In situ generation of hydrogen peroxide and its use for enzymatic degradation of 2,4,6‐trinitrotoluene

A novel electroenzymatic method hybridizing both electrochemical and enzymatic reactions and using lignin peroxidase (Lip) for treatment of TNT (2,4,6‐trinitrotoluene) waste was studied. In the presence of Phanerochaete chrysosporium lignin peroxidase, TNT was degraded in an electrochemical reactor using hydrogen peroxide, produced by an electrode reaction. The effectiveness of the electroenzymatic method was examined in this study. The efficiency of removal of TNT was greater than that of biochemical methods under optimal conditions. The effects of reaction conditions on TNT degradation and denitrification, TOC removal efficiency, and power consumption were also investigated. A potential (vs Ag/AgCl) of +0.1 V was selected as being optimal for the electroenzymatic reaction. TNT degradation was significantly improved in the combined veratryl alcohol–lignin peroxidase oxidation procedure, showing complementary effects of veratryl alcohol (VA) in the TNT degradation reaction. Denitrification was found to be proportional to the amount of TNT degraded. One intermediate, 2,4‐diamino‐6‐nitrotoluene, derived from the oxidative degradation of TNT, was eluted on an HPLC chromatogram and was detected using mass spectrometry. The electroenzymatic method had a lower power requirement than electrochemical oxidation at ?0.2 and ?0.4 V. The electroenzymatic method may be easily applied to biodegradation systems and provide added benefit for highly recalcitrant chemicals since the system would not be susceptible to the toxicity of the chemical. Also H₂O₂ instability and decomposition in the samples after preparation would not be of concern. © 2001 Society of Chemical Industry     

Toxicity of soluble products from the peroxidase‐catalysed polymerization of substituted phenolic compounds

The residual toxicities of aqueous solutions of phenol and substituted phenols were investigated following polymerization under the catalytic action of soybean peroxidase (SBP) and horseradish peroxidase (HRP) enzymes. The treated mixtures obtained from the enzymatic polymerization of these phenols were usually significantly more toxic than expected, and in several cases, the residual toxicity exceeded the initial toxicity of the solution of untreated parent compound. However, this residual toxicity tended to be lower when combinations of these phenols were co‐polymerized. The decrease in toxicity was attributed to the different polymeric products which form as a result of a cross‐coupling between products of the enzyme‐catalysed oxidation of parent phenols. The residual toxicities obtained using either SBP or HRP were not significantly different in most cases. © 2000 Society of Chemical Industry     

Acrylonitrile monomer grafting on gray cotton to impart high water absorbency

Acrylonitrile (AN) monomer was directly grafted onto gray cotton yarn using a KMnO₄—HNO₃ redox system by a chemical initiation technique. The major factors affecting polymerization of AN, such as KMnO₄, nitric acid, and AN concentration as well as the reaction time and temperature of the polymerization, were studied. The water absorbency of grafted fibers depends strongly on their posttreatment. Saponification of AN‐g‐cotton with a hot sodium hydroxide solution developed superabsorbency. Absorbency with distilled water and a saline solution (0.9% NaCl) was studied. Grafting cellulose with AN using a KMnO₄/nitric acid redox system proceeds by a free‐radical mechanism. Use of cotton in the gray form as a starting material rather than a bleached one helps in the better deposition of MnO₂ with subsequent acceleration of the grafting reaction, resulting in better whiteness of the grafted products. The enhancement in the whiteness index could be interpreted in terms of the oxidation of natural coloring matter, which happens to be the objective of the bleaching process. Grafting of AN onto gray cotton results in the elimination of several preparatory treatments including the conventional bleaching operation, ultimately reducing the water consumption as well as minimizing the unwanted effluent generation. The work has the potential of promoting cost‐effective and environmental friendly technologies and techniques. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 887–894, 1999     

Oxidation,Redox Disproportionation and Chain Termination Reactions Catalysed by the Pd‐561 Giant Cluster

