The homogeneous and heterogeneous reactions in the boundary-layer of a flat surface are considered. The autocatalysts are assumed to be of regular sizes, while the solution is a dilute nanofluid. The heat release due ...The homogeneous and heterogeneous reactions in the boundary-layer of a flat surface are considered. The autocatalysts are assumed to be of regular sizes, while the solution is a dilute nanofluid. The heat release due to the chemical reactions is taken into account. The Buongiorno’s model is used to describe the behaviors of this reaction system. This configuration makes the current model be different from all previous publications. Multiple solutions are given numerically to the rescaled nonlinear system, whose stability is verified. The results show that the strength coefficients of the homogeneous and heterogeneous reactions are key factors to cause the appearance of the multiple solutions in the distribution of the chemical reactions. Nanofluids enhance the diffusion of heat and help maintain the stability of chemical reactions.展开更多
Oxidized starch powder and cationic starch solution were reacted with alkyl ketene dimer(AKD) under heterogeneous conditions at 70℃ for 12 h.The AKD molecules reacted with starch hydroxyl groups to form β-keto ester...Oxidized starch powder and cationic starch solution were reacted with alkyl ketene dimer(AKD) under heterogeneous conditions at 70℃ for 12 h.The AKD molecules reacted with starch hydroxyl groups to form β-keto ester linkages under the above conditions.The reaction products were separated into CHCl_3-soluble and CHCl_3-insoluble fractions.FT-IR spectroscopy,SEM,Xray diffraction,and TG-DTA analyses of the CHCl_3-insoluble fraction indicated that β-keto ester substituents were introduced to hydroxyl groups on the starch surfaces.The results indicated that hydrogen bonds between the starch molecules were disrupted under heterogeneous conditions upon heating.The activity and accessibility of hydroxyl groups were enhanced,as a result of which β-keto ester bonds were produced between AKD and starch.Based on these results,we speculate that the β-keto esters which existed in the sheets sized by AKD emulsions were generated by the reaction between AKD and starch.展开更多
Soot particles,composed of elemental carbon and organic compounds,have attracted widespread attention in recent years due to their significant impacts on climate,the environment and human health.Soot has been found to...Soot particles,composed of elemental carbon and organic compounds,have attracted widespread attention in recent years due to their significant impacts on climate,the environment and human health.Soot has been found to be chemically and physically active in atmospheric aging processes,which leads to alterations in its composition,morphology,hygroscopicity and optical properties and thus changes its environmental and health effects.The heterogeneous reactions on soot also have a significant impact on the transformation of gaseous pollutants into secondary aerosols.Therefore,the interactions between soot and atmospheric substances have been widely investigated to better understand the environmental behaviors of soot.In this review,we systematically summarize the progress and developments in the heterogeneous chemistry on soot over the past_(3)0 years.Atmospheric trace constituents such as NO_(2),O_(3),SO_(2),N_(2)O_(5),HNO_(3),H_(2)SO_(4),OH radical,HO_(2)radical,peroxyacetyl nitrate etc.,are presented in detail from the aspect of their heterogeneous reactions on soot.The possible mechanisms and the effects of environmental conditions on these heterogeneous reactions are also addressed.Further,the impacts of the heterogeneous reactions of soot on the atmospheric environment are discussed,and some aspects of soot-related research which require further investigation are proposed as well.展开更多
Chemical warfare agents(CWA)are stockpiled in large quantities across the globe.Agents stored in inaccessible facilities need to be destroyed rapidly without dispersing the compounds to surrounding areas.Metal-based e...Chemical warfare agents(CWA)are stockpiled in large quantities across the globe.Agents stored in inaccessible facilities need to be destroyed rapidly without dispersing the compounds to surrounding areas.Metal-based energetic formulations are used in such prompt defeat applications to rapidly decompose the CWA by generating a high temperature environment.An alternate,and possibly a more effective decomposition pathway could be provided by chemicidal action of aerosolized condensed combustion products,which typically consist of metal oxides.Toxic fumes that escape the high temperature blast zone can be neutralized by smoke generated during combustion,depending on the particle size,surface characteristics,chemical properties,and concentration of this smoke.This review considers relevant experimental and modeling studies quantifying decomposition of CWA comprising organophosphorus compounds and their surrogates on the surface of various metal oxides.Dimethyl methylphosphonate(DMMP),a sarine surrogate,was used most commonly for such experiments.Many reported efforts focused on the mechanisms of adsorption of DMMP to various metal oxides and initial reaction steps cleaving various bonds from the chemisorbed molecules.For selected oxides,these experiments were supported by quantum-mechanical calculations.In other studies,the capacity of oxide surfaces to adsorb and decompose DMMP was quantified.In most cases,porous catalysts were used although limited experimental data are available for aerosolized nonporous oxide particles.The reported experimental data applicable to scenarios involving prompt decomposition of CWA are summarized.It is noted that information is lacking describing respective heterogeneous reaction kinetics.Preliminary estimates of aerosolized smoke particle concentrations required to destroy CWA are made considering gas phase diffusion rates and reported values of the oxide capacity to decompose CWA or their surrogates.展开更多
The paper presents shortly some of the important elements of the theory and of the practical applications of the kinetics of heterogeneous catalytic reactions. Discussed are some of the most important concepts of the ...The paper presents shortly some of the important elements of the theory and of the practical applications of the kinetics of heterogeneous catalytic reactions. Discussed are some of the most important concepts of the kinetics of complex heterogeneous catalytic reactions,methodology of building kinetic models and mathematical treatment of experimental data,influence of heat and mass transfer,types of laboratory reactors,kinetics and nanosized catalysts and others. Examples for use of the kinetic studies for the development and application of industrial catalysts and modeling of industrial reactors are presented.展开更多
