Formation Of Chloride Ions Research Articles

Structure, Adhesion Strength and Corrosion Resistance of Vacuum Arc Multi-Period NbN/Cu Coatings

The influence of deposition modes on the phase-structural state, corrosion resistance, and adhesive strength of vacuum-arc multi-period NbN/Cu coatings is studied. It was found that in thin layers (about 8 nm, in a constant rotation mode), regardless of the change in the pressure of the nitrogen atmosphere, a metastable δ - NbN phase forms (cubic crystal lattice of the NaCl type). At a layer thickness of ~ 40 nm or more, a phase composition changes from the metastable δ - NbN to the equilibrium ε - NbN phase with a hexagonal crystal lattice. In the presence of the ε - NbN phase in the niobium nitride layers, the highest adhesive strength is achieved with a value of LС5 = 96.5 N. Corrosion resistance tests have shown that for all the studied samples the corrosion process has mainly an anodic reaction. The highest corrosion resistance was shown by coatings obtained at a pressure of 7·10-4 Torr, with the smallest bias potential of -50 V and the smallest layer thickness; with a thickness of such a coating of about 10 microns, its service life in the environment of the formation of chloride ions is about a year.

STRUCTURE AND CORROSION RESISTANCE OF VACUUM-ARC MULTI-PERIOD CrN/Cu, ZrN/Cu, AND NbN/Cu COATINGS

The structure and properties of vacuum-arc multi-period composite coatings of the MeN/Cu system (where Me is Cr, Zr, and Nb) are studied. It was found that at the smallest nanolayer thickness (about 8…10 nm) of composites in the layers of all systems, only a phase with an fcc lattice is formed, without a pronounced texture in the nitride layers. For ZrN and CrN, the phases with an fcc lattice are equilibrium, and for NbN, they are nonequilibrium. An increase in the thickness of nitride layers leads to the appearance of a texture in ZrN/Cu and CrN/Cu systems and the formation of an equilibrium ε-NbN phase in the layers of the NbN/Cu system. Tests for corrosion resistance in the environment of the formation of chloride ions showed that the coatings are anodic reaction. The best corrosion properties were obtained for coatings with the smallest layer thickness (about 8…10 nm).

Electro-oxidative decolorization and treatment of model wastewater containing Acid Blue 80 on boron doped diamond and platinum anodes

This paper aims to study the decolorization and degradation of textile dye Acid Blue 80 using indirect electrochemical oxidation on active platinum (Pt) and non-active boron doped diamond (BDD) anodes in the presence and formation of chloride ions. Ultraviolet-visible (UV–VIS) spectroscopy helped to monitor the rate of decolorization in relation to the amount of electrolyte, input voltage as well as current density. The effect of pH on the rate of decolorization was also assessed. Following the decolorization of model wastewater, we monitored the subsequent degradation of Acid Blue 80 by repeatedly measuring the values of total organic carbon (TOC), total nitrogen (TN), chemical oxygen demand (COD) and adsorbable organically bound halogens (AOX). Using liquid chromatography-mass spectrometry (LC-MS), we analyzed the reaction mixture and examined the mechanism of Acid Blue 80 decomposition both with the presence and with the exclusion of chloride ions. In the presence of chloride ions, oxidation was also accompanied by substrate chlorination, along with the formation AOX. Their concentration culminated between 6 and 12 h of electro-oxidation, which was then followed by a decrease in AOX values across the entire pH range of 3.0–11.0. After 24 h, Acid Blue 80 was mineralized by 90% at pH = 3.0 on the BDD anode, coupled with a 99% decrease in COD. Under the same conditions, the Pt anode showed a 94% decrease in COD and 64% in TOC.

Understanding Processes Following Resonant Electron Attachment: Minimum-Energy Crossing Points between Anionic and Neutral Potential Energy Surfaces.

The equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) method with and without a complex absorbing potential (CAP) is applied for the study of the complex potential energy surfaces (CPES) of temporary anions and their parent neutral molecules. Crossings between the anionic state and the neutral state can be connected to the emission of nearly zero-energy electrons, which is demonstrated by the examples of acrylonitrile and methacrylonitrile. We show that the location of the minimum-energy crossing point (MECP) relative to the equilibrium structures of the neutral molecule and the anion can explain experimentally observed peaks on the threshold line of two-dimensional electron-energy loss spectra. The location and energy of the MECP is also crucial in dissociative electron attachment as we illustrate for chloro-substituted ethylenes. It is demonstrated that both the metastable region of the anionic CPES and the crossing with the neutral PES need to be considered to explain trends in the chloride ion formation cross sections of dichloroethylenes.

Radical Chain Reduction of CCl4 Initiated by Illumination of SPEEK Solutions.

Efficient reduction of CCl4 took place upon exposure to 350-nm photons of aqueous solutions containing sulfonated poly(ether etherketone) (SPEEK) as a sensitizer and either poly(vinyl alcohol) (PVA) or HCO2H/HCO2- buffer. The photoreaction formed chloride ions whose concentration increased linearly with time in solutions free of O2, whereas slower reductions occurred in the presence of air. Utilization of formate buffer as the H-atom donor yielded photoreactions at least 10 times faster than those in the presence of PVA and generated CHCl3 as another reaction product. The quantum yield of chloride ion formation, ø(Cl-), was found to be a function of both the SPEEK concentration and concentration of formate buffer. Whereas the quantum efficiency increased steadily with decreasing solution acidity, a drastic surge in the reaction rate occurred in neutral solutions. ø(Cl-) first increased rapidly to a maximum value exceeding 1 at pH 7.3 and then decreased thereafter. The dependence of r(Cl-) on (I0)1/2, where I0 is the light intensity, and the occurrence of postirradiation formation of Cl- through the reduction of CCl4 in the dark are further evidence that the photoreaction proceeded by a chain process. Several of the kinetic features were rationalized by means of a mechanism involving the α-hydroxy radicals of SPEEK and •CCl3 as chain carriers.

Enhanced aerobic degradation of 4-chlorophenol with iron-nickel nanoparticles

In this study, we demonstrate that the bimetallic iron-nickel nanoparticles (nZVIN) possessed an enhanced performance in comparison with nanoscale zero-valent iron (nZVI) on aerobic degradation of 4-chlorophenol (4-CP). The 4-CP degradation rate constant in the aerobic nZVIN process (nZVIN/Air) was 5 times that in the classic nZVI counterpart system (nZVI/Air). Both reactive oxygen species measurement and inhibition experimental results suggested that hydroxyl radicals were the major active species contributed to aerobic 4-CP degradation with nZVI, on contrast, superoxide radicals predominated the 4-CP degradation in the nZVIN/Air process. High performance liquid chromatography and gas chromatography-mass spectrometer analysis indicated the intermediates of the nZVI/Air system were p-benzoquinone and hydroquinone, which were resulted from the bond cleavage between the chlorine and carbon atom in the benzene ring by hydroxyl radicals. However, the primary intermediates of 4-CP found in the nZVIN/Air system were phenol via the direct dechlorination by superoxide radicals, accompanying with the formation of chloride ions. On the base of experimental results, a superoxide radicals mediated enhancing mechanism was proposed for the aerobic degradation of 4-CP in the nZVIN/Air system. This study provides new insight into the role of bimetallic nickel on enhancing removal of organic pollutants with nZVI.

Bacillus mesophilum sp. nov., strain IITR-54T, a novel 4-chlorobiphenyl dechlorinating bacterium.

