6H2O Solution Research Articles

Preparation of NiO/TiO2 Composite Films for Enhanced Dye Sensitized Solar Cell Efficiency

Abstract Spray pyrolysis technique has been applied for preparing many kinds of thin films because this technique offers a lot of advantages, such as inexpensive cost, uncomplicated process and large scale production. Therefore, the spray pyrolysis technique is used for making pure TiO2 and NiO/TiO2 composite films in this report. A NiO/TiO2 composite film is getting attention to be used as a compact layer in dye sensitized solar cell (DSSC) because NiO can be used as a hole collector and a barrier for energy recombination properties. Moreover, the NiO/TiO2 composite film exhibits superhydrophilic properties that can increase absorption efficiency for a dye solution. This study has an objective to improve the efficiency of DSSC by changing the ratio of NiO/TiO2 in the composite films. The pure TiO2 and NiO/TiO2 composite films were prepared at 200℃ by spray pyrolysis technique using a Ti(OCH(CH3)2)4 solution and a mixture of Ti(OCH(CH3)2)4 solution with Ni(NO3)2•6H2O powder, respectively. The effect of the ratio between Ni(NO3)2•6H2O powder and Ti(OCH(CH3)2)4 solution (0.5 atm%, 1 atm%, 2 atm%, and 4 atm% of Ni(NO3)2•6H2O) on the efficiency of DSSCs were studied. The surface morphology, crystal structure and optical properties of TiO2 and NiO/TiO2 composite films on FTO and glass substrates were characterized by using field-emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), and UV-VIS spectrophotometer, respectively. The FE – SEM images showed that the films were smooth surface and dense when prepared at 200 ℃. The XRD results of TiO2 and NiO/TiO2 composite films on the FTO substrates showed that the TiO2 crystals were anatase phase because the peak at 25.30 corresponds to (101) planes of anatase. The spectrophotometer results showed that the optical transmittance for all samples were about 80%. For the energy conversion efficiency characterization, it was found that the NiO/TiO2 composite films that were prepared from 0.5 atm% of Ni(NO3)2•6H2O solution had the better energy conversion efficiency than TiO2 films.

Magnetic amendment material based on bio-char from edible oil industry waste. Its performance on aromatic pollutant removal from water

Bio-chars produced from the pyrolysis of sunflower seed hulls are investigated in the context of adding value to edible oil industry waste. Magnetic bio-chars are obtained to employ them for the aqueous adsorption of guaiacol, which is a model molecule of pollutants in water. Two magnetization methods are followed to get a series of magnetic bio-chars, one based on the pyrolysis of sunflower seed hulls previously washed with FeCl3·6H2O solutions (MBFs) and the other one consisting of magnetization of the bio-char obtained from the pyrolysis of the hulls pretreated with ZnCl2 (MBZ). A full characterization of the samples is carried out by Scanning Electronic Microscopy (SEM), X-Ray Diffraction (XRD), Atomic Absorption (AA), Fourier Transformed Infrared spectroscopy (FTIR), and N2 sorptometry. Selected magnetic bio-chars are tested for the adsorption of guaiacol in water with four models: Langmuir, Freundlich, Sips and Temkin. The best performance is assigned to the sample MBF5 containing 15.2 Fe %wt. with a maximum adsorption capacity of 48.49 mg/g and a heterogeneous surface according to Sips model. Temkin model predicts physisorption as guaiacol surface interaction presenting a b parameter of 15.87 J/mol.

Removal of Tetracycline by Hydrous Ferric Oxide: Adsorption Kinetics, Isotherms, and Mechanism.

