scholarly journals Synthesis of nanostructured conducting polyaniline in the presence of 5-sulfosalicylic acid

2008 ◽  
Vol 62 (3) ◽  
pp. 107-113 ◽  
Author(s):  
Aleksandra Janosevic ◽  
Gordana Ciric-Marjanovic
Keyword(s):  
Molecular Structure ◽  
Oxidative Polymerization ◽  
Average Diameter ◽  
Polymerization Process ◽  
Molar Ratio ◽  
Sulfosalicylic Acid ◽  
Molar Ratios ◽  
Reaction Solution ◽  
Initial Ph ◽  
Constant Molar Ratio

Oxidative polymerizations of aniline with ammonium peroxydisulfate in aqueous solution of 5-sulfosalicylic acid (SSA), were performed at the constant molar ratio [oxidant]/[monomer] = 1.25, by using various initial molar ratios of SSA to aniline. It was shown that the ratio [SSA]/[aniline] has a crucial influence on the molecular structure, morphology, and conductivity of synthesized polyaniline5-sulfosalicylate (PANI-SSA), as well as on the yield and temperature profile i.e. the mechanism of polymerization process. The yield of PANI-SSA was 80 - 86% for [SSA]/[aniline] ratios in the range 0.25-1.0. Granular PANI-SSA was obtained by the oxidative polymerization of in situ formed anilinium 5-sulfosalicylate ([SSA]/[aniline] = 1.0). The initial induction period was followed by the rapid exothermic polymerization of aniline during the oxidation of anilinium 5-sulfosalicylate with peroxydisulfate. Nanostructured PANI-SSA was synthesized by the oxidation of the mixture of dianilinium 5-sulfosalicylate and aniline ([SSA]/[aniline] = 0.25), which proceeds in two exothermic phases well separated with an athermal period. The presence of nanocylinders (nanorods, possibly nanotubes), with the average diameter of 95-250 nm and the length of 0.5-1.0 ?m has been revealed by scanning electron microscopy. It was concluded that PANI nanocylinders are formed when reaction solution has the initial pH > 3.5. Electroconductivity of synthesized polyanilines was in the range 0.01-0.17 S cm-1, and it increases with increasing molar ratio of SSA to aniline. Molecular structure of synthesized polyanilines was investigated by FTIR spectroscopy. Besides the characteristic bands of standard PANI in emeraldine form (benzenoid, quinonoid, and semiquinonoid units), the band attributable to substituted phenazine structural units was observed at -1415 cm-1 in the FTIR spectrum of nanostructured PANI-SSA sample.

Precipitation and surface polymerizations of aniline at different aniline:oxidizer molar ratios

e-Polymers ◽  
2007 ◽  
Vol 7 (1) ◽  
Author(s):  
Lucia Helena Mascaro ◽  
Débora Gonçalves
Keyword(s):  
Oxidative Polymerization ◽  
Reaction Times ◽  
Ammonium Persulfate ◽  
Open Circuit ◽  
Polymerization Process ◽  
Pani Film ◽  
Electrode Surfaces ◽  
Molar Ratios ◽  
Pt Electrodes ◽  
Vis Spectroscopy

AbstractThe oxidative polymerization of aniline was monitored by means of open-circuit potential (OCP) measurements of Pt electrodes immersed in an aqueous acidic medium containing different aniline:oxidizer (ammonium persulfate) molar ratios. Thin polyaniline (PANI) films were formed on the Pt electrode surfaces during the OCP measurements, and they were studied by SEM and cyclic voltammetry in a monomer-free solution at different reaction times. A precipitate also obtained during the polymerization process was analyzed by UV-VIS spectroscopy in 1-methyl-2-pyrrolidinone. It is observed that aniline or short oligomeric species are necessary to initiate the growth of a PANI film, which takes place at the first few minutes of the reaction.

EFFECT OF IRON ON THE NATURE OF PRECIPITATION PRODUCTS OF ALUMINUM

1987 ◽  
Vol 67 (1) ◽  
pp. 135-145 ◽  
Author(s):  
TEE BOON GOH ◽  
M. J. DUDAS ◽  
S. PAWLUK ◽  
P. M. HUANG
Keyword(s):  
Molar Ratio ◽  
Ambient Conditions ◽  
Crystalline Materials ◽  
Molar Ratios ◽  
Iron Aluminum ◽  
Initial Ph ◽  
Oxide Phases ◽  
Key Words Iron ◽  
Rate Of Hydrolysis ◽  
Mixed Systems