In this study,a series of Co_3O_4/ mildly oxidized graphite oxide(mGO) nanocatalysts(Co_3O_4/ mGO-l,Co_3O_4/ mGO-2 and Co_3O_4/mGO-3) were synthesized through solvothermal method and used as a mediator for the heterog...In this study,a series of Co_3O_4/ mildly oxidized graphite oxide(mGO) nanocatalysts(Co_3O_4/ mGO-l,Co_3O_4/ mGO-2 and Co_3O_4/mGO-3) were synthesized through solvothermal method and used as a mediator for the heterogeneous peroxymonosulfate(PMS)activation.The performance of CO_3O_4 / mGO/PMS system was investigated using acid orange 7(AO7).Results showed that Co_3O_4/mGO-3 had the best degradation efficiency of AO7 and the removal rate was above 90%in about 6 min.The phenomenon indicated the catalytic activity of Co_3O_4/mGO composites was related to the oxidation degree of graphite oxide(GO).In addition,experiments showed the content of Co_3O_4 had an effect on the catalytic activity.The composites were characterized with X-ray powder diffraction(XRD),FTIR,Raman,X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM).According to the charactrization and synergistic catalytic mechanism,the generation of Co—OH complexes found to be the initial step to activate PMS in the heterogeneous system of Co_3O_4/mGO hybrid.展开更多
Heterogeneous reaction of NO_(2) with mineral dust aerosol may play important roles in troposphere chemistry,and has been investigated by a number of laboratory studies.However,the influence of mineralogy on this reac...Heterogeneous reaction of NO_(2) with mineral dust aerosol may play important roles in troposphere chemistry,and has been investigated by a number of laboratory studies.However,the influence of mineralogy on this reaction has not been well understood,and its impact on aerosol hygroscopicity is not yet clear.This work investigated heterogeneous reactions of NO_(2)(∼10 ppmv)with K-feldspar,illite,kaolinite,montmorillonite and Arizona Test Dust(ATD)at room temperature as a function of relative humidity(<1%to 80%)and reaction time(up to 24 hr).Heterogeneous reactivity towards NO_(2) was low for illite,kaolinite,montmorillonite and ATD,and uptake coefficients of NO_(2),γ(NO_(2)),were determined to be around or smaller than 1×10^(−8);K-feldspar exhibited higher reactivity towards NO_(2),and CaCO_(3) is most reactive among the nine mineral dust samples considered in this and previous work.After heterogeneous reaction with NO_(2) for 24 hr,increase in hygroscopicity was nearly insignificant for illite,kaolinite and montmorillonite,and small but significant for K-feldspar;in addition,large increase in hygroscopicity was observed for ATD,although the increase in hygroscopicity was still smaller than CaCO_(3).展开更多
Mineral dust is an important type of ice nucleating particles in the troposphere;however,the effects of heterogeneous reactions on ice nucleation(IN)activities of mineral dust remain to be elucidated.A droplet-freezin...Mineral dust is an important type of ice nucleating particles in the troposphere;however,the effects of heterogeneous reactions on ice nucleation(IN)activities of mineral dust remain to be elucidated.A droplet-freezing apparatus(Guangzhou Institute of Geochemistry Ice Nucleation Apparatus,GIGINA)was developed in thiswork to measure IN activities of atmospheric particles in the immersion freezingmode,and its performancewas validated by a series of experimental characterizations.This apparatus was then employed to measure IN activities of feldspar and Arizona Test Dust(ATD)particles before and after heterogeneous reaction with NO_(2)(10±0.5 ppmv)at 40%relative humidity.The surface coverage of nitrate,θ(NO_(3)^(−)),increased to 3.1±0.2 for feldspar after reaction with NO_(2) for 6 hr,and meanwhile the active site density per unit surface area(ns)at-20℃ was reduced from 92±5 to<1.0 cm^(−2) by about two orders of magnitude;however,no changes in nitrate content or IN activities were observed for further increase in reaction time(up to 24 hr).Both nitrate content and IN activities changed continuously with reaction time(up to 24 hr)for ATD particles;after reaction with NO_(2) for 24 hr,θ(NO_(3)^(−))increased to 1.4±0.1 and ns at-20℃ was reduced from 20±4 to 9.7±1.9 cm^(−2) by a factor of∼2.Our work suggests that heterogeneous reaction with NO_(2),an abundant reactive nitrogen species in the troposphere,may significantly reduce IN activities of mineral dust in the immersion freezing mode.展开更多
Iron oxychloride(FeOCl)is a unique layered material with tunable electronic properties.The conventional synthetic route of chemical vapor transition involves a thermodynamics-driven gas-solid interfacial reaction whic...Iron oxychloride(FeOCl)is a unique layered material with tunable electronic properties.The conventional synthetic route of chemical vapor transition involves a thermodynamics-driven gas-solid interfacial reaction which often generates macroscopic crystals with stable facets.In this study,through analyzing the effects of the synthetic parameters on the FeOCl synthesis,we discovered the dominant contribution of theα-Fe_(2)O_(3)precursors on the chemical property of the FeOCl product,and subsequently developed a highly-controllable synthetic route of tailoring the FeOCl structures into small sizes and exposed high-energy facets via a facile and scalable mechanical-chemical approach.The synthesized products could be systematically tuned by the ball-milling conditions of theα-Fe_(2)O_(3)precursors.With increased milling time,the FeOCl crystallites demonstrated reduced sizes and more exposed(110)facets.Intriguingly,these smallsized FeOCl catalysts exhibited much faster Fenton-like kinetics than the pristine macroscopic FeOCl materials.Specifically,FeOCl catalysts with a 12-hour milling time showed nearly 39 times higher efficiency toward phenol degradation than the pristine FeOCl.The structure-reactivity relationship was further elucidated using the combinatory analysis via density functional theory calculation,electron paramagnetic resonance and radical quenching probe experiments.This work provides a rationale for tailoring the surface structures of FeOCl crystallites for potential applications in environmental catalysis.展开更多
Despite the heterogeneous reaction of sulfur dioxide(SO_(2))on mineral dust particles significantly affects the atmospheric environment,the effect of acidic gases on the formation of sulfite and sulfate from this reac...Despite the heterogeneous reaction of sulfur dioxide(SO_(2))on mineral dust particles significantly affects the atmospheric environment,the effect of acidic gases on the formation of sulfite and sulfate from this reaction is not particularly clear.In this work,using the in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)technique,we employed a mineral dust particle model(CaCO_(3))combined with NO_(2)and acetic acid to investigate their effects on the heterogeneous reaction of SO_(2)on CaCO_(3)particles.Itwas found that water vapor can promote the formation of sulfite and simulated radiation can facilitate the oxidation of sulfite to sulfate.The addition of NO_(2)or acetic acid to the reaction system altered the production of sulfate and sulfite accordingly.There was a synergistic effect between NO_(2)and SO_(2)that promoted the oxidation of sulfite to sulfate,and a competitive effect between acetic acid and SO_(2)that inhibited the formation of sulfite.Moreover,light and water vapor can also affect the heterogeneous reaction of SO_(2)with the coexistence ofmultiple gases.These findings improve our understanding of the effects of organic and inorganic gases and environmental factors on the formation of sulfite and sulfate in heterogeneous reactions.展开更多
