Oxidation rate in the preparation of polyferric sulfate coagulant

The oxidation rate of ferrous sulfate was investigated in the preparation of polyferric sulfate(PFS) coagulant. It was proved that this reaction is zero order with respect to Fe2+, first order with respect to NO2(g) and first order with respect to the interface area between gas phase and liquid phase. If the partial pressure of NO2(g) in gas phase is increased or the interface area is increased, the time needed to complete the reaction will be decreased.

Modeling of growth stress gradient effect on the oxidation rate at high temperature

A new oxidation kinetics model is established for high-temperature oxidation. We assume that the interface reaction is fast enough and the oxidation rate is controlled by diffusion process at high temperature. By introducing the growth stress gradient we modify the classical oxidation parabolic law. The modified factor of the oxidation rate constant is a function of growth strain, environment oxygen concentration, and temperature. The modeling results show that the stress gradient effect on the oxidation rate cannot be ignored. Growth strain will dominate whether the stress gradient effect promotes or slows down the oxidation process. The stress gradient effect becomes weaker at higher temperature. This effect is amplified at higher concentrations of environmental oxygen. Applied mechanical loads do not affect the oxidation rate. This model is available for high temperature oxidation of metals and alloys.

The combined effects of biomass and temperature on maximum specific ammonia oxidation rate in domestic wastewater treatment

Measurement and predicted variations of ammonia oxidation rate(AOR)are critical for the optimization of biological nitrogen removal,however,it is difficult to predict accurate AOR based on current models.In this study,a modified model was developed to predict AOR based on laboratoryscale tests and verified through pilot-scale tests.In biological nitrogen removal reactors,the specific ammonia oxidation rate(SAOR)was affected by both mixed liquor volatile suspended solids(MLVSS)concentration and temperature.When MLVSS increased 1.6,4.2,and 7.1-fold(1.3‒8.9 g/L,at 20℃),the measured SAOR decreased by 21%,49%,and 56%,respectively.Thereby,the estimated SAOR was suggested to modify when MLVSS changed through a power equation fitting.In addition,temperature coefficient(θ)was modified based on MLVSS concentration.These results suggested that the prediction of variations ammonia oxidation rate in real wastewater treatment system could be more accurate when considering the effect of MLVSS variations on SAOR.

Retarded thermal oxidation of strained Si substrate

Strained Si is recognized as a necessary technology booster for modem integrated circuit technology. However, the thermal oxidation behaviors of strained Si substrates are not well understood yet despite their importance. In this study, we for the first time experimentally find that all types of strained Si substrates （uniaxial tensile, uniaxial compressive, biaxial tensile, and biaxial compressive） show smaller thermal oxidation rates than an unstrained Si substrate. The possible mechanisms for these retarded thermal oxidation rates in strained Si substrates are also discussed.

Influence of N-type doping on the oxidation rate in n-type 6H-SiC

The doping dependence of dry thermal oxidation rates in n-type 6H-SiC was studied. The oxidation temperature ranged from 1050 to 1150℃ and the nitrogen doping concentration ranged from 9.53× 10^16, 1.44× 10^17, to 2.68×10^18 cm ^3. By combining the modified deal-grove model and Arrhenius equation, the linear and parabolic rate constants, and their corresponding activation energies were extracted. The results show that： higher temperature corresponded to thicker oxides; dry thermal oxidation rate in n-type 6H-SiC depended on the doping concentration; both linear-rate-constant and parabolic-rate-constant increased with the doping concentration; the parabolic activation energy increased from 0.082 to 0.104 e V, both linear and parabolic activation energies increasing with the doping concentration; and, the parabolic pre-exponential factor increased from 2.6 ×10^4 to 2.7 ×10^5nm^2/s, both linear and parabolic pre-exponential factor increasing with doping concentration. Moreover, the experiment also illustrated that it is unreasonable to use a variation of the Arrhenius activation energy to explain the doping dependence of thermal oxidation on SiC.

