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1.
Sci Total Environ ; 803: 149783, 2022 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-34482132

RESUMO

Understanding the hydro-biogeochemical conditions that impact the mobility of uranium (U) in natural or artificial wetlands is essential for the management of contaminated environments. Field-based research indicates that high organic matter content and saturation of the soil from the water table create favorable conditions for U accumulation. Despite the installation of artificial wetlands for U remediation, the processes that can release U from wetland soils to underlying aquifers are poorly understood. Here we used a large soil core from a montane wetland in a 6 year lysimeter experiment to study the stability of U accumulated to levels of up to 6000 ppm. Amendments with electron acceptors showed that the wetland soil can reduce sulfate and Fe(III) in large amounts without significant release of U into the soil pore water. However, amendment with carbonate (5 mM, pH 7.5) resulted in a large discharge of U. After a six-month period of imposed drought, the re-flooding of the core led to the release of negligible amounts of U into the pore water. This long-term experiment demonstrates that U is strongly bound to organic matter and that its stability is only challenged by carbonate complexation.


Assuntos
Urânio , Carbonatos , Elétrons , Compostos Férricos , Solo , Urânio/análise , Áreas Alagadas
2.
Chemosphere ; 286(Pt 2): 131779, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34364225

RESUMO

Anaerobic decolorization of azo dye in sulfate-containing wastewater has been regarded as an economical and effective method, but it is generally limited by the high concentration of azo dye and accumulation of toxic intermediates. To address this problem, Fe3O4 was added to one of the anaerobic reactors to investigate the effects on system performances. Results showed that AO7 removal rate, COD removal rate, and sulfate reduction were enhanced with the addition of Fe3O4 under various influent AO7 concentrations (153 mgCOD/L - 1787 mgCOD/L). According to the proposed pathway for the degradation of AO7, more intermediates (2-hydroxy-1,4-naphthoquinone, phthalide, 4-methylphenol) were produced in the presence of Fe3O4. The electron transfer capacity of sludge was also increased since Fe3O4 could stimulate to secrete humic acid-like organics in EPS. Microbial analysis showed that iron-reducing bacteria like Clostridium and Geobacter were also enriched, which were capable of azo dye and aromatic compounds degradation.


Assuntos
Compostos Azo , Microbiota , Anaerobiose , Reatores Biológicos , Corantes , Elétrons , Óxidos , Sulfatos
3.
Chemosphere ; 286(Pt 2): 131755, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34365173

RESUMO

Humic substances (HS) possess redox active groups covering a wide range of potentials and are used by facultative anaerobic microorganisms as electron acceptors. To serve as suitable electron shuttles for anaerobic respiration, HS should be able to re-oxidize relatively quickly to prevent polarization of the surrounding medium. Mediated electrochemical oxidation and decolorization assays, based on the reduction of the radical ion of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS•-) allow to determine the electron donating capacity (EDC) of HS, but uncertainties remain about the reaction time that should be allowed to obtain environmentally meaningful EDC values. In this work, we performed a kinetic analysis of the time trend of the reduction of ABTS•- by HS by Vis and Electron Paramagnetic Resonance (EPR) spectroscopies and by cyclic voltammetry. We found evidences of two concomitant separate mechanisms of electron exchange: a fast and a slow transfer processes which may have different environmental roles. These results can set a base to identify the appropriate conditions for the spectrophotometric determination of the fast and slow components of the EDC of HS.


