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1.
Nat Chem ; 2024 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-38570729

RESUMO

Lithium metal batteries represent a promising technology for next-generation energy storage, but they still suffer from poor cycle life due to lithium dendrite formation and cathode cracking. Fluorinated solvents can improve battery longevity by improving LiF content in the solid-electrolyte interphase; however, the high cost and environmental concerns of fluorinated solvents limit battery viability. Here we designed a series of fluorine-free solvents through the methylation of 1,2-dimethoxyethane, which promotes inorganic LiF-rich interphase formation through anion reduction and achieves high oxidation stability. The anion-derived LiF interphases suppress lithium dendrite growth on the lithium anode and minimize cathode cracking under high-voltage operation. The Li+-solvent structure is investigated through in situ techniques and simulations to draw correlations between the interphase compositions and electrochemical performances. The methylation strategy provides an alternative pathway for electrolyte engineering towards high-voltage electrolytes while reducing dependence on expensive fluorinated solvents.

2.
Huan Jing Ke Xue ; 45(3): 1561-1576, 2024 Mar 08.
Artigo em Chinês | MEDLINE | ID: mdl-38471870

RESUMO

At the time when water resources are in short supply,wastewater recycling is both an important environmental protection strategy and also a resource strategy. Disinfection is essential to ensure the biological safety of reclaimed wastewater by killing pathogens and preventing the spread of waterborne diseases. However,the disinfection process could inevitably produce toxic disinfection byproducts(DBPs)due to the reaction between the disinfectants and wastewater organic matters. Regarding wastewater DBPs,this study reviewed their identification methods,formation conditions(including precursors,the effect of water quality,disinfectants,and operational parameters on DBPs),and control methods(including source control,process control,and end control). In addition,future research trends of wastewater DBPs were discussed.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Desinfecção/métodos , Águas Residuárias , Purificação da Água/métodos , Poluentes Químicos da Água/análise , Halogenação
4.
Nat Commun ; 15(1): 1206, 2024 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-38332019

RESUMO

Micro-sized silicon anodes can significantly increase the energy density of lithium-ion batteries with low cost. However, the large silicon volume changes during cycling cause cracks for both organic-inorganic interphases and silicon particles. The liquid electrolytes further penetrate the cracked silicon particles and reform the interphases, resulting in huge electrode swelling and quick capacity decay. Here we resolve these challenges by designing a high-voltage electrolyte that forms silicon-phobic interphases with weak bonding to lithium-silicon alloys. The designed electrolyte enables micro-sized silicon anodes (5 µm, 4.1 mAh cm-2) to achieve a Coulombic efficiency of 99.8% and capacity of 2175 mAh g-1 for >250 cycles and enable 100 mAh LiNi0.8Co0.15Al0.05O2 pouch full cells to deliver a high capacity of 172 mAh g-1 for 120 cycles with Coulombic efficiency of >99.9%. The high-voltage electrolytes that are capable of forming silicon-phobic interphases pave new ways for the commercialization of lithium-ion batteries using micro-sized silicon anodes.

7.
BMC Infect Dis ; 23(1): 532, 2023 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-37580698

RESUMO

INTRODUCTION: Psittacosis can cause severe community-acquired pneumonia (CAP). The clinical manifestations of psittacosis range from subclinical to fulminant psittacosis with multi-organ failure. It is essential to summarize the clinical characteristic of patients with severe psittacosis accompanied by acute hypoxic respiratory failure (AHRF). METHODS: This retrospective study included patients with severe psittacosis caused CAP accompanied by AHRF from 19 tertiary hospitals of China. We recorded the clinical data, antimicrobial therapy, respiratory support, complications, and outcomes. Chlamydia psittaci was detected on the basis of metagenomic next-generation sequencing performed on bronchoalveolar lavage fluid samples. Patient outcomes were compared between the treatment methods. RESULTS: This study included 45 patients with severe CAP and AHRF caused by psittacosis from April 2018 to May 2021. The highest incidence of these infections was between September and April. There was a history of poultry contact in 64.4% of the patients. The median PaO2/FiO2 of the patients was 119.8 (interquartile range, 73.2 to 183.6) mmHg. Four of 45 patients (8.9%) died in the ICU, and the median ICU duration was 12 days (interquartile range, 8 to 21) days. There were no significant differences between patients treated with fluoroquinolone initially and continued after the diagnosis, fluoroquinolone initially followed by tetracycline, and fluoroquinolone combined with tetracycline. CONCLUSION: Psittacosis caused severe CAP seems not rare, especially in the patients with the history of exposure to poultry or birds. Empirical treatment that covers atypical pathogens may benefit such patients, which fluoroquinolones might be considered as an alternative.


