High O2 Concentrations Research Articles

Evaluation of Air Quality in Sudanese Gold Mining Fields

This study intended to provide a base line and describe the current air quality in Sudanese Gold mining fields. It covers 21 gold marketing centers in 5 states; namely Northern, River Nile, Gadaref, Red Sea and Kurdofan state. The main objectives of the survey is the detection of any significant concentrations that exceed Occupational Safety and Health norms and specifying the key emission sources, and also identification and assessing of the health hazards and environmental impacts. The tests were carried out by using electronic portable devices to measure the concentrations of pollutants in air. The measured pollutants were: Dust or Particulate Matter (PM), Nitrogen Dioxide (NO2), Volatile Organic Components (VOCs), Sulphur Dioxide (SO2), Ammonia (NH3), Carbon Monoxide (CO) and Ozone (O3). National Ambient Air Quality Standards (NAAQSs) and Sudanese Standards for Ambient Air Pollutants were used for comparison purposes. In addition to that, Air Quality Index (AQI) was applied for the average concentrations of each pollutant. It was found that, all gold marketing centers suffered from very high concentration of PM2.5 and PM10. 90.5% of those centers had higher NO2 concentration than the standards, 37% of it was increased by 200% and 42% of it was increased by 150%. In addition to that, 48% of gold marketing centers had higher SO2 concentration than the standards. On the other hand, concentrations of other pollutants obtained were found within the allowable limits. Finally, it was concluded that all those centers are contaminated with one or more air pollutants. Therefore, it was recommended to improve the environmental conditions by mitigating emissions from point sources. Supervisors have been advised to assume their responsibilities in controlling the use of Personal Protective Equipment (PPE) in addition to the dissemination of safety culture through psychological approach.

Ambient Air Quality and Emergency Hospital Admissions in Singapore: A Time-Series Analysis.

Air pollution exposure may increase the demand for emergency healthcare services, particularly in South-East Asia, where the burden of air-pollution-related health impacts is high. This article aims to investigate the association between air quality and emergency hospital admissions in Singapore. Quasi-Poisson regression was applied with a distributed lag non-linear model (DLNM) to assess the short-term associations between air quality variations and all-cause, emergency admissions from a major hospital in Singapore, between 2009 and 2017. Higher concentrations of SO2, PM2.5, PM10, NO2, and CO were positively associated with an increased risk of (i) all-cause, (ii) cardiovascular-related, and (iii) respiratory-related emergency admissions over 7 days. O3 concentration increases were associated with a non-linear decrease in emergency admissions. Females experienced a higher risk of emergency admissions associated with PM2.5, PM10, and CO exposure, and a lower risk of admissions with NO2 exposure, compared to males. The older adults (≥65 years) experienced a higher risk of emergency admissions associated with SO2 and O3 exposure compared to the non-elderly group. We found significant positive associations between respiratory disease- and cardiovascular disease-related emergency hospital admissions and ambient SO2, PM2.5, PM10, NO2, and CO concentrations. Age and gender were identified as effect modifiers of all-cause admissions.

Capacity of River Valleys to Retain Nutrients from Surface Runoff in Urban and Rural Areas (Southern Poland)

Studies on water quality are necessary, as catchments of small watercourses are exposed to anthropogenic influences associated with agricultural activities, settlement, transport and other undertakings, leading to water pollution. There has been insufficient research performed on the valley’s ability to retain nutrients during floods, contributing to water accumulation. The main object of the study was to identify the retention capacity of river valleys under various aspects of human urbanization. To represent soil water retention, the Soil Conservation Service Curve Number (SCS-CN) method was used. Spatiotemporal autoregressive models were exploited to investigate the relationship between pollutants in precipitation and surface water in rivers. In contrast, multivariate analysis was used to identify and reveal patterns of land use for specific chemical compounds in the headwaters. The canonical-correlation analysis (CCA) showed that Mg+2 and Ca+2 cations in rainwater and surface waters play the main roles in the geochemical cycle in urban and rural areas. In the urban catchment area, the strongest relations were found for NO3−, K+ and Na+. The average NO3− concentration in urban headwater was 8.3 mg·dm−3, the highest in the study area. The relationship between NO3− concentration in headwater and rainwater was found for all study catchments using spatial autoregression (SAR). High concentrations of SO42− in surface water have been identified in urban areas. Severe water erosion raises the risk of nutrient leaching in soils prone to surface runoff. As a consequence of low soil permeability and urbanization, retention capacity is significantly reduced in areas with low soil permeability. Land development plans should take spatial retention capacity into consideration. To ensure that large reservoirs can retain water in the face of climate change, riparian buffer zones (protective zones in valleys for small water bodies as well as Nature-based Solution) are important.

