Initial O2 Concentration Research Articles

Differential Reshaping of Skin and Intestinal Microbiota by Stocking Density and Oxygen Availability in Farmed Gilthead Sea Bream (Sparus aurata): A Behavioral and Network-Based Integrative Approach.

Fish were kept for six weeks at three different initial stocking densities and water O2 concentrations (low-LD, 8.5 kg/m3 and 95-70% O2 saturation; medium-MD, 17 kg/m3 and 55-75% O2 saturation; high-HD, 25 kg/m3 and 60-45% O2 saturation), with water temperature increasing from 19 °C to 26-27 °C. The improvement in growth performance with the decrease in stocking density was related to changes in skin and intestinal mucosal microbiomes. Changes in microbiome composition were higher in skin, with an increased abundance of Alteromonas and Massilia in HD fish. However, these bacteria genera were mutually exclusive, and Alteromonas abundance was related to a reactive behavior and systemic growth regulation via the liver Gh/Igf system, while Massilia was correlated to a proactive behavior and a growth regulatory transition towards muscle rather than liver. At the intestinal level, microbial abundance showed an opposite trend for two bacteria taxa, rendering in a low abundance of Reyranella and a high abundance of Prauserella in HD fish. This trend was correlated with up-regulated host gene expression, affecting the immune response, epithelial cell turnover, and abiotic stress response. Most of the observed responses are adaptive in nature, and they would serve to infer new welfare indicators for increased stress resilience.

Treatment of pistachio processing industry wastewaters by supercritical water oxidation in a continuous-flow reactor

ABSTRACT The objective of the present study is the treatment of pistachio processing industry wastewaters (PPIW) using the supercritical water oxidation method. The experiments were conducted within a 400–600°C temperature range and a 30–150 s reaction time range, while maintaining a constant pressure of 25 MPa and using an O2/COD ratio of 1:1. To observe the effects of the initial PPIW and O2 concentrations on the treatment efficiency, experiments were also conducted with O2/COD ratios ranging from 0.5 to 3, while maintaining a constant reaction temperature and time of 500°C and 60 s, respectively. The influence of reaction temperature, reaction time and O2/COD ratio on the total organic carbon (TOC) and total nitrogen (TN) contents of the liquid PPIW effluents were investigated. Treatment efficiencies up to 99.75% regarding TOC conversion and 78.72% regarding TN conversion were obtained in very short reaction times. Additionally, the kinetics of oxidation of PPIW was studied, and reaction rate expressions based on TOC and TN were proposed.

An experimental investigation into the fate of fuel-bound N-species during fluidised bed combustion of a dried coal slime in O2/Ar mixtures

The formation of NO, NO2, N2O and N2 from fuel-bound nitrogen species during the combustion of a coal slime (CS) and its char (CS char) were investigated in a laboratory bench-scale fluidised bed reactor by tracking the N-containing gas species using a gas chromatograph and an electrochemical gas analyser. Quartz sand with a particle size fraction of 0.3–0.38 mm was used as the bed material. A stream of an Ar/O2 mixture of varying O2 concentration was used as the oxidant and fluidisation gas. The effect of operating temperature (900–1300 K), initial O2 concentration (3–8%), fuel feed rate (0.0041 g min−1 for CS, 0.0036 g min−1 for CS char) and C/O2 mole ratio (0.14–0.78) on carbon burnout, NOx, N2O and N2 formation were systematically studied. It was found that the oxidation process of CS in the fluidised bed is controlled by mass diffusion under the tested conditions. N2, N2O and NO concentrations in the flue gas during CS combustion were higher than during CS char combustion under the same experimental conditions due to the presence of the greater N content in CS (1.56%) than in CS char (1.34%). At low combustion temperatures of 900 K and 1000 K, the fuel-N was mainly converted to NO and N2O. However, as the operating temperature increased, NO and N2 became the dominating species in both the CS and CS char combustion experiments. The NO concentration increased with increasing initial O2 concentration due to enhanced oxidation of char-N. Comparing the N2 formation data during CS and CS char combustion, it is inferred that in the presence of volatile, fuel-N was preferentially converted to N2.