The present study reveals the effect of homogeneous/hetereogeneous reaction on stagnation point flow of Williamson fluid in the presence of magnetohydrodynamics and heat generation/absorption coefficient over a stretc...The present study reveals the effect of homogeneous/hetereogeneous reaction on stagnation point flow of Williamson fluid in the presence of magnetohydrodynamics and heat generation/absorption coefficient over a stretching cylinder. Further the effects of variable thermal conductivity and thermal stratification are also considered. The governing partial differential equations are converted to ordinary differential equations with the help of similarity transformation.The system of coupled non-linear ordinary differential equations is then solved by shooting technique. MATLAB shooting code is validated by comparison with the previously published work in limiting case. Results are further strengthened when the present results are compared with MATLAB built-in function bvp4c. Effects of prominent parameters are deliberated graphically for the velocity, temperature and concentration profiles. Skin-friction coefficient and Nusselt number for the different parameters are investigated with the help of tables.展开更多
The heterogeneous reaction of SO_(2) on mineral dust surfaces is generally considered as an important chemical pathway for secondary sulfate formation in the troposphere.To this day,there are no reported studies that ...The heterogeneous reaction of SO_(2) on mineral dust surfaces is generally considered as an important chemical pathway for secondary sulfate formation in the troposphere.To this day,there are no reported studies that assess the impact of atmospheric CO_(2) in sulfate production on mineral dust surfaces.In this work,we investigate the impact of CO_(2) on SO_(2) uptake on dust proxy aluminum oxide particles using a diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).CO_(2) is demonstrated to suppress the heterogeneous oxidation of SO_(2) on alpha-Al2 O_(3).Compared to that measured in the CO_(2)-free case,the uptake coefficient is decreased by nearly 57%when Al_(2)O_(3) particles are exposed to the gas flow with atmospheric CO_(2) at a relative humidity(RH)of 25%.It is also found that there is a balance between the yield of active moiety-OH provided by AI(OH)3(CO)(OH)2 clusters and the loss of basic hydroxyl group on aluminum oxide surfaces blocked by CO_(2)-derived(bi)carbonate species.This work,for the first time,reveals a negative effect of atmospheric CO_(2) on the sulfate formation,which potentially decreases solarradiation scattering and further exacerbates global warming.展开更多
Fe-impregnated biochar(Fe-BC)as high-efficiency heterogeneous Fenton catalyst was synthesized and evaluated in detail for its catalytic activity,stability and reusability under various conditions.The optimal condition...Fe-impregnated biochar(Fe-BC)as high-efficiency heterogeneous Fenton catalyst was synthesized and evaluated in detail for its catalytic activity,stability and reusability under various conditions.The optimal conditions for the Fenton oxidation of methylene blue(MB)as model dye were determined as 0.075 g/L H_(2)O_(2),0.5 g/L Fe-BC for 0.1 g/L MB,which resulted in optimum Dye:Fe_(cat):H_(2)O_(2) ratio of 1:5:0.75(on g/L basis)or[Dye]:[Fe_(total)]:[H_(2)O_(2)]molar ratio of 1:6.2:7.0 respectively.The effective degradation of MB was identified over a wider pH range,and even after four consecutive runs Fe-BC maintained above 95%MB removal rate within 3 min of treatment with low Fe release,indicating strong stability and reusability.Under the optimum Dye:Fe_(cat):H_(2)O_(2)(g/L)condition at initial pH 4,the Fe-BC achieved 99.9%removal efficiency of MB within 3 min in heterogeneous Fenton reaction(HEFR)with much less H_(2)O_(2) concentration and low catalyst dosage,demonstrat-ing its efficiency and cost-effectiveness compared to other Fenton reaction catalysts.The removal velocity of MB showed two rate steps:a fast first stage followed by a slow stage with the rate in the order of H_(2)O_(2)/Fe-BC⋙H_(2)O_(2)/biochar>biochar>H_(2)O_(2).Overall,the developed Fe-BC is more economical with strong stability and recyclability for use in HEFR for treating recalcitrant pollutants.展开更多
Atmospheric oxidizing capacity(AOC)is the fundamental driving factors of chemistry process(e.g.,the formation of ozone(O_(3))and secondary organic aerosols(SOA))in the troposphere.However,accurate quantification of AO...Atmospheric oxidizing capacity(AOC)is the fundamental driving factors of chemistry process(e.g.,the formation of ozone(O_(3))and secondary organic aerosols(SOA))in the troposphere.However,accurate quantification of AOC still remains uncertainty.In this study,a comprehensive field campaign was conducted during autumn 2019 in downtown of Beijing,where O_(3) and PM_(2.5) episodes had been experienced successively.The observation-based model(OBM)is used to quantify the AOC at O_(3) and PM_(2.5) episodes.The strong intensity of AOC is found at O_(3) and PM2.5 episodes,and hydroxyl radical(OH)is the dominating daytime oxidant for both episodes.The photolysis of O_(3) is main source of OH at O_(3) episode;the photolysis of nitrous acid(HONO)and formaldehyde(HCHO)plays important role in OH formation at PM_(2.5) episode.The radicals loss routines vary according to precursor pollutants,resulting in different types of air pollution.O_(3) budgets and sensitivity analysis indicates that O_(3) production is transition regime(both VOC and NOx-limited)at O3 episode.The heterogeneous reaction of hydroperoxy radicals(HO_(2))on aerosol surfaces has significant influence on OH and O_(3) production rates.The HO_(2) uptake coefficient(γHO_(2))is the determining factor and required accurate measurement in real atmospheric environment.Our findings could provide the important bases for coordinated control of PM_(2.5) and O_(3) pollution.展开更多
Ammonium is an important atmospheric particulate component that dictates many environmental processes.The promotion of the heterogeneous conversion of NH_(3) to NH_(4)^(+) by SO_(2) on different mineral dust surfaces ...Ammonium is an important atmospheric particulate component that dictates many environmental processes.The promotion of the heterogeneous conversion of NH_(3) to NH_(4)^(+) by SO_(2) on different mineral dust surfaces displays remarkable discrepancies,especially on MgO and α-Fe2O3 surfaces,however,the underlying mechanisms are not well known.Here,using periodic density functional theory(DFT)calculation and Born-Oppenheimer molecular dynamics(BOMD)simulation,we explored the hetero-geneous adsorption of NH_(3) on MgO(110)and α--Fe2O3(001)surfaces in the presence and absence of SO_(2).The results show that on MgO(110)surface,hydrogen-bonding interactions of NH_(3) on both adsorbed hydroxyl or bisulfite/bisulfate sites are observed no matter whether SO_(2) is present or not.While,on theα-Fe2O3(001)surface,significant conversion of NH_(3) to NH_(4)^(+)occurs with the coexistence of SO_(2),which is due to the hydrogen transfer reaction from surface HSO4 to N in NH_(3).The fundamental reason may be that the stronger electron affinity of Fe3+than Mg2+results in adsorbed bisulfate and/or bisulfite with greater acidity on α-Fe2O3 surface than MgO surface.Our results give a molecular-level explanation for the heterogeneous conversion of NH_(3) to NH_(4)^(+)on different mineral dust surfaces under complex air pollution conditions.Considering the fact that ammonium is abundant in secondary particulates,this work would help in understanding the rapid conversion of ammonia to ammonium and in developing classification governance policies for the key precursor pollutants in China.展开更多