Solar-induced efficient propylparaben photodegradation by nitrogen vacancy engineered reticulate g-C3N4: Morphology, activity and mechanism

Propylparaben (PrP) has attracted extensive concerns due to its wide occurrence in wastewater and potential health risk. Herein, nitrogen vacancy engineered reticulate g-C3N4 (Nv-RCN) was successfully synthesized for the photodegradation of PrP. Nv-RCN exhibited larger specific surface area, greater light absorption ability, higher transfer and separation efficiency of charge carriers in comparison with bulk g-C3N4 (CN). According to the characterization results and DFT calculation, nitrogen vacancy could capture electrons and facilitate oxygen adsorption. The Nv-RCN exhibited an outstanding PrP removal efficiency of 94.3 %, and the corresponding apparent rate constant of Nv-RCN was 3.37 times higher than that of CN. High O2 concentration (8 mg/L) and low pH value (pH = 3) promoted PrP photodegradation based on Box-Behnken Design. The O2− was the major radical during PCOP of Nv-RCN, and could oxidize PrP by decarbonylation and dealkylation. This study provided new insights to the improvement of photodegradation performance of g-C3N4 for parabens removal and related environmental remediation.

The Effect of a Hybrid Pretreatment Device for CEMS on the Simultaneous Removal of PM2.5 and Water Vapor

Stationary emission sources still account for a significant portion of total air pollution emissions. Continuous emission monitoring systems (CEMS) have been used to estimate the emissions of stack pollutants. A large amount of moisture and other interfering factors in the sample discharged from a stack result in the loss of target gases due to artifact formation or gas absorption, thereby reducing measurement accuracy. Therefore, a pretreatment process is essential. Among various pretreatment technologies available, a cyclone with a rapid cooling unit is a special one that can be applied to remove particles and water vapor at the same time in CEMS. This study aimed at the simultaneous removal of water vapor and particles by operating a hybrid pretreatment device at low temperatures such as −5, −15, and −25 °C. When using the hybrid cyclone under the conditions of high temperature (180 °C), humidity (150 g/m3), PM2.5 (1 mg/m3), and SO2 (105.2 ppm) concentrations, the reduction rates of water vapor and PM2.5 concentration and the recovery rates of SO2 concentration were 82.2, 80.2, and 96.4%, respectively. These data suggested that the hybrid cyclone could be used as a pretreatment device for CEMS.

Association between ambient air pollution and polycystic ovarian syndrome: A 2010-2019 national populational-based cohort study in Korea

Background: Several studies have indicated that prenatal exposure to ambient air pollution is associated with an increased risk of gestational diabetes mellitus, hypertensive disorder during pregnancy, preterm birth, and stillbirth. However, no previous study has focused on the association between the number of pregnancy complications and exposure to ambient air pollution. Objectives: To investigate the association between prenatal exposure to ambient air pollutants and the number of pregnancy complications in high-risk pregnancies. Methods: We collected data on gestational diabetes mellitus, hypertensive disorder during pregnancy, preterm birth, and stillbirth from the National Health Information Databases, provided by the Korean National Health Insurance Service. To assess individual-level exposure to air pollutants, a spatial prediction model and area-averaging approach were used. Results: From 2015 to 2018, data of 789,595 high-risk pregnancies were analyzed. The ratio of gestational diabetes mellitus in the country was the highest, followed by preterm birth, hypertensive disorder during pregnancy, and stillbirth. Approximately 71.7% of pregnant women (566,143) presented with one pregnancy complication in identical pregnancies, 27.5% (216,714) presented with two, and 0.9% (6738) presented with three or more. Multiple logistic regression models with adjustments for age, residence, and income variables indicated that the risk of having two or more pregnancy complications was positively associated with the exposure to higher levels of PM10 (odds ratio [OR], 1.11; 95% confidence interval [CI], 1.09–1.12) and PM2.5 (OR, 1.14; 95% CI, 1.12–1.15). The highest quartile presented higher odds of two or more pregnancy complications compared with the lower three quartiles of PM10, PM2.5, CO, NO2, and SO2 exposures (p < 0.001). Conclusion: The results indicate that the risk of pregnancy complications is positively associated with the exposure to the high concentrations of PM10, PM2.5, CO, NO2, and SO2.

