Na3V2(PO4)3-decorated Na3V2(PO4)2F3 as a high-rate and cycle-stable cathode material for sodium ion batteries.

Since Na3V2(PO4)3 (NVP) possesses modest volume deformation and three-dimensional ion diffusion channels, it is a potential sodium-ion battery cathode material that has been extensively researched. Nonetheless, NVP still endures the consequences of poor electronic conductivity and low voltage platforms, which need to be further improved. On this basis, a high voltage platform Na3V2(PO4)2F3 was introduced to form a composite with NVP to increase the energy density. In this study, the sol-gel technique was successfully used to synthesize a Na3V2(PO4)2.75F0.75/C (NVPF·3NVP/C) composite cathode material. The citric acid-derived carbon layer was utilized to construct three-dimensional conducting networks to effectively promote ion and electron diffusion. Furthermore, the composites' synergistic effect accelerates the quick ionic migration and improves the kinetic reaction. In particular, NVP as the dominant phase enhanced the structural stability and significantly increased the capacitive contribution. Therefore, at 0.1C, the discharge capacity of the modified NVPF·3NVP/C composite is 120.7 mA h g-1, which is greater than the theoretical discharge capacity of pure NVP (118 mA h g-1). It discharged 110.9 mA h g-1 of reversible capacity even at an elevated multiplicity of 10C, and after 200 cycles, it retained 64.1% of its capacity. Thus, the effort produced an optimized NVPF·3NVP/C composite cathode material that may be used in the sodium ion cathode.

[Occurrence of Antibiotic Resistance Genes and Bacterial Community Structure of Different Sludge Samples During Microwave Pretreatment-Anaerobic Digestion].

The waste sludge of municipal wastewater treatment plants is an important reservoir for antibiotic resistance genes (ARG). It is necessary to explore the fate of ARG, microbial community succession, and the correlations between them. Therefore, the distribution of ARG and the microbial community structure of waste sludge from wastewater treatment plants with A2O and A2O-MBR processes during microwave pretreatment and anaerobic digestion were studied in this research. The results showed that the occurrence of ARG and the microbial community structure were quite different in the waste sludge of A2O and A2O-MBR processes. The microwave pretreatment did not change the microbial community much, whereas the community structure of the digested sludge with pretreatment showed significant differences. Anaerobic digestion had a conformity effect on the distribution of ARG and MGE in the digested sludge with or without pretreatment. Among genes, ermF, qnrS, and blaNDM-1 were the most difficult to be reduced ARG and were prone to propagation during anaerobic digestion. The influence of biomass, ammonia nitrogen, and phosphorus on the distribution of ARG and MGE was higher than that of other environmental factors. The sludge characteristics also showed important impacts on the microbial community, especially on some genera with specific functions. These results could help people to better understand the spread and control of ARG during sludge anaerobic digestion.

[Impacts of Sludge Characteristics on Anaerobic Digestion with Microwave Pretreatment and Archaeal Community Structure Analysis].

Sludge characteristics is an important factor in sludge pretreatment and anaerobic digestion (AD) efficiency. Therefore, waste sludge of anaerobic-anoxic-aerobic (A2O) and A2O-membrane bioreactor (MBR) wastewater treatment processes from a full-scale wastewater treatment plant were taken, and the variations of sludge characteristics and performance during microwave pretreatment and AD were compared. The succession of archaeal community structure during the sludge treatment was also investigated. A2O waste sludge showed better biodegradability than A2O-MBR waste sludge did, with 16.4% higher organic matter content (66.4% vs. 50.0%), soluble chemical oxygen demand (COD) (1.24 fold), soluble protein (2.02 fold), and polysaccharides (4.84 fold). Although the efficiency of microwave pretreatment for A2O-MBR waste sludge was better than that for A2O waste sludge, the latter sludge produced 26.1% more methane than the former did. The two types of waste sludge showed different archaeal community structures. The abundances of Methanothrix and Methanosarcina in A2O-MBR waste sludge were 3.68% and 19.73% higher than that in A2O waste sludge. The richness and evenness of archaeal communities slightly changed after pretreatment, but significantly changed after AD. The Chao1 index increased by 54.0%-68.8% after AD, whereas the Pielou index decreased by 16.2%-34.6%. Redundancy analysis showed that the organic components of waste sludge contributed to the succession of archaeal community structure.