Hydrothermal Synthesis and Electrochemical Properties of Layered Vanadates

1998 ◽  
Vol 548 ◽  
Author(s):  
J. Livage ◽  
L. Boujhedja ◽  
S. Castro-Garcia ◽  
C. Julien
Keyword(s):  
Aqueous Solutions ◽  
Electrochemical Properties ◽  
Diffusion Processes ◽  
Mixed Valence ◽  
Layered Structures ◽  
Point Of Zero Charge ◽  
Organic Cations ◽  
Oh Groups ◽  
Molecular Precursors ◽  
Ph Range

ABSTRACTThe synthesis of vanadates from aqueous solutions leads to a large variety of crystalline materials. The nature of molecular precursors mainly depends on pH and three different pH ranges can be distinguished. Cationic precursors are formed at low pH. Precipitation is obtained via the addition of anions leading to materials in which [VO6] octahedra are linked through anions. V2O5,nH2O gels are formed around the Point of Zero Charge (pH=2). They are made of ribbon-like particles and exhibit interesting properties as cathodic materials. Electrochemical properties depend on the drying procedure. Moreover, intercalation reactions lead to a whole range of new inorganic and organic bronzes. Chain metavanadates are precipitated from anionic precursors in basic aqueous solutions. Vanadium coordination decreases and they are made of corner sharing [VO4] tetrahedra. Layered structures are formed in the pH range where negatively charged species such as [VO(OH)4(OH2)]− should behave as precursors. Condensation occurs via V-OH groups in the equatorial plane leading to layered structures in which cations are inserted between the vanadate planes. Some reduction occurs when organic cations such as tetramethyl ammonium [N(CH3)4]+ are used leading to mixed valence vanadates. Electron delocalization is observed in these compounds but Li insertion is hindered by large organic cations. Better electrochemical properties are observed with smaller inorganic cations. Fibrous crystals of NaV3O8,H2O are formed in the presence of NaOH whereas the mixed valence bronze α'-NaxV2O5 is obtained when both NaOH and TMAOH react with V2O5. This fibrous morphology appears to improve diffusion processes at the electrode-electrolyte interface.

scholarly journals Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

2014 ◽  
Vol 13 (1) ◽  
Author(s):  
Dariusz Wyrzykowski ◽  
Joanna Pranczk ◽  
Dagmara Jacewicz ◽  
Aleksandra Tesmar ◽  
Bogusław Pilarski ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Substitution Reactions ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Hydroxo Complexes ◽  
Binary Complexes ◽  
Vis Spectroscopy ◽  
Potentiometric Titration Method ◽  
The Stability ◽  
Ph Range

AbstractA potentiometric titration method (PT) and a stopped-flow kinetic technique monitored by a UV−Vis spectroscopy have been used to characterize the stability of series of Co(II)- and Ni(II)-thiodiacetato complexes, M(TDA), in the presence of 1,10-phenanthroline (phen) or 2,2’-bipyridine (bipy) in aqueous solutions. The stability constants of the binary (1:1), ternary (1:1:1) as well as the resulting hydroxo complexes were evaluated and compared to the corresponding oxydiacetate complexes. Based on the species distribution as a function of pH the relative predominance of the species in the system over a pH range was discussed. Furthermore, the kinetic measurements of the substitution reactions of the aqua ligands to phen or bipy in the coordination sphere of the binary complexes M(TDA) were performed in the 288–303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (0.2–0.5 mM). The kinetic stability of the M(TDA) complexes was discussed in relation to the experimental conditions and the kind of the auxiliary ligands (phen/bipy). Moreover, the influence of the type of primary ligand (thiodiacetate/oxydiacetate) on the substitution rate of the auxiliary ligands was also compared.

Chemilumineszenz der SO2-Oxidation / Chemiluminescence of SO2-Oxidation

1978 ◽  
Vol 33 (3) ◽  
pp. 293-299 ◽  
Author(s):  
Joachim Stauff ◽  
Wolfgang Jaeschke
Keyword(s):  
Aqueous Solutions ◽  
Spectral Region ◽  
Time Course ◽  
Light Emission ◽  
Analog Computer ◽  
Reaction Scheme ◽  
So2 Oxidation ◽  
Recombination Product ◽  
Electronically Excited ◽  
Ph Range

Abstract The reactions of diluted aqueous solutions of SO2 resp. HSO3-ions with MnO4-or Ce4+ ions in the pH range 1-4 produce chemiluminescence in the spectral region of 450-600 nm. Measurements of the time course of the light emission and their simulation on an analog computer led to a reaction scheme in which a recombination product of primarily formed HSO3 radicals -of a lifetime of about 1 second -appears as precursor of electronically excited SO2 molecules. The participation of singlet oxygen can be excluded because at least the reaction with Ce4+ ions proceeds also in the absence of oxygen.

