Black Oxidation Research Articles

Role of surface chemistry in modified ACF (activated carbon fiber)-catalyzed peroxymonosulfate oxidation

A commercial activated carbon fiber (ACF-0) was modified by three different methods: nitration treatment (ACF-N), heat treatment (ACF-H) and heat treatment after nitration (ACF-NH), and the effects of textural and chemical properties on the ability of the metal-free ACF-catalyzed peroxymonosulfate (PMS) oxidation of Reactive Black 5 (RB5), an azo dye being difficultly adsorbed onto ACF, in aqueous solution were investigated in this work. Surface density of functional groups, surface area changes, surface morphology and the chemical state inside ACF samples were characterized by Boehm titration, N2 adsorption, scanning electron microscopy in couple with energy dispersive spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS), respectively. XPS spectra deconvolution was applied to figure out the importance of surface nitrogen-containing function groups. We found that π-π, pyridine and amine have promoting effect on the catalytic oxidation while the −NO2 has inhibitory effect on the ACF/PMS systems for RB5 destroy. Sustainability and renewability of the typical ACF-NH for catalytic oxidation of RB5 were also discussed in detail. Information about our conclusions are useful to control and improve the performance of ACF-catalyzed PMS oxidation for organic pollutants in wastewater treatment.

Comparison of the quantitative determination of soil organic carbon in coastal wetlands containing reduced forms of Fe and S

The performance of the Walkley–Black wet oxidation chemical method for soil organic carbon (SOC) determination in coastal wetland soils (mangroves, coastal lagoons, and hypersaline tidal flats) was evaluated in the state of Ceara along the semiarid coast of Brazil, assessing pyrite oxidation and its effects on soil C stock (SCS) quantification. SOC determined by the chemical oxidation method (CWB) was compared to that assessed by means of a standard elemental analyzer (CEA) for surficial samples (<30 cm depth) from the three wetland settings. The pyrite fraction was quantified in various steps of the chemical oxidation method, evaluating the effects of pyrite oxidation. Regardless of the method used, and consistent with site-specific physicochemical conditions, higher pyrite and SOC contents were recorded in the mangroves, whereas lower values were found in the other settings. CWB values were higher than CEA values. Significant differences in SCS calculations based on CWB and CEA were recorded for the coastal lagoons and hypersaline tidal flats. Nevertheless, the CWB and CEA values were strongly correlated, indicating that the wet oxidation chemical method can be used in such settings. In contrast, the absence of correlation for the mangroves provides evidence of the inadequacy of this method for these soils. Air drying and oxidation decrease the pyrite content, with larger effects rooted in oxidation. Thus, the wet oxidation chemical method is not recommended for mangrove soils, but seems appropriate for SOC/SCS quantification in hypersaline tidal flat and coastal lagoon soils characterized by lower pyrite contents.

Preparation and Characterization of Black Micro-Arc Oxidation Films

Preparation and Characterization of Black Micro-Arc Oxidation Films

Photocatalytic oxidation of Reactive Black 5 with UV-A LEDs

The effectiveness of UV-A Light emitting diodes (UV-A LEDs) for decolourization of Reactive Black 5 (RB5) solutions in a continuous photoreactor and the effect of different operational parameters on the photocatalytic decolourization of RB5 were investigated in the present work. The operational parameters included catalyst load, initial dye concentration, irradiance and solution flowrate. Photocatalytic experiments were conducted in a self-designed photoreactor with a matrix of 96 UV-A LEDs (375nm) and Evonik P-25 TiO2 was used as a photocatalyst. The optimum experimental conditions that allowed the highest decolourization of RB5 (89%) were an irradiance of 40W/m2, 1.0g/L of TiO2, 50mg/L of RB5 and a flowrate of 0.8mL/min.A continuous stirred tank reactor (CSTR) design equation, subsequently simplified to a pseudo-first order rate equation, was used to analyse the kinetics of the experimental results. From the kinetics it is possible to observe that high TiO2 concentrations (1.0g/L) and light irradiances (40W/m2) positively affect the reaction rate (r, 2.483×10−7mol/Lmin) and the reaction rate constants (k, 7.351×10−3min−1).The figure-of-merit electrical energy per order (EEO) was calculated for the photoreactor, and values of 220kWh/m3/order were reached for an electric power consumption of 0.0129kW and a solution flowrate of 4.8×10−6m3/h. Results demonstrated that a UV-A LED/TiO2 process can effectively decolourize RB5 dye solutions within the selected optimum conditions.

