Hydrogen Peroxide In Acid Solution Research Articles

Analysis of complex oscillatory dynamics of a pH oscillator

Reaction systems that display pronounced periodic and aperiodic variations in the pH value of the reaction medium are known as pH oscillators. A member of this family of reactions studied here, the Cu(II)-catalyzed oxidation of thiosulfate by hydrogen peroxide in acidic solution, is known to display a rich variety of oscillatory dynamics. We focus on experimental time series showing complex aperiodic dynamics that simultaneously possesses the characteristics of period-doubled large-amplitude oscillations and irregular small-amplitude oscillations reminiscent of mixed-mode dynamics. An analysis based on the reconstruction of the attractor from the measured time series by two different methods and subsequent calculation of the maximal Lyapunov exponent reveals that this interesting dynamical regime is a manifestation of deterministic chaos.

Development of a field method for measuring manganese in welding fume

Workers who perform routine welding tasks are potentially exposed to fume that may contain manganese. Manganese may cause respiratory problems and is implicated in causing the occurrence of Parkinson-like symptoms. In this study, a field colorimetric method for extracting and measuring manganese in welding fume was developed. The method uses ultrasonic extraction with an acidic hydrogen peroxide solution to extract welding fume collected on polyvinyl chloride filters. Commercially available pre-packaged reagents are used to produce a colored solution, created by a reaction of manganese(ii) with 1-(2-pyridylazo)-2-naphthol. Absorbance measurements are then made using a portable spectrophotometer. The method detection limit and limit of quantification (LOQ) were 5.2 microg filter(-1) and 17 microg filter(-1), respectively, with a dynamic range up to 400 microg filter(-1). When the results are above the LOQ for the colorimetric method, the manganese masses are equivalent to those measured by the International Organization for Standardization Method 15202-2, which employs a strong acid digestion and analysis using inductively coupled plasma-optical emission spectrometry.

Optimization of desulphurization of Artvin–Yusufeli lignite with acidic hydrogen peroxide solutions

In this study in which the Taguchi method was used, the optimization of sulphur removal by H 2O 2/H 2SO 4 solutions was carried out over lignite with higher content of sulphur from Artvin/Yusufeli, Turkey. In experiments, the ranges of experimental parameters were between 0.25 and 6.0 mol L −1 for H 2O 2 concentration, 0.25–4 mol L −1 for H 2SO 4 concentration, 10–60 °C for reaction temperature, 0.01–0.08 g mL −1 for solid-to-liquid ratio, 15–120 min for reaction time, 200–300 rpm for stirring speed and 710–120 μm for particle size. The optimum conditions for these parameters have found to be 60 °C of temperature, 0.06 g mL −1 of solid-to-liquid ratio, 60 min of reaction time, 250 rpm of stirring speed and −250 + 180 μm of particle size. A statistical experimental arrangement, L 25(5 6) was prepared to determine optimum sulphur removal and ash removal ratios. The obtained yields were 97.85% in removal of total sulphur, 56.54% in removal of pyritic sulphur, 21.33% in removal of organic sulphur and 61.52% in removal of ash. According to variance analysis, it was seen that all parameters were effective in removal of pyritic and total sulphur, reaction temperature, solid-to-liquid ratio, reaction time, stirring speed, H 2O 2 and H 2SO 4 concentrations in removal of organic sulphur, and other parameters except acid concentration in removal of ash.

Micromachining of GaAs structures with an acidic hydrogen peroxide solution: Experimental and theoretical 3D etching shapes

A study was made on the micromachining of various GaAs substrates in a H2SO4:H2O2:H2O solution with composition 1:8:1. In the first part the anisotropy etching behaviour was studied. Etch rates and morphologies produced by the acidic solution were evaluated. The second part was devoted to the determination of a database (dissolution constants) for the GaAs crystal. Theoretical 3D etching shapes were derived from the simulator TENSOSIM using this database. Comparison of theoretical 3D etching shapes with experimental shapes supports the validity of the proposed database. So this study opens up new applications in the field of GaAs micromechanical devices.

