H2O2 Decomposition Rate Research Articles

Consequences of Confinement for Alkene Epoxidation with Hydrogen Peroxide on Highly Dispersed Group 4 and 5 Metal Oxide Catalysts

Ti, Nb, and Ta atoms substituted into the framework of zeolite *BEA (M-BEA) or grafted onto mesoporous silica (M-SiO2) irreversibly activate hydrogen peroxide (H2O2) to form pools of metal-hydroperoxide (M-OOH) and peroxide (M-(η2-O2)) species for alkene epoxidation. The product distributions from reactions with Z-stilbene, in combination with time-resolved UV–vis spectra of the reaction between H2O2-activated materials and cyclohexene, show that M-OOH surface intermediates epoxidize alkenes on Ti-based catalysts, while M-(η2-O2) moieties epoxidize substrates on the Nb- and Ta-containing materials. Kinetic measurements of styrene (C8H8) epoxidation reveal that these materials first adsorb and then irreversibly activate H2O2 to form pools of interconverting M-OOH and M-(η2-O2) intermediates, which then react with styrene or H2O2 to form either styrene oxide or H2O2 decomposition products, respectively. Activation enthalpies (ΔH⧧) for C8H8 epoxidation and H2O2 decomposition decrease linearly with increasing heats of adsorption for pyridine or deuterated acetonitrile coordinated to Lewis acid sites, which suggests that materials with greater electron affinities (i.e., stronger Lewis acids) are more active for C8H8 epoxidation. Values of ΔH⧧ for C8H8 epoxidation and H2O2 decomposition also decrease linearly with the ligand-to-metal charge-transfer (LMCT) band energies for the reactive intermediates, which is a more relevant measure of the requirements for the active sites in these catalytic cycles. Epoxidation rates depend more strongly on the LMCT band energy than H2O2 decomposition rates, which shows that more electrophilic M-OOH and M-(η2-O2) species (i.e., those formed at stronger Lewis acid sites) give both greater rates and greater selectivities for epoxidations. Thermochemical analysis of ΔH⧧ for C8H8 epoxidation and adsorption enthalpies for C8H8 within the pores of *BEA and SiO2 reveal that the 0.7 nm pores within M-BEA preferentially stabilize transition states for C8H8 epoxidation with respect to the 5.4 nm pores of M-SiO2, while H2O2 decomposition is unaffected by the differences between these pore diameters due to the small Stokes diameter of H2O2. Thus, the differences in reactivity and selectivity between M-BEA and M-SiO2 materials is solely attributed to confinement of the transition state and not differences in the identity of the reactive intermediates, mechanism for alkene epoxidation, or intrinsic activation barriers. Consequently, the rates and selectivities for alkene epoxidation reflect at least two orthogonal catalyst design criteria—the electronegativities of the transition metal atoms that determine the electronic structure of the active complex and the mean diameters of the surrounding pores that can selectively stabilize transition states for specific reaction pathways.

Degradation of organic compounds during the corrosion of ZVI by hydrogen peroxide at neutral pH: Kinetics, mechanisms and effect of corrosion promoting and inhibiting ions

The corrosion of zero valent iron (ZVI) by hydrogen peroxide (H2O2) generates hydroxyl (⋅OH) and other radical oxygen species (ROS) that degrade organic materials. To better understand the factors that govern the ROS formation during the H2O2-induced corrosion, we investigated the degradation of an organic probe compound (acesulfame (ACE)) in slurries of ZVI powder in unbuffered laboratory water at pH 6.5 ± 0.5. Chloride ions accelerated the corrosion of ZVI by H2O2 and the formation ROS and, therefore, the degradation of organic materials. Conversely, slowing corrosion by phosphate buffer inhibited ROS formation and the degradation of organic compounds. The rate of H2O2 decomposition was correlated with the liberation of Fe2+(aq) and the ACE degradation rate. The kinetics of H2O2 decomposition was pseudo-first-order and zero-order at low (<0.04 mM/mg) and high [H2O2]/[ZVI] initial ratios, respectively, and was consistent with Langmuir kinetics. The H2O2 decomposition rate was proportional to the ZVI reactive surface area (SA) and nearly independent of the extent of ZVI oxidation, the presence of a Fe2+(aq) chelating agent, and ⋅OH quenchers (methanol and tert-butanol). Kinetic data suggest a mechanism involving rapid cathodic reduction of H2O2 at the metallic ZVI surface which causes the liberation of Fe2+(aq) that generate ⋅OH via the homogeneous Fenton reaction. The stoichiometric efficiency (SE) of organics degradation ranged from 0.0008% to 0.014% and increased with decreasing H2O2 decomposition rate.

