scholarly journals Surface adsorption of stearic acid by natural calcite

2009 ◽  
Vol 63 (2) ◽  
pp. 101-106 ◽  
Author(s):  
Slavica Mihajlovic ◽  
Aleksandra Dakovic ◽  
Zivko Sekulic ◽  
Deana Iles ◽  
Milan Kragovic
Keyword(s):  
Stearic Acid ◽  
Active Sites ◽  
Solution Method ◽  
Surface Adsorption ◽  
Exothermic Peak ◽  
Test Results ◽  
Dry Coating ◽  
X Ray ◽  
Dta Curves ◽  
Hydrophobic Material

In order to obtain hydrophobic material, the surface of natural limestone with the high content of calcite (>95%), was treated with 0.5, 1, 1.5, 2, 3 and 4% of stearic acid. Two methods were used for modification: the solution method and the dry coating. The obtained products were characterized using the thermal analysis (DT/TG), X-ray powder diffraction analysis (XRPD), scanning electron microscopy (SEM) and by the evaluation of floating test. Results of floating test showed that when the solution method was applied, the hydrophobicity arrived at above 99% when the amount of stearic acid was 1.5%, while with the dry coating the same hydrophobicity was achieved with 3% of stearic acid. From the position of the principal exothermic peak (> 310 ?C) at DTA curves, for calcites modified with dry coating and with the solution method, it can be concluded that with both modification processes, the same active sites exist at the calcite surface onto which stearic acid may be chemisorbed. However, the position and the intensity of the other exothermic peaks, indicate the differences in bonding of stearic acid at the calcite surface during the solution method and the dry coating.

scholarly journals Barium oxide as a modifier to stabilize the γ-Al2O3 structure

2016 ◽  
Vol 18 (4) ◽  
pp. 1-4 ◽  
Author(s):  
Shahram G. Pakdehi ◽  
Maryam Rasoolzadeh ◽  
Ali Saberi Moghadam
Keyword(s):  
Phase Transition ◽  
Barium Oxide ◽  
Exothermic Peak ◽  
X Ray ◽  
Α Phase ◽  
Aluminum Ions ◽  
Porous Properties ◽  
Dta Curves ◽  
Octahedral Cations

Abstract This research concentrated on the structural stability of γ-alumina (γ-Al2O3) was investigated by a combination of differential thermal analysis, X-ray diffractometry and surface-area measurements. The γ –to– θ and then α phase transitions were observed as an exothermic peak at 1000°C–1400°C in the DTA curves. The role of barium oxide as a modifier to stabilize γ-Al2O3 structure has been investigated. XRD measurements show that after calcination at 1000°C for 2 h, a significant fraction of the pure γ-Al2O3 (BaO-free) transformed to θ-Al2O3 while that the transition phase in alumina samples modified by BaO have been reduced significantly. Barium oxide, eliminate pentacoordinated aluminum ions through coordinative saturation and alter these ions into octahedral cations and effectively suppressed the γ –to– α phase transition in Al2O3, which concluded as improving the thermal stability and porous properties of the experimental samples.

scholarly journals Strengthening Sulfidation Flotation of Hemimorphite via Pretreatment with Pb2+

Minerals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 463 ◽  
Author(s):  
Yuqing Huang ◽  
Wanzhong Yin ◽  
Rongdong Deng ◽  
Dingquan Xing ◽  
Feng Rao
Keyword(s):  
Metal Ions ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Test Results ◽  
Flotation Process ◽  
X Ray ◽  
Force Microscopy ◽  
Adsorption Sites ◽  
Atomic Force ◽  
Induced Crystallization

The conventional sulfidation-xanthate flotation process that consists of sulfidization with sodium sulfide, activation by heavy-metal ions, and collection with xanthate is not sufficiently efficient for treating hemimorphite, and the dosages of the sulfurizing reagent and metal ions are large. In this study, the sulfidation flotation (Pb2+ + Na2S + Pb2+ + xanthate) of hemimorphite was strengthened by pretreating with Pb2+ before sulfidation. Microflotation test results indicated that the recovery of hemimorphite increased by 5–10% after pretreatment with Pb2+. The comprehensive results of adsorption experiments, scanning electron microscopy–energy-dispersive X-ray spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy indicated that a large amount of Pb2+ was adsorbed on the hemimorphite surface and entered the lattice, forming Zn(4−x)PbxSi2O7(OH)2·H2O. The newly formed component had an increased amount of surface sulfidation active sites and had the effect of induced crystallization, making the surface more effective for sulfidation. After the Pb2+ was added to the pulp, a large number of uniform and dense PbS species were formed on the hemimorphite surface, increasing the number of adsorption sites for xanthate and reducing the competitive adsorption of residual S2− on the xanthate.