Stability of Pt-Catalyzed Highly Oriented Pyrolytic Graphite Against Hydrogen Peroxide in Acid Solution

Aiming at clarifying the effects of hydrogen peroxide on the degradation of catalyst in polymer electrolyte fuel cells (PEFCs), a model electrode for the catalyst was prepared by electrodeposition of Pt on highly oriented pyrolytic graphite (HOPG) and its durability against hydrogen peroxide investigated. After storage in acidic solution at room temperature, many scars were formed by oxidative etching of HOPG and Pt-particle catalysts aggregated on the surface. In contrast, no surface change was observed without hydrogen peroxide. These results showed that hydrogen peroxide significantly deteriorates the Pt/HOPG electrode, and the active surface area of the Pt particles, which was determined by cyclic voltammetry, was reduced after immersion in the solution. The influence of applied potential was also investigated, and the deterioration of the electrode was accelerated at potentials both more positive and negative than open-circuit potential (ca. ). Moreover, similar degradation phenomenon was observed when the potential was set at , at which a large amount of is formed in oxygen reduction, in -saturated -free acid solution for .

Chemical changes in silver birch (Betula pendula Roth) wood caused by hydrogen peroxide bleaching and monitored by color measurement (CIELab) and UV-Vis, FTIR and UVRR spectroscopy

Abstract Silver birch (Betula pendula Roth) wood was subjected to bleaching with acidic hydrogen peroxide solution. The color change and chemical changes occurring on bleaching were investigated by CIELab color measurements and UV-Vis, FTIR and UVRR spectroscopy. With bleaching, the color of birch wood changed notably towards white, less red and more yellow, revealed by the CIELab color measurements, however, followed by notable yellowing in 343 days. The chemical changes occurring with the bleaching treatment in the xylem of birch, demonstrated by UV-Vis, FTIR and UVRR spectroscopy, indicated degradation of aromatic structures with a simultaneous increase in relative amounts of unconjugated carbonyl structures. The results indicate that the degradation of aromatic structures involved opening of the aromatic ring possibly leading to the formation of muconic acids or other low molecular weight products rich in carbonyl structures. In addition, in birch wood subjected to bleaching treatment with acidic hydrogen peroxide solution, syringyl structures provided favorable sites for the degradation of aromatic structures.

Evaluation of a New CA15-3 Protein Assay Method: Optical Protein-Chip System for Clinical Application

Carbohydrate antigen 15-3 (CA15-3) is frequently measured as a breast cancer marker test. Here we describe a novel type of optical biosensor system, the optical protein chip (OPC), to detect CA15-3 in serum. The complex formed by interaction between an antibody molecule and its corresponding antigen can be detected on a silicon substrate by an optical sensor, as described in previous reports (1)(2). For processing and modification of the silicon substrate surface, silicon wafers were cut into ∼2 × 0.7 cm rectangles and made hydrophilic by immersion in an acidic peroxide solution (300 mL/L H2O2–980 mL/L H2SO4; 1:3 by volume) and light shaking in a shaker for 30 min. The solution not only removed contaminants from the silicon surface but also increased the number of silanol groups on the surface. The hydrophilic surfaces were rinsed in distilled water 3 times and in absolute ethanol 3 times, then incubated in a mixture of 3-aminopropyltriethoxysilane and ethanol (1:15 by volume) and shaken lightly in a shaker for 2 h. The liquid was then removed, and the silicon wafers were rinsed in absolute ethanol 3 times and in phosphate-buffered saline (PBS) buffer 3 times. The wafers were then placed in a mixture of glutaraldehyde and PBS (1:10 by volume), shaken lightly in a shaker for 1 h, and finally, washed in PBS buffer 3 times and left in a beaker with PBS buffer until use. Through the reaction of glutaraldehyde with 3-aminopropyltriethoxysilane, Fc regions of the antibody molecules were covalently immobilized on the chip surfaces. Protein chip preparation and detection included the following steps: (a) CA15-3-specific monoclonal antibody (Biodezign) was concentrated to 0.1 g/L, and then 20 μL of CA15-3 solution …