This study aims to investigate the time-dependent squeezing of nanofluid flow, comprising carbon nanotubes of dual nature, e.g. single-walled carbon nanotubes, and multi-walled carbon nanotubes,between two parallel di...This study aims to investigate the time-dependent squeezing of nanofluid flow, comprising carbon nanotubes of dual nature, e.g. single-walled carbon nanotubes, and multi-walled carbon nanotubes,between two parallel disks. Numerical simulations of the proposed novel model are conducted,accompanied by Cattaneo-Christov heat flux in a Darcy-Forchheimer permeable media. Additional impacts of homogeneous–heterogeneous reactions are also noted, including melting heat. A relevant transformation procedure is implemented for the transition of partial differential equations to the ordinary variety. A computer software-based MATLAB function, bvp4c, is implemented to handle the envisioned mathematical model. Sketches portraying impacts on radial velocity, temperature, and concentration of the included parameters are given, and deliberated upon. Skin friction coefficient and local Nusselt number are evaluated via graphical illustrations. It is observed that the local inertia coefficient has an opposite impact on radial velocity and temperature field. It is further perceived that melting and radiation parameters demonstrate a retarding effect on temperature profile.展开更多
Three imidazole-modified Ag-polyoxovanadates frameworks(APFs)with a controllable molar ratio of Ag+to polyoxovanadates(POVs)[Ag(IM)_(2)]_(2)V_(4)O_(12)·2Ag(IM)_(2)(APF-1),[Ag_(2)(1-eIM)_(4)]_(2)[Ag(1-eIM)_(2)]_(3...Three imidazole-modified Ag-polyoxovanadates frameworks(APFs)with a controllable molar ratio of Ag+to polyoxovanadates(POVs)[Ag(IM)_(2)]_(2)V_(4)O_(12)·2Ag(IM)_(2)(APF-1),[Ag_(2)(1-eIM)_(4)]_(2)[Ag(1-eIM)_(2)]_(3)·2Ag(1-eIM)_(2)·3(1-HeIM)[V_(10)O_(28)]_(2)(APF-2)and[Ag(1-pIM)_(2)]_(3)[HV_(10)O_(28)]·2Ag(1-pIM)_(2)·2H_(2)O(APF-3)(IM=imida-zole;1-eIM=1-ethylimidazole and 1-pIM=1-propylimidazole)have been successfully achieved by self-assembly of POVs,Ag+cations,and three different imidazole derivatives.Interestingly,the molar ratios of Ag+to POVs vary from 4:1,4.5:1 to 5:1 by changing the vanadium resources and imidazole deriva-tives.Notably,the coordination environment of Ag+cations and the structure of POVs in the APFs are also different.Specifically,for APF-1,the four Ag atoms adopt three-coordinated and four-coordinated geometries,respectively,and Ag-imidazole complexes and[V_(4)O 1_(2)]_(4)−cluster form the one-dimensional polymeric chains.While Ag atoms in APF-2 and APF-3 exhibit two-,four-and five-coordinated geome-tries for APF-2,four-,five-and six-coordinated geometries for APF-3,respectively.These Ag+cations and decavanadate clusters are assembled into the 2D supramolecular structure through the Ag-O bonds and Ag…Ag argentophilic interaction.Remarkably,thus-obtained APF-2 can serve as powerful efficient hetero-geneous catalyst for construction of C–N bond and detoxification of simulant sulfur mustard(yields up to 99%),which enable successful recycling for three cycles with remained catalytic activities and structure stability.展开更多
Laboratory studies of HO2 uptake coefficients,γ(HO2),were conducted at room temperature using an aerosol flow tube coupled with a laser induced fluorescence(LIF) system.The measurement was conducted with atmospherica...Laboratory studies of HO2 uptake coefficients,γ(HO2),were conducted at room temperature using an aerosol flow tube coupled with a laser induced fluorescence(LIF) system.The measurement was conducted with atmospherically relevant HO2 concentrations(~1×10^9 molecule/cm^3) at 51% RH.The measured γ(HO2) onto aqueous(NH4)2 SO4 aerosol was 0.001±0.0007,which was consistent with the relatively low first-order loss rate of HO2 onto aqueous(NH4)2 SO4 aerosol.Theγ(HO2) was elevated with increase of Cu(Ⅱ) concentrations in aqueous(NH4)2 SO4 aerosol.The threshold of Cu(Ⅱ) concentration was10^-3 mol/L for the dramatic increase of γ(HO2).It was found that γ(HO2) reached 0.1 when Cu(Ⅱ)concentration in aerosol was larger than 10^-3 mol/L,suggesting that γ(HO2) is very sensitive to concentration of transition metal ions in aerosol.展开更多
The UCD/CIT model was modified to include a process analysis(PA)scheme for gas and particulate matter(PM)to study the formation of secondary nitrate aerosol during a stagnant wintertime air pollution episode during th...The UCD/CIT model was modified to include a process analysis(PA)scheme for gas and particulate matter(PM)to study the formation of secondary nitrate aerosol during a stagnant wintertime air pollution episode during the California Regional PM_(2.5)/PM_(10) Air Quality Study(CRPAQS)where detailed measurements of PM components are available at a few sites.Secondary nitrate is formed in the urban areas from near the ground to a few hundred meters above the surface during the day with a maximum modeled net increase rate of 4μg·m^(-3)·d^(-1) during the study episode.The secondary nitrate formation rate in rural areas is lower due to lower NO_(2).In the afternoon hours,near-surface temperature can be high enough to evaporate the particulate nitrate.In the nighttime hours,both the gas phase N_(2)O_(5) reactions with water vapor and the N_(2)O_(5) heterogeneous reactions with particle-bound water are important for secondary nitrate formation.The N_(2)O_(5) reactions are most import near the surface to a few hundred meters above surface with a maximum modeled net secondary nitrate increase rate of 1μg·m^(-3)·d^(-1) and are more significant in the rural areas where the O3 concentrations are high at night.In general,vertical transport during the day moves the nitrate formed near the surface to higher elevations.During the stagnant days,process analysis indicates that the nitrate concentration in the upper air builds up and leads to a net downward flux of nitrate through vertical diffusion and a rapid increase of surface nitrate concentration.展开更多
基金the National Natural Science Foundation of China(Nos.11872241 and11432009)。
文摘The homogeneous and heterogeneous reactions in the boundary-layer of a flat surface are considered. The autocatalysts are assumed to be of regular sizes, while the solution is a dilute nanofluid. The heat release due to the chemical reactions is taken into account. The Buongiorno’s model is used to describe the behaviors of this reaction system. This configuration makes the current model be different from all previous publications. Multiple solutions are given numerically to the rescaled nonlinear system, whose stability is verified. The results show that the strength coefficients of the homogeneous and heterogeneous reactions are key factors to cause the appearance of the multiple solutions in the distribution of the chemical reactions. Nanofluids enhance the diffusion of heat and help maintain the stability of chemical reactions.