Spin-selected electron transfer in liquid–solid contact electrification

Electron transfer has been proven the dominant charge carrier during contact electrification at the liquid–solid interface. However, the effect of electron spin in contact electrification remains to be investigated. This study examines the charge transfer between different liquids and ferrimagnetic solids in a magnetic field, focusing on the contribution of O2 molecules to the liquid–solid contact electrification. The findings reveal that magnetic fields promote electron transfer at the O2-containing liquid–solid interfaces. Moreover, magnetic field-induced electron transfer increases at higher O2 concentrations in the liquids and decreases at elevated temperatures. The results indicate spin-selected electron transfer at liquid–solid interface. External magnetic fields can modulate the spin conversion of the radical pairs at the O2-containing liquid and ferrimagnetic solid interfaces due to the Zeeman interaction, promoting electron transfer. A spin-selected electron transfer model for liquid–solid contact electrification is further proposed based on the radical pair mechanism, in which the HO2 molecules and the free unpaired electrons from the ferrimagnetic solids are considered radical pairs. The spin conversion of the [HO2• •e−] pairs is affected by magnetic fields, rendering the electron transfer magnetic field-sensitive.

Resource utilization of high concentration SO2 for sulfur production over La–Ce-Ox@ZrO2 composite oxide catalyst

Sulfur dioxide is one of the main causes of air pollution such as acid rain and photochemical smog, and its pollution control and resource utilization become an important research direction of air pollution control. The active component La–Ce-Ox is loaded on SiO2, γ-Al2O3, TiO2 and ZrO2, and the La–Ce-Ox@ZrO2 exhibits the best catalytic activity. By adjusting the loading amount of La–Ce-Ox, La–Ce-Ox@ZrO2 with different mass fractions was prepared. The results show that the activity of 15%La–Ce-Ox@ZrO2 catalyst is the best. The SO2 conversion is 100%, and the S yield and S selectivity are more than 96% at 350 °C. According to the analysis results of H2-TPR, CO2-TPD and NH3-TPD, ZrO2 as a support not only reduces the acidity of the catalyst, but also improves the weak alkaline sites of the catalyst, which is conducive to the adsorption and activation of SO2 molecules at low temperature. The incorporation of La and Ce increases the oxygen concentration adsorbed on the catalyst. The strong interaction between the support ZrO2 and the active component La–Ce-Ox is conducive to the electron transfer between the active component and the support, and improves the activity of the catalyst. For the 15%La–Ce-Ox@ZrO2, the main reaction intermediates are weakly adsorbed SO2 (SO32−), bicoordinated CO32−, monodentate carbonate and CO in the gas phase. Therefore, the catalytic reaction follows both L-H and E-R mechanisms.

Improving Chemical Mechanical Polishing Efficiency of PZT with Less than 100 ppm SO4 2−

Excellent surface quality of lead zirconate titanate (PZT) is required to achieve high performance in micro-electro-mechanical systems. In this work, PZT-4 (Pb(Zr0.44Ti0.56)O3) was processed with chemical mechanical polishing (CMP). K2SO4 was used to enhance the CMP efficiency. The results reveal that at pH 4 and 6, as the K2SO4 concentration increases, the material removal rate (MRR) and surface roughness S a first increase, then decrease and stabilize. Interestingly, at pH 6, after adding only 55 ppm SO4 2−, the MRR increases by 54%. After CMP, the surface becomes smooth. No visible processing damage occurs in the substrate. For the CMP mechanism, SO4 2− in K2SO4 plays an essential role in the MRR enhancement. At pH 6, PbO can dissolve, forming oxygen vacancies. After adding a low concentration of SO4 2−, the negatively charged SO4 2− ions can be attracted by the positively charged oxygen vacancies. Then soluble Zr(SO4)2 can be formed, promoting the dissolution of Zr4+. As a result, the surface integrity can be destroyed. Therefore, the MRR is improved. However, with a high concentration of SO4 2−, the PbSO4 precipitates can inhibit dissolution and wear. Hence, the MRR is suppressed. This research may provide a feasible approach for high-efficiency CMP of PZT.

