摘要 : Stable carbon release and coupled microbial efficacy of external carbon source solid fillers are the keys to enhanced nitrogen removal in constructed wetlands. The constructed wetland plant residue Acorus calamus was cross-linked with poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) to create composite solid carbon source fillers (Ac-BDPs). The study demonstrated the slow release of carbon sources from Ac-BDPs with 35.27 mg/g under an average release rate of 0.88 mg/(g·d). Excellent denitrification was also observed in constructed wetlands with Ac-BDPs. Moreover, the average removal rate of nitrate nitrogen (NO 3 − -N) was increased by 1.94 and 3.85 times of the blank groups under initial NO 3 − -N inputs of 5 and 15 mg/L, respectively. Furthermore, the relatively high abundances of nap, narG, nirKS, norB, qnorZ and nosZ guaranteed efficient denitrification performance in constructed wetlands with Ac-BDPs. The study introduced a reliable technique for biological nitrogen removal by using composite carbon source fillers in constructed wetlands.

摘要 : In this study, a nitrogen/oxygen co-doped carbon fiber cloth with a hierarchical porous structure was synthesized by one-step carbonization and in situ activation method and acted as binder-free electrode materials for supercapacitors. Cotton fiber cloth served as the carbon precursor, while molecular dispersed CaCl 2 ·6H 2 O and urea functioned as activator and N dopant, respectively. The influence of molar concentration of CaCl 2 ·6H 2 O and urea on the microstructure and capacitive performance of the resulting products were investigated. CaCl 2 ·6H 2 O has an expansion effect on pores, resulting in reduction of micropores. Hence, the specific surface area of the resulting porous carbon increased first and then decreased with the increase of CaCl 2 ·6H 2 O concentration. In addition, the erosion of NH 3 and CO 2 (produced by the decomposition of urea) at high temperature on the surface of the samples promoted the formation of porous structure. Urea plays the dual role of doping and activation agent. The morphology and structure analysis shown that the activated samples exhibited hierarchical pore structure, large specific surface area, and high heteroatom content. The optimal sample NAC-20 exhibited good capacitive performance, including high specific capacitance of 260.9 F g −1 at 0.1 A g −1 and good rate performance. Moreover, the symmetric supercapacitor exhibited a maximum energy density and power density of 16.2 Wh kg −1 and 19.0 kW kg −1, respectively, in 6 M KOH electrolyte. In this work, a green, low-cost molten salt activation method was proposed to synthesis biomass derived porous carbon materials for energy storage devices.

摘要 : TC4 titanium alloy is utilized in aerospace and a wide range of other applications due to its high strength and corrosion resistance, but its poor thermal conductivity and high ductility introduce challenges in machining. In this paper, firstly, a mathematical model of workpiece surface morphology under tilted ultrasonic elliptical vibration cutting (TUEVC) was established based on the tip trajectory and material removal mechanism, and the variation of workpiece surface morphology was investigated at different tool tilt angles θ, and it was found that the tilt θ in a certain range could significantly reduce the surface residual height compared with that of ordinary ultrasonic elliptical vibration cutting (UEVC). Second, the TUEVC experiment of TC4 titanium alloy was carried out to comparatively analyze the changes in the surface morphology, surface profile, and surface roughness of the workpiece under different tilt θ, the effect of each machining parameter (cutting speed, feed, and ultrasonic amplitude) on surface roughness was explored. The experimental results indicate that as the tilt θ changes from 0° to 90° throughout the process, the workpiece surface morphology flatness decreases and then increases. When the tilt angle θ is 45°, workpiece cutting surface roughness is minimized ( Sa = 0.157), compared with the ordinary ultrasonic elliptical vibration cutting roughness is reduced by 47.6 % maximum. Both the surface morphology flatness and the surface roughness of the workpiece are at their smallest, whereas the theoretical profile curve and cutting surface profile curve are at their most consistent. Under the same machining parameters, TUEVC can reduce the surface roughness more effectively compared with UEVC, this technique reduces surface roughness by 16 %, 23 %, and 26 % at maximum for different cutting speeds, feeds, and ultrasonic amplitudes, respectively.