Alleviating hypoxia through self-generating oxygen and hydrogen peroxide fluorinated chitosan: Insights from a kinetic study

Effective methods to alleviate hypoxia are necessary for the proper healing of chronic wounds. However, current oxygen (O2) delivery methods suffer from limitations, such as low O2 capacity and short supply time, burst release, and inadequate O2 preservation potential. This study presents a new approach utilising fluorinated chitosan (PFC-chitosan) infused with self-generating and preserving O2 and hydrogen peroxide (H2O2). We incorporated calcium peroxide (CaO2)-loaded polycaprolactone (PCL) particles into the PFC-chitosan matrix and subsequently evaluated the release kinetics of O2 and H2O2 from these materials. The incorporation of CaO2 into PCL particles and PFC-chitosan effectively mitigate the rapid decomposition rate of CaO2 while the PFC groups enable the dissolution of generated O2 via Van der Waals interactions. The apparent rate constant (kO2) for O2 release from CaO2 under hypoxia decreased from 1.194 µM−1h−1 to 0.141 µM−1h−1 by incorporating into PCL particles and PFC-chitosan, indicating the slower release of O2 from these materials. Regarding release kinetics, H2O2 follows a pseudo-zero-order pattern, while O2 exhibits a pseudo-first-order pattern. The kO2 is affected by temperature, pH, initial O2 concentration in the release media, and an initial amount of CaO2. The particles with PFC-chitosan showed higher cell viability and slower O2 release rates, indicating improved angiogenesis potential. The simultaneous generation of O2 and H2O2 from PFC-chitosan may have the potential to improve chronic wound healing by providing a continuous supplying of O2.

Zero-Dimensional Ignition Model of Boron Agglomerates.

Boron primarily exists in the form of agglomerates in ramjet combustion chambers. However, the model used to predict the ignition time of boron agglomerates is usually based on the single-particle assumption, resulting in inaccurate predictions. This study aims to develop a numerical model that can accurately describe the ignition of boron agglomerates. The model is based on the ignition model of a single particle boron proposed by the group of Kuo. Thiele modulus and effectiveness factor are introduced to represent the diffusion resistance of reaction gases in the pores of boron agglomerates. The model includes the necessary physical processes to accurately predict the ignition time. The rates of evaporation and heterogeneous reactions involved in the oxide layer removal process are corrected based on the fact that the diffusion rate of (BO)n in the liquid oxide layer equals to its consumption rate at the oxide-air interface. To evaluate the accuracy of the model, the obtained results for ignition time are compared with experimental data, showing reasonable consistency between them. The model is then applied to investigate the ignition characteristics of boron agglomerates. Parameters, such as initial average pore diameter, oxide layer thicknesses, initial particle diameter, O2 concentration, H2O concentration, and environmental pressure, are studied for their effects on the ignition time. In summary, the boron ignition model established in this study is a powerful tool to investigate the ignition mechanisms and characteristics of boron agglomerates. It can be further coupled with flow analysis for the detailed simulation of turbulent combustion in ramjet combustors.

Amaranth wastewater treatment by intensified ozonation in a rotating zigzag bed

This study investigated the treatment of amaranth wastewater by ozone (O3) in a rotating zigzag bed (RZB), in which a high gravity environment was created to intensify O3 mass transfer and enhance the degradation of amaranth. The degradation effect of amaranth was evaluated in terms of decolorization rate of the wastewater and removal rate of chemical oxygen demand under various operating conditions. Intermediate products of amaranth degradation were also investigated to elucidate the degradation mechanisms of amaranth. Results show that the degradation efficiency generally increased with increase in initial pH, rotational speed of RZB, initial O3 concentration, gas flow rate but declined with increase in both liquid flow rate and initial amaranth concentration. The decolorization rate of the wastewater reached 92.8 % within a liquid retention time of several seconds in the RZB, suggesting that RZB can significantly enhance the mass transfer rate of O3 into liquid and thus improve the degradation efficiency of amaranth.