基金financial support from Shandong Province Education Department(Grant No.J14 LC11)National Natural Science Foundation of China(Grant No.21406126 and 21576146)+2 种基金Department of Science and Technology of Shandong Province(Grant No.2014 GSF116001)973(Grant No.2014 CB460610)Department of Science and Technology of Shandong Province(Grant No.2015 ZDXX0403 B03)
文摘Oxidized starch powder and cationic starch solution were reacted with alkyl ketene dimer(AKD) under heterogeneous conditions at 70℃ for 12 h.The AKD molecules reacted with starch hydroxyl groups to form β-keto ester linkages under the above conditions.The reaction products were separated into CHCl_3-soluble and CHCl_3-insoluble fractions.FT-IR spectroscopy,SEM,Xray diffraction,and TG-DTA analyses of the CHCl_3-insoluble fraction indicated that β-keto ester substituents were introduced to hydroxyl groups on the starch surfaces.The results indicated that hydrogen bonds between the starch molecules were disrupted under heterogeneous conditions upon heating.The activity and accessibility of hydroxyl groups were enhanced,as a result of which β-keto ester bonds were produced between AKD and starch.Based on these results,we speculate that the β-keto esters which existed in the sheets sized by AKD emulsions were generated by the reaction between AKD and starch.
基金This work was financially supported by the National Natural Science Foundation of China(22122610,22188102,41877304,21777171).
文摘Soot particles,composed of elemental carbon and organic compounds,have attracted widespread attention in recent years due to their significant impacts on climate,the environment and human health.Soot has been found to be chemically and physically active in atmospheric aging processes,which leads to alterations in its composition,morphology,hygroscopicity and optical properties and thus changes its environmental and health effects.The heterogeneous reactions on soot also have a significant impact on the transformation of gaseous pollutants into secondary aerosols.Therefore,the interactions between soot and atmospheric substances have been widely investigated to better understand the environmental behaviors of soot.In this review,we systematically summarize the progress and developments in the heterogeneous chemistry on soot over the past_(3)0 years.Atmospheric trace constituents such as NO_(2),O_(3),SO_(2),N_(2)O_(5),HNO_(3),H_(2)SO_(4),OH radical,HO_(2)radical,peroxyacetyl nitrate etc.,are presented in detail from the aspect of their heterogeneous reactions on soot.The possible mechanisms and the effects of environmental conditions on these heterogeneous reactions are also addressed.Further,the impacts of the heterogeneous reactions of soot on the atmospheric environment are discussed,and some aspects of soot-related research which require further investigation are proposed as well.
基金This work was supported by the US Defense Threat Reduction Agency,DTRAGrant HDTRA1-19-1-0023.
文摘Chemical warfare agents(CWA)are stockpiled in large quantities across the globe.Agents stored in inaccessible facilities need to be destroyed rapidly without dispersing the compounds to surrounding areas.Metal-based energetic formulations are used in such prompt defeat applications to rapidly decompose the CWA by generating a high temperature environment.An alternate,and possibly a more effective decomposition pathway could be provided by chemicidal action of aerosolized condensed combustion products,which typically consist of metal oxides.Toxic fumes that escape the high temperature blast zone can be neutralized by smoke generated during combustion,depending on the particle size,surface characteristics,chemical properties,and concentration of this smoke.This review considers relevant experimental and modeling studies quantifying decomposition of CWA comprising organophosphorus compounds and their surrogates on the surface of various metal oxides.Dimethyl methylphosphonate(DMMP),a sarine surrogate,was used most commonly for such experiments.Many reported efforts focused on the mechanisms of adsorption of DMMP to various metal oxides and initial reaction steps cleaving various bonds from the chemisorbed molecules.For selected oxides,these experiments were supported by quantum-mechanical calculations.In other studies,the capacity of oxide surfaces to adsorb and decompose DMMP was quantified.In most cases,porous catalysts were used although limited experimental data are available for aerosolized nonporous oxide particles.The reported experimental data applicable to scenarios involving prompt decomposition of CWA are summarized.It is noted that information is lacking describing respective heterogeneous reaction kinetics.Preliminary estimates of aerosolized smoke particle concentrations required to destroy CWA are made considering gas phase diffusion rates and reported values of the oxide capacity to decompose CWA or their surrogates.
基金supported by the SABIC Chair in Catalysis,King Abdulaziz University
文摘The paper presents shortly some of the important elements of the theory and of the practical applications of the kinetics of heterogeneous catalytic reactions. Discussed are some of the most important concepts of the kinetics of complex heterogeneous catalytic reactions,methodology of building kinetic models and mathematical treatment of experimental data,influence of heat and mass transfer,types of laboratory reactors,kinetics and nanosized catalysts and others. Examples for use of the kinetic studies for the development and application of industrial catalysts and modeling of industrial reactors are presented.
基金Innovation Program of Shanghai Municipal Education Commission,China(No.12ZZ069)Research Fund for the Doctoral Program of Higher Education,China(No.20130075110006)
文摘In this study,a series of Co_3O_4/ mildly oxidized graphite oxide(mGO) nanocatalysts(Co_3O_4/ mGO-l,Co_3O_4/ mGO-2 and Co_3O_4/mGO-3) were synthesized through solvothermal method and used as a mediator for the heterogeneous peroxymonosulfate(PMS)activation.The performance of CO_3O_4 / mGO/PMS system was investigated using acid orange 7(AO7).Results showed that Co_3O_4/mGO-3 had the best degradation efficiency of AO7 and the removal rate was above 90%in about 6 min.The phenomenon indicated the catalytic activity of Co_3O_4/mGO composites was related to the oxidation degree of graphite oxide(GO).In addition,experiments showed the content of Co_3O_4 had an effect on the catalytic activity.The composites were characterized with X-ray powder diffraction(XRD),FTIR,Raman,X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM).According to the charactrization and synergistic catalytic mechanism,the generation of Co—OH complexes found to be the initial step to activate PMS in the heterogeneous system of Co_3O_4/mGO hybrid.