Assuntos
Elétrons , Substâncias Húmicas , Transporte de Elétrons , Substâncias Húmicas/análise , Cinética , Oxirredução
4.
Chemosphere ; 286(Pt 2): 131765, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34371351

RESUMO

Photocatalytic conversion of carbon dioxide (CO2) into gaseous hydrocarbon fuels is an auspicious way to produce renewable fuels in addition to greenhouse gas emission mitigation. In this work, non-metals (B, O, P, and S) doped graphitic carbon nitride (g-C3N4) was prepared via solid-state polycondensation of urea for photocatalytic CO2 reduction into highly needed methane (CH4) with water under UV light irradiation. The various physicochemical characterization results reveal the successful incorporation of B, O, P, and S elements in the g-C3N4 matrix. The maximum CH4 yield of 55.10 nmol/(mLH2O.gcat) over S-doped g-C3N4 has been obtained for CO2 reduction after 7 h of irradiation. This amount of CH4 production was 1.9, 1.4, 1.7, and 2.4-folds higher than B, O, P and bare g-C3N4 samples. The doping of S did not enlarge the surface area and photon absorption ability of the g-C3N4 sample, but this significant improvement was evidently due to effective charge separation and migration. The observed results imply that the doping of non-metal elements provides improved charge separation and is an effective way to boost photocatalyst performance. This work offers an auspicious approach to design non-metal doped g-C3N4 photocatalysts for renewable fuel production and would be promising for other energy application.


Assuntos
Dióxido de Carbono , Água , Catálise , Elétrons , Porosidade
5.
Chemosphere ; 286(Pt 3): 131856, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34399268

RESUMO

The development in urbanization, growth in industrialization and deficiency in crude oil wealth has made to focus more for the renewable and also sustainable spotless energy resources. In the past two decades, the concepts of microbial fuel cell have caught more considerations among the scientific societies for the probability of converting, organic waste materials into bio-energy using microorganisms catalyzed anode, and enzymatic/microbial/abiotic/biotic cathode electro-chemical reactions. The added benefit with MFCs technology for waste water treatment is numerous bio-centered processes are available such as sulfate removal, denitrification, nitrification, removal of chemical oxygen demand and biological oxygen demand and heavy metals removal can be performed in the same MFC designed systems. The various factors intricate in MFC concepts in the direction of bioenergy production consists of maximum coulombic efficiency, power density and also the rate of removal of chemical oxygen demand which calculates the efficacy of the MFC unit. Even though the efficacy of MFCs in bioenergy production was initially quietly low, therefore to overcome these issues few modifications are incorporated in design and components of the MFC units, thereby functioning of the MFC unit have improvised the rate of bioenergy production to a substantial level by this means empowering application of MFC technology in numerous sectors including carbon capture, bio-hydrogen production, bioremediation, biosensors, desalination, and wastewater treatment. The present article reviews about the microbial community, types of substrates and information about the several designs of MFCs in an endeavor to get the better of practical difficulties of the MFC technology.


Assuntos
Fontes de Energia Bioelétrica , Microbiota , Análise da Demanda Biológica de Oxigênio , Eletricidade , Eletrodos , Elétrons , Águas Residuárias
6.
J Hazard Mater ; 422: 126761, 2022 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-34418836

RESUMO

Carbon and its analogous nanomaterials are beneficial for toxic gas sensors since they are used to increase the electrochemically active surface region and improve the transmission of electrons. The present article addresses a detailed investigation on the potential of the monolayer PC3 compound as a possible sensor material for environmentally toxic nitrogen-containing gases (NCGs), namely NH3, NO, and NO2. The entire work is carried out under the frameworks of density functional theory, ab-initio molecular dynamics simulations, and non-equilibrium Green's function approaches. The monolayer-gas interactions are studied with the van der Waals dispersion correction. The stability of pristine monolayer PC3 is confirmed through dynamical, mechanical, and thermal analyses. The mobility and relaxation time of 2D PC3 sensor material with NCGs are obtained in the range of 101-104 cm2 V-1 s-1 and 101-103 fs for armchair and zigzag directions, respectively. Out of six possible adsorption sites for toxic gases on the PC3 surface, the most prominent site is identified with the highest adsorption energy for all the NCGs. Considering the most stable configuration site of the NCGs, we have obtained relevant electronic properties by utilizing the band unfolding technique. The considerable adsorption energies are obtained for NO and NO2 compared to NH3. Although physisorption is observed for all the NCGs on the PC3 surface, NO2 is found to convert into NO and O at 5.05 ps (at 300 K) under molecular dynamics simulation. The maximum charge transfer (0.31e) and work function (5.17 eV) are observed for the NO2 gas molecule in the series. Along with the considerable adsorption energies for NO and NO2 gas molecules, their shorter recovery time (0.071 s and 0.037 s, respectively) from the PC3 surface also identifies 2D PC3 as a promising sensor material for those environmentally toxic gases. The experimental viability and actual implications for PC3 monolayer as NCGs sensor material are also confirmed by examining the humidity effect and transport properties with modeled sensor devices. The transport properties (I-V characteristics) reflect the significant sensitivity of PC3 monolayer toward NO and NO2 molecules. These results certainly confirm PC3 monolayer as a promising sensor material for NO and NO2 NCG molecules.


