Aqueous Solution In Presence Research Articles

Effect of montmorillonite clay on the fluorescence resonance energy transfer between two cationic dyes Acridine Orange and Rhodamine B in solution

In this article the Fluorescence resonance energy transfer (FRET) between two important cationic dyes namely Acridine Orange (AO) and Rhodamine B (RhB) in aqueous solution in presence and absence of montmorillonite (MMT) is demonstrated. The energy transfer is also studied in ethanolic solution. Excited state energy migration is occurred from AO to RhB molecules and the extent of energy transfer efficiency linearly increases with increase in RhB concentration in the solution. Interestingly the incorporation of MMT clay significantly increases the energy transfer efficiencies between the dye pair in the solution but the nature of interaction depends on the clay concentrations studied in the present work. The nature of quenching of steady state fluorescence emission of AO in presence of RhB as well as MMT clay in the mixed ensemble is systematically investigated and further confirmed by Time-resolved fluorescence and temperature-dependent steady state fluorescence emission experiments. AO and RhB dye molecules formed ground state complex with MMT clay followed by static quenching. As the clay platelets successfully control the FRET efficiency and it is also well known that MMT clay can host wide diversity of molecular species therefore, the present studies may provide a new insight for the design and the development of FRET-based molecular sensors.

A simple way to prepare palladium nanoparticles decorated with cyclodextrins and ionic liquid. The effects of coating on the catalytic activity and colloidal stability

In this work, palladium nanoparticles (PdNps) were synthesized by reducing palladium chloride with sodium borohydride (NaBH4) aqueous solutions in presence of organic capping ligands such as β-cyclodextrin (βCD), an amphiphilic imidazole-based Ionic Liquid (C12mimBr) and an amphiphilic βCD derivative (βCDMOD14). The results demonstrated that the molecular organization of the capping agents has an important role in the stability of colloidal solution of PdNPs. In particular, the stability of PdNPs coated with βCDMOD14 ([email protected]βCDMOD14) can be controlled by changing the pH of the colloidal suspension. In addition, we propose that during the synthesis of PdNps and capped with C12mimBr ([email protected]12mimBr), the source of palladium is a coordination complex formed due to the presence of C12mimBr. Additionally, we studied the catalytic activity of [email protected]βCDMOD14 and [email protected]12mimBr using the reduction reaction of aromatic nitro compounds to aromatic amine in the presence of NaBH4, as a model in the remediation of aqueous phase. The kinetic data were modeled to the Langmuir–Hinshelwood equation that allows us to discriminate the affinity of 4-NP and NaBH4 towards modified surface of NPs in terms of their association constants (K4-NP, KBH4).

Controlling Fluid Diffusion and Release through Mixed-Molecular-Weight Poly(ethylene) Glycol Diacrylate (PEGDA) Hydrogels.

Due to their inherent ability to swell in the presence of aqueous solutions, hydrogels offer a means for the delivery of therapeutic agents in a range of applications. In the context of designing functional tissue-engineering scaffolds, their role in providing for the diffusion of nutrients to cells is of specific interest. In particular, the facility to provide such nutrients over a prolonged period within the core of a 3D scaffold is a critical consideration for the prevention of cell death and associated tissue-scaffold failure. The work reported here seeks to address this issue via fabrication of hybrid 3D scaffolds with a component fabricated from mixed-molecular-weight hydrogel formulations capable of storing and releasing nutrient solutions over a predetermined time period. To this end, poly(ethylene) glycol diacrylate hydrogel blends comprising mixtures of PEGDA-575 Mw and PEGDA-2000 Mw were prepared via UV polymerization. The effects of addition of the higher-molecular-weight component and the associated photoinitiator concentration on mesh size and corresponding fluid permeability have been investigated by diffusion and release measurements using a Theophylline as an aqueous nutrient model solution. Fluid permeability across the hydrogel films has also been determined using a Rhodamine B solution and associated fluorescence measurements. The results indicate that addition of PEGDA-2000 Mw to PEGDA-575 Mw coupled with the use of a specific photoinitiator concentration provides a means to change mesh size in a hydrogel network while still retaining an overall microporous material structure. The range of mesh sizes created and their distribution in a 3D construct provides for the conditions required for a more prolonged nutrient release profile for tissue-engineering applications.