The taxonomic position of a Gram-positive, endospore-forming bacterium isolated from soil sample collected from an industrial site was analyzed by a polyphasic approach. The strain designated as IITR-54T matched most of the phenotypic and chemical characteristics of the genus Bacillus and represents a novel species. It was found to biodegrade 4-chlorobiphenyl through dechlorination and was isolated through enrichment procedure from an aged polychlorinated biphenyl-contaminated soil. Both resting cell assay and growth under aerobic liquid conditions using 4-chlorobiphenyl as sole source of carbon along with 0.01% yeast extract, formation of chloride ions was measured. 16S rRNA (1,489 bases) nucleotide sequence of isolated strain was compared with those of closely related Bacillus type strains and confirmed that the strain belongs to the genus Bacillus. Strain IITR-54T differs from all other species of Bacillus by at least 2.1% at the 16S rRNA level, and the moderately related species are Bacillus oceanisediminis (97.9%) followed by Bacillus infantis (97.7%), Bacillus firmus (97.4%), Bacillus drentensis (97.3%), Bacillus circulans (97.2%), Bacillus soli (97.1%), Bacillus horneckiae (97.1%), Bacillus pocheonensis (97.1%) and Bacillus bataviensis (97.1%), respectively. The cell wall peptidoglycan contained meso-diaminopimelic acid and the major isoprenoid quinone was MK-7. Major fatty acids are iso-C15:0 (32.4%) and anteiso-C15:0 (27.4%). Predominant polar lipids are diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The results of physiological and biochemical tests allowed the genotypic and phenotypic distinctiveness of strain IITR-54T with its phylogenetic relatives and suggest that the strain IITR-54T should be recognized as a novel species, for which the name Bacillus mesophilum sp. nov. is proposed. The type strain is IITR-54T (=MTCC 11060T=JCM 19208T).

Solar photo-Fenton treatment of carbofuran: Analysis of mineralization, toxicity, and organic by-products

The degradation of the pesticide carbofuran (CBF) using solar photo-Fenton treatment, at both the laboratory and the pilot scale, was evaluated. At the laboratory scale, in a suntest reactor, the Fe2+ concentration and H2O2 concentration were evaluated and optimized using the surface response methodology and the Pareto diagram. Under optimal conditions experiments were performed to evaluate the evolution of the substrate removal, oxidation, subsequent mineralization, toxicity and the formation of chloride ions during the treatment. The analysis and evolution of five CBF by-products as well as several control and reactivity tests at the density functional theory level were used to depict a general scheme of the main degradation pathway of CBF via the photo-Fenton system. Finally, at the pilot scale, a sample of the commercial CBF product Furadan was eliminated after 420 min by the photo-Fenton system using direct sunlight. Under these conditions, after 900 min 89% of toxicity (1/E50 on Vibrio fischeri bacteria), 97% of chemical oxygen demand, and 90% of dissolved organic carbon were removed.

Degradation of dichloroacetic acid in homogeneous aqueous media employing ozone and UVC radiation

A tentative workable mechanism for dichloroacetic acid decomposition (DCA) in aqueous media employing ozone and UVC radiation has been developed. All experiments were made in a homogeneous medium under assured kinetic control regime. Under no circumstances did a headspace exist in the reactor volume. The starting point of the reaction with UVC radiation was always under the prerequisite of a confirmed state of initial equilibrium conditions for the mixture water-ozone-oxygen at 20 °C. The explored variables were: (i) DCA initial concentration, (ii) ozone concentration and (iii) fluence rate at the reactor window. The model comprises three parallel reactions: (1) direct photolysis, (2) direct ozonation and (3) ozone + UVC degradation. Complete DCA removal was achieved, and the mass balance, considering DCA disappearance and chloride ion formation, closed within very small error. The combination of ozone and UVC radiation produces a significant amount of hydrogen peroxide as an important reaction by-product. The direct photolysis can be well represented with a six step reaction sequence. The direct ozonation mechanism comprises 22 steps and, with the entire set of kinetic constants completed in this work, it is independent of the reaction pH in the range from 3 to 6.3. Lastly, the associated use of ozone and UVC radiation becomes necessary to consider the existence of radiation absorption by three species, namely DCA, ozone and hydrogen peroxide. The developed system, including the three parallel reactions, led to the proposal of a 37 step reaction mechanism. Finally the reaction kinetics, the mass balances and the radiation field corresponding to this complex system were rigorously modeled and the most significant features of the mathematical representation are briefly described. The simulation results rendered from this model agree very well with the measured experimental data. This outcome will be essential for deriving a complete reactor model that must be appropriate to describe, in the future, the more practical two-phase operating system.

