Concentration Of Oxidizing Agent Research Articles

Controlling the bandgap of graphene oxide via varying KMnO4

This research focuses on the production and characterization of graphene oxide via Modified Hummers' method, with a specific emphasis on controlling oxidizing agent concentration. The study employed various analytical techniques to investigate structural and chemical properties. X-ray diffraction (XRD) revealed significant changes in interplanar spacing (8.3 Å to 14.6 Å), implying structural transformations. Raman spectroscopy inspected defects and layer formation. Field Emission Scanning Electron Microscope (FESEM) depicted structural evolution from multilayer lamellar structures to crumpled nanosheets as oxygen concentration varied. FTIR confirms the increase in intensity of notable oxygen containing functional groups, such as hydroxyl, epoxy and carbonyl groups. UV-VIS spectroscopy in conjunction with Tauc's plot shows an increase in bandgap energy (3.37 eV–3.70 eV), MATLAB modelling provides electronic properties of the material.

Biosynthesis of tetrahydropapaverine and semisynthesis of papaverine in yeast

Tetrahydropapaverine (THP) and papaverine are plant natural products with clinically significant roles. THP is a precursor in the production of the drugs atracurium and cisatracurium, and papaverine is used as an antispasmodic during vascular surgery. In recent years, metabolic engineering advances have enabled the production of natural products through heterologous expression of pathway enzymes in yeast. Heterologous biosynthesis of THP and papaverine could play a role in ensuring a stable supply of these clinically significant products. Biosynthesis of THP and papaverine has not been achieved to date, in part because multiple pathway enzymes have not been elucidated. Here, we describe the development of an engineered yeast strain for de novo biosynthesis of THP. The production of THP is achieved through heterologous expression of two enzyme variants with activity on nonnative substrates. Through protein engineering, we developed a variant of N-methylcoclaurine hydroxylase with activity on coclaurine, enabling de novo norreticuline biosynthesis. Similarly, we developed a variant of scoulerine 9-O-methyltransferase capable of O-methylating 1-benzylisoquinoline alkaloids at the 3' position, enabling de novo THP biosynthesis. Flux through the heterologous pathway was improved by knocking out yeast multidrug resistance transporters and optimization of media conditions. Overall, strain engineering increased the concentration of biosynthesized THP 600-fold to 121 µg/L. Finally, we demonstrate a strategy for papaverine semisynthesis using hydrogen peroxide as an oxidizing agent. Through optimizing pH, temperature, reaction time, and oxidizing agent concentration, we demonstrated the ability to produce semisynthesized papaverine through oxidation of biosynthesized THP.

The molecular structural transformation of jackfruit seed starch in hydrogen peroxide oxidation condition

Jackfruit (Artocarpus heterophyllus Lam.) is popularly grown in tropical countries including Vietnam. Jackfruit seeds contain high starch but usually discharged during processing produces about jackfruit. The study was carried out oxidizing the starch isolating from jackfruit seeds by hydrogen peroxide agent to increase starch value for its potential industrial applications. The optimal parameters were oxidizing agent concentration, starch/water ratio, temperature, pH and reaction time. The recovery efficiency was at 95.79%; Carbonyl content of oxidized jackfruit seed starch (OJS) products was at 1.06%; and carboxyl was at 0.29%. Scanning electron microscopy (SEM) revealed that the OJS particles remained the original structure, but the grain surface was no longer as smooth as natural starch but rough, appeared to have small pores and the edges lost definition completely. The vibrations of featured functional groups in OJS structure appeared at peak with the wavenumber of 1760 ​cm−1 related to the oscillation of the C = O group via Fourier transform infrared (FTIR) spectrum. The oxidation mainly occurred in the amorphous phase using X-ray diffraction (XRD) pattern. The structural modellings of jackfruit seed starch products related to glucose chains were shown based on evaluation for changes of microstructure via XRD and FTIR analyses Abstract Text.