Assuntos
Infecções Comunitárias Adquiridas , Pneumonia , Psitacose , Insuficiência Respiratória , Animais , Humanos , Psitacose/complicações , Psitacose/diagnóstico , Psitacose/tratamento farmacológico , Estudos Retrospectivos , Infecções Comunitárias Adquiridas/diagnóstico , Tetraciclina/uso terapêutico , Aves Domésticas , Fluoroquinolonas/uso terapêutico , China/epidemiologia
8.
Water Res ; 235: 119879, 2023 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-36934541

RESUMO

Changes in spectral features and molecular weight (MW) of dissolved organic matter (DOM) along the A/A/O processes in eight full-scale wastewater treatment plants (WWTPs) were characterized using size exclusion chromatography with a diode array detector, a fluorescence detector and an organic carbon detector in tandem (SEC-DAD-FLD-OCD) as well as bulk water quality parameters. The parallel factor (PARAFAC) and the nonnegative matrix factorization (NMF) analyses have been effectively applied to the postprocessing of SEC-FLD fingerprints and SEC-OCD chromatograms, respectively. Individual SEC-FLD-PARAFAC or SEC-OCD-NMF components may span a broad range of MW, indicating that these SEC fractions within the same component were cognate and varied coherently across the dataset samples. The SEC-FLD-PARAFAC modeling and SEC-OCD-NMF analysis have clearly and concisely presented that the dramatic decreases of dissolved organic carbon, UV absorbance at 254 nm and protein-like fluorescence at Ex280/Em350 nm in the anaerobic process were primarily associated with the degradation of the large MW proteinaceous and polysaccharide-like biopolymers. It has also revealed that fluorescence of humic acid-like fractions increased significantly during the anaerobic process, but fluorescence of fulvic acid-like and humic substances' building blocks decreased slightly. Laboratory experiments further confirmed the presence of the humification process in anaerobic processes, and the formation of humic acid-like fluorophores may be associated with carbohydrate metabolism. The combination of SEC-FLD-PARAFAC and SEC-OCD-NMF helped to establish the links between changes in bulk water quality parameters and the evolution of SEC MW fractions, which provides a more in-depth insight into wastewater DOM treatability and enables the optimization of wastewater treatment processes.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Matéria Orgânica Dissolvida , Substâncias Húmicas/análise , Poluentes Químicos da Água/análise , Proteínas , Cromatografia em Gel , Espectrometria de Fluorescência/métodos , Análise Fatorial
9.
Water Res ; 232: 119702, 2023 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-36758356