Sulfur cycle contributes to stable autotrophic denitrification and lower N2O accumulation in electrochemically integrated constructed wetlands: Electron transfers patterns and metagenome insights

Excessive discharge of nutrients from wastewater treatment plants (WWTPs) is an important pollutant source of eutrophic water bodies. In this work, three electrochemically integrated horizontal flow constructed wetlands (E-HFCWs) were developed for advanced nutrients removal from WWTPs effluent with different S/N ratios. In E-HFCWs, PO43−-P, NO3−-N and TN removal percentages at current of 0.2 A and hydraulic retention time (HRT) of 24 h did not differ significantly as S/N ratios altered. When fed with low, middle and high concentrations of SO42−-S wastewater during this period, PO43−-P removal percentages respectively reached 99.3 %±0.9 %, 99.2 %±1.1 % and 99.0 %±1.4 %, NO3−-N removal percentages respectively reached 99.5 %±0.5 %, 99.6 %±0.4 % and 99.4 %±0.8 %, and TN removal percentages respectively reached 92.0 %±2.5 %, 90.8 %±3.4 % and 91.2 %±2.7 %. This work highlighted that sulfur cycle played crucial roles in improving nitrogen removal stability as current or HRT decreased in higher S/N ratio groups. The formed sulfur ferrites under higher current or HRT condition served as “electron reservoir”, and would resupply electron for denitrification when electron supplied by electrolysis was deficient. In addition, the higher S/N ratio groups allowed significantly lower N2O accumulation, which was accordance with the concept of carbon neutral. Based on metagenome results, the occurrence of more abundant sulfur-oxidizing denitrifying genes and bacteria (e.g., Thiobacillus) in higher S/N ratio groups under lower current or HRT further demonstrated the significant roles of sulfur cycle in stable autotrophic denitrification performance in E-HFCWs. Overall, this work provides perspective on the future practical application for the regulation of nitrogen removal stability enhancement and N2O emission reduction in electrochemically integrated bioreactors.

Resin-based iron-manganese binary oxide for phosphate selective removal.

Adsorption technology can effectively remove phosphorus from water and realize phosphorus recovery. Hence, it is used to curb the eutrophication of water and alleviate the crisis caused by the shortage of phosphorus resources. Resin has been attracting increasing interest as an ideal adsorption material; however, its practical application is greatly affected by environmental factors. To solve the competitive adsorption and pore blockage caused by humic acid and coexisting ions during the removal of phosphorus by ion-exchange resin, this study has developed an iron-manganese oxide-modified resin composite adsorbent (Fe/Mn-402) based on the nanoconfinement theory. The structural characterization results of XRD, FT-IR, SEM, and XPS showed that the iron-manganese binary oxide was successfully loaded on the skeleton of the strongly alkaline anion resin and showed good stability under both neutral and alkaline conditions. The batch adsorption experiments showed that the maximum adsorption capacity of Fe/Mn-402 for phosphorus can reach up to 50.97mgg-1 under the optimal raw material ratio (Fe:Mn = 1:1). In addition, Fe/Mn-402 shows good selectivity for phosphorus removal. Fe/Mn-402 can maintain good adsorption performance for phosphate even under high concentrations of SO42-, HCO3-, and humic acid. The regenerated Fe/Mn-402 can be recycled without any obvious change in its treatment capacity. Hence, it is suitable for stable, long-term usage. In general, this work puts forward a new idea for the development of phosphorus-removal adsorbents for the treatment of wastewater containing coexisting ions and HA.

Effects of the upward-increasing gradient magnetic field on soot properties in ethylene inverse diffusion flames with different oxygen concentrations

The effects of the upward-increasing gradient magnetic field on soot properties are experimentally investigated in ethylene inverse diffusion flames with different oxygen concentrations. The soot morphology, nanostructure, graphitization degree, and oxidation reactivity are obtained by high-resolution transmission electron spectroscopy (HRTEM), X-ray diffractometer (XRD), and thermogravimetric analyzer (TGA), respectively. The upward-increasing gradient magnetic field is induced by two Nd-Fe-B permanent magnets with different thicknesses. The results show that the magnetic field influences the soot properties mainly by affecting the distributions of paramagnetic O2 and OH radicals in the flames. The soot samples are more graphitized in the flame with higher O2 concentration, which contains a longer fringe length and smaller fringe tortuosity. Fullerene-like structures are more apparent with increasing oxygen content. The soot fringe length decreases and fringe tortuosity increases when the upward-increasing gradient magnetic field is applied. The application of the magnetic field enhances the soot oxidation reactivity, and it shows the greatest effect on the oxidation reactivity of soot produced in the flame with 21% O2 content.