Photocatalytic Properties of TiO2 for the Degradation of O3: Examined by Environmental Parameters

Background: This paper describes how environmentally relevant parameters affect titanium dioxide's photocatalytic properties (TiO2) to decompose ozone (O3). Methods: Thus, experiments have been carried out in a box chamber with TiO2 coated roofing membrane samples to determine the significance of light intensity, temperature, initial O3 concentration, and relative humidity. Furthermore, an outdoor experiment was conducted where the roofing membrane was subjected to natural sunlight. Results: The results show a significant photocatalytic effect of TiO2. The half-life of the O3 decay curve is 5.8 min in near-ambient UV-light exposure compared with 7.1 min in dark conditions. Experiments conducted at higher light intensity show a more extensive degradation of O3, where the value of the reactive uptake coefficient increases from 0.044 to 0.051. Also, the measurements carried out under natural sunlight show a photocatalytic effect where the uptake coefficient value is 0.046. A larger photocatalytic effect is detected for the experiments conducted at 283 K and 303 K temperatures compared with experiments under standard conditions. Conclusion: Experiments carried out with a very high initial concentration of O3 show that 28.1 μg of O3 is decomposed in ambient conditions, where 2.3 μg is destroyed. This demonstrates that light intensity, temperature, ozone concentration, and relative humidity significantly impact TiO2's degradation of O3.

Effects of sulfation on the ash fusibility and minerals evolution of corn straw during oxy-fuel combustion

Oxy-biomass combustion is an important technology for achieving negative CO2 emission. However, during oxy-biomass combustion, a series of ash-related problems are induced because of the accumulation of recycled SO2. In this study, the effects of SO2 on the ash fusibility were systematically investigated through ash fusion temperatures (AFTs) tests, scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectrometer (ICP-OES), X-ray diffraction (XRD), and chemical thermodynamics calculation (FactSage). Besides, the relevance among minerals evolution, melting performance, and ash sulfation was established. It was found that the presence of SO2 suppressed the release of K and Ca species, thereby increasing the AFTs of corn straw, while this depended heavily on the SO2 concentration, the duration of ash sulfation, and the initial concentration of O2. Furthermore, two reacting mechanisms, including moderate and excessive sulfation, were proposed in this work. When the initial SO2 concentration was less than 1000 ppm, AFTs increased due to the transformation of alkaline chlorides to their sulfates and aluminosilicates with the presence of SiO2 and Al2O3 in ash samples, which was named as moderate sulfation. When the concentration of SO2 was higher than 1000 ppm, large amounts of KAlSi3O8, CaAl2Si2O8, Ca2Al2SiO7 and CaSO4 were generated, causing the simultaneous eutectic and CaO-assisted melting, thereby decreasing the AFTs of corn straw, which was named as excessive sulfation.

Degradation of nitrobenzene by high-gravity intensified heterogeneous catalytic ozonation with Mn-Fe/ZSM-5 catalysts

In this study, high-gravity intensified heterogeneous catalytic ozonation is proposed for degradation of nitrobenzene (NB) in wastewater using Mn-Fe/ZSM-5 as the packing of the high-gravity rotating packed bed (RPB). The effects of inlet O3 concentration, liquid flow rate, initial pH, and high-gravity factor on the removal rate of total organic carbon (TOC) at room temperature are investigated and compared with that in a bubbling reactor (BR), and the degradation mechanism is also discussed. The results show that under the optimal conditions of the high-gravity factor β = 20, initial O3 concentration CO3 = 25 mg/L, liquid flow rate QL = 60 L/h, and initial pH = 6, the removal rate of TOC reaches 72% after 40 min. The removal rate of TOC in RPB is 33.5% higher than that in BR. The radical quenching experiment shows that •OH plays a dominant role in high-gravity intensified heterogeneous catalytic ozonation with Mn-Fe/ZSM-5. It is concluded that high-gravity intensified heterogeneous catalytic ozonation with Mn-Fe/ZSM-5 can effectively improve the degradation efficiency of organic wastewater.