RESUMO

Electrochemical oxidation (EO) is an attractive option for treatment of dissolved organic matter (DOM) in landfill leachate but concerns remain over the energy efficiency and formation of oxidation byproducts ClO3- and ClO4-. In this study, EO treatment of landfill leachates was carried out using representative active and nonactive anode materials, cell configurations and current densities. Size exclusion chromatograms coupled with 2D synchronous and asynchronous correlation analysis showed that the sensitivity of DOM fractions to EO degradation was dependent on the anode material. The nonactive boron-doped diamond (BDD) anode demonstrated the best performance for DOM oxidation. The humic acid-like fraction (HA, 2.5-20 kDa) predominated the visible absorbance of landfill leachates at λ ≥400 nm, and it generally had the highest reaction rates except the occurrence of the pH-induced denaturation and precipitation of the proteinaceous biopolymer fraction (BP, >20 kDa). During the EO treatment of landfill leachate with BDD anode, the UV absorbance spectra of landfill leachates at wavelengths <400 nm were affected by the formation of free chlorine. Instead, the decrease of Abs420 was found to be a good indicator of the shift of the oxidation from predominantly HA fraction to the proteinaceous BP fraction. The behavior of the Abs420 parameter was also indicative of the transition from the energy-efficient oxidation of DOM to the dominance of side reactions of chlorine evolution and the subsequent formation of ClO3- and ClO4-. These findings suggest that the EO treatment of landfill leachate can be optimized by adjusting the current density with feedback signals from the online monitoring of Abs420, to achieve a trade-off between degradation of DOM and control of ClO3- and ClO4-.


Assuntos
Matéria Orgânica Dissolvida , Poluentes Químicos da Água , Poluentes Químicos da Água/química , Cloro/análise , Oxirredução , Análise Espectral
10.
J Environ Sci (China) ; 125: 309-318, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36375916

RESUMO

Accurate quantification of dissolved organic nitrogen (DON) has been a challenge due to the cumulative analytical errors in the conventional method via subtracting dissolved inorganic nitrogen species (DIN) from total dissolved nitrogen (TDN). Size exclusion chromatography coupled with an organic nitrogen detector (SEC-OND) has been developed as a direct method for quantification and characterization of DON. However, the applications of SEC-OND method still subject to poor separations between DON and DIN species and unsatisfied N recoveries of macromolecules. In this study, we packed a series of SEC columns with different lengths and resin materials for separation of different N species and designed an independent vacuum ultraviolet (VUV) oxidation device for complete oxidation converting N species to nitrate. To guarantee sufficient N recoveries, the operation conditions were optimized as oxidation time ≥ 30 min, injection mass (sample concentration × injection volume) < 1000 µL × mg-N/L for macromolecular proteins, and neutral pH mobile eluent. The dissolved O2 concentration in SEC mobile phase determined the upper limit of VUV oxidation at a specific oxidation time. Compared to conventional HW50S column (20 × 250 mm), HW40S column (20 × 350 mm) with mobile phase comprising of 1.5 g/L Na2HPO4·2H2O + 2.5 g/L KH2PO4 (pH = 6.85) could achieve a better separation of DON, nitrite, nitrate, and ammonia. When applied to river water, lake water, wastewater effluent, groundwater, and landfill leachate, the SEC-OND method could quantify DON as well as DIN species accurately and conveniently even the DIN/TDN ratio reached 0.98.


Assuntos
Nitratos , Nitrogênio , Nitrogênio/análise , Nitratos/análise , Nitritos , Amônia/análise , Matéria Orgânica Dissolvida , Compostos Orgânicos/análise , Cromatografia em Gel , Óxidos de Nitrogênio/análise , Água/química
11.
Chemosphere ; 308(Pt 3): 136359, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36099987

RESUMO

The characteristics of dissolved organic matter (DOM) in the influent and secondary effluent from 6 municipal wastewater treatment plants (WWTPs) were investigated with a size exclusion chromatogram (SEC) coupled with multiple detectors to simultaneously detect ultraviolet absorbance, fluorescence, dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) as a function of molecular weight (MW). The SEC chromatograms showed that biopolymers (>6 kDa) and humic substances (0.5-6 kDa) comprised the significant fraction in the influent, while humic substances became the abundant proportion in the secondary effluent. Direct linkages between MW distribution and hydrophobicity of DOM in the secondary effluent were further explored via SEC analysis of XAD resin fractions. DON and DOC with different hydrophobicity exhibited significantly distinct MW distribution, indicating that it was improper to consider DOC as a surrogate for DON. Different from DOC, the order of averaged MW in terms of DON was hydrophobic neutral ≈ transphilic neutral > hydrophobic acid > transphilic acid > hydrophilic fraction. Fluorescence spectral properties exhibited a significant semi-quantitative correlation with MW and hydrophobicity of DOC, with Pearson's coefficients of -0.834 and 0.754 (p < 0.01) for biopolymer and humic substances. Meanwhile, regional fluorescence proportion was demonstrated to indicate the MW and hydrophobicity properties of DON at the semi-quantitative level. The fluorescence excitation-emission matrix (EEM) could be explored to provide a rapid estimation of MW distribution and hydrophobic/hydrophilic proportion of DOC and DON in WWTPs.