Redox disproportionation of benzyl alcohol to benzaldehyde and toluene catalysed by the Pd₅₆₁phen₆₀(OAc)₁₈₀ (phen=1,10‐phenanthroline) giant cluster 1 under anaerobic conditions was found, whereas in an O₂ atmosphere cluster 1 catalyses the oxidation of benzyl alcohol to benzaldehyde and inhibits further oxidation of the latter. A study of the AIBN‐initiated and non‐initiated oxidation of benzyl alcohol, sec‐butyl alcohol and styrene in the presence of cluster 1 revealed that cluster 1 performs three functions in the oxidation reactions: 1) catalysis of polar oxidation of the substrates with O₂, 2) termination of the chains of radical oxidation, and 3) catalysis of redox disproportionation.     

Comparative Studies of Chlorine Dioxide Reactions with Muconic Acid Derivatives and Lignin Model Compounds

Abstract

The reaction of chlorine dioxide with different types of lignin model compounds was investigated in order to compare the kinetics and to evaluate the amount of oxidant consumed by the different substrates. Complete reaction of lignin model compounds was observed at ClO₂‐to‐substrate molar ratios of 0.9–1.2, which corresponds to an electron transfer varying between 5–6 equivalents per mole of substrate. Muconic acid derivatives also fully reacted, at a ClO₂‐to‐substrate molar ratio of 1.2, with the oxidant consumption being about 4 equivalents per mole of substrate. The reaction of mixtures of phenolic, non‐phenolic, and muconic acid type substrates showed that the reaction rates of non‐phenolic and muconic acid type substrates were rather similar. This study suggests that further reaction between ClO₂ and the primary lignin oxidation products, such as muconic acid type structures could be the cause of overconsumption of oxidant in a D stage.     

Hydrotreating and hydrothermal treatment of alkaline lignin as technological valorization options for future biorefinery concepts: a review

Lignin has the potential to be a sustainable resource for producing biobased chemicals (e.g. phenols, aromatic hydrocarbons, vanillin) for multiple applications. However, given its heterogeneous and rigid structure, its efficient conversion to value‐added products remains one of the most important limiting factors for the successful viability of the biobased economy. Hydrotreating and hydrothermal treatment (including liquefaction, gasification and wet oxidation) are promising technologies that can convert lignin into biobased products. This review article provides a literature overview of how key process parameters of hydrotreating and hydrothermal treatment (operating conditions, catalysts, solvents, type of starting lignin) may influence the conversion of alkaline lignin into valuable chemical products. It was observed that low selectivity to products (and subsequent required separation and purification) and char formation are the main hurdles for effective conversion of alkaline lignin. However, experimental work in alternative catalytic systems, solvents and hydrogen sources has shown that promising opportunities exist to overcome these drawbacks. Certain catalysts (e.g. Ru/Al₂O₃) have been found to improve selectivity and the use of alcohol solvents (especially methanol or ethanol) as a hydrogen source has been found to improve product yields and reduce char formation at lower working temperatures and pressures. © 2016 Society of Chemical Industry     

The electrocatalytic oxidative polymerization of o-phenylenediamine by reduced graphene oxide and properties of poly(o-phenylenediamine)

The electrocatalytic oxidative polymerization of o-phenylenediamine (o-PD) was performed on a reduced graphene oxide (RGO)/glassy carbon (GC) electrode. The electrolysis of o-PD was carried out using cyclic voltammetry and potentiostatic and galvanostatic methods. The experimental results demonstrated that the reduced graphene oxide (RGO) has a pronounced catalytic ability for the electrochemical oxidative polymerization of o-PD in a 0.60 M H₂SO₄ solution compared to the bare GC electrode; however, graphene oxide has only a slight catalytic ability for the electrochemical oxidative polymerization of o-PD. The above three electrochemical techniques confirmed that there is a considerable discrepancy between the characteristics of the electrocatalytic oxidation of a species and the characteristics of the electrocatalytic oxidative polymerization of o-PD. This effect occurs because the charges passed during the electrolysis of o-PD on the bare GC electrode were mainly consumed for the formation of the soluble oligomer; however, RGO plays an important role in suppressing the formation of the soluble oligomer. An unexpected result was obtained: two or three pairs of the redox peaks of poly(o-phenylenediamine) (PoPD), synthesized using RGO as a catalyst, occur on the cyclic voltammogram in a wider potential range, depending on the polymerization conditions; however, only one pair of redox peaks occurs on the cyclic voltammogram of the conventional PoPD in a narrow potential range under exactly the same experimental conditions. The NMR and ESR spectra of the PoPD polymerized on the RGO/GC electrode are presented in this paper.     