Bleaching of cotton fabric with tetraacetylhydrazine as bleach activator for H2O2

Tetraacetylhydrazine (TH) as bleach activator for H2O2 cotton bleaching was synthesized and characterized by 1H NMR, 13C NMR and MS spectra. TH has better solubility than that of TAED. The CIE whiteness index (WI), H2O2 decomposition rate and bursting strength were employed to investigate the performance of H2O2/TH bleaching system. By addition of TH, WI and H2O2 decomposition rate increased significantly at 70 °C. Bleaching temperature, NaHCO3 concentration and bleaching time were also discussed in detail and the loss of bursting strength is not clear. By using benzenepentacarboxylic acid (BA) as a fluorescent probe for hydroxyl radical detection, the bleaching process of H2O2/TH system was investigated. Acetylhydrazine and diacetylhydrazine were also utilized to further confirm the process. In addition, bimolecular decomposition was investigated by using 9,10-dimethylanthracene (DMA) as fluorescent probe of 1O2. Based on these experimental results, the bleaching mechanism of H2O2/TH system was proposed.

New Signal Probe Integrated with ABEI as ECL Luminophore and Ag Nanoparticles Decorated CoS Nanoflowers as Bis-Co-Reaction Accelerator to Develop a Ultrasensitive cTnT Immunosensor

In this work, Ag nanoparticles (Ag NPs) decorated CoS nanoflowers (CoS NFs) were firstly used as bis-coreaction accelerator for signal amplification to establish an highly sensitive electrochemiluminescence (ECL) immunosensor for cardiac troponin T (cTnT) detection. Due to the synergistic catalysis between CoS NFs and Ag NPs, the decomposition rate of the co-reaction reagent H2O2 was largely improved, generating more ROS for signal amplification. Using the N-(4-aminobutyl)-N-ethylisoluminol (ABEI) as ECL luminophore, a new signal tag was acheived according to the assembly of ABEI functionalized Ag NPs (ABEI-Ag) on the CoS NFs via Ag-S bond, which integrated with the ECL luminophore and bis-co-reaction accelerator. In addition, to fabricate sensing interface, primary antibodies (Ab1) was immobilized on the glassy carbon electrode which decorated with Au nanoparticles (Au NPs), almost providing a zero background signal. As a result, this developed immunosensor for cTnT possessed a linear range from 0.1 fg mL−1 to 100 pg mL−1 and the limit of detection down to 0.03 fg mL−1 for ultrasensitive detection of cTnT, which was expected to be applicable to cTnT detection in clinic acute myocardial infarction.

Development of o-phthalic anhydride as a low-temperature activator in H2O2 bleaching system for cotton fabric

O-phthalic anhydride (PA) was developed as a low-temperature activator in the H2O2 bleaching system for cotton fabric. The performance of the H2O2/PA bleaching system was investigated by measuring the CIE whiteness index (WI) of the bleached cotton fabric, H2O2 decomposition rate and bursting strength, respectively. The effects of experimental conditions, including PA dosage, bleaching time, bleaching temperature and NaOH concentration, were discussed in the H2O2/PA bleaching system. Upon addition of PA, the WI and H2O2 decomposition rate increased significantly at 70 °C. The results showed that the bleaching system had a promising application prospect. Compared with the H2O2 system, the H2O2/PA system significantly promoted 1O2 generation under the same alkali condition by using 9,10-dimethylanthracene as a fluorescent probe for 1O2. And the generation of large amount of 1O2 did not obviously affect the bleaching performance in the H2O2/PA system. By using benzenepentacarboxylic acid as a fluorescent probe for HO· detection, it was found that the fluorescence intensity was enhanced 14 folds in the presence of PA, indicating that PA could strongly promote HO· generation. By using dimethyl sulfoxide as a scavenger to control HO· concentration, it was found that the WI of the fabric was closely related to the HO· concentration, revealing that the HO· could play an important role in the bleaching process. Phthalic acid was also added to the H2O2 bleaching system to investigate potential bleaching route of the H2O2/PA system. Based on these experimental results, a possible bleaching mechanism of the H2O2/PA system was proposed.

