Conjugated organic component-functionalized hourglass-type phosphomolybdates for visible-light photocatalytic Cr(VI)reduction in wide pH range

Abstra ct Utilizing efficient and durable photocatalysts for the removal of carcinogen Cr(Ⅵ)in wide pH water environment is of great significance for environment remediation.Herein,three conjugated organic component-functionalized hourglass-type phosphomolybdate hybrids with the formulas(H_(2)DBQ)[Fe(-H_(2)O)_(3)]_(2){Fe[P_(4)Mo_(6)0_(31)H_(7)]_(2)}·7H_(2)O(1),(H_(2)DBQ)_(2)(H_(2)DBP)[Fe(H_(2)O)_(4)]{Fe[P_(4)Mo_(6)O_(31)H_(7)]_(2)}·4H_(2)O(2),(H_(2)DBP)_(2){Fe[P_(4-)Mo_(6)O_(31)H_(9)]_(2)}·10H_(2)O(3)(DBQ=2,2'-dimehyl-6,6'-biquinoline;DBP=4,4'-diaminobiphenyl)were synthesized via hydrothermal method as photocatalysts for reducing Cr(Ⅵ)under visible light illumination.Structure analysis showed that hybrids 1-3 consist of hourglass-type[Fe(P_(4)Mo_(6)O_(31)H_(6))_(2)]^(10)-(abbr.Fe{P_(4)Mo_(6)}_(2))poly anionic clusters functionalized with different proportional of conjugated organic components(DBQ and DBP)effectively regulated their visible-light absorption capabilities and electron structures,which could be employed to reflect the structure-activity relationship of materials.When used as catalysts for reducing Cr(Ⅵ),hybrids 1-3 displayed distinct photocatalytic activities with Cr(Ⅵ)removal efficiencies of 91%,86%and 81%with only 10 W of white light being used as illumination,which are superior to that of pristine Fe{P_(4)Mo_(6)}_(2) salt(62%).Moreover,hybrid 1 also maintained high Cr(Ⅵ)removal efficiencies above~85%and high structural stabilities in solutions with wide pH ranges of2.5-10.0.Mechanism investigation showed that the higher organic component conjugation levels could promote the optic al absorption and facilitate the electron transfer between Fe{P_(4)Mo_(6)}_(2) and org anic components,thus resulting in effective Cr(Ⅵ)reduction photocatalytic efficacy.This work provides a viable way to design the photocatalysts based on polyoxometalates for removing wastewater pollutants.

Chemical looping gasification characteristics and kinetic analysis of Chlorella and its organic components

Chemical looping gasification(CLG)characteristics and kinetic analysis of Chlorella(CHL),simulated Chlorella(V-CHL)and medium-chain triglycerides(MCT)were investigated using a thermogravimetric analyzer coupled with an online mass spectrometer.The apparent activation energy was obtained via Kissinger-Akahira-Sunose(KAS)method.In the result of the weightless behavior,the addition of oxygen carrier inhibited the decomposition of V-CHL at lower temperatures but promoted its decomposition at high temperatures.The values of chemical looping process characteristic parameters showed that a 10 wt%oxygen carrier would maximize the release of volatile products in the CLG of MCT,with 5.12×10^(-6)%⋅min^(-1)⋅℃^(-3).Oxygen carriers also affected gaseous products.The LHV of gaseous products of CHL reached the largest when the oxygen carrier was 10 wt%,which was 8.13 MJ/m^(3).And the gaseous product of MCT had the largest LHV with 30 wt%oxygen carrier,which was 8.83 MJ/m^(3).According to the kinetic analysis,the minimum value of apparent activation energy of MCT chemical looping gasification was 89.54 kJ⋅mol^(-1) with the oxygen carrier of 30 wt%,which was 50%less than that of MCT pyrolysis.And the minimum value for V-CHL was obtained when the mass fraction of Fe2O3 was 50 wt%.This paper could provide a reference for the choice of algae,the design of reactors,and the targeted regulation of the gaseous product for the algae CLG process.

