Presence Of Oxidizing Agent Research Articles

Dissolution of Palladium Metal in Solvent Leaching System with the Presence of Oxidizing Agent

Platinum group metals (PGMs) are important for the manufacture of advanced materials in the field of catalysts and electronic devices. Since the chemical properties of PGMs are very similar to each other, hydrometallurgical processes should be employed to recover PGMs with high purity from either ores or secondary resources. In hydrometallurgical processes for PGMs, the first step is the dissolution of PGMs. For this purpose, inorganic acid solutions with oxidizing agents are generally employed. In this work, nonaqueous solvent leaching systems with a relatively cheap price were employed to investigate the dissolution of pure palladium (Pd) metal. The solvent leaching systems consisted of concentrated hydrochloric acid solution and commercial extractants such as tributyl phosphate (TBP), 7-hydroxydodecan-6-one oxime (LIX 63), and di-n-octyl sulfide (DOS) in the presence of H2O2 as an oxidizing agent. Among the three systems, TBP showed the best efficiency for the dissolution of Pd. The effect of several parameters like TBP concentration, temperature, time, stirring speed and the weight ratio of Pd to TBP/HCl/H2O2 was explored. The dissolution percentage of Pd by the HCl–H2O2–TBP system was higher than by the HCl–H2O–H2O2 system at the same concentration of HCl and H2O2. The role of TBP in enhancing the dissolution of Pd was discussed on the basis of the interaction between HCl and TBP. Compared to aqueous systems, mass transfer is important in the dissolution of Pd metal by the solvent leaching system. Optimum conditions for the complete dissolution of Pd were obtained.

Study of the Stability of Cyanex 301 and its Salts in the Presence of Oxidizing Agents

The effect of oxidizing agents on the stability of bis (2,4,4-trimethylpentyl) dithiophosphinic acid (НR, Cyanex 301) and its extracts with Cu, Ni, Co, and Zn in decane and toluene was studied. It was shown that the stability of НR and extracts varies in the following series of oxidizing agents: HNO3> H2O2> J2. In a mixture of Cyanex 301 with trioctylamine, the oxidation of the extractant is much more effective than with Cyanex 301 alone. The degree of degradation of Cyanex 301 is higher than that of extracts, which indicates a higher stability of НR salts in comparison with the acid itself. The main oxidation products of Cyanex 301 and its extracts (NiR2 and ZnR2) with HNO3, H2O2 and J2 were determined

Synergistic promotion effect of MgO and CeO2 on nanofibrous Ni/Al2O3 catalysts for methane partial oxidation

Ni/Al2O3 catalysts are formed via NiAl2O4 reduction while inactive NiAl2O4 is readily re-formed in the presence of oxidant agent during reactions, such as oxygen in methane partial oxidation. MgO has demonstrated promotion effect through securing Al2O3 to form MgAl2O4 during catalyst calcination so as to diminish NiAl2O4 formation. However, the promotion effect is limited by the formation of NiO-MgO solid solution with low reducibility. CeO2 promotes NiAl2O4 reduction via forming CeAlO3 and therefore prevents NiAl2O4 re-formation during the reaction. This study, for the first time, demonstrates the synergistic promotion effect of MgO and CeO2 on the Ni/Al2O3 catalysts for methane partial oxidation through optimizing MgO and CeO2 contents in the MgO-CeO2-Ni/Al2O3 catalyst system. The thermally stable structure of fibrous catalysts prepared by one-step electrospinning enables the investigation of the synergistic promotion.

Epoxidation of norbornene in the presence of Oxidizing agents

Part1: epoxidation of norbornen and norbornadien in the presence of dimethyloxirane as reagent oxidant has been investigated.Part 2: A general procedure for the epoxidation of norbornen using hydrogen peroxide as the oxidant in the presence of ruthenium trichloride has been investigated. norbornene gave the epoxides at room temperature in good to excellent yield. And epoxy norbornene identified by H-NMR,FT-IR,13C-NMR method spectroscopics

Improved continuity of reduced graphene oxide on polyester fabric by use of polypyrrole to achieve a highly electro-conductive and flexible substrate

A flexible and highly conductive fabric can be applied for wearable electronics and as a pliable counter electrode for photovoltaics. Methods such as surface coating of fabrics with conductive polymers and materials have been developed, but the roughness of fabric is a challenge because it creates discontinuity in the coated layer. The present study first coated polyethylene terephthalate (PET) fabric with reduced graphene oxide sheets; RGO and then filled the gaps with polypyrrole (PPy). The samples were first dipped in graphene oxide (GO) and then reduced to RGO. They were next coated with PPy by in situ polymerization. The results showed that the presence of oxidative agent during synthesis of PPy oxidized the RGO to some extent on the previously RGO-coated samples. PPy was more uniform on samples pre-coated with RGO in comparison those coated with raw PET. The RGO–PPy coated samples exhibited 53% and 263% lower surface resistivity values than samples coated only with PPy and RGO, respectively. There was no significant difference between the tenacity of samples but the bending rigidity of samples increased. The RGO–PPy coated fabric displayed properties, such as excellent UV blocking (UPF=73), antibacterial activity, improved electrochemical behavior and thermal stability which make it a multifunctional fabric.