Hybrid composites based on technical cellulose from rice husk

ABSTRACTWe introduced the preparation of hybrid composites using technical cellulose as a matrix material from rice husks with a natural SiO2 content from 0% to 19.4%. In this work, the physicochemical characteristics of the resulting hybrid composites have been investigated. The presence of SiOC chemical bonds in the resulting hybrid composites was determined by infrared spectroscopy. Microscopic analysis showed the complete removal of the mineral component and lignin from the cell wall of the rice husk fibers. This allows obtaining of an expanded surface of the fibers (101.7 m2/g) with uniform distribution of the TiO2 aggregates. It could be shown that with content increasing of natural silicon dioxide in the hybrid composite the decomposition rate of H2O2 also increases. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45796.

Hot electron flux at solid–liquid interfaces probed with Pt/Si catalytic nanodiodes: Effects of pH during decomposition of hydrogen peroxide

Hydrogen peroxide (H2O2) is an effective oxidizing agent that is commonly used in industry. In the presence of metal catalysts, H2O2 can decompose into water and oxygen. Understanding this process at a fundamental level is extremely important for a number of industrial applications, e.g. the direct synthesis of H2O2 from H2 and O2. Here, we studied the rates of H2O2 decomposition on Pt/n-Si catalysts using a chemicurrent approach that is based on the detection of hot electrons created during dissociative adsorption of H2O2 molecules on platinum. We showed that both the rate of H2O2 decomposition and the corresponding chemicurrent are sensitive to the pH of the reactive solution. This phenomenon is explained by variation of the potential barrier for electron transfer at the Pt/solution interface caused by adsorption of H+ and OH− species from the solution on the catalytic surface.

Radiolytic Synthesis of Pt-Particle/ABS Catalysts for H₂O₂ Decomposition in Contact Lens Cleaning.

A container used in contact lens cleaning requires a Pt plating weight of 1.5 mg for H2O2 decomposition although Pt is an expensive material. Techniques that decrease the amount of Pt are therefore needed. In this study, Pt nanoparticles instead of Pt plating film were supported on a substrate of acrylonitrile–butadiene–styrene copolymer (ABS). This was achieved by the reduction of Pt ions in an aqueous solution containing the ABS substrate using high-energy electron-beam irradiation. Pt nanoparticles supported on the ABS substrate (Pt-particle/ABS) had a size of 4–10 nm. The amount of Pt required for Pt-particle/ABS was 250 times less than that required for an ABS substrate covered with Pt plating film (Pt-film/ABS). The catalytic activity for H2O2 decomposition was estimated by measuring the residual H2O2 concentration after immersing the catalyst for 360 min. The Pt-particle/ABS catalyst had a considerably higher specific catalytic activity for H2O2 decomposition than the Pt-film/ABS catalyst. In addition, sterilization performance was estimated from the initial rate of H2O2 decomposition over 60 min. The Pt-particle/ABS catalyst demonstrated a better sterilization performance than the Pt-film/ABS catalyst. The difference between Pt-particle/ABS and Pt-film/ABS was shown to reflect the size of the O2 bubbles formed during H2O2 decomposition.

