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Enhanced catechol oxidation by heterogeneous biomimetic catalysts immobilized on clay minerals.
No full textOxidative and photo-oxidative polymerization of humic suprastructures by heterogeneous biomimetic catalysis.
No full textThe meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of manganese(III) chloride [Mn-(TDCPPS)Cl] biomimetic catalyst immobilized on spacer-functionalized kaolinite clay mineral was employed in the oxidative coupling reaction of a dissolved humic acid (HA) suprastructure with either chemical (H2O2) or UV-light oxidation. The changes in molecular size of humic matter subjected to catalyzed oxidative reaction were followed by high-performance size exclusion chromatography (HPSEC) with UV-vis and refractive index (RI) detectors in series, and by thermogravimetric (TGA) analysis. Both the enhanced molecular size shown by differences between HPSEC chromatograms of humic reaction mixtures at either pH 6 or 3.5 and the increase of thermogravimetric stability suggest that the heterogeneous biomimetic catalysis promoted the stabilization of humic conformations by new intermolecular covalent bonds during oxidative coupling. The similarity between chemical and light-induced oxidation results suggests potential multiple applications of the kaolinite-supported heterogeneous catalyst in controlling the reactivity of natural organic matter within biogeochemical cycles and environmental reactions
In situ photo-polymerization of soil organic matter by heterogeneous nano-TiO2 and biomimetic metal-porphyrin catalysts
No full textTwo oxidative catalytic systems, titanium dioxide (TiO2) nanoparticles and a biomimetic Mn-porphyrin linked to montmorillonite through a spacer (MnP-M), were used to photo-polymerize soil organic matter (SOM) directly in situ on soil, with the aim to sequester organic carbon (OC) and reduce CO2 emissions from soil. We first validated, by infrared spectroscopy, thermogravimetric analysis (TGA), and proton spin–lattice relaxation time (T1ρH) in 13C cross-polarization magic angle spinning (13C CPMAS) nuclear magnetic resonance (NMR) spectra, the capacity of the nano-TiO2 catalyst to photo-oxidatively couple humic molecules together by covalent bonds, as already proved under MnP-M. Both catalysts turn the loosely associated humic superstructures into more stable and larger molecular masses through a photo-oxidative free radical coupling mechanism. Then, the addition of either nano-TiO2 or MnP-M to soil induced an in situ photo-polymerization of SOM, since exposure of catalyst-treated soils to solar light determined a significant reduction of respired CO2 and an increase in thermal stability of humic components and, consequently, in SOC content. This suggests that both nano-TiO2 and immobilized metal-porphyrin photo-catalysts effectively promote OC sequestration in soil and reduction of CO2 emissions from soil to atmosphere. Soil treatments with heterogeneous photo-catalysts may become a promising technology for the development of future agricultural practices aimed to increase SOM stabilization and contribute to mitigate global climate change
Conformational changes of dissolved humic and fulvic superstructures with progressive iron complexation.
No full textDegradation of 2, 4-dichlorophenol and coupling into humic matter by oxidative biomimetic catalysis with iron-porphyrin.
No full textEnhanced washing of polycyclic aromatic hydrocarbons from contaminated soils by the empowered surfactant properties of de novo O-alkylated humic matter
Get PDFAqueous solutions of humic acid (HA) derivatized by a catalyzed O-alkylation reaction with methyl, pentyl, and benzyl groups at 40, 60, and 80% of total HA acidity were used to wash off polycyclic aromatic hydrocarbons (PAHs) from two contaminated soils. The enhanced surfactant properties enabled the alkylated HA to remove phenanthrene, anthracene, fluoranthene, and pyrene from both soils more extensively than the original unmodified HA, the 60% benzylation generally showing the greatest soil washing efficiency. For both soils, all alkylated HA revealed greater PAH removals than Triton X-100 nonionic surfactant, while the benzylated and methylated HA nearly and fully matched pollutants release by the anionic SDS in the coarse- and fine-textured soils, respectively. A consecutive second washing with 60% benzylated HA removed additional PAHs, in respect to the first washing, from the coarser-textured soil, except for fluoranthene, while removal from the finer-textured soil incremented even more for all PAHs. These findings indicate that the enhanced hydrophobicity obtained by a simple and unexpensive chemical derivatization of a natural humic surfactant can be usefully exploited in the washing of polluted soils, without being toxic to the soil biota and by potentially promoting the subsequent bio-attenuation of organic pollutants
Effective degradation of organic pollutants in aqueous media by microbial strains isolated from soil of a contaminated industrial site
Get PDFBackground: Bioremediation is a low-cost technology, whose efficacy is often enhanced with preliminary mild physical–chemical remediation methods. A further advantage of bioremediation resides in its eco-compatibility and, thus, sustainability. Two autochthonous microbial strains, Methylobacterium populi VP2 and Aspergillus sydowii VP4, were isolated from a soil of a highly contaminated industrial site and used to degrade the aqueous extract of contaminants (AEC) obtained from the same polluted soil. Results: The AEC incubation with both strains produced a significant removal of most organic pollutants, although the degradation capacity decreased with increasing AEC concentration in the minimal selective liquid medium (MSML) of the experiments. At 30 % of AEC, M. populi VP2 determined the removal of most pollutants and the appearance of new products due to oxidation and enzymatic degradation. Incubation of A. sydowii VP4 at the same AEC concentration in MSML removed the same pollutants but also the derived degradation products. Our results showed that the strains isolated from a highly contaminated soil maintained the capacity to use organic contaminants as metabolic carbon in aqueous extracts from the same soil. The greater biodegradation efficiency of the fungal strain in comparison to M. populi VP2 may be caused by a modification of the A. sydowii VP4 cell surface that increases cell permeability to hydrophobic compounds and thus enhances the extent of pollutants degradation. Conclusions: This work indicates that two specific strains, M. populi VP2 and A. sydowii VP4, isolated from the soil of a highly contaminated site are not only useful in the treatment of leaching polluted waters but may also be used in bioaugmentation practices during remediation of contaminated soils
Structural recognition of lignin isolated from bioenergy crops by subcritical water: Ethanol extraction
No full textLignin was isolated with subcritical water:ethanol:CO2 (Sub-CW) from biorefinery biomasses, such as giant reed (AD) and miscanthus (MG), with recovery yields about 30% on Klason lignin. Their structural composition assessed by IR and NMR techniques, as well as Derivatization Followed by Reductive Cleavage (DFRC/GC-MS). The 2D HSQC-NMR spectra elucidated that the Sub-CW extracts contained different lignin dimers and co-extracted carbohydrates. The DFRC/GC-MS revealed that syringyl molecules were more abundant in AD, while guaiacyl monomers were predominant in MG. Lignin residues were derivatized with phospholane to quantitatively estimate the amount of OH groups by 31P NMR, showing a marked predominance of aliphatic units for both lignins, due to the presence of either hydroxyls in lignin side-chain or residual carbohydrates. Lignin residues derivatized with phospholane allowed to record 31P-DOSY NMR spectra. AD-lignin showed a smaller diffusivity constant than for MG-substrate, possibly because of the larger content of disaccharides in MG lignin. We showed that the molecular composition of lignin isolated by the Sub-CW technique may differ depending on the type of biomass used for the extraction, suggesting a different industrial application of lignin from various biomass
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