Direct analysis of oxidizing agents in aqueous solution with attenuated total reflectance mid-infrared spectroscopy and diamond-like carbon protected waveguides

A novel approach for the direct detection of oxidizing agents in aqueous solution is presented using diamond-like carbon (DLC) protected waveguides in combination with attenuated total reflectance (ATR) mid-infrared spectroscopy. Pulsed laser deposition was applied to produce high-quality DLC thin films on ZnSe ATR crystals with thicknesses of a few 100 nm. Scanning electron microscopy and X-ray photoelectron spectroscopy has been used to investigate the surface properties of the DLC films including the sp(3)/sp(2) hybridization ratio of the carbon bonds. Beside excellent adhesion of the DLC coatings to ZnSe crystals, these films show high chemical stability against strongly oxidizing agents. IR microscopy was utilized to compare differences in the chemical surface modification of bare and protected ATR waveguides when exposed to hydrogen peroxide, peracetic acid, and peroxydisulfuric acid. The feasibility of DLC protected waveguides for real-time concentration monitoring of these oxidizing agents was demonstrated by measuring calibration sets in a concentration range of 0.2-10%. Additionally, principal component regression has been applied to analyze multicomponent mixtures of hydrogen peroxide, acetic acid, and peracetic acid in aqueous solution. Due to high chemical stability and accurate monitoring capabilities, DLC protected waveguides represent a novel approach for directly detecting oxidizing agents in aqueous solution with promising potential for industrial process analysis.     

Fracture of nanoporous thin-film glasses

Fracture of nanoporous thin-film glasses is a significant challenge for the integration of these mechanically fragile materials in emerging microelectronic and biological technologies. In particular, the integration of these materials has been limited by accelerated cracking rates in moist environments leading to premature failure. Here, we demonstrate how cracking is affected by aqueous solution chemistry, and reveal anomalously high crack-growth rates in hydrogen peroxide solutions frequently encountered during device processing or when in use. Kinetic mechanisms involving the transport and steric hindrance of reactive hydrogen peroxide molecules at the crack tip are proposed. Thin-film design strategies that involve energy dissipation by local plasticity in thin ductile layers on increasing the resistance to cracking of nanoporous glass layers is demonstrated. Understanding how aqueous solutions influence cracking and associated device reliability is a fundamental challenge for these promising materials to be viable candidates for new technologies.     

Degradation of bisphenol A and formation of hydrogen peroxide induced by glow discharge plasma in aqueous solutions

Degradation of bisphenol A (BPA) and simultaneous formation of hydrogen peroxide induced by glow discharge plasma in contact with aqueous solution were investigated. Experimental results indicated that the BPA degradation rate was higher in sodium chloride solution than that in sodium sulfate or phosphate solutions. However, the formation rates of hydrogen peroxide were on the opposite case. Both the BPA removal and the hydrogen peroxide production rates decreased in the presence of hydroxyl radical scavengers, indicating that hydroxyl radicals are the most probable oxidants responsible for BPA degradation and the precursors of hydrogen peroxide. Ferric ion showed better catalytic effect than that of ferrous ion, suggesting that the ferric ion was reduced by the intermediates formed during BPA degradation, which was confirmed by following the production of ferrous ion in the system. TOC of the solution gradually reduced with discharge time; however, without catalysts, the solution COD increased with discharge time and sharply decreased in the presence of iron salts. The major intermediate products were identified by LC/MS and the possible degradation mechanism was discussed.     

Ozonation and H2O2/UV treatment of clofibric acid in water: a kinetic investigation

The presence of pharmaceuticals or their active metabolites in surface and ground waters has been recently reported as mainly due to an incomplete removal of these pollutants in sewage treatment plants (STP). Advanced oxidation processes may represent a suitable tool to reduce environmental release of these species by enhancing the global efficiency of reduction of pharmaceuticals in the municipal sewage plant effluents. The present work aims at assessing the kinetics of abatement from aqueous solutions of clofibric acid (a metabolite of the blood lipid regulator clofibrate) which has been found in surface, ground and drinking waters. Ozonation and hydrogen peroxide photolysis are capable of fast removal of this species in aqueous solution, with an almost complete conversion of the organic chlorine content into chloride ions for the investigated reaction conditions. A validation of assessed kinetics at clofibric acid concentrations as low as those found in STP effluents is presented for both systems.     