Constructing highly catalytic oxidation over BiOBr-based hierarchical microspheres: Importance of redox potential of doped cations

In this work, we prepared BiOBr-based hierarchical microspheres by a simple solvothermal method. The phase structure, morphology and optical properties of catalysts were well characterized by XRD, FESEM, FTIR, UV-DR spectra, XPS valence band and BET surface area analysis. Among the Vis/catalyst/H2O2 system, Cu-BiOBr is found to be the most effective for rhodamine b degradation while Fe-BiOBr exhibits the highest catalytic activity for the mineralization of 2-chlorophenol. Hydroxyl radicals generation rate and H2O2 decomposition rate follow: Fe-BiOBr>BiOBr>Zn-BiOBr=Ni-BiOBr=Ag-BiOBr>Cu-BiOBr, and Cu-BiOBr>Fe-BiOBr>BiOBr=Zn-BiOBr=Ni-BiOBr>Ag-BiOBr, respectively. The catalytic mechanisms under Vis/catalyst/H2O2 systems are proposed and compared, as following: (1) for BiOBr/Zn-BiOBr/Ni-BiOBr/Ag-BiOBr, the activation of H2O2 by photoelectrons to generate hydroxyl radical; (2) for Fe-BiOBr, the reaction of Fe(II) or photoelectrons with H2O2 to produce hydroxyl radical, and Fe(III) is reduced by photoelectrons to Fe(II); (3) for Cu-BiOBr, the activation of H2O2 by photoelectrons to generate hydroxyl radical that probably oxides Cu(II) to Cu(III), and the reaction of Cu(I) with H2O2 to generate Cu(III). The trapping experiments display that holes and hydroxyl radicals (or Cu(III)) have dominant roles.

The role of exposed facets in the Fenton-like reactivity of CeO2 nanocrystal to the Orange II

Recently, ceria-based Fenton-like reactions have been developing in wastewater treatment. Nevertheless, the effects of geometric (exposed facets) of the CeO2 on its Fenton-like reactivity have rarely been considered. In this work, shaped CeO2 nanocrystals with different exposed facets were synthesized and applied in the Fenton-like degradation of Orange II (AO7). Due to the relative low oxygen vacancy formation energy on {110} facet, H2O2 decomposition shows higher apparent activation energy with nanocubes ({100} facet) than that with nanorods ({110} and {100} facets). CeO2 nanorods calcined at 300°C exhibits the maximal activity for the decomposition of H2O2, while that for the Fenton-like degradation of AO7 is achieved with CeO2 nanorods calcined at 500°C. Calcination at higher temperature decreases the surface Ce(III) content of CeO2, thus lowers the H2O2 decomposition rate. On the contrary, the decrescent formation energy of oxygen vacancy, the decreased amount of surface hydroxyls, as well as reduced coordination status of surface Ce cations, play important roles in promoting the adsorption and Fenton-like degradation of AO7 for CeO2 nanorods calcined at 500°C.

Catalytic effect of low concentration carboxylated multi-walled carbon nanotubes on the oxidation of disinfectants with Cl-substituted structure by a Fenton-like system

Carbon nanotubes (CNTs) have attracted increasing attentions due to their numerous potential applications. Their applications as catalysts or catalyst carriers have been the focus of many recent studies. In this paper, the role of carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) played in the degradation of triclosan (TCS), chlorofene (CF) and dichlorofene (DCF) by a Fenton-like system Fe3+/H2O2 was investigated. The results indicated that MWCNTs-COOH exhibited significant catalytic effect on TCS, CF and DCF removal. Meanwhile, the structure and chemical composition of MWCNTs-COOH did not show significant change after the oxidative reaction process, which has been characterized by TEM, Raman spectroscopy, XPS, and FT-IR. Taking TCS for example, increasing initial Fe3+ ion and H2O2 concentrations and reaction temperature favored the decomposition of TCS, while the optimal concentration of MWCNTs-COOH at 2.0ppm was observed. When [Fe3+]=0.04mmoldm−3, [H2O2]=0.6mmoldm−3, [MWCNTs-COOH]=2.0ppm, [TCS]=0.02mmoldm−3, at pH 4.0 and 25°C, the TCS removal efficiency was 97.0% after 30min and the total organic carbon (TOC) removal was 64.5% after 90min. Mechanism study showed that the reduction rate of Fe3+ ion to Fe2+ ion and the decomposition rate of H2O2 were both increased in the presence of MWCNTs-COOH, thus lead to the enhanced production of hydroxyl radicals (OH), which is the dominant reactive species responsible for TCS oxidation. Seven intermediates of TCS were identified by TOF-LC-MS, and their structures were further rationalized by frontier electron density (FED) calculations. Major oxidation pathways including hydroxylation, dechlorination and cleavage of the ether bond were tentatively proposed, and detailed underlying mechanisms were also discussed.

