title: Oxidative and photoxidative polymerization of humic suprastructures by heterogeneous biomimetic catalysis.
abstract: The 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.
authors.affiliation: Centro Interdipartimentale di Ricerca sulla Risonanza Magnetica Nucleare per l'Ambiente, l'Agroalimentare ed i Nuovi Materiali (CERMANU), Università di Napoli Federico II, Via Università, 100, 80055 Portici (NA), Italy.
authors.forename: Assunta
authors.initials: A
authors.lastname: Nuzzo
authors.forename: Alessandro
authors.initials: A
authors.lastname: Piccolo
mesh_terms: D000538:Aluminum Silicates; D040761:Biomimetic Materials / Q000737:chemistry*; D002384:Catalysis; D002850:Chromatography, Gel; D000077215:Clay; D006812:Humic Substances; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D058105:Polymerization; D011166:Porphyrins / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D013818:Thermogravimetry
chemical_list: D000538:Aluminum Silicates; D006812:Humic Substances; D011166:Porphyrins; D012987:Soil; D006861:Hydrogen Peroxide; D000077215:Clay