Removal of sulfate and chloride ions from reverse osmosis concentrate using a two-stage ultra-high lime with aluminum process

Reverse osmosis (RO) concentrate generated from RO desalination is necessary to be managed due to its discharge toxicity and mineral scaling. In this work, the removal of SO42− and Cl− from RO concentrate and further improvement of water quality were systematically investigated using the two-stage ultra-high lime with aluminum (UHLA) process and carbonation post-process, respectively. Firstly, batch results of the one-stage UHLA process proved the competitive inhibition effect of coexisting SO42− on Cl− removal. Thus, a two-stage UHLA process was designed to preferentially precipitate SO42− as ettringite (Ca6Al2(SO4)3(OH)12) in stage I and then dislodge partial Cl− as Friedel's salt (Ca4Al2Cl2(OH)12) in stage II. Results showed that almost all of SO42− and 77.8 % of Cl− could be removed at the optimal conditions. And the XRD and SEM analysis results showed formation of ettringite and Friedel's salt with good crystal morphology in stage I and stage II, respectively. This technology was further applied in the real RO concentrate treatment and achieved almost complete SO42− removal and high Cl− removal of 70.5 %, which confirmed the feasibility and effectiveness of the two-stage UHLA process. Finally, the carbonation post-process was applied to precipitate remaining Ca2+ as well as lower the pH and conductivity, so as to improve the treated water quality. This two-stage UHLA process is promising to be applied to saline wastewater containing high concentrations of SO42− and Cl−.

Long-term air pollution levels modify the relationships between short-term exposure to meteorological factors, air pollution and the incidence of hand, foot and mouth disease in children: a DLNM-based multicity time series study in Sichuan Province, China

BackgroundEpidemiological studies have investigated the short-term effects of meteorological factors and air pollution on the incidence of hand, foot, and mouth disease (HFMD). Several meteorological indicators, such as relative humidity and the diurnal temperature range (DTR), significantly modify the relationship between short-term exposure to temperature and HFMD incidence. However, it remains unclear whether (and how) long-term air pollution levels modify the short-term relationships of HFMD incidence with meteorological factors and air pollution.MethodsWe obtained daily data on meteorological factors, air pollutants, and HFMD counts in children from 21 prefecture-level cities in Sichuan Province in Southwest China from 2015 to 2017. First, we constructed a distributed lag nonlinear model (DLNM) at each prefecture-level site to evaluate the short-term impacts of meteorological variables and air pollutants on HFMD incidence. Then, we assessed the pooled effects of the exposures and incorporated long-term city-specific air pollutant indicators as meta-predictors to examine their potential modification effects by performing multivariate meta-regression models.ResultsWe found that long-term SO2 and CO concentrations significantly modified the short-term relationships between climatic variables and HFMD incidence. Specifically, high concentrations of CO (P = 0.027) and SO2 (P = 0.039) reduced the risk of HFMD at low temperatures. The relationship between relative humidity and HFMD incidence was weakened at high SO2 concentrations (P = 0.024), especially when the relative humidity was below the median level. When the minimum relative humidity (32%) was compared to the median relative humidity (77%), the risk ratio (RR) was 0.77 (95% CI: 0.51–1.17) in the 90th percentile of SO2 (19.6 μg/m3) and 0.41 (95% CI: 0.27–0.64) in the 10th percentile of SO2 (10.6 μg/m3).ConclusionOur results indicated that long-term SO2 and CO levels modified the short-term associations between HFMD incidence in children and meteorological variables. These findings may inform health authorities to optimize targeted public health policies including reducing ambient air pollution and reinforcing self-protective actions to weaken the adverse health impacts of environmental factors on HFMD incidence.

