Air Oxidation Process Research Articles

Electric Conduction Mechanisms Study within Zr Doped Mn3O4 Hausmannite Thin Films through an Oxidation Process in Air

Electric Conduction Mechanisms Study within Zr Doped Mn3O4 Hausmannite Thin Films through an Oxidation Process in Air

Dilithium and Magnesium Alkanediides and 1‐Oxaalkanediides

Dilithium and magnesium alkanediides of the types Li(CH2)nLi and [Mg(CH2)n]x represent substance classes with a long tradition, however, the interest in these compounds ceased in recent years. Numerous reasons account for the vanishing attention such as challenging synthetic procedures, poor to moderate yields, complex structures in solution and the solid state, and complex equilibria in solution. Degradation processes (ether degradation, β‐hydride elimination, indirect reduction reactions) increase the intricacy of these compounds because these degradation products take part in the solution equilibria. Thus, chloride and hydride ions are able to act as templates for lithium cages yielding e.g. [(Et2O)4Li]+ [Li12(C4H8)6(@‐X)]– (X = H, Cl) with an X‐centered Li12 icosahedron. Despite these challenges, the dilithium and magnesium alkanediides are a fascinating substance class with a rich chemistry by its own (such as Schlenk‐type equilibria) and as metalating and reducing reagents. The enormous sensitivity toward moisture (hydrolysis reactions) and air (oxidation processes) and reactivity toward ethereal media (ether degradation reactions) also interferes with the dianionic alkanes because alkoxide and oxide ions are strong Lewis bases and as such, are easily integrated in the structures as bridging anions or centers of metal cages. Thus, aerial oxidation leads to insertion of an oxygen atom into the metal–carbon bond yielding 1‐oxaalkanediides. Alternatively, magnesium 1‐oxaalkanediides can be prepared by a two‐step protocol from chloroalkanol, starting with deprotonation of the alcohol functionality with a Grignard reagent and a subsequent reduction of the C–Cl unit with magnesium turnings. This protocol leads to compounds of the type [{MgO(CH2)n}x(MgCl2)y] with additional ether bases saturating the coordination spheres of the magnesium atoms. All these reactions (increasing degradation processes and reactions with inadvertently introduced traces of oxygen and moisture) limit the durability of such solutions, subsumed as aging of these dilithium and magnesium dialkanediide stock solutions, which lead to a changing (decreasing) reactivity of such reagents.

Synthesis and Demonstration of Subnanometric Iridium Oxide as Highly Efficient and Robust Water Oxidation Catalyst

Development of a highly efficient and robust water oxidation catalyst (WOC) with reduced usage of noble metals is extremely crucial for water splitting and CO2 reduction by photocatalysis or electrolysis. Herein, we synthesized subnanometric iridium dioxide clusters supported on multiwalled carbon nanotubes (MWCNTs) by a chemical vapor deposition method (nominated as IrO2/CNT). Benefiting from a mild oxidation process in air at 303 K, the deposited iridium clusters can be controlled to have a narrow size distribution from several atoms to 2 nm, having an average size of ca. 1.1 nm. The subnanometric iridium-containing sample is demonstrated to be highly efficient and robust for water oxidation. The optimal turnover frequency (TOF) of chemical water oxidation on the as-obtained sample can reach 11.2 s–1, and the overpotential of electrochemical water oxidation is 249, and 293 mV at 10 mA cm–2 in 1.0 M KOH (pH: 13.6), and 0.5 M H2SO4 (pH: 0), respectively. On the basis of the structural characterizations an...

Wastewater treatment by catalytic wet air oxidation process over Al-Fe pillared clays synthesized using microwave irradiation

Microwave irradiation has been used to prepare Al, Fe-pillared clays from a natural Tunisian smectite from the El Hicha deposit (province of Gabes). Chemical analysis, XRD spectra and surface properties evidenced the success of pillaring process. The obtained solids present higher surface area and pore volume than conventionally prepared Al-Fe pillared clays. The main advantages of the microwave methodology are the considerable reduction of the synthesis time and the consumption of water. The microwave-derived Al-Fe pillared clays have been tested for catalytic wet air oxidation (CWAO) of phenol in a stirred tank at 160°C and 20 bar of pure oxygen pressure. These materials are efficient for CWAO of phenol and are highly stable despite the severe operating conditions (acidic media, high pressure, high temperature). The catalyst deactivation was also significantly hindered when compared to conventionally prepared clays. Al-Fe pillared clays prepared by microwave methodology are promising as catalysts for CWAO industrial water treatment.

