Large-scale soil application of hydrochar: Reducing its polycyclic aromatic hydrocarbon content and toxicity by heating.

The beneficial roles of hydrochar in carbon sequestration and soil improvement are widely accepted. Despite few available reports regarding polycyclic aromatic hydrocarbons (PAHs) generated during preparation, their potential negative impacts on ecosystems remain a concern. A heating treatment method was employed in this study for rapidly removing PAHs and reducing the toxicity of corn stover-based hydrochar (CHC). The result showed total PAHs content (∑PAH) decreased and then sharply increased within the temperature range from 150 °C to 400 °C. The ∑PAH and related toxicity in CHC decreased by more than 80% under 200 °C heating temperature, compared with those in the untreated sample, representing the lowest microbial toxicity. Benzo(a)pyrene produced a significant influence on the ecological toxicity of the hydrochar among the 16 types of PAHs. The impact of thermal treatment on the composition, content, and toxicity of PAHs was significantly influenced by the adsorption, migration, and desorption of PAHs within hydrochar pores, as well as the disintegration and aggregation of large molecular polymers. The combination of hydrochar with carbonized waste heat and exhaust gas collection could be a promising method to efficiently and affordably reduce hydrochar ecological toxicity.

Liquid-solid ratio during hydrothermal carbonization affects hydrochar application potential in soil: Based on characteristics comparison and economic benefit analysis.

Returning straw-like agricultural waste to the field by converting it into hydrochar through hydrothermal carbonization (HTC) is an important way to realize resource utilization of waste, soil improvement, and carbon sequestration. However, the large-scale HTC is highly limited by the large water consumption and waste liquid pollution. Here, we propose strategies to optimize the liquid-solid ratio (LSR) of HTC, and comprehensively evaluate the stability, soil application potential, and economic benefits of corn stover-based hydrochar under different LSRs. The results showed that the total amount of dissolved organic carbon of hydrochars increased by 55.0% as LSR reducing from 10:1 to 2:1, while the element content, thermal stability, carbon fixation potential, specific surface area, pore volume, and functional group type were not obviously affected. The specific surface area and pore volume of hydrochar decreased by 61.8% and 70.9% as LSR reduced to 1:1, due to incomplete carbonization. According to the gray relation, hydrochar derived at LSR of 10:1 and followed by 2:1 showed greatest relation degree of 0.80 and 0.70, respectively, indicating better soil application potential. However, reducing LSR from 10:1 to 2:1 made the income of single process production increased from -388 to 968 ¥, and the wastewater generation decreased by 80%. Considering the large-scale application of HTC in fields for farmland improvement and environmental remediation, the comprehensive advantages of optimized LSR will be further highlighted.

Fabrication of Anatase TiO2/PVDF Composite Membrane for Oil-in-Water Emulsion Separation and Dye Photocatalytic Degradation.

At present, the types of pollutants in wastewater are more and more complicated, however, the multifunctional membrane materials are in short supply. To prepare a membrane with both high efficient oil-in-water emulsion separation performance and photocatalytic degradation performance of organic dyes, the bifunctional separation membrane was successfully prepared by electrostatic spinning technology of PVDF/PEMA and in situ deposition of anatase TiO2 nanoparticles containing Ti3+ and oxygen vacancies (Ov). The prepared composite membrane has excellent hydrophilic properties (WCA = 15.65), underwater oleophobic properties (UOCA = 156.69), and photocatalytic performance. These composite membranes have high separation efficiency and outstanding anti-fouling performance, the oil removal efficiency reaches 98.95%, and the flux recovery rate (FRR) reaches 99.19% for soybean oil-in-water emulsion. In addition, the composite membrane has outstanding photocatalytic degradation performance, with 97% and 90.2% degradation of RhB and AG-25 under UV conditions, respectively. Several oil-in-water separation and dye degradation experiments show that the PVDF composite membrane has excellent reuse performance. Based on these results, this study opens new avenues for the preparation of multifunctional reusable membranes for the water treatment field.