The removal of tetracycline (TC) from solution is an important environmental issue. Here we prepared an adsorbent hydrous ferric oxide (HFO) by adjusting a FeCl3·6H2O solution to neutral pH. HFO was characterized by a surface area analyzer, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), and was used to remove TC from solution. The influence of pH, solid-to-liquid ratio, ionic type, and strength on TC removal was investigated. Adsorption kinetics and isotherms were also determined. HFO after adsorption of TC was analyzed by FTIR and XPS to investigate the adsorption mechanism. The results showed that the adsorption of TC increased from 88.3% to 95% with increasing pH (3.0–7.0) and then decreased. K+ ions had little effect on TC adsorption by HFO. However, Ca2+ and Mg2+ reduced the adsorption of TC on HFO. When the concentrations of Ca2+ and Mg2+ were increased, the inhibitory effect was more obvious. Pseudo-second-order kinetics and the Langmuir model fitted the adsorption process well. The maximum adsorption capacity of TC on HFO reached 99.49 mg·g−1. The adsorption process was spontaneous, endothermic, and increasingly disordered. Combination analysis with FTIR and XPS showed that the mechanism between TC and HFO involved electrostatic interactions, hydrogen interactions, and complexation. Therefore, the environmental behavior of TC could be affected by HFO.

Porous mullite ceramics with enhanced mechanical properties prepared by SLS using MnO2 and phenolic resin coated double-shell powders

Novel double-shell mullite powders with good flowability and formability for selective laser sintering (SLS) were prepared for the fabrication of porous mullite ceramics with enhanced mechanical properties. The inner MnO2 shell was prepared by the co-precipitation reaction between MnC4H6O4·4H2O (Mn(Ac)2·4H2O) and KMnO4, and the outer phenolic resin shell was obtained via the solvent evaporation method. The influence of Mn(Ac)2·4H2O solution content on phase composition, microstructure, pore size distribution and mechanical properties of porous mullitie ceramics was investigated. With increasing Mn(Ac)2·4H2O content from 0 to 48 mL, the compressive strength and fracture toughness of porous mullite ceramics increased from 0.8 ± 0.1 MPa to 22.1 ± 1.0 MPa and from 0.03 ± 0.01 MPa m1/2 to 0.53 ± 0.01 MPa m1/2, respectively. It was found from TEM analysis that the remarkable mechanical property enhancement was attributed to the pinning effect of the presence of MnO2 sintering additive precipitated between the interwoven mullite grains. Correspondingly, the shrinkage increased sharply from 5.27 ± 1.3% to 23.5 ± 1.4%, while the open porosity decreased dramatically from 64.1 ± 0.6% to 48.7 ± 1.2% with the gradual reduction of open pore size distribution from 17.25 to 11.33 μm. Finally, the honeycomb mullite ceramics with very complex shapes of intersecting pore tunnels were successfully prepared by SLS. This paper provide a novel and feasible route to dramatically improve the mechanical properties of SLS-formed porous ceramic products.

Enhancing catalysis activity of La0.6Sr0.4Co0.8Fe0.2O3-δ cathode for solid oxide fuel cell by a facile and efficient impregnation process

Abstract The development of high performance electrocatalysts to promote oxygen reduction reaction (ORR) and to prolong the durability of cathodes of solid oxide fuel cell is essential at intermediate or low temperatures. Here, we report a facile and efficient spray impregnation strategy in enhancing catalytic activity of La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF) due to the introduction of a multitude of homogeneous nanoparticles. With a highly active surface abundance in B-site cations, the modified LSCF cathode manifests an area-specific resistance (ASR) of ∼0.140 Ω cm2, only a fifth of that for a pristine LSCF cathode (∼0.764 Ω cm2) at 600 °C, and anode-supported fuel cells with the decorated LSCF cathode show markedly improved peak power densities (∼0.94 W cm−2 at 700 °C). Furthermore, the ORR kinetics of the modified LSCF cathode can be further enhanced by impregnating Ni(NO3)2·6H2O and Co(NO3)2·6H2O solution again. X-ray photoelectron spectroscopy analysis indicates that the homogeneous nanoparticles alter the distribution of Srsurface and Osurface. It is found that ‘Co’ decoration can effectively alleviate the surface aggregation of Sr and ‘Co’ and ‘Ni’ decoration play a pivotal role in the reactivation of electrode surface.

Use of CeO₂ Nanoparticles to Enhance UV-Shielding of Transparent Regenerated Cellulose Films.