Selective oxidation of 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furancarboxylic acid using silver oxide supported on calcium carbonate

This work revealed 5-hydroxymethylfurfural (HMF) oxidation towards 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) employed Ag2O supported on calcium carbonate as heterogeneous catalyst in conventional batch protocols and microwave-assisted batch conditions. Different reaction regimes were investigated, such as catalyst loading, reaction temperature, solvent types and oxidizing agent concentrations. 89 % HMF conversion, 85 % HMFCA yield as well as 95 % HMFCA selectivity achieved under optimum condition (125 mg 20 wt% Ag2O-CaCO3, 2 wt% aq. H2O2 with 0.1 mL min−1 flow rate in 50 min, oil bath 100 ºC). Microwave irradiation (30 W) afforded higher HMF conversion (95 %) as well as HMFCA yield (93 %) with HMFCA selectivity (97 %) under identical condition. Catalyst recycling showed deactivation (64 % HMF conversion and 50 % HMFCA yield in fourth time). Post-characterization was investigated to analyze catalyst deactivation. For instance, EDS and SEM mapping micrographs showed organic moieties deposited on the surface of catalyst. XRD exhibited no CaCO3 crystallographic modification happened after reaction, however, partial reduction of silver (I) to metallic silver (0) happened.

Extraction of Indium from By-products of Zinc Metallurgy by Ultrasonic Waves

The extraction of indium from hard zinc slag is a relatively common method, but it is desired to further improve the leaching efficiency of indium. The leaching effect of indium from a hard zinc slag via ultrasonication was studied. We have found that the infiltration efficiency of indium can be improved by ultrasonic waves through its cavitation effect, mechanical effect, etc. The use of calcium hypochlorite instead of the chlorine used in the conventional method as an oxidant reduces corrosion of the equipment and does not pollute the environment. In this paper, HCl–CaCl2 and Ca(ClO)2 were employed as a leaching agent and oxidant, respectively. The effects of ultrasonic power, leaching time, initial acidity, reaction temperature, concentration of CaCl2, and amount of Ca(ClO)2 on the leaching rate of indium from zinc metallurgy by-products were investigated. The optimum conditions were as follows: ultrasonic power 700 W, reaction temperature 70 °C, leaching time 50 min with ultrasonication and 60 min without ultrasonication, HCl concentration 4.5 mol/L, CaCl2 concentration 150 g/L, and oxidizing agent concentration 35 g/L. Under the optimal conditions, the leaching rate of indium was 96.42% with ultrasonication and 94.8% without ultrasonication. The effect of the ultrasonic waves on the slag during hard zinc leaching was studied by scanning electron microscope.

Oxidation- and Temperature-Responsive Poly(hydroxyethyl acrylate-co-phenyl vinyl sulfide) Micelle as a Potential Anticancer Drug Carrier.

Poly(hydroxyethyl acrylate-co-phenyl vinyl sulfide) (P(HEA-co-PVS)), as an oxidizable amphiphilic polymer, was prepared for the fabrication of an oxidation- and temperature-responsive micelle for the delivery of doxorubicin (DOX). The interfacial activity of H2O2-treated P(HEA-co-PVS) was significantly lower than that of the untreated variety, possibly because of the oxidization of PVS. P(HEA-co-PVS) exhibited a lower critical solution temperature (LCST) behavior and the LCST increased upon H2O2 treatment. The copolymer micelles, prepared by the dialysis method, were found to be round particles (less than 100 nm) on TEM micrograph. The release degree of Nile red loaded in the micelles was higher when the H2O2 concentration was higher, possibly because the micelles could be solubilized more readily at a higher H2O2 concentration. The release degree was more strongly dependent on the oxidizing agent concentration when the temperature was higher. DOX loaded in the micelles suppressed the in vitro growth of KB cells (a human cancer cell type originating from the cervix) much more effectively than DOX loaded in an unoxidizable control micelle and free DOX, possibly because the copolymer would undergo an increase in its LCST, lose its amphiphilic property, and the micelles would be disassembled. The DOX-loaded micelles were readily internalized into KB cells, as evidenced by flow cytometry (FACS) and confocal laser scanning microscopy (CLSM).