[Analysis of fungal diversity in intestines of Hepialus gonggaensis larvae].

OBJECTIVE: Studied fungi diversity in the guts of larval Hepialus gonggaensis using culture-independent and traditional culturing methods. METHODS: For the culture-independent method, the total DNA of fungus was extracted from the intestinal contents and internal transcribed spacer (ITS) regions were amplified with fungal universal primers. A near-full length ITS gene library was constructed. Subsequently, the fingerprints of the microorganisms were analyzed by isolated plasmid and digestion with Msp I, HaeIII and Taq I enzymes, respectively. Restriction fragment length polymorphism (RFLP) analysis based on the fungal ITS sequences indicated that the library established includes 23 operational taxonomic units (OTUS) and a phylogenetic tree depicted the linkage of the isolated fungi. RESULTS: Abundant fungi were in the intestines of H. gonggaensis larvae, but their abundance was very different. The dominant fungi belonged to Mortierellaone and Trichosporon and accounted for 46.34 % and 39.02 % of the total ITS clones, respectively. Only three genera of fungi were identified from eight isolated fungal populations by traditional culturing methods. CONCLUSION: We could get more information by combined traditional culturing and molecular biology methods.

[Analysis of the bacterial diversity in intestines of Hepialus gonggaensis larvae].

OBJECTIVE: We investigated the intestinal microbial diversity in the larval gut of Hepialus gonggaensis, an economically important insect. METHODS: We used morphological, physiological, chemotaxonomic characteristics and 16S rRNA analysis method, and the molecular method of PCR-DGGE (denaturing gradient gel electrophoresis) analysis based on the sequence of 16S rRNA V3 region gene. RESULTS: By the traditional isolation method, 8 genera of bacteria were identified from 11 isolated bacterial populations. The dominant bacteria in intestine belonged to enterobacter. By 16S rRNA V3 region gene DGGE method, eleven distinct bands were obtained from 16S rDNA amplificons. The bands were purified, sequenced. The sequences aligned with GenBank database and showed that they were belonged to 8 different genera of bacteria. Phylogenetic analysis showed that the sequences of bacteria belonged to the Proteobacteria and Firmicutes. The most dominant bacteria group was Carnobacterium in the gut and Bacillus followed by it. The different patterns were observed in different instars larvae guts from DGGE profiles, which might be related to their physiological development stages. CONCLUSION: 8 genera were obtained from intestine of H. gonggaensis by traditional culturing method and 16S rDNA analysis method respectively, but the two groups were not exactly same, and the dominant group was different also. This suggested that a combination of molecular and traditional culturing methods can be used to analyze and monitor the diversity of intestinal microflora effectively, and that will give us more information of microorganism diversity.

Analysis of the intestinal microflora in Hepialus gonggaensis larvae Using 16S rRNA sequences.

Gut microbial diversity provides insight into the basic function of a gut microbial ecosystem. In this study, restriction fragment length polymorphism 16S rRNA sequences was used to detect the intestinal microbial diversity of Hepialus gonggaensis larvae. The total DNA of microorganisms was extracted from the intestinal contents and 16S rRNA was amplified. A nearly full-length of 16S rRNA sequence library was constructed. The fingerprints of the microorganisms were analyzed by isolating plasmid and then digesting them with EcoRI, MspI, and HaeIII enzymes, respectively. The library established includes 35 restriction endonuclease types and a phylogenetic tree depicted the linkage of the isolated microbial from the guts of H. gonggaensis larvae. The dominant bacteria in the guts of H. gonggaensis larvae belong to Rahnella sp and Carnobacterium sp and accounted for 45.58% and 30.88% of the total 16S rRNA clones library, respectively. The result showed that bacteria diversity in the guts of H. gonggaensis larvae had some differences from those isolated from normal environment.