scholarly journals Utilization of Sodium Hexametaphosphate for Separating Scheelite from Calcite and Fluorite Using an Anionic–Nonionic Collector

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 705 ◽  
Author(s):  
Jianhua Kang ◽  
Yuehua Hu ◽  
Wei Sun ◽  
Zhiyong Gao ◽  
Runqing Liu
Keyword(s):  
Photoelectron Spectroscopy ◽  
Negative Charge ◽  
Electrostatic Force ◽  
Sodium Hexametaphosphate ◽  
Infrared Spectrometry ◽  
Low Grade ◽  
X Ray ◽  
Charged Surfaces ◽  
Selective Reagent ◽  
Positively Charged

This study presents a highly selective reagent system that utilizes sodium hexametaphosphate (SHMP) to improve the separation of scheelite from calcite and fluorite using an anionic–nonionic collector. The recoveries of calcite and fluorite decreased to 20% as the SHMP dose exceeded 6 × 10−6 mol/L, whereas that of scheelite remained at 85%. The interaction mechanisms of minerals with SHMP were investigated through equilibrium speciation, Zeta potential, Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy analyses. SHMP exists as hydrogen phosphate anion in the aqueous solution with a pH of 7–12. Moreover, it may be adsorbed intensively on the positively charged surfaces of calcite and fluorite via electrostatic force or chelation with calcium ion to impede further adsorption of the assembled collector. By comparison, the adsorption of SHMP is feeble on the scheelite surface because of its negative charge. The roughing grade of low-grade scheelite ore is substantially improved from 0.74% to 1.65% compared with that in the contrast test in the absence of SHMP.

Thermally Induced Superlow Friction of DLC Films in Ambient Air

2018 ◽  
Vol 37 (8) ◽  
pp. 725-731 ◽  
Author(s):  
Qunfeng Zeng
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ambient Air ◽  
Friction Model ◽  
Repulsive Force ◽  
Hydroxyl Group ◽  
Thermally Induced ◽  
X Ray ◽  
Thermally Activated ◽  
Charged Interface ◽  
Positively Charged

AbstractThermally induced superlow friction (0.008) of diamond-like carbon (DLC) films was achieved in ambient air in the present work. Raman and XPS (X-ray Photoelectron Spectroscopy) measurements and analyses show that superlow friction of the annealed DLC films is involved in the transformation of sp3 to sp2 hybridized carbon during annealing and the tribochemical reactions during sliding. The thermally activated graphitization and oxidation of the annealed DLC films in ambient air is beneficial to form the positively charged interface and achieve the stable superlow friction. A friction model was developed and applied to explain superlow friction, which is attributed to Van de Waals force between graphite layers and the repulsive force between hydroxyl group of graphite oxide and hydrogen terminated DLC films surface.

scholarly journals Removal Efficiency and Mechanism of Cr(VI) from Aqueous Solution by Maize Straw Biochars Derived at Different Pyrolysis Temperatures

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 781 ◽  
Author(s):  
Wang ◽  
Zhang ◽  
Lv
Keyword(s):  
Aqueous Solution ◽  
Removal Efficiency ◽  
Photoelectron Spectroscopy ◽  
Low Cost ◽  
X Ray ◽  
Removal Capacity ◽  
Maize Straw ◽  
Efficient Adsorbent ◽  
Positively Charged ◽  
Maximum Removal

The removal efficiency and mechanism of Cr(VI) removal from aqueous solution on semi-decomposed maize straw biochars pyrolyzed at 300 to 600 °C were investigated. The removal of Cr(VI) by the biochars decreased with pyrolysis temperature increasing from 300 to 600 °C, and the maximum removal capacity of Cr(VI) for maize straw biochar pyrolyzed at 300 °C was 91 mg/g at pH 2.0. The percentage removal of Cr(VI) rapidly decreased with pH increasing from 2.0 to 8.0, with the maximum (>99.9%) at pH 2.0. The variation of Cr(VI) and Cr(III) concentrations in the solution after reaction showed that Cr(VI) concentration decreased while Cr(III) increased and the equilibrium was reached after 48 h, while the redox potential after reaction decreased due to Cr(VI) reduction. X-ray photoelectron spectroscopy (XPS) semi-quantitative analysis showed that Cr(III) accounted for 75.7% of the total Cr bound to maize straw biochar, which indicated reductive adsorption was responsible for Cr(VI) removal by the biochars. Cr(VI) was firstly adsorbed onto the positively charged biochar surface and reduced to Cr(III) by electrons provided by oxygen-containing functional groups (e.g., C=O), and subsequently part of the converted Cr(III) remained on the biochar surface and the rest released into solution. Fourier transform infrared (FTIR) data indicated the participation of C=O, Si–O, –CH2 and –CH3 groups in Cr(VI) removal by the biochars. This study showed that maize straw biochar pyrolyzed at 300 °C for 2 h was one low-cost and efficient adsorbent for Cr(VI) removal from aqueous solution.

