The catalytic behavior of H-ZSM-5 and Zn/H-ZSM-5 for the aromatization of dimethyl ether (DME) was investigated. The increase in the number and strength of acid sites on the H-ZSM-5 zeolite was ...beneficial for DME aromatization. Aromatization performance was enhanced by loading Zn into H-ZSM-5. The yields of total and C
8 aromatics over H-ZSM-5 at 360 °C were 50.0% and 28.6%, respectively, and over Zn/H-ZSM-5 (Zn 2% in mass) were 66.2% and 39.0%, respectively. At 480 °C, the total aromatics yield increased to 78.0% over Zn/H-ZSM-5.
考察了䜕H-ZSM-5䜕和䜕Zn/H-ZSM-5䜕催化剂的二甲醚芳构化性能.䜕䜕结果表明,䜕H-ZSM-5䜕分子筛催化剂酸性的增强和酸中心的增多有利于二甲醚芳构化.䜕䜕当在䜕H-ZSM-5䜕催化剂中加入䜕2%䜕Zn䜕时,䜕在䜕䜕°C䜕下反应时总芳烃收率从䜕50.0%䜕增加至䜕66.2%,䜕C
8䜕芳烃收率从䜕28.6%䜕增加到䜕39.0%.䜕䜕反应温度升高到䜕480䜕°C䜕时,䜕总芳烃收率增加至䜕78.0%.䜕
Dimethyl ether can be effectively converted into aromatics over a Zn/H-ZSM-5 catalyst, and a high yield of C8 aromatics is achieved. The aromatization performance was affected by SiO
2/Al
2O
3 ratio, Zn amount, and reaction temperature.
•The experiment was conducted in the fish matrix.•A. sobria showed the highest proteolytic activities.•Inosine nucleosidase mainly came from bacterial secretions.•A. sobria, P. helmanticensis and S. ...putrefaciens could produce inosine nucleosidase.•Xanthine oxidase came from fish muscle and bacterial secretions.
This study investigated the biochemical changes (proteins degradation, total volatile basic nitrogen, biogenic amines, volatile organic compounds, nucleotides catabolism and related enzymes) of bighead carp samples inoculated with four different bacteria (Shewanella putrefaciens, Aeromonas sobria, Acinetobacter bohemicus, and Pseudomonas helmanticensis) during storage at 4 ± 1 °C. A. sobria exhibited the strongest proteolytic activity. A. sobria, P. helmanticensis, and S. putrefaciens were responsible for putrescine production, whereas S. putrefaciens was the sole producer of cadaverine. Alcohols and S-compounds were mainly released by A. sobria and S. putrefaciens, respectively. The fastest degradation rates of hypoxanthine riboside and hypoxanthine were found in samples inoculated with P. helmanticensis and S. putrefaciens. Inosine nucleosidase was mainly resulted by A. sobria, P. helmanticensis and S. putrefaciens, whereas xanthine oxidase was derived from both fish muscle and secretions of P. helmanticensis and S. putrefaciens.
In water environment, nitrogen (N) and phosphorus (P) are biochemically dependent nutrients following the co-limitation concept for algae growth under mixotrophic mode. From a practical viewpoint, ...algae growth may not bring about significant change of the background nutrient concentration of an actual waterbody in contrast to a conventional batch system. In order to better understand the growth pattern of microalgae in aquatic environments, a series of experiments were conducted under stably controlled N-P levels for studying the N-P coupling effect on mixotrophic Chlorella vulgaris growth process, with attention paid to the physiological and biochemical characteristics. It was found that within the concentration range of N = 1–8 mg·L−1 and P = 0.1–1.0 mg·L−1, the variation of the N-P level slightly affected the specific growth rate, but significantly influenced nutrients uptake, biomass dry weight, chlorophyll contents of the grown C. vulgaris. The biochemical and elemental composition of the microalgae tended to be more sensitive to the N-P concentrations and ratios in the lower nutrient range (1–2 mg N·L−1, 0.1–0.4 mg P·L−1) in which the highest N and P conversion rates were gained as 90.18 ± 1.23% and 60.47 ± 1.59%, respectively. The P assimilation and conversion efficiencies were much affected by both N and P supplies, while the P supply showed little influence on N assimilation and conversion efficiencies. It was also noticed that the N level greatly affected the metabolic pathway involving nutrient assimilation, carbohydrate fixation and monosaccharide profile, resulting in conversion of the dominant fraction of protein at N ≤ 2 mg·L−1 into other biochemical compositions including lipids at N ≥ 3 mg·L−1. The fatty acid methyl esters (FAMEs) composition tended to differ with varied nutrient levels. These findings may deepen our understanding of algal growth in aquatic environment and provide perspective for eutrophication control.
