Insights into the mechanism of multiple Cu-doped Co Fe2O4 nanocatalyst activated peroxymonosulfate for efficient degradation of Rhodamine B

The multiple metal catalyst as a promising nanomaterial has shown excellent activity in the peroxymonosulfate (PMS) activation for pollutant degradation.However,the role of special sites and in-depth understanding of the PMS activation mechanism are not fully studied.In this study,a Cu-doped CoFe₂O₄nanocatalyst (0.5CCF) was synthesized by a sol-gel and calcination method,and used for PMS activation to remove Rhodamine B (RhB).The results showed that the Cu doping obviously ...     

Multiple isotopes reveal the driving mechanism of high NO–3 level and key processes of nitrogen cycling in the lower reaches of Yellow River

The continuous increase of nitrate (NO₃^–) level in rivers is a hot issue in the world.However,the driving mechanism of high NO₃^–level in large rivers is still lacking,which has limited the use of river water and increased the cost of water treatment.In this study,multiple isotopes and source resolution models are applied to identify the driving mechanism of high NO₃^–level and key processes of nitrogen cycling in the lower reaches ...     

Choice of precipitant and calcination temperature of precursor for synthesis of NiCo2O4 for control of CO–CH4 emissions from CNG vehicles

Compressed natural gas(CNG)is most appropriate an alternative of conventional fuel for automobiles.However,emissions of carbon-monoxide and methane from such vehicles adversely affect human health and environment.Consequently,to abate emissions from CNG vehicles,development of highly efficient and inexpensive catalysts is necessary.Thus,the present work attempts to scan the effects of precipitants(Na_2CO_3,KOH and urea)for nickel cobaltite(Ni Co_2O_4)catalysts prepared by co-precipitation from nitrate solutions and calcined in a lean CO-air mixture at 400°C.The catalysts were used for oxidation of a mixture of CO and CH_4(1:1).The catalysts were characterized by X-ray diffractometer,Brunauer–Emmett–Teller surface-area,X-ray photoelectron spectroscopy;temperature programmedreductionandScanningelectronmicroscopycoupledwith Energy-Dispersive X-Ray Spectroscopy.The Na_2CO_3was adjudged as the best precipitant for production of catalyst,which completely oxidized CO-CH_4mixture at the lowest temperature(T_(100)=350°C).Whereas,for catalyst prepared using urea,T_(100)=362°C.On the other hand the conversion of CO-CH_4mixture over the catalyst synthesized by KOH limited to 97%even beyond 400°C.Further,the effect of higher calcination temperatures of 500 and600°C was examined for the best catalyst.The total oxidation of the mixture was attained at higher temperatures of 375 and 410°C over catalysts calcined at 500 and 600°C respectively.Thus,the best precipitant established was Na_2CO_3and the optimum calcination temperature of 400°C was found to synthesize the Ni Co_2O_4catalyst for the best performance in CO-CH_4oxidation.     

Activity and hydrothermal stability of CeO2–ZrO2–WO3 for the selective catalytic reduction of NOx with NH3

A series of CeO_2–ZrO_2–WO_3(CZW)catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction(SCR)of NO with NH_3 over a wide temperature of 150–550°C.The effect of hydrothermal treatment of CZW catalysts on SCR activity was investigated in the presence of 10% H_2O.The fresh catalyst showed above 90% NO_x conversion at 201–459°C,which is applicable to diesel exhaust NO_x purification(200–440°C).The SCR activity results indicated that hydrothermal aging decreased the SCR activity of CZW at low temperatures(below 300°C),while the activity was notably enhanced at high temperature(above 450°C).The aged CZW catalyst(hydrothermal aging at 700°C for 8 hr)showed almost 80% NO_x conversion at 229–550°C,while the V_2O_5–WO_3/TiO_2 catalyst presented above 80% NO_x conversion at 308–370°C.The effect of structural changes,acidity,and redox properties of CZW on the SCR activity was investigated.The results indicated that the excellent hydrothermal stability of CZW was mainly due to the CeO_2–ZrO_2 solid solution,amorphous WO_3 phase and optimal acidity.In addition,the formation of WO_3 clusters increased in size as the hydrothermal aging temperature increased,resulting in the collapse of structure,which could further affect the acidity and redox properties.     