From gel-like Pickering emulsions to highly ordered superparamagnetic magnetite aggregates with embedded gold nanoparticles

Pickering emulsions with two types of nanoparticles, i.e., superparamagnetic magnetite nanoparticles dispersed in n-hexane and gold nanoparticles dispersed in water, were formed by rigorous mixing in presence of surface active polymeric surfactants. Monodisperse magnetite nanoparticles with a mean particle size of 4 nm were obtained by a microwave-assisted synthesis in n-hexane in presence of oleic acid, and gold nanoparticles were produced in aqueous solution in presence of the hyperbranched poly(ethyleneimine) (PEI) or sodium citrate as reducing and stabilizing agent. After mixing the prepared nanoparticle dispersions in presence of the Pluronics an intermediate gel-like phase is formed. The Pickering emulsion droplets in the intermediate phase are stabilized by both types of nanoparticles, as to be seen by cryo-SEM micrographs. After separating, solvent evaporation and redispersion in water highly ordered Pluronic-stabilized superparamagnetic magnetite nanoparticle aggregates with embedded gold nanoparticles can be obtained.

Aggregation behavior of pluronic F127 solutions in presence of chitosan/clay nanocomposites examined by dynamic light scattering

HypothesisAlthough several researches have explored the dynamics of pluronic aqueous solutions under different conditions, little is known about the dynamical properties of pluronic copolymers in presence of nanoparticles. Knowing and understanding the fundamental dynamical behavior of such systems is crucial to optimize the formulation of high performance multifunctional structures. ExperimentsIn the present work, dynamic light scattering (DLS) is used to investigate the temperature dependence of the dynamical properties of Pluronic F127 aqueous solutions in presence of intercalated chitosan/clay nanocomposites; for comparison, the pluronic aqueous solution and the binary systems pluronic/chitosan and pluronic/montmorillonite having the same copolymer concentration were also investigated. FindingsDLS results show that the pluronic solution is characterized by a fast and a slow diffusion process. The faster diffusion is associated with the unimers interchange between micelles whereas the slower one is ascribed to the presence of micellar clusters that undergo dehydration as the temperature increases. Starting from these observations, the dynamics of the pluronic-based/water systems was analyzed and, depending upon solution temperature, the observed decays were attributed to differently sized entities. The DLS findings give strong evidence for the coexistence of complex states of aggregation allowing us to get a better insight into the architecture of the investigated systems.

An optical fiber based surface plasmon resonance technique for sensing of lead ions: A toxic water pollutant

Abstract Lead is a very toxic element whose presence in aqueous solutions in high concentration levels leads to several undesirable consequences. In this work, we report a detection mechanism of lead ion through an optical method. This SPR based technique measures output response of the sensor probe in terms of voltage of different analytes such as arsenic, copper, cadmium, nickel, mercury, iron and lead. The proposed sensor probe is coated with chitosan and glutathione. It is observed that this sensor probe has good voltage response for lead ions solutions in particular. This technique has limit of detection 1.3 ppb with a sensitivity of 0.28 mV/ppb. Use of optical fiber, LED and photodiode ha made this technique low cost, easily hand able and environment friendly.

Stable All Solid State Z-Scheme Based TiO2/M/CdxZn1-Xs Photo-Catalysts for Efficient Hydrogen Generation

Water splitting to hydrogen and oxygen molecules suing semiconductors as photocatalysts to store solar energy, is one of the “Holy Grails” in solar energy conversion1. The performance of a photocatalyst is largely limited by four requirements: 1) long term stability with respect to photo corrosion, 2) a narrow band gap materials to absorb a large fraction of solar light, 3) suitable band edges that match the redox potential of water, and 4) slow charge carrier recombination systems. In particular, with respect to point 4, many artificial Z-scheme based photocatalytic systems have been widely investigated2. Recently, Rao et al.,3 reported an all-solid state Z-scheme anisotropic ZnO/Pt/Cd0.8Zn0.2S heterojunction system which exhibited a high photocatalytic activity owing to an efficient electron-hole transfer between the ZnO conduction band and the CdS valence band through Pt nanoparticles (using benzyl alcohol and acetic acid as sacrificial reagents). However, this system is not stable over the long term mainly because ZnO is stable in a very narrow pH range (6-8)4, whereas the ideal pH for hydrogen production, either by sacrificial or direct water splitting, is often outside this range. As a consequence, the original Z-scheme structure is gradually destroyed following the dissolution of the ZnO which subsequently causes the decomposition of Cd0.8Zn0.2S. In this work, we have developed a novel TiO2/Ag-Pd/Cd(Zn)S based Z-scheme photocatalytic system. This system was found to be stable in the presence of aqueous solution containing benzyl alcohol/acetic acid (the role of both has been investigated). Catalysts were prepared and characterized by XRD, XPS, TEM and UV-Vis and the catalytic tests were conducted over the complete series of the Z-Scheme system and its individual components such as Ag-Pd/TiO2 and Cd0.8Zn0.2S. The hydrogen generation rate of the best system and that of its components were 3.3 mmol/h.gcatal. (TiO2/Ag-Pd/Cd0.8Zn0.2S), 1.1 mmol/h.gcatal. (Ag-Pd/TiO2) and 0.5 mmol/h.g catal. (Cd0.8Zn0.2S) respectively under identical conditions as described below. Figure 1