The major challenge in preparing polymer nanocomposites is to prevent the agglomeration of inorganic nanoparticles (NPs). Here, with regenerated cellulose (RC) films as supporting medium, UV-shielding and transparent nanocomposite films with hydrophobicity were fabricated by in situ synthesis of CeO2 NPs. Facilitated through the interaction between organic and inorganic components revealed by X-ray diffraction (XRD) and Fourier transformation infrared spectroscopy (FTIR) characterization, it was found that CeO2 NPs were uniformly dispersed in and immobilized by a cellulose matrix. However some agglomeration of CeO2 NPs occurred at higher precursor concentrations. These results suggest that the morphology and particle size of CeO2 and the corresponding performance of the resulting films are affected by the porous RC films and the concentrations of Ce(NO3)3·6H2O solutions. The optimized nanocomposite film containing 2.95 wt% CeO2 NPs had more than 75% light transmittance (550 nm), high UV shielding properties, and a certain hydrophobicity.

Crystal-Chemical Features and Sorption Properties of Natural and Synthetic Smectites

Sorption of uranyl ions from uranyl nitrate UO2(NO3)2 · 6H2O solutions by natural and synthetic layered silicates was studied by X-ray diffraction, IR spectroscopy, and high-resolution inductively coupled plasma mass spectrometry. The modifications of some structural parameters of the studied species after they were reacted with uranyl ions are due to a partial incorporation of uranyls into the interlayer spaces of the smectite structure, or the rotation of the tetrahedra of a tetrahedral network and the distortion of octahedra in an octahedral layer. The natural bottom clay samples from the Pacific Ocean and the Sea of Okhotsk have the best sorption properties. This is due to structural defects and the formation of uranium complexes with the iron ions of the smectite structure. Iron present in clay minerals improves their sorption potentials.

Effect of surface treatments on the localized corrosion resistance of the AA2198‐T8 aluminum lithium alloy welded by FSW process

In this work, the effect of eight types of surface treatments on the corrosion resistance of friction stir welded samples of an AA2198‐T8 Al‐Cu‐Li alloy were tested and compared in an attempt to find suitable alternatives to toxic and carcinogenic hexavalent chromium treatments. All the samples were anodized and subjected to different post‐anodizing treatments. The post‐anodizing treatments were (1) hydrothermal treatment in Ce (NO3)3 6H2O solution; (2) hydrothermal treatment in Ce (NO3)3 6H2O solution with H2O2; (3) hydrothermal treatment in boiling water; (4) hexavalent chromium conversion coating; and (5) immersion in BTSE (bis‐1,2‐(triethoxysilyl) ethane. The corrosion resistance of the treated samples was evaluated by immersion tests in sodium chloride solution (0.1 mol L−1 NaCl) and electrochemical impedance spectroscopy (EIS) of the friction stir weldment. The results showed that among the alternative treatments, the Ce‐containing solutions presented the best corrosion resistance, especially when used without peroxide.

Effect of concentration of Ce(NO3)3 · 6H2O and temperature on the corrosion resistance of Al2O3/cerium oxide composite films on 1060 Al alloy

In this paper, Al2O3/cerium oxide composite films were prepared on the surface of aluminum by anodic oxidation and chemical solution deposition. The aluminum was firstly anodized in sulfuric acid, then treated with different concentrations of Ce(NO3)3 · 6H2O solution at different temperatures. X‐ray diffraction (XRD), energy dispersive spectrometer (EDS), scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), and electrochemical polarization tests were used to characterize the properties of the composite films. The results indicate that the Al2O3/cerium oxide composite films successfully form on 1060 Al alloy, and the best condition of film‐forming is 2 g/L Ce(NO3)3 · 6H2O and 50 °C. Al2O3/cerium oxide composite film under this condition has a uniform, smooth, and pyknotic surface topography and optimal corrosion resistance. The corrosion density at that time is 1.106 × 10−6 A/cm2 and the corrosion potential is −0.458 V.

Development of new approaches to the study of pitting corrosion resistance of stainless steels obtained by selective laser melting

This paper presents the results of comparative corrosion resistance studies of stainless steels manufactured by selective laser melting (SLM) in the initial state with subsequent heat treatment and machining. Pitting corrosion tests are carried out, according to ASTM G48 method A in 10% FeCl3·6H2O solution at elevated temperature and exposure time for 5h. The studies were performed on the AISI 321 and AISI 316L stainless steels manufactured by SLM. It was obtained that laser scanning speed decrease led to density rise by other SLM parameters being equal. Porosity affected to the stainless steel corrosion behaviour significant. Metal density decrease resulted to corrosion rate rise. Microstructure examination showed that pitting corrosion development depended on surface steel condition.