摘要 : Per- and polyfluoroalkyl substances (PFAS) have already drawn a lot of attention for their accumulation and reproductive toxicity in organisms. Perfluorooctanoic acid (PFOA) and perfluorooctanoic sulfonate (PFOS), two representative PFAS, are toxic to humans and animals. Due to their widespread use in environmental media with multiple toxicities, PFOA and PFOS have been banned in numerous countries, and many substitutes have been produced to meet market requirements. Unfortunately, most alternatives to PFOA and PFOS have proven to be cumulative and highly toxic. Of the reported multiple organ toxicities, reproductive toxicity deserves special attention. It has been confirmed through epidemiological studies that PFOS and PFOA are not only associated with reduced testosterone levels in humans, but also with an association with damage to the integrity of the blood testicular barrier. In addition, for women, PFOA and PFOS are correlated with abnormal sex hormone levels, and increase the risk of infertility and abnormal menstrual cycle. Nevertheless, there is controversial evidence on the epidemiological relationship that exists between PFOA and PFOS as well as sperm quality and reproductive hormones, while the evidence from animal studies is relatively consistent. Based on the published papers, the potential toxicity mechanisms for PFOA, PFOS and their substitutes were reviewed. For males, PFOA and PFOS may produce reproductive toxicity in the following five ways: (1) Apoptosis and autophagy in spermatogenic cells; (2) Apoptosis and differentiation disorders of Leydig cells; (3) Oxidative stress in sperm and disturbance of Ca 2+ channels in sperm membrane; (4) Degradation of delicate intercellular junctions between Sertoli cells; (5) Activation of brain nuclei and shift of hypothalamic metabolome. For females, PFOA and PFOS may produce reproductive toxicity in the following five ways: (1) Damage to oocytes through oxidative stress; (2) Inhibition of corpus luteum function; (3) Inhibition of steroid hormone synthesis; (4) Damage to follicles by affecting gap junction intercellular communication (GJIC); (5) Inhibition of placental function. Besides, PFAS substitutes show similar reproductive toxicity with PFOA and PFOS, and are even more toxic to the placenta. Finally, based on the existing knowledge, future developments and direction of efforts in this field are suggested.

摘要 : The adsorption and utilization of Fe(III) can be impeded by precipitation in anaerobic reactors. In this study, we investigated whether the bioavailability of Fe(III) can be enhanced by EDTA-Fe(III), thereby improving the stability of anammox system. Fe(III) and EDTA-Fe(III) were added to two parallel up-flow anaerobic sludge blanket (UASB) reactors, respectively. After 186 days of operation, when the nitrogen loading rate (NLR) was 0.8 g-N/L/d, the nitrogen removal rate (NRR) of R2 was stable at 0.675 g-N/L/d, which was higher than that of R1 at 0.557 g-N/L/d. The anammox activity of R2 reached its peak in phase III (158.55 ± 4.53 mg-N/g-VSS/d), while the anammox activity of R1 was only 28.37 ± 5.96 mg-N/g-VSS/d. Moreover, in phase II-V, the bioavailability of Fe(III) in R2 was increased by 15.63%, 38.37%, 65.90%, and 39.63%, respectively, compared with R1. The results showed that EDTA-Fe(III) can prevent precipitation encasing anammox granular sludge, which can enhance substrate transport and Fe(III) adsorption utilization. High throughput sequencing suggested that EDTA-Fe(III) could better increase the abundance of anammox bacteria (AnAOB). In conclusion, this research proved that EDTA could increase the bioavailability of Fe(III) and thereby ensuring the stability of the reactors.

摘要 : The study assessed the effect of salinity and lead (Pb(II)) on the anammox sludge for nitrogen removal from saline wastewater. Results showed decreased nitrogen removal and specific anammox activity (SAA) with elevated salinity and Pb(II). SAA reduced from 541.3 ± 4.3 mg N g −1 VSS d −1 at 0.5 mg/L Pb(II) to 436.0 ± 0.2 mg N g −1 VSS d −1 at 30 g/L NaCl, further to 303.6 ± 7.1 mg N g −1 VSS d −1 under 30 g/L NaCl + 0.5 mg/L Pb(II). Notably, the combined inhibition at salinity (15–20 g/L NaCl) and Pb(II) (0.3–0.4 mg/L) exhibited synergistic effect, while higher salinity and Pb(II) aligned with independent inhibition models. Combined inhibition decreased protein/polysaccharides ratio, indicating more severe negative effect on anammox aggregation capacity. Metagenomics confirmed decreased Candidatus Kuenenia, and enhanced denitrification under elevated salinity and Pb(II) conditions. This study offers insights into anammox operation for treating saline wastewater with heavy metals.