The Cation Radical Chain Cycloaddition Polymerization of N,3‐Bis(trans‐1‐2)carbazole: The Critical Importance of Intramolecular Hole Transfer in Cation Radical Cycloaddition Polymerization

The synthesis and polymerization of N,3‐[bis(trans‐1‐2)]carbazole ( 1 ) is reported. Using either the stable cation radical salt tris(4‐2)aminium hexachloroantimonate ( 2 ^+. ) or anodic oxidation to initiate the reaction, novel cycloaddition polymers are obtained in which the intermonomer linkages are of the cyclobutane, and to some extent of the Diels−Alder, type. A novel cation radical chain mechanism is proposed for the reaction, and extensive support for this mechanism is presented. The greatly enhanced reactivity of difunctional, as opposed to monofunctional, substrates in cation radical cycloadditions is dramatically highlighted by a comparison of the cycloaddition reactivity (rapid polymerization) of 1 versus N‐propenylcarbazole (inefficient cyclodimerization) under electrochemical oxidation conditions. The sharply enhanced reactivity of 1 is attributed to the availability of intramolecular hole transfer in the bifunctional but not the monofunctional case.     

Oxidative detoxification of aqueous bark extracts. Part II: Alternative methods

The most important problem associated with the high-pH autoxidative detoxification of methanogenic toxins in debarking wastewater was its limited application to the aqueous extractives of bark from specific species. The autoxidative polymerization of coniferous bark extracts exhausted prior to complete removal of the toxic oligomeric tannins. As a result, highly toxic spruce bark extracts were only partly detoxified. Birch bark extracts were not detoxified, even though effective polymerization of the oligomeric tannins occurred. The non-tannin toxins in birch bark extracts and toxic intermediates produced by high-pH autoxidation of these extracts were responsible for the poor detoxification results. These problems can potentially be resolved by applying alternative oxidation methods. In this study a high level of detoxification was obtained for all bark species tested by short-term destructive oxidations with H₂O₂, or by long-term aerobic biological treatments which caused high levels of polymerization. The applicability of high-pH autoxidation was also made feasible for all species of bark by applying a granular active carbon treatment after the autoxidation. The active carbon was able to adsorb the residual toxic oligomeric tannins of autoxidized spruce bark extracts and the non-tannin toxins in autoxidized birch bark extracts. Additionally, a potential disadvantage of the autoxidative detoxification method is the formation of colored end products. Although these compounds are non-toxic and are non-biodegradable, their elimination from the wastewater would be necessary if discharge norms concerning color and non-biodegradable COD must be fulfilled. The destructive oxidation with H₂ O₂ produced non-toxic low-molecular-weight compounds which did not have much color. The autoxidation and long-term aerobic biological treatments produced highly colored humic end products which could be eliminated by calcium precipitation.     

Affinity‐tuned peroxidase‐like activity of hydrogel‐supported Fe3O4 nanozyme through alteration of crosslinking concentration

