Investigation of CO and formaldehyde oxidation over mesoporous Ag/Co_3O_4 catalysts

CO and formaldehyde(HCHO)oxidation reactions were investigated over mesoporous Ag/Co3O4 catalysts prepared by one-pot(OP)and impregnation(IM)methods.It was found that the one-pot method was superior to the impregnation method for synthesizing Ag/Co3O4 catalysts with high activity for both reactions.It was also found that the catalytic behavior of mesoporous Co3O4 and Ag/Co3O4 catalysts for the both reactions was different.And the addition of silver on mesoporous Co3O4 did not always enhance the catalytic activity of final catalyst for CO oxidation at room temperature(20 C),but could significantly improve the catalytic activity of final catalyst for HCHO oxidation at low temperature(90 C).The high surface area,uniform pore structure and the pretty good dispersion degree of the silver particle should be responsible for the excellent low-temperature CO oxidation activity.However,for HCHO oxidation,the addition of silver played an important role in the activity enhancement.And the silver particle size and the reducibility of Co3O4 should be indispensable for the high activity of HCHO oxidation at low temperature.

Glutathione S-transferase(GST) gene expression profiles in two marine bivalves exposed to BDE-47 and their potential molecular mechanisms

Glutathione S-transferases(GSTs) are phase II enzymes that facilitate the detoxification of xenobiotics and play important roles in antioxidant defense. We investigated the expression patterns of seven Venerupis philippinarum GSTs( Vp GSTs) and four Mytilus galloprovincialis GSTs( Mg GSTs) following exposure to BDE-47. Differential expressions of the seven V p GSTs and four Mg GSTs transcripts were observed,with differences between the hepatopancreas and gills. Among these GSTs,the sigma classes( Vp GSTS1,Vp GSTS2,Vp GSTS3,Mg GST1,and Mg GST3) were highly expressed in response to BDE-47 exposure,demonstrating their potential as molecular biomarkers for environmental biomonitoring studies. We obtained the three-dimensional crystal structures of V p GSTs and Mg GSTs by homologous modeling. A model to elucidate the binding interactions between the ligands and receptors was defined by molecular docking. Hydrophobic and π were the most often observed interactions between BDE-47 and the GSTs.

Catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al2O_(3) in a rotating packed bed

This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-MnCu/γ-Al_(2)O_(3)(Cat)in a rotating packed bed(RPB)for the first time.The results showed that the value of the overall decomposition rate constant of ozone(K_(c))and overall volumetric mass transfer coefficient(K_(L)a)are 4.28×10^(-3) s^(-1) and 11.60×10^(-3) s^(-1) respectively at an initial pH of 6,βof 40,Co3(g)of 60 mg·L^(-1)and Q_(L) of 85 L·h^(-1) in deionized water,respectively.Meanwhile,the K_(c) and K_(L)a values of Fenhe water are0.88×10^(-3) s^(-1) and 2.51×10^(-3) s^(-1) lower than deionized water,respectively.In addition,the K_(c) and K_(L)a values in deionized water for the Cat/O_(3)-RPB system are 44.86%and 47.41%higher than that for the Cat/O_(3)-BR(bubbling reactor)system,respectively,indicating that the high gravity technology can facilitate the decomposition and mass transfer of ozone in heterogeneous catalytic ozonation and provide some insights into the industrial wastewater.

Degradation of Benzene by Using a Silent-Packed Bed Hybrid Discharge Plasma Reactor

In this work,a novel gas phase silent-packed bed hybrid discharge plasma reactor has been proposed,and its ability to control a simulative gas stream containing 240 ppm benzene is experimentally investigated.In order to optimize the geometry of the reactor,the benzene conversion rate and energy yield(EY) were compared for various inner electrode diameters and quartz tube shapes and sizes.In addition,benzene removal efficiency in different discharge regions was qualitatively analyzed and the gas parameter(space velocity) was systematically studied.It has been found that silent-packed bed hybrid discharge plasma reactor can effectively decompose benzene.Benzene removal proved to achieve an optimum value of 60% with a characteristic energy density of 255 J/L in this paper with a 6 mm bolt high-voltage electrode and a 13 mm quartz tube.The optimal space velocity was 188.1 h-1,which resulted in moderate energy yield and removal efficiency.Reaction by-products such as hydroquinone,heptanoic acid,4-nitrocatechol,phenol and 4-phenoxy-phenol were identified by mean of GC-MS.In addition,based on these organic by-products,a benzene destruction pathway was proposed.