Growth of Calcium Phosphate on Poled Piezoelectric Poly-L-lactic Acid Membrane by a Biomimetic Method

2007 ◽  
Vol 330-332 ◽  
pp. 703-706
Author(s):  
Chun Peng Huang ◽  
Dong Hua Guan ◽  
Kun Tian ◽  
Xin Min Chen ◽  
Lin Niu ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Electric Field ◽  
Photoelectron Spectroscopy ◽  
Charged Surface ◽  
X Ray ◽  
Charged Surfaces ◽  
Before And After ◽  
Dc Electric Field ◽  
Biomimetic Method

The bioactivity of poled piezoelectric PLLA membrane was investigated by studying the calcium phosphate formation in vitro using a biomimetic method. Samples (φ10mm) were poled under DC electric field of 8~l0kV/cm at 70°C for 30 min followed by cooling under the electric field. Surface chemistry of the samples before and after poling treatment was studied by X-ray photoelectron spectroscopy (XPS). Poled/unpoled samples were immersed in supersaturated calcification solution (SCS) for periods up to 24 h (36.5°C). The surface morphology and composition of the soaked samples were evaluated by using scanning electron microscope (SEM) and X-ray diffraction analysis (XRD). Poled samples showed two different charged surfaces, negatively-charged surface (N-PLLA) and positively-charged surface (P-PLLA). On the N-PLLA surfaces, SEM together with XRD showed a gradually formed calcium phosphate (Ca-P), while no obvious Ca-P on either P-PLLA or unpoled samples was observed. This study demonstrated that poled piezoelectric PLLA substrates induce substantially higher level of Ca-P formation than electrically neutral substrates and only N-PLLA, however, can improve Ca-P formation after immersion in SCS.

scholarly journals Structural, Surface Morphology and Optical Properties of ZnS Films by Chemical Bath Deposition at Various Zn/S Molar Ratios

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Fei-Peng Yu ◽  
Sin-Liang Ou ◽  
Pin-Chuan Yao ◽  
Bing-Rui Wu ◽  
Dong-Sing Wuu
Keyword(s):  
Chemical Bath Deposition ◽  
Photoelectron Spectroscopy ◽  
Visible Region ◽  
Film Surface ◽  
Optical Transmittance ◽  
Molar Ratio ◽  
Infrared Spectrometry ◽  
X Ray ◽  
Molar Ratios ◽  
Zns Films

In this study, ZnS thin films were prepared on glass substrates by chemical bath deposition at various Zn/S molar ratios from 1/50 to 1/150. The effects of Zn/S molar ratio in precursor on the characteristics of ZnS films were demonstrated by X-ray diffraction, scanning electron microscopy, optical transmittance, X-ray photoelectron spectroscopy, and Fourier transform infrared spectrometry. It was found that more voids were formed in the ZnS film prepared using the precursor with Zn/S molar ratio of 1/50, and the other ZnS films showed the denser structure as the molar ratio was decreased from 1/75 to 1/150. From the analyses of chemical bonding states, the ZnS phase was indeed formed in these films. Moreover, the ZnO and Zn(OH)2also appeared due to the water absorption on film surface during deposition. This would be helpful to the junction in cell device. With changing the Zn/S molar ratio from 1/75 to 1/150, the ZnS films demonstrate high transmittance of 75–88% in the visible region, indicating the films are potentially useful in photovoltaic applications.

scholarly journals Synthesis, Characterization and Catalytic Activity of UiO-66-NH2 in the Esterification of Levulinic Acid