Kinetic and spectroscopic evidence for reaction pathways and intermediates for olefin epoxidation on Nb in *BEA

The selective epoxidation of olefins with hydrogen peroxide (H2O2) over transition metal substituted zeolites is less environmentally impactful than epoxidation schemes that use chlorinated or organic oxidants. The structure and reactivity of reactive intermediates derived from H2O2 and the mechanism for olefin epoxidation on such materials are debated. Here, cyclohexene oxide formation and H2O2 decomposition rates (measured as functions of reactant and product concentrations) and in situ infrared (IR) and UV-vis spectroscopy are used to probe the intervening elementary steps for cyclohexene (C6H10) epoxidation and the identity of the reactive intermediates on a Nb-β catalyst. IR and UV-vis spectra acquired in situ show that the reactive intermediates are predominantly superoxide species (NbIV-(O2)−, observed also by X-ray photoelectron spectroscopy), which form by the irreversible activation of H2O2 over Nb centers. Similar M-(O2)∗ (M=Ti or Ta) intermediates were previously assumed to form via reversible processes; however, in situ IR and UV-vis measurements directly show that NbIV-(O2)− forms irreversibly in both H2O and acetonitrile. Activation enthalpies (ΔH‡) for C6H10 epoxidation are 27kJmol−1 higher than for H2O2 decomposition, while activation entropies (ΔS‡) for epoxidation are 56Jmol−1K−1 lower than for H2O2. These comparisons show that the selectivities for epoxidation, via primary reaction pathways, increase with increasing reaction temperatures. Collectively, these results provide a self-consistent mechanism for C6H10 epoxidation that is also in agreement with previously published data. These findings will aid the rational design and study of alternative metal oxide catalysts for olefin oxidation reactions.

Novel feed including bioactive compounds from winery wastes improved broilers' redox status in blood and tissues of vital organs

Currently, there is a great interest in the production of animal feed with antioxidant activity. The aim of this study was to examine the potential antioxidant effects of a feed supplemented with grape pomace (GP), a winery by-product with high environmental load, in chickens. Broilers of 15 days post birth were separated into two groups fed either with standard diet or with diet supplemented with GP for 35 days. Blood and tissues collections were performed after feeding for 15 and 35 days with the experimental diet (i.e. at 30 and 50 days post birth). Free radical toxicity markers, namely thiobarbituric acid reactive substances, protein carbonyls, total antioxidant capacity, reduced glutathione, catalase activity and rate of H2O2 decomposition were determined in blood and tissues of vital organs. The results indicated that feed supplemented with GP decreased oxidative stress-induced toxic effects and improved chickens’ redox status, and so it may also improve their wellness and productivity. On the other hand, this exploitation of GP may solve problems of environmental pollution in areas with wineries.

Low-temperature bleaching of cotton knitting fabric with H2O2/PAG system

Pentaacetyl glucose (PAG) is a common and cheap intermediate and has biocompatible, nontoxic, and renewable features. PAG was investigated as a bleach activator for H2O2 in the pretreatment of gray knitting cotton fabric. The bleaching performance of the H2O2/PAG bleaching system was investigated by measuring the CIE whiteness index (WI), H2O2 decomposition rate and bursting strength. By addition of PAG, the WI and H2O2 decomposition rate increased significantly at 70 °C with little damage to the strength. The effects of temperature and pH value on WI were also considered. Due to its environmental advantages, the H2O2/PAG system showed a good applied prospect. By using benzenepentacarboxylic acid as a fluorescent probe for HO· detection, it was found that PAG could strongly promote HO· generation and that the concentration of HO· was closely related to the WI of the fabric. On this basis, a bleaching mechanism of the H2O2/PAG system was proposed.