Adsorption of Benzene from Aqueous Solution Using Base Modified Expanded Perlite

2012 ◽  
Vol 622-623 ◽  
pp. 1779-1783
Author(s):  
Richard Appiah-Ntiamoah ◽  
Xuan Thang Mai ◽  
Francis W.Y. Momade ◽  
Hern Kim
Keyword(s):  
Zeta Potential ◽  
Adsorption Capacity ◽  
Linear Regression Analysis ◽  
Basic Medium ◽  
Maximum Adsorption Capacity ◽  
Hydroxyl Groups ◽  
Expanded Perlite ◽  
Oh Groups ◽  
Base Solution ◽  
Ph Range

In this study, the adsorption capacity of expanded perlite (EP) for benzene at low concentrations in water was investigated after EP was treated with sodium hydroxide (NaOH). IR spectra used to characterize the modified EP showed that there was no bonding between NaOH and the hydroxyl groups on the surface of EP. However, the NaOH provided a basic medium for negatively charged surface oxide ions (-SO-) to form on EP. This fact was corroborated by pH readings of the modification solution. This reduced in pH from 10 to 9 at the end of the reaction which indicated that the hydroxyl OH- groups on the EP underwent deprotonation and hence releases H+ into the solution, and also positive sites on EP adsorbed OH- ions from the base solution. Mahir et al. in their paper Zeta potential of unexpanded and expanded perlite samples in various electrolyte media confirmed that EP has no isoelectric point and exhibits negative zeta potential in the pH range of 2-11. The surface oxides (-SO-) were believed to have given EP it adsorptive potential. Adsorption isotherm values correlated reasonably well with the Langmuir isotherm model and it parameters (qo and K) were obtained using linear regression analysis. A maximum adsorption capacity (qo) value of 19.42 mg/g was achieved.

Construction of a pH-sensitive self-assembly in aqueous solutions based on a dansyl-modified β-cyclodextrin

Soft Matter ◽  
2021 ◽  
Author(s):  
Bing Jiang ◽  
Yu Liu ◽  
Linlin Zhao ◽  
Li Zhao ◽  
Ce Wang ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Self Assembly ◽  
Ph Sensitive ◽  
Ph Responsive ◽  
Ph Range

Here we present a pH-responsive self-assembly based on a β-cyclodextrin (β-CD) derivative bearing a dansyl terminus (βCD-C6-Dns). Vesicular structures were formed over the entire studied pH range (8.5-0.7); however, the...

scholarly journals Synthesis characterization and sorption properties of a sorbent synthesized using slag and red mud: Arsenic removal from spiked aqueous solutions

2016 ◽  
Vol 18 (2) ◽  
pp. 339-347 ◽  
Keyword(s):  
Aqueous Solutions ◽  
Red Mud ◽  
Arsenic Removal ◽  
Point Of Zero Charge ◽  
Maximum Adsorption Capacity ◽  
X Ray Diffraction ◽  
Equilibrium Studies ◽  
Metallurgical Wastes ◽  
Bet Method ◽  
Gf Aas

<p>The aim of the present study was to synthesize a sorbent, for arsenic removal from aqueous solutions, reusing two waste materials (slag and red mud). The sorbent was prepared after chemical and thermal treatment, during which amorphous silica sol and FeOOH sol were produced simultaneously and form Fe-Si complexes on the surface of the slag. To characterize the sorbent Powder X-ray diffraction (XRD); Fourier transform infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM-EDX) were applied. The surface area (BET method) and the Point of Zero Charge (PZC) of the sorbent were determined.). The sorption efficiency of the sorbent produced was investigated with kinetic and equilibrium studies, performed in batch conditions. The concentration of arsenic in solutions was determined by electro thermal atomic absorption spectroscopy (GF-AAS). The results of the study showed that with the described process, using metallurgical wastes, iron oxyhydroxides were &ldquo;loaded&rdquo; onto slag producing an effective sorbent for arsenic removal. Kinetic experiments proved that equilibrium was achieved within 15 hours, while the maximum adsorption capacity as evidenced by equilibrium experiments, was 16.14 mg g<sup>-1</sup>. Data proved to fit better to the Langmuir equation.</p>

scholarly journals Ultrasonic irradiation of chemical compounds in aqueous solutions

1992 ◽  
Author(s):  
Αναστασία Κοτρωναρου
Keyword(s):  
Aqueous Solutions ◽  
Ultrasonic Irradiation ◽  
Energy Utilization ◽  
Oxidation Products ◽  
Utilization Efficiency ◽  
Interfacial Region ◽  
Reaction Products ◽  
Operation Conditions ◽  
Cavitation Bubbles ◽  
Ph Range