Electrosynthesis of hydrogen peroxide in acidic solutions by mediated oxygen reduction in a three-phase (aqueous/organic/gaseous) system Part I: Emulsion structure, electrode kinetics and batch electrolysis

The mediated electrosynthesis of H2O2 in acidic solutions (pH 0.9–3.0) was investigated in a three-phase, aqueous/organic/gaseous system using 2-ethyl-9,10-anthraquinone (EtAQ) as mediator (redox catalyst). The main hydrogen peroxide producing route is the in situ mediating cycle: EtAQ electroreduction–homogeneous oxidation of anthrahydroquinone (EtAQH2). The organic phase was composed of tributylphosphate solvent (TBP) with 0.2 M tetrabutylammonium perchlorate (TBAP) supporting electrolyte, 0.06 M tricaprylmethylammonium chloride (A336) surface active agent, and 0.1–0.2 M EtAQ mediator. Part I of this two part work deals with the physico-chemical characteristics of the emulsion electrolyte (e.g., ionic conductivity, emulsion type, H2O2 partition between the aqueous and organic phases), and kinetic aspects (both electrode and homogenous) of the mediation cycle. Furthermore, batch electrosynthesis experiments are presented employing reticulated vitreous carbon cathodes (specific surface area 1800 m2 m−3) operated at superficial current densities of 500–800 A m−2. During 10 h batch electrolysis involving the emulsion mediated system with O2 purge at 0.1 MPa pressure, H2O2 concentrations in the range 0.53–0.61 M were obtained in 0.1 M H2SO4 (pH 0.9) and 2 M Na2SO4(acidified to pH3). The corresponding apparent current efficiencies were from 46 to 68%. Part II of the present work describes investigations using flow-by fixed-bed electrochemical cells with co-current upward three-phase flow.

Electrosynthesis of hydrogen peroxide in acidic solutions by mediated oxygen reduction in a three-phase (aqueous/organic/gaseous) system. Part II: Experiments in flow-by fixed-bed electrochemical cells with three-phase flow

The second part of the work concerned with mediated electrosynthesis of H2O2 in acidic solutions (pH 3) deals with investigations using divided flow-by fixed bed electrochemical cells operated with co-current three-phase flow (aqueous/organic emulsion and O2 gas at 0.1 MPa). Graphite felt (GF) and reticulated vitreous carbon (RVC) were evaluated as cathodes at superficial current densities up to 3000 A m−2. Typically, at current densities above 600 A m−2 graphite felt yielded higher peroxide concentrations per pass and current efficiencies, most likely due to the almost an order of magnitude higher organic liquid to solid mass transfer capacity for 2-ethyl-9,10-anthraquinone (EtAQ) mediator, that is, 0.13 s−1 in the case of GF vs 0.015 s−1 for RVC with 39 ppc (pores per cm). Factorial experiments revealed a positive interaction effect between superficial current density and emulsion load with respect to the current efficiency for H2O2 electrosynthesis. Thus, at the highest investigated superficial current density of 3000 A m−2, the current efficiency was 84% when the emulsion load was at the highest explored level of 11.7 kg m−2 s−1, whilest for the lowest level of emulsion load, 2.8 kg m−2 s−1, the current efficiency for H2O2 was 18%. Furthermore, the presence of 1 mM cationic surfactant, tricaprylmethylammonium chloride (CH3(C8H17)3N+Cl−, A336), had a positive main effect of about 12% on H2O2 current efficiency and there was also a positive synergistic effect between surfactant and emulsion load, estimated at about 7%. The aqueous to organic phase volume ratio, in the range of 0.9/1 and 3/1, had a statistically insignificant effect on the current efficiency for H2O2 generation. A decrease of the aqueous to organic phase volume ratio from 3 to 0.9 increased the cell voltage from about 6.5 to 7.3 V.