Photochemical treatment of phenol aqueous solutions using ultraviolet radiation and hydrogen peroxide

The potential of purifying phenol aqueous solutions (0.0006-0.0064 M) using ultraviolet (UV) radiation and hydrogen peroxide (H2O2; 0.005-0.073 M) was investigated. Although the direct photolysis of phenol and its oxidation by hydrogen peroxide (without ultraviolet light) were insignificant, the combination of UV and H2O2 was extremely effective on phenol degradation. However, the chemical oxygen demand was on no occasion entirely eliminated, indicating the resistance of the intermediate products formed to the photo-oxidation. Increasing the initial concentration of phenol had as a result lower phenol conversions achieved, whereas the increase in hydrogen peroxide initial concentration enhanced significantly the degradation of phenol. In contrast, COD removal was less sensitive to these changes.     

Some properties of aqueous titanium isopropoxide-hydrogenperoxide solutions and their decomposition to produce titanium dioxide

The preparation of aqueous titanium isopropoxide-hydrogen peroxide solutions, their light absorption spectra, optical density changes based on the transformation to colloids, thermal analysis of the dry colloids to titanium dioxide and the spontaneous explosions of the residues produced after vacuum evaporation of the solutions transforming titanium dioxide powders, were studied. The solutions were prepared by dissolving titanium tetra isopropoxide in an aqueous hydrogen peroxide solution. Component isopropanol was expelled from the mixture by vacuum evaporation. The presence of various H₂O₂/Ti ratios of residues produced by the evaporation, and the variation of absorption spectra with the concentration of hydrogen-peroxide suggested that the hydrogenperoxide content in the solute species was determined by the concentration of hydrogen peroxide in them. The thermal analysis of the dry colloids revealed that they suddenly decompose exothermally and consist of titanium, water and hydrogenperoxide. X-ray powder diffraction revealed that the dry colloid was amorphous and the heated product of the colloid at 440°C was in the anatase form and also that the explosion products were the same. SEM revealed that the fine dry colloid deformed above 609°C.     

Potential of far-ultraviolet absorption spectroscopy as a highly sensitive quantitative and qualitative analysis method for aqueous solutions, part I: determination of hydrogen chloride in aqueous solutions

This paper reports the usefulness of far-ultraviolet (FUV) absorption spectroscopy in highly sensitive quantitative and qualitative analysis of aqueous solutions. We propose a totally new idea for the utilization of FUV spectroscopy in pure water and aqueous solution analyses. We use an absorption band near 170 nm due to an n --> sigma* transition of water. The intensity of the foot of this band, which can be observed in the 190-210 nm region by use of an ordinary ultraviolet-visible (UV-Vis) spectrometer, is very sensitive to changes in hydration and hydrogen bonds of water. To demonstrate the potential of FUV spectroscopy in analytical chemistry, we undertook three kinds of experiments. The first one is concerned with the discrimination of eight kinds of commercial natural mineral water. The eight kinds of mineral water can be discriminated straightforwardly from the spectral patterns in the 190-250 nm region without any spectral pretreatment or spectral analysis such as multivariate analysis. The second experiment is the determination of hydrogen chloride (HCl) in aqueous solutions. FUV spectra of aqueous solutions of HCl over a concentration of 0-20 ppm were measured. A calibration model for predicting the concentration of HCl in the aqueous solutions was developed based on the absorbance at 193 nm. This method does not require any spectral pretreatment or multivariate analysis. The correlation coefficient and standard error of prediction of the calibration model developed are 0.9987 and 0.18 ppm, respectively. The detection limit of the proposal method for the determination of HCl in aqueous solutions was estimated to be 0.5 ppm (13.7 microM). The determination of HCl was also tried for natural mineral water to which HCl solutions with the concentrations of 2, 4, 6, 8, 12, 16, and 20 ppm were artificially added. The third study was the determination of ammonia (NH3) and hydrogen peroxide (H2O2) in aqueous solutions containing both NH3 and H2O2. It has been found that the present method is also useful for the determination of the two-component system.     