Electron power absorption in capacitively coupled neon–oxygen plasmas: a comparison of experimental and computational results

Phase resolved optical emission spectroscopy (PROES) measurements combined with 1d3v particle-in-cell/Monte Carlo collisions (PIC/MCC) simulations are used to study the electron power absorption and excitation/ionization dynamics in capacitively coupled plasmas (CCPs) in mixtures of neon and oxygen gases. The study is performed for a geometrically symmetric CCP reactor with a gap length of 2.5 cm at a driving frequency of 10 MHz and a peak-to-peak voltage of 350 V. The pressure of the gas mixture is varied between 15 Pa and 500 Pa, while the neon/oxygen concentration is tuned between 10% and 90%. For all discharge conditions, the spatio-temporal distributions of the electron-impact excitation rate from the Ne ground state into the Ne 2p53p0 state measured by PROES and obtained from PIC/MCC simulations show good qualitative agreement. Based on the emission/excitation patterns, multiple operation regimes are identified. Localized bright emission features at the bulk boundaries, caused by local maxima in the electronegativity are found at high pressures and high O2 concentrations. The relative contributions of the ambipolar and the Ohmic electron power absorption are found to vary strongly with the discharge parameters: the Ohmic power absorption is enhanced by both the high collisionality at high pressures and the high electronegativity at low pressures. In the wide parameter regime covered in this study, the PROES measurements are found to accurately represent the ionization dynamics, i.e. the discharge operation mode. This work represents also a successful experimental validation of the discharge model developed for neon–oxygen CCPs.

Dramatic changes in aerosol composition during the 2016–2020 heating seasons in Beijing–Tianjin–Hebei region and its surrounding areas: The role of primary pollutants and secondary aerosol formation

With the implementation of a series of air pollution mitigation strategies during the past decade, great air quality improvements have been observed in the BTH region. Despite of significant decreases in gaseous pollutants, such as SO2 and NO2, the enhancement of secondary aerosol formation was observed. NO3− has surpassed SO42− and OM to become the dominant PM2.5 component. We find that the reduction of POC mainly dominated the decreasing trend of OC. As for secondary inorganic components, the key processes or factors controlling the spatial-temporal variation characteristics were different. The areas with large SO42− concentrations corresponded well to those with high SO2 concentrations, while the synchronized NO3− better followed spatial patterns in O3 than NO2. From 2016 to 2020, the response of SO42− to SO2 was close to a linear function, while the reaction of NO3− to the decrease of NO2 displayed nonlinear behavior. Such different relationships indicated that SO42− was predominantly controlled by SO2, while NO3− was not only related to NO2 but also determined by the secondary conversion process. The ratios of SO42−, NO3−, NH4+, and OC to EC between 2016 and 2020 were generally higher than 1 in typical BTH cities, and the ratio of NO3− to EC was exceptionally high, with a range reaching up to 200 %. Besides, this ratio coincided well with the enhancement of Ox, indicating the potential role of Ox to secondary NO3− formation. The diurnal cycle of NO3−, O3, and NO2 concentration change rate indicated that the relative increase of O3 during nighttime may offset the effectiveness of NOX emission reduction. This study provided observational evidence of enhanced secondary NO3− formation with the rising trend of atmospheric oxidation and emphasized the importance of nighttime chemistry for NO3− formation in the BTH region.

Numerical study of the influence of O2 admixture on the propagation and F-containing species distribution of He/CF4 atmospheric pressure plasma jet

O2 impurity in the working gas of an He/CF4 atmospheric pressure plasma jet (APPJ) can affect the discharge dynamics and the density of reactive species. Therefore, a two-dimensional (2D) fluid model is built in order to explore the influence of an O2 admixture on the propagation and F-containing species distribution of He/CF4 APPJ. The addition of 0.1% O2 accelerates the ionization rates of APPJ due to the increase of Penning ionization reactions of O2, resulting in the increases of axial speed and F-containing reactive species (CF4+, CF3+, CF2+, CF+, F+, CF3, F, CF3−) when APPJ approaches the dielectric surface. The addition of O2 has the inhibitory effect on the rise of some F-containing reactive species (CF3+ and F). As O2 concentration increases to 2%, the concentration of F-containing reactive species shows a downward trend due to the increase of excitation energy loss and an electron attachment reaction of O2. Different from the axial speed, the radial speed decreases continuously with the increase of O2 because of the high O2 concentration on the dielectric surface when APPJ propagates radially. This also results in a reduced distribution of reactive species fluxes. The excitation energy loss and electronegativity of O2 and CF4 in the case of He + 0.5% CF4 + 0.5% O2 have been presented in this paper. It is discovered that excitation energy loss of O2 is stronger than that of CF4, but the electronegativity of CF4 is stronger than that of O2.