Shock tube and kinetic study on auto-ignition characteristics of methanol/n-heptane mixtures at high temperature

The development of methanol/diesel dual-fuel engines urgently requires further study on chemical kinetic models for binary fuels. Ignition delay of lean and stoichiometric methanol/n-heptane mixtures (30/70, 50/50, 70/30, and 90/10) diluted with argon was investigated at high temperature (T = 1195 K–1514 K) and low pressure (p = 2 bar) using an aerosol shock tube and a detailed LLNL3.1 mechanism. The results indicated that LLNL3.1 mechanism agreed well with the current measurements. An increase in methanol can accelerate the ignition process at Ф = 1, because of the key radical---HO2, produced by CH2OH + O2=CH2O + HO2, which was affected by the methanol concentration. HO2 would subsequently attack the parent fuels and combine with H radical (HO2+H = 2OH), leading to the booming radical pool. For lean mixtures, n-heptane promoted the reactivity of system due to its high sensitivity to reaction H + O2=O + OH. The higher initial O2 concentration expedited this reaction and shortened the IDT. Besides, both methanol and n-heptane undergo H-abstraction reaction mostly by H radical, however, these reactions showed an inhibition effect on reactivity. This is caused by the competition for H radical between O2 and the parent fuels. Also, the fuel radicals, produced by C7H15-3, had a low decomposition reaction rate thus slowing down the chain branching and suppressing the reactivity of system.

Oxygen concentrations regulate NO, N2O, and N2 kinetics and nitrogen transformation in a fluvo-aquic soil using a robotized incubation system

The current study aimed to (1) investigate the responses of N gases (NO, N2O, and N2) and mineral N (NH4+, NO2−, and NO3−) to the different O2 availability; (2) better understand the importance of O2 availability on N2O production pathways; and (3) provide evidence for making N2O mitigation measures in this agricultural soil. An incubation experiment with a fluvo-aquic soil was conducted using a robotized incubation system, with two added nitrogen sources (NH4+, NO2−) under two initial O2 concentrations (21% and 0% v/v). Gas samples (3.5 ml) were collected every 8 h during the incubation, and soil samples were destructed collected at the beginning and the end of the incubation. Under initial condition of 21% O2, NH4+ combined with NO2− increased N2O emission especially at high NH4+ concentration (150 mg N kg−1). It is possibly because strong nitrification with high NH4+ addition caused a low O2 availability (< 6.2% v/v) which might have stimulated nitrifier denitrification or denitrification with N2O emission, and under initial condition of 0% O2, denitrification and anammox were the dominant processes, and N loss via gas depended on NO2− and NO3− concentration in the soil. Anammox might occur when NH4+ and NO2− were present, and this process should not be overlooked under anaerobic condition at the studied soil. O2 controlled the soil microbiome processes in the fluvo-aquic soil under current conditions. Under aerobic condition, nitrification and nitrification-related process (nitrifier denitrification or denitrification) were the main N2O sources, and the nitrogenous gas kinetics depended on the rates of exogenous N and N types; while under anaerobic condition, denitrification contributed the most N2O and N2 production, which closely related with NO2− and NO3− concentration in the soil.

Rapid degradation of refractory organic pollutants by continuous ozonation in a micro-packed bed reactor