Quantitative modeling of freshwater stress in the nine water basins of Tanzania

Freshwater scarcity is a global issue of environmental concern that threatens agricultural production and human health.In this study,we established freshwater stress indices(WSIs) for the nine water basins of Tanzania by using the quantity of freshwater available and various water uses.The relationship between water availability and different water uses,including environmental water requirements,was analyzed,with uncertainty and sensitivity analysis performed by a Monte Carlo simulation technique.Extreme WSI values close to 1.00 were obtained in the Rufiji,Pangani,and Wami-ruvu basins,Internal drainage,and Lake Rukwa,while low and moderate WSI values ranging from 0.03 to 0.84 were found in Lake Victoria and the Ruvuma,Tanganyika,and Nyasa basins.This study adds further knowledge on the level of freshwater scarcity,relationships between water availability and different water uses,and suggests policy options to reduce freshwater scarcity at the basin level for sustainable water supply.

Estimation of crop residue in China based on a Monte Carlo analysis

Accurate crop residue resource estimation is important for bioenergy development.This is done by the ratio of residue to grain(R/G),which is usually regarded constant and is widely used for crop residue estimation though uncertainty is inevitable in practice.In this study,a Monte Carlo algorithm was applied to estimate national crop residue by R/G taken from published reports in China.The estimated result was further mapped in pixels by geographic information system.In2009,the amount of crop residue was found to be 802.32 million tons(Mt),with 679.36 and 947.28 Mt as the lower and upper limits for 95%confidence limits.Chinese crop residue was dominated by rice,wheat,and corn,accounting for74.57%(598.29 Mt).From 1949 to 2009,the amount of crop residue increased by four times,accompanied by component change.The spatial distribution of crop residue in China is markedly heterogeneous.Compared to the shortage of crop residue in northwest China,there is an abundant crop residue of about 334 Mt in eastern China,attracting 90%of the country's electricity or heat generation plants.

Adsorption and membrane separation for removal and recovery of volatile organic compounds

Volatile organic compounds(VOCs)are a crucial kind of pollutants in the environment due to their obvious features of severe toxicity,high volatility,and poor degradability.It is particularly urgent to control the emission of VOCs due to the persistent increase of concentration and the stringent regulations.In China,clear directions and requirements for reduction of VOCs have been given in the“national plan on environmental improvement for the 13th Five-Year Plan period”.Therefore,the development of efficient technologies for removal and recovery of VOCs is of great significance.Recovery technologies are favored by researchers due to their advantages in both recycling VOCs and reducing carbon emissions.Among them,adsorption and membrane separation processes have been extensively studied due to their remarkable industrial prospects.This overview was to provide an up-to-date progress of adsorption and membrane separation for removal and recovery of VOCs.Firstly,adsorption and membrane separation were found to be the research hotspots through bibliometric analysis.Then,a comprehensive understanding of their mechanisms,factors,and current application statuses was discussed.Finally,the challenges and perspectives in this emerging field were briefly highlighted.

Electrochemically enhanced adsorption of PFOA and PFOS on multiwalled carbon nanotubes in continuous flow mode

It is important to develop efficient technologies on removal of perfluorooctanoic acid(PFOA)and perfluorooctane sulfonate(PFOS)from water due to their wide distribution and potential threat to human health.In this work,a durable and convenient electrosorption device was designed in continuous flow mode to investigate the adsorption of PFOX(X=A and S)on multiwalled carbon nanotubes(MWNTs)from water under electrochemical assistance.The electrosorption experiments were conducted under different influent and electrolyte concentrations,hydraulic retention time(HRT)and electrode distance to optimize the operation.The results showed that the highest removal efficiencies toward both PFOA and PFOS could come up to 90%at 1 V.Compared with open circuit(OC)adsorption under the same conditions,the removal efficiencies were improved by 4.9 times(PFOA)and 4.2 times(PFOS)respectively.In addition,the MWNTs electrode was found to be reusable.These findings provide an efficient method to remove PFOX from water by electrosorption in continuous flow mode.

