Atomically dispersed dinuclear iridium active sites for efficient and stable electrocatalytic chlorine evolution reaction.

The electrochemical chlorine evolution reaction (CER) is a critical anode reaction in chlor-alkali electrolysis. Although precious metal-based mixed metal oxides (MMOs) have long been used as CER catalysts, they suffer from high cost and poor selectivity due to the competing oxygen evolution reaction (OER). Single-atom catalysts (SACs), featuring high atom utilization efficiency, have captured widespread interest in diverse applications. However, the single-atom sites in SACs are generally recognized as independent motifs and the interplay of adjacent sites is largely overlooked. Herein, we report a "precursor-preselected" cage-encapsulated strategy to synthesize atomically dispersed dinuclear iridium active sites bridged by oxygen that are supported on nitrogen-doped carbon (Ir2-ONC). The dinuclear Ir2-ONC catalyst exhibits a CER onset potential of 1.375 V vs. normal hydrogen electrode, a high faradaic efficiency of >95%, and a high mass activity of 14321.6 A gIr -1, much better than the Ir SACs, which demonstrates the significance of coordination and electronic structure regulation for atomically dispersed catalysts. Density functional theory calculations and ab initio molecular dynamics simulations confirm that the unique dinuclear structure facilitates Cl- adsorption, resulting in improved catalytic CER performance.

Evaluation of immunoregulation and immunoprotective efficacy of Glaesserella parasuis histidine kinase QseC.

QseC is a membrane sensor kinase that enables bacteria to perceive autoinducers -3, adrenaline, and norepinephrine to initiate downstream gene transcription. In this study, we found that the QseC protein of Glaesserella parasuis can serve as an effective antigen to activate the host's immune response. Therefore, we investigated the immunogenicity and host protective effect of this protein. ELISA and indirect immunofluorescence results showed that QseC protein can induce high titer levels of humoral immunity in mice and regularly generate specific serum antibodies. We used MTS reagents to detect lymphocyte proliferation levels and found that QseC protein can cause splenic lymphocyte proliferation with memory and specificity. Further immunological analysis of the spleen cell supernatant revealed significant upregulation of levels of IL-1ß, IL-4 and IFN-γ in the QseC + adjuvant group. In the mouse challenge experiment, it was found that QseC + adjuvant can provide effective protection. The results of this study demonstrate that QseC protein provides effective protection in a mouse model and has the potential to serve as a candidate antigen for a novel subunit vaccine for further research.

Design optimization and experimental study of a novel mechanism for a hover-able bionic flapping-wing micro air vehicle.

Allomyrina dichotomahas a natural ultra-high flying ability and maneuverability. Especially its ability to fly flexibly in the air, makes it more adaptable to the harsh ecological environment. In this study, a bionic flapping-wing micro air vehicle (FMAV) is designed and fabricated by mimicking the flight mode ofA. dichotoma. Parametric design was employed for combining the airframe structure and flight characteristics analysis. To improve the transmission efficiency and compactness of the FMAV mechanisms, this study first analyses the body structure ofA. dichotoma, and then proposes a novel mechanism of FMAV based on its biological motion characteristics, the flight motion characteristics, and its musculoskeletal system. By optimizing the flapping-wing mechanism and mimicking the flying mechanism ofA. dichotoma, the large angle amplitude and the high-frequency flapping motion can be achieved to generate more aerodynamic force. Meanwhile, to improve the bionic effect and the wing performance of FMAV, the flexible deformation ofA. dichotomawings for each flapping period was observed by a high-speed camera. Furthermore, the bionic design of wings the prototype was carried out, therefore the wings can generate a high lift force in the flapping process. The experiment demonstrated that the aircraft can achieve a flapping angle of 160 degrees and 30 Hz flapping frequency. The attitude change of FMAV is realized by mimicking the movement for the change of attitude of theA. dichotoma, by changing the angle of attack of the wing, and executing the flight action of multiple degrees of freedom including pitch, roll and yaw. Finally, the aerodynamic experiment demonstrated that the prototype can offer 27.8 g lift and enough torque for altitude adjustment.

Bacterial community structure upstream and downstream of cascade dams along the Lancang River in southwestern China.