Comparison of Glycine and Citric Acid as Complexing Agents in Copper Chemical-Mechanical Polishing Slurries

AbstractTwo complexing agents, glycine and citric acid, in hydrogen peroxide based slurries for planarizing copper have been compared. Copper dissolution and polish rates and in situ electrochemical experimental results at various slurry pH values and hydroxyl radical concentrations at pH=8.4 are presented. It was observed that the pH of the slurry has a strong influence on copper dissolution and polish rates. While high copper removal rates were observed with citric acid-peroxide solutions at low pH values, glycineperoxide system yielded high Cu removal rates at alkaline pH values. Copper dissolution rates in both the systems at pH 4 and 8 were consistent with the electrochemical measurements. The concentration of hydroxyl radicals generated in citric acid-peroxide system was less than that of those generated in glycine peroxide system at pH=8.4 indicating low copper removal rates at alkaline conditions in the former system.

An Electrochemical Quartz Crystal Microbalance Study of the Electrochemical Oscillation in H2O2-Reduction Reaction

Abstract Electrochemical quartz crystal microbalance (EQCM) was used to trace the process of the oscillation A and oscillation B appeared in the reduction reaction of hydrogen peroxide in acidic solutions. Good correlation was observed. Only a few frequency shift even remaining constant was observed parallel with the measured oscillation A while the pronounced frequency shift was correlative to the measured oscillation B. Preliminary idea regarding above observation is presented for discussion.

Activation of hydrogen peroxide by p-nitrophenyl chloroformate. Indication for in situ formation of carbon trioxide and evidence for singlet oxygen generation by the chloride-catalysed decomposition of hydrogen peroxide in acidic solution

The kinetics of the activation of hydrogen peroxide by p-nitrophenyl chloroformate (NPCF) in tetrahydrofuran (THF) have been investigated by measuring the phosphorescence of the released singlet molecular oxygen (1O2) at 1270 nm. The results are consistent with the assumption that the reaction between hydrogen peroxide and NPCF under pseudo first-order conditions with respect to hydrogen peroxide proceeds via a consecutive, pseudo first-order reaction. In the first pseudo first-order reaction O-p-nitrophenyl monoperoxycarbonic acid 1 and hydrochloric acid are formed. The corresponding second-order rate constant at T = 20 °C was found to be k5 = (2.6 ± 0.5) × 10−2 dm3 mol−1 s−1. In the second pseudo first-order reaction 1 undergoes an acid-catalysed decomposition to give, in the end, besides p-nitrophenol, carbon trioxide (CO3), the anhydride of the unstable monoperoxycarbonic acid. The pseudo first-order rate constant of this catalysis was determined to be k10 = (2.9 ± 0.4) × 10−3 s−1 at T = 20 °C. The Arrhenius parameters determined for both reactions are consistent with the assumption that the formation of 1 occurs according to a BAC2-mechanism and that the acid-catalysed decomposition of 1 occurs according to an AAC1-mechanism. The assumption that 1 in the NPCF–H2O2 system undergoes an acid-catalysed decomposition to give CO3 is confirmed by the results of the measurements carried out with the 1H-1,2,4-triazolecarboxylic acid p-nitrophenyl ester (TCNP)–H2O2 system in THF in the presence of sulfuric acid. Moreover, in the NPCF–H2O2–THF system 1O2 is generated by the decomposition of hydrogen peroxide catalysed by chloride. The fact that in acidic solution 1O2 is formed by a chloride-catalysed decomposition of hydrogen peroxide is confirmed by measurements carried out with hydrochloric acid–H2O2 systems in THF and in water, respectively. For the latter system it is found that the oxygen liberated is exclusively formed as 1O2.