Applied Nano ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 344-358
Author(s):  
Daiana A. Bravo Fuchineco ◽  
Angélica C. Heredia ◽  
Sandra M. Mendoza ◽  
Enrique Rodríguez-Castellón ◽  
Mónica E. Crivello
Keyword(s):  
Catalytic Activity ◽  
Photoelectron Spectroscopy ◽  
Levulinic Acid ◽  
Microwave Plasma ◽  
Raw Materials ◽  
Metal Organic Framework ◽  
Research Trend ◽  
Infrared Spectrometry ◽  
X Ray ◽  
Ethyl Levulinate

The massive use of petroleum and its possible exhaustion are driving the current research trend to study alternative raw materials from biomass for organic reactions. In this context, the present article presents a study of the catalytic esterification of levulinic acid, a platform molecule, with ethanol. Metal-organic framework (MOF) type compounds UiO-66-NH2 have been synthesized. Zirconium was incorporated, using zirconium chloride as a metal precursor, together with 2-aminoterephthalic acid as an organic binding agent. An alternative route of synthesis was proposed using more favorable conditions from an economic and environmental point of view, replacing dimethylformamide by 50 and 75% acetone as substitute solvent. The physicochemical properties of the materials were evaluated by X-ray diffraction (XRD), Infrared Spectrometry with Fourier Transform (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), microwave plasma atomic emission spectroscopy (MP-AES) and N2 adsorption to understand their morphology, crystalline, chemical and pore structure. The progress of the reaction was followed by gas chromatography and mass spectroscopy. The catalytic activity result of MOF25% in autoclave reactor, showed 100% of selectivity to ethyl levulinate and a turnover number (TON) of 66.18 moles of product/moles of Zr. This good catalytic performance obtained by partial solvent replacement in the synthetic material provides a more economical and eco-friendly process for ethyl levulinate generation.

scholarly journals Rapid Atmospheric Leaching of Chalcopyrite Using a Novel Reagent of Trichloroisocyanuric Acid

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1012
Author(s):  
Guobao Chen ◽  
Jiarui Sun ◽  
Hongying Yang ◽  
Pengcheng Ma ◽  
Shixiong Gao
Keyword(s):  
Photoelectron Spectroscopy ◽  
Cyanuric Acid ◽  
Passivation Layer ◽  
Composition Analysis ◽  
Copper Extraction ◽  
Low Grade ◽  
X Ray ◽  
Atmospheric Leaching ◽  
Leaching Reaction ◽  
Trichloroisocyanuric Acid

With the decrease in high-grade chalcopyrite resources, the copper extraction from low-grade chalcopyrite has attracted more and more attention. However, the kinetic rates of chalcopyrite leaching with traditional oxidants are usually very slow due to the formation of the passivation layer. In this study, a novel reagent of chlorinated oxidant, trichloroisocyanuric acid (TCCA), was used to leach chalcopyrite for the first time. The experimental results showed that when the initial oxidant concentration for TCCA was 0.054 mol·L−1, the leaching temperature was kept at 55 °C, and the pH of the pulp was controlled at 1, the oxidation efficiency of Cu can reach above 90% in less than 30 min. Various analyses of chalcopyrite mineral ore and its oxidized residues, such as chemical composition analysis, X-ray diffraction analysis, scanning electron microscopy analysis and X-ray photoelectron spectroscopy, were conducted, respectively. No obvious passivation layer was found on the chalcopyrite surface, though the sulfur product can also be generated during the leaching. Reaction kinetic analysis results showed that the different influence of surface reaction and diffusion process on the dissolution of chalcopyrite is little due to the fast leaching speed. After calculation, the activation energy of the whole leaching reaction is 9.06 kJ·mol−1, much lower than that in other reports. The mechanism was also proposed that TCCA was hydrolyzed in the solution to form hypochlorous acid, which is the strong oxidant, and cyanuric acid, which prevents the formation of a passivation layer. The processing in this study is expected to be applied as a novel method for atmospheric leaching of chalcopyrite.