Black carbon surface oxidation and organic composition of beech-wood soot aerosols

Abstract. Soot particles are the most strongly light-absorbing particles commonly found in the atmosphere. They are major contributors to the radiative budget of the Earth and to the toxicity of atmospheric pollution. Atmospheric aging of soot may change its health- and climate-relevant properties by oxidizing the primary black carbon (BC) or organic particulate matter (OM) which, together with ash, comprise soot. This atmospheric aging, which entails the condensation of secondary particulate matter as well as the oxidation of the primary OM and BC emissions, is currently poorly understood. In this study, atmospheric aging of wood-stove soot aerosols was simulated in a continuous-flow reactor. The composition of fresh and aged soot particles was measured in real time by a dual-vaporizer aerosol-particle mass spectrometer (SP-AMS). The dual-vaporizer SP-AMS provided information on the OM and BC components of the soot as well as on refractory components internally mixed with BC. By switching the SP-AMS laser vaporizer off and using only the AMS thermal vaporizer (at 600 °C), information on the OM component only was obtained. In both modes, OM appeared to be generated largely by cellulose and/or hemicellulose pyrolysis and was only present in large amounts when new wood was added to the stove. In SP-AMS mode, BC signals otherwise dominated the mass spectrum. These signals consisted of ions related to refractory BC (rBC, C1-5+), oxygenated carbonaceous ions (CO1-2+), potassium (K+), and water (H2O+ and related fragments). The C4+ : C3+ ratio, but not the C1+ : C3+ ratio, was consistent with the BC-structure trends of Corbin et al. (2015c). The CO1-2+ signals likely originated from BC surface groups: upon aging, both CO+ and CO2+ increased relative to C1-3+ while CO2+ simultaneously increased relative to CO+. Factor analysis (positive matrix factorization) of SP-AMS and AMS data, using a modified error model to address peak-integration uncertainties, indicated that the surface composition of the BC was approximately constant across all stages of combustion for both fresh and aged samples. These results represent the first time-resolved measurements of in situ BC surface aging and suggest that the surface of beech-wood BC may be modelled as a single chemical species.

Modelling of Carbon Black oxidation in the presence of CeO2 catalyst using a 3D representation of the solid–solid mixture

A model based on a 3D representation of mixtures involving Carbon Black (CB) and commercial ceria (CeO2) particles placed in a fixed bed reactor is proposed. Catalyst particles may aggregate in different ways in the whole bed and different CB–CeO2 mass ratios are considered which range from 95–5 to 10–90. Two types of oxidation are assigned by the model: a catalytic oxidation under the influence of CeO2 and a non-catalytic one in the other case. The activation energies of these oxidation processes have been determined through experiments, while their frequency factors are derived for the two reactions using a numerical simulation. The model simulates the CB oxidation in a good way whatever the CB–CeO2 mass ratio, except for the 50–50 case. The catalytic oxidation is here underestimated, as the contact between CB and CeO2 is progressively lost.

Quantitative Assessment of Parametric Uncertainty in Northern Hemisphere PAH Concentrations.

We quantitatively examine the relative importance of uncertainty in emissions and physicochemical properties (including reaction rate constants) to Northern Hemisphere (NH) and Arctic polycyclic aromatic hydrocarbon (PAH) concentrations, using a computationally efficient numerical uncertainty technique applied to the global-scale chemical transport model GEOS-Chem. Using polynomial chaos (PC) methods, we propagate uncertainties in physicochemical properties and emissions for the PAHs benzo[a]pyrene, pyrene and phenanthrene to simulated spatially resolved concentration uncertainties. We find that the leading contributors to parametric uncertainty in simulated concentrations are the black carbon-air partition coefficient and oxidation rate constant for benzo[a]pyrene, and the oxidation rate constants for phenanthrene and pyrene. NH geometric average concentrations are more sensitive to uncertainty in the atmospheric lifetime than to emissions rate. We use the PC expansions and measurement data to constrain parameter uncertainty distributions to observations. This narrows a priori parameter uncertainty distributions for phenanthrene and pyrene, and leads to higher values for OH oxidation rate constants and lower values for European PHE emission rates.