Prediction of methane production performances based on determination of organic components for different vegetable wastes

The rapid development of the economy has led to rapid consumption of fossil fuels,which results in extremely serious environmental problems.Biomass energy has been accepted as a way to reduce the usage of fossil fuels due to its cleanliness and renewability.In this study,vegetable wastes(VWs),an abundant kind of biomass resource,were treated by anaerobic digestion(AD)to be converted into methane.The total solids(TS),volatile solids(VS),elemental contents,and organic components of 17 kinds of typical VWs were systematically determined.The methane production performances were then measured and ranged from 120.1 mL/g VS(for pepper stem)to 377.7 mL/g VS(for bok choy).To easily and quickly predict the methane yields of VWs,a curvilinear relationship between different organic compositions(e.g.,cellulose,hemicellulose,lignin,non-structural carbohydrate,protein,and VFA contents)and methane production was established and proved to be a useful tool for methane prediction.Four kinetic models(first-order model,Fitzhugh model,Cone model,modified Gompertz model)were applied to simulate the process of AD,and Cone and modified Gompertz models were shown to describe the AD process well.This study will not only provide basic data about the characteristics and methane production of 17 kinds of VWs but also contribute a method for predicting the methane yields of vegetable wastes,which is also valuable in future agro-industrial applications.

Effects of soil organic matter components and iron aluminum oxides on aggregate stability during vegetation succession in granite red soil eroded areas

Soil aggregates determine the basic structure of soil,and their composition and stability are influenced by the various types of cementitious substances occurring in soil.To explore the main limiting factors of soil aggregation in the process of vegetation succession with granite as the parent material,five stages of vegetation succession in an eroded area were selected:bare land(BL),grassland(GL),grassland shrub transition land(GS),shrubland(SL)and secondary forest(SF).Soil samples were collected to determine the composition and stability of aggregates.The contents of organic and inorganic cementitious substances,including organic matter components and iron aluminum oxides,were determined at five soil aggregate grain levels.The results indicated that the stability of soil aggregates and the>0.25 mm water-stable aggregate content(WR_(0.25))increased with vegetation succession.Based on the Le Bissonnais(LB)method,the mean weight diameter(MWD)of soil aggregates increased,and the relative dissipation index(RSI)and relative mechanical crushing index(RMI)decreased.The humic acid(HA)and fulvic acid(FA)contents in soil aggregates increased with vegetation succession,and the soil humus content at the SF stage increased by more than 13.54%over the BL level.Upon different vegetation succession stage,the iron and aluminum oxides for the SL and the SF were at a high level,and the contents of free-form iron oxide(Fe_(d))and amorphous iron oxide(Fe_(o))for BL were high.Correlation analysis indicated that the soil humic degree(PQ)and the contents of amorphous alumina(Al_(o))were positively correlated with aggregate stability to varying degrees.Redundancy analysis(RDA)revealed that PQ values of 1-2 mm(PQ_(2))and 0.25-0.5 mm(PQ_(4))aggregates,the contents of Fe_(o) of bulk soil(Fe_(oB)),>2 mm(Fe_(o1)),1-2 mm(Fe_(o2)),and<0.25 mm(Fe_(o5))aggregates,and the contents of Al_(o) of>2 mm(Al_(o1))aggregates could explain 99.4%of the changes in soil aggregate stability at different vegetation succession stages.Al_(o1) had a contribution rate of 71.2%and is the key factor for improving the stability of soil aggregates.

The Changing Characteristics of Profile Distribution of Organic Nitrogen Components in Apple-pear Orchard Soil

In order to evaluate the effects of soil depth on the contents of soil organic nitrogen,organic nitrogen forms in apple-pear orchard soil profile were quantified using the method proposed by Bremner in 1965.The results indicated that in addition to the amino sugar-N,all the soil organic N components within the same soil layer in wasteland were more than those in apple-pear orchard soil;with the layer depth increasing,the contents of different organic nitrogen forms in apple-pear orchard soil and wasteland were decreased;and the proportion of each organic N component within total hydrolysable N was different,and the percentages of ammonia N and amino acid-N components within total hydrolysable N were higher,especially the percentage of ammonia N components within total hydrolysable N was the highest.