Treatment of industrial organic raffinate containing pyridine and its derivatives by coupling of catalytic wet air oxidation and biological processes

The treatment of non-biodegradable industrial organic raffinate containing refractory and toxic organic compounds pyridine, β-picoline and 3-cyanopyridine has been studied by coupling of catalytic wet air oxidation (CWAO) over alumina based platinum catalyst and biological processes. The alumina based platinum catalyst was characterized and the stability of the catalyst was studied. The CWAO experiments were performed in a glass reactor at atmospheric pressure and the effluent treatment efficiency was evaluated in terms of chemical oxygen demand (COD) removal. The effect of various parameters such as air flow rate, reaction temperature, platinum loading and catalyst dosage on the COD removal was studied. The optimum values of air flow rate, platinum loading and catalyst dosage were found to be 1 L/min, 1 wt. % and 3 g/L respectively and a COD removal of 45% was obtained at the optimum conditions at reaction temperature of 70 °C. The CWAO experimental results were found to be in agreement with the lumped kinetic model. The toxicity test using E. coli bacteria and the biodegradability study were performed. The toxicity of the effluent decreased considerably while the BOD/COD ratio was found to increase significantly after the CWAO. The aerobic biological treatment confirmed the biodegradability enhancement and a total COD removal of 98.4% was obtained after 10 days of aerobic treatment of the CWAO effluent.

Experimental coupling and modelling of wet air oxidation and packed-bed biofilm reactor as an enhanced phenol removal technology.

Experimental coupling of wet air oxidation process and aerobic packed-bed biofilm reactor is presented. It has been tested on phenol as a model refractory compound. At 30MPa and 250°C, wet air oxidation batch experiments led to a phenol degradation of 97% and a total organic carbon removal of 84%. This total organic carbon was mainly due to acetic acid. To study the interest of coupling processes, wet air oxidation effluent was treated in a biological treatment process. This step was made up of two packed-bed biofilm reactors in series: the first one acclimated to phenol and the second one to acetic acid. After biological treatment, phenol and total organic carbon removal was 99 and 97% respectively. Thanks to parameters from literature, previous studies (kinetic and thermodynamic) and experimental data from this work (hydrodynamic parameters and biomass characteristics), both treatment steps were modelled. This modelling allows the simulation of the coupling process. Experimental results were finally well reproduced by the continuous coupled process model: relative error on phenol removal efficiency was 1 and 5.5% for wet air oxidation process and packed-bed biofilm reactor respectively.

A solar ultraviolet sensor based on fluorescent polyoxometalate and viologen

A novel solar ultraviolet sensitive composite film, which can be coloured and bleached by photoreduction and air oxidation processes, has been readily prepared using fluorescent polyoxometalate and viologen.

Enhanced Oxidation of Reactive Black 5 Using a Ferrous Oxidation–Based Treatment Process in the Presence of Hydrous Ferric Oxide

AbstractThe major limitations of the Fenton process are the working pH range (2–5) and the high cost of H2O2. These limitations were unraveled using the Fe2+-air oxidation process, in which ferrous ions were used with continuous aeration without H2O2 at a higher pH (pH = 10). This paper studies the effect of the initial hydrous ferric oxide (HFO) concentration on the Fe2+-air process. The enhancement in degradation of the dye [Reactive Black 5 (RB5)] was observed using the Fe2+-air process in the presence of initial HFO, as compared to the Fe2+-air process in the absence of initial HFO. The enhancement is possibly attributable to the adsorption of ferrous ions, dye, and oxygen onto the HFO surface and leading to effective utilization of reactive oxidizing species. The oxidizing entities appear to be generated during oxidation of adsorbed ferrous ions under oxic conditions—probably on the surface of HFO. Furthermore, the Fe2+-air process in the presence of HFO reduces the concentration of ferrous ions requ...

Paper industry will drive global spending on optical brighteners beyond $1 bn by 2020

Recovery of chemicals in papermaking and converting sections are presented in this chapter. Use of wet air oxidation process, OptiThick GapWasher technology (Metso), Trenntechnik (a filler recovery system connected to the effluent treatment plant), forced evaporation, FilRec (Ahlstrom), ultrafiltration techniques, etc. for recovery of coating color, pigments, and fillers are discussed.

