Concentration Of Starting Solution Research Articles

Emerging NiO–rGO nanohybrids for antibiotic pollutant degradation under visible-light irradiation

The continuous increase in the discharge of unregulated chemical waste from various industries has prompted the need to remove organic pollutants. Photocatalysts have garnered tremendous attention owing to their advantages of eliminating pollutants without harmful products, low cost, and easy control. In this study, NiO nanocubes and NiO–reduced graphene oxide (rGO) nanohybrids were fabricated using a simple hydrothermal method. The chemical bonding and structural, morphological, absorption, and photocatalytic properties of the prepared NiO–rGO nanohybrids were characterized. The results showed that graphene could be successfully hybridized with the NiO nanocubes. The surface area supported the better light absorption perfromnace of the NiO–rGO nanohybrids. Hence, the separation rate of electron-hole pairs has been accelerated. The NiO-rGO nanohybrids significantly improved the degradation efficiency of the antibiotics, such as ciprofloxacin (Cipxn) and tetracycline (TetC), compared to pure NiO. NiO–rGO with 20 mg rGO exhibited the highest degradation efficiency for Cipxn (91.5%) and TetC (94.75%) under visible light irradiation. Further, the impact of several variables, such as the catalyst dose and starting solution concentration, on the pollutant degradation and related first-order kinetic constants were assessed. The trapping test results showed that the •OH and •O2 radicals are involved in the photocatalytic activity. Moreover, the catalysts exhibited good reusability and stability over four cycles. Therefore, the NiO–rGO nanohybrids can be potential photocatalysts for converting energy and cleaning the environment.

Research on the performance of modified blue coke in adsorbing hexavalent chromium

To solve the issue of hexavalent chromium (Cr(VI)) contamination in water bodies, blue coke powder (LC) was chemically changed using potassium hydroxide to create the modified material (GLC), which was then used to treat a Cr(VI)-containing wastewater solution. The differences between the modified and unmodified blue coke’s adsorption characteristics for Cr(VI) were studied, and the impact of pH, starting solution concentration, and adsorption period on the GLC's adsorption performance was investigated. The adsorption behavior of the GLC was analyzed using isothermal adsorption models, kinetic models, and adsorption thermodynamic analysis. The mechanism of Cr(VI) adsorption by the GLC was investigated using characterization techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FE-SEM), X-Ray Diffraction (XRD), and X-Ray Photoelectron Spectroscopy (XPS). With the biggest difference in removal rate at pH = 2, which was 2.42 times that of LC, batch adsorption experiments revealed that, under the same adsorption conditions, the GLC always performed better than LC. With a specific surface area that was three times that of LC and an average pore diameter that was 0.67 times that of LC, GLC had a more porous structure than LC. The alteration significantly increased the number of hydroxyls on the surface of GLC by altering the structural makeup of LC. The ideal pH for removing Cr(VI) was 2, and the ideal GLC adsorbent dosage was 2.0 g/L. Pseudo-second-order kinetic (PSO) model and Redlich-Peterson (RP) model can effectively describe the adsorption behavior of GLC for Cr(VI). Physical and chemical adsorption work together to remove Cr(VI) by GLC in a spontaneous, exothermic, and entropy-increasing process, with oxidation–reduction processes playing a key role. GLC is a potent adsorbent that can be used to remove Cr(VI) from aqueous solutions.

Modeling of hydrated cations transport through 2D MXene (Ti3C2Tx) membranes for water purification

Two-dimensional (2D) MXene membranes with high thermal and mechanical stability have shown great promise for water purification and desalination given their low energy consumption and high efficiency. In this work, we used a one-dimensional (1D) steady-state ion sieving and rejection model to describe the transport of hydrated cations through 2D lamellar MXene (Ti3C2Tx) membranes under transmembrane pressure field and external electric field. The model was validated using experimental data on the permeation fluxes of the 365 nm-thick MXene membrane with an interlayer spacing of 7.8 Å under transmembrane pressure of 0.2 atm at 298 K and under an external electric field between 0.1 and 8.25 V. The regressed model diffusion coefficients of penetrant (Di,pc) through the MXene membrane under transmembrane pressure field were 1.98 × 10−7 m2 h−1 for K+ and 1.77 × 10−7 m2 h−1 for Na+. Under the external electric field at 298 K and fixed starting solution concentration of 50 mg L−1 for K+ or Na+ cation, the diffusion coefficient of penetrant (Di,ec) from the regression were 2.55 × 10−9 m2 h−1 for K+ and 1.21 × 10−9 m2 h−1 for Na+. By applying the regressed parameters from both operation modes into the one-dimensional ion sieving and rejection models, the effects of interlayer spacing, potential voltage, temperature, and thickness on the permeation and rejection of hydrated K+ and Na+ cations through the MXene membrane can be effectively simulated. The use and modification of a theoretical model for ionic transport through 2D MXene (Ti2C3Tx) membranes we reported here can provide essential insights to guide future membrane design and determine its applicability of water desalination.