Catalytic Effect of Aqueous Solution in Water-Assisted Proton-Transfer Mechanism of 8-Hydroxy Guanine Radical.

Water-assisted proton-transfer process is a key step in guanine damage reaction by hydroxyl radical in aqueous solution. In this article, we quantitatively determine the solvent effect in water-assisted proton-transfer mechanism of 8-hydroxy guanine radical using combined quantum mechanics and molecular mechanism with an explicit solvation model. Atomic-level reaction pathway was mapped, which shows a synchronized two-proton-transfer mechanism between the assistant water molecule and 8-hydroxy guanine radical. The transition-state dipole moment is the largest along the reaction pathway, which electrostatically stabilizes the proton-transfer transition-state complex. The free-energy reaction barrier for this water-assisted proton-transfer reaction was calculated at 19.2 kcal/mol with the density functional theory/M08-SO/cc-pVTZ+/molecular mechanics level of theory. The solvent effect not only has a big impact on geometries, but also dramatically changes the energetics along the reaction pathway. Among the solvent effect contributions to the transition state, the solvent energy contribution is -28.5 kcal/mol and the polarization effect contribution is 19.9 kcal/mol. In total, the solvent effect contributes -8.6 kcal/mol to the free-energy barrier height, which means that the presence of aqueous solution has a catalytic effect on the reaction mechanism and enhances the proton-transfer reactivity in aqueous solution.

The Conversion of Wollastonite to CaCO3 Considering Its Use for CCS Application as Cementitious Material

The reaction of wollastonite (CaSiO3) with CO2 in the presence of aqueous solutions (H2O) and varied temperature conditions (296 K, 323 K, and 333 K) was investigated. The educts (CaSiO3) and the products (CaCO3 and SiO2) were analyzed by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), and differential scanning calorimetry with thermogravimetry coupled with a mass spectrometer and infrared spectrometer (DSC TG/MS/IR). The reaction rate increased significantly at higher temperatures and seemed less dependent on applied pressure. It could be shown that under the defined conditions wollastonite can be applied as a cementitious material for sealing wells considering CCS applications, because after 24 h the degree of conversion from CaSiO3 to CaCO3 at 333 K was very high (>90%). As anticipated, the most likely application of wollastonite as a cementitious material in CCS would be for sealing the well after injection of CO2 in the reservoir.

Catalytic degradation of malachite green in aqueous solution by porous manganese oxide octahedral molecular sieve (OMS-2) nanorods

Preparation of porous manganese oxide octahedral molecular sieves (OMS-2) in presence of different inorganic acids including HF, HNO3, H3PO4, and glacial acetic acid as an organic alternative was investigated. The obtained OMS-2 samples were characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). The OMS-2 sample obtained in presence of HNO3 acted as catalyst in degradation of malachite green (MG) at near-ambient temperature in aqueous solution in presence of NaIO4 as effective oxidant. Under mild reaction conditions, mineralization was completed within 10 min and the recovered catalyst retained activity during at least five successive runs.