Gas-Assisted IR-ATR Probe for Detection of Volatile Compounds in Aqueous Solutions

The application of the principle of solid-phase microextraction (SPME) to attenuated total reflectance (ATR) infrared (IR) probes can provide a convenient and sensitive way to detect volatile organic compounds (VOCs) in aqueous solutions. In this paper a new method to increase the performance of this type of sensing device is proposed. A stream of gas purges out VOCs from aqueous solution. These compounds are directed to an internal-reflection sensor. Several advantages are recognized by this new method as compared with a conventional liquid probe; these include a longer lifetime for the probe, higher selectivity in the detection of VOCs, less limitation in the sample volume, and easier regeneration of the sensing probe.     

The formation and influence of hydrogen peroxide during ozonation of para-chlorophenol

Hydrogen peroxide was detected during the ozonation of para-chlorophenol (4-CP) in aqueous solutions. Its formation and influence on the reaction mechanism were examined. Semi-batch experiments showed that hydrogen peroxide was formed during the direct reaction between molecular ozone and 4-CP. The detected hydrogen peroxide could reach 12.3% of the initial mole concentration of 4-CP. Hydrogen peroxide reacts with ozone in neutral pH and leads to the appearance of the powerful oxidant, OH* radicals. An O(3)/OH* probe compound, succinate was then developed, and also included in the 4-CP solution matrix. The disappearance of succinate with time shows the amount of OH radicals. With enough tert-butanol inhibiting the OH* radical oxidation, results showed that 4-CP was transformed to para-quinone by ozone, and subsequently destroyed to formic acid and oxalic acid. Without scavengers of inactivation the OH* radicals, 4-CP was destroyed to low molecular weight acid.     

Photochemical treatment of 2-chlorophenol aqueous solutions using ultraviolet radiation, hydrogen peroxide and photo-Fenton reaction

In the present work, the photochemical oxidation of 2-chlorophenol aqueous solutions in a batch recycle photochemical reactor using ultraviolet irradiation and hydrogen peroxide was studied. Specifically, the effect of hydrogen peroxide initial concentration (0-10316 mg L(-1)) and 2-chlorophenol initial concentration (150-3000 mg L(-1)) was examined. The process was attended via total organic carbon (TOC), 2-chlorophenol, chloride ion, acetic acid, formic acid and pH measurements. The conversion of 2-chlorophenol observed was always much higher than the corresponding total organic carbon removal, whereas the increase in hydrogen peroxide amount in the solution led to higher values of 2-chlorophenol conversion and total organic carbon removal. Finally, the photo-Fenton reaction was applied to the oxidation of 2-chlorophenol, leading to a higher degree of mineralization of the parent compound.     

Preparation of vermiculite nanoparticles using thermal hydrogen peroxide treatment

Powdered natural Mg-vermiculite (Letovice, Czech Republic), with the formula (Mg0.35K0.02Ca0.01) (Mg2.39Fe0.51(3+)Fe0.02(2+)Al0.08) (Si2.64Al1.33Ti0.03) O10(OH)2 x 4.97H2O and particle size < 5 microm, was used for the investigation of exfoliation after hydrogen peroxide and/or microwave treatment (600 W). A sample heated in the microwave oven for 40 min exhibits a 11% mass loss and reduction of the 001 peak intensity in the X-ray diffraction pattern. The basal 001 peak intensity of untreated Mg-vermiculite sample (/001 = 100%) drops to 35% in the microwave treated sample. Only the sample treated for 5 h at 80 degrees C fully rehydrated after 120 min at room temperature. A more pronounced reduction of the 001 peak intensity (to 8%) was observed after hydrogen peroxide treatment of the sample at 25 degrees C. The combination of a five-hour hydrogen peroxide treatment at 80 degrees C and subsequent microwave heating leads to an effective extinction of the 001 diffraction in the XRD pattern. The 001 diffraction profile becomes very diffuse with peak intensity less than 1%. The degree of reduction of the 001 diffraction intensity also depends on the time and temperature of hydrogen peroxide treatment and on the peroxide concentration. An even more pronounced reduction of the peak intensity is caused by exfoliation of particles to nano-domains coupled with a randomization of the c-axes.     