Highly selective catalytic reduction of NOxby MnOx–CeO2–Al2O3 catalysts prepared by self-propagating high-temperature synthesis

We first present preparation of MnOx–CeO_2–Al_2O_3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis(SHS) method, and studied the application of these catalysts to the selective catalytic reduction of NOxwith NH3(NH_3-SCR).Using the catalyst with 18 wt.% Mn(18 MnCe1Al2), 100% NO conversion was achieved at 200°C and a gas hourly space velocity of 15384 hr-1, and the high-efficiency SCR temperature window, where NO conversion is greater than 90%, was widened to a temperature range of 150–300°C. 18 MnCe1Al2 showed great resistance to SO_2(100 ppm)and H_2O(5%) at 200°C. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller(BET) analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and H_2 temperature programmed reduction. The characterization results showed that the surface atomic concentration of Mn increased with increasing Mn content, which led to synergism between Mn and Ce and improved the activity in the SCR reaction. 18 MnCe1Al2 has an extensive pore structure,with a BET surface area of approximately 135.4 m~2/g, a pore volume of approximately 0.16 cm~3/g, and an average pore diameter of approximately 4.6 nm. The SCR reaction on 18 MnCe1Al2 mainly followed the Eley-Rideal mechanism. The performances of the MnOx–CeO_2–Al_2O_3 catalysts were good, and because of the simplicity of the preparation process,the SHS method is applicable to their industrial-scale manufacture.     

Trend and seasonal variations of atmospheric CH4 in Beijing

The atmospheric CH4 in Beijing is still increasing, even though its increasing rate has significantly decreased from 1.76 ％/a during 1985-1989 to 0.50 ％/a during 1990-1997. The seasonal variation of CH4 concentration showed a double-peak pattern, one peak appearing in winter and the other in summer. It is evident that the annually seasonal variations of atmospheric CH₄ in Beijing are different. From 1986 to 1997, the atmospheric CH₄ increased by 185 ppbv, 37％ and 21％ of which were due to the increase in winter and in summer, respectively. After 1993, the annually seasonal increasing rate of CH4 concentration in summer (due to emission from biogenic sources) is negative while the increasing rate in winter (due to emission from non-biogenic sources) is positive about 25 ppbv/a. As a result, the increase of CH₄ emission from non-biogenic sources in winter is the major reason that caused theannually seasonal increasing rate from 1993 to 1997. The biogenic sources in Beijing are shrinking while the non-biogenic ones (such as fossil fuel combustion) are enlarging.     

Investigation into the roles of interfacial H2O structure in catalytic oxidation of HCHO and CO over CuMnO2 catalysts

The rapid deactivation of cost-effective MnO₂-based catalysts in humid air limits their application in practice,and the identification of the role of water in an oxidation process is significant for developing water-resistant MnO₂-based catalysts.Here,CuMnO₂showed a20.3%HCHO conversion in 10 hr at room temperature in humid air with relative humidity of 40%,but deactivated in 3 hr in dry air.The excellent activity and stability of HCHO oxidation in humid air were ...     

Nano-sized Fe2O3/Fe3O4 facilitate anaerobic transformation of hexavalent chromium in soil–water systems

The purpose of this study is to investigate the effects of nano-sized or submicro Fe_2O_3/Fe_3O_4 on the bioreduction of hexavalent chromium(Cr(VI)) and to evaluate the effects of nano-sized Fe_2O_3/Fe_3O_4 on the microbial communities from the anaerobic flooding soil.The results indicated that the net decreases upon Cr(VI) concentration from biotic soil samples amended with nano-sized Fe_2O_3(317.1 ± 2.1 mg/L) and Fe_3O_4(324.0 ± 22.2 mg/L) within21 days,which were approximately 2-fold of Cr(VI) concentration released from blank control assays(117.1 ± 5.6 mg/L).Furthermore,the results of denaturing gradient gel electrophoresis(DGGE) and high-throughput sequencing indicated a greater variety of microbes within the microbial community in amendments with nano-sized Fe_2O_3/Fe_3O_4 than the control assays.Especially,Proteobacteria occupied a predominant status on the phylum level within the indigenous microbial communities from chromium-contaminated soils.Besides,some partial decrease of soluble Cr(VI) in abiotic nano-sized Fe_2O_3/Fe_3O_4 amendments was responsible for the adsorption of nano-sized Fe_2O_3/Fe_3O_4 to soluble Cr(VI).Hence,the presence of nano-sized Fe_2O_3/Fe_3O_4 could largely facilitate the mobilization and biotransformation of Cr(VI) from flooding soils by adsorption and bio-mediated processes.     

Sorption of Perfluorooctane sulfonate（PFOS） including its isomers on hydrargillite as a function of pH,humic substances and Na2SO4

Perfluorooctane sulfonate（PFOS） is a persistent organic pollutant（POP） and emergent contaminant that are widespread in the environment. Understanding the mechanisms controlling the distribution of PFOS and its isomers between hydrargillite and the water phase is important in order to study their redistribution and mobility in the environment. This study investigated the effects of pH, humic acid, fulvic acid and Na₂SO₄ on sorption of PFOS isomers to hydrargillite. A mixture...     