Scanning luminescence x-ray microscopy: Progress toward selective staining using microspheres

1994 ◽  
Vol 52 ◽  
pp. 74-75
Author(s):  
C. Jacobsen ◽  
J. Fu ◽  
S. Mayer ◽  
Y. Wang ◽  
S. Williams
Keyword(s):  
Visible Light ◽  
Active Sites ◽  
Light Emission ◽  
Chinese Hamster ◽  
Polystyrene Spheres ◽  
Good Resistance ◽  
X Ray ◽  
Selective Staining ◽  
Visible Light Emission ◽  
Specific Labelling

In scanning luminescence x-ray microscopy (SLXM), a high resolution x-ray probe is used to excite visible light emission (see Figs. 1 and 2). The technique has been developed with a goal of localizing dye-tagged biochemically active sites and structures at 50 nm resolution in thick, hydrated biological specimens. Following our initial efforts, Moronne et al. have begun to develop probes based on biotinylated terbium; we report here our progress towards using microspheres for tagging.Our initial experiments with microspheres were based on commercially-available carboxyl latex spheres which emitted ~ 5 visible light photons per x-ray absorbed, and which showed good resistance to bleaching under x-ray irradiation. Other work (such as that by Guo et al.) has shown that such spheres can be used for a variety of specific labelling applications. Our first efforts have been aimed at labelling ƒ actin in Chinese hamster ovarian (CHO) cells. By using a detergent/fixative protocol to load spheres into cells with permeabilized membranes and preserved morphology, we have succeeded in using commercial dye-loaded, spreptavidin-coated 0.03μm polystyrene spheres linked to biotin phalloidon to label f actin (see Fig. 3).

Structural/Texture Evolution During Facile Substitution of Ni into ZSM-5 Nanostructure vs. its Impregnation Dispersion Used in Selective Transformation of Methanol to Ethylene and Propylene

2020 ◽  
Vol 23 ◽  
Author(s):  
Parisa Sadeghpour ◽  
Mohammad Haghighi ◽  
Mehrdad Esmaeili
Keyword(s):  
High Temperature ◽  
Physicochemical Properties ◽  
Active Sites ◽  
Catalytic Performance ◽  
Fixed Bed Reactor ◽  
Light Olefins ◽  
Isomorphous Substitution ◽  
Impregnation Method ◽  
Hydrothermal Temperature ◽  
X Ray

Aim and Objective: Effect of two different modification methods for introducing Ni into ZSM-5 framework was investigated under high temperature synthesis conditions. The nickel successfully introduced into the MFI structures at different crystallization conditions to enhance the physicochemical properties and catalytic performance. Materials and Methods: A series of impregnated Ni/ZSM-5 and isomorphous substituted NiZSM-5 nanostructure catalysts were prepared hydrothermally at different high temperatures and within short times. X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray (EDX), Brunner, Emmett and Teller-Barrett, Joyner and Halenda (BET-BJH), Fourier transform infrared (FTIR) and Temperature-programmed desorption of ammonia (TPDNH3) were applied to investigate the physicochemical properties. Results: Although all the catalysts showed pure silica MFI–type nanosheets and coffin-like morphology, using the isomorphous substitution for Ni incorporation into the ZSM-5 framework led to the formation of materials with lower crystallinity, higher pore volume and stronger acidity compared to using impregnation method. Moreover, it was found that raising the hydrothermal temperature increased the crystallinity and enhanced more uniform incorporation of Ni atoms in the crystalline structure of catalysts. TPD-NH3 analysis demonstrated that high crystallization temperature and short crystallization time of NiZSM-5(350-0.5) resulted in fewer weak acid sites and medium acid strength. The MTO catalytic performance was tested in a fixed bed reactor at 460ºC and GHSV=10500 cm3 /gcat.h. A slightly different reaction pathway was proposed for the production of light olefins over impregnated Ni/ZSM-5 catalysts based on the role of NiO species. The enhanced methanol conversion for isomorphous substituted NiZSM-5 catalysts could be related to the most accessible active sites located inside the pores. Conclusion: The impregnated Ni/ZSM-5 catalyst prepared at low hydrothermal temperature showed the best catalytic performance, while the isomorphous substituted NiZSM-5 prepared at high temperature was found to be the active molecular sieve regarding the stability performance.

Role of the Structure and Electronic Properties of Fe2O3-MoO3 Catalyst on the Dehydration of Isopropyl Alcohol

1993 ◽  
Vol 58 (7) ◽  
pp. 1591-1599 ◽  
Author(s):  
Abd El-Aziz A. Said
Keyword(s):  
Active Sites ◽  
Isopropyl Alcohol ◽  
Oxide Catalyst ◽  
Flow System ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Catalyst Composition ◽  
Surface Active

Molybdenum oxide catalyst doped or mixed with (1 - 50) mole % Fe3+ ions were prepared. The structure of the original samples and the samples calcined at 400 °C were characterized using DTA, X-ray diffraction and IR spectra. Measurements of the electrical conductivity of calcined samples with and without isopropyl alcohol revealed that the conductance increases on increasing the content of Fe3+ ions up to 50 mole %. The activation energies of charge carriers were determined in presence and absence of the alcohol. The catalytic dehydration of isopropyl alcohol was carried out at 250 °C using a flow system. The results obtained showed that the doped or mixed catalysts are active and selective towards propene formation. However, the catalyst containing 40 mole % Fe3+ ions exhibited the highest activity and selectivity. Correlations were attempted to the catalyst composition with their electronic and catalytic properties. Probable mechanism for the dehydration process is proposed in terms of surface active sites.