Corrosion and Cavitation Resistance of High-Strength Austenitic Nitrogen Stainless Steels in Seawater

Abstract—The corrosion and cavitation resistance of high-strength economically alloyed nitrogen-bearing chromium–nickel–manganese austenitic C10Cr19Mn10Ni6Mo2N and C09Cr19Mn10Ni6Mo2Cu2N stainless steels in seawater is compared experimentally with the properties of chromium–nickel C04Cr18Ni9 and C04Cr18Ni9N steels. The resistance to pitting corrosion is tested by a chemical method in a 100-g/L FeCl3 · 6H2O solution. The overall corrosion resistance is assessed by tests in synthetic seawater (3% NaCl). The cavitation resistance in seawater is tested by means of a high-intensity cavitation system based on a Hielscher Ultrasonic UIP 1000hd ultrasound unit in 3% aqueous NaCl solution (vibration frequency 20 kHz, power 1000 W, amplitude 25 μm) for 8–36 h. After cavitation treatment, the damage and change in microhardness at the sample surface is estimated, as well as the change in phase composition and mass of the samples in the tests. According to the tests, C10Cr19Mn10Ni6Mo2N and C09Cr19Mn10Ni6Mo2Cu2N steels are free of pits after exposure to seawater and iron-chloride solution. The overall corrosion rate is lower than for chromonickel Cr18Ni9 steel. Ultrasonic cavitation may lead not only to surface damage by erosion and intensification of local corrosion but also to change in the physical and mechanical properties on account of cold working and phase transformations. The resistance to ultrasonic cavitation in seawater is greater for C10Cr19Mn10Ni6Mo2N and C09Cr19Mn10Ni6Mo2Cu2N steels, containing thermally and mechanically stable austenite, than for chromonickel steels, especially C04Cr18Ni9, which is weaker and less stable. For example, after 36-h cavitational treatment in seawater, significant changes in state are seen in C04Cr18Ni9 and C04Cr18Ni9N steels: considerable damage (etching) and hardening of the surface and also the formation of a small quantity of martensite in C04Cr18Ni9 steel. For C10Cr19Mn10Ni6Mo2N and C09Cr19Mn10Ni6Mo2Cu2N steels, the tests indicate only slight change in state of the surface and hardening.

Comparative study of immobilization and mechanical properties of sulfoaluminate cement and ordinary Portland cement with different heavy metals

There have been limited studies on the hardening of cement containing different heavy metals owing to differences in solidification effect. The leachability, setting time, and compressive strength of sulfoaluminate cement (CSA) and ordinary Portland cement (OPC) mixed with different concentrations of Cr(NO3)·9H2O, Pb(NO3)2, Cd(NO3)2·4H2O solution were studied and the hydration products were analyzed using XRD and SEM. The results suggest that CSA immobilized Pb2+ and Cd2+ efficiently, while OPC solidified Cr3+ and Cd2+ well. Cd2+ prolonged the setting time of CSA and Pb2+ remarkably delayed that of OPC. There was only a slight influence of Cr3+, Pb2+, and Cd2+ on the compressive strength of CSA or OPC.

Maintaining Postharvest Quality of Fresh Button Mushrooms by Application of Hydrogen Peroxide and Antibrowning Agent Treatments

This experiment was conducted to study the effect of postharvest dipping of fresh button mushrooms (Agaricus bisporus) in hydrogen peroxide (H2O2) 5% alone or in combination with antibrowning agents (calcium chloride at 3 or 5%, ascorbic acid 3 or 5% and citric acid 2 or 4%) beside dipping in distilled water (control) to inhibition browning, had the lower level of microbial load and maintaining quality during storage for 12 days at 4 ± 1oC and 90 ± 2% relative humidity during two successive seasons of 2016 and 1017. Results showed that all studied treatments reduced weight loss percentage, browning index and Polyphenol oxidase activity, total bacteria counts, yeast and mold counts and maintaining of phenolic and flavonoids contents of fresh button mushrooms during cold storage comparing with untreated control. However, dipping button mushrooms in solution H2O2 5% + calcium chloride 5% was the most effective in this concern, which reducing browning, maintaining quality and inhibiting microbial counts for 12 days at 4 ± 1oC and 90 ± 2% relative humidity.