Regulation of PM2.5on mitochondrial damage in H9c2 cells through miR-421/SIRT3 pathway and protective effect of miR-421 inhibitor and resveratrol

Fine particulate matter (PM_2.5) exposure is associated with cardiovascular disease (CVD)morbidity and mortality.Mitochondria are sensitive targets of PM_2.5,and mitochondrial dysfunction is closely related to the occurrence of CVD.The epigenetic mechanism of PM_2.5-triggered mitochondrial injury of cardiomyocytes is unclear.This study focused on the mi R-421/SIRT3 signaling pathway to investigate the regulatory mechanism in cardiac mitochondrial dynamics imbalance ...     

An estimate of the conversion rates of SO_2 to SO_4~(2-)- and NO_2 to HNO_(3+) NO_3~- for the evaluation air pollution in Beijing

The conversion rates of SO2 to SO42- and NO2 to HNO3+NO3- are estimated from the field-data obtained in Beijing in summer, 1988. The results show that the conversion rate of NO2 is about four times as much as that of SO2; The conversion rates have a diurnal variation in a day. On the average, the rate of SO2 is estimated to be 4.7% h-1 during the daytime and 3.4% h-1 during the nighttime. Similarly, the rate of NO2 is estimated to be 17.2% h-1 and 12% h-1 respectively.     

One-step preparation of a novel graphitic biochar/Cu0/Fe3O4 composite using CO2-ambiance pyrolysis to activate peroxydisulfate for dye degradation

Herein,a one-step co-pyrolysis protocol was adopted for the first time to prepare a novel pyrogenic carbon-Cu⁰/Fe₃O₄ heteroatoms (FCBC) in CO₂ ambiance to discern the roles of each component in PDS activation.During co-pyrolysis,CO₂ catalyzed formation of reducing gases by biomass which facilitated reductive transformation of Fe³⁺ and Cu²⁺ to Cu⁰ and Fe₃O₄,respectively.According to the a...     

Multi-process production occurs in the iron and steel industry,supporting ‘dual carbon' target: An in-depth study of CO2 emissions from different processes

Reducing CO₂emissions of the iron and steel industry,a typical heavy CO₂-emitting sector is the only way that must be passed to achieve the‘dual-carbon’goal,especially in China.In previous studies,however,it is still unknown what is the difference between blast furnace basic oxygen furnace (BF-BOF),scrap-electric furnace (scrap-EF) and hydrogen metallurgy process.The quantitative research on the key factors affecting CO₂emissions is insufficient There is also a l...     

Preparation and characterization of Fe2O3-CeO2-TiO2/γ-Al2O3 catalyst for degradation dye wastewater

In order to develop a catalyst with high activity for catalytic wet oxidation （CWO） process at room temperature and atmospheric pressure, Fe2O3-CeO2-TiO2/γ-Al2O3 catalyst was prepared by consecutive impregnation method and the prepared parameters were optimized. The structure of the catalyst was characterized by BET, XRF, SEM and XPS technologies, and the actual wastewater was used to investigate the catalytic activity of Fe2O3-CeO2-TiO2/γ-Al2O3 in CWO process. The experimental results showed that the prepared catalyst exhibited good catalytic activity when the doping amount of Ti was 1.0 wt% （the weight ratio of Ti to carriers）, and the middle product, Fe2O3-CeO2-TiO2/γ-Al2O3, was calcined in 450℃ for 2 h. The CWO experiment for treating actual dye wastewater indicated that the COD, color and TOC of actual wastewater were decreased by 62.23%, 50.12% and 41.26% in 3 h, respectively, and the ratio of BOD5/COD was increased from 0.19 to 0.30.     

Unraveling SO2-tolerant mechanism over Fe2（SO4）3/TiO2 catalysts for NOx reduction

Developing low-temperature SO₂-tolerant catalysts for the selective catalytic reduction of NO_x is still a challenging task. The sulfation of active metal oxides and deposition of ammonium bisulfate deactivate catalysts, due to the difficult decomposition of the as-formed sulfate species at low temperatures（<300 °C）. In recent years, metal sulfate catalysts have attracted increasing attention owing to their good catalytic activity and strong SO₂ tolerance at hi...     