In this work, we evaluated the effect of crosslinking concentration on the affinity of poly (2‐acrylamido‐2‐methyl‐1‐propansulfonic acid) (PAMPS) hydrogel‐supported Fe₃O₄ nanozyme towards substrates (tetramethylbenzidine (TMB) and H₂O₂). The peroxidase‐like catalytic activity of PAMPS/Fe₃O₄ nanozyme was discussed with respect to crosslinking concentration of PAMPS hydrogel for the oxidation of TMB in the presence of H₂O₂ at room temperature. High catalytic activity was achieved due to good dispersion of Fe₃O₄ nanozyme in the hydrogel network and strong affinity of PAMPS hydrogel‐supported Fe₃O₄ nanozyme towards substrates. The affinity between the hydrogel‐supported Fe₃O₄ nanozyme and substrates can be improved by regulating the crosslinking concentration of PAMPS hydrogel without other trenchant experimental conditions. In addition, the result indicated that H₂O₂ can be detected even at a concentration as low as 1.5 × 10^?6 mol L^?1 with a linear detection range of 1.5–9.8 × 10^?6 mol L^?1. Such investigations not only showed a new approach to improve the affinity and peroxidase‐like activity of Fe₃O₄ nanozyme, but also verified its potential application in bio‐detection and environmental chemistry. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43065.     

Biophysical Features of Bacillithiol,the Glutathione Surrogate of Bacillus subtilis and other Firmicutes

Bacillithiol (BSH) is the major low‐molecular‐weight (LMW) thiol in many low‐G+C Gram‐positive bacteria (Firmicutes). Evidence now emerging suggests that BSH functions as an important LMW thiol in redox regulation and xenobiotic detoxification, analogous to what is already known for glutathione and mycothiol in other microorganisms. The biophysical properties and cellular concentrations of such LMW thiols are important determinants of their biochemical efficiency both as biochemical nucleophiles and as redox buffers. Here, BSH has been characterised and compared with other LMW thiols in terms of its thiol pK_a, redox potential and thiol–disulfide exchange reactivity. Both the thiol pK_a and the standard thiol redox potential of BSH are shown to be significantly lower than those of glutathione whereas the reactivities of the two compounds in thiol–disulfide reactions are comparable. The cellular concentration of BSH in Bacillus subtilis varied over different growth phases and reached up to 5 mM , which is significantly greater than previously observed from single measurements taken during mid‐exponential growth. These results demonstrate that the biophysical characteristics of BSH are distinctively different from those of GSH and that its cellular concentrations can reach levels much higher than previously reported.     

Black liquor detoxification by laccase of Trametes versicolor pellets

Black liquors from a soda pulping mill were treated with the white‐rot fungus Trametes versicolor to detoxify and reduce colour, aromatic compounds and chemical oxygen demand (COD). The fungus was used in the form of pellets in aerated reactors (fluidized, stirred and air‐pulsed reactors). Reductions in colour and aromatic compounds of 70–80% and in COD of 60% were achieved. During the different experiments, laccase activity was detected but neither lignin peroxidase (LiP) nor manganese peroxidase activities were detected, although T versicolor is able to produce these enzymes. Experiments also showed a LiP activity inhibitory effect produced by lignin. From the results obtained, it can be concluded that there is a relationship between laccase production and toxicity reduction. This correlation responds to the equation Laccase production = 1.57 LN (toxicity reduction) ?16.40. Copyright © 2003 Society of Chemical Industry     

Characteristics of Dioxane Lignins Isolated at Different Ages of Nalita Wood (Trema orientalis)

Abstract

Nalita (Trema orientalis) is one of the fastest growing trees in the tropical countries. The structural characteristics of lignin isolated at different ages of Nalita wood (Trema orientalis) by acidolytic dioxane method were examined by UV, FTIR, ¹H‐NMR and ¹³C‐NMR spectroscopy, alkaline nitrobenzene oxidation, molecular weight determination, elemental and methoxyl analysis. The data were compared with aspen lignin. The structural analysis revealed that Nalita wood lignin is syringyl‐guaiacyl type. The methoxyl content in Nalita wood lignin was lower than aspen lignin. The C₉ formulas for 30‐months‐old Nalita was C₉H_9.31O_3.13(OCH₃)_1.27, whereas that of aspen was C₉H_8.94O_3.15(OCH₃)_1.47. The weight average molecular weight of Nalita wood lignin was decreased from 36,500 to 25,500 with increasing tree age from 12 to 30 months, whereas weight average molecular weight of aspen was 20,000. Both alcoholic and phenolic hydroxyl group in Nalita wood lignin is lower than aspen lignin.     

