Effects of impregnation sequence on the NH_(3)-SCR activity and hydrothermal stability of a Ce-Nb/SnO_(2) catalyst

Hydrothermal stability is crucial for the practical application of deNO_(x)catalyst on diesel vehicles,for the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR).SnO_(2)-based materials possess superior hydrothermal stability,which is attractive for the development of NH_(3)-SCR catalyst.In this work,a series of Ce-Nb/SnO_(2)catalysts,with Ce and Nb loading on SnO_(2)support,were prepared by impregnation method.It was found that,the NH_(3)-SCR activities and hydrothermal stabilities of the Ce-Nb/SnO_(2)catalysts significantly varied with the impregnation sequences,and the Ce-Nb(f)/SnO_(2) catalyst that firstly impregnated Nb and then impregnated Ce exhibited the best performance.The characterization results revealed that CeNb(f)/SnO_(2)possessed appropriate acidity and redox capability.Furthermore,the strong synergistic effect between Nb and Sn species stabilized the structure and maintained the dispersion of acid sites.This study may provide a new understanding for the effect of impregnation sequence on activity and hydrothermal stability and a new environmental-friendly NH_(3)-SCR catalyst with potential applications for NO_(x)removal from diesel and hydrogenfueled engines.

Promoted NH_(3)-SCR activity and hydrothermal stability of Cu-SSZ-50 catalyst synthesized by one-pot method

Nitrogen oxide(NO_(x))is one of the most critical contaminants in the air,and the control of NO_(x)emission from diesel vehicles is very important.Cu-based small-pore zeolites have already been applied for NO_(x)abatement on diesel vehicles.Among the small-pore zeolites,Cu-SSZ-50 catalysts with good NH_(3)-SCR catalytic activity were believed to have potential for application.In this study,a one-pot synthesis method for Cu-SSZ-50 catalysts was developed for the first time,using the co-templates of Cu-TEPA and 2,6-dimethyl-N-methylpyridinium hydroxide.In this synthesis method,Cu-SSZ-50 with various Cu contents can be obtained by adjusting the amount of Cu-TEPA without the need for a further after-treatment process.The addition of Cu-TEPA affected the framework atoms and Cu species,and a lower Si/Al ratio and more SCR active Cu species were obtained.The synthesized catalyst with a Cu/Al ratio of 0.40 exhibited over 90%NO_(x)conversion between 200℃and 450℃for the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR).Meanwhile,over 80%NO_(x)conversion could be obtained from 250℃to 450℃after hydrothermal aging at 750℃for 16 h.In addition,both L-H and E-R mechanisms were proven to exist for the one-pot-synthesized Cu-SSZ-50 by in situ DRIFTS experiments.The simple synthesis procedure,excellent catalytic activity and hydrothermal stability brighten the prospects for the application of Cu-SSZ-50.

Different responses of soil fauna gut and plant rhizosphere microbiomes to manure applications

Microbial attributes were compared between soil fauna gut and plant rhizosphere.•Manure applications decreased or increased gut or rhizosphere bacterial diversity.•Stochastic or deterministic processes drove gut or rhizosphere bacterial assembly.•Manure applications increased bacterial network complexity of gut and rhizosphere.Diverse microbes inhabit animals and plants,helping their hosts perform multiple functions in agricultural ecosystems.However,the responses of soil fauna gut and plant rhizosphere microbiomes to livestock manure applications are still not well understood.Here we fed Protaetia brevitarsis larvae(PBL)with chicken manure and collected their frass.The frass and manure were applied as fertilizers to lettuce pots.We then compared the changes of microbial diversity,community assembly,and potential functions between the gut group(i.e.,all PBL gut and frass samples)and the rhizosphere group(i.e.,all rhizosphere soil samples).We revealed that manure applications(i.e.,feeding or fertilization)decreased bacterial diversity in the gut group but increased that in the rhizosphere group.Particularly,the proportions of Bacilli in the gut group and Gammaproteobacteria in the rhizosphere group were increased(up to a maximum of 33.8%and 20.4%,respectively)after manure applications.Stochastic and deterministic processes dominated community assembly in the gut and rhizosphere microbiomes,respectively.Manure applications increased the microbial co-occurrence network complexity of both the gut and rhizosphere groups.Moreover,the proportions of functional taxa associated with human/animal pathogens in the gut group and carbon/nitrogen cycling in the rhizosphere group were enhanced(up to 2.6-fold and 24.6-fold,respectively).Our findings illustrate the different responses of microbial diversity,community assembly,and potential functions in soil fauna gut and plant rhizosphere to manure applications.The results could enhance our knowledge on the reasonable utilization of animal and plant microbiomes in agricultural management.