Naturally-occurring iron minerals as inexpensive catalysts for CWPO

This work explores the potential application of naturally-occurring minerals as inexpensive catalysts in heterogeneous Fenton, namely catalytic wet peroxide oxidation (CWPO). The availability, low cost and environmentally friendly character of those materials make them interesting candidates for such application. The performance of magnetite, hematite and ilmenite as CWPO catalysts has been tested under different working conditions, which include temperature (25–90°C), H2O2 dose (250–1000mgL−1) and catalyst concentration (1–4gL−1). The operating temperature plays a key role on the rate of H2O2 decomposition so that with magnetite H2O2 conversion after 4h increased from 8 to 99% by increasing the temperature from 25 to 90°C. Based on the reaction mechanism proposed, a kinetic model was developed which successfully described the experimental results on H2O2 decomposition. The catalytic performance of the minerals tested at temperatures above the ambient was demonstrated using phenol (100mgL−1) as target pollutant. Unprecedented efficiencies of H2O2 consumption, higher than 80% were achieved, allowing high oxidation and mineralization, i.e. complete phenol conversion and almost 80% TOC reduction at 75°C with a catalyst loading of 2gL−1 and the theoretical stoichiometric amount of H2O2 for complete mineralization of phenol (500mgL−1). Magnetite is particularly attractive, since it showed the highest activity and can be easily separated from the liquid phase given its magnetic properties. All the minerals tested suffered low iron leaching and magnetite and hematite showed a good reusability upon three consecutive runs. However, in this case long-term durability is not a crucial issue, given the availability and low cost of these minerals.

The dual role of Escherichia coli in the course of ulcerative colitis.

BackgroundThis study examines the dual role of Escherichia coli in the course of ulcerative colitis (UC). The intestinal microbiota is considered to play an important role in UC pathogenesis, but how E. coli contributes to inflammation in UC is still unknown. On the one hand, we demonstrated that there was a significant increase in the number of E. coli at the sites of inflammation in patients with UC, which can lead to immune system activation, whilst, on the other hand, E. coli may contribute to the resolution of inflammatory reactions since E. coli can inhibit hydroxyl radical formation by eliminating substrates of the Fenton reaction, by assimilating ferrous iron (Fe2+) and inducing the decomposition of hydrogen peroxide (H2O2). On this way, E. coli may affect the initiation and/or prolongation of remission stages of UC.MethodsTen E. coli strains were isolated from the colonic mucosa of patients in the acute phase of UC. Using PCR, we examined the presence of genes encoding catalases (katG and katE) and proteins participating in iron acquisition (feoB, fepA, fhuA, fecA, iroN, fyuA, and iutA) in these E. coli strains. To determine if iron ions influence the growth rate of E. coli and its ability to decompose H2O2, we grew E. coli in defined culture media without iron (M9(-)) or with ferrous ions (M9(Fe2+)). Expression levels of genes encoding catalases were examined by real-time PCR.ResultsAll investigated E. coli strains had catalase genes (katG, katE), genes coding for receptors for Fe2+ (feoB) and at least one of the genes responsible for iron acquisition related to siderophores (fepA, fhuA, fecA, iroN, fyuA, iutA). E. coli cultured in M9(Fe2+) grew faster than E. coli in M9(-). The presence of Fe2+ in the media contributed to the increased rate of H2O2 decomposition by E. coli and induced katG gene expression.Conclusions E. coli eliminates substrates of the Fenton reaction by assimilating Fe2+ and biosynthesizing enzymes that catalyze H2O2 decomposition. Thus, E. coli can inhibit hydroxyl radical formation, and affects the initiation and/or prolongation of remission stages of UC.

Effects of hydrogen and propylene presence on decomposition of hydrogen peroxide over palladium catalysts