Hydrothermal synthesis of Ag-ZrO2/r-GO coating on CoCrMo substrate

A simple hydrothermal method was used to synthesize silver-doped zirconia-reduced graphite oxide (Ag-ZrO2/r-GO) composite coating on CoCrMo, an alloy commonly used in artificial hip joints. The Ag-ZrO2/r-GO coating is mainly intended to extend the service life of artificial hip joints via a rational coating design, which consists of three components, namely, a ceramic component ZrO2, a friction reducing component r-GO, and an antibacterial agent Ag. After hydrothermal treatment in Zr(SO4)2·4H2O solution containing GO at 200 °C for 24 h, ZrO2/r-GO coating of about 12.5 µm thick was formed on CoCrMo substrate. Ag was incorporated subsequently by soaking in AgNO3 solution and calcination was carried out to improve the adhesion of the coating on CoCrMo substrate.

High density liquid structure enhancement in glass forming aqueous solution of LiCl.

We investigate using molecular dynamics simulations the dynamical and structural properties of LiCl:6H2O aqueous solution upon supercooling. This ionic solution is a glass forming liquid of relevant interest in connection with the study of the anomalies of supercooled water. The LiCl:6H2O solution is easily supercooled and the liquid state can be maintained over a large decreasing temperature range. We performed simulations from ambient to 200 K in order to investigate how the presence of the salt modifies the behavior of supercooled water. The study of the relaxation time of the self-density correlation function shows that the system follows the prediction of the mode coupling theory and behaves like a fragile liquid in all the range explored. The analysis of the changes in the water structure induced by the salt shows that while the salt preserves the water hydrogen bonds in the system, it strongly affects the tetrahedral hydrogen bond network. Following the interpretation of the anomalies of water in terms of a two-state model, the modifications of the oxygen radial distribution function and the angular distribution function of the hydrogen bonds in water indicate that LiCl has the role of enhancing the high density liquid component of water with respect to the low density component. This is in agreement with recent experiments on aqueous ionic solutions.

Solubility of the Metal Precursor Ni(NO3)2·6H2O in High-Pressure CO2 + Ethanol Mixtures

The solubility of Ni(NO3)2·6H2O in high-pressure CO2 + ethanol mixtures was measured using a high-pressure variable-volume view cell from (308.2 to 353.2 K) and up to 25.0 MPa. This compound has been used previously as a Ni precursor in metal deposition experiments using supercritical CO2. Ni(NO3)2·6H2O was not soluble in pure CO2 but the addition of ethanol into the system allowed the solubilization of the hydrated salt in the mixture. Mole fraction of Ni(NO3)2·6H2O varied from 1.67 × 10–4 to 1.97 × 10–3. At these salt concentrations, the phase diagram of the CO2 + EtOH + Ni(NO3)2·6H2O system resembled that of the CO2 + EtOH binary system and, at the studied conditions, a vapor–liquid equilibrium was observed. For the higher ethanol concentrations, the bubble points closely matched those of the CO2 + EtOH system. For the lower EtOH concentrations, however, much higher solubilization pressures were required, due to the release of water molecules from the salt into the solution. Ni(NO3)2·6H2O solutions wer...