Stability study and oxidative degradation kinetics of posaconazole

Posaconazole (POS), a triazole derivative used for the treatment of systemic fungal infections, was recently found to be a potential therapeutic alternative for patients with chronic Chagas disease. It is necessary to determine the stability of POS and identify its degradation products to achieve the expected pharmacological effects and assess the risks of drug toxicity associated with this novel therapeutic application. This study aimed to evaluate POS stability under varied conditions using forced degradation tests (acidic and basic hydrolysis, thermolysis, and oxidation). A high-performance liquid chromatography (HPLC) method was developed for the separation and identification of POS and its degradation products. POS was stable to acid and basic hydrolysis and thermolysis but not to oxidation. POS and its degradation products were characterized by high-resolution positive mode electrospray ionization quadrupole time-of-flight (ESI-QTOF) mass spectrometry. Two degradation products with m/z values of 717 and 733 were detected. Molecular modeling was used for the calculation of the highest occupied molecular orbital (HOMO) and electrostatic potential changes. The results suggest that POS degradation begins with the breakage of its piperazine ring. This is the first study to report the kinetics of POS oxidative degradation under different oxidizing agent concentrations, temperatures, and pH conditions. The reaction followed second-order kinetics under all tested conditions. The analytical methods developed in this study were suitable to delineate the stability profile of POS. Elucidation of the degradation kinetics of POS is essential to ensure the stability of the drug in pharmaceutical formulations.

Oxidative desulfurization of diesel fuel oil using supported Fenton catalysts and assisted with ultrasonic energy

An ultrasound-assisted heterogeneous catalytic oxidation process was applied to eliminate sulfur from commercial diesel fuel oil. The studied variables were catalyst concentration, type of catalyst (homogeneous or heterogeneous), oxidizing agent concentration, and the application of ultrasound energy. Supported catalysts were prepared by impregnation of coal fly ash with an iron(II) sulfate aqueous solution using ultrasound energy. After drying, the catalyst was calcined at 500 °C for 4 h. The oxidizing agent was hydrogen peroxide. Ultrasound energy was applied with a frequency of 47 kHz and an intensity of 147 W. Ethanol was employed for extracting the oxidized compounds from the hydrocarbon mixture. Coal fly ash and ethanol were used with the purpose of applying low-cost raw materials in chemical processes. It was found that under the studied conditions, increasing oxidizing agent concentration and the application of ultrasound energy can enhance the sulfur removal from commercial diesel fuel oil. Catalyst concentration did not play a significant role in the process. Similar results were obtained using homogeneous or heterogeneous catalyst, which is important since the heterogeneous catalyst could be recovered, reactivated, and used in many cycles.

ORGANOPHOSPHATE ESTERS REMOVAL BY UV/H2 O2 PROCESS MONITORED BY 31P NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY

Abstract The present work aims to study the photocatalytic degradation of three organophosphate esters considered environmental emerging contaminants by the UV/H2O2 system with the use of 31P NMR spectroscopy to investigative their removal after the treatment. Results demonstrated the efficiency of the oxidation system in removing the esters tris(2-butoxyethyl) phosphate (TBEP), tris(2-chloroethyl) phosphate (TCEP) and tri-butyl phosphate (TBP) from aqueous solutions when they were individually present and mixed. High levels of degradation of these chemicals were achieved, in addition to the good performance of the analytical technique applied in the study, which represents some advantages in comparison with other techniques reported in the literature. An increase in the 31P NMR signal removal could also be observed when the oxidizing agent concentration increases. Decreases in solution acute toxicity were also verified for both TBP and TBEP treated samples when compared with the samples before the treatment.