Recently microreactor technology attracts attention due to the excellent multiphase mixing and enhanced mass transfer. Herein, a continuous ozonation system based on a micro-packed bed reactor (μPBR) was used to improve the dissolution rate of ozone and achieved a rapid and efficient degradation of refractory organic pollutants. The effects of liquid flow rate, gas flow rate, initial pH, initial O3 concentration and initial phenol concentration on the phenol and chemical oxygen demand (COD) removal efficiencies were also investigated. Experimental results showed that phenol and COD removal efficiencies under optimal conditions achieved 100.0% and 86.4%, respectively. Compared with large-scale reactors, the apparent reaction rate constant in μPBR increased by 1-2 orders of magnitude. In addition, some typical organic pollutants (including phenols, antibiotics and dyes) were treated by ozonation in μPBR. The removal efficiencies of these organic pollutants and COD achieved 100.0% and 70.2%–80.5% within 71 s, respectively. In this continuous treatment system, 100% of the unreacted ozone was converted to oxygen, which promoted the healthy development of aquatic ecosystems. Thus, this continuous system based on μPBR is a promising method in rapid and efficient treating refractory organic pollutants.

Characteristics and Kinetics Study of Mercury Re-emission Inhibited by DTCR in Simulated Desulfurization Slurry

The mercury re-emission characteristics and inhibition effect of sodium dithiocarbamate (DTCR) on mercury re-emission in a simulated desulfurization slurry were investigated. The effects of the desulfurization slurry parameters (including slurry temperature, initial pH value, O2 concentration, and Cl– concentration) on mercury re-emission with and without DTCR were explored. Moreover, the kinetic parameters (reaction order, reaction rate constant, and apparent activation energy) of mercury re-emission and inhibition were calculated by the experimental data. The results showed that addition of DTCR could effectively reduce the mercury re-emission from the desulfurization slurry. The mercury re-emission was enhanced with increases of the slurry temperature and initial pH, while O2 and Cl– in the slurry could inhibit the mercury re-emission. Further study shows that the mercury re-emission reaction processes in the desulfurization slurry with and without DTCR are both consistent with the pseudo-first-order kinetics. In the absence of DTCR, the reaction rate constant of mercury re-emission is 0.01888 min–1, and the apparent activation energy is 44.59 kJ/mol. In the presence of 0.002% DTCR, the reaction rate constant of mercury re-emission is 0.01126 min–1 and the apparent activation energy is 49.08 kJ/mol. Moreover, the effects of slurry parameters on the reaction rate constant were also explored. The present findings are valuable for coal-fired power plants to control mercury re-emission from a desulfurization slurry.

Effects of oxygen tension on the microbial community and functional gene expression of aerobic methane oxidation coupled to denitrification systems.

Aerobic CH4 oxidation coupled to denitrification (AME-D) can not only mitigate the emission of greenhouse gas (e.g., CH4) to the atmosphere, but also reduce NO3- and/or NO2- and alleviate nitrogen pollution. The effects of O2 tension on the community and functional gene expression of methanotrophs and denitrifiers were investigated in this study. Although higher CH4 oxidation occurred in the AME-D system with an initial O2 concentration of 21% (i.e., the O2-sufficient condition), more NO3--N was removed at the initial O2 concentration of 10% (i.e., the O2-limited environment). Type I methanotrophs, including Methylocaldum, Methylobacter, Methylococcus, Methylomonas, and Methylomicrobium, and type II methanotrophs, including Methylocystis and Methylosinus, dominated in the AME-D systems. Compared with type II methanotrophs, type I methanotrophs were more abundant in the AME-D systems. Proteobacteria and Actinobacteria were the main denitrifiers in the AME-D systems, and their compositions varied with the O2 tension. Quantitative PCR of the pmoA, nirS, and 16S rRNA genes showed that methanotrophs and denitrifiers were the main microorganisms in the AME-D systems, accounting for 46.4% and 24.1% in the O2-limited environment, respectively. However, the relative transcripts of the functional genes including pmoA, mmoX, nirK, nirS, and norZ were all less than 1%, especially the functional genes involved in denitrification under the O2-sufficient condition, likely due to the majority of the denitrifiers being dormant or even nonviable. These findings indicated that an optimal O2 concentration should be used to optimize the activity and functional gene expression of aerobic methanotrophs and denitrifiers in AME-D systems.