Extensive construction of dams by humans has caused alterations in flow regimes and concomitant alterations in river ecosystems. Even so, bacterioplankton diversity in large rivers influenced by cascade dams has been largely ignored. In this study, bacterial community diversity and profiles of seven cascade dams along the720 km of the Lancang River were studied using Illumina sequencing of the V3-V4 hypervariable region of the 16S rRNA gene. Spatiotemporal variations of bacterial communities in sediment and water of the Gongguoqiao hydroelectric dam and factors affecting these variations were also examined. Microbial diversity and richness in surface water increased slightly from upstream toward downstream along the river. A significant positive correlation between spatial distance and dissimilarities in bacterial community structure was confirmed (Mantel test, r = 0.4826, p = 0.001). At the Gongguoqiao hydroelectric dam, temporal differences in water overwhelmed spatial variability in bacterial communities. Temperature, precipitation, and nutrient levels were major drivers of seasonal microbial changes. Most functional groups associated with carbon cycling in sediment samples decreased from winter to summer. Our findings improve our understanding of associations, compositions, and predicted functional profiles of microbial communities in a large riverine ecosystem influenced by multiple cascade dams.

Seasonal effects of river flow on microbial community coalescence and diversity in a riverine network.

Terrestrial microbial communities may take advantage of running waters and runoff to enter rivers and mix with aquatic microorganisms. However, the environmental factors governing the interchange of the microbial community within a watercourse and its surrounding environment and the composition of the resulting community are often underestimated. The present study investigated the effect of flow rate on the mixing of water, soil, sediment and biofilm at four sites along the Lancang River and one branch of the river in winter and summer and, in turn, the resultant changes in the microbial community within each habitat. 16S rRNA gene-based Illumina high-throughput sequencing illustrated that bacterial communities were apparently distinct among biofilm, water, soil and sediment. Biofilms had the lowest richness, Shannon diversity and evenness indices compared with other habitats, and those three indices in all habitats increased significantly from winter to summer. SourceTracker analysis showed a significant coalescence between the bacterial communities of sediment, water and biofilm samples at lower flow rates. Additionally, the proportion of Betaproteobacteria in sediment and biofilms increased with a decrease in flow rate, suggesting the flow rate had a strong impact on microbial community composition and exchange among aquatic habitats. These results were further confirmed by a Mantel test and linear regression analysis. Microbial communities in all samples exhibited a significant but very weak distance-decay relationship (r = 0.093, P = 0.024). Turbidity played a much more important role on water bacterial community structure in summer (i.e. rainy season) (BIOENV, r = 0.92). Together, these results suggest that dispersal is an important factor affecting bacterial community structure in this system.

Bacterial Abundance and Physicochemical Characteristics of Water and Sediment Associated with Hydroelectric Dam on the Lancang River China.

Research on bacterial abundance in water column and sediment of dammed rivers remain poorly understood, despite their importance to biogeochemical processes, benthic ecology, and bioremediation. The present study investigates the water and sediment bacteria by epifluorescence microscopy in the reservoir (above the dam site), as well as in the downstream river stretches (below-dam site) at the middle reach of Lancang River during the wet, the normal and the dry seasons. The results demonstrated that the reservoir operating regime (water discharge variations) and strong precipitation promoted significant differences in the conditions of the river below the dam, especially for the concentration of dissolved oxygen, redox potential, electric conductivity, turbidity, and total dissolved solids in water and concentration of microbial activity in sediment. The seasonal variations were also key factors influencing water quality at the below-dam sampling sites. Nutrients concentration did not induce a significant response in bacterial abundance when inorganic nutrients were sufficient. Bacterial density in sediment was regulated by hydropower-related discharge, particle size, and type of sediments, while bacterial abundances in water were strongly linked with the physicochemical characteristics of the water, such as total dissolved solids and conductivity.

Understanding azo dye anaerobic bio-decolorization with artificial redox mediator supplement: Considering the methane production.

Artificial redox mediators (ARM) have been proven to accelerate the azo dye anaerobic bio-reduction (ADAB) but the mechanisms involved are still unclear. Previous studies do seldom focus on the production of methane during the ADAB, particularly if supplemented with ARM. Our studies revealed that the supplement of ARM could significantly accelerate the decolorization rate, recover the inhibited methanogenesis and decrease extracellular polymeric substance secretion in an ADAB system. Supplement of an ARM only enhanced the pre-existing metabolic pathway of the ADAB system. Significant differences in metabolic pathway and microbial community were found between traditional methanogenic system and ADAB system by high-throughput sequencing technique. The ADAB system performed an "over-requirement for electron donor" phenomenon and the requirement amount can be altered by regulating ARM dosage. Response surface methodology was then successfully employed to optimize the dosage of ARM and possible additional electron donor required for ADAB under different conditions.