Following Structural Changes by Thermal Denaturation Using Trapped Ion Mobility Spectrometry-Mass Spectrometry.

The behavior of biomolecules as a function of the solution temperature is often crucial to assessing their biological activity and function. While heat-induced changes of biomolecules are traditionally monitored using optical spectroscopy methods, their conformational changes and unfolding transitions remain challenging to interpret. In the present work, the structural transitions of bovine serum albumin (BSA) in native conditions (100 mM aqueous ammonium acetate) were investigated as a function of the starting solution temperature (T ∼ 23-70 °C) using a temperature-controlled nanoelectrospray ionization source (nESI) coupled to a trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) instrument. The charge state distribution of the monomeric BSA changed from a native-like, narrow charge state ([M + 12H]12+ to [M + 16H]16+ at ∼23 °C) and narrow mobility distribution toward an unfolded-like, broad charge state (up to [M + 46H]46+ at ∼70 °C) and broad mobility distribution. Inspection of the average charge state and collision cross section (CCS) distribution suggested a two-state unfolding transition with a melting temperature Tm ∼ 56 ± 1 °C; however, the inspection of the CCS profiles at the charge state level as a function of the solution temperature showcases at least six structural transitions (T1-T7). If the starting solution concentration is slightly increased (from 2 to 25 μM), this method can detect nonspecific BSA dimers and trimers which dissociate early (Td ∼ 34 ± 1 °C) and may disturb the melting curve of the BSA monomer. In a single experiment, this technology provides a detailed view of the solution, protein structural landscape (mobility vs solution temperature vs relative intensity for each charge state).

Use of Sucrose To Tune V2O5 Films Growth Deposited through the Spray Pyrolysis Technique

Vanadium pentoxide (V2O5) films can be easily obtained through the spray pyrolysis technique (SPT), although they are often accompanied by other vanadium oxide phases. The V2O5 phase growth is only observed at low starting solution concentrations and/or at slow deposition flows with high crystalline orientation. These conditions limit the characterization of new V2O5 properties and their industrial application. Sucrose use as reagent in the precursor solution was versatile enough to produce vanadium pentoxide under high flow rates and relatively high starting salt concentrations. In addition, it efficiently randomized the texturing of SPT-deposited samples. Nanostructured and polycrystalline vanadium pentoxides were obtained at salt concentrations ranging from 100 × 10–3 to 400 × 10–3 mol·L–1, at temperatures varying from 265 to 450 °C and a flow rate of 3000 mL·min–1. Moreover, when it comes to controlling the surface texture of deposited films, one can assume that sucrose is a chelating agent capable of...

Design of copolymer PLA-PCL electrospun matrix for biomedical applications

Electrospinning is a quite consolidated technique to produce polymer nanofibrous matrices whose nanostructured morphology received great interest for application in the biomedical field i.e. in manufacturing matrices for tissue regeneration.Purpose of the work to design electrospun matrices made of Poly-l-lactide-co-poly-ε-caprolactone (PLA-PCL) 70:30M ratio and their thoroughly physico-chemical and functional characterization. The ultimate goal of the research work is to obtain electrospun matrices suitable for circular substitution of esophageal defects. However the paper deals with very preliminary investigation mainly on electrospinning process and physical-chemical characterization of the electrospun matrices. The investigation on electrospinning process conditions involves polymer starting solution concentration between 20% w/v and 25% w/v, viscosity and surface tension, but also process parameters of electrospinning apparatus in order to optimize them at achieving homogeneous and reproducible nanofibers.The optimized electrospun matrices are characterized for their cytocompatibility, morphology (SEM analysis), polymer molecular structure in the solid state (FT-IR analysis) and thermal behavior (DSC analysis) and mechanical properties. In vitro degradation test is performed to evaluate electrospun matrix biodegradability.Results show good cytocompatibility for all polymer concentrations and electrospinning times. Moreover, the electrospun matrices biodegradation is slower with respect to matrices made by solvent casting method. The behavior is related to modifications in the polymer solid state and to polymer chains structure.

Sonosynthesis of Vaterite-Type Calcium Carbonate

Metastable nanoparticles of vaterite were formed using a simple ultrasound technique. The effects of ultrasound amplitude and duration, as well as solution concentration, were investigated. The produced particles were characterized using standard X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning and transmission electron microscopies (SEM and TEM, respectively). As expected, the ultrasound synthesis process caused the particle size to be smaller than with conventional (magnetic bar) stirring, and allowed for the reaction time to be shortened as the crystallization rate was increased. As shown by XRD, FTIR, and SEM, the ultrasound process also led to the formation of pure vaterite, though the presence of calcite occurred as the ultrasound power was reduced and the pulse time increased. For both conventional and ultrasound techniques, the particle size was reduced with an increase in starting solution concentration. Using this technique allows for reproducible, tailored c...