Metal assisted photochemical etching of 4H silicon carbide

Metal assisted photochemical etching (MAPCE) of 4H–silicon carbide (SiC) in Na2S2O8/HF and H2O2/HF aqueous solutions is investigated with platinum as metallic cathode. The formation process of the resulting porous layer is studied with respect to etching time, concentration and type of oxidizing agent. From the experiments it is concluded that the porous layer formation is due to electron hole pairs generated in the semiconductor, which stem from UV light irradiation. The generated holes are consumed during the oxidation of 4H–SiC and the formed oxide is dissolved by HF. To maintain charge balance, the oxidizing agent has to take up electrons at the Pt/etching solution interface.Total dissolution of the porous layers is achieved when the oxidizing agent concentration decreases during MAPCE. In combination with standard photolithography, the definition of porous regions is possible. Furthermore chemical micromachining of 4 H–SiC at room temperature is possible.

Low temperature liquid phase catalytic oxidation of aniline promoted by niobium pentoxide micro and nanoparticles

A microwave-assisted hydrothermal method was employed to synthesis Nb2O5 (niobium pentoxide) nanoparticles and the effects of synthesis conditions on the physical-chemical properties were evaluated. The catalytic activity of the prepared samples in the liquid phase oxidation of aniline with aqueous hydrogen peroxide as oxidizing agent was also studied. The nanoparticles showed hexagonal structure and rounded shape covered by nanoneedles. The results evidenced high catalytic activity with total conversion of aniline at ambient condition. Aniline conversion and product selectivities depended on the experimental parameters, particularly the oxidizing agent concentration, the nature of the solvent, type of the catalyst and reaction time.

Liquid Phase Oxydehydration of Glycerol to Acrylic Acid over Supported Silicotungstic Acid Catalyst: Influence of Reaction Parameters

The liquid phase catalytic oxydehydration of glycerol to acrylic acid over supported silicotungstic acid (SiW) catalysts was carried out in the batch reactor. The effect of oxidizing agent concentration (H2O2), reaction temperatures (70 and 90 °C), types of supports (HZSM-5, SiO2 and Al2O3) and SiW loading (20-60 wt.% based on support) on the conversion and product yield were investigated. The addition of H2O2 and supported SiW catalysts significantly conducted the synergetic positive effects on glycerol conversion and acrylic acid yields as well as other desired products including glycolic acid, formic acid, acetic acid, acrolein and acrylic acid. High reaction temperature was able to enhance high glycerol conversion as the same yield of all desired products. The BET surface area of supported SiW catalysts played much more important role in the activities of oxydehydration of glycerol that this oxydehydration was more remarkable than the acidity of catalysts. Among all supported SiW catalysts, the SiW/HZSM-5 with SiW loading of 30 wt.% exhibited the highest glycerol conversion (85.54%) with the production acrylic acid yield of 30.57 % over 2.74 M H2O2 at 90 °C. The kinetics of glycerol conversion to desired products over supported SiW catalyst was explored.

Chemo Assisted Magnetic Abrasive Finishing: Experimental Investigations

In modern industries with advancement of technology advanced engineering materials are needed to be used like Tungsten, Titanium alloys, ceramics, various composites etc. These materials possess some special characteristics such as high hardness, high wear resistance, high toughness, high strength etc. which make them preferred over conventional materials in modern industries. Due to the stringent properties these materials are difficult to process. Different conventional finishing processes like grinding, lapping, honing, buffing etc. are generally inefficient in finishing these materials. Although processes like abrasive flow machining, magnetic field assisted finishing processes and chemo-mechanical finishing may be used but these may be less productive. Therefore a new process which uses combination of chemical oxidation and magnetic field assisted abrasion (magnetic abrasive finishing) has been conceived in the present work for faster processing.To establish the process experiments have been conducted on tungsten work piece and the effects of various process parameters like percentage weight of abrasive, oxidizing agent concentration, rotational speed of magnet and working gap on process response namely percentage change in average surface roughness value (ΔRa) was recorded. The experiments were planned using Taguchi L9 orthogonal array. Experimental data was analyzed using analysis of variance to understand contribution of various process factors on process response. SEM micrographs have also been obtained to study the surface morphology of the finished work piece. Regression model was developed to predict the percentage change in surface roughness in terms of significant process factors.