Effect of low temperature of thermal pretreatment on anaerobic digestion of textile dyeing sludge.

The minimization and methane production of textile dyeing sludge (TDS) can be simultaneously attained via anaerobic digestion (AD). However, the possible toxicity and complex recalcitrant organic matters involved in limited the hydrolysis of TDS. Therefore, the low-temperature of thermal pretreatment (LTTP) lasting for 1h at temperatures from 60 to 100°C was employed to accelerate the hydrolysis and subsequent methane generation of TDS. The results showed that LTTP with temperatures higher than 70°C obviously improve the AD performance of TDS. Highest accumulative methane production was achieved for 100°C pretreated TDS and from thermal analysis point of view it was due to the disintegration of some recalcitrant macromolecules in TDS. Nevertheless, 90°C pretreated TDS did not perform favorable methane yield as expected, attributing to the inhibited acetogenesis as well as the hindered methanogenesis which was simultaneously competed by dye reducer for electrons.

[Effects of Bamboo Biochar on Greenhouse Gas Emissions During the Municipal Sludge Composting Process].

Effect of adding bamboo biochar into the compost at different dosages on greenhouse gas emissions was investigated by analyzing the dynamic characteristics of the process of municipal sludge composting with four different composts (S1:adding 2.5% bamboo biochar, S2:adding 5% bamboo biochar, S3:adding 10% bamboo biochar, CK:without bamboo biochar). The results showed that CH4 emissions mainly occurred during the heating period and the beginning of the altithermal period, accounting for 99.01%-99.81% of the total emissions. When the added bamboo biochar is less than 5%, CH4 emissions decrease with the increase in the amount of bamboo biochar. If it is more than 5%, CH4 emissions will clearly increase. CO2 emissions mainly occurred during the heating period and the altithermal period, accounting for 75.65%-86.58% of the total emissions. Adding bamboo biochar can reduce 3.37%-13.48% of the CO2 emissions but there is no significant difference between the treatments (P>0.05). N2O emissions mainly occurred during the heating period and the rotten period. Adding bamboo biochar can reduce the emissions of N2O; the more the amount of bamboo biochar, the less N2O emissions (P<0.05). The emission factors of CK, S1, S2, and S3 were 44.10, 37.57, 35.10, and 35.44 kg·t-1 of dry sludge, respectively. S1, S2, and S3 showed 14.81%-20.41% reduction in greenhouse gas emissions owing to the addition of bamboo biochar, indicating that bamboo biochar can reduce the carbon emissions in the process of sludge composting.

Anaerobic digestion of recalcitrant textile dyeing sludge with alternative pretreatment strategies.

Abundant organic compounds in textile dyeing sludge (TDS) provide possibility for its anaerobic digestion (AD) treatment. However, preliminary test showed little biogas generation in direct AD of the TDS during 20days. In order to improve the AD availability of TDS, alkaline, acid, thermal and thermal alkaline pretreatments were performed. Color and aromatic amines were specifically measured as extra characteristics for the AD of TDS. The rate-limiting steps of AD of TDS were slow hydrolysis rate and inhibited acidogenesis, which were somewhat overcome by pretreatments. Thermal alkaline pretreated TDS performed best enhancement on solubilisation. The biochemical methane potential tests revealed that thermal pretreated TDS showed highest total methane production of 55.9mL/gVSfed compared to the control with little methane generation. However, thermal alkaline pretreated TDS did not perform well in BMP test as expected. Moreover, the hydrophilicity of reactive dyes in TDS could seriously affect dewaterability of TDS.

Inhibitory effect and mechanism of azo dyes on anaerobic methanogenic wastewater treatment: Can redox mediator remediate the inhibition?