Effect of starting solution concentration in spray pyrolysis on powder properties and electrochemical electrode performance

Nano-composite powders consisting of Sr-doped SmCoO3 (SSC) and Sm-doped CeO2 (SDC) were synthesized by spray pyrolysis using different cation concentration solutions, and the effect of this cation concentration on the electrochemical performance of electrodes fabricated using the powders was investigated. Regardless of the cation concentration, spherical particles consisting of nano-order fine SSC and SDC crystallites were successfully obtained. Although the crystal size of all the synthesized powders was almost the same, the particle size increased with increasing cation concentration. The microstructure of the cathodes fabricated using the nano-composite powders clearly depended on the particle size of the starting powders; the microstructure became coarser with increasing particle size and the original particle shapes partially remained in the cathode network. Also, electrochemical measurements for solid oxide fuel cells with these cathodes revealed that the electrode performance was related to the microstructure. The electrode polarization resistance decreased with decreasing particle size, and a relatively fine microstructure cathode exhibited lower electrode polarization resistance, resulting in a high performance of 1.52Wcm−2 at 700°C. These results indicate that controlling the particle size, as well as controlling the nanostructure within the particles, is crucial to attain high performance electrodes.

Production and characterization of hypromellose phthalate nanoparticles containing levofloxacin for ophthalmic applications

Although eyedrops are nowadays the most used administration form of ophthalmic drugs, they present several problems: they imply repeated applications, lead to significant drug losses, and may cause undesirable side effects, as a result of the rapid drug absorption into the blood stream. Several attempts have been made to develop new drug delivery systems, which increase the residence time of the drugs in the eye and improve its bioavailability. Therapeutic soft contact lenses (SCLs) seem to constitute a promising alternative due to the prolonged contact with the eye. Although drug soaked contact lenses have demonstrated to be more efficient than eyedrops, they still present limitations: maximum drug load is limited and diffusion is the only resistance to drug transport across the gel, which may lead to short release times. Designing an effective system for the treatment of ocular diseases is a challenging task, to which nanotechnologies may give a valuable contribution. The incorporation of drug-loaded nanostructures in the SCLs materials may help to control the drug release rates and to maintain drug therapeutic levels for longer periods of time.The main objective of this work is to produce hypromellose phthalate (HPP 50) nanoparticles (NPs) containing levofloxacin (LOF) to incorporate in hydrogels for SCLs. LOF is an antibiotic which offers a broad spectrum against ocular infections and is used both in prophylaxis and treatment. The NPs were produced using a supercritical atomization process developed by the research team - Supercritical Enhanced Atomization (SEA) and were engineered in order to improve the release rate of LOF. Different working pressures, LOF concentrations and polymer+antibiotic starting solution concentrations were tested. The morphology and size of the obtained particles were analysed by scanning electron microscopy (SEM) (Figure 1). The release profiles of the drug were determined using a standard dissolution tester. The quantification of the drug in the supernatant was done by high performance liquid chromatography (HPLC). The particles which presented the best release rate were SEA 15 (Figure 2), containing 10% w/w of LOF and produced at 20 MPa with a concentration of polymer+antibiotic of 5 mg/mL. These particles were further characterized by dynamic light scattering (DLS) (Figure 3), which confirmed the wide size dispersion of the particles, and by zeta potential measurements, which gave a slightly negative potential, -10 mV.Future work may involve both the optimization of the experimental conditions to decrease the size dispersion of the particles and their eventual coating with polyelectrolytes in order to extend the drug release time.This study was financially supported by the project PEst- OE/QUI/UI0100/2011. Patrizia Paradiso acknowledges grant from the project SFRH/BD/71990/2010.

Adsorption and diffusion of strontium in simulated rock fractures quantified via ion beam analysis

AbstractAn experimental technique has been developed and applied to the problem of determining effective diffusion coefficients and partition coefficients of Sr in low permeability geological materials. This technique, the micro-reactor simulated channel method (MRSC), allows rapid determination of contaminant transport parameters with resulting values comparable to those determined by more traditional methods and also creates product surfaces that are amenable for direct chemical analysis. An attempt to further constrain mass flux was completed by detailed ion beam analysis of polished tuff surfaces (tuff is a polycrystalline polyminerallic aggregate dominated by silicate phases) that had been reacted with Sr solutions at concentrations of 10−5, 10−3 and 10−1 mol l−1. Ion beam analysis was carried out using beams of both protons (using particle induced X-ray emission and elastic backscattering spectrometry or EBS) and alpha-particles (using Rutherford backscattering spectrometry). The ion beam analyses showed that increased solution concentrations resulted in increased surface concentrations and that in the highest concentration experiment, Sr penetrated to at least 4 μm below the primary interface. The Sr surface concentrations determined by EBS were 0.06 (±0.05), 0.87 (±0.30) and 2.40 (±1.0) atomic weight % in the experiments with starting solution concentrations of 10−5, 10−3, and 10−1 mol l−1, respectively.