Reactions

OPINION Reactions ShareShare onFacebookTwitterWechatLinked InRedditEmail C&EN, 2017, 95 (49), pp 3–4December 18, 2017Cite this:C&EN 95, 49, 3-4(Credit: iStockphoto)Letters to the editor Bird problem In the Nov. 20 issue, herring gull is cited as one of the species that scientists are watching for possible environmental impacts (page 26). However, I have been a birder for over 45 years, and I knew immediately that the photo of the “herring gull” on the cover and in the accompanying article cannot be such. The bird is obviously (to a birder) an adult bird, and thus to be a herring gull would have a larger, thicker yellow bill with a bright red spot on the lower mandible. The bird in this photo, with a thin, small, greenish-colored bill lacking any clear marking (as well as several other factors), is more likely a black-legged kittiwake, a species also mentioned in the article.R. Martin SmithMadison, Wis.Periodate chemistry I read with interest the Oct. 2, 2017, article (page 6) about new studies of aqueous periodate equilibria which found no evidence for metaperiodate (IO4–) in aqueous solution. Kinetics studies tell a different story. Two independent temperature-jump studies (J. Phys. Chem. 1964, DOI: 10.1021/j100794a057; Z. Naturforsch., B: J. Chem. Sci. 1977, DOI: 10.1515/znb-1977-0127) and a corroborating 17O NMR line-broadening study (J. Am. Chem. Soc. 1965, DOI: 10.1021/ja01096a008) indicate the existence of a rapid meta-orthoperiodate hydration-dehydration equilibrium in acidic media.The equilibrium and kinetics studies are not necessarily in conflict, however. The equilibrium study of Horváth and colleagues indicates that orthoperiodate predominates in aqueous solution over a wide range of pH values (Inorg. Chem. 2017, DOI: 10.1021/acs.inorgchem.7b01911). The equilibrium quotient for formation of metaperiodate is much smaller than had been generally accepted in previous kinetics studies. Metaperiodate, though present at low concentrations, insufficient to be unambiguously detected in equilibrium studies, can manifest its presence in aqueous solution. For example, the subtle role of this species is in accordance with ... [an] independent kinetics study reported on complex formation of an iron(III) hydroxo dimer with periodate ion (Dalton Trans. 2004, DOI: 10.1039/B313341A).Kenneth KustinChapel Hill, N.C.Women in chemistry Bibiana’s editorial in the Nov. 13 issue on the giants of chemistry (page 2) connected well with my current reading. My oldest daughter, upon graduating from college, was given this book by a classmate: “Nobel Prize Women in Science” (Carol Publishing Group, 1993) by Sharon Bertsch McGrayne. My daughter left the book with her old man when she moved on. Beginning with Marie Curie and followed by Lise Meitner, the book takes the reader through biographies of 11 additional Nobel Prize-winning women and their respective struggles to compete in the male-dominated scientific communities during much of the 20th century. The book aptly describes what each accomplished scientifically and how each overcame great gender discrimination obstacles. Eve Curie’s “Madame Curie” (Da Capo Press, 1937) is a great resource on the life of her famous mother. A paperback copy updated in 2001 is readily available. In 2012, I offered a lifelong learning course over four evenings on the life and accomplishments of Madame Curie at Michigan State University. This course was well attended.Paul R. Loconto Okemos, Mich. ACS 2016 IRS FORM 990 AVAILABLE The American Chemical Society’s 2016 IRS Form 990 is now available on the ACS website. To access the information, go to www.acs.org/acsirsform990. Please scroll toward the bottom of the page to access the 2016 form and related “Guide to Schedule J” for explanatory information regarding ACS executive compensation. If you have any access problems, please contact service@acs.org.

Synthesis and crystal structure of N,N-dimethylformamide solvate of thiocyanuric acid

Considerable attention has been paid recently to crystal engineering; which involves the design and preparation of new crystalline molecular solids with desired properties [1–4]. Crystalline materials with specific properties find applications in petrochemical industry for separation and purification. Moreover, crystal engineering provides products designed for manufacturing catalysts and high-valued chemicals for specific purposes. Recently, crystalline materials find application in pharmaceutical, food and microelectronic industries [5]. The main two strategies that are used for crystal engineering are based on hydrogen bonding and coordination bonding [6]. Since the hydrogen bonding is usually stronger and more directional than the other methods, more new crystal materials have been prepared based on this method. We are here able to design crystalline materials based on hydrogen bonding and study their solid state structures. N, N-dimethylformamide (DMF)-solvate of thiocyanuric acid (TCUA) and dimethyl sulfoxide (DMSO)-solvate of thiocyanuric acid (TCUA) were successfully prepared at room temperature in the presence of aqueous solution of sodium nitrate (NaNO3). To the best of our knowledge, this study presents the easy, modest, and rapid method to prepare co-crystal formation based on thiocyanuric acid (TCUA) and solvent-containing hydrogen bonding functionality. In this paper, we present the most effective method to synthesize the co-crystals of (TCUA), and as evidence, the crystal structure of (TCUA) in DMF is fully studied and presented in this paper. The N,N-dimethylformamide (DMF)-solvate of thiocyanuric acid (TCUA) was successfully prepared at room temperature, and was characterized spectroscopically by nuclear magnetic resonance (NMR) and single-crystal X-ray diffraction (SXRD). The asymmetric unit of the title compound contains one molecule of thiocyanuric acid (TCUA) features an almost planar six-membered ring having exocyclic C-S thione double bonds and one molecule of N,N-dimethylformamide (DMF). It was crystallized in the monoclinic, P21/c with unit cell parameters of a = 9.6255 (4) Å, b = 12.6864 (5) Å, c = 9.1367 (4) Å, β = 90.095 (2)°, V = 1115.71 (8) Å3, Z = 4. The structure is composed of 1-D TCUA ribbons formed via N–H–S hydrogen bonds. The ribbons are separated by DMF molecules, which are bridged to the ribbons by N–H–O hydrogen bonds. The ribbons and their DMF molecules form 2-D sheets which are in turn π-stacked to build up a layered, 3-D structure. The proton and carbon-13 NMR studies confirmed the formation of such solvate between DMF and TCUA.