Improved NO removal from flue gas by hydrazine and its mechanism analysis

AbstractBACKGROUNDSelective non‐catalytic reduction (SNCR) is a proven technique to lessen nitric oxide (NO) emissions from stationary sources. However, the process using ammonia or urea as a reducing agent is only effective in a narrow and high temperature window, with the maximum NO abatement declining when increasing the oxygen (O2) content. Large industrial boilers may be often under a variable load and an excess of O2, which could decrease the effectiveness of the de‐NOx process. This study investigated hydrazine (N2H4) as a reagent to improve SNCR performance.RESULTSNO reduction by N2H4 was experimentally investigated in a pilot‐scale flow reactor. The effect of reaction temperature, molar ratio of NH2 to NO (normalized stoichiometric ratio, NSR), initial NO level and O2 concentration on the NO reduction in flue gas containing 7.4–17.4% (v/v) O2 at temperatures between 450 and 1100 °C was determined. The experimental results indicated that NO reduction by N2H4 was possible in dual temperature ranges, and the optimum reaction temperatures were about 580 and 1060 °C at NSR = 2.0. Moreover, the N2H4–NO reaction is less O2‐sensitive. A chemical kinetic model was developed to correctly describe the non‐catalytic reduction of NO by N2H4 in the presence of O2.CONCLUSIONHydrazine‐based SNCR is an alternative method for NO reduction occurring in dual temperature ranges and excess O2. The present model provided a satisfactory prediction of the experimental results, offering an effective tool for process simulation over a wide range of operating conditions. © 2019 Society of Chemical Industry

Ozone removal efficiency of the KI-denuder in the carbonyl sampling

In the carbonyl sampling of 2, 4- dinitrophenylhydrazine (DNPH) impregnated cartridge, the ozone removal was necessary because ozone reacted with the DNPH derivatives. A commercial ozone scrubber was usually used to remove O3. However, high humidity leaded to carbonyl compounds being trapped on the ozone scrubber before passing through the DNPH cartridge. The purpose of this study was to assess the ozone removal by KI-denuder under the climatic conditions of Ho Chi Minh City. Several parameters including air sampling flow rate and denuder length were optimized to achieve the highest removal efficiency. The optimum parameters of the KI denuder were the sampling flow rate of less than 1 L/min, and the denuder length of 20 cm. The effect of the initial O3 concentration on the removal efficiency was also investigated. Finally, the ozone removal efficiency of KI-denuder was compared to that of ozone scrubber when two devices were applied for the carbonyl sampling during field measurement. The results show that KI-denuder could be used to replace the ozone scrubber with high removal efficiency, particularly in high humidity condition. In conclusion, KI-denuder was effective, simple, easy to use and cheap. Therefore, it was encouraged to use in carbonyl sampling.

Volatile metabolites, quality and sensory parameters of “Ferrovia” sweet cherry cold stored in air or packed in high CO2 modified atmospheres

Volatile organic compounds, quality and sensory attributes of sweet cherry cv “Ferrovia”, cold packaged in Air or in different modified atmospheres (Low-O2 = 1% O2/0.03% CO2; High-CO2 = 16% O2/20% CO2; Mix = 1% O2/20% CO2), were monitored until 21 days of conservation. Results showed that sweet cherry cv “Ferrovia” is sensitive to CO2 accumulation (over 20%) in low oxygen (about 1%) modified atmosphere, as showed by the increase in respiration rate, biosynthesis of fermentative volatile metabolites, and sensory perception of off-odours. However, High-CO2 treatment seemed to preserve quality and sensory traits, presumably due to the high initial concentration of O2 (16%) that could limit the synthesis of ethyl esters and γ-butyrolactone, keeping the accumulation of off-flavours below their sensory perception threshold. Finally, PLSR analysis allowed to select 1-pentanol as putative marker of sensory alteration and hexanal and 2-hexenal as possible predictors of freshness for “Ferrovia” sweet cherries.