Study on Catalytic Wet Air Oxidation Process for Phenol Degradation in Synthetic Wastewater Using Trickle Bed Reactor

The present work aims to study the feasibility of utilizing a trickle bed reactor, packed with activated carbon catalyst, for phenol degradation in synthetic wastewater. Effect of operating variables (e.g., pH, pressure, temperature, gas flow rate, liquid flow rate, and flow mode) on the performance of the trickle bed reactor was investigated and optimized. Results showed that phenol degradation would be enhanced by increasing temperature, pressure, and gas flow rate, while initial concentration of phenol and liquid flow rate give a different trend. It was found that down-flow mode exhibits better performance than up-flow mode. High degradation rate of phenol of about 97 % was obtained at optimum conditions (liquid space time = 0.143 h, temperature = 160 °C, oxygen partial pressure = 0.9 MPa, and phenol concentration = 5 mg/l). Reaction kinetics including effects of catalyst deactivation on the oxidation process was investigated. Results showed that the oxidation process behaves as pseudo-first-order reaction with respect to phenol concentration, and 0.6 with respect to oxygen solubility. Activation energy is 77.7 kJ/mol. and reaction rate constant is equal to \({1.826 \times 10^{9}{l}/{kg}_{\rm cat}}\) h. However, when catalyst deactivation was taken into account, the reaction rate constant and activation energy were \({2.9 \times 10^{11} {l}/{kg}_{\rm cat}}\) h and 114.43 kJ/mol, respectively, and the oxygen order was equal to 1.4. The calculated kinetic parameters were compared with the data reported in the literature.

Energy Optimisation of Wet Air Oxidation Process Based on the Preliminary Study on Liquid-Vapour Equilibrium

Wet air oxidation process is used to treat wastewater with high chemical oxygen demand. Temperatures up to 350°C and pressures up to 30 MPa, are operated to develop a non-catalytic process. In the literature, there is some data about the phase equilibrium of water-air system but on larger domains and not accurate enough in our range. To study the process, it is necessary to complete the data with adapted pressures, temperatures and compositions. An experimental set-up has been developed to realise equilibrium measurements as well as trials on waste degradation. It consists of a stirred reactor of 150 mL equipped with two sapphire windows (diameter 4.1 cm) allowing a total visualization of the reactive chamber. The results of experiments give the volume occupied by the liquid and the gas phases, for a combination of temperature, pressure and global composition. Measurements are realised to establish dew curves for water-air, water-nitrogen and water-waste-nitrogen systems. Nitrogen has the same behaviour as oxygen and can replace it in mixtures for the phases equilibrium studies with the waste to avoid any reaction. The presence of the waste, in the concentrations studied, has no significant influence on the equilibrium points. Those data serve to model the liquid-vapour equilibrium in the appropriate domain first with an ideal model and then with equation of state Soave-Redlich-Kwong and appropriate mixing rules. Those equilibrium models are then included in commercial engineering software to simulate WAO processes. With the objective to develop a process energetically optimised, the second part of this work is dedicated to perform energy balances for each component and for the whole process

Tracking and analyzing the structures and morphologies of mesocarbon microbeads (MCMBs) in air oxidation process

Mesocarbon microbeads (MCMBs) were fabricated from coal tar pitches via the general air oxidization method. To track and analyze the structures of MCMBs in detail, air oxidization was carried out slowly. Polycondensation among the aromatic rings of polycyclic aromatic hydrocarbons in coal tar pitches is carried out mainly through the bonding type of Ar-R-O-R-Ar, which was verified by FT-IR measurements. Meanwhile, the lamellar structure is observed at the initial forming stage of the MCMBs, which was verified by measurements of X-ray diffraction. These results show that controlling the reaction condition is likely to fabricate MCMBs suitable for storage of lithium ions.