The effect of processing parameters on particle size in ammonia-induced precipitation of zirconyl chloride under industrially relevant conditions

The effect of pH of precipitation, starting solution concentration, and agitation levels on the particle size of hydrous zirconia precipitates have been investigated. It was found that all three variables affect the particle size of the hydrous zirconia. The smallest particle size is produced by a 0.81 M starting solution, precipitated at pH 12 with a high agitation level. The pH of precipitation was also found to have a significant impact on the type of hydrous zirconia produced. TGA/DTA, micro combustion and TEM/EDS were used to investigate the difference in the powders produced at pH 3 and 12. This work suggests that powders produced at pH 3 will have a structure similar to Zr[OH] 4 whilst those at pH 12 are more likely ZrO[OH] 2. XRD and micro-combustion suggest that the powders produced at pH 3 retained ammonium chloride whilst those produced at pH 12 did not. The filtration rates for the pH 3 product were significantly faster than that of the powders made at pH 12 which is significant in the industrial production of these materials.

Development of Pure Electric Bus with Mn type Li-ion Battery

Aluminum-doped lithium manganese powders were successfully produced by internal combustion-type spray pyrolysis using metal nitrate solution. As-prepared particles with an average diameter of about 4 μm had a porous microstructure and were nonagglomerated. Chemical analysis showed that the molar ratio of Li/Mn and the content of Aluminum were kept contact with the starting solution concentration. A lithium ion battery module for electric vehicle (EV) was also developed and its performance was examined. A 53 kWh lithium ion battery module was set on an electric microbus, and then its performance was examined.

Formation of a nickel catalyst on the surface of aluminosilicate supports for the synthesis of catalytic fibrous carbon

Conditions for the homogeneous precipitation of nickel hydroxide in the presence of urea onto the surface of aluminosilicate honeycomb monoliths, which were prepared based on clay, talc, and amorphous aluminum hydroxide, were examined. Factors affecting the concentration of supported nickel (synthesis time, starting solution concentrations, loaded amount of the support, and support calcination temperature) were studied. The possibility of supporting nickel hydroxide onto the surface of cellular ceramic foam, glass foam, and haydite was demonstrated. The morphology of nickel hydroxide particles, nickel metal particles on support surfaces, and carbon coatings synthesized in the course of the catalytic pyrolysis of a propane-butane mixture was studied by scanning electron microscopy.

Effect of Supersaturation on Crystal Size and Number of Crystals Produced in Antisolvent Crystallization.

The antisolvent crystallization of sodium chloride was carried out in batches to observe crystallization phenomena using ethanol as an antisolvent. To decrease high local supersaturation generated by the addition of antisolvent, the authors have proposed a new idea by choosing high ethanol concentration operational conditions. Obtained crystals seemed to be unagglomerated and monodispersed in the optimum range of ethanol concentration. From the observation of nucleation phenomena, it was considered that nucleation induced by the antisolvent addition occurred due to the local supersaturation generated at the boundary of the starting and feed solutions. On the other hand, crystal growth is considered to proceed by the supersaturation generated by sufficient mixing between the starting and feed solutions. Average crystal size increased with the increase of σg. The number of produced crystals increased with the increase of the starting solution concentration C. The induction period for nucleation tended to decrease with increase of C and σg. Since the number of produced crystals depended on C, nucleation was considered to be influenced by local mixing between the starting and feed solutions.

Manufacture of fine metallic silver powders by a reduction technique

1. Very fine metallic silver powders were produced by the chemical reduction technique, using divalent iron sulfate, hydrazine hydrate, and hydroxylamine as reducing agents. 2. A study was made of the effects of starting solution concentrations and temperature upon the particle size of the resultant silver powder and also of the effects of various methods of preparation and particle size upon the purity of the final product. The purest (99.7–99.85%) and finest (0.2–0.6μ) silver powders are obtained when an ammoniacal solution of silver nitrate is reduced with hydrazine hydrate in the presence of tartaric acid. 3. The specific surfaces of silver powders with mean particle sizes of 1.5 ± 0.3 and 0.4 ± 0.2μ were determined by the method of low-temperature krypton adsorption and found to be 0.25 ± 0.05 and 1.0 ± 0.2 m2/g, respectively.