Assuntos
Águas Residuárias , Poluentes Químicos da Água , Matéria Orgânica Dissolvida , Substâncias Húmicas/análise , Interações Hidrofóbicas e Hidrofílicas , Peso Molecular , Espectrometria de Fluorescência , Águas Residuárias/química , Poluentes Químicos da Água/análise
12.
Biomacromolecules ; 23(10): 4327-4338, 2022 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-36069679

RESUMO

As the utilization of degradable polymer coatings increased, the accompanying trade-off between good degradability and high-efficiency antidiatom adhesion due to their hydrophobic nature remains unresolved. The study presents a new hydrophobic surface-fragmenting coating consisting of degradable hyperbranched polymers (hereafter denoted as h-LLAx) synthesized by reversible complexation-mediated copolymerization with isobornyl acrylate (IBOA) and divinyl-functional oligomeric poly(l-lactide) (OLLA-V2), both derived from biomass, that exhibited superior resistance (∼0 cell mm-2) to marine diatom Navicula incerta (N. incerta) attachment with higher OLLA content. The combined impact of the microscale hollow semisphere micelles that self-assembled degradable hyperbranched copolymers and hydrolysis-driven self-renewable surfaces following immersion in seawater may account for the remarkable resistance of h-LLAx coatings against N. incerta. Detailed investigations were conducted across multiple perspectives, from hydrolytic degradation to broad-spectrum antibacterial attachment to ecotoxicity assessment. The excellent features of high resistance to marine diatoms and bacterial attachment, degradability, and environmental friendliness make the as-prepared h-LLAx coatings widely sought after for antifouling coating applications.


Assuntos
Incrustação Biológica , Diatomáceas , Antibacterianos , Micelas , Polímeros/química , Polímeros/farmacologia , Propriedades de Superfície
13.
J Immunol Res ; 2022: 1210890, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35832646

RESUMO

Background: Lepidium meyenii Walp. (Maca) has emerged as a functional plant food and traditional herb owing to its biological activities; Maca polysaccharides as an important active component of Maca have good immunomodulatory effect; however, studies on the immunomodulatory effect of Maca polysaccharides are mainly focused on macrophages; little attention has been devoted to the mechanisms and other immune cells. This study is aimed at investigating the immunomodulatory effects and mechanisms of Maca polysaccharides. Methods: Sixty mice were divided into five groups, and the mice were injected with cyclophosphamide to establish an immunosuppression model except for those in the common group. The body weights were measured, as well as immune-related indices, such as organ indices, haematological parameters, lymphocyte cycle, and proliferation, cytokine, and protein expression levels. Results: The weight loss and immune organ index decline caused by cyclophosphamide could be reversed by MP. Furthermore, MP increased WBC and HGB counts and reduced the ratio of G0/G1 phase obviously, increased the proportion of S phase and G2/M phase in peripheral blood lymphocytes, increased the counts of CD4+ T cells and the ratio of CD4+/CD8+, and reduced the inhibition rate of splenic lymphocytes. MP affected the production of cytokines by increasing IFN-γ, TNF-α, and IL-2 levels and by decreasing IL-4 levels. MP increased the mRNA expression of T-bet and the protein expression of Bcl-2 in the spleen and decreased the protein expression of caspase-3 and Bax. Conclusions: Maca polysaccharides might be the basic material for Maca's immunomodulatory effect. The mechanism was perhaps related to inhibiting lymphocyte apoptosis and promoting the balance of Th1/Th2 cell subsets.