Frequency effects on the sonochemical degradation of chlorinated compounds

The effects of frequency in chlorobenzene, chloroform, and carbon tetrachloride have been experimentally investigated in this study. The irradiation frequencies were 35, 74, 170, 300 and 1000 kHz. The degradation rates of chlorobenzene, chloroform, and carbon tetrachloride were highest at 300 kHz. The results of between formation of hydrogen peroxide concentration and degradation of chlorinated compounds were not a coincidence. Methods of the sonochemical efficiency were needed to review. The concentration of total organic carbon was remained after 4 h of sonication. High power intensity, longer sonication time, addition of catalysts and combination of the AOP process, were needed for the degradation of TOC. The formation of chloride ion in aqueous solution was evident for the degradation of chlorinated compounds. However, the theoretical concentration of chloride ion was higher than the measured concentration. This means that the remaining chlorinated contaminants in each solution cannot complete dechlorination and some intermediated were produced.

PHOTOCATALYTIC DEGRADATION OF PENTACHLOROPHENOL (PCP) USING IMOBILIZED TiO<sub>2</sub>

Imobilization of titanium plate using titanium diisopropoxide as a precursor, that will be used as a catalyst for degradation of pentachlorophenol (PCP) has been done. In this study 10 ppm of pentachlorophenol (PCP) solution at pH 5 was used as a model of organic polutant. Irradiation was done with and without TiO2 as a catalyst. Sampling was done at interval time of 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, 180, 195, 210, 225 and 240 minutes. Parameter examined after irradiation were the changes of spectrum and pH, the formation of chloride ions and intermediate compounds. The decreased of pH and PCP concentration and the formation of chloride ions and intermediate compounds showed that PCP has already degraded. Keywords: PCP, TiO2, photocatalytic.

Fenton degradation of 4-chlorophenol contaminated water promoted by solar irradiation

The degradation of 4-chlorophenol (4-CP) contaminated water by Fenton process with or without solar irradiation assistance were investigated. It was found that the COD degradation and mineralization efficiency of 4-CP were more than 90% when a 30 min treatment of solar photo-Fenton oxidation process was applied and under an optimum [H 2O 2] 0/[Fe 2+] 0 ratio of 40, the COD degradation and mineralization efficiency increased 65% as compared to Fenton oxidation. Meanwhile, the AOS values increased from −0.33 to 2.13 in solar photo-Fenton process while no significant improvement for AOS values was found in Fenton process, implying a higher degree of oxidation for 4-CP in solar photo-Fenton process. In addition, increasing the intensity of solar irradiation seemed to be beneficial for treatment of 4-CP contaminated water. Formation of chloride ion as a result of mineralization of organically bounded chlorine was identified during the treatment of 4-CP solution. Near-stoichiometric accumulation of chlorine was observed during the degradation of 4-CP in both Fenton and solar photo-Fenton processes. However, accumulation rate of chloride ions were much faster in solar photo-Fenton process. The degradation of 4-CP was found to obey a pseudo-first-order reaction kinetics. As compared to Fenton process, the presence of solar light in photo-Fenton process increases the reaction rate by a factor of 6.5 and 15.8 for COD and TOC degradation, respectively. In other words, during the treatment of 4-CP contaminated water, solar photo-Fenton process possesses notably higher mineralization efficiency in a relatively short radiation time as compared to Fenton process, and could enhance the degradation treatment of refractory organic wastewater such as 4-CP in a cost-effective approach.

Preparation and properties of a new composite photocatalyst based on nanosized titanium dioxide

AbstractThe use of photocatalysts supported on adsorbents is receiving substantial attention. Supporting TiO2 with zeolites is found to be one of the best solutions to increase the efficiency of TiO2-based photocatalysts. This work was focused on simple preparation of a TiO2/Na-ZSM-5 composite catalyst by the solid state dispersion (SSD) method and its modification with an organic photosensitizer — polythiophene (PT). Using the XRD diffractometry, structure of the new composite catalyst was proved. Beside this composite catalyst, mechanical mixtures of TiO2-based catalysts with Na-ZSM-5 zeolite were prepared. The efficiency of all five available photocatalysts (TiO2, TiO2-PT, mechanical mixture of TiO2 + Na-ZSM-5, mechanical mixture of TiO2-PT + Na-ZSM-5, and the modified SSD-PT composite) on photodegradation of 4-chlorophenol was compared. By measuring the formation of chloride ions and decreasing the 4-chlorophenol concentration at two different initial concentrations of 4-chlorophenol in the basic aqueous solution, the photoefficiency and adsorption properties of our photocatalysts were determined.