Hollow Iridium-Based Catalysts for the Oxygen Evolution Reaction in Proton Exchange Membrane Water Electrolyzers

The performance of Proton Exchange Membrane Electrolyzers (PEMWE) is mostly impeded by the efficiency of the anode catalysts allowing for the Oxygen Evolution Reaction (OER) to occur. New catalytic materials should possess at least as high performance and stability as state of the art materials, since the price of electrolysis is mostly impacted by the price of electricity and higher overpotentials would render the catalysts not viable for application in PEMWE. The use of noble metal at the anode for the OER is at the current stage essential due to the highly oxidative and strongly acidic environment. Nevertheless, due to cost and resources considerations, it is necessary to reduce the noble metal content. In addition, according to present industrial requirements, PEMWE cells should be able to work at very high current density and under high pressure. Water and gases management are also a major challenge in PEMWE catalyst layers, and unlike in fuel cells or PEMWE cathodes the use of a cheap carbon based porous support for electronic conduction at the anode is highly undesirable due to highly anodic potential. We have developed a cheap, clean and easily scalable synthesis method to produce highly porous iridium-based materials. The materials are synthesized in aqueous solutions in presence of a porogen. The resulting material is further calcinated to remove the porogen and initiate crystallization of the inorganic phase. By adjusting reactant concentrations and calcination conditions, metallic iridium, iridium oxide or mixed oxides can be obtained. This last point is of high importance since in addition to reducing noble metals content compared to current technologies, the atomic neighborhood of dissimilar metals is expected to modify the monometallic behavior and potentially gives rise to new desired characteristics, i.e.to decrease the OER overpotential and/or increase the material stability. Structural characteristics and chemical composition of the materials have been determined using XRD, XPS and XRF. The influence of the thermal treatment has a strong impact on the crystallite size and the composition of the particle surface. SEM-FEG and BET characterizations have shown that the type of the porogen used for material synthesis directly impacts its morphology and porosity. To assess the catalytic performances of these hierarchically porous materials, a screening of the electrocatalytic activity of a series of prepared materials has been performed using a three-electrodes electrochemical setup. The optimized material shows lower overpotential than commercial Ir or IrO2 nanoparticles as shown on the figure thereafter. Finally, selected materials have been used to prepare anode catalyst layers and have been tested in a complete electrolysis device. With a loading of 2 mg cm-2 in Iridium, a potential of 1.65 V at 1 A cm-2 and of 1.85 V at 2 A cm-2 is obtained. The produced specific morphologies are very well adapted to the formation of porous percolating networks, which promote gases and water transport throughout the catalyst layer. Figure 1

Thermodynamic modeling of equilibrium conditions of CH4/CO2/N2 clathrate hydrate in presence of aqueous solution of sodium chloride inhibitor

ABSTRACTIn this work, the effect of sodium chloride (NaCl) on thermodynamic properties of CH4+CO2+N2 hydrate formation and equilibrium condition has been studied. The three-phase (hydrate–liquid–gas) equilibrium calculation has been carried out using the Peng–Robinson equation of state (PR EoS) and Universal Quasi Chemical (UNIQUAC) activity coefficient models. The PR EoS coupled with classic mixing rule is applied for the vapor phase. The calculations of the gas hydrate formation pressures are performed in the absence and presence of sodium chloride inhibitor for the gas hydrate systems. The Chen–Guo model has been used for the hydrate phase and the UNIQUAC activity coefficient is applied for non-ideality of the liquid phase. To obtain higher accuracy, the solubility of the gases in the aqueous phase is also taken into account using pressure corrected Henry's law. Finally, the stepwise procedure has been followed to obtain the results and compared with the experimental results. The addition of 2% (by volume) sodium chloride to water results in large shifts in phase equilibrium boundary to increase pressure for the same temperature condition.