Effects of land use, climate, topography and soil properties on regional soil organic carbon and total nitrogen in the Upstream Watershed of Miyun Reservoir, North China

Soil organic carbon （SOC） and total nitrogen （TN） contents as well as their relationships with site characteristics are of profound importance in assessing current regional, continental and global soil C and N stocks and potentials for C sequestration and N conservation to offset anthropogenic emissions of greenhouse gases. This study investigated contents and distribution of SOC and TN under different land uses, and the quantitative relationships between SOC or TN and site characteristics in the Upstream Watershed of Miyun Reservoir, North China. Overall, both SOC and TN contents in natural secondary forests and grasslands were much higher than in plantations and croplands. Land use alone explained 37.2% and 38.4% of variations in SOC and TN contents, respectively. The optimal models for SOC and TN, achieved by multiple regression analysis combined with principal component analysis （PCA） to remove the multicollinearity among site variables, showed that elevation, slope, soil clay and water contents were the most significant factors controlling SOC and TN contents, jointly explaining 70.3% of SOC and 67.1% of TN contents variability. Only does additional 1.9% and 3% increase in the interpretations of SOC and TN contents variability respectively when land use was added to regressions, probably due to environment factors determine land use. Therefore, environmental variables were more important for SOC and TN variability than land use in the study area, and should be taken into consideration in properly evaluating effects of future land use changes on SOC and TN on a regional scale.

Electrothermal Driving Microcantilever Resonator as a Platform for Chemical Gas Sensing

In the current research,the use of a micromachined cantilever resonator as a platform for chemical gas sensing was examined.The microcantilever resonator integrates an electrothermal driving unit and a piezoresistive detecting unit,and it is fabricated by direct bonding a silicon-on-insulator（SOI） wafer.With a particular polymer layer coated on the surface of the microcantilever,a gas sensor for volatile organic components（VOCs） detection can be realized.The operation mechanism provides the microcantilever resonator with integrated circuit（IC） compatibility in terms of both the fabrication process and operating voltage.The configuration of the microcantilever resonator can optimize the performance of the gas sensor.The SOI wafer provides a solution for the integrated fabrication of the microstructure,transducers,electronics,and the precise control of the resonator parameters.In this paper,the principles,design,analysis,process,and demonstration of the gas sensor based on the microcantilever resonator are presented.The experimental results provide confirmation that the polymer-coated microcantilever resonator has excellent performance with regard to VOC detection.

Comparison of three-dimensional fluorescence analysis methods for predicting formation of trihalomethanes and haloacetic acids

This work investigated the application of several fluorescence excitation–emission matrix analysis methods as natural organic matter（NOM） indicators for use in predicting the formation of trihalomethanes（THMs） and haloacetic acids（HAAs）. Waters from four different sources（two rivers and two lakes） were subjected to jar testing followed by 24 hr disinfection by-product formation tests using chlorine. NOM was quantified using three common measures： dissolved organic carbon, ultraviolet absorbance at 254 nm, and specific ultraviolet absorbance as well as by principal component analysis, peak picking,and parallel factor analysis of fluorescence spectra. Based on multi-linear modeling of THMs and HAAs, principle component（PC） scores resulted in the lowest mean squared prediction error of cross-folded test sets（THMs： 43.7（μg/L）^2, HAAs： 233.3（μg/L）^2）. Inclusion of principle components representative of protein-like material significantly decreased prediction error for both THMs and HAAs. Parallel factor analysis did not identify a protein-like component and resulted in prediction errors similar to traditional NOM surrogates as well as fluorescence peak picking. These results support the value of fluorescence excitation–emission matrix–principal component analysis as a suitable NOM indicator in predicting the formation of THMs and HAAs for the water sources studied.