CATHODIC DEPOSITION OF Mg(OH)2 COATINGS ON PURE Mg IN THREE Mg SALTS AQUEOUS SOLUTIONS

Film-forming effects of cathodic deposition on pure Mg substrate at constant DC in aqueous solutions of magnesium nitrate (Mg(NO3)[Formula: see text]6H2O), magnesium chloride (MgCl[Formula: see text]6H2O) and magnesium sulfate (MgSO[Formula: see text]7H2O) respectively were investigated systematically. Typical processes were studied by potentiodynamic cathodic polarization and galvanostatic polarization and typical samples were analyzed by SEM and XRD. The results indicate that the depositing efficiency is not only the highest but stablest, and deposited coatings show the best uniformity with Mg(NO3)[Formula: see text]6H2O solution employed as depositing medium and applied current density [Formula: see text][Formula: see text]mA cm[Formula: see text]. Cathodic deposition leads to regular mass loss of Mg substrate. The cathodic polarization curve of pure Mg in magnesium nitrate solution shows more obvious pseudo-passivation, several Tafel regions with different slopes appearing before diffusion-limited current density region, and oxygen consumption is the major cathodic reduction reaction under specified current density. However, hydrogen evolution reaction is dominant in both Mg chloride and Mg sulfate solutions. The deposition coatings are all composed of continuous and uniform mesh-like “basic layer” adjacent to substrate and discrete distributed snowball-like particles on the microscopic scale. The phase compositions are all crystal Mg(OH)2, and the coatings deposited in Mg chloride solution have (011) preferred orientation.

Nanocrystalline LiCo0.8Fe0.2PO4 / Multi-Walled Carbon Nanotubes Positive Electrode for 5-Volts Class Lithium Ion Batteries

1. Introduction Lithium cobalt phosphate (LiCoPO4) with olivine structure has attracted much attention as a new positive electrode material for lithium ion batteries because of its high potential (4.8V vs. Li/Li+), theoretical capacity (167 mAh g-1) and thermal stability due to the P-O covalent bonding. However, the practical use of LiCoPO4 has been limited by the capacity fading during cycling due to the electrolyte oxidation and irreversible structure changes such as amorphization and anti-site defects of the material during charge and discharge1). Besides, it suffers from its poor rate performance related to the inherently low electron conductivity (<10-9 S cm-1)2) and Li+ diffusivity (<10-13 cm2 s-1)2) due to its b-axis oriented diffusion path. To overcome these limitations, we have synthesized Fe-substituted LiCoPO4 (LiCo0.8Fe0.2PO4) nanoparticles which are highly dispersed within a multi-walled carbon nanotube (MWCNT) matrix via an original in-situ material synthesis method called ultracentrifugation (UC) treatment3,4). Here, we also report about the influence of Fe substitution on cycle and rate performances of LiCo0.8Fe0.2PO4. 2. Experimental UC treatment was carried out on the prepared mixture of Co(CH3COO)2・4H2O, Fe(CH3COO)2, CH3COOLi, citric acid, MWCNT and H3PO4 aqueous solution. Obtained composites were electrochemically characterized using a 2032 coin half-cell with Li metal in 1M LiPF6 / EC:PC:DMC (1:1:3, volume ratio). Physicochemical characterizations of the LiCo0.8Fe0.2PO4/ MWCNT composite were conducted by HRTEM, XRD, XPS, XAFS measurements and Mössbauer spectroscopy. 3. Results and Discussion The XRD pattern of LiCo0.8Fe0.2PO4 / MWCNT composite indicates an olivine structure, without impurity phases. The combination of XRD, XPS, XAFS and Mössbauer analysis suggests that substituted Fe3+ into LiCoPO4 crystals was not placed in the Co2+ site, but in the Li+ site. The result of HRTEM observation indicates that LiCo0.8Fe0.2PO4 nanocrystals (ca. 100 nm) were highly dispersed within a MWCNT matrix. In addition, HRTEM images of LiCo0.8Fe0.2PO4 / MWCNT composite showed that a substitution of Fe3+ into LiCoPO4 crystals prevents degradations such as amorphization of LiCoPO4and electrolyte decomposition during charge and discharge processes. Then, LiCo0.8Fe0.2PO4 / MWCNT composite showed a higher discharge capacity of 130 mAh g-1 than LiCoPO4 / MWCNT composite and enabled a 100C (36 seconds) rate discharge with 45 mAh g-1. Furthermore, the obtained composite showed stable cycle performance with 81 % of capacity retention after 100 cycles at 0.2C. These enhancements were achieved by the combination of an entanglement between nanocrystalline LiCo0.8Fe0.2PO4 and MWCNT matrix and Fe3+ substitution in the Li+ site of LiCoPO4. The Fe3+substitution gives a “pillar effect” which effectively prevents an irreversible crystal structure change and electrolyte decomposition during charge and discharge processes, resulting in the stable cycle performance. References 1) A. Boulineau et al., Chem. Mater., 27, 802 (2015). 2) S. Brutti et al., ACS Symposium Series, (2013). 3) K. Naoi et al., Acc. Chem. Res., 46, 1075 (2013). 4) K. Naoi et al., Energy Environ. Sci., 5, 9363 (2012).