Progress and perspectives of quantitative structure-activity relationships used for ecological risk assessment of toxic organic compounds

Structure-activity relationship (SAR) and quantitative structure-activity relationship (QSAR), collec- tively referred to as (Q)SARs, play an important role in ecological risk assessment (ERA) of organic chemicals. (Q)SARs can fill the data gap for physical-chemical, environmental behavioral and ecotoxicological parameters of organic compounds; they can decrease experimental expenses and reduce the extent of experimental testing (especially animal testing); they can also be used to assess the uncertainty of the experimental data. With the development for several decades, (Q)SARs in envi- ronmental sciences show three features: application orientation, multidisciplinary integration, and in- telligence. Progress of (Q)SAR technology for ERA of toxic organic compounds, including endpoint selection and mathematic methods for establishing simple, transparent, easily interpretable and portable (Q)SAR models, is reviewed. The recent development on defining application domains and diagnosing outliers is summarized. Model characterization with respect to goodness-of-fit, stability and predictive power is specially presented. The purpose of the review is to promote the development of (Q)SARs orientated to ERA of organic chemicals.

鞍山某化工园区环境风险防控体系研究

化工园区的环境风险问题是当前化工园区规划建设中亟待解决的问题。本文以鞍山某化工园区为例,对化工园区在生产、运营的过程中可能产生的主要环境风险进行详细识别,并从风险管理系统、合理选址布局、伴生水环境风险、管道运输风险多个角度提出相应的风险防范措施,形成了一套较为完整的风险防控体系,为化工园区的环境风险防控提供有效的参考和指导。

Effective adsorption of 2,4-dichlorophenol on hydrogenated graphene: kinetics and isotherms

The effective adsorption capability of a hydrogenated graphene(H-Gr) was demonstrated. The H-Gr was firstly prepared by heating graphene(Gr) in a hydrogen flow at 1,000 °C. The specific surface area, layer number, zeta potential, surface defects, surface compounds groups and elemental ratio of H-Gr were investigated.Taking 2,4-dichlorophenol as a target pollutant, the adsorption ability of H-Gr was evaluated. The results showed that the adsorption kinetics followed the pseudosecond-order equation well. For the adsorption isotherms,the equilibrium data of H-Gr were found to fit to Langmuir model, which was different from the Freundlich model of Gr. The adsorption capacity of H-Gr was high to287.01 mg/g, almost three times as much as that of Gr,which was benefit from the increase of specific surface area and zeta potential. This work suggests that H-Gr may be a potential candidate for the adsorption of aromatic compounds from water and has great prospect for practical application.

Enhancement of toluene oxidation performance over La_(1-x)CoO_(3-δ) perovskite by lanthanum non-stoichiometry

La_(1-x)CoO_(3-δ)catalysts with different non-stoichiometry of lanthanum ions were synthesized by using the sol-gel method,and their catalytic performance in toluene combustion was investigated.The results showed that the catalytic activity and stability of A-site nonstoichiometric La_(1-x)CoO_(3-δ)were improved to a certain extent compared with pure LaCoO_(3)perovskite.Among them,the La_(0.9)CoO_(3-δ)catalyst gave the best catalytic performance for toluene oxidation.It achieved 90%toluene conversion at 205℃under the conditions of a WHSV(weight hourly space velocity)of 22,500 mL/(g·hr)and a 500 ppmV-toluene concentration.Various characterization techniques were used to investigate the relationship between the structure of these catalysts and their catalytic performance.It was found that the non-stoichiometric modification of the lanthanum ion at position A in LaCoO_(3)changed the surface element state of the catalyst and increased the oxygen vacancy content,thus,combined with improved reducibility,improving toluene degradation on the catalyst.

Novel quantitative structure activity relationship models for predicting hexadecane/air partition coefficients of organic compounds

Predicting the logarithm of hexadecane/air partition coefficient(L)for organic compounds is crucial for understanding the environmental behavior and fate of organic compounds and developing prediction models with polyparameter linear free energy relationships.Herein,two quantitative structure activity relationship(QSAR)models were developed with 1272 L values for the organic compounds by using multiple linear regression(MLR)and support vector machine(SVM)algorithms.On the basis of the OECD principles,the goodness of fit,robustness and predictive ability for the developed models were evaluated.The SVM model was first developed,and the predictive capability for the SVM model is slightly better than that for the MLR model.The applicability domain(AD)of these two models has been extended to include more kinds of emerging pollutants,i.e.,oraganosilicon compounds.The developed QSAR models can be used for predicting L values of various organic compounds.The van derWaals interactions between the organic compound and the hexadecane have a significant effect on the L value of the compound.These in silico models developed in current study can provide an alternative to experimental method for high-throughput obtaining L values of organic compounds.