Assuntos
Gases , Nanoestruturas , Adsorção , Elétrons , Nitrogênio
7.
Chemosphere ; 287(Pt 4): 132381, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34606902

RESUMO

Herein, the major biochar properties were correlated with electron transfer of zerovalent iron (ZVI) and contribution of biomass constituents to biochar property was ascertained to optimize electron transfer of ZVI. To this end, five respective stalk-type and wood-type lignocellulosic biomasses were pyrolzed at 600 °C to prepare biochars to harbor ZVI (ZVI/BC). Thermogravimetric analysis demonstrated woody biomasses decomposed more intensively at higher temperature relative to stalky biomass. ZVI/BC were characterized with Raman, X-ray diffraction, and electrochemical analyses including electron donating capacity (EDC) and electron accepting capacity (EAC). Pearson correlation and partial least-squares (PLS) analyses confirmed that Cr(VI) reduction capacity was negatively related to Tafel corrosion potential and intensity ratio of ID/IG, but significantly positively-related to EDC of BC, in which EDC was a predominant attribute to contribute to reductive capacity toward Cr(VI) reduction. That is, greater EDC and higher graphitic carbon structure of biochar due to cellulose and hemicellulose components favor electron transfer of ZVI toward Cr(VI) reduction.


Assuntos
Ferro , Poluentes Químicos da Água , Carbono , Carvão Vegetal , Cromo/análise , Elétrons , Poluentes Químicos da Água/análise
8.
Chemosphere ; 287(Pt 2): 132133, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34826893

RESUMO

Benzotriazole (BTA), which is extensively served as household and engineering agent, is one of the emerging and persistent contaminants. Despite the spirit to remove BTA is willing, the traditional wastewater treatments are weak. Therefore, the degradation of BTA via electron beam was systematically explored in this study. It turned out that after 5.0 kGy irradiation, even 87.5 mg L-1 BTA could be completely removed, and the irradiation conformed perfectly to the pseudo first-order kinetics model. The effects of solution pH, inorganic anions (CO32-, HCO3-, NO3-, NO2-, SO42-, SO32-, Cl-), and gas atmosphere were all explored. And results indicated that oxidative hydroxyl radicals played critical role in BTA irradiation. Additionally, presence of H2O2 and K2S2O8 promoted significantly not only degradation extent but also mineralization efficiency of BTA due to they both augmented the generation of oxidative free radicals. Moreover, by combining theoretical calculations with experimental results, it could be inferred that degradation of BTA was mainly carried out by the benzene ring-opening. Further toxicity evaluation proved that as irradiation proceeded, the toxicity alleviated. Taken together, there were various indications that BTA could be effectively eliminated by electron beam irradiation in aquatic environments.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Elétrons , Peróxido de Hidrogênio , Cinética , Oxirredução , Triazóis , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade
9.
Chemosphere ; 287(Pt 2): 132154, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34826897