Influence of Environmental Conditions on Carbon Black Oxidation by Reactive Oxygen Intermediates

The paper examined the influence of hydrogen peroxide and ozone and singlet oxygen co-agents on the functional groups of the carbon black surface. The influence of the ambient temperature and the concentration of the reactants on protogenic functional groups (carboxylic and phenolic) generating has been studied. To assess the functional composition methods of titration with alkali of different strengh, differential potentiometer, pyrolysis gas chromatography have been used. It was found that the carbon oxidation depends on the sample structure. It is shown that carbon oxidation with hydrogen peroxide depends on the co-agent nature. With singlet oxygen used as a co-agent, carboxyl groups with the lowest pKa of about 2are generated on the carbon surface. When using ozone pKa of the group is higher than 2.

Physicochemical characterization and catalytic performance of 10% Ag/CeO2 catalysts prepared by impregnation and deposition–precipitation

Two silver–cerium oxide samples (Ag 10wt.%) were prepared by two different methods: impregnation and deposition–precipitation. The XRD, EPR, XPS, and TPR techniques were used for physicochemical characterization. Catalysts were tested in C3H6, CO, and carbon black oxidation reactions. The impregnated catalyst showed better performance compared to the one prepared by deposition–precipitation in the different reactions. The EPR technique allowed the identification of three different Ag2+ sites in the impregnated solid along with the distinction of the Ag2+ isotopes (107Ag2+ and 109Ag2+) ions. The impregnated catalyst reduced at lower temperatures compared to the one prepared by deposition–precipitation. The catalytic activity of the impregnated solid was attributed to the presence of Ag2+ species that enhance the redox potential of the solid by creating three different redox couples: Ag2+/Ag+, Ag2+/Ag0, and Ag+/Ag0.

Study of carbon black oxidation behavior under different heating rates

The thermodynamic methods of the Arrhenius and Achar-Brindley-Sharp-Wendworth are employed to investigate the influence of the heating rate on oxidation characteristics of three carbon samples. High resolution transmission electron microscopy, Raman spectroscopy, and specific surface area measurements using Brunauer–Emmett–Teller theory are applied to evaluate the influence of the graphitization degree, the microcrystalline length, and the microstructure on the oxidation of carbon black. The results show that with the increase in heating rate, the reaction rate of carbon black increases and the oxidation activation energy gradually decreases; the fitted values of the activation energy range from 136.4 to 221.3 kJ mol−1 with the heating rate is <100 K min−1. Besides, the evaporation and oxidation of simulating soluble organic fractions absorbed on carbon samples can change its internal microstructure, which could influence carbon oxidation. All experimental results indicate that carbon black would sequentially take those steps during oxidation: volatile substance evaporation or oxidation, amorphous carbon oxidation, graphitization, and combustion finally.

Preparation of Black Coating on AM50 Alloys by Microarc Oxidation (MAO)

The black microarc oxidation (MAO) coating containing Cu2+ was prepared on AM50 magnesium alloys. When the additives (CuSO4 and C4H4KNaO6 · 4H2O) were added into the NaAlO2 solution, the color of the prepared coatings appearance changed from white to black. The effects of CuSO4 concentration and treatment time on the color of the coatings were investigated. The optimum formula of black coatings prepared by MAO has been acquired by a single-factor experiment and orthogonal experiment of L9(34) with four factors and three levels. The estimated optimum values of the process parameters are corresponding to NaAlO2 10 g/L, C4H4KNaO6 · 4H2O 1 g/L, CuSO4 1 g/L, and pH 11. The surface morphologies, structure, composition, and corrosion resistance of the MAO coatings were analyzed by scanning electron microscopy, X-ray diffraction (XRD), and electrochemical tests. The results of the above series of tests have shown that the properties and characteristics of the black coatings are improved. The black coating is irregular porous structure, which aperture size is about 0.1 ∼ 0.2 µm. The black coating mainly consists of MgO, MgAl2O4, and Cu3MgO4.

