Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Enhanced nitrate reduction in hypotrophic waters with integrated photocatalysis and biodegradation
No full textAddressing nitrate contamination in water bodies is a critical environmental challenge, and Intimately Coupling Photocatalysis and Biodegradation (ICPB) presents a promising solution. However, there is still debate about the effectiveness of ICPB in reducing nitrate under hypotrophic conditions. Further research is needed to understand its microbial metabolic mechanism and the functional changes in bacterial structure. Here we explored microbial metabolic mechanisms and changes in bacterial structure in ICPB reactors integrating a meticulously screened TiO2/g-C3N4 photocatalyst with biofilm. We achieved a 26.3% increase in nitrate reduction using 12.2% less organic carbon compared to traditional biodegradation methods. Metagenomic analysis of the microbial communities in ICPB reactors revealed evolving metabolic pathways conducive to nitrate reduction. This research not only elucidates the photocatalytic mechanism behind nitrate reduction in hypotrophic conditions but also provides genomic insights that pave the way for alternative approaches in water remediation technologies. (c) 2024 The Authors. Published by Elsevier B.V. on behalf of Chinese Society for Environmental Sciences, Harbin Institute of Technology, Chinese Research Academy of Environmental Sciences. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Polyethylene is degraded by the deep-sea <i>Acinetobacter venetianus</i> bacterium
No full textPolyethylene is a plastic pollutant impacting marine life, calling for advanced remediation methods such as biodegradation. However, there is actually limited information on polyethylene-degrading bacteria in the marine environment. Here, we studied bacterial degradation of polyethylene and associated phthalates additives using scanning electron microscopy, Fourier transform infrared, gel permeation chromatography and genomic and transcriptomic techniques. Results show that a deep-sea bacteria, Acinetobacter venetianus F1, can degrade 12.2% of polyethylene after 56 days, following the alkane metabolic pathway. Phthalates were also degraded via the metabolic pathways of benzoic acid and phthalic acid. This is first report of polyethylene-degrading bacteria from deep-sea environments
One hundred YouthScience and Technology Plan, Guangdong University of Technology, China[263113906]
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Enhanced Catalytic Activity for Levulinic Acid Esterification Using Covalent Organic Framework Heterogenized Heteropolyacids
No full textAlkyl levulinates act as crucial additives in gasoline and biodiesel and are largely produced through esterification of levulinic acid (LA) with alcohols using homogeneous acids suffering from equipment corrosion and low reusability issues. Here, in this work, a homogeneous phosphotungstic acid (HPW) catalyst was heterogenized via incorporation on a 2D imine-based covalent organic framework material (LZU1) to obtain a heterogeneous HPW-LZU1 catalyst. The material synthesis process was comprehensively monitored through 1H NMR, solid 13C MAS NMR, ATR-FTIR, etc. When the HPW/LZU1 mass ratio was 8.6, the HPW-LZU1 catalyst exhibited an excellent catalytic activity, with >90% conversion of LA and 100% selectivity of alkyl levulinates obtained, comparable to the HPW catalyst. Catalytic performance without obvious decrease after five cycles demonstrated excellent stability and reusability of the as-prepared catalyst. In situ FTIR study shows that LA was dominantly adsorbed on the Bro''nsted acid sites, while methanol was adsorbed on the Bro''nsted and Lewis acid sites. The HPW-pi interaction-induced electron delocalization effect over the catalyst effectively enhanced the adsorption of LA and alcohols and the attack of alcohols to LA through AAc1 mechanism, attributing to the high catalytic performance of the catalyst
Study of Hydrate Particle Morphology and Cohesive Force in the Presence of Wax and Glycine
No full textDuring the operation of deep-sea pipelines, the accumulation and deposition of hydrates are important reasons for pipeline blockage. The current main measure to solve the hydrate plugging problem is the addition of low-dose inhibitors (LDHIs), but it is not yet known whether the precipitation of wax crystals will affect their effectiveness. Therefore, in this study, the hydrate cohesive force within the wax-free/wax-containing system was directly measured by using a micromechanical force device (MMF) and the reasons for the change in cohesive force were analyzed from a morphological point of view. The results showed that glycine was effective in reducing the cohesion between hydrate particles in both wax-free/wax-containing systems and still exerted the effect of antiagglomeration agent (AA) at very low concentrations (as low as 0.10 wt %). Moreover, the optimum concentration of glycine was 0.50 wt %. At this concentration, the cohesive force decreased from 8.54 to 7.07 mN/m in the wax-free system, a decrease of about 17.2%, while the cohesive force decreased from 5.94 to 2.15 mN/m in the wax-containing system, a decrease of about 63.8%. By observation of the morphology of the hydrate particles, the presence of glycine was found to reduce the volume of the liquid bridge by changing the surface roughness and wettability of the particles, thereby reducing the cohesive force. And when wax was contained in the system, the wax further reduced the wettability by adsorbing on the surface of the hydrate particles. However, under certain AA conditions, the increase in wax concentration (from 0.1 to 0.3 wt %) resulted in the free water inside the hydrate being more likely to form liquid bridges with the surrounding particles, thus weakening the effect of AA. This work analyzes the effect on cohesive force in the simultaneous presence of LDHIs and wax from a morphological point of view, which is beneficial in providing more insights into securing safe hydrate flow management
Universal occurrence of organophosphate tri-esters and di-esters in marine sediments: Evidence from the Okinawa Trough in the East China Sea
No full textDespite numerous data on organophosphate tri-esters (tri-OPEs) in the environment, literatures on organophosphate di-esters (di-OPEs) in field environment, especially marine sediments remain scarce. This study addresses this gap by analyzing 35 abyssal sediment samples from the middle Okinawa Trough in the East China Sea. A total of 25 tri-OPEs and 10 di-OPEs were determined, but 13 tri-OPEs and 2 di-OPEs were nondetectable in any of these sediment samples. The concentrations of n-ary sumation 12tri-OPE and n-ary sumation 8di-OPE were 0.108-32.2 ng/g (median 1.11 ng/g) and 0.548-15.0 ng/g (median 2.74 ng/g). Chlorinated (Cl) tri-OPEs were the dominant tri-esters, accounting for 47.5 % of total tri-OPEs on average, whereas chlorinated di-OPEs represented only 19.2 % of total di-OPEs. This discrepancy between the relatively higher percentage of Cl-tri-OPEs and lower abundance of Cl-di-OPEs may be ascribed to the stronger environmental persistence of chlorinated tri-OPEs. Source assessment suggested that di-OPEs were primarily originated from the degradation of tri-OPEs rather than industrial production. Long range waterborne transport facilitated by oceanic currents was an important input pathway for OPEs in sediments from the Okinawa Trough. These findings enhance the understanding of the sources and transport of OPEs in marine sediments, particularly in the Okinawa Trough
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