Physicochemical and Catalytic Properties of Spinels Formed by Solid-Solid Interaction Between Fe2O3and V2O5

1996 ◽  
Vol 61 (8) ◽  
pp. 1131-1140 ◽  
Author(s):  
Abd El-Aziz Ahmed Said
Keyword(s):  
Vanadium Oxide ◽  
Active Sites ◽  
Catalyst Surface ◽  
Catalytic Properties ◽  
Flow System ◽  
Oxide Catalysts ◽  
X Ray Diffraction ◽  
Selective Catalyst ◽  
X Ray ◽  
Solid Catalysts

Vanadium oxide catalysts doped or mixed with 1-50 mole % Fe3+ ions were prepared. The structure of the original samples and those calcined from 200 up to 500 °C were characterized by TG, DTA, IR and X-ray diffraction. The SBET values and texture of the solid catalysts were investigated. The catalytic dehydration-dehydrogenation of isopropanol was carried out at 200 °C using a flow system. The results obtained showed an observable decrease in the activity of V2O5 on the addition of Fe3+ ions. Moreover, Fe2V4O13 is the more active and selective catalyst than FeVO4 spinels. The results were correlated with the active sites created on the catalyst surface.

scholarly journals A Superhydrophobic, Antibacterial, and Durable Surface of Poplar Wood

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1885
Author(s):  
Xinyu Wu ◽  
Feng Yang ◽  
Jian Gan ◽  
Zhangqian Kong ◽  
Yan Wu
Keyword(s):  
Stearic Acid ◽  
Antibacterial Properties ◽  
Alkali Resistance ◽  
Poplar Wood ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures ◽  
Acid And Alkali Resistance ◽  
The Stability

The silver particles were grown in situ on the surface of wood by the silver mirror method and modified with stearic acid to acquire a surface with superhydrophobic and antibacterial properties. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray energy spectroscopy (XPS) were used to analyze the reaction mechanism of the modification process. Scanning electron microscopy (SEM) and contact angle tests were used to characterize the wettability and surface morphology. A coating with a micro rough structure was successfully constructed by the modification of stearic acid, which imparted superhydrophobicity and antibacterial activity to poplar wood. The stability tests were performed to discuss the stability of its hydrophobic performance. The results showed that it has good mechanical properties, acid and alkali resistance, and UV stability. The durability tests demonstrated that the coating has the function of water resistance and fouling resistance and can maintain the stability of its hydrophobic properties under different temperatures of heat treatment.

scholarly journals Searching novel complex solid solution electrocatalysts in unconventional element combinations

Nano Research ◽  
2021 ◽  
Author(s):  
Olga A. Krysiak ◽  
Simon Schumacher ◽  
Alan Savan ◽  
Wolfgang Schuhmann ◽  
Alfred Ludwig ◽  
...  
Keyword(s):  
High Throughput ◽  
High Throughput Screening ◽  
Active Sites ◽  
Search Space ◽  
Reduction Reaction ◽  
Film Material ◽  
X Ray ◽  
High Entropy ◽  
Catalyst Composition ◽  
Scanning Transmission

AbstractDespite outstanding accomplishments in catalyst discovery, finding new, more efficient, environmentally neutral, and noble metal-free catalysts remains challenging and unsolved. Recently, complex solid solutions consisting of at least five different elements and often named as high-entropy alloys have emerged as a new class of electrocatalysts for a variety of reactions. The multicomponent combinations of elements facilitate tuning of active sites and catalytic properties. Predicting optimal catalyst composition remains difficult, making testing of a very high number of them indispensable. We present the high-throughput screening of the electrochemical activity of thin film material libraries prepared by combinatorial co-sputtering of metals which are commonly used in catalysis (Pd, Cu, Ni) combined with metals which are not commonly used in catalysis (Ti, Hf, Zr). Introducing unusual elements in the search space allows discovery of catalytic activity for hitherto unknown compositions. Material libraries with very similar composition spreads can show different activities vs. composition trends for different reactions. In order to address the inherent challenge of the huge combinatorial material space and the inability to predict active electrocatalyst compositions, we developed a high-throughput process based on co-sputtered material libraries, and performed high-throughput characterization using energy dispersive X-ray spectroscopy (EDS), scanning transmission electron microscopy (SEM), X-ray diffraction (XRD) and conductivity measurements followed by electrochemical screening by means of a scanning droplet cell. The results show surprising material compositions with increased activity for the oxygen reduction reaction and the hydrogen evolution reaction. Such data are important input data for future data-driven materials prediction.

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