Carbon and nitrogen removal from glucose-glycine melanoidins solution as a model of distillery wastewater by catalytic wet air oxidation

Sugarcane molasses distillery wastewater contains melanoidins, which are dark brown recalcitrant nitrogenous polymer compounds. Studies were carried out in batch mode to evaluate Pt and Ru supported catalysts in the Catalytic Wet Air Oxidation (CWAO) process of a synthetic melanoidins solution, prepared by stoichiometric reaction of glucose with glycine. The addition of a catalyst slightly improved TOC removal compared with the non-catalytic reaction, and especially promoted the conversion of ammonium produced from organically-bound nitrogen in melanoidins to molecular nitrogen and nitrate. The selectivity to N2 attained 89% in the presence of the Pt catalysts in the reaction conditions used (TOC=2200mgL−1, TN=280mgL−1, 0.5g catalyst loaded with 3% metal, 210°C, 70bar total air pressure). To avoid leaching of the active metal by organically-bound nitrogen, the reaction was very efficiently performed in a two-step reaction consisting in WAO to convert nitrogen into ammonium, before the introduction of a catalyst.

Quantitative structure–property relationship (QSPR) study for the degradation of dye wastewater by Mo–Zn–Al–O catalyst

Quantitative structure–property relationships (QSPR) between the structure of dyes and the discoloration rate of dyes were established to predict the discoloration rate of dyes in catalytic wet air oxidation (CWAO) process. The DFT-based quantum chemical descriptors were obtained at the B3LYP/6-31G (d,p) level and partial lease squares (PLS) regression was employed for QSPR model development. The discoloration rate of dyes was recorded in the CWAO process by Mo–Zn–Al–O catalyst under room conditions. The optimal QSPR model with a cross-validation Q2(cum) value of 0.845 and R value of 0.9893 indicates that the QSPR model has sufficient predictive ability and robustness. Two components were selected in the model, which account for 0.733 of the variance of the predictor variables and 0.979 of the variance of the dependent variable. The absolute values of W*[1] for that absolute hardness (η) and the most negative atomic net charges of the molecule (q‑) were 0.806657 and 0.561769 demonstrates that η and q− are the main causes for the first component. The second PLS component is loaded on descriptor dipole moment (μ) for which the W*[2] values were 0.906712. The equation was obtained with the descriptors: Y=51.5042+252.644η+0.899607μ+102.427q−(Y is the discoloration rate of dyes). The obtained QSPR model could be used for predicting the discoloration rate of dyes and also reveals our previous suspicion of catalytic mechanism.

TiO2-sludge carbon enhanced catalytic oxidative reaction in environmental wastewaters applications

The enhanced oxidative potential of sludge carbon/TiO2 nano composites (SNCs), applied as heterogeneous catalysts in advanced oxidation processes (AOPs), was studied. Fabrification of efficient SNCs using different methods and successful evaluation of their catalytic oxidative activity is reported for the first time. Surface modification processes of hydrothermal deposition, chemical treatment and sol-gel solution resulted in improved catalytic activity and good surface chemistry of the SNCs. The solids obtained after chemical treatment and hydrothermal deposition processes exhibit excellent crystallinity and photocatalytic activity. The highest photocatalytic rate was obtained for the material prepared using hydrothermal deposition technique, compared to other nanocomposites. Further, improved removal of bisphenol A (BPA) from aqueous phase by means of catalytic ozonation and catalytic wet air oxidation processes is achieved over the solid synthesized using chemical treatment method. The present results demonstrate that the addition of TiO2 on the surface of sludge carbon (SC) increases catalytic oxidative activity of SNCs. The latter produced from harmful sludge materials can be therefore used as cost-effective and efficient sludge derived catalysts for the removal of hazardous pollutants.

Wet air oxidation of resorcinol as a model treatment for refractory organics in wastewaters from the wood processing industry

Wastewater treatment systems are important tools to enhance sustainability in terms of reducing environmental impact and complying with sanitary requirements. This work addresses the wet air oxidation (WAO) process for pre-treatment of phenolic wastewater effluents. The aim was to increase biodegradability prior to a subsequent anaerobic stage. In WAO laboratory experiments using a micro-autoclave, the model compound resorcinol was degraded under different oxygen availability regims within the temperature range 150 °C–270 °C. The activation energy was determined to be 51.5 kJ/mol. Analysis of the products revealed that after 3 h of reaction at 230 °C, 97.5% degradation of resorcinol was achieved. At 250 °C and the same reaction time complete removal of resorcinol was observed. In this case the total organic carbon content was reduced down to 29%, from 118.0 mg/L down to 34.4 mg/L. Under these process conditions, the pollutant was only partially mineralized and the ratio of the biological oxygen demand relative to the chemical oxygen demand, which is 0.07 for resorcinol, was increased to a value exceeding 0.5. The main by-product acetic acid, which is a preferred compound for methanogenic bacteria, was found to account for 33% of the total organic carbon.

