Sandwiched naphthyl carbazole: Inversion Circularly Polarized Luminescence based on a pull-push electron valve strategy.

Inspired by circularly polarized luminescence (CPL), artificial CPL assembly has attracted intense attention. However, precise manipulation of chiral transfer from achiral and luminescent materials remains a formidable challenge. Two sandwiched carbazole and binaphthol derivatives composed of pyridine or trifluoride methyl benzene have been synthesized. Among R-1 and R-2, their spectra were found in the violet region, both in the solution and the film state. They exhibit the photoluminescence dissymmetry factors up to 1.4 × 10-3 for R-2 and an opposite value of -5.6 × 10-4 for R-1. Theoretical CPL and circular dichroism (CD) studies were in good agreement with the experimental data and deciphered their opposite signals by the transition electric and magnetic moment. Our study offers a strategy for studying the charge and chiral transfer.

Nano Fe3O4 improved the electron donating capacity of dissolved organic matter during sludge composting.

The effect of Fe3O4 nanoparticles (Fe3O4 NPs) on the electron transfer process in aerobic composting systems remains unexplored. In this study, we compared the electron transfer characteristics of DOM in sludge composting without additives (group CK) and with the addition of 50 mg/kg Fe3O4 NPs additive (group Fe). It was demonstrated that the electron transfer capacity (ETC) and electron donating capacity (EDC) of compost-derived DOM increased by 13%-29% and 40%-47%, respectively, with the addition of Fe3O4 NPs during sludge composting. Analyzing the composition and structure of DOM revealed that Fe3O4 NPs promoted the formation of humic acid-like substances and enhanced the aromatic condensation degree of DOM. Correlation analysis indicated that the increase in EDC of DOM was closely associated with the phenolic group in DOM and influenced by quinone groups and the degree of aromatization of DOM. The higher EDC and the structural evolution of DOM in group Fe reduced the bioaccessibility of Cu, Cr, Ni, Zn. This study contributes to a deeper understanding of the redox evolutionary mechanism of DOM in sludge composting and broadens the application of iron oxides additives.

Computational Insights into the Non-Heme Diiron Alkane Monooxygenase Enzyme AlkB: Electronic Structures, Dioxygen Activation, and Hydroxylation Mechanism of Liquid Alkanes.

Alkane monooxygenase (AlkB) is a membrane-spanning metalloenzyme that catalyzes the terminal hydroxylation of straight-chain alkanes involved in the microbially mediated degradation of liquid alkanes. According to the cryoEM structures, AlkB features a unique multihistidine ligand coordination environment with a long Fe-Fe distance in its active center. Up to now, how AlkB employs the diiron center to activate dioxygen and which species is responsible for triggering the hydroxylation are still elusive. In this work, we constructed computational models and performed quantum mechanics/molecular mechanics (QM/MM) calculations to illuminate the electronic characteristics of the diiron active center and how AlkB carries out the terminal hydroxylation. Our calculations revealed that the spin-spin interaction between two irons is rather weak. The dioxygen may ligate to either the Fe1 or Fe2 atom and prefers to act as a linker to increase the spin-spin interaction of two irons, facilitating the dioxygen cleavage to generate the highly reactive Fe(IV)═O. Thus, AlkB employs Fe(IV)═O to trigger the hydrogen abstraction. In addition, the previously suggested mechanism that AlkB uses both the dioxygen and Fe-coordinated water to perform hydroxylation was calculated to be unlikely. Besides, our results indicate that AlkB cannot use the Fe-coordinated dioxygen to directly trigger hydrogen abstraction.

Nitrogen-doped carbon dots boost microbial electrosynthesis via efficient extracellular electron uptake of acetogens.

This study investigated the molecular mechanism behind the highly efficient performance of nitrogen-doped carbon dots (NCDs)-assisted microbial electrosynthesis systems (MESs). The impact of NCDs (C:N precursor = 1:0.5-1:3) on acetogens was examined in the biocathode. The highest electrocatalytic performance was observed with NCDs1:1. The maximum acetate production rate of 1.9 ± 0.1 mM d-1 was achieved in NCDs1:1-modified MESs, which was 26.7-216.7 % higher than other MESs (0.6-1.5 mM d-1). With NCDs1:1 modified, the biocathode exhibited a 129.3-186.8 % increase in the abundance of Sporomusa, and 38.5-104.6 % increase in cytochrome expression (cydAB, cybH). Transcriptome confirmed that cytochromes played a crucial role in the extracellular electron uptake (EEU) of NCDs1:1-modified Sporomusa. NCDs1:1 enhanced EEU efficiency, thereby increasing the two H+-pumping steps and accelerating microbial CO2 fixation. These results provide valuable insights into increasing CO2 fixation by maximizing EEU efficiency in acetogens.