Direct grafting poly(methyl methacrylate) from TiO2 nanoparticles via Cu2+‐amine redox‐initiated radical polymerization: An advantage of monocenter initiation

Cu²⁺ can oxidize amines to generate radicals to initiate radical polymerization of electron‐deficient monomers under mild conditions. Here, CuSO₄‐catalyzed redox‐initiated radical polymerizations of methyl methacrylate from amino‐functionalized TiO₂ nanoparticles (TiO₂‐NH₂ nanoparticles) was performed to prepare TiO₂ nanoparticles grafted with poly(methyl methacrylate) (TiO₂‐g‐PMMA hybrid nanoparticles) in dimethylsulfoxide or N,N‐dimethylformamide at 90°C. Infrared spectroscopy, thermogravimetric analysis, and X‐ray photoelectron spectroscopy confirmed the presence of the grafted PMMA and the grafting yield was about 50 wt%. Microscopy and particle‐size analysis indicated that TiO₂‐g‐PMMA nanoparticles had a good affinity to organic media. Because only aminyl radical (? NH?) on TiO₂ nanoparticles formed in Cu²⁺‐amine redox‐initiation step, there was no free PMMA chains formed during polymerization. Thus, our protocol provides a facile strategy to prepare inorganic/organic hybrid nanoparticles via one‐pot Cu²⁺‐amine redox‐initiated free radical polymerization. POLYM. ENG. SCI., 55:735–744, 2015. © 2014 Society of Plastics Engineers     

Converting Alkali Lignin to Biofuels over NiO/HZSM‐5 Catalysts Using a Two‐Stage Reactor

A series of NiO/HZSM‐5 catalysts were used to convert alkali lignin to hydrocarbon biofuels in a two‐stage catalytic pyrolysis system. The results indicated that all NiO/HZSM‐5 catalysts reduced the content of undesirable phenols, furans, and alcohols of the biofuel compared to non‐catalytic treatment. The NiO/HZSM‐5 catalyst with the lowest amount of NiO generated the highest biofuel yield in all catalytic treatments, and it also produced biofuel with the highest content of hydrocarbons. The emission of carbon oxides (CO and CO₂) increased in the treatments with higher‐NiO loading HZSM‐5 due to the redox reaction between NiO and the oxygenated compounds in the bio‐oil. Ni₂SiO₄ was generated in the used NiO/HZSM‐5 catalysts during the high‐temperature pyrolysis process.     

Electrosyntheses and characterization of poly(5‐bromoindole) in boron trifluoride diethyl etherate

Poly(5‐bromoindole) (PBrI) films were synthesized electrochemically by direct oxidation of 5‐bromoindole in pure boron trifluoride diethyl etherate. The oxidation potential of 5‐bromoindole in this medium was measured to be only 0.97 V vs. saturated calomel electrode, which was lower than that determined in acetonitrile + 0.1 mol L^?1 Bu₄NBF₄ (1.08 V). PBrI films obtained from this medium showed good electrochemical behavior and good thermal stability. Structural studies showed that the polymerization of 5‐bromoindole ring occurred at 2,3 position. As‐formed PBrI films were thoroughly soluble in strong polar solvent dimethylsulfoxide and partly soluble in tetrahydrofuran. Fluorescent spectral studies indicated that PBrI was a good blue‐light emitter. The excitation and emission spectra of PBrI showed a significant shift to longer wavelength compared with that of the monomer, consistent with the greater extent of electron delocalization. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 539–547, 2006     

pKa-Values of Guaiacyl and Syringyl Phenols Related to Lignin

Abstract

The literature relating to the pK_a -values of guaiacyl- and syringyl-derived phenols has been thoroughly surveyed and summarized. In addition, the pK_a -values of a number of guaiacyl, syringyl and other phenols related to lignin have been determined using a spectrophotometric method combined with multivariate evaluation. Differences and similarities between the acidities of a number of substances are extensively discussed. The pK_a -value strongly affects the delignification during pulping, bleaching and leaching of lignin during pulp washing.     