A QUANTITATIVE STUDY ON ENHANCEMENT OF TYPE Ⅱ PHOTOSENSITIZED OXIDATION REACTION RATE BY HEAVY WATER

A method for quantitative evaluating the enhancement of the rate of Type Ⅱ photosensitized oxidation by D_2O was suggested. The effect of substrate concentration on this process was also discussed.

Chemical looping partial oxidation over FeWOx/SiO2 catalysts

This paper describes the design of a FeWOx-based oxygen carrier for the chemical partial oxidation of methane(CLPOM).Thermodynamic screening and kinetic analyses both forecast the FeWOx-based oxygen carrier as a promising candidate for the production of syngas.The total methane conversion and syngas yield can be dramatically increased with this catalyst compared to the case with the unmodified WO3/SiO2,thereby enabling CLPOM with 62%methane conversion,93%CO gas-phase selectivity,94%H2 selectivity,and a 2.4 H2/CO ratio.The catalyst has the advantages of high availability of lattice oxygen to oxidize carbonaceous intermediates in time,together with the formation of an Fe-W alloy to promote the surface reaction.Consequently,it demonstrates excellent catalytic performance with no catalyst deactivation at 900°C and 1 atm.The excellent structural stability plays an essential role in CLPOM.As revealed via XPS and ICP,the phase segregation has not been observed due to the strong interaction between Fe and W,which resulted in the formation of the Fe-W alloy during the reduction processes and the match between the ion oxidation rates of the Fe and W ions in the oxidation stage.The results provide fundamental information on the reaction mechanism of FeWOx/SiO2,and present it as a promising candidate for CLPOM.

Effects of oxygen content on the oxidation process of Si-containing steel during anisothermal heating

The oxidizing behavior of Si-containing steel was investigated in an O2 and N2 binary-component gas with oxygen contents ranging between 0.5 vol% and 4.0 vol% under anisothermal-oxidation conditions. A simultaneous thermal analyzer was employed to simulate the heating process of Si-containing steel in industrial reheating furnaces. The oxidation gas mixtures were introduced from the commencement of heating. The results show that the oxidizing rate remains constant in the isothermal holding process at high temperatures; therefore, the mass change versus time presents a linear law. A linear relation also exists between the oxidizing rate and the oxygen content. Using the linear regression equation, the oxidation rate at different oxygen contents can be predicted. In addition, the relationship between the total mass gain and the oxygen content is linear; thus, the total mass gain at oxygen contents between 0.5 vol%–4.0 vol% can be determined. These results enrich the theoretical studies of the oxidation process in Si-containing steels.

Preparation of PFS coagulant by sectionalized reactor

The oxidation rate of ferrous sulfate is investigated for the preparation of polyferric sulfate(PFS) coagulant. It is proved that this reaction is zero order with respect to Fe 2+ , first order with respect to NO 2(g), and first order with respect to the interface area between gas phase and liquid phase. According to this mechanism, sectionalized reactor(SR) is used in place of traditional reactor(TR), and the liquid of reaction mixture is recycled by pump. As a result, not only the flow path of reaction liquid is prolonged, but also gas liquid contact area enlarged, and the reaction distinctly accelerated, compared with traditional reactor. The effects of parameters including temperature, acidity and others on the reaction rate are also discussed.

Simultaneous Oxidization of NO_x and SO_2 by a New Non-thermal Plasma Reactor Enhanced by Catalyst and Additive

The non-thermal plasma as one of the most promising technologies for removing NOx and SO2 has attrm^ted much attention. In this study, a new plasma reactor combined with catalyst and additive was developed to effectively oxidize and remove NOx and SO2 in the flue gas. The experimental results showed that TiO2 could improve the oxidation efficiency of SO2 in the case of applying plasma while having a negative effect on the oxidation process of NO and NOx. With the addition of NH3, the oxidation rates of NOx, NO and SO2 were slightly increased. However, the effect of adding NH3 on NOx oxidation was negative when the temperature was above 200℃.