Experimental characterization of self-heating behavior of charcoal from eucalyptus wood

The long cooling time of charcoal produced from eucalyptus pyrolysis is due in part to the heat generation in oxidation reactions at low temperatures. The intensity of this reactions depends on complex interactions between the interstitial gas and the solid matrix. The objective of this paper was to investigate the kinetics of the self-heating phenomena due to charcoal oxidation at low temperatures and at different oxygen concentrations. Samples of 230 g of charcoal were subjected to heating in a steel reactor at constant temperature, from 100 to 300 °C, and oxygen concentrations ranging from 20.9 to 10%. Was evidenced that the rate of oxygen consumption increases with charcoal temperature at rates that depend on the initial concentration of O2. The beginning of the oxidation reactions was observed at 67 °C in atmospheres with 20.9% O2. The overall activation energy for the self-heating phenomenon was 17,790 J mol−1 and its intensity was increased with the temperature and O2 concentration.

Kinetics and mechanism of Pseudoanabaena cell inactivation, 2-MIB release and degradation under exposure of ozone, chlorine and permanganate

The organic pollutants produced by cyanobacteria cells, such as off-flavor compounds (e.g. 2-methylisoborneol, 2-MIB) and hazardous toxins (e.g. microcystins), are commonly detected in water sources. Although studies have shown that oxidation using potassium permanganate (KMnO4), chlorine and ozone helps to remove cyanobacteria cells, the potential effects of these oxidants on cell viability and the release of off-flavor substances have scarcely been explored. This study investigated the impacts of three widely used oxidants on Pseudanabaena sp. (a common species of 2-MIB producing cyanobacteria) inactivation, and on the release and degradation of intracellular 2-MIB. Experiments using KMnO4 showed that both the cell viability and 2-MIB release fit to a two-stage second-order kinetic model with a threshold of KMnO4 exposure (ct). No significant variations in the cell viability and 2-MIB release occurred until the exposure reached ct because KMnO4 was primarily consumed by the dissolved and cell-bound organic matters before it damaged the cell. However, chlorine permeates the cell membrane more easily, causing rapid algae inactivation and the subsequent cell lysis and 2-MIB release. Unlike permanganate and chlorine, which are unable to degrade the released 2-MIB because of their insufficient oxidation potentials, ozone is capable to inactivate the cell and degrade 2-MIB as well. When the initial O3 concentration is above a certain level (1.0 mg ·L−1 in this study), the released 2-MIB can be substantially oxidized. Therefore, the choice of a suitable oxidant and a proper dose is highly important in the control of off-flavor compounds during the treatment of algae-containing raw water.

Effects of acidic gases and operation parameters on denitrification in oxy-fuel CO2 compression process

Oxy-fuel combustion technology has great potential as a technically feasible method to significantly reduce CO2 emissions from coal-fired power plants. In an oxy-fuel combustion system, gas impurities such as SO2 and NOx must be removed before CO2 recovery because they can cause potential corrosion risk to CO2 compression and purification units (CPU). An attractive strategy is to simultaneously remove SO2 and NOx in the existing CO2 CPU system in place of traditional flue gas treatment device. Since NOx contains more than 90% of insoluble NO, the removal of NO has attracted much attention. In this study, NO removal efficiency in CO2 compression process were experimentally investigated on a pressurized reaction system. Effects of acidic gases (SO2, CO2) and operation parameters (pressure, temperature, initial O2 concentration and residence time) were taken into consideration. NO removal was achieved in pressurized reaction system as a result of oxidation to NO2 in the presence of O2 and the absorption of NO2 in water. NO conversion to NO2 was the key step for NO removal, which was strongly and positively dependent on the pressure and negatively dependent on the temperature. With the addition of 1000 ppm SO2 in simulated gases, NO removal efficiency was reduced by 8.1% at 2.0 MPa. The gas phase and liquid phase reactions between SO2 and NO2 suggested that partial NO2 was converted to insoluble NO when reacting with SO2. It was also found that NO removal efficiency in O2/CO2 atmosphere was slightly higher than that in O2/N2 atmosphere. The dissolution of CO2 in water increased the residence time as well as the acidity of the aqueous solution, which could facilitate the oxidation of NO.