Investigations on removal of SO2 from flue gas by aerosol formation in pulsed corona discharge process

The removal of SO₂ from flue gas by pulsed corona discharge in presence of ammonia was experimentally investigated. The results showed that the SO₂ removal mainly depends on thermal reaction of SO₂ with NH₃ and enhancements of 0%—25% by pulsed corona discharge in the range of the specific energy 0—5 Wh/Nm³. The aerosol mass concentration, mainly composed of ammonium sulfate, increased with specific energy dissipated into the reactor. With an initial concentration of 2000—2100 ppmv SO₂ and energy consumption of 3 Wh/Nm³, when a stoichiometric amount of ammonia is injected, the removal efficiency of SO₂ and percentage of ammonium sulfates in reaction products are all ≥80%. The collection efficiency of the reactor for aerosol is about 74% at a flue gas temperature of 60 to 65℃ and a water vapor content of 9% to 11% volume.     

Insights into the interface of NiCo2O4 spinel/LaCoO3 perovskite nano-composite for CO and soot oxidation

In the quest for the development of thermally stable, highly active and low-cost catalysts for use in catalyzed diesel particulate filter, nano-composites are new areas of research. Therefore, we reported the easy synthesis of spinel NiCo₂O₄/perovskite LaCoO₃ nano-composite,and its individual oxides NiCo₂O₄and LaCoO₃ for comparison. The detailed insights into the physio-chemical characteristics of formed NiCo₂O₄     

Enhanced dechlorination of 2,4-dichlorophenol by recoverable Ni/Fe–Fe3O4 nanocomposites

Ni/Fe-Fe_3O_4 nanocomposites were synthesized for dechlorination of 2,4-dichlorophenol(2,4-DCP). The effects of the Ni content in Ni/Fe-Fe_3O_4 nanocomposites, solution pH, and common dissolved ions on the dechlorination efficiency were investigated, in addition to the reusability of the nanocomposites. The results showed that increasing content of Ni in Ni/Fe–Fe_3O_4 nanocomposites, from 1 to 5 wt.%, greatly increased the dechlorination efficiency; the Ni/Fe–Fe_3O_4 nanocomposites had much higher dechlorination efficiency than bare Ni/Fe nanoparticles. Ni content of 5 wt.% and initial p H below 6.0 was found to be the optimal conditions for the catalytic dechlorination of 2,4-DCP. Both 2,4-DCP and the intermediate product 2-chlorophenol(2-CP) were completely removed, and the concentration of the final product phenol was close to the theoretical phenol production from complete dechlorination of 20 mg/L of 2,4-DCP, after 3 hr reaction at initial p H value of 6.0,3 g/L Ni/Fe-Fe_3O_4 , 5 wt.% Ni content in the composite, and temperature of 22℃. 2,4-DCP dechlorination was enhanced by Cl-and inhibited by NO3-and SO_4~(2-). The nanocomposites were easily separated from the solution by an applied magnetic field. When the catalyst was reused, the removal efficiency of 2,4-DCP was almost 100% for the first seven uses, and gradually decreased to 75% in cycles 8–10. Therefore, the Ni/Fe–Fe_3O_4 nanocomposites can be considered as a potentially effective tool for remediation of pollution by 2,4-DCP.     

Newly developed Fe3O4–Cr2O3 magnetic nanocomposite for photocatalytic decomposition of 4-chlorophenol in water

Chlorophenols, typically 4-chlorophenols are highly toxic and non-biodegradable organic contaminants which pose serious threat to the environment, particularly when released into aqueous medium. The removal of these pollutants by efficient method has received worldwide concern in recent past. A new Fe_3O_4–Cr_2O_3 magnetic nanocomposite was synthesized by wet chemical method under ultrasonic irradiation. Microstructure and morphology of the nanocomposite were characterized by powder X-ray diffraction(XRD),Fourier transform infrared(FT-IR), and a transmission electron microscope(TEM). Magnetic and optical properties were studied by a vibrating sample magnetometer(VSM) and an ultraviolet–visible(UV–Vis) spectrophotometer respectively. The magnetic nanocomposite(MNC) was used as photocatalyst for effective decomposition of 4-chlorophenol in water under ultraviolet(UV) irradiation.     

Spatial distribution of fossil fuel derived CO2 over India using radiocarbon measurements in crop plants

Examining the contribution of fossil fuel CO₂to the total CO₂changes in the atmosphere is of primary concern due to its alarming levels of fossil fuel emissions over the globe,specifi cally developing countries.Atmospheric radiocarbon represents an important observationa constraint and utilized to trace fossil fuel derived CO₂(CO_2ff) in the atmosphere.For the firs time,we have presented a detailed analysis on the spatial distribution of fossil fuel der...