Effect of non-vacuum storage condition on minimum explosible concentration of aluminum dust

Non-vacuum storage condition has a great impact on the explosion characteristics of aluminum powders. In this paper, vacuum-packed flake and globular aluminum powders stored in a dryer after opening the vacuum package are selected as the experimental samples, and a 20 L spherical explosion device is chosen to test the minimum explosible concentration (MEC) values of aluminum dusts under different storage time. The results show that the MEC values of two types of unoxidized aluminum powders are 30 g/m^3. The MEC values of flake and globular aluminum powders firstly go up with the increase of storage time in the dryer and then reach the maximum values of 50 g/m^3 and 60 g/m^3 at respective storage time until finally they stabilize gradually. The main reason is that the oxidation rate is faster owing to the bigger specific surface area of globular aluminum powders. Hence, the storage time has more significant effect on the MEC of globular aluminum powder than that of flake aluminum powder. After a period of time, the outer surface is oxidized to generate a layer of film, which prevents the further oxidation of aluminum powder, resulting in the temporary stability of MEC.

Oxidative effects of glyphosate on the lipophobic intracellular environment in the microalgae Chlorella vulgaris

The studied hypothesis is that the herbicide glyphosate(GLY)can affect the oxidative balance in the hydrophobic intracellular medium in non-target Chlorella vulgaris cells.Analytical GLY and RoundUp(RUP)supplementation,affected the growth profile.A significant 42%decrease in the cellular biomass in stationary(St)phase was observed in cultures supplemented with either 5μM of GLY or RUP,as compared to control cultures.The treatment with 0.3μM of GLY generated non-significant effects on the oxidation rate of 2’,7’dichlorofluorescein diacetate(DCFH-DA),neither in exponential(Exp)nor in St phase of development,as compared to control cultures.However,the treatment with either 5μM GLY or 0.3 and 5μM RUP lead to a significant decrease in the DCFH-DA oxidation rate,as compared to control cultures.The lipid radical(LR●)generation rate,detected by Paramagnetic Resonance Spectroscopy(EPR),was significantly increased in the presence of RUP,in Lag and Exp phase of growth.The non-enzymatic antioxidants,α-Tocopherol(α-T)andβ-Carotene(β-C),are aimed to protect membranes against the damage produced by the radical reactions.The content ofβ-C was not significantly affected,as compared to control cultures,by any of the treatments,in both growth phases of cellular development.The content ofα-T was significantly decreased by the supplementation with either 0.3 or 5μM of RUP or 5μM GLY.The LR●/α-T ratio,used as indicator of the oxidative balance in the hydrophobic cellular media,was significantly different between samples obtained from control and RUP-exposed microalgae in both,Exp and St phase of development,with either 0.3 or 5μM RUP.The data presented here showed evidence that suggested that oxidative balance in the hydrophobic environment was affected by either GLY or RUP.

Optimization of Fermentation Media for Enhancing Nitrite-oxidizing Activity by Artificial Neural Network Coupling Genetic Algorithm

Two artificial intelligence techniques, artificial neural network and genetic algorithm, were applied to optimize the fermentation medium for improving the nitrite oxidization rate of nitrite oxidizing bacteria. Experiments were conducted with the composition of medium components obtained by genetic algorithm, and the experimental data were used to build a BP (back propagation) neural network model. The concentrations of six medium components were used as input vectors, and the nitrite oxidization rate was used as output vector of the model. The BP neural network model was used as the objective function of genetic algorithm to find the optimum medium composition for the maximum nitrite oxidization rate. The maximum nitrite oxidization rate was 0.952 g 2 NO-2-N·(g MLSS)-1·d-1 , obtained at the genetic algorithm optimized concentration of medium components (g·L-1 ): NaCl 0.58, MgSO 4 ·7H 2 O 0.14, FeSO 4 ·7H 2 O 0.141, KH 2 PO 4 0.8485, NaNO 2 2.52, and NaHCO 3 3.613. Validation experiments suggest that the experimental results are consistent with the best result predicted by the model. A scale-up experiment shows that the nitrite degraded completely after 34 h when cultured in the optimum medium, which is 10 h less than that cultured in the initial medium.