RESUMO

Designing catalysts that can effectively activate oxygen and hydrogen peroxide is a huge challenge in electro-Fenton (EF) process. Considering the superior ability of electrons transport and activation of H2O2, ceria encapsulated with N, P-codoped carbon material was a promising catalyst for EF reaction. Herein, CeO2-NPCTX (where T and X represented the calcination temperature and the initial mass of CeO2, respectively) materials were synthesized via pyrolysis process and used as catalysts to degrade ciprofloxacin (CIP) in EF process. The results indicated that CeO2-NPC1000100 catalyst had good degradation performance under the optimal conditions. Compared with CeO2 and CeO2-NC1000100 catalysts, CeO2-NPC1000100 catalyst had more content of graphite N and more oxygen vacancies, which were beneficial to activation of oxygen and hydrogen peroxide. Scavenging experiments and electron paramagnetic resonance analysis confirmed ·O2- and ·OH were the main reactive oxygen species in the CIP degradation process. And three logical degradation routes of CIP were given. In addition, CeO2-NPC1000100 catalyst still had good stability after three times of continuous operation, and presented good universality for the treatment of a variety of antibiotic wastewaters. Finally, a convincing mechanism in the EF system with CeO2-NPC1000100 for CIP degradation was proposed.


Assuntos
Peróxido de Hidrogênio , Poluentes Químicos da Água , Carbono , Catálise , Elétrons , Oxirredução , Poluentes Químicos da Água/análise
10.
Chemosphere ; 287(Pt 2): 132228, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34826921

RESUMO

Hexavalent chromium (Cr(VI)) and methyl orange (MO) are highly toxic and difficult to treat. Electron beam irradiation (EB) can produce ·OH, H·, ·O2-, hydrated electron (eaq-) and other active substances, which have strong redox ability to pollutants. However, the penetration capacity of EB is limited (the penetration depth of water is 10 cm). Therefore, the photocatalytic method of graphitic carbon nitride (CN) was used as the synergistic method of EB in this project to degrade Cr(VI) and MO. The results showed that the maximum treatment efficiency of 100 mg L-1 Cr(VI) and 50 mg L-1 MO with liquid surface height of 5 cm was 95.0% and 99.1%, respectively, which was much higher than that of single photocatalytic method (39.5%, 23.4%) and EB (79.6%, 92.1%), and the efficiency of synergistic treatment was higher under acidic condition. When the liquid depth increased to 30 cm, the efficiency of synergistic system decreased by 14.7% and 15.2% for the degradation of Cr(VI) and MO, respectively, less than the single EB treatment (47.2%, 45.7%). Additionally, the performance of the morphology, the light absorption performance, and the separation of photogenerated electron-hole pairs of the CN were evaluated before and after the synergistic system. Lastly, the mechanism illustrates that the electron and thermal effects of EB, eaq-, photogenerated electrons played key roles for the Cr(VI) reduction, and the electron and thermal effects of EB, ·O2-, photogenerated holes played key roles for the MO degradation. This study provides a new opportunity for the synergistic system of photocatalyst and EB in the treatment of pollutants.


Assuntos
Cromo , Elétrons , Compostos Azo , Catálise , Grafite , Compostos de Nitrogênio
11.
Bioresour Technol ; 343: 125896, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34649059

RESUMO

This study for the first time bioreduced Te(IV) using elemental sulfur (S0) as electron donor, achieving 91.17%±0.8% conversion with reaction rate of 0.77 ± 0.01 mg/L/h in a 60-day cultivation. Characterization using X-ray photoelectron spectroscopy and X-ray power diffraction analyses confirmed that most removed Te(IV) was reduced to elemental Te(0) deposits, while ion chromatogram analysis showed that most S(0) was oxidized to sulfite and sulfate. High-throughput 16S rRNA gene sequencing indicated that the Te(IV) reduction coupled to S(0) oxidation was mediated synergistically by a microbial consortia with S(0)-oxidizing bacteria (Thiobacillus) to generate volatile fatty acids as metabolites and Te(IV)-reducing bacteria (Rhodobacter) to consume formed volatile fatty acids to yield Te(0). The synergy between these two strains presents a novel bioremediation consortium to efficiently treat Te(IV) wastewaters.