基金supported by the National Natural Science Foundation of China(No.42022050)Guangdong Foundation for Program of Science and Technology Research(Nos.2019B121205006 and 2020B1212060053)+1 种基金the Guangdong Science and Technology Department(No.2017GC010501)CAS Pioneer Hundred Talents program.
文摘Heterogeneous reaction of NO_(2) with mineral dust aerosol may play important roles in troposphere chemistry,and has been investigated by a number of laboratory studies.However,the influence of mineralogy on this reaction has not been well understood,and its impact on aerosol hygroscopicity is not yet clear.This work investigated heterogeneous reactions of NO_(2)(∼10 ppmv)with K-feldspar,illite,kaolinite,montmorillonite and Arizona Test Dust(ATD)at room temperature as a function of relative humidity(<1%to 80%)and reaction time(up to 24 hr).Heterogeneous reactivity towards NO_(2) was low for illite,kaolinite,montmorillonite and ATD,and uptake coefficients of NO_(2),γ(NO_(2)),were determined to be around or smaller than 1×10^(−8);K-feldspar exhibited higher reactivity towards NO_(2),and CaCO_(3) is most reactive among the nine mineral dust samples considered in this and previous work.After heterogeneous reaction with NO_(2) for 24 hr,increase in hygroscopicity was nearly insignificant for illite,kaolinite and montmorillonite,and small but significant for K-feldspar;in addition,large increase in hygroscopicity was observed for ATD,although the increase in hygroscopicity was still smaller than CaCO_(3).
基金supported by the National Natural Science Foundation of China(No.42022050)the Guangdong Basic and Applied Basic Research Fund Committee(No.2020B1515130003)+3 种基金the Guangdong Foundation for Program of Science and Technology Research(Nos.2019B121205006 and 2020B1212060053)the Guangdong Science and Technology Department(No.2017GC010501)the CAS Pioneer Hundred Talents program.We would like to thank Ryan Sullivan(Carnegie Mellon University,USA)the Nadine Borduas-Dedekind(University of British Columbia,Canada)for sharing their original data.
文摘Mineral dust is an important type of ice nucleating particles in the troposphere;however,the effects of heterogeneous reactions on ice nucleation(IN)activities of mineral dust remain to be elucidated.A droplet-freezing apparatus(Guangzhou Institute of Geochemistry Ice Nucleation Apparatus,GIGINA)was developed in thiswork to measure IN activities of atmospheric particles in the immersion freezingmode,and its performancewas validated by a series of experimental characterizations.This apparatus was then employed to measure IN activities of feldspar and Arizona Test Dust(ATD)particles before and after heterogeneous reaction with NO_(2)(10±0.5 ppmv)at 40%relative humidity.The surface coverage of nitrate,θ(NO_(3)^(−)),increased to 3.1±0.2 for feldspar after reaction with NO_(2) for 6 hr,and meanwhile the active site density per unit surface area(ns)at-20℃ was reduced from 92±5 to<1.0 cm^(−2) by about two orders of magnitude;however,no changes in nitrate content or IN activities were observed for further increase in reaction time(up to 24 hr).Both nitrate content and IN activities changed continuously with reaction time(up to 24 hr)for ATD particles;after reaction with NO_(2) for 24 hr,θ(NO_(3)^(−))increased to 1.4±0.1 and ns at-20℃ was reduced from 20±4 to 9.7±1.9 cm^(−2) by a factor of∼2.Our work suggests that heterogeneous reaction with NO_(2),an abundant reactive nitrogen species in the troposphere,may significantly reduce IN activities of mineral dust in the immersion freezing mode.
基金This work was partially supported by the National Key Projects for Fundamental Research and Development of China(Grant No.2019YFC1906700)the National Natural Science Foundation for Outstanding Young Scholars(Grant No.22222602)the National Natural Science Foundation of China(Grant No.21876049).
文摘Iron oxychloride(FeOCl)is a unique layered material with tunable electronic properties.The conventional synthetic route of chemical vapor transition involves a thermodynamics-driven gas-solid interfacial reaction which often generates macroscopic crystals with stable facets.In this study,through analyzing the effects of the synthetic parameters on the FeOCl synthesis,we discovered the dominant contribution of theα-Fe_(2)O_(3)precursors on the chemical property of the FeOCl product,and subsequently developed a highly-controllable synthetic route of tailoring the FeOCl structures into small sizes and exposed high-energy facets via a facile and scalable mechanical-chemical approach.The synthesized products could be systematically tuned by the ball-milling conditions of theα-Fe_(2)O_(3)precursors.With increased milling time,the FeOCl crystallites demonstrated reduced sizes and more exposed(110)facets.Intriguingly,these smallsized FeOCl catalysts exhibited much faster Fenton-like kinetics than the pristine macroscopic FeOCl materials.Specifically,FeOCl catalysts with a 12-hour milling time showed nearly 39 times higher efficiency toward phenol degradation than the pristine FeOCl.The structure-reactivity relationship was further elucidated using the combinatory analysis via density functional theory calculation,electron paramagnetic resonance and radical quenching probe experiments.This work provides a rationale for tailoring the surface structures of FeOCl crystallites for potential applications in environmental catalysis.
基金supported by the National Natural Science Foundation of China(No.91644214)Youth Innovation Program of Universities in Shandong Province(No.2019KJD007)Fundamental Research Fund of Shandong University(No.2020QNQT012)
文摘Despite the heterogeneous reaction of sulfur dioxide(SO_(2))on mineral dust particles significantly affects the atmospheric environment,the effect of acidic gases on the formation of sulfite and sulfate from this reaction is not particularly clear.In this work,using the in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)technique,we employed a mineral dust particle model(CaCO_(3))combined with NO_(2)and acetic acid to investigate their effects on the heterogeneous reaction of SO_(2)on CaCO_(3)particles.Itwas found that water vapor can promote the formation of sulfite and simulated radiation can facilitate the oxidation of sulfite to sulfate.The addition of NO_(2)or acetic acid to the reaction system altered the production of sulfate and sulfite accordingly.There was a synergistic effect between NO_(2)and SO_(2)that promoted the oxidation of sulfite to sulfate,and a competitive effect between acetic acid and SO_(2)that inhibited the formation of sulfite.Moreover,light and water vapor can also affect the heterogeneous reaction of SO_(2)with the coexistence ofmultiple gases.These findings improve our understanding of the effects of organic and inorganic gases and environmental factors on the formation of sulfite and sulfate in heterogeneous reactions.