A kind of double-sided porous anodic alumina membrane fabricated with the three-step anodic oxidation method

The porous anodic alumina membranes （PAAMs） have been successfully used as templates for the fabrication of functional nano-materials due to their outstanding regularity and physicochemical properties. In this paper, a transparent double-sided anodic alumina membrane with ultra-thin aluminum substrate was fabricated with the three-step anodic oxidation method in the oxalic acid electrolyte. The characters such as the top-surface morphology, membrane thickness, and depth of nanopores of this three-layer （A1203-A1-A1203） sandwiched nano-structure were controllable through regulating the main anodic oxidation conditions, e.g., anodic oxidation time of various steps, coating remove process. The experiments data revealed that the aluminum substrate is exponential declined with the oxidation time when it was approximately reduced by a few micrometers. This new double-sided anodic alumina membrane can be used as the high-quality functional field emission materials and templates.

Effect of slag composition on elements oxidation behavior of GH984G superalloy for electroslag remelting withdrawal process

The composition of a slag system has been shown to be particularly important and influential for the new technology of electroslag remelting withdrawal process.The oxidation of the GH984G alloy elements,in contact with different contents of CaF_(2)–CaO–Al_(2)O_(3)–MgO–TiO_(2)–SiO_(2)in various slag systems,has been investigated in the present study by performing slag–metal equilibrium experiments and ion and molecule coexistence theory analysis.The results show that CaF_(2)and MgO have only a minor effect on the oxidation rates of Al and Ti in the GH984G superalloys.However,it was found that SiO_(2)would intensify the oxidation degree of Al and Ti,and Al was found to become easier oxidized than Ti.Moreover,CaO was found to reduce the activity of SiO_(2)and,thereby,also the oxidation degree of Al and Ti.Also,TiO_(2)was found to reduce the oxidation rate of Ti and instead increase the oxidation rate of Al.Finally,the effect of Al_(2)O_(3)on the oxidation of Al and Ti was observed to be opposite to that of TiO_(2).The calculated results were found to be in good agreement with experimental measurements.Moreover,viscosity experiments showed that CaO would rapidly increase the viscosity of the slag at low temperatures,and that the viscosity of the slag would increase with an increase in SiO_(2)content.

Study on Oxidation Mechanism of Nitrogen Monoxide in Indoor Environment

With the aid of wind-tunnel. experimental setup, the possibilities that nitrogen monoxide (NO) is oxidized to nitrogen dioxide (NO2) in various environments were stucied, which include indoor, outdoor and darkroom conditions. By comparing their effects, a conclusion can be drawn that NO can be oxidized to NO2 in indoor environment with a low rate, and micro amount of ozone, propylene and methane can accelerate the reaction: 2NO + O-2-->NO2. The initial concentration of NO has effect on the oxidation rate. When the initial concentration of NO ranges between 500 and 900 mug/L, natural logarithm of initial rate and natural logarithm of initial concentration have a good linear relation, so do ln(1/[NO]) and the time (t). Besides that, the possible oxidation mechanism of indoor NO has also been studied.

Aerobic N_2O emission for activated sludge acclimated under different aeration rates in the multiple anoxic and aerobic process

Nitrous oxide（N_2O） is a potent greenhouse gas that can be emitted during biological nitrogen removal. N_2O emission was examined in a multiple anoxic and aerobic process at the aeration rates of 600 m L/min sequencing batch reactor（SBRL） and 1200 m L/min（SBRH）.The nitrogen removal percentage was 89% in SBRLand 71% in SBRH, respectively. N_2O emission mainly occurred during the aerobic phase, and the N_2O emission factor was 10.1%in SBRLand 2.3% in SBRH, respectively. In all batch experiments, the N_2O emission potential was high in SBRLcompared with SBRH. In SBRL, with increasing aeration rates, the N_2O emission factor decreased during nitrification, while it increased during denitrification and simultaneous nitrification and denitrification（SND）. By contrast, in SBRHthe N_2O emission factor during nitrification, denitrification and SND was relatively low and changed little with increasing aeration rates. The microbial competition affected the N_2O emission during biological nitrogen removal.

