The proper characterization of aqueous brown carbon (BrC) species, their formation, and their light absorbance properties is critical to understanding the aggregate effect that they have on overall atmospheric aerosol climate forcing. The contribution of dark chemistry secondary organic aerosol (SOA) products from carbonyl-containing organic compounds (CVOCs) to overall aqueous aerosol optical properties is expected to be significant. However, the multiple, parallel pathways that take place within CVOC reaction systems and the differing chromophoricity of individual products complicates the ability to reliably model the chemical kinetics taking place. Here, we proposed an alternative method of representing UV-visible absorbance spectra as a composite of Gaussian lineshape functions to infer kinetic information. Multiple numbers of curves and different CVOC/ammonium reaction systems were compared. A model using three fitted Gaussian curves with magnitudes following first-order kinetics achieved an accuracy within 65.5% in the 205–300-nm range across multiple organic types and solution aging times. Asymmetrical peaks that occurred in low-200-nm wavelengths were decomposed into two overlapping Gaussian curves, which may have been attributable to different functional groups or families of reaction products. Component curves within overall spectra exhibited different dynamics, implying that the utilization of absorbance at a single reference wavelength to infer reaction rate constants may result in misrepresentative kinetics for these systems.
The modification of anode materials is important to enhance the power generation of microbial fuel cells (MFCs). A novel and cost-effective modified anode that is fabricated by dispersing manganese dioxide (MnO 2) and Halloysite nanotubes (HNTs) on carbon cloth to improve the MFCs' power production was reported. The results show that the MnO 2 /HNT anodes acquire more bacteria and provide greater kinetic activity and power density compared to the unmodified anode. Among all modified anodes, 75 wt% MnO 2 /HNT exhibits the highest electrochemical performance. The maximum power density is 767.3 mWm-2 , which 21.6 higher than the unmodified anode (631 mW/m 2). Besides, CE was improved 20.7, indicating that more chemical energy transformed to electricity. XRD and FTIR are used to characterize the structure and functional groups of the anode. CV scans and SEM images demonstrate that the measured power density is associated with the attachment of bacteria, the microorganism morphology differed between the modified and the original anode. These findings demonstrate that MnO 2 /HNT nanocomposites can alter the characteristics of carbon cloth anodes to effectively modify the anode for practical MFC applications.
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