Influence Of Reactant Concentration Research Articles

In-situ construction of chitosan@tannin structure on bamboo fiber for green and convenient reinforcement of poly(3-hydroxybutyrate) biocomposite

Fiber-reinforced biocomposites were widely considered as the optimal sustainable alternative to traditional petroleum-based polymers due to their renewable, degradable, and environmentally friendly characteristics, along with economic benefits. However, the poor interfacial bonding between the matrix and natural fiber reinforcement remained a key issue limiting their mechanical and thermal properties. Focusing on cost-effective, convenient, and low-pollution chemical methods, this work proposed a strategy for in-situ synthesis of composite structures on bamboo fiber (BF) surfaces. Crude chitosan (CS) and reclaimed tannic acid (TA) were utilized as the raw materials, to construct stereo-netlike chitosan @ tannin structures (CS@TA) via a one-pot method facilitated by hydrogen bonding and complexation. The influence of reactant concentration and pH value on the process was further investigated and optimized. The CS@TA structure improved the interfacial bonding between the BF reinforcement and matrix poly(3-hydroxybutyrate) (PHB), and this non-amino-driven construction provided a potential reaction platform for functionalizing the interfacial layer. The modified biocomposite showed improvements in tensile and impact strengths (51.58 %, 41.18 %), also in tensile and flexural moduli (13.59 %, 26.88 %). Enhancements were also observed in thermal properties and heat capacity. This work presents a simple and promising approach to increase biocomposite interface bonding.

Insight into the Preparation of MgAl-Layered Double Hydroxide (LDH) Intercalated with Nitrates and Chloride Adsorption Ability Study

In recent years, layered double hydroxide (LDH) has attracted extensive attention of researchers in the field of corrosion protection due to its unique structure and anion exchange characteristics. However, its chloride adsorption capacity remains to be further optimized to increase its corrosion protection ability. In this work, the influence of reactant concentration on the prepared MgAl-LDH intercalated with nitrates was investigated, and the morphology, composition, and structure were characterized by scanning electronic microscopy/energy dispersive spectrometer (SEM/EDS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), respectively. The results indicate that the reactant concentration did not have an obvious influence on the particle size and morphology of LDH, while the composition and crystalline structure were changed to some extent. The corresponding reasons were interpreted deeply. The chloride absorption behavior was investigated, and the powder after immersion in NaCl solutions with different concentrations was characterized by XRD to explain the difference in chloride adsorption amounts. The MgAl-LDH powder synthesized at higher concentrations presented excellent chloride adsorption ability with a Qm value of 155.88 mg/g, which was much better than that reported in the literature. This work demonstrated the superior chloride adsorption of the synthesized MgAl-LDH, and it is of great significance for providing a solid foundation and guidance for the industrial application of LDH in the field of corrosion protection in the future.

Glucose oxidase modified Fenton reactions for in-situ ROS generation and potential application in groundwater remediation

Catalyzed H2O2 propagations (CHP) have demonstrated great potential in the remediation of chlorinated aliphatic hydrocarbons (CAHs) like trichloroethene (TCE) contaminated groundwater. However, the importation of highly unstable H2O2 into subsurface environment remains challenging. In this work, the in-situ H2O2 generation reaction between glucose oxidase (GOD) and glucose was applied in combination with Fe(II) to form the modified Fenton system (GMFs) and its performance in TCE oxidative degradation was investigated. The influence of reactant concentration as well as environmental factors like temperature and pH on the kinetics of TCE oxidation in GMFs were studied. At optimized conditions, about 78% TCE were removed within 8 h in GMFs, which remained effective over the temperature range of 15–30 °C and pH range of 3.6–6.0 (in acetate buffer). The in-situ H2O2 and OH generation capacity of GMFs were further investigated to elucidate their functional mechanism on TCE oxidation. Intermediate and product analysis indicated the near-complete release of chloride ion by TCE oxidation with few organic chlorinated intermediates detected. This work reveals the potential of GMFs for CAHs contaminated groundwater remediation through in-situ generation of reactive oxygen species.

The High Surface Ratio Micro-MoS<sub>2</sub> Grain Composed of MoS<sub>2</sub> Nanosheet Prepared with One-Step Hydrothermal Synthesis

Micro molybdenum disulfide was prepared with one-step hydrothermal method; the influence of reactant concentration and temperature on the surface ratio of micro-MoS2 grain was investigated. Raman spectroscopy (Raman), X-ray diffraction (XRD), and Scanning electron microscopy (SEM) were used to characterize the structure, composition and morphology of MoS2. The results show that micro-MoS2 grains were synthesized with one-step hydrothermal synthesis, and the morphology of micro-MoS2 grains is like flower and sphere. The SEM figures indicate that the surface ratio of micro-MoS2 grains is different and also show that the surface ratio of micro-MoS2 grains can be improved by regulating reactant concentration and temperature. This research showed a method to improve the surface ratio of micro-MoS2 grains.