Assuntos
Elétrons , Enxofre , Oxirredução , RNA Ribossômico 16S/genética , Sulfatos
12.
Bioresour Technol ; 343: 126144, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34673194

RESUMO

The effectiveness of producing n-caproate from food waste without external electron donors (EDs) was investigated through batch and semi-continuous fermentation. The maximum concentration of n-caproate reached 10,226.28 mg COD/L during semi-continuous fermentation. The specificity for n-caproate was the highest at 40.19 ± 3.95%, and the soluble COD conversion rate of n-caproate reached up to 22.50 ± 1.09% at the end of batch fermentation. The production of n-caproate was coupled with the generation of lactate as an ED to facilitate chain elongation reactions. When lactate was used as the only substrate, n-butyrate (64.12 ± 20.11%) markedly dominated the products, instead of n-caproate (0.63 ± 0.07%). Microbial community analysis revealed that Caproiciproducens, Rummeliibacillus, and Clostridium_sensu_stricto_12 were the key genera related to n-caproate production. In addition to n-caproate, n-butyrate dominated the products in batch and semi-continuous fermentation with a maximum specificity of 47.59 ± 3.39%. Clostridium_sensu_stricto_7 was committed to producing n-butyrate from lactate.


Assuntos
Caproatos , Eliminação de Resíduos , Reatores Biológicos , Elétrons , Fermentação , Alimentos
13.
Methods Mol Biol ; 2414: 97-113, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34784034

RESUMO

Vaccines consisting of whole inactivated bacteria (bacterins) are generated by incubation of the pathogen with chemicals. This is a time-consuming procedure which may lead to less immunogenic material, as critical antigenic structures can be altered by chemical modification. A promising alternative approach is low-energy electron irradiation (LEEI). Like other types of ionizing radiation, it mainly acts by destroying nucleic acids but causes less damage to structural components like proteins. As the electrons have a limited penetration depth, LEEI is currently used for sterilization of surfaces. The inactivation of pathogens in liquids requires irradiation of the culture in a thin film to ensure complete penetration. Here, we describe two approaches for the irradiation of bacterial suspensions in a research scale. After confirmation of inactivation, the material can be directly used for vaccination, without any purification steps.


Assuntos
Vacinas Bacterianas , Elétrons , Bactérias , Radiação Ionizante , Vacinas de Produtos Inativados
14.
Anal Chim Acta ; 1189: 339232, 2022 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-34815030

RESUMO

N-glycosylation is a critical quality attribute for monoclonal antibody (mAb)-based therapeutics due to its significant impact on drug efficacy and safety. Extensive glycosylation mapping is therefore necessary for mAb drug development and quality control. We utilized a higher-energy dissociation product ions-triggered electron-transfer/higher-energy collision dissociation (HCD-pd-EThcD) approach to mapping N-glycosylation in therapeutic mAbs. Due to the improved duty cycle and targeted ability, HCD-pd-EThcD could provide extensive N-glycan identifications as well as higher quality spectra than EThcD mode. On average, ten types of N-glycan were uncovered in two different lots of trastuzumab, demonstrating a significant increment in N-glycan species compared to only four types identified by EThcD. After integrating pre-enrichment of glycopeptides, up to 16 N-glycans were recognized. Significantly, this strategy facilitated the identification of glycopeptides containing fucosylated and sialylated glycans, meanwhile enabled the recognition of different N-glycan classes (high mannose, hybrid, and complex). Further application in the glycosylation analysis of adalimumab and bevacizumab resulted in 19 and 8 N-glycans species, providing a more comprehensive insight into their glycosylation modification status. We demonstrated the benefits of an integrated strategy in characterizing various N-glycans of mAb therapeutics and offer an alternative approach for their quality control at the intact glycopeptides level.