Characterization of document paper using elemental compositions determined by inductively coupled plasma mass spectrometry

Comparison of the origin of successive pages of a multiple page document can provide important forensic evidence in cases of document fraud. The use of elemental compositions, determined by inductively coupled plasma mass spectrometry (ICP-MS), to characterize paper is reported. Samples of commonly used office document paper (white, A4, 80 gsm) from seventeen different sources, were analysed for their elemental composition, after microwave digestion in nitric acid–hydrogen peroxide solution. The limits of detection, instrumental precision and potential matrix interferences were established for the 23 most abundant elements found in paper. The variability of distribution for these elements within a ream of paper was determined. Nine elements (Na, Mg, Al, Mn, Sr, Y, Ba, La and Ce) were selected as suitable discriminators because their concentrations were sufficiently high and uniform. All seventeen papers could be distinguished by statistical t-tests (99% confidence) using only two of these elemental concentrations (Mn and Sr). The results are also presented using ternary plots which use three inter-element associations to display the differences in paper composition. Four separate batches of a single product line from the same mill, manufactured at monthly intervals, were also discriminated using elemental concentrations. Three unknown samples, chosen randomly from among the seventeen papers, were correctly identified from their elemental composition; two unknown samples from the four batches were similarly identified. The results show that elemental analysis, using ICP-MS, provides an effective and robust technique for the discrimination of document paper.

Investigation of citric acid-hydrogen peroxide etched GaAs and Al0.3Ga0.7As surfaces by spectroscopic ellipsometry

GaAs (100) surfaces were etched in citric acid-hydrogen peroxide (C6H8O7:H2O2) solutions with volume ratios ranging from 1:1 to 10:1. Ex situ variable angle spectroscopic ellipsometry measurements (1.5–5.5 eV) were made before and after etching for periods of up to 8 min. Analysis of these data indicated that low volume ratios (⩽2:1), with corresponding low etch rates, produced a thin interfacial layer (which might represent microscopic roughness) beneath a porous oxide. For a 1:1 ratio the interfacial layer thickness increased with etch time, while for a 2:1 ratio it stabilized at a small value (≅2 nm). Higher volume ratios (⩾3:1), associated with much higher etch rates, produced qualitatively different overlayers which were more absorbing and 4–6 nm thick. Their optical constants could be modeled as a mixture of a small fraction (typically 5%–10%) of crystalline arsenic in a low-dielectric medium, using an effective medium approximation. Similar effects were seen in etched Al0.3Ga0.7As surfaces. Low etch rates (volume ratio of 5:1 or less) resulted in nearly normal oxide overlayers. A high etch rate (volume ratio 10:1) resulted in an absorbing layer similar to the one seen on rapidly etched GaAs surfaces, 8–12 nm thick.

Titanium-zirconium carbonitride coatings: H.Westphal et al. (Widia GmbH, Essen, Germany.)

The thin-layer chromatographic (TLC) behaviour of 64 ions including Zr(IV) and Hf(IV) has been surveyed on systems composed of silica gel and of nitric acid and nitric acid-hydrogen peroxide media. In the 0.5 mol 1−1 HNO3-3% (w/v) H2O2 solution, only Hf(IV) adsorbed very strongly, whereas Zr(IV) and many other ions showed no or weak adsorption. Stepwise development with diluted nitric acid and subsequently with nitric acid-hydrogen peroxide solution allowed the consecutive separation of three-component mixtures consisting of Zr(IV), Hf(IV) and one of many other accompanying elements, such as Mo(VI), Nb(V), Th(IV), Ti(IV), U(VI) and rare earths(III), to be conducted simply and effectively.

Oxidation of manganese(II) by ozone and reduction of manganese(III) by hydrogen peroxide in acidic solution

Manganese(II) is oxidized by ozone in acid solution, k=(1.5±0.2)×103 M−1 s−1 in HClO4 and k=(1.8±0.2)×103M−1 s−1 in H2SO4. The plausible mechanism is an oxygen atom transfer from O3 to Mn2+ producing the manganyl ion MnO2+, which subsequently reacts rapidly with Mn2+ to form Mn(III). No free OH radicals are involved in the mechanism. The spectrum of Mn(III) was obtained in the wave length range 200–310 nm. The activation energy for the initial reaction is 39.5 kJ/mol. Manganese(III) is reduced by hydrogen peroxide to Mn(II) with k(Mn(III)+H2O2)=2.8×103M−1 s−1 at pH 0–2. The mechanism of the reaction involving formation of the manganese(II)-superoxide complex and reaction of H2O2 with Mn(IV) species formed due to reversible disproportionation of Mn(III), is suggested. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 207–214, 1998.