Solutions Of AlCl3 (5 × 10−3 mol L−1) and FeCl2 were mixed and aged for 3 yr under ambient conditions at the initial pH of 7.0 and Fe:Al molar ratios of 0, 0.1, 0.3, 0.5 and ∞ (Fe at 5 × 10−3 mol L−1). Fe2+ was readily oxidized in this experiment so that only the mutual interaction between Fe3+ and Al3+ can be reported. The initial Fe:Al molar ratio was an important parameter in determining the rate and amount of hydrolysis and precipitation of Fe and Al. At Fe:Al molar ratios ≤ 0.3, hydrolysis was delayed when compared to that in pure Al suspensions. At higher ratios more acidity was produced by hydrolytic reactions. The acidity was contributed by both Al and Fe. The fractions of Fe and Al precipitated were greater at lower Fe:Al molar ratios. Aluminum and iron were mutually interfering cations during crystallization. In mixed systems, the fractions of crystalline materials were greatly reduced. Between the crystalline compounds, gibbsite was more abundant than bayerite and this evolution was governed by pH and the interference of Fe on the subsequent rate of hydrolysis and crystallization. Iron substitution was not evident in the crystalline Al(OH)3 polymorphs. Crystalline Fe oxides could not be detected even at the Fe: Al molar ratio of 0.1. Two discrete oxide phases were formed in the mixed Fe-Al systems consisting of crystalline Al(OH)3 and a mixed Fe-Al oxide of indeterminate composition. In the pure ferric suspension, maghemite was formed. The results presented are used to explain the distribution of aluminum hydroxide polymorphs in soil and the genesis of gibbsite and iron oxide containing horizons of Oxisols. Key words: Iron, aluminum, gibbsite, bayerite, maghemite, Fe-Al surface coatings

Optimization of Bioscorodite Crystallization for Treatment of As(III)-Bearing Wastewaters

2017 ◽  
Vol 262 ◽  
pp. 555-558 ◽  
Author(s):  
Masahito Tanaka ◽  
Tsuyoshi Hirajima ◽  
Keiko Sasaki ◽  
Naoko Okibe
Keyword(s):  
Molar Ratio ◽  
Seed Crystals ◽  
Molar Ratios ◽  
Initial Ph ◽  
Applicable Range ◽  
Acidianus Brierleyi ◽  
The Stability ◽  
Reaction Speed

Arsenic (As) is a major impurity contaminated in metal refinery wastewaters. To immobilize As ions, we have previously reported microbial scorodite (FeAsO4·2H2O) crystallization using the thermo-acidophilic iron-oxidizing archaeon, Acidianus brierleyi. In order to extend the applicable range of As (III)-bearing metal refinery wastewaters (especially for dilute As (III) concentrations of 250–1500 ppm), this study investigated the effect of several factors possibly affecting the bioscorodite crystallization efficiency; (i) [Fe (II)]ini/[As (III)]ini molar ratio at different target As (III) concentrations, (ii) initial pH, and (iii) seed scorodite with different morphologies. The [Fe (II)]ini/[As (III)]ini molar ratio strongly affected the bioscorodite crystallization efficiency at each target As (III) concentration. Whilst the [Fe (II)]ini/[As (III)]ini molar ratio of 1.4 was most effective at 500–1500 ppm As (III), the optimal molar ratios for treating more dilute concentrations (< 500 ppm) were shown to be relatively higher. However, further increasing the [Fe (II)]ini/[As (III)]ini molar ratio resulted in formation of unwanted potassium jarosite (KFe3(OH)6(SO4)2) together with scorodite. Lowering the initial pH from 1.5 to 1.2 resulted in earlier scorodite nucleation, but lesser overall As immobilization. Feeding chemical-and bio-scorodite seed crystals differently affected the reaction speed and the stability of newly-precipitated bioscorodite. The TCLP test indicated that scorodite formed on bioscorodite seeds is more stable than that formed on chemically-synthesized scorodite seeds.

Preparation of TiO2/CNTs Nanocomposite and its Photocatalytic Activity for Methyl Orange in Aqueous Solutions

2011 ◽  
Vol 130-134 ◽  
pp. 1539-1543
Author(s):  
Xuan Hui Zhang ◽  
Su Juan Hu ◽  
Shao Ping Tong ◽  
Yuan Cheng ◽  
Dan Chen ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Photocatalytic Activity ◽  
Methyl Orange ◽  
Aqueous Solutions ◽  
Average Diameter ◽  
Molar Ratio ◽  
Molar Ratios ◽  
Hydrolysis Method ◽  
Transmission Electron ◽  
Supernatant Liquid