Femtosecond Dynamics of the Excited Primary Electron Donor in Reaction Centers of the Purple Bacterium Rhodobacter sphaeroides.

Femtosecond transient absorption spectroscopy was used to study the dynamics of the excited primary electron donor in the reaction centers of the purple bacterium Rhodobacter sphaeroides. Using global analysis and the interval method, we found a correlation between the vibrational coherence damping of the excited primary electron donor and the lifetime of the charge-separated state P+BA-, indicating the reversibility of electron transfer to the primary electron acceptor, the BA molecule. In the reaction centers, the signs of superposition of two electronic states of P were found for a delay time of less than 200 fs. It is suggested that the admixture value of the charge transfer state PA+PB- with the excited primary electron donor P* is about 24%. The results obtained are discussed in terms of the two-step electron transfer mechanism.

Versatile Bovine Serum Albumin as Ingenious Electron Operator-Enhanced Photoelectrochemical Biosensing for Ultrasensitive Detection of miRNA.

Bovine serum albumin (BSA) has been widely used in biosensors as a blocking agent. Herein, conformist BSA was first exploited as an ingenious operator to enhance the photocurrent response of (2Z,2'Z)-2,2'-(1,4-phenylene)bis(3-(4-(bis(4-methoxyphenyl)amino)phenyl)acrylonitrile) (TPDCN)-based photoelectrochemical (PEC) platform via manipulating the electron transfer process of the detection system. Concretely, the presence of target molecules triggered catalytic hairpin assembly reaction and subsequently powered terminal deoxynucleotidyl transferase-mediated signal amplification to produce the AgNP@BSA-DNA dendrimer nanostructure. After being treated with HNO3, a large amount of BSA could be released from the dendrimer nanostructure. When they were transferred to the TPDCN-based PEC platform, the photocurrent response of the biosensor was largely enhanced because BSA can manipulate the electrons of TPDCN via a well-matched energy level to form a new electron transfer track. Meanwhile, tryptophan (Trp) in BSA could be oxidized to quinone Trp-O under photoirradiation, which can facilitate the oxidation of ascorbate and generate more H+ to promote the migration of photogenerated electrons. As a result, the proposed PEC biosensor exhibits excellent analytical performance for detection of miRNA-21 (as a model target) over a wide linear range of 0.01 to 10,000 pM with detection limit as low as 4.7 fM. Overall, this strategy provides a new perspective on constructing efficient PEC biosensors, which expands the potential applications in bioanalysis and clinical diagnosis.

Sustainable Biomass Acts as an Electron Donor for Cr(VI) Reduction during the Subcritical Hydrothermal Process: Molecular Insights into the Role of Hydrochar and Liquid Compounds.

Heavy metal pollution is a critical environmental issue that has garnered significant attention from the international community. Subcritical hydrothermal liquefaction (HTL) as an emerging green technology has demonstrated remarkable promise in environmental remediation. However, there is limited research on the remediation of highly toxic Cr(VI) using HTL. This study reveals that the HTL reaction of biomass enables the simultaneous reduction and precipitation of Cr(VI). At 280 °C, the reduction of Cr(VI) was nearly complete, with a high reduction rate of 98.9%. The reduced Cr as Cr(OH)3 and Cr2O3 was primarily enriched in hydrochar, accounting for over 99.9% of the total amount. This effective enrichment resulted in the removal of Cr(VI) from the aqueous phase while simultaneously yielding clean liquid compounds like organic acids and furfural. Furthermore, the elevated temperature facilitated the formation of Cr(III) and enhanced its accumulation within hydrochar. Notably, the resulting hydrochar and small oxygenated compounds, especially aldehyde, served as electron donors for Cr(VI) reduction. Additionally, the dissolved Cr facilitated the depolymerization and deoxygenation processes of macromolecular compounds with lignin-like structures, leading to more small oxygenated compounds and subsequently influencing Cr(VI) reduction. These findings have substantial implications for green and sustainable development.