Consecutive thin-layer chromatographic separation of Zr(IV), Hf(IV) and many other ions on silica gel in nitric acid-hydrogen peroxide media

The thin-layer chromatographic (TLC) behaviour of 64 ions including Zr(IV) and Hf(IV) has been surveyed on systems composed of silica gel and of nitric acid and nitric acid-hydrogen peroxide media. In the 0.5 mol 1 −1 HNO 3-3% (w/v) H 2O 2 solution, only Hf(IV) adsorbed very strongly, whereas Zr(IV) and many other ions showed no or weak adsorption. Stepwise development with diluted nitric acid and subsequently with nitric acid-hydrogen peroxide solution allowed the consecutive separation of three-component mixtures consisting of Zr(IV), Hf(IV) and one of many other accompanying elements, such as Mo(VI), Nb(V), Th(IV), Ti(IV), U(VI) and rare earths(III), to be conducted simply and effectively.

Simple and effective synthesis of pentamethylcyclopentadienyl oxo-peroxo and dioxo tungsten acetylide complexes

The pentamethylcyclopentadienyl tungsten carbonyl acetylide complexes (C 5Me 5)W(CO) 3(CCR), ( 1) R = Ph, CH 2OMe, Pr n and C(Me) = CH 2, reacted with an acidic solution of hydrogen peroxide at room temperature, giving the oxo-peroxo acetylide complexes (C 5Me 5)W(O)(O 2)(CCR) ( 2) in good yields. Upon treatment with triphenylphosphine the complexes ( 2) lost one oxygen atom to afford the corresponding dioxo complexes (C 5Me 5)W(O) 2(CCR) ( 3). These oxo-peroxo and dioxo complexes were characterized by spectroscopic methods and, for (C 5Me 5)W(O) 2(CCPh) ( 3a), was further identified by single crystal X-ray diffraction study.

Synthesis of Peroxo-Modified Anatase Sol from Peroxo Titanic Acid Solution

A peroxo titanic acid (PTA) solution has been prepared by mixing titanic acid wet gel and hydrogen peroxide solution. The PTA solution was a neutral, transparent, stable liquid. The PTA crystallized to form an anatase phase after calcination at a temperature above 250°C. When the PTA solution was autoclaved at a temperature above 100°C for 6h, it changed to a sol containing anatase crystals less than 20nm in diameter. Aggregation occurred after autoclaving at a temperature above 120°C. When the PTA solution was heated to 100°C, it was translucent and stable in spite of containing ultrafine anatase crystals (9nm in diameter). It was deduced that the surfaces of anatase crystals are modified by the peroxo groups.

Selective wet etching of a [formula omitted] heterostructure with citric acid-hydrogen peroxide solutions for pseudomorphic GaAs/Al xGa 1−xAs/In yGa 1−yAs heterojunction field effect transister fabrication

The selective wet etching characteristics of GaAs Al x Ga 1−x As 1−x systems in citric acid-hydrogen peroxide solution have been studied for x = 0.15, x = 0.2 and x = 0.3 respectively. A 4:1 ratio of citric acid (50% by weight)-H 2O 2 solution was found to be a better selective etchant than the more commonly used NH 4OHH 2O 2 solutions. The selectivity obtained was more than 110 for x = 0.3. The simple and reliable selective wet etchant was applied to the gate recess etching in the fabrication of pseudomorphic GaAs/Al xGa 1−xAs/In yGa 1−yAs heterojunction field effect transistors.