Assuntos
Lepidium , Animais , Ciclofosfamida/efeitos adversos , Terapia de Imunossupressão , Camundongos , Extratos Vegetais/farmacologia , Polissacarídeos/farmacologia
14.
Dig Endosc ; 34(5): 1063-1068, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35569111

RESUMO

To overcome difficulties in the removal of duodenal bulb lesions, especially those in anatomically challenging locations, we developed the endoscopic resection via antral submucosal tunneling (ERAST) technique. In this study, we evaluated the feasibility and safety of ERAST for the removal of superficial and subepithelial lesions in the duodenal bulb. This was a single-center retrospective study of 10 patients with lesions in the bulb. Submucosal tunneling from the gastric antrum to the duodenum was performed to facilitate en bloc tumor resection in the bulb. The en bloc resection rate, postoperative bleeding, and perforation were the primary endpoints. Ten lesions (four superficial and six subepithelial), with an average size of 19.1 ± 9.2 mm, were resected en bloc by ERAST. Esophagogastroduodenoscopy follow-up after 2 months indicated complete wound healing in all patients. In our primary experience, ERAST was found to be a feasible and safe endoscopic resection technique for the removal of lesions in the duodenal bulb, especially those that are difficult to access.


Assuntos
Ressecção Endoscópica de Mucosa , Neoplasias Gástricas , Duodeno/cirurgia , Ressecção Endoscópica de Mucosa/métodos , Endoscopia , Humanos , Estudos Retrospectivos , Neoplasias Gástricas/cirurgia , Resultado do Tratamento
15.
Front Pediatr ; 10: 767690, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35372151

RESUMO

Objective: This study aimed to investigate whether the ventilation duration for children undergoing invasive mechanical ventilation (IMV) in pediatric intensive care unit (PICU) is correlated with pediatric sequential organ failure (pSOFA) score, white blood cell (WBC) count, blood lactate level, and duration of fever. Methods: Retrospectively reviewed that the medical records of patients who received IMV in the PICU of Jingzhou Central Hospital between January 2018 and December 2020. According to the duration of IMV in diagnosis-related groups, these patients were divided into two groups: group A, ventilation duration <96 h, and group B, ventilation duration ≥96 h. Each group's pSOFA scores, WBC counts, blood lactate levels, and durations of fever were compared. Logistic regression analysis was used to analyze the clinical risk factors of ventilation duration ≥96 h, and the receiver operator characteristic (ROC) curve was drawn. Results: A total of 42 patients were included, including 23 in group A and 19 in group B. The difference in pSOFA score between group A and group B was statistically significant (P < 0.05), while the differences in blood lactate level, duration of fever, and WBC count between the two groups were not statistically significant (P > 0.05). Logistic regression analysis was conducted to analyze the influencing factors of mechanical ventilation duration ≥96 h. An ROC curve was drawn with pSOFA score as a test variable and duration of mechanical ventilation ≥96 h as a state variable, revealing that the area under the curve was 0.76 (SE = 0.075, 95% CI: 0.614-0.906, P = 0.005). The sensitivity and specificity were 68.4 and 73.9%, respectively, and the corresponding pSOFA score was 7.5. Conclusion: When the pSOFA score ≥8, the risk of mechanical ventilation duration ≥96 h increases.