Alkyl pyrazine synthesis via an open heated bath with variable sugars, ammonia, and various amino acids.

Semi-quantitative characteristics of headspace volatile pyrazines which constituted around 1% by weight of the final product have been previously described. The influence of reactant concentration, reaction temperature, and reaction time on both the yield of total alkyl pyrazines and the distribution pattern of specific identified pyrazines has not been reported. The optimum synthetic conditions were 5 mol L-1 NH4 OH, 2 mol L-1 rhamnose, 0.5 mol L-1 leucine at 110°C for 2 h. The greatest total amount of pyrazines obtained was 17 280 µg of extracted product which translated into 31% 2,6-dimethyl pyrazine, 17% 2-methyl pyrazine, 15% 2-ethyl-6-methyl pyrazine, and 16% 2-isoamyl-6-methyl pyrazine. The yield of synthesized pyrazines increased at higher temperatures. Quantitative total and specific pyrazine results as opposed to analysis of only headspace volatiles are more representative of pyrazine synthesis. © 2016 Society of Chemical Industry.

Influence of reactant concentration on optical properties of ZnO nanoparticles

Zinc oxide (ZnO) nanoparticles have been prepared by wet chemical method from zinc acetate. Particle size was controlled by adjusting the reactant concentration. The size of nanoparticles was investigated using ultraviolet–visible absorption spectra and photoluminescence spectra. The present nanoparticles exhibit non-linear optical behaviour with blue shift of the wavelengths as the particle size decreases. Furthermore, yellow emission is observed in ambient air while it disappears in the presence of nitrogen gas and gets substituted by blue violet emissions. While the blue violet emissions are familiar and likely to be attributed to electronic transitions from localised states (e.g. shallow donor states on Zn interstitials ‘Zni’) or the conduction band edge to the valence band, the yellow emission in the absence of nitrogen remains unclear. Our results of the present investigation suggest that the bubbling with nitrogen should fill the oxygen vacancies, substitute the oxygen interstitials, passivate the dangling bonds and introduce shallow acceptor states, which allow electronic transitions with shorter wavelengths (i.e. blue violet emissions). In the absence of nitrogen, surface defects such as oxygen interstitials and Zn(OH)2 and possibly other point defects become again active and induce deep acceptor states of ∼1 eV above the valence band edge, which allow electronic transitions of longer wavelength (i.e. yellow emission). Our results are compared to several available experimental data and first principle calculations in order to support our claims and conclusions.

Influence of reactant concentration on formation of AgCl particles in PEO–PPO–PEO microemulsion and morphology and performance of AgCl–PMMA membranes

AbstractAgCl/poly(methyl methacrylate) (PMMA) organic–inorganic hybrid membrane has been synthesized by reverse microemulsion polymerization using triblock copolymer polyoxyethylene–polyoxypropylene–polyoxyethylene as surfactant and MMA as oil phase. The results by ultraviolet–visible spectrum, transmission electron microscopy, and scanning electron microscopy showed that small AgCl nanoparticles distributed well in the F127 microemulsions and hybrid membranes at low reactant concentration. AgCl nanoparticles in the microemulsion became smaller with increasing reactant concentration. However, AgCl nanoparticles aggregated obviously in hybrid membranes, when reactant concentration was more than 0.15 mol L−1. The performance of different hybrid membranes for separation of the benzene and cyclohexane was measured. The results indicated that the separation performance of membrane was promoted obviously due to presence of more well‐dispersed AgCl particles in hybrid membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Reactive polymer films: Polypyrrole oxidation kinetics in aqueous solution

The oxidation kinetics of electrogenerated polypyrrole films was studied in aqueous solution. The influence of reactant concentrations (LiClO 4 in solution and active centres in the polymer film) and temperature on the kinetics has been studied. The usual procedure for any kinetic study was now repeated for different initial states, attained by electrochemical reduction at the same cathodic potential for different reduction times. For rising reduction times, lower kinetic coefficient ( k) and higher activation energies ( E a) were obtained. The activation energy is assumed to include rising conformational energy for more packed conformations of the initial states. Both kinetic magnitudes become a way to quantify the initial packing conformational degree. So, kinetic magnitudes can include structural information opening a new window for the chemical kinetics of reactive macromolecules that could be extended to reactive biopolymers. When compared the evolutions of k and E a experimental changes from aqueous and acetonitrile solutions of the same salt, important differences were found. Evolutions of k and E a from different solvents could be used as tools to quantify the polymer–solvent interaction evolution along the reaction.