Electron beam irradiation developed cinnamon oil- (polyvinyl alcohol/gum tragacanth)/graphene oxide dressing hydrogels: Antimicrobial and healing assessments.

This study aimed to develop hydrogel dressings for wound healing composed of gum tragacanth (TG) and polyvinyl alcohol (PVA) loaded with Graphene oxide (GO) and Cinnamon oil (CMO) using electron beam irradiation. The impact of the preparation conditions and the incorporation of GO and CMO on the characteristic properties of the prepared CMO-(PVA/TG)-GO wound dressings was evaluated. The healing-related characteristics were assessed, including fluid absorption and retention, water vapor transmission rate (WVTR), hemolytic assay, and antimicrobial potential. Wound healing efficacy was evaluated using a scratch wound healing assay. FTIR analysis verified the chemical structure, whereas scanning electron microscopy demonstrated an appropriate porosity structure necessary for optimal wound healing. The gel content increases with the initial total polymer concentration and the irradiation dose increases. Higher GO and CMO content improve the gel content and decreases swelling. WVTR decreases with the rise in CMO content. In vitro, cytotoxicity and hemolytic potency assessments confirmed their biocompatibility. The incorporation of GO and CMO enhances the antimicrobial activity and wound-healing capability. Based on the above findings, CMO-(PVA/TG)-GO dressings show promising potential as candidates for wound care.

New insights and enhancement mechanisms of activated carbon in autotrophic denitrification system utilizing zero-valent iron as indirect electron donors.

Zero-valent iron acts as an indirect electron donor, supplying ferrous iron for the nitrate-dependent ferrous oxidation (NDFO) process. The addition of activated carbon (AC) increased the specific NDFO activity in situ and ex situ by 0.4 mg-N/(d·g VSS) and 2.2 mg-N/(d·g VSS), respectively, due to the enrichment of NDFO bacteria. Furthermore, AC reduced the nitrous oxide emission potential of the sludge, a mechanism that metagenomic analysis suggests may act as a cellular energy storage strategy. During a 196-day experiment, a total nitrogen removal efficiency of 53.7 % was achieved, which may be attributed to the upregulation of key genes involved in iron oxidation and denitrification. Based on these findings, a model involving pilin, 'nanowires,' and a cyc2/?→/(FoxE→FoxY)/?→cymA/Complex III/?-mediated pathway for extracellular electron uptake was proposed. Overall, this work provides a feasible strategy for enhancing the nitrogen removal performance of the ZVI-NDFO process.

Calcined pyrite accelerates sulfur metabolic and electron transfer in driving targeted microbial fuel cell denitrification.

The sulfur powder as electron donor in driving dual-chamber microbial fuel cell denitrification (S) process has the advantages in economy and pollution-free to treat nitrate-contained groundwater. However, the low efficiency of electron utilization in sulfur oxidation (ACE) is the bottleneck to this method. In this study, the addition of calcined pyrite to the S system (SCP) accelerated electron generation and intra/extracellular transfer efficiency, thereby improving ACE and denitrification performance. The highest nitrate removal rate reached to 3.55 ± 0.01 mg N/L/h in SCP system, and the ACE was 103 % higher than that in S system. More importantly, calcined pyrite enhanced the enrichment of functional bacteria (Burkholderiales, Thiomonas and Sulfurovum) and functional genes which related to sulfur metabolism and electron transfer. This study was more effective in removing nitrate from groundwater without compromising the water quality.

Analysis of structural defects and their influence on red-emitting γ-Al2O3:Mn4+,Mg2+ nanowires using positron annihilation spectroscopy.

The present paper reported on the analysis of structural defects and their influence on the red-emitting γ-Al2O3:Mn4+,Mg2+ nanowires using positron annihilation spectroscopy (PAS). The nanowires were synthesized by hydrothermal method and low-temperature post-treatment using glucose as a reducing agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and photoluminescence excitation (PLE) were utilized, respectively, for determining the structural phase, morphology and red-emitting intensity in studied samples. Three PAS experiments, namely, positron annihilation lifetime (PAL), Doppler broadening (DB), and electron momentum distribution (EMD), were simultaneously performed to investigate the formations of structural defects in synthesized materials. Obtained results indicated that the doping concentration of 0.06% was optimal for the substitution of Mn4+ and Mg2+ to two Al3+ sites and the formation of oxygen vacancy (VO)-rich vacancy clusters (2VAl + 3VO) and large voids (~0.7 nm) with less Al atoms. Those characteristics reduced the energy transfer between Mn4+ ions, thus consequently enhanced the PL and PLE intensities. Moreover, this optimal doping concentration also effectively controlled the size of nanopores (~2.18 nm); hence, it is expected to maintain the high thermal conductivity of γ-Al2O3 nanowire-phosphor. The present study, therefore, demonstrated a potential application of γ-Al2O3 nanowire-phosphor in fabricating the high-performance optoelectronic devices.

