Excitation-emission matrix (EEM) fluorescence spectroscopy is a powerful tool for the characterization of dissolved organic matter (DOM) in wastewater systems. It is of particular value if its ...utility could be extended by connecting the spectral features to hydrophobicity, one of the fundamental physicochemical properties of DOM. In this study, we employed a DAX-8 resin column to fractionate the hydrophobic/philic components of DOM and determine the relative degree of hydrophobicity by adjusting the critical retention factor (k’cr, the ratio of treated water sample volume to column volume). A higher k’cr would result in a higher hydrophobicity of the column effluent. At different k’cr values (5, 10, 25, 50, 100, and 200), the EEM characteristics of the obtained DOM components were inspected, including overall properties (average fluorescence per total organic carbon and UV absorbance), regional properties (fluorescence regional integration (FRI) and its secondary parameters), and energy-related properties (energy level of the excited states, Stokes shift for relaxation of the excited states, and fluorescence lifetime). In case studies of a wastewater membrane bioreactor and an oxidation ditch, plenty of the EEM properties varied significantly with logk’cr (r > 0.9, p < 0.05). The average fluorescence per UV absorbance (reflecting quantum yield), fluorescence proportion at Stokes shift ≥ 1.1 μm−1, and some secondary FRI parameters presented the best linear fitting with logk’cr, suggesting a smooth variation of the π-conjugated structures with the relative degree of DOM hydrophobicity. This may help to further understand the relationship between EEM fingerprints and DOM hydrophobicity.
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•Fluorescence EEM fingerprints vary with the relative degree of DOM hydrophobicity.•Critical retention factor (k’cr) of DAX column regulates the relative hydrophobicity.•A set of intensity, wavelength and energy parameters are explored from EEM spectra.•Fluorescence quantum yield, excitation energy, and Stokes shift correlate with k’cr.•Some EEM parameters exhibit good linear regression with logk’cr, with R2 > 0.95.
This study aimed to investigate the vitamin D deficiency of patients with BPPV recurrence and to evaluate the differences of 25-hydroxy vitamin D (25(OH)D) and serum calcium levels among gender and ...age categories.
This cross-sectional study enrolled patients with BPPV. The diagnosis of BPPV was based on positional nystagmus and vertigo induced by certain head positions (The Dix-Hallpike maneuver and head roll tests). All patients' age, serum 25(OH)D, calcium measurements and recurrence data were collected and analyzed.
The median of 25(OH)D was 15.32 (IQR 10.61, 20.90) ng/ml. The recurrent group showed lower 25(OH)D levels than that of non-recurrent group 13.28 (IQR 9.47, 17.57) ng/ml vs 16.21 (IQR 11.49, 21.13) ng/ml. There were significant differences of 25(OH)D levels among age categories. The proportion of vitamin D deficiency in patients ≥60 years old was lower than that in the other two groups.
Our study suggested that BPPV patients had a decreased 25(OH)D level and a high incidence of vitamin D deficiency. The 25(OH)D level of recurrent BPPV patients was lower than that in non-recurrent ones. Among them, the elderly group (≥60 years) took the preponderance, which had the lowest incidence of vitamin D deficiency and the highest incidence of vitamin D sufficiency.
•UV/fluorescence spectra and quantum yield distinguished TB-EPS from LB- and S-EPS.•TB-/LB-/S-EPS had identifiable characteristic regions on an FEEM-FQ contour map.•An MLR-VPA model quantified ...spectral contributions of EPS's PS/PN/HA components.•An FEEM-mapping technique signified PS/PN/PA interactions in layered EPS structure.•UHPLC-MS evidenced the hybridization of PS/PN/PA fragments in the EPS structure.
Extracellular polymeric substances (EPS), with a stratified structure including tightly-bound EPS (TB-EPS), loosely-bound EPS (LB-EPS), and soluble EPS (S-EPS) surrounding the microbial cells, are known to vitally affect the physicochemical and biological functions of activated sludge in wastewater treatment. Polysaccharides (PS), proteins (PN), and humic acids (HA) are key components of EPS but their roles in constructing the multi-layer architecture are still unclear. This study explored the EPS characteristics in relation to the components using spectroscopic fingerprinting techniques. Ultraviolet-visible (UV-vis) spectra demonstrated stark difference between TB-EPS and other EPS. Fluorescence excitation-emission matrix (FEEM) and apparent quantum yield revealed further detailed differences. Fluorescence quotient analysis highlighted the dominance of TB-EPS, LB-EPS, and S-EPS in the excitation/emission wavelength (Ex/Em) region of Em = 350–400 nm, Em > 400 nm, and low-Stokes shift band (Em − Ex < 25 nm), respectively. Wavelength-wise prediction of the FEEM intensity was achieved through multiple linear regression against the chemical composition and variance partitioning analysis witnessed binary interactions of PS×HA and PS×PN in S-EPS, PN×HA and PS×PN in LB-EPS, and ternary interaction of PS×PN×HA in TB-EPS as well as the wavelength-specific fluorescence responses of these interactions. Further, X-ray photoelectron spectroscopy, infrared spectra, and circular dichroism spectra corroborated the differences in primary, secondary, and tertiary structures across the EPS layers. Ultrahigh-performance liquid chromatography-mass spectrometry detected molecular fragments confirming the multi-component hybridization among PS, PN, and HA. This study demonstrates a spectroscopic approach to sensitively fingerprint the fine structure of EPS, which has the potential for rapid monitoring of EPS and related sludge properties in wastewater treatment systems.