16.
Sci Total Environ ; 824: 153793, 2022 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-35150674

RESUMO

A better understanding of the physicochemical properties and fate of algae-derived organic matter (AOM) in water treatments significantly benefits the control of algae-derived disinfection byprodcuts and process parameter optimization. In this study, we conducted a comprehensive investigation of the release and treatability of dissolved organic matter during prechlorination and postcoagulation treatments of cyanobacteria-laden source water via size-exclusion chromatography-tandem diode array detector, fluorescence detector and organic carbon detector. The results revealed that the allochthonous humic substances could protect algal cell membrane from damage during prechlorination at a low level of chlorine dose. Due to the release and oxidation of biopterins during prechlorination of M. aeruginosa cells, the variation of the humic-like fluorescence can be used to indicate the chlorine dose for a sufficient membrane damage of algae cells. The prechlorination of M. aeruginosa cells induced minimal release of large MW biopolymer fractions but much more release of low MW fractions E1 and E2 (i.e., unknown carbonaceous substances and fluorescent nitrogenous biopterins). The physically extracted AOM contained a large proportion of biopolymers and could not well represent those released during prechlorination treatment. During coagulation, the negative effect of humic substances on the coagulant demand to achieve algae removal was more remarkable than AOM released by prechlorination. The high-MW biopolymers and humic substances can be removed over 50% by coagulation. Among the low-MW carbonaceous fractions, E1 released by prechlorination can also be effectively removed via coagulation while fractions C, D (possibly oligopeptides or secondary aromatic metabolites & low MW acids) and nitrogenous biopterins were recalcitrant to coagulation. This study highlights the differences of AOM properties between physical extraction and prechlorination and provides a basis for drinking water treatment plants to give more attention to the recalcitrant low MW fractions in coagulation when treating algae-laden source water.


Assuntos
Cianobactérias , Purificação da Água , Biopolímeros , Cloro , Substâncias Húmicas/análise , Nitrogênio/análise , Purificação da Água/métodos
17.
Zhongguo Ying Yong Sheng Li Xue Za Zhi ; 37(6): 584-588, 2021 Nov.
Artigo em Chinês | MEDLINE | ID: mdl-34821088

RESUMO

Objective: To investigate the intervention effects and mechanism of interleukin-17A (IL-17A) on chronic obstructive pulmonary disease (COPD). Methods: C57BL/6 mice were randomly divided into wild type blank control group, wild type COPD group and IL-7A knockout COPD group. Mice in wild type blank control group received no treatment, and mice in the other two groups were exposed to cigarette smoke to induce COPD (Cigarette: 1 cigarette / time, 4 times/day, 45 minutes/time; interval time: 1 hour; total intervention time: 90 days). Lung function of mice was assessed using animal pulmonary function machine. Bronchoalveolar lavage fluid (BALF) of mice was collected and BALF cell count and classification were determined. The lung tissue of mice was collected, the expression level of IL-17A in airway epithelium was determined by flow cytometry, and the levels of inflammatory factors in lung tissue were determined by enzyme-linked immunosorbent assay. The expression level of JNK/AP1 signaling pathway protein in mouse lung tissue was determined by Western blot. Results: Compared with the wild type blank control group mice, the wild type COPD group mice had significantly higher expression level of IL-17A, significantly lower peak inspiratory flow rate (PIF) and peak expiratory flow rate (PEF), significantly higher number of BALF neutrophils, eosinophils, lymphocytes and macrophage, significantly higher expression levels of CXC chemokine 1(CXCL1), CXC chemokine 2 (CXCL2), interleukin-1ß (IL-1ß) and interleukin-6 (IL-6), and significantly higher phosphorylation level of JNK, cJun and cFos and AP1 expression levels (P<0.05). Compared with COPD mice, IL-17A expression level in airway epithelium of mice in IL-7A knockout COPD group was significantly lower, PIF and PEF were higher, the number of BALF neutrophils, eosinophils, lymphocytes and macrophage was significantly lower, the expression levels of CXCL1, CXCL2, IL-1ß and IL-6 in lung tissue were lower, and the phosphorylation levels of JNK, cJun and cFos and AP1 expression levels were significantly lower (P<0.05). Conclusion: Cigarette smoke can induce the production of IL-17A and reduce (or inhibit) the production (or expression or secretion) of IL-17A in mouse airway epithelium, thus inhibiting the JNK/AP1 signaling pathway to reduce the airway inflammation and improve the lung function of COPD mice.