Investigation of a novel 2.5 MV sintered diamond target beam for intracranial linac-based stereotactic treatments.

Purpose. This work investigates the small-field dosimetric characteristics of a 2.5 MV sintered diamond target beam and its feasibility for use in linac-based intracranial stereotactic treatments. Due to the increased proportion of low energy photons in the low-Z beam, it was hypothesized that this novel beam would provide sharper dose fall-off compared to the 6 MV beam owing to the reduced energy, and therefore range, of secondary electrons.Methods. Stereotactic treatments of ocular melanoma and trigeminal neuralgia were simulated for 2.5 MV low-Z and 6 MV beams using Monte Carlo to calculate dose in a voxelized anatomical phantom. Two collimation methods were investigated, including a 5 × 3 mm2HDMLC field and a 4 mm cone to demonstrate isolated and combined effects of geometric and radiological contributions to the penumbral width.Results. The measured 2.5 MV low-Z dosimetric profiles demonstrated reduced penumbra by 0.5 mm in both the inline and crossline directions across all depths for both collimation methods, compared to 6 MV. In both treatment cases, the 2.5 MV low-Z beam collimated with the 4 mm cone produced the sharpest dose fall off in profiles captured through isocenter. This improved fall-off resulted in a 59% decrease to the maximum brainstem dose in the trigeminal neuralgia case for the 2.5 MV low-Z MLC collimated beam compared to 6 MV. Reductions to the maximum and mean doses to ipsilateral and contralateral OARs in the ocular melanoma case were observed for the 2.5 MV low-Z beam compared to 6 MV with both collimation methods.Conclusions. While the low dose rate of this novel beam prohibits immediate clinical translation, the results of this study support the further development of this prototype beam to decrease toxicity in intracranial SRS treatments.

Exploring the Bonding Nature of Iron(IV)-Oxo Species through Valence Bond Calculations and Electron Density Analysis.

Compound I (Cpd I) plays a pivotal role in substrate transformations within the catalytic cycle of cytochrome P450 enzymes (P450s). A key constituent of Cpd I is the iron(IV)-oxo unit, a structural motif also found in other heme enzymes and nonheme enzymes. In this study, we performed ab initio valence bond (VB) calculations, employing the valence bond self-consistent field (VBSCF) and breathing orbital valence bond (BOVB) methods, to unveil the bonding nature of this vital "Fe(IV)═O″ unit in bioinorganic chemistry. Comparisons were drawn with the triplet O2 molecule, which shares some electronic characteristics with iron(IV)-oxo. Additionally, Cpd I models of horseradish peroxidase (HRP) and catalase (CAT) were analyzed to assess the proximal ligand effect on the electronic structure of iron(IV)-oxo. Our VB analysis underscores the significant role of noncovalent resonance effects in shaping the iron(IV)-oxo bonding. The resonance stabilization within the π and σ frameworks occurs to comparable degrees, with additional stabilization resulting from resonance between VB structures from these frameworks. Furthermore, we elucidated the substantial influence of proximal and equatorial ligands in modulating the relative significance of different VB structures. Notably, in the presence of these ligands, iron(IV)-oxo is better described as iron(III)-oxyl or iron(II)-oxygen, displaying weak covalent character but enhanced by resonance effects. Although both species exhibit diradicaloid characters, resonance stabilization in iron(IV)-oxo is weaker than in O2. Further exploration using the Laplacian of electron density shows that, unlike O2, which exhibits a charge concentration region between its two oxygen atoms, iron(IV)-oxo species display a charge depletion region.

Electronic properties of single vacancy defect in boron nitride nanoribbons with edge perturbation.