Assuntos
Glicopeptídeos , Polissacarídeos , Elétrons , Glicosilação , Íons
15.
Chemosphere ; 287(Pt 2): 132098, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34509004

RESUMO

The visible light photocatalytic removal of NO in air is a promising way. BiPO4 is restricted by its wide band gap and can only be responded to ultraviolet light. Herein, 1D BiPO4 nanorod/2D g-C3N4 heterostructured photocatalyst was successfully synthesized via a facile one-step hydrothermal process for efficient visible light photocatalytic removal of NO. With simulated sunlight irradiation, the photocatalytic NO removal activity of the BiPO4/g-C3N4 (64%) is much higher than that of the pure BiPO4 (7.2%) and g-C3N4 (50%). Its excellent photocatalytic performance was ascribed to broadening the light response range to visible light and boosting the separation and transfer of photogenerated electrons and holes. The NO photocatalytic removal mechanism was proposed by the free radical trapping experiment and in situ DRIFTS research. The present study might induce a new means to design BiPO4-based heterostructured photocatalysts for the removal of NO from air pollution under simulated solar light irradiation.


Assuntos
Luz , Nanotubos , Catálise , Elétrons
16.
Chemosphere ; 287(Pt 3): 132292, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34562711

RESUMO

The insight into the neglected reduction process accompanied by UV-based oxidation process may provide new ideas for the development of advanced oxidation and reduction technologies. In this study, aniline was comprehensively investigated as an unexpected indicator of hydrated electron (eaq-) under UV irradiation. Monochloroacetic acid (MCAA) was selected as the probe of eaq- and the balance of chloride ions indicated the reduction of MCAA. Further, laser flash photolysis experiments demonstrated the generation of eaq- in the UV/aniline process and the half-life period of formed eaq- was demonstrated to be 0.13 µs. The photolysis of aniline along with the decay of the excited state of aniline was responsible for the eaq- generation. Besides, the hydrogen atom (H) generated from the photolysis can subsequently reacted with OH- to generate eaq-. The photolysis pathways of aniline were proposed by the results of GC-MS. Aniline was abstracted of H in solution to the formation of aniline radical (PhNH) or form aminophenol in three different isomers (orto-, meta- and para-aminophenol). Moreover, UV/aniline showed a higher reducing capacity of MCAA compared with other organic electron donors and sustained a highly reducing ability in a wide pH. And the calculation results of quantum efficiency (Φ) showed that excessive aniline was not conducive to the elevation of Φ. This study introduced a novel pathway of eaq- generation during the photolysis of aniline and provided a new perspective for eaq--based advanced reduction processes.


Assuntos
Elétrons , Poluentes Químicos da Água , Compostos de Anilina , Oxirredução , Fotólise , Raios Ultravioleta , Poluentes Químicos da Água/análise
17.
Chemosphere ; 287(Pt 3): 132285, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34563769

RESUMO

Microbial fuel cell (MFC) is lauded for its potentials to solve both energy crisis and environmental pollution. Technologically, it offers the capability to harness electricity from the chemical energy stored in the organic substrate with no intermediate steps, thereby minimizes the entropic loss due to the inter-conversion of energy. The sciences underneath such MFCs include the electron and proton generation from the metabolic decomposition of the substrate by microbes at the anode, followed by the shuttling of these charges to cathode for electricity generation. While its promising prospects were mutually evinced in the past investigations, the upscaling of MFC in sustaining global energy demands and waste treatments is yet to be put into practice. In this context, the current review summarizes the important knowledge and applications of MFCs, concurrently identifies the technological bottlenecks that restricted its vast implementation. In addition, economic analysis was also performed to provide multiangle perspectives to readers. Succinctly, MFCs are mainly hindered by the slow metabolic kinetics, sluggish transfer of charged particles, and low economic competitiveness when compared to conventional technologies. From these hindering factors, insightful strategies for improved practicality of MFCs were formulated, with potential future research direction being identified too. With proper planning, we are delighted to see the industrialization of MFCs in the near future, which would benefit the entire human race with cleaner energy and the environment.