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•Mixotrophic C. vulgaris cultivation was conducted at stably controlled N-P levels.•N-P coupling effect was significant on algal nutrient uptake, dry mass and pigments.•Physiological and biochemical properties of algae varied greatly in lower N-P range•Algal metabolic pathway was more strongly influenced by nitrogen than phosphorus.
•Glucose was used as external carbon to investigate its effect on C. vulgaris growth.•External carbon increased algal growth rate but reduced its carbon fixation ability.•Anabolism and catabolism ...might be the main reason for lower carbon fixation.•External carbon reduced the algal dry weights and chlorophyll contents.•External carbon enhanced algal N/P accumulation and nutrient conversion rate.
Water eutrophication may be affected not only by nutrients but also the coexisting organic carbon. In order to reveal the effect of external carbon on algal growth, an experimental study was conducted using Chlorella vulgaris as the representative microalgae to investigate their growth under varied N and P levels with/without added glucose at TOC = 18 mg/L. The TOC consumption by microalgae growth depended much on N and P concentrations and N/P ratio especially when P was sufficient. This ultimately increased the specific growth rate and resulted in higher N and P accumulations but lower carbon fixation in algal biomass in contrast to non-TOC addition. The biomass dry weight became much lower with TOC addition, along with an apparent change of algal composition shown by the much lower chlorophyll contents in the microalgae cells, which might associate the extent of two carbon fixation pathways – anabolism vs catabolism.
•Thermophilic fermentation slurry from food waste was used as carbon source.•Nitrogen and phosphate removal rate was promoted with FSFW.•SND and denitrifying phosphate accumulation process were ...observed with FSFW.•Microbial community structure with FSFW addition was studied.
Enhancement of nitrogen and phosphate removal using thermophilic fermentation slurry from food waste (FSFW) as external carbon source was investigated. Based on the batch tests, the soluble and particulate fractions of the FSFW acted as easily and slowly biodegradable carbon sources, respectively, and the fermented slurry showed the combined nutrients removal properties of soluble and solid organics. During the long-term operation of a sequencing batch reactor (SBR) with FSFW for wastewater treatment, the sludge particle size increased obviously, the bacterial metabolic capacity improved significantly, and some functional microorganisms were enriched selectively, which significantly promoted the nitrogen removal efficiency (approximately 90%) by enhancing the anoxic denitrification and simultaneous nitrification and denitrification (SND) processes. Moreover, high phosphate removal efficiency (above 98%) was achieved through the aerobic and anoxic phosphate accumulation processes. Thus, using the FSFW as supplementary carbon source is a suitable solution for both food waste disposal and wastewater treatment.
Antimicrobial and antioxidant effects of essential oils (oregano, thyme, and star anise) on microbial composition and quality of grass carp fillets were investigated. Essential oils treatment was ...found to be effective in inhibiting microbial growth, delaying lipid oxidation, and retarding the increase of TVB-N, putrescine, hypoxanthine, and K-value. Based on sensory analysis, shelf-life of grass carp fillets was 6days for control and 8days for treatment groups. Among the essential oils, oregano essential oil exhibited the highest antimicrobial and antioxidant activities. GC-MS analysis of essential oils components revealed that carvacrol (88.64%) was the major component of oregano essential oil. According to the results of high-throughput sequencing, Aeromonas, Glutamicibacter, and Aequorivita were the predominant microbiota in fresh control samples. However, oregano essential oil decreased the relative abundance of Aeromonas, while thyme and star anise essential oils decreased the relative abundance of Glutamicibacter and Aequorivita in fresh treated samples. The microbial composition of both control and treatment groups became less diverse as storage time increased. Aeromonas and Pseudomonas were dominant in spoiled samples and contributed to fish spoilage. Compared to the control, essential oils effectively inhibited the growth of Aeromonas and Shewanella in grass carp fillets during chilled storage.