Influence of reactant concentrations and solution acidity on the complexation of 188Re with 1-hydroxyethane-1,1-diphosphonic acid

Specific features of the complexation of 188Re with 1-hydroxyethane-1,1-diphosphonic acid (HEDP) were studied in relation to the solution acidity and reactant concentrations. The reaction rate and efficiency of the complexation of 188Re with HEDP increase with decreasing pH. A decrease in the reactant concentrations leads to a decrease in the reaction rate and in the efficiency of binding of 188Re with HEDP. The maximal binding of 188Re with HEDP is attained at pH 2.70, HEDP concentration of 117 µmol ml−1, and SnCl2 and ascorbic acid concentrations of 10 µmol ml−1. The results obtained can serve as basis for further optimization of the reaction conditions.

The Microstructural Evolution of Mn<sub>3</sub>O<sub>4</sub> Hausmannite during Autoxidation

Mn3O4 hausmannite, which is a normal spinel with the Mn2+ in the tetrahedral site and the Mn3+ in the tetrahedral site, is one of the most stable manganese oxides. Variation in the valence of Mn ions (2+, 3+ and 4+) contributes to several different structures of manganese oxides. The autoxidation of precipitated manganese hydroxide in an alkaline solution is a practical approach to synthesize hausmannite (Mn3O4) at low temperature. During the process, the particle size and morphology of derived products were totally different from the precursors even though nanometer-sized Mn(OH)2 crystals were fabricated at first. It was observed that the variation was resulted from the accumulation of produced Mn3O4 crystallites which departed from the original crystals. This study has not only discussed the influence of reactant concentrations on the particle size and morphology of derived powders, but also revealed the morphological transformation of crystals involved in autoxidation with the aid of electron micrographs

The Influence of Reactant Concentration and Reaction Medium Ionic Strength, Viscosity, and Temperature on the Immunocomplex Substitution Reaction in the Radioimmunoassay of Aldosterone

Competitive protein binding radioimmunoassay (CPB-RIA) is a principal method for quantifying serum aldosterone concentration. The accuracy of this method is critically dependent on factors that influence the substitution reaction between unlabeled (Q) antigen (aldosterone) with 125I-labeled antigen (M) bound to anti-aldosterone antibody (P). We studied the influence of initial concentration of M, ionic strength, viscosity, and temperature on the substitution reaction between M and Q. In addition, we propose a kinetic model for this reaction. We used a commercially available CPB-RIA for aldosterone, a gamma counter, and a viscosimeter to study the effect of initial concentration of M, ionic strength, viscosity, and temperature on the substitution reaction between M and Q. Data were analyzed using Statistica software. The apparent rate constant for the reaction between M and Q in the formation of PM is dependent on the initial concentration of M, and the ionic strength, viscosity, and temperature of the reaction medium, and independent of the concentration of Q. Moreover, this reaction is endothermic and is not controlled by diffusion. Our results support the proposed model for the reaction between Q, M, and P: PM + Q ↔ PQ + M.

A current distribution model of a porous fuel cell electrode

A one-dimensional model of the current and potential distribution in a porous electrode, which accounts for internal limitations of mass transport is presented. The electrode kinetics of the reaction are described by the Tafel approximation and the mass transport limitations are described by a mass transfer coefficient. The model is solved analytically to give a convenient algebraic equation to predict the influence of electrode parameters, such as conductivity, thickness and specific surface area on electrode polarisation. The model can also predict the influence of reactant concentration and internal mass transport on the electrode polarisation behaviour. The predicted electrode polarization is in agreement with that observed for a porous platinum based anode.

Synthesis and Characterization of a Novel Zn-polycarboxylate Ocular Adhesive

A Zn-polycarboxylate biocompatible adhesive was synthesized from polyacrylic acid and Zn-acetate solutions. The influence of reactant concentration, from 1 to 3 N, on the properties of this compound, was studied. The reaction product was characterized by both infrared (IR) and Raman spectroscopies and scanning electron microscopy. Adhesion behavior was evaluated by 90° and 180° peel-out testing using wood and cowhide as substrates, to simulate bonding to living tissue. The measured adhesion strength increases with reactant concentration. In-vivo tests were performed in dogs. Preliminary results show a transparent and flexible polymer material with very good adhesion to cornea tissue.