Redox initiation of bulk thiol–ene polymerizations

The unique formation-structure-property attributes and reaction behavior of the thiol-ene "click" reaction have been explored extensively for photochemically and thermally initiated reactions but have been much less explored for redox initiation. Therefore, the objective of this work is to characterize fully the impact of the initiation system, monomer structure, degree of functionalization, and inhibitor level on the redox-mediated thiol-ene polymerization rate and behavior. Moreover, this study confirms the ability of redox initiation to achieve full conversion of desired thiol-ene "click" products for small molecules in solution. For the multifunctional thiol-ene systems, polymerization rate was shown to be comparable to photo- and thermally initiated systems, but with the additional advantages of unlimited depth of cure and mild reaction conditions. Additionally, the network properties of the redox-initiated thiol-ene systems were on par with a photocured material formulated with identical monomers and radical initiating potential. Lastly, control over the polymerization rate and preceding induction period was garnered from the concentration of inhibitor included in the reaction mixture. The mechanism of action of quinone inhibition in redox-mediated thiol-ene polymerizations is shown to depend on both the presence of an aniline reducing agent and the concentration of inhibitor, with quinone concentrations in great excess of oxidizing agent concentrations actually leading to heightened polymerization rates when aniline is present.

Electrophilic iododestannylation of N-(4-(2-azanorborn-2-yl)butyl)-4-trimethylstannylbenzamide as a route to a novel radioiodinated compound for malignant melanoma

N-(4-(2-Azanorborn-2-yl)butyl)-4-[125I]iodobenzamide was prepared by the reaction of its trimethylstannyl precursor with Na125I in the presence of various oxidizing agents such as lactoperoxidase, Chloramine T, and Iodogen. The effect of reaction parameters such as temperature, reaction time, oxidizing agent concentration, pH, and substrate concentration was examined. The stability of the labeled product was evaluated. Chromatographic analysis of the reaction mixture by TLC using ethanol: ethyl acetate (1: 1) and by HPLC using methanol: water (55: 45) as eluent showed that the optimum radiochemical yield of the final product is 94% and the radiochemical purity is 99%. Also HPLC chromatographic analysis showed that the content of undesired by-products, especially of chlorinated products, in case of Chloramine T was higher than that in case of other oxidizing agents. With the lactoperoxidase method, the amount of undesired by-products was minimal and, therefore, the radiochemical purity was high.

Structural features of lignin obtained at different alkaline oxidation conditions from sugarcane bagasse

Lignin is a macromolecule frequently obtained as residue during technological processing of biomass. Modifications in chemical structure of lignin generate valuable products, some with particular and unique characteristics. One of the available methods for modification of industrial lignin is oxidation by hydrogen peroxide. In this work, we conducted systematic studies of the oxidation process that were carried out at various pHs and oxidizing agent concentrations. Biophysical, biochemical, structural properties of the oxidized lignin were analyzed by UV spectrophotometry, Fourier transform infrared spectroscopy, scanning electron microscopy and small angle X-ray scattering. Our results reveal that lignin oxidized with 9.1% H 2O 2 (m/v) at pH 13.3 has the highest fragmentation, oxidation degree and stability. Although this processing condition might be considered quite severe, we have concluded that the stability of the obtained oxidized lignin was greatly increased. Therefore, the identified processing conditions of oxidation may be of practical interest for industrial applications.