Trichloroethylene Degradation by Zero Valent Iron Activated Persulfate Oxidation

The present study describes the use of zero valent iron (Fe0 ) as a source for ferrous ion activated persulfate (PS) oxidation of trichloroethylene (TCE). The experimental results indicated that in the absence of TCE there was a lag time for persulfate decomposition when the reaction was activated by Fe0 . An initial pH drop in the Fe0 /PS system to acidic conditions was accompanied by the persulfate decomposition and a decrease in oxidation-reduction potential (ORP) values. Furthermore, in the TCE/Fe0 /PS system, the rapid TCE degradation was accompanied by the rapid persulfate decomposition and chloride ion formation as evidence of TCE mineralization. SEM images of Fe0 before and after persulfate oxidation exhibited significant corrosions of Fe0 . Acicular aggregate formation in the absence of TCE and coarse aggregate formation in the presence of TCE were observed. Moreover, the XRD spectrum revealed the formation of magnetite over the surface of Fe0 after contact with persulfate. Thus, Fe0 activated pe...

Atmospheric Pressure Photoionization Mass Spectrometry of Polyisobutylene Derivatives

Atmospheric pressure photoionization mass spectrometric (APPI-MS) study on three types of polyisobutylene derivatives is reported. Two of the polyisobutylenes investigated were polyisobutylene with dihydroxy and diolefinic end-groups derived from aromatic moieties [dicumyl chloride, 1,4-bis(2-chloro-2-propyl)benzene], and the third contained no aromatic moieties with a monohydroxy end-group. All three polyisobutylene derivatives (PIBs) had an average molecular weight (M(n)) of approximately 2000 g/mol, with a polydispersity lower than 1.2. In the positive ion APPI mode, protonated PIB molecules were formed, but the molecular weights obtained were considerably lower than those expected, indicating fragmentation of the PIB chains. In the negative APPI mode, using solvents such as tetrahydrofuran and toluene as dopants, no signal was obtained. However, in chlorinated solvents, such as CCl(4), CHCl(3), and CH(2)Cl(2), in the presence of toluene dopant, PIB adducts with chloride ions were formed with relatively high signal intensity. In the case of CH(2)Cl(2), no dopant (toluene) was necessary to generate chlorinated adduct ions, albeit increasing the toluene concentration in the flow increased the PIB signal intensity. The effect of the toluene concentration on PIB signal intensity was studied and models that include (1) photoionization of toluene, (2) formation of chloride ions from the chlorinated solvents by dissociative electron capture, (3) formation of chlorinated adduct ions and charge recombination reactions between the toluene radical cation, (4) chloride ions, and (5) chlorinated adduct ions are proposed based on the experimental results.

Removal of thiobencarb in aqueous solution by zero valent iron

A cost-effective method with zero valent iron (ZVI) powder was developed for the purification of thiobencarb (TB)-contaminated water. The removal treatment was performed in the batch system. A sample solution of 10 ml containing 10 μg ml −1 of TB could be almost completely treated by 100 mg of ZVI at 25 °C for 12 h of treatment time. Since the formation of chloride ion in the aqueous solution during the treatment of TB was observed, the removal of TB with ZVI may contain two processes: reduction (degradation) and adsorption. Because the present treatment for TB is simple, easy handling and cheap, the developed technology with ZVI can contribute to the treatment of agricultural wastewaters.

Chain Photoreduction of CCl3F in TiO2 Suspensions: Enhancement Induced by O2

Trichlorofluoromethane (CFC 11) was photoreduced in aqueous suspensions of TiO2 particles containing HCO2- ions and air. Dissolved O2 inhibited the reaction during an induction period that preceded the rapid formation of chloride ions. Reaction rates were higher in systems containing O2 as compared to analogous reactions that occurred in anaerobic suspensions. High photonic efficiencies of Cl- formation (> or =15) were achieved using suspensions with pH > or = 5. As was the case for studies with air-free suspensions, reactions are best described using a photoinitiated chain mechanism that produced CHCl2F and Cl- during the propagation steps. The enhanced yields obtained in the presence of air are attributed to the removal by O2 of electrons trapped in the oxide, which are converted first into H2O2 and then into reducing radicals that participate in the chain process. Enhanced yields of Freon photoreduction were also observed during illumination of air-free suspensions containing hydrogen peroxide, which were interpreted using a similar mechanism.