Ecology and risks of the global plastisphere as a newly expanding microbial habitat

Plastic offers a new niche for microorganisms,the plastisphere.The everincreasing emission of plastic waste makes it critical to understand the microbial ecology of the plastisphere and associated effects.Here,we present a global fingerprint of the plastisphere,analyzing samples collected from freshwater,seawater,and terrestrial ecosystems.The plastisphere assembles a distinct microbial community that has a clearly higher heterogeneity and a more deterministically dominated assembly compared to natural habitats.New coexistence patterns—loose and fragile networks with mostly specialist linkages among microorganisms that are rarely found in natural habitats—are seen in the plastisphere.Plastisphere microbiomes generally have a great potential to metabolize organic compounds,which could accelerate carbon turnover.Microorganisms involved in the nitrogen cycle are also altered in the plastisphere,especially in freshwater plastispheres,where a high abundance of denitrifiers may increase the release of nitrite(aquatic toxicant)and nitrous oxide(greenhouse gas).Enrichment of animal,plant,and human pathogens means that the plastisphere could become an increasingly mobile reservoir of harmful microorganisms.Our findings highlight that if the trajectory of plastic emissions is not reversed,the expanding plastisphere could pose critical planetary health challenges.

Tuning SMSI to stabilize metallic Pd species:A case study on Pd/TiO_(2) for HCHO oxidation

Pretreatment of the carrier for supported catalysts can effectively improve the strong metal-support interaction(SMSI)and increase the dispersion of precious metals,which are critical to many important catalytic reactions.In this work,we tuned SMSI on Pd/TiO_(2)catalysts through inducing surface defects of TiO_(2)by pretreated with different atmospheres(H_(2)/N_(2),N_(2),O_(2)/N_(2))at the high temperature(800℃).Multiple characterization results illustrated that surface defects anchored Pd species and thus enhanced their dispersion.During reduction,Ti^(3+)species formed and transferred onto the metallic Pd species and then induced SMSI,which effectively stabilize Pd species in the metallic state.The stronger MSI,the more stability of Pd species.As a case,Pd/TiO_(2)–800H_(2),with strongest MSI,displayed the best HCHO oxidation performance at low temperature(10℃).

Stochastic community assembly of abundant taxa maintains the relationship of soil biodiversity-multifunctionality under mercury stress

Soil abundant taxa diversity positively related to multifunctionality under Hg stress.•Microbial network complexity of soil abundant taxa supported the strength of SBF.•Stochastic assembly of soil abundant subcommunity supported the strength of SBF.•Stochastic ratio was the most important predictor for the strength of SBF.It is known that soil microbial communities are intricately linked to multiple ecosystem functions and can maintain the relationship between soil biodiversity and multifunctionality(SBF)under environmental stresses.However,the relative contributions and driving forces of abundant and rare taxa within the communities in maintaining soil biodiversity-multifunctionality relationship under pollution stresses are still unclear.Here,we conducted microcosm experiments to estimate the importance of soil abundant and rare taxa in predicting these relationships under heavy metal mercury(Hg)stress in paired paddy and upland fields.The results revealed that the diversity of abundant taxa,rather than rare taxa,was positively related to multifunctionality,with the abundant subcommunity tending to maintain a larger proportion of soil functions including chitin degradation,protein degradation,and phosphorus mineralization.Soil multitrophic network complexity consisting of abundant species showed positive correlations with biodiversity and multifunctionality,and supported the strength of SBF within a network complexity range.Stochastic assembly processes of the abundant subcommunity were positively correlated with the strength of SBF,although stochastic processes decreased the biodiversity and the multifunctionality,respectively.After simultaneously accounting for multiple factors on the strength of SBF,we found that the stochastic community assembly ratio of abundant taxa was the most important predictor for SBF strength under Hg stress.Our results highlight the importance of abundant taxa in supporting soil multifunctionality,and elucidate the linkages between community assembly,network complexity and SBF relationship under environmental stresses.

Dynamic changes in soil chemical properties and microbial community structure in response to different nitrogen fertilizers in an acidified celery soil

To determine the effects of different kinds of nitrogen fertilizer,especially high-efficiency slowrelease fertilizers,on soil pH,nitrogen(N)and microbial community structures in an acidic celery soil,four treatments(CK,no N fertilizer;NR,urea;PE,calcium cyanamide fertilizer;and SK,controlled-release N fertilizer)were applied,and soil pH,total soil N,inorganic N,and soil microbial biomass C were analyzed.Phospholipid fatty acids(PLFAs)were extracted and detected using the MIDI Sherlock microbial identification system.The PE treatment significantly improved soil pH,from 4.80 to>6.00,during the whole growth period of the celery,and resulted in the highest celery yield among the four treatments.After 14 d application of calcium cyanamide,the soil nitrate content significantly decreased,but the ammonium content significantly increased.The PE treatment also significantly increased soil microbial biomass C during the whole celery growth period.Canonical variate analysis of the PLFA data indicated that the soil microbial community structure in the CK treatment was significantly different from those in the N applied treatments after 49 d fertilization.However,there was a significant difference(P<0.05)in soil microbial community structure between the PE treatment and the other three treatments at the end of the experiment.Calcium cyanamide is a good choice for farmers to use on acidic celery land because it supplies sufficient N,and increases soil pH,microbial biomass and the yield of celery.

