Humic acids adsorption and decomposition on Mn2O3 and α-Al2O3 nanoparticles in aqueous suspensions in the presence of ozone

© 2018 Elsevier Ltd. The removal and decomposition of humic acids (HAs) in the presence of ozone and aqueous suspensions of Mn2O3 and a-alumina (Al2O3) nanoparticles was investigated. Mn2O3 presented lower BET specific surface area (15.6m2 g-1 vs 45.8m2 g-1) but a higher point of zero charge (PZC) (5.9 vs 4.2) than α-Al2O3. Solution pH played a key role in the adsorption of HAs and catalytic oxidation on the surface of α-Al2O3 and Mn2O3 nanopart icles. The adsorption capacity of α-Al2O3 at the natural pH of HAs in water (pH 5.5) was up to2.903 gHAs g-1, but no adsorption occurred onto the Mn2O3 nanoparticles, due to the unfavorable surface charge at pH 5.5. In consequence, although Mn2O3 was a more efficient catalyst (khet=0.7 L-1 min-1 g-1) than α-Al2O3 (khet=0.2 L-1 min-1 g-1) for the decomposition of O3, Mn2O3 did not exhibited catalytic action duringthe ozonation of HAs at pH 5.5. Instead, the Mn2O3 catalytic action was significant at pH equal to PZC (catalytic ate constant ratio k1-HAcat/k1-HA=1.562). Overall, α-Al2O3 exhibited the highest catalytic removal rate of HAs during ozonation (k1-HAcat/ k1-HA=2.298) due to favorable surface charge and larger specific surface area. The main mechanism for HAs removal in the presence of α-Al2O3 involves simultaneous adsorption of both HAs and O3, the reaction of ozone from the bulk solution and the catalytic decomposition of HAs on the solid surface by ROS, through complex series-parallel reactions. The α-Al2O3 dosage up to 0.5 g L-1 required to remove HAs by catalytic ozonation was significantly lower than in other studies employing granular activated carbon, iron coated zeolite or γ-alumina catalysts

Photo-assisted degradation of organic pollutant by CuFeS2 powder in RGB-LED reactors: A comprehensive study of band gap values and the relation between wavelength and electron-hole recombination

This work investigated the relation between direct band-gap conversion and excitation wavelength towards catalysis efficiency in red, green, and blue (RGB) light-emitting diode (LED) reactors. An integrating sphere and spectroradiometer system obtained the emission wavelengths of the operating modes spectra of the RGB-LED reactors. The effects of pH, catalyst, and H2O2 dosage were investigated, and the optimal photocatalysis conditions were found to be at pH 3, catalyst loading of 0.25 g L 1, 0.25 mmol L 1 of H2O2(aq) (30% v/v) for an initial model pollutant concentration of 75 mg L 1 and reaction time of 60 min. Under the higher intensity red mode (R1), the highest color removal rate was reached (88.1%), while in the conventional white light mode (WL), the decolorization efficiency remained 64.3%. Furthermore, the R1 mode showed a superior TOC removal than the WL mode, reaching the final removal efficiencies of 91.86% and 61.06%, respectively. Contrary to what has been reported, as the dominant wavelength of the irradiation source decreased, the efficiency also tended to decrease. The electronhole recombination increased as the irradiation mode decreased, and a work function (u) representing this phenomenon was obtained by the deduction of the relation between energy (E) and frequency (f) of the photons involved. Therefore, the insights presented in this work are valuable tools in increasing LED photocatalysis efficienc

Membrane Association Landscape of Myelin Basic Protein Portrays Formation of the Myelin Major Dense Line

Compact myelin comprises most of the dry weight of myelin, and its insulative nature is the basis for saltatory conduction of nerve impulses. The major dense line (MDL) is a 3-nm compartment between two cytoplasmic leaflets of stacked myelin membranes, mostly occupied by a myelin basic protein (MBP) phase. MBP is an abundant myelin protein involved in demyelinating diseases, such as multiple sclerosis. The association of MBP with lipid membranes has been studied for decades, but the MBP-driven formation of the MDL remains elusive at the biomolecular level. We employed complementary biophysical methods, including atomic force microscopy, cryo-electron microscopy, and neutron scattering, to investigate the formation of membrane stacks all the way from MBP binding onto a single membrane leaflet to the organisation of a stable MDL. Our results support the formation of an amorphous protein phase of MBP between two membrane bilayers and provide a molecular model for MDL formation during myelination, which is of importance when understanding myelin assembly and demyelinating conditions

Molecular structure and function of myelin protein P0 in membrane stacking

Compact myelin forms the basis of nerve insulation essential for higher vertebrates. Dozens of myelin membrane bilayers undergo tight stacking, and in the peripheral nervous system, this is partially enabled by myelin protein zero (P0). Consisting of an immunoglobulin (Ig)-like extracellular domain, a single transmembrane helix, and a cytoplasmic extension (P0ct), P0 harbours an important task in ensuring the integrity of compact myelin in the extracellular compartment, referred to as the intraperiod line. Several disease mutations resulting in peripheral neuropathies have been identified for P0, reflecting its physiological importance, but the arrangement of P0 within the myelin ultrastructure remains obscure. We performed a biophysical characterization of recombinant P0ct. P0ct contributes to the binding affinity between apposed cytoplasmic myelin membrane leaflets, which not only results in changes of the bilayer properties, but also potentially involves the arrangement of the Iglike domains in a manner that stabilizes the intraperiod line. Transmission electron cryomicroscopy of native full-length P0 showed that P0 stacks lipid membranes by forming antiparallel dimers between the extracellular Ig-like domains. The zipper-like arrangement of the P0 extracellular domains between two membranes explains the double structure of the myelin intraperiod line. Our results contribute to the understanding of PNS myelin, the role of P0 therein, and the underlying molecular foundation of compact myelin stability in health and disease

Membrane association landscape of myelin basic protein portrays formation of the myelin major dense line

Abstract Compact myelin comprises most of the dry weight of myelin, and its insulative nature is the basis for saltatory conduction of nerve impulses. The major dense line (MDL) is a 3-nm compartment between two cytoplasmic leaflets of stacked myelin membranes, mostly occupied by a myelin basic protein (MBP) phase. MBP is an abundant myelin protein involved in demyelinating diseases, such as multiple sclerosis. The association of MBP with lipid membranes has been studied for decades, but the MBP-driven formation of the MDL remains elusive at the biomolecular level. We employed complementary biophysical methods, including atomic force microscopy, cryo-electron microscopy, and neutron scattering, to investigate the formation of membrane stacks all the way from MBP binding onto a single membrane leaflet to the organisation of a stable MDL. Our results support the formation of an amorphous protein phase of MBP between two membrane bilayers and provide a molecular model for MDL formation during myelination, which is of importance when understanding myelin assembly and demyelinating conditions

Proceedings Of The 23Rd Paediatric Rheumatology European Society Congress: Part Two

PubMe