Two-dimensional material hexagonal boron nitride (h-BN), and its one-dimensional thin strips, boron nitride nanoribbons (BNNRs) are electrically insulating with high thermal stability, making them excellent thermal conductors suitable for high-temperature application. BNNRs are wide bandgap semiconductors with bandgaps ranging from 4 to 6 eV. This study investigates the electronic properties of BNNRs with single vacancy defects in armchair and zigzag configurations. The nearest-neighbour tight-binding model and numerical method were used to simulate the electronic properties of BNNRs with a single vacancy, including band structure and local density of states. The alpha and beta matrices were adjusted to account for missing boron or nitrogen atoms. Furthermore, a small perturbations were introduced to model the effects of impurities and edge imperfections. The simulation result from this work was compared with pristine BNNRs to examine the impact of a single vacancy on their electronic properties. The findings reveal that both armchair and zigzag BNNRs with single vacancy defects exhibit distorted band structures and local density of states due to the delocalization of pz orbitals. The valence bands show a higher concentration of nitrogen, while the conduction bands are richer in boron. These findings provide insights into how vacancy defects and edge perturbations can influence the electronic properties of BNNRs, which can guide the design and optimization of BNNR-based electronic devices in future research.

Understanding Variations in Ferrate Detection through the ABTS Method in the Presence of Electron-Rich Organic Compounds.

The chromogenic reaction between 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and ferrate [Fe(VI)] has long been utilized for Fe(VI) content measurement. However, the presence of electron-rich organic compounds has been found to significantly impact Fe(VI) detection using the ABTS method, leading to relative errors ranging from ∼88 to 100%. Reducing substances consumed ABTS•+ and resulted in underestimated Fe(VI) levels. Moreover, the oxidation of electron-rich organics containing hydroxyl groups by Fe(VI) could generate a phenoxyl radical (Ph•), promoting the transformation of Fe(VI) → Fe(V) → Fe(IV). The in situ formation of Fe(IV) can then contribute to ABTS oxidation, altering the ABTS•+:Fe(VI) stoichiometry from 1:1 to 2:1. To overcome these challenges, we introduced Mn(II) as an activator and 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic agent for Fe(VI) detection. This Mn(II)/TMB method enables rapid completion of the chromogenic reaction within 2 s, with a low detection limit of approximately 4 nM and a wide detection range (0.01-10 µM). Importantly, the Mn(II)/TMB method exhibits superior resistance to reductive interference and effectively eliminates the impact of phenoxyl-radical-mediated intermediate valence iron transfer processes associated with electron-rich organic compounds. Furthermore, this method is resilient to particle interference and demonstrates practical applicability in authentic waters.

Prediction of the treatment effect of FLASH radiotherapy with synchrotron radiation from the Circular Electron-Positron Collider (CEPC).

The Circular Electron-Positron Collider (CEPC) in China can also work as an excellent powerful synchrotron light source, which can generate high-quality synchrotron radiation. This synchrotron radiation has potential advantages in the medical field as it has a broad spectrum, with energies ranging from visible light to X-rays used in conventional radiotherapy, up to several megaelectronvolts. FLASH radiotherapy is one of the most advanced radiotherapy modalities. It is a radiotherapy method that uses ultra-high dose rate irradiation to achieve the treatment dose in an instant; the ultra-high dose rate used is generally greater than 40 Gy s-1, and this type of radiotherapy can protect normal tissues well. In this paper, the treatment effect of CEPC synchrotron radiation for FLASH radiotherapy was evaluated by simulation. First, a Geant4 simulation was used to build a synchrotron radiation radiotherapy beamline station, and then the dose rate that the CEPC can produce was calculated. A physicochemical model of radiotherapy response kinetics was then established, and a large number of radiotherapy experimental data were comprehensively used to fit and determine the functional relationship between the treatment effect, dose rate and dose. Finally, the macroscopic treatment effect of FLASH radiotherapy was predicted using CEPC synchrotron radiation through the dose rate and the above-mentioned functional relationship. The results show that the synchrotron radiation beam from the CEPC is one of the best beams for FLASH radiotherapy.

The critical role of electron donating rate of pyrogenic carbon in mediating the degradation of phenols in the aquatic environment.