文摘The present study reveals the effect of homogeneous/hetereogeneous reaction on stagnation point flow of Williamson fluid in the presence of magnetohydrodynamics and heat generation/absorption coefficient over a stretching cylinder. Further the effects of variable thermal conductivity and thermal stratification are also considered. The governing partial differential equations are converted to ordinary differential equations with the help of similarity transformation.The system of coupled non-linear ordinary differential equations is then solved by shooting technique. MATLAB shooting code is validated by comparison with the previously published work in limiting case. Results are further strengthened when the present results are compared with MATLAB built-in function bvp4c. Effects of prominent parameters are deliberated graphically for the velocity, temperature and concentration profiles. Skin-friction coefficient and Nusselt number for the different parameters are investigated with the help of tables.
基金the National Natural Science Foundation of China(Nos.21976030 and21677037)Ministry of Science and Technology of China(Nos.2016YFE0112200 and 2016YFC0202700)the Natural Science Foundation of Shanghai(Nos.19ZR1471200 and 17ZR1440200)。
文摘The heterogeneous reaction of SO_(2) on mineral dust surfaces is generally considered as an important chemical pathway for secondary sulfate formation in the troposphere.To this day,there are no reported studies that assess the impact of atmospheric CO_(2) in sulfate production on mineral dust surfaces.In this work,we investigate the impact of CO_(2) on SO_(2) uptake on dust proxy aluminum oxide particles using a diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).CO_(2) is demonstrated to suppress the heterogeneous oxidation of SO_(2) on alpha-Al2 O_(3).Compared to that measured in the CO_(2)-free case,the uptake coefficient is decreased by nearly 57%when Al_(2)O_(3) particles are exposed to the gas flow with atmospheric CO_(2) at a relative humidity(RH)of 25%.It is also found that there is a balance between the yield of active moiety-OH provided by AI(OH)3(CO)(OH)2 clusters and the loss of basic hydroxyl group on aluminum oxide surfaces blocked by CO_(2)-derived(bi)carbonate species.This work,for the first time,reveals a negative effect of atmospheric CO_(2) on the sulfate formation,which potentially decreases solarradiation scattering and further exacerbates global warming.
基金This work was supported,in part,by the USDA National Institute of Food and Agriculture Hatch Project#1013888,Louisiana Board of Regents Support Fund#LEQSF(2019-20)-RD-D-01,a Grant from the Ministry of Science and ICT(MSIT)through the National Research Foundation(NRF)of Korea[NRF-2019R1C1C1004572NRF-2019R1A4A1029125]by Korea Institute of Planning and Evaluation for Technology in Food,Agriculture and Forestry(IPET)through Animal Disease Management Technology Development Program,funded by Ministry of Agriculture,Food and Rural Affairs(MAFRA)(319078-2)。
文摘Fe-impregnated biochar(Fe-BC)as high-efficiency heterogeneous Fenton catalyst was synthesized and evaluated in detail for its catalytic activity,stability and reusability under various conditions.The optimal conditions for the Fenton oxidation of methylene blue(MB)as model dye were determined as 0.075 g/L H_(2)O_(2),0.5 g/L Fe-BC for 0.1 g/L MB,which resulted in optimum Dye:Fe_(cat):H_(2)O_(2) ratio of 1:5:0.75(on g/L basis)or[Dye]:[Fe_(total)]:[H_(2)O_(2)]molar ratio of 1:6.2:7.0 respectively.The effective degradation of MB was identified over a wider pH range,and even after four consecutive runs Fe-BC maintained above 95%MB removal rate within 3 min of treatment with low Fe release,indicating strong stability and reusability.Under the optimum Dye:Fe_(cat):H_(2)O_(2)(g/L)condition at initial pH 4,the Fe-BC achieved 99.9%removal efficiency of MB within 3 min in heterogeneous Fenton reaction(HEFR)with much less H_(2)O_(2) concentration and low catalyst dosage,demonstrat-ing its efficiency and cost-effectiveness compared to other Fenton reaction catalysts.The removal velocity of MB showed two rate steps:a fast first stage followed by a slow stage with the rate in the order of H_(2)O_(2)/Fe-BC⋙H_(2)O_(2)/biochar>biochar>H_(2)O_(2).Overall,the developed Fe-BC is more economical with strong stability and recyclability for use in HEFR for treating recalcitrant pollutants.
基金supported by the National Key Research and Development Program of China (No. 2017YFC0210001)the National Natural Science Foundation of China (Nos. 41830106, 42022039)+1 种基金Beijing National Laboratory for Molecular Sciences (No. BNLMS-CXXM-202011)the Youth Innovation Promotion Association CAS (No. 2017042)
文摘Atmospheric oxidizing capacity(AOC)is the fundamental driving factors of chemistry process(e.g.,the formation of ozone(O_(3))and secondary organic aerosols(SOA))in the troposphere.However,accurate quantification of AOC still remains uncertainty.In this study,a comprehensive field campaign was conducted during autumn 2019 in downtown of Beijing,where O_(3) and PM_(2.5) episodes had been experienced successively.The observation-based model(OBM)is used to quantify the AOC at O_(3) and PM_(2.5) episodes.The strong intensity of AOC is found at O_(3) and PM2.5 episodes,and hydroxyl radical(OH)is the dominating daytime oxidant for both episodes.The photolysis of O_(3) is main source of OH at O_(3) episode;the photolysis of nitrous acid(HONO)and formaldehyde(HCHO)plays important role in OH formation at PM_(2.5) episode.The radicals loss routines vary according to precursor pollutants,resulting in different types of air pollution.O_(3) budgets and sensitivity analysis indicates that O_(3) production is transition regime(both VOC and NOx-limited)at O3 episode.The heterogeneous reaction of hydroperoxy radicals(HO_(2))on aerosol surfaces has significant influence on OH and O_(3) production rates.The HO_(2) uptake coefficient(γHO_(2))is the determining factor and required accurate measurement in real atmospheric environment.Our findings could provide the important bases for coordinated control of PM_(2.5) and O_(3) pollution.
基金supported by National Natural Science Foundation of China(grant Nos.22006158,22188102 and 221222610)the China Postdoctoral Science Foundation(grant Nos.2019M660818 and 2020TQ0339)Special Research Assistant Project of the Chinese Academy of Sciences.