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Hydrophobicity and molecular weight (MW) are two fundamental properties of dissolved organic matter (DOM) in wastewater treatment systems. This study proposes fluorescence Stokes shift and specific ...fluorescence intensity (SFI) as novel indicators of hydrophobicity and MW. These indicators originate from the energy gap and photon efficiency of the fluorescence process and can be readily extracted from a fluorescence excitation–emission matrix (EEM). The statistical linkages between these indicators and hydrophobicity/MW were explored through investigation of DOM across 10 full-scale membrane bioreactors treating municipal wastewater. Stokes shift was found to exhibit a general rule among the hydrophobicity components in the order of hydrophilic substances (HIS) < hydrophobic acids (HOA) < hydrophobic bases (HOB). The Stokes shift of 1.2 μm–1 is a critical border, above which the relative fluorescence correlated significantly with the HOA-related content (Pearson’s r = 0.8). With regard to MW distribution (<1, 1–10, 10–100, and >100 kDa), SFI was found to be the most sensitive to the change of MW of <1 kDa proportion, especially at the excitation/emission wavelengths of 200–320/310–550 nm (r > 0.9). Hydrophobicity-related π conjugation and MW-dependent light exposure might be responsible for the correlations. These fluorescence indicators may be useful for convenient monitoring of DOM in wastewater treatment systems.
* Principles and methods for fluorescence EEM are systematically outlined. * Fluorophore peak/region/component and energy information can be extracted from EEM. * EEM can fingerprint the ...physical/chemical/biological properties of DOM in MBRs. * EEM is useful for tracking pollutant transformation and membrane retention/fouling. * Improvements are still needed to overcome limitations for further studies.
The membrane bioreactor (MBR) technology is a rising star for wastewater treatment. The pollutant elimination and membrane fouling performances of MBRs are essentially related to the dissolved organic matter (DOM) in the system. Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy, a powerful tool for the rapid and sensitive characterization of DOM, has been extensively applied in MBR studies; however, only a limited portion of the EEM fingerprinting information was utilized. This paper revisits the principles and methods of fluorescence EEM, and reviews the recent progress in applying EEM to characterize DOM in MBR studies. We systematically introduced the information extracted from EEM by considering the fluorescence peak location/intensity, wavelength regional distribution, and spectral deconvolution (giving fluorescent component loadings/scores), and discussed how to use the information to interpret the chemical compositions, physiochemical properties, biological activities, membrane retention/fouling behaviors, and migration/transformation fates of DOM in MBR systems. In addition to conventional EEM indicators, novel fluorescent parameters are summarized for potential use, including quantum yield, Stokes shift, excited energy state, and fluorescence lifetime. The current limitations of EEM-based DOM characterization are also discussed, with possible measures proposed to improve applications in MBR monitoring.
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•Pore blocking and gel/cake fouling potentials were tested during 151-d run of AnMBR.•The fouling potential significantly correlated with 6 UV–vis and 15 EEM indexes.•Fluorescence EEM ...indexes exhibited overall better correlation than UV–vis indexes.•FTIR/XPS/UHPLC-MS highlighted polysaccharide-hybrid foulants with spectral activity.•Combined use of FIP1 and UV280 well predicted the fouling potentials with R2 > 0.75.
The application of anaerobic membrane bioreactors (AnMBRs) for wastewater treatment is seriously challenged by membrane fouling. Online monitoring of the fouling potential would promisingly support smart control of fouling. The monitoring is most likely achievable using spectroscopic methods, but the spectroscopic indicators are yet to be qualified. In this study, 11 ultraviolet (UV) indicators, 19 fluorescence excitation-emission matrix indicators and 2 infrared scattering indicators were screened during 151-day operation of a lab-scale AnMBR. The critical filtration volume for flux declining to 50% or 25% (V0.5 or V0.25) and the specific resistance (Kcf) were employed as benchmarks of fouling potential for initial pore blocking and subsequent gel/cake layer growth. The 254 and 280 nm UV absorbances (UV254 and UV280) displayed significant correlation coefficients of 0.57–0.77 with the fouling indexes, while the Peak 1 and Peak 2 fluorescence intensities (FIP1 and FIP2) displayed 0.84–0.92. Statistical variance partitioning and Fourier transform infrared analyses showed that polysaccharide-like solutes were mostly responsible for fouling and were UV/fluorescence-sensitive due to the chromophoric/fluorophoric segments they carried. X-ray photoelectron spectra revealed a correlation of fouling and fluorescence with the O=C-(R N O) content. Ultrahigh-performance liquid chromatography-mass spectrometry substantiated the direct connection of sugar units with chromophoric/fluorophoric groups. Regression models were then established to predict the fouling potential during AnMBR operation. The combined use of FIP1 and UV280 achieved the best prediction of V0.5, V0.25 and Kcf with R2 = 0.763, 0.891 and 0.845, respectively, showing the viability of spectroscopic sensing in membrane bioreactor applications.