摘要 : Microplastics (MPs) existing extensively in various ecosystems can be ingested by marine organisms and enter the food chain, resulting the health risks from the presence of MPs in aquatic and terrestrial ecosystems. In the present study, an ideal model for Lepidoptera, the silkworm, Bombyx mori, was exposed to environmental concentrations (0.125 μg, 0.25 μg or 0.5 μg/diet) of MPs for 5 days, and the global changes in gut microbes and metabolites were subsequently examined via 16S rDNA sequencing and GC‒MS-based metabolomics. The results showed that MPs exposure did not seriously threaten survival but may regulate signaling pathways involved in development and cocoon production. MPs exposure induced gut microbiota perturbation according to the indices of α-diversity and β-diversity, and the functional prediction of the altered microbiome and associated metabolites demonstrated the potential roles of the altered microbiome following MPs exposure in the metabolic and physiological states of silkworm. The metabolites markedly altered following MPs exposure may play vital biological roles in energy metabolism, lipid metabolism, xenobiotic detoxification and the immune system by directly or indirectly affecting the physiological state of silkworms. These findings contribute to assessing the health risks of MPs exposure in model insects and provide novel insight into the toxicity mechanism of MPs.

摘要 : Pumped two-phase loop integrated with thermal storage is an emerging solution for the short-term high-heat-flux cooling. The transient microchannel boiling heat transfer of pumped two-phase loop (PTL) integrated with latent heat storage (LHS) under step heat load are experimentally investigated, with special focuses on dynamic thermal response of two-phase loop and latent heat storage unit. The transient thermal behaviors of PTL-LHS are determined based on the wide variations of heat load and flow rate. A thermal behavior regime diagram is proposed to quantitatively recognize the transient thermal response of PTL-LHS, depending on the heat load and flow rate. The results indicate that the fast tracking mode and the delay response mode are observed and sequentially experienced for PTL-LHS as the step heat load increases. With respect to delay response mode, thermal storage efficiency is high with short thermal storage duration but cooling performance is insufficient, while the transient thermal performances are contrary under the fast tracking mode. The increase of heat load accelerates the transformation of the heat transfer mechanism in LHS from sensitive-heat-dominated to latent-heat-dominated, while increasing flow rate is conducive for the enhancements of thermal capacity and thermal stability of PTL-LHS. Increasing heat load brings about a larger critical flow rate of the transient thermal behavior regime transition, and hence the range of flow rate tends to be larger for the delay response mode. Particularly, the proposed variable flow rate optimization strategy is validated by comparative experiments, showing better cooling performance (the average evaporator wall temperature decreases by 10 °C) and more remaining load of phase change material.

摘要 : The prevention of material leakage and improvement of thermal conductivity are very important for thermal energy storage application. In this work, nano-TiO 2 @ n -docosane microcapsules were synthesized by the fine emulsion interface polymerization method using tetra- n -butyl titanate (TBT). This approach enhances the encapsulation rate and efficiency of phase change microcapsules. The microcapsules formation process was observed using a biological microscope. The diameter of the microcapsules decreased significantly with the increase of stirring rate. The phase transition temperature of the optimal microcapsules is 42.4 °C. The encapsulation rate and efficiency reach up to 90.7% and 91.0%, respectively. The average thermal conductivity of nano-TiO 2 @ n -docosane microcapsules is 215% higher than that of n -docosane. SEM and infrared spectroscopy testing results confirm the successful coating of n -docosane by TiO 2 . Thermogravimetric analysis presents that TiO 2 forms a shell, which reduces the leakage of n -docosane. The melting and solidification processes of n -docosane and nano-TiO 2 @ n -docosane microcapsules were simulated numerically. In comparison to n -docosane, nano-TiO 2 @ n -docosane microcapsules exhibit a 14.89% increase in peak storage power and a 12.47% increase in heat transfer coefficient during charging. Additionally, during discharging, these values rise by 3.23% and 6.46%, respectively. Nano-TiO 2 @ n -docosane microcapsules enhance heat transfer and the charging/discharging process of phase change materials.

摘要 : In this study, a pilot-scale anaerobic membrane bioreactor (AnMBR) was developed to continuously produce volatile fatty acids (VFAs) from kitchen waste slurry under an alkaline condition. The alkaline fermentation effectively suppressed methanogenesis, thus achieving high VFAs production of 60.3 g/L. Acetic acid, propionic acid, and butyric acid accounted for over 95.0 % of the total VFAs. The VFAs yield, productivity, and chemical oxygen demand (COD) recovery efficiency reached 0.5 g/g-COD influent, 6.0 kg/m 3 /d, and 62.8 %, respectively. Moreover, the COD VFAs /COD effluent ratio exceeded 96.0 %, and the COD VFAs /NH 3 -N ratio through ammonia distillation reached up to 192.5. The microbial community was reshaped during the alkaline fermentation with increasing salinity. The membrane fouling of the AnMBR was alleviated by chemical cleaning and sludge discharge, and membrane modules displayed a sustained filtration performance. In conclusion, this study demonstrated that high-quality VFAs could be efficiently produced from kitchen waste slurry using an AnMBR process via alkaline fermentation.