Assuntos
Fontes de Energia Bioelétrica , Eletricidade , Eletrodos , Elétrons , Humanos , Águas Residuárias
18.
J Colloid Interface Sci ; 607(Pt 2): 1641-1650, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34592551

RESUMO

Peroxymonosulfate (PMS) has been activated for the generation of reactive oxygen species by nitrogen-doped carbonaceous material. However, the influence of phosphate on the degradation performance has not been reported. In this study, phosphate ions accelerate PMS decomposition and degradation of target organic compounds such as carbamazepine, atrazine, sulfamethoxazole, and benzoic acid. It was revealed that the physical mixture of phosphate with Co and N doped graphitic carbon (GcN/Co) demonstrates the occurrence of P C, P N, and P O - C bonds. Essentially, the graphitic N or graphitic N P increased in the presence of phosphate. This was correlated with the lower electrical transfer resistance, improved electrical conductivity, and higher electron morbidity confirmed by different electrochemical tests. Moreover, due to the strong buffering capacity of phosphate at neutral pH, bicarbonate was used to confirm the negligible influence of pH. The presence of phosphate helps to recover the scavenging effect of Cl- but has no effect on the presence of HCO3- and CO32-. Nevertheless, GcN/Co demonstrates good reusability for three reaction cycles, however, in order to maintain a high catalytic performance phosphate needs to be replenished after each cycle.


Assuntos
Grafite , Carbono , Cobalto , Elétrons , Nitrogênio , Peróxidos , Fosfatos
19.
Spectrochim Acta A Mol Biomol Spectrosc ; 265: 120339, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34537632

RESUMO

In this study, the excited state charge distribution characteristics and fluorescence mechanism of HClO detection probes HN-ClO (weak fluorescence) and HN-ClO-F (strong fluorescence) probes were investigated based on density functional theory (DFT) and time-dependent density functional theory (TDDFT). The results of electrostatic potential (ESP) map and hole-electron analysis show that the HN-ClO and HN-ClO-F probes have obvious charge separation characteristics in the excited state. The excited state energy decomposition and Merz-Kollman charge analysis demonstrate the existence of distinct planar intramolecular charge transfer (PICT) features in HN-ClO and HN-ClO-F. Due to the strong charge coupling caused by the planar structure, the fluorescence of HN-ClO-F could occur. Furthermore, the weak fluorescence of HN-ClO is caused by inter-system crossing (ISC) between S1 and T1 state. Our result proves that the ICT process could exist in HN-ClO-F, but the PICT process does not cause fluorescence quenching, which have provided an excellent supplement to the mechanism of fluorescent probes. The conclusion is consistent with the fluorescence phenomenon observed in the experiment.


Assuntos
Elétrons , Corantes Fluorescentes , Espectrometria de Fluorescência , Eletricidade Estática
20.
Chemosphere ; 286(Pt 3): 131850, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34426281

RESUMO

Microbial electrochemical technologies (METs) have become a widely studied technology in recent years due to the need for sustainable biotechnologies. The scope of this work is the development of a mechanistic biokinetic model, based on first principles and a robust thermodynamic basis, to provide a theoretical accurate description of a MET system that would treat water contaminated with nitrate, the most common aquifer water pollutant, in absence of external electron donors. The model aims at describing the complex processes occurring including the competition between bioelectroactive and non-bioelectroactive reactions as well as the dynamics and kinetics of multiple bioelectrochemical reactions (both in series and in parallel) taking place in the same electrode. The bioelectrochemical denitrification of groundwater was then evaluated using the model as a case study. The evaluation focused on theoretical removal rates and energy expenditure, as well as the effect of key design parameters on the system's performance. The model successfully described how changes in the applied voltage and/or hydraulic retention time may impact the performance in terms of removal rate and effluent quality. The theoretical results also predict that the impact of electrode area is potentially more significant on the energy efficiency rather than on the effluent quality.


Assuntos
Água Subterrânea , Poluentes Químicos da Água , Desnitrificação , Elétrons , Nitratos/análise , Poluentes Químicos da Água/análise
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