Removal Efficiency of Cu2+, Zn2+, Fe2+, Al3+ and Mn2+ from Aqueous Solution in Presence of Bentonite Using Column Adsorption

Removal Efficiency of Cu2+, Zn2+, Fe2+, Al3+ and Mn2+ from Aqueous Solution in Presence of Bentonite Using Column Adsorption

Investigation on ionic states of 1,2-Dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC) using organic laser dyes: A FRET study

Fluorescence Resonance Energy Transfer (FRET) between two organic dyes Fluorescein and Rhodamine 6G were successfully investigated in aqueous solution in presence and absence of 1,2-Dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC) at different pH. Spectroscopic studies suggest that both the dyes were present mainly as monomer in solution. FRET occurred from Fluorescein to Rhodamine 6G in solutions. Energy transfer efficiency increases in presence of DPPC and the maximum efficiency was 59.3% when the concentration of DPPC was 1.4×10−4M at ambient condition. pH plays a crucial role in this investigation as the energy transfer efficiency was found to change in presence of DPPC at different pH. It has been demonstrated that with proper calibration it is possible to use the present system under investigation to realize various ionic states of DPPC by observing the change in FRET efficiency between these two dyes.

FERROCENYL ALKYLAMMONIUM N-SUBSTITUTED POLYPYRROLE CONTAINING Pt AND Pd AND ITS APPLICATION ON ELECTROANALYSIS OF ARSENITE

Arsenic occurs in a variety of forms and oxidation states and is a very toxic element. The main inorganic arsenic species present in natural waters are arsenate (oxidation state V) and arsenite ions (oxidation state III). Arsenite is more toxic and mobile than arsenate. Therefore, it is important the development of new materials for analysis and control of these toxic species. This research proves that polymer-metal composite electrode materials synthesized by incorporation of Pt0 and Pd0 nanoparticles into a poly(pyrrole-ferrocenyl alkylammonium) matrix present electrocatalytic properties towards the oxidation of arsenite to arsenate. The polymer films displayed a stable electrochemical response in aqueous solution. However, when the polymer film modified electrode were transferred to aqueous solution in presence of arsenite anions, the CV curves for polymer films were deeply modified by the decrease in the electroactivity of the film. It can be concluded that the cationic polymer films present a strong affinity toward arsenite anions. The composite films containing Pt0 or Pd0 showed catalytic activity towards oxidation of As(III) to As(V) due to the presence of metal catalyst particles into the polymer films.

Behavior of 9Ni Steel in the Presence of Aqueous Solutions Containing CO2 and H2S

This paper presents the corrosion test results of 9%Ni steels (ASTM A522 type 1 and ASTM A333 grade 8) in presence of aqueous solutions containing H2S and CO2. A forged bar and a seamless pipe, manufactured to be used in high-pressure CO2 lines, were tested by NACE TM0177, TM0284, and ISO 7539-2. Localized corrosion and cracks were observed in the sulfide stress cracking (SSC) tests, in both base materials, and welded joint. These types of attack were associated to specific metallurgical features of the products (forged bar and seamless pipe), indicating that a better evaluation of the corrosion resistance of these materials is necessary. No hydrogen induced cracking damage was detected after the standard testing time, but microcracks were identified, reducing the impact energy levels. The welded joint presented high susceptibility to SSC cracking.

A new method for producing substituted anthraquinones via diene synthesis in the presence of Mo-V-P heteropoly acid solution: Catalyst regeneration

The possibilities of developing catalytic processes for the synthesis of 2-methylanthraquinone from 1,4-naphthaquinone (NQ) and isoprene, and synthesizing 2,3-dimethylanthraquinone from NQ and 2,3-dimethylbutadiene in the presence of aqueous solutions of high-vanadium heteropoly acid (HPA) as a bifunctional catalyst are examined. Two methods for catalyst regeneration are discussed: oxidation with oxygen at \({P_{o{}_2}}\) = 0.3–0.4 MPa and with concentrated nitric acid at atmosphere pressure. It is shown that regeneration with nitric acid ensures deeper oxidation of the reduced catalyst. Complete restoration of the properties of the catalyst following regeneration offers the possibility of its repeated use in the processes discussed in this work.

Application of Graphene Nanoparticles in Removal of Fluoride from Aqueous Solution in Presence of Sulfate Anion

Application of Graphene Nanoparticles in Removal of Fluoride from Aqueous Solution in Presence of Sulfate Anion