Enhanced Photocatalysis of Pentachlorophenol by Metal-Modified Titanium (IV) Oxide

The effects of four metals (Ag, Au, Pt, and Cu) doped on TiO2 on the photocatalysis of pentachlorophenol (PCP) were investigated. The results of this study indicated that all four metals-doped TiO2 catalysts were able to enhance the efficiency of PCP photocatalysis with an optimum metallic content of 0.1 wt%. For the metal-doped TiO2 samples (Au, Pt, and Cu), the patterns of light absorption were significantly extended toward visible light spectra in the wavelengths between 400 and 800 nm. The photocatalysis of PCP was pH dependent with the maximum degradation rate achieved in the solution at pH 3. The formation of chloride ion corresponded with the concentration of PCP degraded which confirmed that dechlorination was the major pathway of PCP photocatalysis. The overall toxicities of PCP samples were reduced with the extension of light exposure using the microtox test. The results of PCP photocatalysis are also discussed based on the characteristics of metal/TiO2 including X-ray differential (XRD) patterns, Brunquer Emmett Teller (BET) specific area analysis, and Ultra Violet (UV)-Vis absorption spectra.

Photoelectrocatalytic treatment of pentachlorophenol in aqueous solution using a rutile nanotube-like TiO2/Ti electrode

Taking pentachlorophenol (PCP) as a reference, we investigated the photoelectrocatalytic degradation of organic pollutants using a rutile nanotube-like TiO(2)/Ti film electrode. The nanotube-like TiO2 electrode was prepared by first oxidizing the surface of a titanium sheet to form rutile TiO2 and then treating it to form the tubular structure in NaOH aqueous solution. The occurrence of PCP degradation was indicated by the decrease in pH, concentration of PCP and TOC, and by the formation of chloride ions. The photoelectrochemical (PEC) efficiency of the nanotube-like TiO2/Ti electrode has been determined in terms of degradation of PCP and the incident photo-to-current conversion efficiency (IPCE). The experimental results showed that PCP could be degraded more efficiently by a photoelectrocatalytic process than by a photocatalytic or electrochemical oxidation alone. A significant photoelectrochemical synergetic effect was observed. The kinetic constant of PEC degradation of PCP using a nanotube-like TiO2 electrode was over 60% higher than that using a TiO2 film electrode. It is noted that chloride ion and hydrogen ion concentration increased with irradiation time in the PEC degradation of PCP; PCP was gradually mineralized and the complete minimization of PCP took more time than its degradation.

Some Parametric Studies on Separation of Palladium from Perchloric Acid Medium by Radiolytic Reduction

The radiolytic reduction of palladium ions to palladium metal in perchloric acid solutions has been studied with the aim of separating palladium from aqueous acidic waste. Fraction of Pd separated out as precipitate has been studied as a function of initial Pd concentration and strength of HClO4. Addition of t‐butanol to the system has been found to cause substantial enhancement in the amount of Pd precipitated as compared to that in its absence. At a given absorbed dose, the extent of Pd separated is found to increase with the concentration of HClO4 in presence of t‐butanol. However, the converse is true for the radiolysis in absence of t‐butanol. The decrease in the extent of reduction of Pd(II) to Pd(0) has been found to be due to increasing formation of chloride ions that tend to form reduction resistant cholorocomplexes of Pd. This is supported by the red‐shifting in the absorption bands of Pd(ClO4)2 observed for the spectra of gamma radiolysed solutions of Pd(II) at higher HClO4 concentrations. External addition of chloride ions to aqueous Pd(II)/HClO4 system even in presence of t‐butanol has been found to cause substantial inhibition to the radiolytic reduction of Pd(II) owing to formation of reduction‐resistant complexes. Correspondingly, the addition of nitrate ions to Pd(II)/HClO4/t‐butanol system showed inhibition effect at much greater stoichiometric amount of nitrate.