Novel radioiodinated sibutramine and fluoxetine as models for brain imaging

Brain imaging is a process which allows scientists and physicians to view and monitor the areas of the brain which allow diagnosis and following up different abnormalities in the brain. The aim of this study was to develop potential radiopharmaceuticals for the non-invasive brain imaging. Sibutramine and fluoxetine (two drugs that have the ability to cross blood–brain barrier) were successfully labeled with 125I via direct electrophilic substitution reaction at ambient temperature. The reaction parameters studied were substrate concentration, oxidizing agent concentration, pH of the reaction mixture, reaction temperature, reaction time and in vitro stability of the iodocompounds. The iodocompounds gave maximum labeling yield of 92 ± 2.77 and 93 ± 2.1%, respectively, and maintained stability throughout working period (24 h). Biodistribution studies showed that maximum in vivo uptake of the iodocompounds in the brain was 5.7 ± 0.19 and 6.14 ± 0.26% injected activity/g tissue organ, respectively, at 15 and 5 min post-injection, whereas the clearance from the mice appeared to proceed via the hepatobiliary pathway. Brain uptake of 125I-sibutramine and 125I-fluoxetine is higher than that of 99mTc-ECD and 99mTc-HMPAO (currently used radiopharmaceuticals for brain imaging) and so radioiodinated sibutramine and fluoxetine could be used instead of 99mTc-ECD and 99mTc-HMPAO for brain SPECT.

Oxidizing agent concentration effect on metal-assisted electroless etching mechanism in HF-oxidizing agent-H 2O solutions

The mechanism of metal-assisted electroless etching of silicon in HF-oxidizing agent-H 2O etching system as a function of oxidizing agent concentration was studied. Three types of oxidizing agent were experimented namely Na 2S 2O 8, K 2Cr 2O 7 and KMnO 4. Their concentrations were varied from 0.05 M to 0.3 M. The layers formed on silicon were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray (EDX). It is shown that an insoluble solid-phase film (K 2SiF 6) form on silicon surface when concentration of K 2Cr 2O 7 or KMnO 4 increases in chemical solutions. On other hand, when Na 2S 2O 8 concentration increases, the surface roughness decreases without any chemical complex formation.

Transition Metal−Peptide Binding Studied by Metal-Catalyzed Oxidation Reactions and Mass Spectrometry

We have identified conditions that allow metal-catalyzed oxidation (MCO) reactions and mass spectrometry (MS) to correctly identify binding sites of first-row transition metal ions to model peptides. This work extends the applicability of the MCO/MS method to metals other than Cu(II). When the appropriate reducing agent (ascorbate, 10 mM) and oxidizing agent concentrations (1 mM persulfate, atmospheric O2, or both) are used, metal-bound amino acids can be sufficiently and specifically oxidized for clear identification by MS. The MCO reactions with Mn(II), Fe(II), Co(II), and Ni(II) occur to lesser extents than with Cu(II), but oxidation is still extensive enough to allow easy identification of the metal-bound residues. With the exception of aspartic acid, the known metal-binding amino acids of angiotensin I and bacitracin A are oxidized, while no oxidation is observed at nonbinding residues. Failure to oxidize aspartic acid is likely due to the relatively slow reactivity of its carboxylic acid side chain with reactive oxygen species, suggesting that the current MCO/MS protocol is transparent to such acidic residues. Overall, this study indicates that, just as is possible for Cu(II), the MCO/MS method should be suitable for determining the Mn(II)-, Fe(II)-, Co(II)-, and Ni(II)-binding sites of metalloproteins.

Optimization of the preparation conditions of radioiodoepidepride: A dopamine D2receptor antagonist radioligand

[125I]iodepidepride, (s)-(-)-[(1-ethyl-2-pyrrolidinyl)methyl]-5-[125I]-iodo-2,3-dimethoxybenzamide is the iodine substituted analogue of isoremoxipride, both of which are very potent dopamine D2-antagonists. Epidepride was radioiodinated using different oxidizing agents such as chloramine-T, iodogen, iodogen glass frit and hydrogen peroxide. Chloramine-T is a powerful oxidizing agent compared to both iodogen and hydrogen peroxide so that the side products, especially the chlorinated epidepride, decreases the radiochemical yield. This chlorinated epidepride is minimized in the case of iodogen and iodogen glass frit and are not observed in case of the non-chlorinated oxidizing agent hydrogen peroxide. TLC and HPLC were used to analyze the reaction components and to estimate both the radiochemical yield and purity. The reaction parameters such as reaction time, pH, epidepride and oxidizing agent concentrations and the stabilty of the final product were studied to optimize the radiochemical yield and purity. The optimized radiochemical yield was about 90% and the radiochemical purity of the final product was 99.9%.