The effect of dissolved oxygen concentration on long-term stability of partial nitrification process

Dissolved oxygen(DO)concentration is regarded as one of the crucial factors to influence partial nitrification process.However,achieving and keeping stable partial nitrification under different DO concentrations were widely reported.The mechanism of DO concentration influencing partial nitrification is still unclear.Therefore,in this study two same sequencing batch reactors(SBRs)cultivated same seeding sludge were built up with realtime control strategy.Different DO concentrations were controlled in SBRs to explore the effect of DO concentration on the long-term stability of partial nitrification process at room temperature.It was discovered that ammonium oxidation rate(AOR)was inhibited when DO concentration decreased from 2.5 to 0.5 mg/L.The abundance of Nitrospira increased from 1011.5 to 1013.7 copies/g DNA,and its relative percentage increased from 0.056%to 3.2%during 190 operational cycles,causing partial nitrification gradually turning into complete nitrification process.However,when DO was 2.5 mg/L the abundance of Nitrospira was stable and AOB was always kept at 1010.7 copies/g DNA.High AOR was maintained,and stable partial nitrification process was kept.Ammonia oxidizing bacteria(AOB)activity was significantly higher than nitrite oxidizing bacteria(NOB)activity at DO of 2.5 mg/L,which was crucial to maintain excellent nitrite accumulation performance.

Modification of nitrifying biofilm into nitritating one by combination of increased free ammonia concentrations, lowered HRT and dissolved oxygen concentration

Nitrifying biomass on ring-shaped carriers was modified to nitritating one in a relatively short period of time （37 days） by limiting the air supply, changing the aeration regime, shortening the hydraulic retention time and increasing free ammonia （FA） concentration in the moving-bed biofilm reactor （MBBR）. The most efficient strategy for the development and maintenance of nitritating biofilm was found to be the inhibition of nitrifying activity by higher FA concentrations （up to 6.5 mg/L） in the process. Reject water from sludge treatment from the Tallinn Wastewater Treatment Plant was used as substrate in the MBBR. The performance of high-surfaced biocarriers taken from the nitritating activity MBBR was further studied in batch tests to investigate nitritation and nitrification kinetics with various FA concentrations and temperatures. The maximum nitrite accumulation ratio （96.6%） expressed as the percentage of NO 2 ？ -N/NOx ？ -N was achieved for FA concentration of 70 mg/L at 36°C. Under the same conditions the specific nitrite oxidation rate achieved was 30 times lower than the specific nitrite formation rate. It was demonstrated that in the biofilm system, inhibition by FA combined with the optimization of the main control parameters is a good strategy to achieve nitritating activity and suppress nitrification.

Effect of the addition of organic carbon sources on nitrous oxide emission in anaerobic-aerobic(low dissolved oxygen)sequencing batch reactors

The effect of additional organic carbon sources on the production of nitrous oxide(N_(2)O)in anaerobicaerobic(low dissolved oxygen)real wastewater treatment system was investigated.In this paper,three laboratoryscale sequencing batch reactors(SBRs)(SBR-1,SBR-2 and SBR-3)were operating under an anaerobic-aerobic(low dissolved oxygen,0.15-0.45 mg·L^(-1))configuration.The SBRs were‘long-term cultured’respectively with a single municipal wastewater sample,sodium acetate,and a waste-activated sludge alkaline fermentation liquid as the additional carbon sources of real wastewater.Off-gas analysis showed that N_(2)O was emitted into the atmosphere during the aerobic(low dissolved oxygen)period in the three SBRs,and the order of N_(2)O emission rate was SBR-2>SBR-1>SBR-3.It was observed that the higher poly-β-hydroxyvalerate fraction of polyhydroxyalkanoates,the lower glycogen transformation and less nitrite accumulation was in SBR-3,while the opposite behavior was observed in SBR-2.Further research indicated that the interaction of the factors above potentially affected the N_(2)O emission in the anaerobic-aerobic(low dissolved oxygen)system.