Production of conductive electrospun polypyrrole/poly(vinyl pyrrolidone) nanofibers

This article reports on a new method for the production of Polypyrrole/Poly(vinyl pyrrolidone) nanofibers via the electrospinning of pyrrole solution and subsequent oxidation. The low solubility of polypyrrole makes its electrospinning very difficult. However, low viscosity of pyrrole makes it also unsuitable for electrospinning as well. It was found that increasing the viscosity of pyrrole by adding poly(vinyl pyrrolidone) (PVP) (9% w/w), makes its electrospinning possible. The electrospun pyrrole − PVP nanofibers were collected in a solution of FeCl3·6H2O (2% w/v) and dopant in ethanol and oxidized in-situ, in other words polymerized to PPy (one step method). In another method (two step method), the electrospun pyrrole-PVP-dopant nanofibers were collected on an aluminum foil and then detached from it. To polymerize pyrrole, the nanofibrous mats were immersed in FeCl3·6H2O (2%w/v) solution. P-toluene sulfonic acid (PTSA) and anthraquinone-2-sulfonic acid sodium salt (AQSA) were employed as dopant. The SEM micrographs showed that PPy-PVP nanofibers with an average diameter as low as 440nm could be prepared. X-ray diffraction patterns showed a crystallinity of about 25.7% for the PPy-PVP nanofibers. FTIR analysis proved the formation of PPy as well as the absence of any considerable reaction between PPy and PVP. The highest electrical conductivity recorded for the AQSA doped PPy-PVP nanofibers with an average diameter of around 830nm was 5.22×10−1Scm−1 which is higher than the highest conductivity of 0.5Scm−1 reported for PPy fibers (average diameter=3μm) in the literature.

Preparation of nanoscale iron (oxide, oxyhydroxides and zero-valent) particles derived from blueberries: Reactivity, characterization and removal mechanism of arsenate

The application of iron nanoparticles (FeNPs) to the removal of various pollutants has received wide attention over the last few decades. A synthesis alternative to obtain these nanoparticles without using harmful chemical reagents, such as NaBH4, is the use of extracts from different natural sources that allow a lesser degree of agglomeration, in a process known as green synthesis. In this study, FeNPs were synthesized by ‘green’ (hereafter, BB-Fe NPs) and ‘chemical’ (hereafter, nZVI) methods. Extracts of leaves and blueberry shoots (Vaccinium corymbosum) were used as reducing agents for FeCl3·6H2O solution in the green synthesis method. FeNPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), electrophoretic migration, Brunauer-Emmett-Teller (BET) surface area analysis and X-ray diffraction (XRD) and evaluated for the removal of As(V) from aqueous systems. In both synthesis methods, XRD analysis confirmed the presence of the different kinds of iron nanoparticles. SEM analysis showed that the average size of BB-Fe NPs was 52.4nm and that a variety of nanoparticles of different forms and associated structures, such as lepidocrocite, magnetite, and nZVI, were present, while the dimensions of nZVI were 80.2nm. Comparatively significant differences regarding the electrophoretic mobility were found between both materials pre- and post-sorption of As(V). The velocity of As(V) removal by BB-Fe NPs was slower than that by nZVI, reaching equilibrium at 120min compared to 60min for nZVI. The removal kinetics of As(V) were adequately described by the pseudo-second-order kinetic model, and the maximum adsorbed amounts of this analyte are in close accordance with the experimental results. The Langmuir-Freundlich model is in good agreement with our experimental data, where the sorption capacity of nZVI and BB-Fe NPs was found to be 52.23 ± 6.06 and 50.40 ± 5.90 (mg·g−1), respectively. The use of leaves of Vaccinium corymbosum affords an easy-to-synthesize, low-cost, and eco-friendly material with capabilities similar to nZVI. BB-Fe NPs are promising for arsenic remediation, which has emerged as a new alternative for water purification and sanitation.