[Show abstract][Hide abstract] ABSTRACT: A dihydroxybenzenes(DHB)-driven Fenton reaction was found to be more efficient than a simple Fenton reaction based on OH radical and activated species production. The reason for this enhanced reactivity by [Fe DHB] complexes is not well understood, but results suggest that it may be explained by the formation of oxidation species different from those formed during the classic Fenton reactions. In previous work, greater concentrations, and more sustained production of OH over time were observed in DHB driven Fenton reactions versus neat Fenton and Fenton-like reactions. In this work, chemiluminescence (CL) was monitored, and compared to OH production kinetics. The CL of the DHB-driven Fenton reaction was shorter than that for sustained production of OH. CL appears to have been caused by excited Fe(IV) species stabilized by the DHB ligands initially formed in the reaction. Formation of this species would have to have occurred by the reaction between OH and Fe(III) in a DHB complex.
[Show abstract][Hide abstract] ABSTRACT: In this paper, formation of unique carbon nanostructures via carbonization of wood in a step-wise process is reviewed. The mechanism described for the production of carbon nanotubes improves our understanding of a historic mystery related to the production of Damascus steel.
[Show abstract][Hide abstract] ABSTRACT: In this work, pyrolysis-molecular beam mass spectrometry analysis coupled with principal components analysis and (13)C-labeled tetramethylammonium hydroxide thermochemolysis were used to study lignin oxidation, depolymerization, and demethylation of spruce wood treated by biomimetic oxidative systems. Neat Fenton and chelator-mediated Fenton reaction (CMFR) systems as well as cellulosic enzyme treatments were used to mimic the nonenzymatic process involved in wood brown-rot biodegradation. The results suggest that compared with enzymatic processes, Fenton-based treatment more readily opens the structure of the lignocellulosic matrix, freeing cellulose fibrils from the matrix. The results demonstrate that, under the current treatment conditions, Fenton and CMFR treatment cause limited demethoxylation of lignin in the insoluble wood residue. However, analysis of a water-extractable fraction revealed considerable soluble lignin residue structures that had undergone side chain oxidation as well as demethoxylation upon CMFR treatment. This research has implications for our understanding of nonenzymatic degradation of wood and the diffusion of CMFR agents in the wood cell wall during fungal degradation processes.
European Journal of Biochemistry 08/2009; 14(8):1253-63. DOI:10.1007/s00775-009-0569-6 · 3.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study the oxidative behavior of carbons derived from cellulose and lignin were compared using thermogravimetric analysis (TGA). Specific surface area and chemical composition of the two types of carbon were analyzed using nitrogen adsorption at 77K and infrared spectroscopy respectively. The results demonstrate that cellulose carbon has a higher reaction order and lower activation energy than lignin carbon under identical experimental conditions when they were prepared at temperatures lower than 500 degrees C. However, such differences were considerably reduced for the carbon samples prepared at temperatures greater than 700 degrees C. It was verified that lignin carbon is more stable than cellulose carbon due to its higher content of aromatic structures when they are prepared at lower temperature. The specific surface area and porosity have a more limited contribution to the differential oxidative behaviors of the two types of carbon. This research has significance related to the formation of carbon nanotubes from plant materials during low temperature carbonization.
[Show abstract][Hide abstract] ABSTRACT: Carbon nanotubes (CNTs) were produced from wood fiber using a low temperature process, which included continuous oxidization at 240 degrees C and cyclic oxidation at 400 degrees C. The inside diameter of the CNTs was approximately 4-5 nm and the outside diameter ranged from 10 nm to 20 nm. No CNTs were produced when pure lignin and cellulose were tested indicating that the molecular and spatial arrangement of cell wall plays an important role in CNT formation. The research suggests that the chemical components in the secondary plant cell wall and their differential ablation properties are critical for the formation of CNTs at these comparatively low temperatures.
Journal of Nanoscience and Nanotechnology 06/2008; 8(5):2472-4. DOI:10.1166/jnn.2008.235 · 1.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This work investigated the effect of a chelator-mediated bio-mimetic free radical treatment on repulping and flotation operations during the deinking of laser printed copy paper. A chelator-mediated free radical treatment was carried out at two different chemical levels and a two-step repulping method, which combined conventional alkaline repulping as well as free radical treatment, was also developed. Flotation trials were performed on each of these treated samples to separate ink particles. Results from image analysis and paper physical properties testing are presented, and the deinking efficiency for these different treatments is also compared. Results indicate that under properly controlled conditions, free radical treatment can perform better than conventional chemical deinking methods.
[Show abstract][Hide abstract] ABSTRACT: A mediated Fenton system has been evaluated for decolorization of several types of dyes. The result shows that the Fenton system with a dihydroxybenzoic acid (DHBA) chelator-mediator effectively reduced the color of a diluted solution of Carta Yellow RW liquid, Carta Yellow G liquid, and Cartasol Red 2GF liquid dye to a colorless level after 90 minutes of treatment with 100 microM iron II (Fe[II]), 100 microM DHBA, and 10 mM hydrogen peroxide (H2O2) at room temperature. Our results show that compared to a neat Fenton process, the mediated Fenton decolorization process increased the production, and therefore the effective longevity, of hydroxyl radical (OH) species to increase the decolorization efficiency. Our results suggest that application of this system would also result in an increase in dissolved oxygen (DO) in solution, which in turn would result in reduction of chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total organic carbon (TOC).
Water Environment Research 11/2004; 76(7):2703-7. · 1.00 Impact Factor