Phenols are the widely detected contaminants in the aquatic environment. Pyrogenic carbon (PyC) can mediate phenols degradation, but the specific properties of PyC or phenols influencing this reaction remain unknown. The present study investigated the kinetic process and mechanism of removal of various phenols by different PyC in aqueous phase system. To avoid the impact of the accumulated degradation byproducts on the overall reaction, we conducted a short-term experiment, quantified adsorption and degradation, and obtained reaction rate constants using a two-compartment first-order kinetics model. The adsorption rate constants (ka) of phenols by PyC were 10-220 times higher than degradation rate constants (kd), and they were positively correlated. Interestingly, no correlation was found between kd and common PyC properties, including functional groups, electron transfer capacities, and surface properties. Phenols were primarily attacked by •OH in the adsorbed phase. But neither the instantly trapped •OH, nor the accumulated •OH could explain phenol degradation. Chemical redox titration revealed that the electron transfer parameters, such as the electron donating rate constant (kED) of PyC, correlated well with kd (r>0.87, P < 0.05) of phenols. Analysis of 13 phenols showed that Egap and ELUMO negatively correlated with their kd, confirming the importance of the electronic properties of phenols to their degradation kinetics. This study highlights the importance of PyC electron transfer kinetics parameters for phenols degradation and manipulation of PyC electron transfer rate may accelerate organic pollutant removal, which contributes to a deeper understanding of the environmental behavior and application of PyC systems.

Enhancing the antioxidant potential of ESIPT-based naringenin flavonoids based on excited state hydrogen bond dynamics: A theoretical study.

Exploring antioxidant potential of flavonoid derivatives after ESIPT process provides a theoretical basis for discovering compounds with higher antioxidant capacity. In this work, employing the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods, the antioxidant potential of two citrus-derived naringenin flavonoids after ESIPT process is explored. Based on studies of ESIPT process including IMHB intensity variations, potential energy curves, and transition state, these molecules exist only in enol and keto⁎ forms due to ultra-fast ESIPT. The HOMOs are utilized to explore electron-donating capacity, demonstrating that the molecules in keto⁎ form is stronger than that in enol form. Furthermore, the atomic dipole moment corrected Hirshfeld population (ADCH) and Fukui functions indicate that the sites attacked by the electrophilic free radical of the two molecules in the keto⁎ form are O3 and O5' respectively, and both are more active than in the enol form. Overall, a comprehensive consideration of the ESIPT process and antioxidant potential of flavonoid derivatives will facilitate the exploration and design of substances with higher antioxidant capacity.

Electron Delocalization Disentangles Activity-Selectivity Trade-Off of Transition Metal Phosphide Catalysts in Oxidative Desulfurization.

Breaking the activity-selectivity trade-off has been a long-standing challenge in catalysis. Here, we proposed a nanoheterostructure engineering strategy to overcome the trade-off in metal phosphide catalysts for the oxidative desulfurization (ODS) of fuels. Experimental and theoretical results demonstrated that electron delocalization was the key driver to simultaneously achieve high activity and high selectivity for the molybdenum phosphide (MoP)/tungsten phosphide (WP) nanoheterostructure catalyst. The electron delocalization not only promoted the catalytic pathway transition from predominant radicals to singlet oxygens in H2O2 activation but also simultaneously optimized the adsorption of reactants and intermediates on Mo and W sites. The presence of such dual-enhanced active sites ideally compensated for the loss of activity due to the nonradical catalytic pathway, consequently disentangling the activity-selectivity trade-off. The resulting catalyst (MoWP2/C) unprecedentedly achieved 100% removal of thiophenic compounds from real diesel at an initial concentration of 2676 ppm of sulfur with a high turnover frequency (TOF) of 105.4 h-1 and a minimal O/S ratio of 4. This work provides fundamental insight into the structure-activity-selectivity relationships of heterogeneous catalysts and may inspire the development of high-performance catalysts for ODS and other catalytic fields.

Ultrahigh carbon utilization in symbiotic biofilm-sludge denitrification systems using polymers as sole electron donors.

The polymer-based denitrification system is an effective nitrate removal process for treating low carbon/nitrogen wastewater. However, in polymer denitrification systems, carbon used for the denitrification reaction is weakly targeted. Improving the efficiency of carbon utilization in denitrification is important to reduce carbon wastage. In this study, a symbiotic biofilm-sludge denitrification system was constructed using polycaprolactone as electron donors. Results show that the carbon release amount in 120 days was 85.32±0.46 g, and the unit mass of polycaprolactone could remove 1.55±0.01 g NO3--N. Meaningfully, the targeted carbon utilization efficiency for denitrification could achieve 79%-85%. The quantitative results showed that the release of electron donors can be well matched to the demand for electron acceptors in the biofilm-sludge denitrification system. Overall, the symbiotic system can improve the nitrate removal efficiency and reduce the waste of carbon source.