Sulfammox forwarding thiosulfate-driven denitrification and anammox process for nitrogen removal

The coupled process of thiosulfate-driven denitrification (NO3−→NO2−) and Anammox (TDDA) was a promising process for the treatment of wastewater containing NH4+-N and NO3−-N. However, the high concentration of SO42− production limited its application, which needs to be alleviated by an economical and effective way to promote the application of TDDA process. In this study, TDDA process was started in a relatively short time by stepwise replacing nitrite with nitrate and operated continuously for 146 days. Results presented that the average total nitrogen removal efficiency of 82.18% can be acquired at a high loading rate of 1.98 kg N/(m3·d) with maximum nitrogen removal efficiency up to 87.04%. It was observed that the increase of S/N ratio improved the denitrification efficiency and slightly inhibit the Anammox process. Batch tests showed that Sulfammox process appeared in TDDA process under certain conditions, further contributing 2.59% nitrogen removal and 10.46% sulfur removal (14.42 mg/L NH4+-N and 37.68 mg/L SO42--S were removed). This finding was mainly attributed to the reduction of sulfate in TDDA system to elemental S0 or HS−, which subsequently was used as an electron donor to realize the recycling of sulfate (SO42--S) pollutants and promote the sulfur-nitrogen (S–N) cycle. High-throughput analysis displayed that Anammox bacteria (Candidatus_Kuenenia), Sulfur-oxidizing bacteria (Thiobacillus) with relatively high abundance of 5.37%, 7.74%, respectively, guaranteeing the excellent nitrogen and sulfate removal performance in the reactor. The enrichment of phyla Chloroflexi (31.79%), Proteobacteria (31.82%), class Ignavibacteriales (10.55%), genus Planctomycetes (13.57%) further verified the exitence of Sulfammox process in the TDDA reactor. This study provides a new perspective for the practical application of TDDA in terms of reducing the production of high concentration SO42− and saving operational cost and strengthening deeply nitrogen removal.

Sulfur tolerance and self-regeneration mechanism of Na-Ru/Al2O3 dual function material during the cyclic CO2 capture and catalytic methanation

The combined CO2 capture and methanation with Dual Function Materials (DFM) is emerging as a vibrant field of research for its potential to increase the efficiency and reduce the cost of current multistage CCU processes. In this work, we set out to investigate for the first time the impact of sulfur poisoning over a Na-Ru/Al2O3 DFM operated in a fixed bed reactor with alternate feeds under realistic conditions including the presence of SO2, H2O and O2 in the process gas stream. The results of the extensive characterization of the fresh and sulfated (reaction-aged) DFM evidenced a remarkable intrinsic tolerance of the combined CO2 capture and methanation process to high concentrations of SO2 in the feed due to a self-regeneration mechanism of the Ru catalytic sites.

Multiple pollutants control of NO, benzene and toluene from coal-fired plant by Mo/Ni impregnated TiO2-based NH3-SCR catalyst: A DFT supported experimental study

There was a dearth of understanding regarding the mechanism of MPC catalyst activity and the creation of effective MPC catalysts for industrial low oxygen and high SO2 concentration environments. Herein, Mo/Ni was utilized to modify the commonly used WVTiOX catalyst to investigate the role and reaction mechanism of Mo/Ni in the MPC process. Mo/Ni doping greatly improved the MPC performance of the WVTiOX catalyst, increased the number of Brønsted and Lewis acid sites on the surface, promoted surface active oxygen Oα ratio, and intensified metal oxide synergy. The TiO2 (001) models of WVTiOX and NiWVTiOX catalysts were built, and the adsorption energies of NH3, O2, NO, C6H6, and C7H8 gaseous molecules on the surfaces of the two catalysts were calculated by density functional theory (DFT). The DFT and in situ DRIFTS results proved that NH3-SCR process of the catalyst was mainly governed by the L-H mechanism, while the E-R mechanism also worked to a certain extent. The following are possible benzene and toluene oxidation pathways on NiWVTiOX: C6H6 → C6H4O2 → C4H2O3 → CO2 + H2O and C7H8 → C6H5CH2OH → C6H5CHO → C6H5COOH → C4H2O3 → CO2 + H2O.