Activity of Highly Dispersed Co/SBA-15 Catalysts (Low Content) in Carbon Black Oxidation

Cobalt supported on mesoporous silica SBA-15 (0.75, 1.5 and 3 wt% Co) were used as catalysts for the oxidation of carbon black. Catalysts were characterized by N 2 sorption, XRD, TEM and TPR. The catalytic activity in CB oxidation was measured. It has been shown that only small cobalt domains (less than 5 nm) are present on all samples. A homogeneous dispersion was obtained for all catalysts. With increasing cobalt loading, crystalline species start to appear. Using an intermediate contact between the CB and the catalyst, the best activity is that of 0.75Co/SBA-15 catalyst where the oxidation reaches the maximum (Tmax) 68 K before the non-catalyzed reaction. On the same catalyst used in tight contact mode with CB, even if Tmax didn’t decrease for more than additional 12 K but the Ti decreases by 38K and thus starts 83 K before.

Fenton-like oxidation of Reactive Black 5 using rice husk ash based catalyst

Fenton-like oxidation of Reactive Black 5 dye was carried out using iron(III) impregnated on rice husk ash as heterogeneous catalyst. The catalyst was prepared by wet impregnation method and characterized. The effectiveness of this catalyst in degradation and decolorization of the dye, as well as the influence of reaction parameters on the catalytic activity was discussed. The effects of pH, the initial hydrogen peroxide concentration, the catalyst loading, and the temperature on the oxidative degradation and decolorization of Reactive Black 5 have been assessed. The best degradation efficiency (59.71%) and decolorization efficiency (89.18%) was obtained at temperature=30°C, pH=3, [H2O2]0=4mM, catalyst loading=0.5g/L for initial dye concentration of 100mg/L.

Preparation of cobalt molybdate nanoparticles; Taguchi optimization and photocatalytic oxidation of Reactive Black 8 dye

In this study, cobalt molybdate (CoMoO4) nanoparticles were synthesized by precipitation and microemulsion methods. The effective parameters for these two methods were determined and optimized using Taguchi design method. The obtained nanoparticles were characterized by XRD, SEM, TEM, DLLS and BET analysis. By comparing the results of the two methods, it was found that the microemulsion procedure produces finer particles (11.7nm) with higher specific surface area than that obtained by precipitation method. Moreover, the CoMoO4 nanoparticles were successfully applied to eliminate Reactive Black (RB) 8 dye from aqueous solution with decolorization efficiency of 91.47%.

Heterogenous Fenton-Like Oxidation of Reactive Black 5 in Water Using Pyrite Cinder

As the Fenton-like oxidation reaction based on iron-bearing minerals could solve some problems of the traditional Fenton oxidation reaction, it became a talking point in academic circles worldwide recently. For the Fenton-like reaction, catalyst selection is an important research parameter. The new Fenton-like reaction uses iron-bearing cinder as catalyst by employing Reactive Black 5 (RB5), the object of investigation, as the target pollutant. By examining the dosage of catalyst, hydrogen peroxide, initial pH, reaction time, concentration of pollutants, optimized reaction conditions can be obtained. Results show that pyrite cinder gives rise to high catalytic activity in the Fenton-like reaction. When 5ml/L of hydrogen peroxide and 10g/L of cinder were added to 75mg/L of dye, the removal rate of RB5 was found to be 96% in 4 hours. Compared to the traditional Fenton reaction, it has a wider pH range and higher catalytic oxidation activity, especially under alkaline condition.

Catalytic activity of copper oxide added to a sample as a copper-polymer carboxylated complex in the reaction of carbon black oxidation

The catalytic activity of copper oxide in the carbon black reaction with air oxygen has been studied with the catalyst addition to a sample by different methods. It has been shown that copper oxide added as copper acetate from the ether solution accelerates the carbon black oxidation at 700 K approximately by a factor of 110, copper acetate added from a water solution accelerates the carbon black oxidation by a factor of 300, and if the catalyst is added as a copper-polymer carboxylated complex, the carbon black oxidation is accelerated by a factor of 460. It has been assumed that the difference in catalytic activity of copper oxide added by various methods is caused by the nonuniformity of the copper distribution over the carbon black surface.

