroxyapatite as well as the similarities/differences between the crystal structures of these phases. By comparing the characteristics of different ICDP reactions that involve anhydrite in sedimentary basins we derive implications about the diagenetic evolution of calcium sulphate evaporites. </p><p> </p><p>Altree-Williams, Alexander, et al. (2017). <em>ACS Earth and Space Chemistry</em> 1.2, 89-100.</p><p>Roncal-Herrero, Teresa, et al. (2017): <em>American Mineralogist</em> 102.6, 1270-1278.</p><p>Putnis A: (2002): <em>Mineralogical Magazine</em> 66.5, 689-708.</p><p> </p><p> </p>

Application of highly porous materials for simazine removal from aqueous solutions

2016 ◽  
Vol 37 (19) ◽  
pp. 2428-2434 ◽  
Author(s):  
Serena Esposito ◽  
Edoardo Garrone ◽  
Antonello Marocco ◽  
Michele Pansini ◽  
Paola Martinelli ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Porous Materials ◽  
Highly Porous Materials ◽  
Highly Porous

Porous PDMS structures for the storage and release of aqueous solutions into fluidic environments

Lab on a Chip ◽  
2017 ◽  
Vol 17 (14) ◽  
pp. 2517-2527 ◽  
Author(s):  
Peter Thurgood ◽  
Sara Baratchi ◽  
Crispin Szydzik ◽  
Arnan Mitchell ◽  
Khashayar Khoshmanesh
Keyword(s):  
Aqueous Solutions ◽  
Building Block ◽  
Microfluidic Systems ◽  
Passive Release ◽  
Highly Porous

This work introduces a highly porous PDMS sponge for the storage and passive release of aqueous solutions, acting as a building block for self-sufficient microfluidic systems.

Ultrathin frozen sections of yeast without aldehyde prefixation

1978 ◽  
Vol 36 (2) ◽  
pp. 58-59
Author(s):  
K. J. Böhm ◽  
a. E. Unger
Keyword(s):  
Aqueous Solutions ◽  
Biological Material ◽  
Yeast Cells ◽  
Frozen Sections ◽  
Good Preservation ◽  
Ultrathin Frozen Sections

During the last years it was shown that also by means of cryo-ultra-microtomy a good preservation of substructural details of biological material was possible. However the specimen generally was prefixed in these cases with aldehydes.Preparing ultrathin frozen sections of chemically non-prefixed material commonly was linked up to considerable technical and manual expense and the results were not always satisfying. Furthermore, it seems to be impossible to carry out cytochemical investigations by means of treating sections of unfixed biological material with aqueous solutions.We therefore tried to overcome these difficulties by preparing yeast cells (S. cerevisiae) in the following manner:

Use of fractals to describe microstructures of porous thick-film platinum electrodes

1992 ◽  
Vol 50 (1) ◽  
pp. 314-315
Author(s):  
Steven D. Toteda
Keyword(s):  
Fractal Dimension ◽  
Power Plants ◽  
Electrical Response ◽  
Cubic Phase ◽  
Platinum Electrodes ◽  
Fine Grained ◽  
Impedance Response ◽  
Platinum Particles ◽  
Energy Surfaces ◽  
Highly Porous

Zirconia oxygen sensors, in such applications as power plants and automobiles, generally utilize platinum electrodes for the catalytic reaction of dissociating O2 at the surface. The microstructure of the platinum electrode defines the resulting electrical response. The electrode must be porous enough to allow the oxygen to reach the zirconia surface while still remaining electrically continuous. At low sintering temperatures, the platinum is highly porous and fine grained. The platinum particles sinter together as the firing temperatures are increased. As the sintering temperatures are raised even further, the surface of the platinum begins to facet with lower energy surfaces. These microstructural changes can be seen in Figures 1 and 2, but the goal of the work is to characterize the microstructure by its fractal dimension and then relate the fractal dimension to the electrical response. The sensors were fabricated from zirconia powder stabilized in the cubic phase with 8 mol% percent yttria. Each substrate was sintered for 14 hours at 1200°C. The resulting zirconia pellets, 13mm in diameter and 2mm in thickness, were roughly 97 to 98 percent of theoretical density. The Engelhard #6082 platinum paste was applied to the zirconia disks after they were mechanically polished ( diamond). The electrodes were then sintered at temperatures ranging from 600°C to 1000°C. Each sensor was tested to determine the impedance response from 1Hz to 5,000Hz. These frequencies correspond to the electrode at the test temperature of 600°C.

Imaging polymers, proteins and dna in aqueous solutions with the atomic force microscope

1989 ◽  
Vol 47 ◽  
pp. 32-33
Author(s):  
S.A.C. Gould ◽  
B. Drake ◽  
C.B. Prater ◽  
A.L. Weisenhorn ◽  
S.M. Lindsay ◽  
...  
Keyword(s):  
Amino Acids ◽  
Dna Sequencing ◽  
Aqueous Solutions ◽  
Atomic Force Microscope ◽  
Piezoelectric Crystal ◽  
Atomic Force ◽  
Structure Of Molecules ◽  
Optical Lever

The atomic force microscope (AFM) is an instrument that can be used to image many samples of interest in biology and medicine. Images of polymerized amino acids, polyalanine and polyphenylalanine demonstrate the potential of the AFM for revealing the structure of molecules. Images of the protein fibrinogen which agree with TEM images demonstrate that the AFM can provide topographical data on larger molecules. Finally, images of DNA suggest the AFM may soon provide an easier and faster technique for DNA sequencing.The AFM consists of a microfabricated SiO2 triangular shaped cantilever with a diamond tip affixed at the elbow to act as a probe. The sample is mounted on a electronically driven piezoelectric crystal. It is then placed in contact with the tip and scanned. The topography of the surface causes minute deflections in the 100 μm long cantilever which are detected using an optical lever.

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