文摘Ammonium is an important atmospheric particulate component that dictates many environmental processes.The promotion of the heterogeneous conversion of NH_(3) to NH_(4)^(+) by SO_(2) on different mineral dust surfaces displays remarkable discrepancies,especially on MgO and α-Fe2O3 surfaces,however,the underlying mechanisms are not well known.Here,using periodic density functional theory(DFT)calculation and Born-Oppenheimer molecular dynamics(BOMD)simulation,we explored the hetero-geneous adsorption of NH_(3) on MgO(110)and α--Fe2O3(001)surfaces in the presence and absence of SO_(2).The results show that on MgO(110)surface,hydrogen-bonding interactions of NH_(3) on both adsorbed hydroxyl or bisulfite/bisulfate sites are observed no matter whether SO_(2) is present or not.While,on theα-Fe2O3(001)surface,significant conversion of NH_(3) to NH_(4)^(+)occurs with the coexistence of SO_(2),which is due to the hydrogen transfer reaction from surface HSO4 to N in NH_(3).The fundamental reason may be that the stronger electron affinity of Fe3+than Mg2+results in adsorbed bisulfate and/or bisulfite with greater acidity on α-Fe2O3 surface than MgO surface.Our results give a molecular-level explanation for the heterogeneous conversion of NH_(3) to NH_(4)^(+)on different mineral dust surfaces under complex air pollution conditions.Considering the fact that ammonium is abundant in secondary particulates,this work would help in understanding the rapid conversion of ammonia to ammonium and in developing classification governance policies for the key precursor pollutants in China.
基金This work is supported by Bahria University,Islamabad,Pakistan.
文摘This study aims to investigate the time-dependent squeezing of nanofluid flow, comprising carbon nanotubes of dual nature, e.g. single-walled carbon nanotubes, and multi-walled carbon nanotubes,between two parallel disks. Numerical simulations of the proposed novel model are conducted,accompanied by Cattaneo-Christov heat flux in a Darcy-Forchheimer permeable media. Additional impacts of homogeneous–heterogeneous reactions are also noted, including melting heat. A relevant transformation procedure is implemented for the transition of partial differential equations to the ordinary variety. A computer software-based MATLAB function, bvp4c, is implemented to handle the envisioned mathematical model. Sketches portraying impacts on radial velocity, temperature, and concentration of the included parameters are given, and deliberated upon. Skin friction coefficient and local Nusselt number are evaluated via graphical illustrations. It is observed that the local inertia coefficient has an opposite impact on radial velocity and temperature field. It is further perceived that melting and radiation parameters demonstrate a retarding effect on temperature profile.
基金supported by the National Natu-ral Science Foundation of China(Nos.21871125,21871026 and 22001034)the Natural Science Foundation of Shandong Province,China(Nos.ZR2019MB043 and ZR2019QB022)the Construction Project of Quality Curriculum for Postgraduate Education of Shandong Province(No.SDYKC19057).
文摘Three imidazole-modified Ag-polyoxovanadates frameworks(APFs)with a controllable molar ratio of Ag+to polyoxovanadates(POVs)[Ag(IM)_(2)]_(2)V_(4)O_(12)·2Ag(IM)_(2)(APF-1),[Ag_(2)(1-eIM)_(4)]_(2)[Ag(1-eIM)_(2)]_(3)·2Ag(1-eIM)_(2)·3(1-HeIM)[V_(10)O_(28)]_(2)(APF-2)and[Ag(1-pIM)_(2)]_(3)[HV_(10)O_(28)]·2Ag(1-pIM)_(2)·2H_(2)O(APF-3)(IM=imida-zole;1-eIM=1-ethylimidazole and 1-pIM=1-propylimidazole)have been successfully achieved by self-assembly of POVs,Ag+cations,and three different imidazole derivatives.Interestingly,the molar ratios of Ag+to POVs vary from 4:1,4.5:1 to 5:1 by changing the vanadium resources and imidazole deriva-tives.Notably,the coordination environment of Ag+cations and the structure of POVs in the APFs are also different.Specifically,for APF-1,the four Ag atoms adopt three-coordinated and four-coordinated geometries,respectively,and Ag-imidazole complexes and[V_(4)O 1_(2)]_(4)−cluster form the one-dimensional polymeric chains.While Ag atoms in APF-2 and APF-3 exhibit two-,four-and five-coordinated geome-tries for APF-2,four-,five-and six-coordinated geometries for APF-3,respectively.These Ag+cations and decavanadate clusters are assembled into the 2D supramolecular structure through the Ag-O bonds and Ag…Ag argentophilic interaction.Remarkably,thus-obtained APF-2 can serve as powerful efficient hetero-geneous catalyst for construction of C–N bond and detoxification of simulant sulfur mustard(yields up to 99%),which enable successful recycling for three cycles with remained catalytic activities and structure stability.
基金the National Natural Science Foundation of China (Nos.91544225,21522701) for the financial support
文摘Laboratory studies of HO2 uptake coefficients,γ(HO2),were conducted at room temperature using an aerosol flow tube coupled with a laser induced fluorescence(LIF) system.The measurement was conducted with atmospherically relevant HO2 concentrations(~1×10^9 molecule/cm^3) at 51% RH.The measured γ(HO2) onto aqueous(NH4)2 SO4 aerosol was 0.001±0.0007,which was consistent with the relatively low first-order loss rate of HO2 onto aqueous(NH4)2 SO4 aerosol.Theγ(HO2) was elevated with increase of Cu(Ⅱ) concentrations in aqueous(NH4)2 SO4 aerosol.The threshold of Cu(Ⅱ) concentration was10^-3 mol/L for the dramatic increase of γ(HO2).It was found that γ(HO2) reached 0.1 when Cu(Ⅱ)concentration in aerosol was larger than 10^-3 mol/L,suggesting that γ(HO2) is very sensitive to concentration of transition metal ions in aerosol.
基金This research was partially supported by the California Air Resources Board and the San Joaquin Valleywide Air Pollution Study Agency under contract 2000-2005 PM.
文摘The UCD/CIT model was modified to include a process analysis(PA)scheme for gas and particulate matter(PM)to study the formation of secondary nitrate aerosol during a stagnant wintertime air pollution episode during the California Regional PM_(2.5)/PM_(10) Air Quality Study(CRPAQS)where detailed measurements of PM components are available at a few sites.Secondary nitrate is formed in the urban areas from near the ground to a few hundred meters above the surface during the day with a maximum modeled net increase rate of 4μg·m^(-3)·d^(-1) during the study episode.The secondary nitrate formation rate in rural areas is lower due to lower NO_(2).In the afternoon hours,near-surface temperature can be high enough to evaporate the particulate nitrate.In the nighttime hours,both the gas phase N_(2)O_(5) reactions with water vapor and the N_(2)O_(5) heterogeneous reactions with particle-bound water are important for secondary nitrate formation.The N_(2)O_(5) reactions are most import near the surface to a few hundred meters above surface with a maximum modeled net secondary nitrate increase rate of 1μg·m^(-3)·d^(-1) and are more significant in the rural areas where the O3 concentrations are high at night.In general,vertical transport during the day moves the nitrate formed near the surface to higher elevations.During the stagnant days,process analysis indicates that the nitrate concentration in the upper air builds up and leads to a net downward flux of nitrate through vertical diffusion and a rapid increase of surface nitrate concentration.