Parallel Bias-Enhanced Sulfur-Assisted Chemical Vapor Deposition of Nanocrystalline Diamond Films

2003 ◽  
Vol 775 ◽  
Author(s):  
Joel De Jesùs ◽  
Juan A. Gonzàlez ◽  
Oscar O. Ortiz ◽  
Brad R. Weiner ◽  
Gerardo Morell
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Photoelectron Spectroscopy ◽  
Film Growth ◽  
Defect Density ◽  
Substrate Surface ◽  
Chemical Vapor ◽  
Nanocrystalline Diamond ◽  
X Ray ◽  
Positively Charged

AbstractThe transformations induced by the application of a continuous bias voltage parallel to the growing surface during the sulfur-assisted hot-filament chemical vapor deposition (HFCVD) of nanocrystalline diamond (n-D) films were investigated by Raman spectroscopy (RS), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The films were deposited on molybdenum substrates using CH4, H2 and H2S. Bias voltages in the range of 0 – 800 VDC were applied parallel to the substrate surface continuously during deposition. The study revealed a significant improvement in the films' density and a lowering in the defect density of the nanocrystalline diamond structure for parallel bias (PB) voltages above 400V. These high PB conditions cause the preferential removal of electrons from the gaseous environment, thus leading to the net accumulation of positive species in the volume above the growing film, which enhances the secondary nucleation. The nanoscale carbon nuclei self-assemble into carbon nano-clusters with diameters in the range of tens of nanometers, which contain diamond (sp3-bonded C) in their cores and graphitic (sp2-bonded C) enclosures. Hence, the observed improvement in film density and in atomic arrangement appears to be connected to the enhanced presence of positively charged ionic species, consistent with models which propose that positively charged carbon species are the crucial precursors for CVD diamond film growth.

Acceleration of Organic Contaminant Adsorption Onto Silicon Surfaces in the Presence of Residual Fluorine

1997 ◽  
Vol 477 ◽  
Author(s):  
Koichiro Saga ◽  
Takeshi Hattori
Keyword(s):  
Photoelectron Spectroscopy ◽  
Organic Contaminants ◽  
Surface Composition ◽  
Electrostatic Force ◽  
Silicon Wafers ◽  
Silicon Surfaces ◽  
Gas Chromatography Mass Spectrometry ◽  
Organic Contamination ◽  
X Ray ◽  
Polar Groups

ABSTRACTThe influence of fluorine atoms remaining after HF treatment on the adsorption of organic contaminants onto the surface of silicon wafers was investigated by analyzing the organic contaminants with gas chromatography-mass spectrometry following thermodesorption (TDGC/MS), and the surface composition with X-ray photoelectron spectroscopy (XPS). It has been found that residual fluorine on silicon surfaces after cleaning of the silicon wafers with either aqueous HF or anhydrous HF accelerates the adsorption of organic contamination onto the silicon surfaces. This would be due to the electrostatic force of attraction between the polar groups of organic compounds and the residual fluorine on the silicon surface.

Surface Charge of Bioactive Polyethylene Modified with –SO3H Groups and Its Apatite Inducing Capability in Simulated Body Fluid

2005 ◽  
Vol 284-286 ◽  
pp. 453-456 ◽  
Author(s):  
Isabel B. Leonor ◽  
Hyun Min Kim ◽  
Francisco Balas ◽  
Kawashita Masakazu ◽  
Rui L. Reis ◽  
...  
Keyword(s):  
Surface Potential ◽  
Photoelectron Spectroscopy ◽  
Calcium Sulphate ◽  
Initial Increase ◽  
Soaking Time ◽  
X Ray ◽  
Phosphate Ions ◽  
Subsequent Decrease ◽  
Surface Variation ◽  
Positively Charged

A bioactive polyethylene polymer substrate can be produced by incorporation of sulfonic functional groups (-SO3H ) on its surface. Variation of the surface potential of the polyethylene modified with -SO3H groups with soaking in SBF were investigated using a laser electrophoresis zeta-potential analyzer. To complement the study using the laser electrophoresis, the surface was examined by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with an attached energy dispersive electron probe X-ray analyser (FE-SEM/EDS). It was found that the surface potential of the polyethylene was highly negative charged after soaking in SBF for 0.5 h, increased for higher soaking times (up to 48 h), and then decreased. The negative charge of the polymer at soaking time of 0.5 h is attributed to the presence of –SO3H groups on the surface. The initial increase in the surface potential was attributed to the incorporation of positively charged calcium ions to form a calcium sulphate, and then the subsequent decrease was assigned to the incorporation of negatively charged phosphate ions to form an amorphous calcium phosphate, which eventually transformed into apatite.

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