Physicochemical principles of the decontamination and utilization of arsenic-containing waste

Thermodynamic computer simulation of heterogeneous multicomponent systems containing arsenic(III), arsenic(V), and calcium chlorides, hydrochloric acid, nitric acid, hydrogen peroxide, and oxygen is carried out for temperatures of 25–100‡C. The solute state of arsenic is found to influence the fugacities of arsenic trichloride and hydrogen chloride. Arsenic(III) oxidation in chloride solutions and distillation of arsenic-containing solutions in the presence of oxidants are studied experimentally to determine conditions for a rapid and virtually complete oxidation of arsenic in chloride solutions by nitric acid, ammonium nitrate, and hydrogen peroxide.     

Integrated optical attenuated total reflection spectrometry of aqueous superstrates using prism-coupled polymer waveguides

Attenuated total reflection (ATR) spectrometry of aqueous solutions in contact with polystyrene integrated optical waveguides has been investigated. The mode-dependent absorption of evanescent energy by fluorescein solutions adjacent to the waveguide surface was measured and compared to theoretical predictions based on a ray optics approach. Although enhanced sensitivity was observed with increasing mode number, the sensitivity for the highest order mode was less than that predicted by theory.     

Decolorization of Acid Orange 7 solution by gas-liquid gliding arc discharge plasma

The decolorization of 180 microM aqueous solutions of Acid Orange 7 (AO7) by means of a non-thermal plasma technique (i.e., the gas-liquid gliding arc discharge, which is generated between at least two metal electrodes with AC high voltage) was investigated in this paper. The effects of the plasma treatment time and the type of feeding gas, including air, oxygen, nitrogen and argon of the dye removal were determined. It is found that the voltage cycles of the gas-liquid gliding arc discharge are characterized by a moderate increase in the tension which is represented by a peak followed by an abrupt decrease and a current peak in the half period (10 ms); the concentration of AO7 solution decreases exponentially to reach 58.9, 77.4, 89.1, 95.1 and 99% in 25, 50, 75, 100 and 125 min, respectively, and the ln(Ct/C0) varies linearly with the treatment time t, indicating that decolorization reaction follow first pseudo-order kinetics with a constant rate of 0.03327 min(-1) when air was used as feeding gas; the decolorization rate during the plasma treatment is the greatest for oxygen as the feeding gas, in turn followed by air and argon, and was the least when using nitrogen. The variations of pH and conductivity and the formations of hydrogen peroxide and ozone are measured.     

Characterization of zirconium, lanthanum and lead oxide deposits prepared by cathodic electrosynthesis

Cathodic electrosynthesis of zirconium, lanthanum and lead oxides was performed from aqueous solutions of ZrOCl₂ · 8H₂O, La(NO₃)₃ · 6H₂O and Pb(NO₃)₂, respectively. The deposits were characterized by X-ray diffraction, thermogravimetric and differential thermal analyses. Crystallite sizes of zirconia were derived at different temperatures from X-ray broadening data. The influence of hydrogen peroxide on the electrosynthesis process, crystallization and phase evolution of deposits has been studied. A possible mechanism of electrosynthesis and the role of hydrogen peroxide are discussed.     