TiO2/CNTs nanocomposites with different Ti/C molar ratios were prepared by a sol-hydrolysis method at 368 K, using titanium tetrachloride as a precursor and nitrified carbon nanotubes as a support. The crystal phase, morphology and microstructure of the sample were characterized by X-ray Diffraction (XRD) and High-Resolution Transmission Electron Microscope (HRTEM). The photocatalytic activity of the samples was performed by methyl orange in aqueous solutions under UV light.The supernatant liquid of methyl orange during degradation was determined by using an UV-vis spectrophotometer (UV-vis). XRD results show that the crystal phases of the sample are composed of carbon nanotubes, anatase and rutile. HRTEM results show that the average diameter of oval titania is about 4.2 nm, and it decorates on the surface of carbon nanotubes uniformly. UV-vis results show that the photocatalytic activity of the TiO2/CNTs nanocomposite with the optimum Ti/C molar ratio is much higher than that of P25. These results indicate that a synergistic effect exists between titania and carbon nanotubes in the nanocomposite.

One-pot Preparation of Cu2(OH)3NO3 Nanosheets and Cu(OH)2 Nanowires

2019 ◽  
Vol 9 (4) ◽  
pp. 467-471
Author(s):  
Wenzhe Zhang ◽  
Ailing Yang ◽  
Xichang Bao
Keyword(s):  
Crystal Structures ◽  
Monoclinic Phase ◽  
Orthorhombic Phase ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
One Pot ◽  
Molar Ratios ◽  
Transmission Electron ◽  
Reaction Solution ◽  
Cuo Nanosheets

Introduction: By using Cu(NO3)2 as precursor and polyvinylpyrrolidone (PVP) as surfactant, nanosheets of Cu2(OH)3NO3, nanowires of Cu(OH)2 or the mixture of the two were prepared under different molar ratios of OH− to Cu2+. Materials and Methods: The crystal structures and morphologies of the products were characterized by X-Ray Diffraction (XRD) and Transmission Electron Microscope (TEM). Results: When the molar ratio of OH− to Cu2+ in reaction solution is lower than 1.28, pure Cu2(OH)3NO3 nanosheets were obtained. The thickness of one piece of nanosheet is about 167 nm. The Cu2(OH)3NO3 nanosheets consists of two types of crystal structures, monoclinic phase and orthorhombic phase. With increase of the molar ratio of OH− to Cu2+, the monoclinic phase of Cu2(OH)3NO3 was transferred to the orthorhombic phase of Cu2(OH)3NO3. When the molar ratio of OH− to Cu2+ is within 1.28-2.24, the product is the mixture of Cu2(OH)3NO3 nanosheets and Cu(OH)2 nanowires. And when this molar ratio is higher than 2.24, only Cu(OH)2 nanowires were produced. The lengths and the diameters of the Cu(OH)2 nanowires are in the region of 50-250 nm and 10 nm, respectively. Conclusion: The reason of the Cu2(OH)3NO3 nanosheets changing into the Cu(OH)2 nanowires is that the OH− anions replace the NO3 − anions in the layered Cu2(OH)3NO3 nanosheets, which causes the rupture of hydrogen bonds connecting the adjacent layers. The Cu(OH)2 nanowires were not stable and found to become spindled CuO nanosheets in air at room temperature.

Coordination Behavior of tBu2PH towards [{Rh(μ-Cl)(coe)2}2] (coe = cis-cyclooctene): Crystal and Molecular Structure of [{Rh(μ-Cl)(tBu2PH)2}2]

2008 ◽  
Vol 63 (9) ◽  
pp. 1035-1039 ◽  
Author(s):  
Hans-Christian Böttcher ◽  
Peter Mayer
Keyword(s):  
Molecular Structure ◽  
Nmr Spectroscopy ◽  
Crystal And Molecular Structure ◽  
Molar Ratio ◽  
X Ray ◽  
X Ray Crystallography ◽  
Molar Ratios ◽  
H Nmr ◽  
Coordination Behavior ◽  
Independent Synthesis