As a group of attractive photoelectromagnetic and catalytic functional materials, metal oxychlorides have been attracting attention for electrochemical energy storage in rechargeable chloride ion ...battery (CIB) systems recently. Their application, however, is limited by the complicated synthesis and/or poor cycling stability. Herein, a facile strategy using vacuum impregnation and subsequent thermal decomposition at mild conditions has been developed to synthesize the FeOCl/CMK-3 nanocomposite material. Benefiting from the nanoconfined structure, a high-performance FeOCl/CMK-3 cathode, which has a high discharge capacity of 202 mAh g–1, superior cycling stability, and significantly improved charge transfer and chloride ion diffusion, is achieved. The electrolyte component is found to show a high affinity with the chlorine layer in the FeOCl phase, inducing evident expansion of the FeOCl layers along the b-axis direction and thus boosting a new potential liquid exfoliation approach for preparing 2D FeOCl material. Importantly, reversible electrochemical reactions of the FeOCl cathode material based on the redox reactions of iron species and chloride ion transfer are revealed.
Two-dimensional materials are easily affected by radiation. So far, there is no work to predict the neutron irradiation effects of AA bilayer graphene. Furthermore, the differences and comparisons of ...various properties between monolayer graphene and AA bilayer graphene after irradiation in the approximately same neutron environment have not been reported. In this study, the neutron irradiation processes on monolayer graphene and AA bilayer graphene were simulated in ab initio molecular dynamics. The mechanical, and optoelectronic properties of monolayer and AA bilayer systems before and after irradiation were calculated using the method based on density functional theory. The results indicate that the AA bilayer system is more resistant to neutron irradiation than the monolayer system. The bandgap of the monolayer (bilayer) system after irradiation will reach the order of 0.1 eV. This article has important value in exploring the methods of radiation reinforcement technology for carbon-based devices.
Cancers heavily threaten human life; therefore, a high‐accuracy diagnosis is vital to protect human beings from the suffering of cancers. While biopsies and imaging methods are widely used as current ...technologies for cancer diagnosis, a new detection platform by metabolic analysis is expected due to the significant advantages of fast, simple, and cost‐effectiveness with high body tolerance. However, the signal of molecule biomarkers is too weak to acquire high‐accuracy diagnosis. Herein, precisely engineered metal–organic frameworks for laser desorption/ionization mass spectrometry, allowing favorable charge transfer within the molecule–substrate interface and mitigated thermal dissipation by adjusting the phonon scattering with metal nodes, are developed. Consequently, a surprising signal enhancement of ≈10 000‐fold is achieved, resulting in diagnosis of three major cancers (liver/lung/kidney cancer) with area‐under‐the‐curve of 0.908–0.964 and accuracy of 83.2%–90.6%, which promises a universal detection tool for large‐scale clinical diagnosis of human cancers.
A precisely engineered metal–organic framework (MOF) is developed as the matrix for laser desorption/ionization mass spectrometry for the acquisition of serum metabolic fingerprints. Fe‐MOF‐UL with favorable charge transfer and mitigated thermal dissipation achieves ≈10 000‐fold signal enhancement and leads to high‐accuracy diagnosis of three major cancers, promising a universal detection tool for human cancers.
While the contact angle is a well-applied indicator of membrane hydrophobicity and surface energy, the interference of surface roughness and porosity in contact angle measurement and surface energy ...calculation has been long neglected in the field of porous membrane study. We propose an improved method to straightforwardly derive the surface energy of the porous membrane from contact angles with the interference effect corrected. A linearized model was established combining the Young–Dupré and Cassie–Baxter equations, from which the surface energy (Lifshitz–van der Waals and Lewis acid/base components) and roughness index (surface area difference) can be solved simultaneously at a given porosity using contact angles measured with a set of standard polar/nonpolar test liquids. The model solution was examined using hydrophilic microfiltration membranes with different pore morphologies (including perforated plate-like PCTE, irregular particulate bed-like PVDF, and fibrous mesh-like PTFE membranes), with the robustness of the results evaluated via Monte Carlo simulation. In comparison with the verified results of the model solution, it was found that the Lifshitz–van der Waals Lewis acid/base energy values for the tested membranes would deviate by 50–87, 30–160, and 52–97%, respectively, if surface roughness and porosity were neglected in the calculation. The profound effect of roughness and porosity on surface energy determination was further confirmed via theoretical analysis of the Young–Dupré and Cassie–Baxter relationships. This improved approach may apply to the surface energy characterization of hydrophilic rough porous membranes (e.g., hydrophilic microfiltration membranes).
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