Influence of reactant concentration and reaction time in the chemical modification process of polypropylene by p-phenylen-bis-maleamic acid in the melt

Following earlier studies on chemical modification processes of polypropylenes by polar monomers, a new study by grafting p-phenylen-bis-maleamic acid in the molten state has been carried out. In a previous work a four independent variable Box–Wilson experimental design lets us conclude the adequacy of working at a certain gear rate and low times of reaction. This is the reason why, in this work, a two independent variable design (reactant concentrations) has been used and applied to four different times of reaction in order to check those findings. Besides, it is also confirmed that the process follows an oscillating evolution of grafting level with the reaction time, and the existence of critical points for the reactant concentrations ( p-phenylen-bis-maleamic acid and dycumile peroxide). These facts seem to agree with a chemisorption mechanism, governing the reaction yields in this kind of reactive systems, where the main and limiting role is played by the macromolecular substrate.

Preparation of marked poly(vinyl chloride) by reactive processing for identification by UV devices (recycling)

AbstractThe grafting of sodium 2‐thionaphtholate (NaTN) and sodium p‐thiocresolate (NaTC) in poly(vinyl chloride) (PVC) has been studied in the melt with the aim of obtaining a marked polymer for easy recognition and separation by UV devices. The influence of reactant concentration. DOP concentration, and temperature was investigated to determine the best conditions to obtain a controlled modification in the polymer. High degrees of grafting, efficiencies > 80%, and no side reactions, such as degradation or crosslinking, have been obtained under polymer processing conditions. The reaction of PVC with both reactants is also stereospecific. The ultraviolet spectrum of p‐thiocresolate grafted PVC shows a maximum absorption in the region < 300 nm, and that of a 2% thionaphtholate grafted PVC in the region of 360 nm, which is far from the UV absorption of a plasticized PVC. While the polymer marked with the first reagent can be used without plasticized polymers, the second can also be used with plasticized PVC, and therefore distinguished from polyolefins. The results reported herein may be useful in the development of polymer recycling, although barriers and interferences can exist.

Precipitation of calcium oxalates from high ionic strength solutions III. the influence of reactant concentrations on the properties of the precipitates

The influence of the initial reactant concentrations ([Ca]=1×10 -5-3×10 -1 mol dm -3, [Ox]=1×10 -5-1×10 -1 mol dm -3) and the aging time on the composition and morphology of calcium oxalates precipitating from 0.3 mol dm -3 sodium chloride solutions at pH=6.5±0.2, 298 K was investigated. In the whole investigated concentration region only monoclinic calcium oxalate monohydrate (COM) and tetragonal dihydrate ( COD, CaC 2O 4·(2+x)H 2O, x=0.25 or 0.5 ) were identified. The relative amounts of these species and their morphologies were dependent on the initial supersaturation, the reactant concentration ratio and the aging time. Compact crystals, dendrites and microcrystalline aggregates have been obtained at low, medium and high supersaturations respectively. Excess calcium and/or oxalate ions inhibited recrystallization of COD into the thermodynamically stable COM. The results are summarized in the form of precipitation curves and diagrams. Thermograms and IR spectra (in the region of 4000-200 cm -1) of COM, COD and the triclinic trihydrate (COT) are compared and discussed. The position and shape of IR absorption bands are defined by the crystal structure, the number of water molecules present and the system of hydrogen bonds.

Carbohydrate-containing derivatives of the trypsin-kallikrein inhibitor aprotinin from bovine organs. I. Modification with lactose, characterization and behaviour of the preparation in vivo.

The trypsin-kallikrein inhibitor aprotinin was modified with lactose. The influence of reactant concentrations, temperature, reaction time and sodium borohydride on the carbohydrate residue content and the inhibiting activity of glycated aprotinin were studied. Glycation of aprotinin neither shifts the pH optimum of the inhibitor-trypsin association reaction nor does it alter the apparent dissociation constant Ki of the complex measured at pH optimum. Glycation by lactose stabilizes aprotinin against denaturation by increased temperature. The distribution of native and modified aprotinin in rat organs after endocardiac injection was studied. Fixation of glycated aprotinin increases 2.5- to 3-fold in liver and decreases 2-fold in kidneys during the observation time (5 min-2 h) compared to native aprotinin.

Copolymers of starch and polyacrylonitrile: The dilution effect

AbstractIn the ceric ammonium nitrate‐initiated graft polymerization of acrylonitrile (AN) with starch, grafting frequencies and molecular weights of grafted polyacrylonitrile changed from 600 anhydroglucose units (AGU)/graft and 120000 to 280 AGU/graft and 36000 when concentrations of starch and AN were varied from 0.27 and 1.20 to 0.023 and 0.235 moles/l. of water, respectively. The influence of variety of starch, size of the starch granules, and reaction time was studied, and possible reasons for the influence of reactant concentration on the composition of the copolymer are considered.