The reaction of [{Rh(μ-Cl)(coe)2}2] (coe = cis-cyclooctene) with tBu2PH in different solvents in various molar ratios was investigated. Working with a molar ratio of Rh to P = 1 : 2 in heptane overnight afforded [{Rh(μ-Cl)(tBu2PH)2}2] (1) in nearly quantitative yield. Upon tuning the molar ratio (Rh/P) in the range from 1 : 2 to 1 : 0.5, 31P{1H} NMR spectroscopy indicated the formation of [(tBu2PH)2Rh(μ-Cl)2Rh(coe)2] (3) besides the complexes [{Rh(μ-Cl)(coe)(tBu2PH)}2] (cis, 2a; trans, 2b). The constitution of 3 was established by an independent synthesis mixing 1 with [{Rh(μ- Cl)(coe)2}2] or [{Rh(μ-Cl)(cod)}2] (cod = 1.4-cyclooctadiene), respectively, which also yielded [(tBu2PH)2Rh(μ-Cl)2Rh(cod)] (4). Single crystals of 1 have been analyzed by X-ray crystallography (monoclinic, Cc, Z = 8, a = 32.7375(3), b = 11.1294(1), c = 24.5134(3)Å ; β = 106.7228(4)◦; V = 8553.70(15) Å3; T = 200 (2) K).

scholarly journals (Ag)Pd-Fe3O4 Nanocomposites as Novel Catalysts for Methane Partial Oxidation at Low Temperature

Nanomaterials ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 988 ◽  
Author(s):  
Blanca Martínez-Navarro ◽  
Ruth Sanchis ◽  
Esther Asedegbega-Nieto ◽  
Benjamín Solsona ◽  
Francisco Ivars-Barceló
Keyword(s):  
Partial Oxidation ◽  
Value Added ◽  
Average Diameter ◽  
Reaction Rates ◽  
Molar Ratio ◽  
Methane Partial Oxidation ◽  
Load Range ◽  
Pd Catalysts ◽  
X Ray ◽  
Molar Ratios

Nanostructured composite materials based on noble mono-(Pd) or bi-metallic (Ag/Pd) particles supported on mixed iron oxides (II/III) with bulk magnetite structure (Fe3O4) have been developed in order to assess their potential for heterogeneous catalysis applications in methane partial oxidation. Advancing the direct transformation of methane into value-added chemicals is consensually accepted as the key to ensuring sustainable development in the forthcoming future. On the one hand, nanosized Fe3O4 particles with spherical morphology were synthesized by an aqueous-based reflux method employing different Fe (II)/Fe (III) molar ratios (2 or 4) and reflux temperatures (80, 95 or 110 °C). The solids obtained from a Fe (II)/Fe (III) nominal molar ratio of 4 showed higher specific surface areas which were also found to increase on lowering the reflux temperature. The starting 80 m2 g−1 was enhanced up to 140 m2 g−1 for the resulting optimized Fe3O4-based solid consisting of nanoparticles with a 15 nm average diameter. On the other hand, Pd or Pd-Ag were incorporated post-synthesis, by impregnation on the highest surface Fe3O4 nanostructured substrate, using 1–3 wt.% metal load range and maintaining a constant Pd:Ag ratio of 8:2 in the bimetallic sample. The prepared nanocomposite materials were investigated by different physicochemical techniques, such as X-ray diffraction, thermogravimetry (TG) in air or H2, as well as several compositions and structural aspects using field emission scanning and scanning transmission electron microscopy techniques coupled to energy-dispersive X-ray spectroscopy (EDS). Finally, the catalytic results from a preliminary reactivity study confirmed the potential of magnetite-supported (Ag)Pd catalysts for CH4 partial oxidation into formaldehyde, with low reaction rates, methane conversion starting at 200 °C, far below temperatures reported in the literature up to now; and very high selectivity to formaldehyde, above 95%, for Fe3O4 samples with 3 wt.% metal, either Pd or Pd-Ag.

Morphogenesis of Photo-Polymerized Dimethacrylate Networks, Kinetics of Curing and Viscoelastic Parameters

2016 ◽  
Vol 851 ◽  
pp. 207-214
Author(s):  
Zdeněk Bystřický ◽  
Josef Jancar
Keyword(s):  
Molecular Structure ◽  
Double Bond ◽  
Kinetic Data ◽  
Complex Modulus ◽  
Polymerization Process ◽  
Molar Ratio ◽  
Structure Evolution ◽  
Degradation Kinetic ◽  
Diffusion Controlled ◽  
Kinetics Of