Characterization of two Lactococcus lactis zinc membrane proteins, Llmg_0524 and Llmg_0526, and role of Llmg_0524 in cell wall integrity

BackgroundDue to its extraordinary chemical properties, the cysteine amino acid residue is often involved in protein folding, electron driving, sensing stress, and binding metals such as iron or zinc. Lactococcus lactis, a Gram-positive bacterium, houses around one hundred cysteine-rich proteins (with the CX2C motif) in the cytoplasm, but only a few in the membrane.ResultsIn order to understand the role played by this motif we focused our work on two membrane proteins of unknown function: Llmg_0524 and Llmg_0526. Each of these proteins has two CX2C motifs separated by ten amino-acid residues (CX2CX10CX2C). Together with a short intervening gene (llmg_0525), the genes of these two proteins form an operon, which is induced only during the early log growth phase. In both proteins, we found that the CX2CX10CX2C motif chelated a zinc ion via its cysteine residues, but the sphere of coordination was remarkably different in each case. In the case of Llmg_0524, two of the four cysteines were ligands of a zinc ion whereas in Llmg_0526, all four residues were involved in binding zinc. In both proteins, the cysteine-zinc complex was very stable at 37 °C or in the presence of oxidative agents, suggesting a probable role in protein stability. We found that the complete deletion of llmg_0524 increased the sensitivity of the mutant to cumene hydroperoxide whereas the deletion of the cysteine motif in Llmg_0524 resulted in a growth defect. The latter mutant was much more resistant to lysozyme than other strains.ConclusionsOur data suggest that the CX2CX10CX2C motif is used to chelate a zinc ion but we cannot predict the number of cysteine residue involved as ligand of metal. Although no other motif is present in sequence to identify roles played by these proteins, our results indicate that Llmg_0524 contributes to the cell wall integrity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-015-0587-1) contains supplementary material, which is available to authorized users.

Real Time Trafficking of System xc− in COS‐7 cells

The cystine/glutamate exchanger, System xc−, is comprised of two proteins, xCT and CD98 and is known to play a significant role in the protective response of cells to oxidative insult. We have previously shown that System xc− activity is rapidly upregulated in the presence of oxidative agents as a result of an increase in trafficking of xCT to the plasma membrane, without an equivalent increase in CD98 membrane localization. Since CD98 has been suggested to be involved in the trafficking xCT, we sought out to monitor the association between xCT and CD98 during this trafficking event. To address this question, we have created three constructs: xCT‐GFP, GFP‐xCT, and mCherry‐CD98 and expressed them in COS‐7 cells. Addition of the GFP tag to either the N‐terminus or the C‐terminus of xCT does not disrupt the basal trafficking of xCT in COS‐7 cells, as 34% of the GFP tagged xCT proteins are localized to the membrane under basal conditions, similar to endogenously expressed xCT. Using live cell fluorescence microscopy, we have observed that while some of GFP‐xCT (or xCT‐GFP) is co‐localized with mCherry‐CD98 on the membrane and within vesicular pools within the cytoplasm, distinct pools of intracellular mCherry‐CD98 and GFP‐xCT do not co‐localize. We are currently monitoring the real time trafficking of xCT‐GFP and mCherry‐CD98 in response to oxidant exposure. This research is supported by NSF‐RUI # 0843564.

Study of Redox-Regulated Transcription Factors in Prokaryotes

Several prokaryotic regulatory proteins that respond to changes in oxygen tension or the presence of oxidative agents have now been identified. The Fnr protein governs the expression of numerous genes during anaerobic growth, both as a transcriptional activator and as a repressor. OxyR protein responds to cellular exposure to H2O2to stimulate transcription of several defense proteins. SoxR protein is triggered by superoxide or nitric oxide to activate a multigene regulon for antioxidant defense and antibiotic resistance. Each of these proteins has been purified and characterized for DNA binding and transcriptional activityin vitro.Fnr, OxyR, and SoxR all seem to respond directly to redox signals generated in the cell, and theirin vitroproperties support this view: Fnr has an oxygen-sensitive [4Fe-4S] center essential for DNA binding; OxyR may be activated via oxidation of a key cysteine residue; and SoxR activation depends on redox-sensitive [2Fe-2S] centers. Basic methods for genetic and biochemical analysis in these systems are presented, with emphasis on detailed methods for SoxR that illustrate general approaches for all the systems.

ChemInform Abstract: New Approaches to the Synthesis of 4,4′‐Bis(phenylglyoxal)benzils in the Presence of Oxidizing Agents on the Basis of DMSO.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Acyl Transfer from S-Monoacyldihydrolipoamide to Benzylamine in the Presence of Oxidizing Agents

Abstract Acyl transfer reaction from N-benzyl-8-S-(p-nitrobenzoyl)dihydrolipoamide to benzylamine was enhanced with oxidizing agents such as cobalt(II) ion or a soluble flavin under an oxygen atmosphere or with di-4-pyridyl disulfide, accompanied by the formation of N-benzyllipoamide.

Iodometric Determination of Iodates, Bromates, or Permanganates in the Presence of Copper. Determination of Copper in the Presence of Oxidizing Agents

Iodometric Determination of Iodates, Bromates, or Permanganates in the Presence of Copper. Determination of Copper in the Presence of Oxidizing Agents