Photodegradation of fluoroquinolone antibiotic gatifloxacin in aqueous solutions

Fluoroquinolone antibiotics (FQs) are frequently detected as emerging pollutants in aqueous environments.In this study,kinetics,influencing factors and mechanisms on the photodegradation of gatifloxacin,a representative FQ,were investigated.The photodegradation follows the pseudo-first-order kinetics.Gatifloxacin photodegrades with a quantum yield of (5.94 ± 0.95) × 10 3 in pure water and undergoes direct photolysis as well as self-sensitized photodegradation.The FQ photodegrades slower in freshwater and seawater than in pure water,which is attributed to the integrative effects of pH and the aqueous dissolved matter (e.g.,humic acids and NO 3-) on the photodegradation.A toxicity test using Vibrio fischeri revealed the formation of hazardous photoproducts.

Comparison of dynamic adsorption/desorption characteristics of toluene on different porous materials

Four different types of adsorbents, SBA-15, MCM-41, NaY and SiO2, were used to study the dynamic adsorption/desorption of toluene. To further investigate the influence of pore structure on its adsorption performance, two SBA-15 samples with different microspores were also selected. It is shown that microporous material NaY has the largest adsorption capacity of 0.2873 mL/g, and the amorphous SiO2 exhibits the least capacity of 0.1003 mL/g. MCM-41 also shows a lower break through capacity in spite of the relatively small pore diameter, because it can not provide the necessary small geometric confinement for the tiny adsorbates. However, the mesoporous SBA-15 silica with certain micropore volume shows relatively higher adsorption capacity than that of MCM-41 silica. The presence of micropores directly leads to an increase in the dynamic adsorption capacity of toluene. Although NaY has the highest adsorption capacity for toluene, its complete desorption temperature for toluene is high (> 350°C), which limits its wide application. On the contrary, mesoporous silica materials exhibits a good desorption performance for volatile organic compounds at lower temperatures. Among these materials mesoporous SBA-15 samples, with a larger amount micropores and a lower desorption temperature, are a potentially interesting adsorbent for the removal of volatile organic compounds. This behavior should been related with the best synergetic effect of mesopores and micropores.

Impact of dissolved organic matter on the photolysis of the ionizable antibiotic norfloxacin

Norfloxacin(NOR), an ionizable antibiotic frequently used in the aquaculture industry, has aroused public concern due to its persistence, bacterial resistance, and environmental ubiquity.Therefore, we investigated the photolysis of different species of NOR and the impact of a ubiquitous component of natural water — dissolved organic matter(DOM), which has a special photochemical activity and normally acts as a sensitizer or inhibiter in the photolysis of diverse organics; furthermore, scavenging experiments combined with electron paramagnetic resonance(EPR) were performed to evaluate the transformation of NOR in water. The results demonstated that NOR underwent direct photolysis and self-sensitized photolysis via hydroxyl radical(U OH) and singlet oxygen(1O2) based on the scavenging experiments. In addition, DOM was found to influence the photolysis of different NOR species, and its impact was related to the concentration of DOM and type of NOR species. Photolysis of cationic NOR was photosensitized by DOM at low concentration, while zwitterionic and anionic NOR were photoinhibited by DOM, where quenching of U OH predominated according to EPR experiments, accompanied by possible participation of excited triplet-state NOR and1O2. Photo-intermediate identification of different NOR species in solutions with/without DOM indicated that NOR underwent different photodegradation pathways including dechlorination, cleavage of the piperazine side chain and photooxidation, and DOM had little impact on the distribution but influenced the concentration evolution of photolysis intermediates. The results implied that for accurate ecological risk assessment of emerging ionizable pollutants, the impact of DOM on the environmental photochemical behavior of all dissociated species should not be ignored.