The paper refers to the process of dimethacrylate networks morphogenesis. These stiff and highly cross-linked networks have been extensively used as a polymeric matrix of dental composites for decades. In the study, common co-monomer mixtures used in dental resin formulations were employed. This includes rigid aromatic base monomers, bisphenol A glycerolate dimethacrylate (Bis-GMA) and its ethoxylated alternative (Bis-EMA). Flexible aliphatic monomer, triethylene glycol dimethacrylate (TEGDMA), was used as the viscosity reducer. Kinetics of the polymerization process was studied regarding the structural differences and varying molar ratio of the co-monomers. Kinetic data provided the base for understanding the supra-molecular structure evolution. Consequently, an attempt to quantify the relationship between the resulting network morphology and complex viscoelastic moduli was made. Curing kinetics was studied using differential photo-calorimetry (DPC). Complex modulus was measured using dynamic-mechanical analysis (DMA). Thermal degradation kinetic data (TGA) were used in order to confirm the estimated morphology of cured networks. Reactivity of the monomer is derived from its molecular structure. The potential for non-covalent physical interactions along with monomer backbone rigidity significantly decrease polymerization rate and resulting double bond conversion. The diffusion-controlled kinetics dominates over the chemically controlled kinetics throughout most of the polymerization process. Dilution by the low viscous and flexible monomer shifts the diffusion-controlled kinetics to the later stages of the polymerization. However, the flexibility of the monomer backbone promotes the origination of structural heterogeneities, characterized by micro-gel domains formation. This is associated particularly with the anomalous pendant double bond reactivity and ineffective cross-linking.

scholarly journals Oxidation of aniline in the presence of phenolic acids

2010 ◽  
Vol 64 (3) ◽  
pp. 215-220 ◽  
Author(s):  
Aleksandra Janosevic ◽  
Gordana Ciric-Marjanovic
Keyword(s):  
Phenolic Acids ◽  
Ph Value ◽  
Polymerization Degree ◽  
Emeraldine Salt ◽  
Sulfosalicylic Acid ◽  
Molar Ratios ◽  
Ammonium Peroxydisulfate ◽  
Benzene Rings ◽  
Initial Ph ◽  
Anion Type

Aniline was oxidized with ammonium peroxydisulfate (APS) in aqueous solutions of various phenolic acids: 5-sulfosalicylic acid (SSA), 3,5-dinitrosalicylic acid (DNSA) and gallic acid (GA). Polymerizations were performed at the constant molar ratios [acid]/[aniline]=0.5 and [APS]/[aniline]=1.25. The conductivity of synthesized polyaniline (PANI) is affected by the dopant anion type and decreases in order: PANI-SSA > PANI-DNSA > PANI-GA, the last polymer being nonconducting. This decrease is in accordance with the increase of initial pH value of the reaction mixture. The differences in molecular structure of synthesized PANI have been revealed by FTIR spectroscopy. FTIR spectra of PANI-SSA and PANI-DNSA show typical features of PANI conductive emeraldine salt segments. On the contrary, FTIR spectrum of PANI-GA shows absence of bands typical for conducting PANI polaronic lattice, and indicates the higher oxidation state of this polymer than that of emeraldine, the presence of substituted phenazines as constitutional units, as well as significant content of monosubstituted benzene rings which reflects low polymerization degree and/or pronounced chain branching. The strong hydrogen bonding between GA and PANI can obstruct propagation of oligoanilines and formation of longer conducting PANI chains.

Efficient Micromixing for Continuous Biodiesel Production from Jatropha Oil

2018 ◽  
Vol 9 (1) ◽  
pp. 133-139
Author(s):  
Waleed S. Mohammed ◽  
Ahmed H. El-Shazly ◽  
Marwa F. Elkady ◽  
Masahiro Ohshima
Keyword(s):  
Methyl Esters ◽  
Continuous Process ◽  
Sol Gel ◽  
Average Diameter ◽  
Biodiesel Production ◽  
High Mass ◽  
Molar Ratio ◽  
Jatropha Oil ◽  
Energy Deficiency ◽  
Gel Preparation

Introduction: The utilization of biodiesel as an alternative fuel is turning out to be progressively famous these days because of worldwide energy deficiency. The enthusiasm for utilizing Jatropha as a non-edible oil feedstock is quickly developing. The performance of the base catalyzed methanolysis reaction could be improved by a continuous process through a microreactor in view of the high mass transfer coefficient of this technique. Materials & Methods: Nanozirconium tungstovanadate, which was synthetized using sol-gel preparation method, was utilized in a complementary step for biodiesel production process. The prepared material has an average diameter of 0.066 &µm. Results: First, the NaOH catalyzed methanolysis of Jatropha oil was investigated in a continuous microreactor, and the efficient mixing over different mixers and its impact on the biodiesel yield were studied under varied conditions. Second, the effect of adding the nanocatalyst as a second stage was investigated. Conclusion: The maximum percentage of produced methyl esters from Jatropha oil was 98.1% using a methanol/Jatropha oil molar ratio of 11 within 94 s using 1% NaOH at 60 &°C. The same maximum conversion ratio was recorded with the nanocatalyst via only 0.3% NaOH.

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