Polymerization of Aniline in Microemulsion by Catalytic Air Oxidation

SummaryA copper catalyzed air oxidation process is presented for polymerization of aniline in a microemulsion constituting with cetyltrimethylammonium chloride (CTAC) and n‐butanol. The process was demonstrated to give stable and pitch‐dark emulsions of Emeraldine base in molecular weights of 33800 Da, as inferred from the capillary viscometer. A fairly linear viscosity‐conversion relation was noted in each case up to 95.0% of conversion. Differential light scattering (DLS) measurements showed 70 nm of average particle size for the polyaniline (PANI) in the emulsion. Conductivities measured by four‐ point probe technique indicated conductivities 8.3×10−8 and 9.8 Scm−1 for un‐doped and doped PANI.

Holey Graphene Nanomanufacturing: Structure, Composition, and Electrochemical Properties

Topology is critical for properties and function of 2D nanomaterials. Membranes and films from 2D nanomaterials usually suffer from large tortuosity as a result from dense restacking of the nanosheets and thus have limited utility in applications such as electrodes for supercapacitor and batteries, which require ion transport through the nanosheet thickness. In comparison with conventional porous 2D nanomaterials, introducing holes through the nanosheets to create holey 2D nanomaterials with retention of the 2D‐related properties is a more viable approach to improve molecular transport. Here, graphene is used as a model to study the fundamental structure‐property relationship as a result from defect‐enabled hole creation. Specifically, the correlation of electrochemical capacitive properties with structure and composition for holey graphene materials is prepared using a highly scalable controlled air oxidation process. The presence of holes on graphene sheets is not sufficient to account for the observed capacitance improvement. Rather, the improvement is achieved through the combination of an enhanced mesopore fraction with simultaneous oxygen doping while retaining the graphitic carbon network with minimal damage. The detailed understanding might be further applied to other 2D materials toward a broader range of both energy‐related and other applications.

Thermal oxidation fabrication of NiO film for optoelectronic devices

In this work, NiO coating was fabricated by magnetron sputtering method on quartz and indium tin oxide (ITO) substrates in an inert gas ambient of Ar followed by a thermal oxidation process in air at 400°C for 2h. The NiO coating was analyzed by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and UV–vis spectrometer. A preliminary photovoltaic performance measurement of the as-prepared device (ITO/NiO/poly-TPD/PC71BM/Al) shows a short circuit current density (Jsc) of 5.6mAcm−2 and power conversion efficiency (PCE) of 1.5% under an illumination of 100mWcm−2. The PCE of device with NiO HTLs was ca. 20% higher than those of the devices based on PEDOT:PSS hole transport layers (HTLs). The thermal oxidation fabricated NiO coating may provide an excellent route to fabricate other NiO-based optoelectronic devices.

Macroporous ZnO foams by high internal phase emulsion technique: synthesis and catalytic activity.

Zinc(II) oxide nanoparticles were used for the stabilization of dicyclopentadiene (DCPD)-water-based high internal phase emulsions (HIPEs), which were subsequently cured using ring-opening metathesis polymerization (ROMP). The morphology of the resulting ZnO-pDCPD nanocomposite foams was investigated in correlation to the nanoparticle loading and nanoparticle surface chemistry. While hydrophilic ZnO nanoparticles were found to be unsuitable for stabilizing the HIPE, oleic acid coated, yet hydrophobic ZnO nanoparticles were effective HIPE stabilizers, yielding polymer foams with ZnO nanoparticles located predominately at their surface. These inorganic/organic hybrid foam-materials were subsequently calcined at 550 °C for 15 min to obtain inorganic macroporous ZnO foams with a morphology reminiscent to the original hybrid foam, and a specific surface area of 1.5 m(2) g(-1). Longer calcination time (550 °C, 15 h) resulted in a sea urchin like morphology of the ZnO foams, characterized by higher specific surface area of 5.5 m(2) g(-1). The latter foam type showed an appealing catalytic performance in the catalytic wet air oxidation (CWAO) process for the destruction of bisphenol A.