Steady performance of a zero valent iron packed anaerobic reactor for azo dye wastewater treatment under variable influent quality

Zero valent iron(ZVI) is expected to help create an enhanced anaerobic environment that might improve the performance of anaerobic treatment.Based on this idea,a novel ZVI packed upflow anaerobic sludge blanket(ZVI-UASB) reactor was developed to treat azo dye wastewater with variable influent quality.The results showed that the reactor was less influenced by increases of Reactive Brilliant Red X-3B concentration from 50 to 1000 mg/L and chemical oxygen demand(COD) from 1000 to 7000 mg/L in the feed than a reference UASB reactor without the ZVI.The ZVI decreased oxidation-reduction potential in the reactor by about 80 mV.Iron ion dissolution from the ZVI could buffer acidity in the reactor,the amount of which was related to the COD concentration.Fluorescence in situ hybridization test showed the abundance of methanogens in the sludge of the ZVI-UASB reactor was significantly greater than that of the reference one.Denaturing gradient gel electrophoresis showed that the ZVI increased the diversity of microbial strains responsible for high efficiency.

Photodegradation of 2-(2-hydroxy-5-methylphenyl) benzotriazole(UV-P) in coastal seawaters: Important role of DOM

Benzotriazole UV stabilizers (BT-UVs) have attracted concems due to their ubiquitous occurrence in the aquatic environment,and their bioaccumulative and toxic properties.However,little is known about their aquatic environmental degradation behavior.In this study,photodegradation of a representative of BT-UVs,2-(2-hydroxy-5-methylphenyl) benzotriazole (UV-P),was investigated under simulated sunlight irradiation.Results show that UV-P photodegrades slower under neutral conditions (neutral form) than under acidic or alkaline conditions (cationic and anionic forms).Indirect photodegradation is a dominant elimination pathway of UV-P in coastal seawaters.Dissolved organic matter (DOM) from seawaters accelerate the photodegradation rates mainly through excited triplet DOM (3DOM*),and the roles of singlet oxygen and hydroxyl radical are negligible in the matrixes.DOM from seawaters impacted by mariculture exhibits higher steady-state concentration of 3DOM*([3DOM*]) relative to those from pristine seawaters,leading to higher photosensitizing effects on the photodegradation.Halide ions inhibit the DOM-sensitized photodegradation of UV-P by decreasing [3DOM*].Photodegradation half-lives of UV-P are estimated to range from 24.38 to 49.66 hr in field water bodies of the Yellow River estuary.These results are of importance for assessing environmental fate and risk UV-P in coastal water bodies.

Highly catalytic activity of Mn/SBA-15 catalysts for toluene combustion improved by adjusting the morphology of supports

Rod-like, hexagonal and fiber-like SBA-15 mesoporous silicas were synthesized to support MnO_x for toluene oxidation. This study showed that the morphology of the supports greatly influenced the catalytic activity in toluene oxidation. MnO_x supported on rod-like SBA-15(R-SBA-15) displayed the best catalytic activity and the conversion at 230°C reached more than 90%, which was higher than the other two catalysts. MnO_x species consisted of coexisting MnO_2 and Mn_2O_3 on the three kinds of SBA-15 samples. Large amounts of Mn_2O_3 species were formed on the surface and high oxygen mobility was obtained on MnO_x supported on R-SBA-15, according to the H_2 temperature programmed reduction(H_2-TPR)and X-ray photoelectron spectroscopy(XPS) results. The Mn/R-SBA-15 catalyst with greater amounts of Mn_2O_3 species possessed a large amount of surface lattice oxygen, which accelerated the catalytic reaction rate. Therefore, the surface lattice oxygen and high oxygen mobility were critical factors on the catalytic activity of the Mn/R-SBA-15 catalyst.

Toward rational design of amines for CO_2 capture: Substituent effect on kinetic process for the reaction of monoethanolamine with CO_2

Amines have been considered as promising candidates for post-combustion CO2 capture. A mechanistic understanding for the chemical processes involved in the capture and release of CO2 is important for the rational design of amines. In this study, the structural effects of amines on the kinetic competition among three typical products(carbamates, carbamic acids and bicarbonate) from amines + CO2 were investigated, in contrast to previous thermodynamic studies to tune the reaction of amines with CO2 based on desirable reaction enthalpy and reaction stoichiometry. We used a quantum chemical method to calculate the activation energies(Ea) for the reactions of a range of substituted monoethanolamines with CO2 covering three pathways to the three products. The results indicate that the formation of carbamates is the most favorable, among the three considered products. In addition, we found that the Eavalues for all pathways linearly correlate with pK aof amines, and more importantly, the kinetic competition between carbamate and bicarbonate absorption pathways varies with p Kaof the amines, i.e. stronger basicity results in less difference in Ea. These results highlight the importance of the consideration of kinetic competition among different reaction pathways in amine design.