Real‐time monitoring by proton relaxometry of radical polymerization reactions of acrylamide in aqueous solution

The potential of time‐domain nuclear magnetic resonance (TD‐NMR) for the real‐time monitoring of solution radical polymerizations is demonstrated. A model system composed of a redox‐pair initiator system, acrylamide as monomer and water as solvent was investigated. A second‐generation continuous wave free precession technique was employed to measure the longitudinal relaxation time constant (T₁) of the samples throughout the polymerization reactions. This parameter was shown to be sensitive to the reactant feed free‐radical enhancement of the water molecule relaxation time, making it a good probe to monitor monomer conversion in real time in an automated, non‐destructive fashion. It was found that the T₁ value was better than the transverse relaxation time constant (T₂) for describing the evolution of the polymerization reactions, due to its greater sensitivity to paramagnetic effects. The TD‐NMR signal variation observed was linked to the formation, propagation and termination steps of the radical polymerization kinetics scheme. These first results may contribute to the application of real‐time monitoring of radical polymerization reactions employing low‐cost and robust TD‐NMR spectrometers. © 2018 Society of Chemical Industry     

Nanocomposite of polyaniline and a layered niobate acid host: Synthesis,electrochemical studies,and photocatalytic properties

The synthesis of polyaniline (PANI) with H₄Nb₆O₁₇ (HNbO) to form PANI/HNbO lamellar nanocomposite by in situ polymerization using aniline (ANI) intercalation compound ANI/HNbO as the intermediate has been investigated. The properties of the samples were characterized by means of XRD, SEM, TEM, FT‐IR, UV–vis spectroscopy, and TG‐DTA. The in situ polymerization of ANI packed in a regular orientation in a mono‐ and bilayers (i.e., pseudo‐bilayers) structure within the HNbO interlayers led to PANI/HNbO nanocomposite powder using (NH₄)₂S₂O₈ as the catalyst with PANI monolayer packing orientation within the HNbO interlayers. PANI/HNbO nanocomposite showed improved thermal stability compared with original PANI by TG analysis. The PANI/HNbO nanocomposite was studied by cyclic voltammetry (CV), which indicated the good redox activity and electrochemical‐cycling stability in acidic solution. The interaction between PANI and nanosheets greatly affected the electrochemical behavior of PANI/HNbO nanocomposite. Two couples of redox peaks corresponded to two oxidation process of PANI in acid conditions. The PANI/HNbO nanocomposite exhibited much higher photocatalytic activities for the degradation of methylene blue (MB) in aqueous solution under visible light irradiation than HNbO itself. POLYM. COMPOS., 34:834–841, 2013. © 2013 Society of Plastics Engineers     

Synthesis and characterization of polybutadiene with monotitanocene/methylaluminoxane catalyst

Butadiene was polymerized using a monotitanocene complex of η⁵‐pentamethylcyclopentadienyltribenzyloxy titanium [Cp*Ti(OBz)₃] in the presence of four types of modified methylaluminoxanes (mMAO), which contained different amounts of residual trimethylaluminum (TMA). The titanium oxidation states in Cp*Ti(OBz)₃/mMAO and Cp*Ti(OBz)₃/mMAO/triisobutylaluminum (TIBA) catalytic systems were determined by redox titration method. The effects of various oxidation states of titanium active species on butadiene polymerization were investigated. It was found that Ti(III) active species is more effective for preparing polybutadiene with high molecular weight. The addition of TIBA to the Cp*Ti(OBz)₃/mMAO system could reduce a greater number of Ti(IV) complexes to Ti(III) species and lead to significant increases of polymerization activity and molecular weight of polymer, whereas the polybutadiene microstructure was only slightly changed. On the basis of microstructure and property characterization by FTIR, ¹³C‐NMR, DSC, and WAXD, all resultant polymers were proved to be amorphous polybutadiene with mixed 1,2; cis‐1,4; and trans‐1,4 structures. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2494–2500, 2004