Photo‐Fenton Oxidation of Azo Dye Reactive Black B Using an Immobilized Iron Oxide as Heterogeneous Catalyst

The heterogeneous oxidation of azo dye Reactive Black B (RBB) by the photo-Fenton system catalyzed with an immobilized iron oxide, B1 (supported with SiO2 grain), was investigated. Reactive Black B oxidation was carried out in an expended-bed reactor in which the effect of B1 dosage on the decolorization and degradation of RBB was examined. Through pseudo-first-order kinetic studies, decolorization was found to be faster than degradation with a fixed rate constant ratio. By determining the iron dissolution from B1, RBB oxidation was supposed to mainly occur on the B1 surface, which catalyzed the generation of hydroxyl radicals in the photo-Fenton reaction. Accordingly, the efficiency of photo-Fenton could reach 100% and 91.2% of decolorization and degradation, respectively, in 300 minutes.

Comparison of methods for the characterization and quantification of carbon forms in estuarine and marine sediments from coal mining regions

Organic matter (OM) in sediments plays a vital role in the global carbon cycle, yet its quantification remains a major analytical challenge. The applicability of various techniques for characterizing the OM in six estuarine sediment samples from the coal-mining region of Northumbria and Tyne and Wear (UK) and three marine sediment samples from the lignite mining region of Aliveri (Greece) was tested. The techniques included wet chemical oxidation according to Walkley–Black and thermal oxidation (16h, 375°C), automatic carbon analysis after thermal (24h, 500°C) and acid treatment, organic petrography, Rock–Eval pyrolysis and thermogravimetric analysis combined with data from X-ray diffraction. The total organic carbon (TOC) content determined after HCl or thermal treatment correlated well but HCl treatment tended to record lower TOC content. Known additions showed that coal OM is partially resistant to wet chemical oxidation and does not contribute to the thermally resistant OC fraction.

Using iron-loaded sepiolite obtained by adsorption as a catalyst in the electro-Fenton oxidation of Reactive Black 5

This study explores the possibility of using iron-loaded sepiolite, obtained by recovering iron from polluted water, as a catalyst in the electro-Fenton oxidation of organic pollutants in textile effluents. The removal of iron ions from aqueous solution by adsorption on sepiolite was studied in batch tests at iron concentrations between 100 and 1,000ppm. Electro-Fenton experiments were carried out in an electrochemical cell with a working volume of 0.15L, an air flow of 1L/min, and 3g of iron-loaded sepiolite. An electric field was applied using a boron-doped diamond anode and a graphite sheet cathode connected to a direct current power supply with a constant potential drop. Reactive Black 5 (100mg/L) was selected as the model dye. The adsorption isotherms proved the ability of the used adsorbent. The removal of the iron ion by adsorption on sepiolite was in the range of 80-100% for the studied concentration range. The Langmuir and Freundlich isotherms were found to be applicable in terms of the relatively high regression values. Iron-loaded sepiolite could be used as an effective heterogeneous catalyst for the degradation of organic dyes in the electro-Fenton process. Successive batch processes were performed at optimal working conditions (5V and pH2). The results indicate the suitability of the proposed combined process, adsorption to iron remediation followed by the application of the obtained iron-loaded sepiolite to the electro-Fenton technique, to oxidize polluted effluents.

Carbon black and propylene oxidation over Ru/CoxMgyAl2Oz catalysts

Abstract The effects of CoxMgyAl2Oz mixed oxides composition and ruthenium addition on the oxidation of propylene and carbon black (CB) were investigated. Different reactive cobalt and ruthenium oxide species were formed following calcination at 600 °C. The addition of ruthenium was beneficial for the CB oxidation under “loose contact” conditions and for propylene oxidation when the cobalt content was intermediate to low. The calculated activation energy for CB oxidation was decreased from 151 kJ mol−1 for the uncatalyzed reaction to 111 kJ mol−1 over the best catalyst.