Inhibitory effect of azo dyes on anaerobic methanogenic wastewater treatment (AMWT) has been studied mainly focusing on biological toxicity in the batch test with simulated sole co-substrate. Detailed information on inhibitory effect and mechanism of azo dyes during the long-term operation with real complex co-substrate is limited. Moreover, whether redox mediator (RM) could remediate the inhibition is still unclear in previous studies, especially under the complex scenario. In this study, the real textile wastewater with alternative concentrations of azo dyes (0-600 mg/L) were used to operate a lab-scale high-rate anaerobic methanogenic bioreactor for 127 days, and 50 µM anthraquinone-2-sulfonate (AQS) as RM was added at the last period of operation. Azo dyes with concentration of 600 mg/L could cause significant inhibition on overall (decolorizing and methanogenic) performance of AMWT. Specific methanogenic activity assays showed that acetoclastic methanogens was more susceptible to high concentration azo dyes than hydrogenotrophic methanogens. The spatial distribution of extracellular polymeric substance in the anaerobic granular sludge (AGS) showed that the high biological toxicity of azo dyes was mainly attributed to enrichment effect in tightly bound-EPS (TB-EPS). The channels of AGS was clogged by azo dyes, which was evidenced by the hard release of aromatic amines in EPSs as well as decreased porosity of AGS and scanning electron microscope images. Meanwhile, the settling ability, particle size and strength of AGS all deteriorated after azo dyes concentration exceeded 450 mg/L. The dosing of AQS could mostly remediate overall performance of the bioreactor even if the recovery of acetoclastic methanogens was slow. However, except for the porosity with a part of recovery, physical characteristics of AGS hardly recovered, and washout of sludge from the bioreactor was still happening. It suggested that additional attention should be paid to prevent sludge from washout if RM was practically used to remediate the anaerobic reactor inhibited by azo dyes.

Shock resistance characteristic of a spiral symmetry stream anaerobic bio-reactor.

The shock resistance characteristic (SRC) of an anaerobic bioreactor characterizes the ability of the anaerobic community in the reactor to withstand violent change in the living environment. In comparison with an upflow anaerobic sludge blanket reactor (UASBR), the SRC of a spiral symmetry stream anaerobic bio-reactor (SSSAB) was systematically investigated in terms of removal efficiency, adsorption property, settling ability, flocculability and fluctuations in these parameters. A quantitative assessment method for SRC was also developed. The results indicated that the SSSAB showed better SRC than the UASBR. The average value (m value) of chemical oxygen demand removal rates of the SSSAB was 86.0%. The contact angle of granules in the SSSAB present gradient distribution, that is the m value of contact angle increasing from bottom (84.5°) to top (93.9°). The m value of the density at the upper and lower sections of the SSSAB were 1.0611 g·cm(-3) and 1.0423 g·cm(-3), respectively. The surface mean diameter of granules in the SSSAB increased from 1.164 to 1.292 mm during operation. The absolute m value of zeta potential of granular sludge at the upper and lower sections of the SSSAB were 40.4 mV and 44.9 mV, respectively. The weighted mean coefficient variance (C̅V̅) value indicated SSSAB was more stable than the UASBR.

Simulation of the transfer and fate of γ-HCH in epikarst system.

The thin surface soil layer and karst features in karst terrains lead to poor filtration, poor pre-purification and rapid infiltration, so that karst groundwater systems are particularly vulnerable to contamination. Due to its extensive use in past, gamma-hexachlorocyclohexane (γ-HCH) is ubiquitous in various environmental compartments of China, even though it has been prohibited since 1984. However, very little is known about its movement and behavior in special karst system. In this study, a dynamic fugacity model was established for γ-HCH in epikarst system via dividing the karst soil into multiple layers coupled with the physical-chemical properties of γ-HCH. The simulated results in soil profile were in good agreement with the measured values of γ-HCH. The modeled results predict that only 18 g γ-HCH will be left in the studied area in 2020, which is only 0.4% of the largest reserves in 1983, and about 99.99% of γ-HCH will remains in soil. The concentrations of γ-HCH in air, plant and 0-20 cm layer soil in the studied area descended quickly after HCHs was prohibited in 1984, while its concentration in soil layer deeper than 20 cm (deeper soil) increased continuously till 1997. The dominant transfer process of γ-HCH between the adjacent compartments in the studied area was from 0-20 cm layer to the deeper soil. Sensitivity analysis results showed that emission rate, infiltration coefficient, total organic carbon of soil, degradation rate in soil, compartment area and volume were the top six influential parameters for predicting γ-HCH concentration.

Rheological behaviors of anaerobic granular sludge in a spiral symmetry stream anaerobic bioreactor.