The ultrasonic irradiation of para-nitrophenol, S(-II), and parathion is studied in aqueous solutions at 20 kHz and ~ 75 W-cnT2. Para-nitrophenol was degraded primarily by denitration and secondarily by ΌΗ radical attack to yield N 02, NO3, benzoquinone, hydroquinone, 4-nitrocatechol, formate and oxalate. These reaction products and the kinetic observations are consistent with a model involving high-temperature reactions of p-nitrophenol in the interfa.cia.1 region of cavitation bubbles. The average effective temperature of the interfacial region surrounding the cavitation bubbles was estimated to be T ~ 800 K. Ultrasonic irradiation of S(-II) is studied in aqueous solutions over the pH range 7 - 12. The reaction of HS“ with OH is the principal pathway for theoxidation of S(-II) at pH > 10; the oxidation products are SO2“, SO2", and S20 Upon prolonged sonication, SO2" is the only observed product. At pH < 8.5, thermal decomposition of H2S within or near collapsing cavitation bubbles becomes the important pathway and elemental sulfur is found as an additional product of the sonolysis of S(-II). The sonolytic oxidation of H2S at pH > 10 was successfully modeled with an aqueous-phase free-radical chemistry mechanism and assumingcontinuous and uniform ΌΗ input into solution from the imploding cavitation bubbles. Parathion degradation occurred primarily by enhanced hydrolysis and secondarily by direct ΌΗ radical attack.The effect of various physical and chemical parameters on sonolytic yields is examined. The observed effects are in qualitative agreement with the sonolysis mechanisms proposed for the chemicals of interest and the existing hydrodynamic theories of acoustic cavitation. The formation of iodine upon ultrasonic irradiation of potassium iodide solutions and the sonolysis of S(-II) are used as probes to compare the sonochemical efficiency of different experimental set-ups. This work elucidates the mechanisms of the ultrasonic decomposition of typical organic and inorganic pollutants. It is shown that ultrasound has the potential to become a viable alternative for the destruction of chemical contaminants in water and wastewater. The current limitation of sonolysis is its low energy utilization efficiency, but there is room for improvement by optimizing reactor design and physical/chemical operation conditions. This work offers some recommendations and insight in that respect.

scholarly journals Removal of Methylene Blue from Aqueous Solutions by Using Nance (Byrsonima crassifolia) Seeds and Peels as Natural Biosorbents

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Lorena Robles-Melchor ◽  
Maribel Cornejo-Mazón ◽  
Diana Maylet Hernández-Martínez ◽  
Gustavo F. Gutiérrez-López ◽  
Santiago García-Pinilla ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Aqueous Solutions ◽  
Driving Forces ◽  
Physical Adsorption ◽  
Point Of Zero Charge ◽  
Transfer Coefficients ◽  
Fractal Structures ◽  
Free Energy Of Adsorption ◽  
Freundlich Isotherms ◽  
Byrsonima Crassifolia

Contamination of effluents with chemicals is a serious problem that impacts human health. Methylene blue is a cationic dye found frequently in industrial and urban sewages. In this work, dried grinded seeds and peels of nance were used as biosorbents in aqueous solutions at pH 7 and 10 (simulating urban and textile effluents) finding that Langmuir and Freundlich isotherms adequately described the sorption. Adsorption efficiencies were larger than 98% in all cases and slightly lower at pH 7 due to the closeness with the point of zero charge (pzc) of seeds and peels of nance (5.96 and 3.42, respectively). In all cases, Langmuir adsorption was favorable (RLa < 1), and Gibbs free energy of adsorption was negative indicating spontaneity, and since these values were larger than −80 but lower than 0 kJ/mol, the MB removal process was mainly due to physical interactions, a characteristic of physical adsorption. No significant differences were found amongst bulk mass transfer coefficients for the adsorption of both sorbents, indicating that both bioadsorbents had the same hydrodynamic and driving forces as well as depicted similar MB-adsorbent affinities. Interaction of MB with adsorbents was corroborated by FTIR spectroscopy, and the sorption was evidenced by scanning electron microscopy and image analysis which indicated that both adsorbents had fractal structures.

Electrochemical properties of aqueous solutions of fullerenol-d

2011 ◽  
Vol 84 (1) ◽  
pp. 79-83 ◽  
Author(s):  
K. N. Semenov ◽  
D. G. Letenko ◽  
N. A. Charykov ◽  
V. A. Nikitin ◽  
M. Yu. Matuzenko ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Electrochemical Properties
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