Assuntos
Interleucina-17 , Doença Pulmonar Obstrutiva Crônica , Animais , Líquido da Lavagem Broncoalveolar , Fumar Cigarros , Interleucina-17/genética , Pulmão , Sistema de Sinalização das MAP Quinases , Camundongos , Camundongos Endogâmicos C57BL
18.
Inorg Chem ; 60(19): 14697-14705, 2021 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-34555280

RESUMO

[Nb(η6-C6H3Me3)2] reacts with ethylenediamine (en) solutions of K4Ge9 in the presence of 18-crown-6 to give [(η6-C6H3Me3)NbHGe6]2- (1) and [(η6-C6H3Me3)NbGe6Nb(η6-C6H3Me3)]2- (2) as their corresponding [K(18-crown-6)]+ salts. The crystalline solids are dark brown, air-sensitive, and sparingly soluble or insoluble in most solvents. The [K(18-crown-6)]+ salts of cluster ions 1 and 2 have been characterized by energy-dispersive X-ray (EDX) analysis, NMR studies, single-crystal X-ray diffraction, and electrospray ionization time-of-flight (ESI-TOF) mass spectrometry studies. Cluster ions 1 and 2 have markedly different [Ge6] moieties: an electron-deficient carborane-like subunit in 1 and a two-center, two-electron cyclohexane-like subunit in 2.

19.
Chemosphere ; 280: 130937, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34162109

RESUMO

Nitrate and sulfate often coexist in organic wastewater. In this study, an internal circulation anaerobic reactor was conducted to investigate the impact of nitrate on sulfate reduction. The results showed that sulfate reduction rate dropped from 78.4% to 41.4% at NO3- /SO42- ratios ranging from 0 to 1.03, largely attributed to the inactivity of acetate-utilizing sulfate-reducing bacteria (SRB) and preferential usage of nitrate of propionate-utilizing SRB. Meanwhile, high nitrate removal efficiency was maintained and COD removal efficiency increased with nitrate addition. Enhancement of propionate and butyrate degradation based on Modified Gompertz model and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2) analysis. Moreover, nitrate triggered the shift of microbial community and function. Twelve genera affiliated to Firmicutes, Bacteroidetes and Proteobacteria were identified as keystone genera via network analysis, which kept functional stability of the bacterial community responding to nitrate stress. Increased nitrate inhibited Desulfovibrio, but promoted the growth of Desulforhabdus. Both the predicted functional genes associated with assimilatory sulfate reduction pathway (cysC and cysNC) and dissimilatory sulfate reduction pathway (aprA, aprB, dsrA and dsrB) exhibited negative relationship with nitrate addition.


Assuntos
Desulfovibrio , Nitratos , Anaerobiose , Reatores Biológicos , Oxirredução , Filogenia , Sulfatos
20.
Sci Total Environ ; 754: 142297, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33254877

RESUMO

A simple and rapid method employing non-suppressed ion chromatography with electrospray ionization tandem mass spectrometry has been developed for the direct determination of trace-level haloacetic acids (HAAs) in water samples. Using 70/30 (v/v) acetonitrile/1 M aqueous methylamine as the mobile phase, three IC columns - AS16, AS18 and AS24 from Thermo-Scientific - were tested, respectively, with the AS16 column exhibiting the best overall performance with respect to resolution and retention time. To assess the effects of mobile phase composition on retention time of HAAs, the AS16 column was further tested using (i) different proportions of acetonitrile to aqueous methylamine, (ii) different proportions of acetonitrile to aqueous solution at fixed methylamine concentrations, and (iii) different concentrations of methylamine at fixed proportions of acetonitrile to aqueous solution. With a low proportion of aqueous solution, van der Waals and/or hydrogen-bonding interactions appeared to play an important role in governing HAA retention, i.e., HAAs with relatively higher apparent logKow* caused by elevated solvent sspKa exhibited longer retention times; whereas with a high proportion of aqueous solution, ionic interactions appeared to dominate retention of HAAs, with the more polarizable HAAs exhibiting longer retention times. Using 70/30 (v/v) acetonitrile/1 M aqueous methylamine, the method detection limits were in the range of 0.090-0.216 µg/L for the 11 selected chloro-, bromo- and iodoacetic acids. Finally, this method was applied to monitor HAAs yields in laboratory chlorination experiments and to determine concentrations of HAAs in tap water and wastewater effluent samples.

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