The rheological behaviors of the anaerobic granular sludge (AGS) in a spiral symmetry stream anaerobic bioreactor (SSSAB) were investigated. Shear-thinning behavior, thixotropic behavior, concentration-viscosity behavior and temperature-viscosity behavior were evaluated based on the constitutive equation of the AGS. The results indicated that the Herschel-Bulkley model was able to adequately describe the constitutive relation of AGS in the SSSAB. The AGS also showed shear-thinning behavior as well as thixotropic behavior. The critical shear rate and network strength of the AGS were 61.8 s(-1) and 497.0 W m(-3), respectively. The relationship between the apparent viscosity and the sludge concentration was illustrated and explained by the Woodcock formula. The relationship between apparent viscosity of the AGS and temperature could be modeled using the Arrhenius equation. The AGS was significantly thermo-sensitive and its mean energy of activation was 14.640 kJ mol(-1). Notably, it was necessary to consider such behaviors in the hydrodynamic modeling of SSSAB in which shear condition, sludge concentration and temperature were in non-uniform distribution.

Bottom-up approach for the reaction of xenobiotics and their metabolites with model substances for natural organic matter by electrochemistry-mass spectrometry (EC-MS).

Risk assessment of xenobiotics requires a comprehensive understanding of their transformation in the environment. As most of the transformation processes usually involve a redox reaction or a hydrolysis as the first steps of the transformation, we applied an approach that uses an electrochemical cell to investigate model "redox" reactions in aqueous solutions for environmental processes. We investigated the degradation of a variety of xenobiotics from polar to nonpolar and analyzed their degradation products by on-line coupling of electrochemistry with mass spectrometry (EC-MS). Furthermore, we evaluated possible binding reactions with regard to the generation of non-extractable residues with some model substances (catechol, phthalic acid, γ-L-Glutamyl-L-cysteinyl-glycine (GSH) and L-histidine) deduced from a natural organic matter (NOM) structure model and identified possible binding-sites. Whereas typically investigations in soil/water-systems have been applied, we used to our knowledge for the first time a bottom-up approach, starting from the chemicals of interest and different model substances for natural organic matter to evaluate chemical binding mechanisms (or processes) in the EC-MS under redox conditions. Under oxidative conditions, bindings of the xenobiotics with catechol, GSH and histidine were found, but no reactions with the model compound phthalic acid were observed. In general, no chemical binding has yet been found under reductive conditions. In some cases (i.e. benzo[a]anthracene) the oxidation product only underwent a binding reaction, whereas the xenobiotic itself did not undergo any reactions. EC-MS is a promising fast and simple screening method to investigate the environmental behavior of xenobiotics and to evaluate the potential risks of newly synthesized substances.

Oxidation of acidic dye Eosin Y by the solar photo-Fenton processes.

Oxidation of acidic dye Eosin Y has been investigated with Fenton process and photo-Fenton process (solar light or artificial light source). With UV-Fenton process and Fenton, 42.5% and 21.3% of dye could be removed from the water, respectively. However, 94.1% of dye was removed in solar-Fenton in 90min. Based on solar-Fenton process, the effect of pH value and the concentration of dye, Fe(2+), H(2)O(2) as well as oxalic acid concentration on Eosin Y degradation efficiency were investigated. In 60min, 96% of Eosin Y was degraded when the pH value was 3.5 and the concentration of Fe(2+), H(2)O(2) and oxalic acid was 10mol/L, 600mg/L and 300mg/L, respectively. The Eosin Y degradation was dependent on the dye concentration. That is higher Eosin Y concentration resulted in lower degradation efficiency. Under the conditions of pH 3.5, the Eosin Y apparent kinetics equation was -dC/dt=0.000249[Eosin Y](0.78)[Fe(2+)](1.14)[H(2)O(2)](1.26). Meanwhile, this research also proved that oxalic acid could improve the photocatalytic efficiency in the solar-Fenton process.

[Photo-fenton oxidation processes used in the degradation of rhodamine B].

Photo-Fenton method, the combination of Fenton reagent with light, is an efficient method for waste water treatment. In this paper, the degradation of rhodamine B (a kind of organic dye) using this method was researched. Through numerous experiments, the influences of five parameters including light source, pH, reaction time, dosage of Fenton reagent, and initial dye concentration were investigated intensively. In this paper, the mechanisms of this reaction have also been probed. It is concluded from the experiments that the irradiations of 450 W high-pressure mercury lamp and sun light can both accelerate the process of degradation effectively. Under optimal conditions, the overall color removal was more than 99.9% within 45 min; COD can be removed effectively at the same time.