Enhanced electrochemical detection performance of multiwall carbon nanotubes functionalized by aspartame

Inexpensive, non-toxic, and biocompatible materials that can disperse multiwall carbon nanotubes (MWCNTs) in aqueous solutions through a non-covalent approach while retaining their unique electronic and photonic properties are highly preferred. In this article, we introduce the use of an amphiphilic dipeptide derivative, aspartame, as an effective dispersing agent in preparing highly stable suspensions under ultrasonication. The results demonstrate that aspartame was absorbed by the nanotube surface possibly because of non-covalent π–π stacking between the aromatic group of aspartame and the CNT backbone. In addition, the resulting MWCNT/aspartame composites remained stably dispersed over a wide range of pH values. The chronoamperometric measurements of MWCNT/aspartame composite-coated electrodes for hydrogen peroxide demonstrated better electrochemical detection performance, as characterized by significantly enhanced step current, higher sensitivity, and reduced potential compared with bare electrodes.     

负载新型酞菁纤维素纤维的制备及催化氧化性能

首先采用丁二酸酐和顺丁烯二酸酐改性氨基钴酞菁制得两种新型水溶性钴酞菁,然后将这两种新型水溶性钴酞菁负载到纤维素纤维上,制得新型高分子催化剂,并选用巯基乙醇和H2O2作为底物来考察负载酞菁纤维素纤维的催化氧化活性。实验结果表明,两种高分子催化剂对巯基乙醇具有良好的催化氧化活性和催化分解H2O2的能力。     

Assessment of Fenton's reagent and ozonation as pre-treatments for increasing the biodegradability of aqueous diethanolamine solutions from an oil refinery gas sweetening process

The aim of this work was to evaluate the efficiency of three chemical oxidation processes for increasing the biodegradability of aqueous diethanolamine solutions (aqueous DEA solutions), to be used as pre-treatments before a biological process. The raw aqueous DEA solution, sourced from a sour gas sweetening plant at a Mexican oil refinery, was first characterized by standardized physico-chemical methods. Then experiments were conducted on diluted aqueous DEA solutions to test the effects of Fenton's reagent, ozone and ozone-hydrogen peroxide on the removal of some physicochemical parameters of these solutions. Lastly, biodegradability tests based on Dissolved Organic Carbon Die Away OECD301-A, were carried out on a dilution of the raw aqueous DEA solution and on the treated aqueous DEA solutions, produced by applying the best experimental conditions determined during the aforementioned oxidation tests. Experimental results showed that for aqueous DEA solutions treated with Fenton's reagent, the best degradation rate (70%) was obtained at pH 2.8, with Fe(2+) and H(2)O(2) at doses of 1000 and 10,000 mg/L respectively. In the ozone process, the best degradation (60%) was observed in aqueous DEA solution (100 mg COD/L), using 100 mg O(3)/L at pH 5. In the ozone-hydrogen peroxide process, no COD or DOC removals were observed. The diluted spent diethanolamine solution showed its greatest increase in biodegradability after a reaction period of 28 days when treated with Fenton's reagent, but after only 15 days in the case of ozonation.     

Bistatic SAR ATR

With the present revival of interest in bistatic radar systems, research in that area has gained momentum. Given some of the strategic advantages for a bistatic configuration, and technological advances in the past few years, large-scale implementation of the bistatic systems is a scope for the near future. If the bistatic systems are to replace the monostatic systems (at least partially), then all the existing usages of a monostatic system should be manageable in a bistatic system. A detailed investigation of the possibilities of an automatic target recognition (ATR) facility in a bistatic radar system is presented. Because of the lack of data, experiments were carried out on simulated data. Still, the results are positive and make a positive case for the introduction of the bistatic configuration. First, it was found that, contrary to the popular expectation that the bistatic ATR performance might be substantially worse than the monostatic ATR performance, the bistatic ATR performed fairly well (though not better than the monostatic ATR). Second, the ATR performance does not deteriorate substantially with increasing bistatic angle. Last, the polarimetric data from bistatic scattering were found to have distinct information, contrary to expert opinions. Along with these results, suggestions were also made about how to stabilise the bistatic-ATR performance with changing bistatic angle. Finally, a new fast and robust ATR algorithm (developed in the present work) has been presented.