•High-throughput sequencing was used to assay microbial composition of fish flesh.•Essential oils delayed the increase of TBA, TVB-N, putrescine, and hypoxanthine.•Aeromonas and Pseudomonas were dominant in spoiled grass carp fillets.•Essential oils treatment inhibited the growth of Aeromonas and Shewanella.•Oregano essential oil was recommended to use in grass carp fillets.
Understanding of the impacts of key influential factors on RDS related heavy metal (HM) contamination is crucial for developing effective RDS management strategies to support the stormwater pollution ...mitigation. In this paper, three factors (i.e. traffic condition, slope of road and antecedent dry period) were considered to investigate their influences on the accumulation of RDS and adsorbed HMs. Positive correlations between truck and Zn/Ni content in RDS, car and Cu/Pb content in fine RDS, as well as bus and Cu content in coarse RDS were observed. Relative to sloping stretches, RDS from level stretches generally presented finer size distributions and aggravated HM contamination in fine fractions. Moreover, the fine RDS and adsorbed HMs increased significantly with the accumulation of RDS. Based on these findings, optimized RDS management strategies were proposed to enhance the removal of washable RDS in pollution hotspots. For example, tandem sweeping technologies, performing high efficiency in capturing fine particles, are suggested to be employed during the steady period of RDS accumulation, in order to reduce fine RDS effectively. The outcomes of this study provide useful reference for the source control of stormwater runoff pollution.
•Vehicles of different types were indicative of specific HM contamination.•RDS on level stretches showed heavier HM contamination.•RDS presented aggravated HM contamination during the steady period of accumulation.•Optimized RDS management strategies were proposed.
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•CoxFe3−xO4 catalysts are synthesized via a series of CoωFe3−ω-MOFs sacrificial template.•Mesopore significantly affected the Oxone activation performance to eliminate bisphenol ...A.•B-site cobalt in mixed spinel CoxFe3−xO4 was evidenced to trigger the catalytic process.
We report a facile process to fabricate porous CoxFe3−xO4 catalysts by using a metal organic framework (MOFs) sacrificial template for bisphenol A (BPA) degradation through Oxone activation. The results demonstrated a significantly enhanced catalytic performance with increasing content of cobalt in the catalyst, which peaked at x = 1.51. Further increase in the cobalt content of catalysts exhibited negative effects on the catalytic performance due to the increased cobalt-rich phase with insufficient Fe. The effects of various conditions were evaluated, circa 0.13 (0.20) min−1 of the catalytic rate could be attained in deionized water (reaction condition: BPA = 60 μM, Oxone concentration = 0.6 mM, catalyst dosage = 0.1 (0.3) g L−1, temperature = 25 °C, and initial pH = 10.2 (6.5)). The radical SO4− was demonstrated to be a major contributor to the catalytic process, as well as HO. More importantly, the catalysts exhibited desirable BPA degradation efficiencies in various water matrices. Simple thermal treatment at 450 °C in open air significantly regenerated the spent catalyst. B-site cobalt in catalysts was proved to play an important role in activating Oxone in the proposed mechanism.
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•Food waste fermentation without inoculum under different pH was investigated.•Hydrolysis and acidogenesis processes were promoted with the increase of pH.•Caproic acid was produced ...at pH 6 through lactate-based chain elongation.•Functional microbial communities were orientationally enriched during fermentation.
Caproic acid (CA) production from food waste (FW) is a promising way for waste recycling, while the fermentation processes need further exploration. In this study, FW acidogenic fermentation under different pH (uncontrolled, 4, 5, 6) using indigenous microbiota was investigated. Result showed that substrate hydrolysis, carbohydrate degradation and acidogenesis increased with the increase of pH. Although various microbial communities were observed in FW, lactic acid bacteria (Lactobacillus and Limosilactobacillus) were enriched at pH lower than 6, resulting in lactic acid accumulation. CA (88.24 mM) was produced at pH 6 accounting for 31.23% of the total product carbon. The enriched lactic acid bacteria were directionally replaced by chain elongators (Caproicibacter, Clostridium_sensu_stricto, unclassified_Ruminococcaceae) at pH 6, and carbohydrates in FW were firstly transformed into lactic acid, then to butyrate and CA through lactate-based chain elongation processes. This work provided a novel CA fermentation pathway and further enriched the FW valorization.
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