The effect of hydrogen reduction of α-MnO_(2) on formaldehyde oxidation: The roles of oxygen vacancies

A series of α-MnO_(2) catalysts with various Mn valence states were treated by hydrogen reduction for different periods of time. Their catalytic capacity for formaldehyde(HCHO) oxidation was evaluated. The results indicated that hydrogen reduction dramatically improves the catalytic performance of α-MnO_(2) in HCHO oxidation. The α-MnO_(2) sample reduced by hydrogen for 2 h possessed superior activity and could completely oxidize 150 ppm HCHO to CO_(2) and H_(2)O at 70℃. Multiple characterization results illustrated that hydrogen reduction contributed to the production of more oxygen vacancies. The oxygen vacancies on the catalyst surface enhanced the adsorption, activation and mobility of O_(2) molecules, and thereby enhanced HCHO catalytic oxidation. This study provides novel insight into the design of outstanding MnO_x catalysts for HCHO oxidation at low temperature.

treatment of swine wastewater in aerobic granular reactors： comparison of different seed granules as factors

The granulation process, physic-chemical properties, pollution removal ability and bacterial com- munities of aerobic granules with different feed-waste- water （synthetic wastewater, R1; swine wastewater, R2）, and the change trend of some parameters of two types of granules in long-term operated reactors treating swine wastewater were investigated in this experiment. The result indicated that aerobic granulation with the synthetic wastewater had a faster rate compared with swine waste- water and that full granulation in R 1 and R2 was reached on the 30th day and 39th day, respectively. However, although the feed wastewater also had an obvious effect on the biomass fraction and extracellular polymeric sub- stances of the aerobic granules during the granulation process, these properties remained at a similar level after long-term operation. Moreover, a similar increasing trend could also be observed in terms of the nitrogen removal efficiencies of the aerobic granules in both reactors, and the average specific removal rates of the organics and ammonia nitrogen at the steady-state stage were 35.33mg.g^-1 VSS and 51.46mg.g^-1 VSS for R1, and 35.47mg.g^-1 VSS and 51.72mg.g^-1 VSS for R2, respectively. In addition, a shift in the bacterial diversity occurred in the granulation process, whereas bacterial communities in the aerobic granular reactor were not affected by the seed granules after long-term operation.

Investigation of suitable precursors for manganese oxide catalysts in ethyl acetate oxidation

The control of ethyl acetate emissions from fermentation and extraction processes in the pharmaceutical industry is of great importance to the environment.We have developed three Mn_(2)O_(3)catalysts by using different Mn precursors(MnCl_(2),Mn(CH_(3)COO)_(2),MnSO_(4)),named as Mn_(2)O_(3)-Cl,-Ac,-SO_(4).The tested catalytic activity results showed a sequence with Mn precursors as:Mn_(2)O_(3)-Cl>Mn_(2)O_(3)-Ac>Mn_(2)O_(3)-SO_(4).The Mn_(2)O_(3)-Cl catalyst reached a complete ethyl acetate conversion at 212℃(75℃lower than that of Mn_(2)O_(3)-SO_(4)),and this high activity 100%could be maintained high at 212℃for at least 100 hr.The characterization data about the physical properties of catalysts did not show an obvious correlation between the structure and morphology of Mn_(2)O_(3)catalysts and catalytic performance,neither was the surface area the determining factor for catalytic activity in the ethyl acetate oxidation.Here we firstly found there is a close linear relationship between the catalytic activity and the amount of lattice oxygen species in the ethyl acetate oxidation,indicating that lattice oxygen species were essential for excellent catalytic activity.Through H_(2)temperature-programmed reduction(H_(2)-TPR)results,we found that the lowest initial reduction temperature over the Mn_(2)O_(3)-Cl had stronger oxygen mobility,thus more oxygen species participated in the oxidation reaction,resulting in the highest catalytic performance.With convenient preparation,high efficiency,and stability,Mn_(2)O_(3)prepared with MnCl_(2)will be a promising catalyst for removing ethyl acetate in practical application.