Reaction rates for H2O2 decomposition in a methanol solution were measured over Pd/SiO2 catalysts in the presence of gas-phase N2, H2 and propylene. The H2O2 decomposition rates were higher in the presence of H2 and lower in the presence of propylene compared to those under N2, which acted as an inert gas. For interpretation of the experimental results, H2O2 decomposition reactions were evaluated with density functional theory calculations on four Pd(111) surfaces: (1) clean, (2) with pre-adsorbed hydrogen, (3) with molecularly pre-adsorbed propylene, and (4) with dissociatively pre-adsorbed propylene. The computational results show that the mechanism of H2O2 decomposition can proceed through O—O and O—H bond splitting reactions. The O—O bond splitting reactions are energetically preferable because they are exothermic and have lower activation energies. However, in the absence of H2, the endothermic O—H bond splitting reactions with higher activation energies are required for the formation of molecular decomposition products: O2 and H2O. In contrast, in the presence of H2, the O—H bond splitting reactions are no longer required, and the H2O2 decomposition can proceed only through the facile O—O bond splitting reaction in H2O2. The formed surface OH species can readily react with H species from dissociative H2 adsorption, forming H2O as the only product. This change in the reaction mechanism from the O—H bond splitting to the O—O bond splitting explains the experimentally observed higher H2O2 decomposition rates in the presence of H2. The lower H2O2 decomposition rates in the presence of propylene are due to blocking of Pd surface sites by hydrocarbon species formed on propylene adsorption. Although propylene does not directly participate in H2O2 decomposition, it adsorbs on Pd more strongly than H2O2 and, therefore, forms surface spectator species that reduce the number of Pd active sites.

Modified ilmenite as catalyst for CWPO-Photoassisted process under LED light

The influence of the iron chemical nature contained in ilmenite (FeTiO3) upon the activity and stability of these materials as catalysts for CWPO-Photoassisted process under LED light (λ: 405nm) were evaluated. Raw ilmenite was treated with H2 within the range 25–1000°C in order to partially reduce iron oxides to Fe(0). The catalysts were characterized by N2 adsorption/desorption, TXRF, XRD and XPS analysis. The co-presence of different iron species (Fe(0), Fe(II) and Fe(III)) along with the light effect over material surface, led to an increase of H2O2 decomposition rate into HO and, therefore, a higher oxidation rate. In all case, after total H2O2 depletion, a complete phenol degradation and a 95% TOC conversion was reached in batch at pH0=3 and 50°C using the stoichiometric H2O2 dose (14mol H2O2/mol phenol) and 10Wm−2 LED light. Long-term continuous experiments were carried out to assess the stability and the lifetime of the catalyst. The higher reduction degree led to a higher organic matter mineralization but also to a higher leaching of active phase around 3% of the total iron amount in ilmenite. Nevertheless, catalyst deactivation seems to be related to the oxidation of iron on the catalyst surface.

Assembly of transition metal ion on cellulose surface anchored with azo-Schiff base and its catalytic activity for H2O2 decomposition

To form polymer-supported catalysts, to eliminate excess H2O2 during wastewater treatment, the assembly of metal ion on cellulose was investigated. Cellulose was covalently grafted with reactive azo-Schiff base containing azo-conjugated system, 3,5-bis {2-hydroxyphenyl-5-[(2-sulfate-4-sulfatoethylsulphonyl-azobenzol) methylene amino]} benzoic acid. Metal ions, Co2+, Mn2+, and Cu2+, were anchored to the modified cellulose by controlling assembly. The cellulose-supported complexes were characterized and the catalytic activity for H2O2 was investigated. Elemental analyses of the cellulose supported complexes, MC–Co, MC–Mn, were well agreed with the proposed composition. Three cellulose-supported complexes had strong catalytic activities for H2O2. H2O2 decomposition rates in 10 min were 84.54% for MC–Co, 94.87%, for MC–Mn, and 77.21% for MC–Cu, respectively. The manganese complex had the strongest catalytic activity among them. The cellulose-supported complexes have potential application in wastewater treatment and biotechnology.

Comparison of phenacetin degradation in aqueous solutions by catalytic ozonation with CuFe2O4 and its precursor: Surface properties, intermediates and reaction mechanisms

In this study, a new magnetic catalyst for enhancing the ozonation process, named as CFOH, a precursor of CuFe2O4 (CFO) was used to enhance the ozonation. The comparison of the surface properties, performance, and reaction mechanisms of CFO and CFOH in catalytic ozonation was investigated. The CFOH showed higher surface area, pore volume, and stronger acidic sites than those of CFO. Importantly, both CFOH and CFO exhibited magnetization, which can be used to separate the catalysts from the bulk solution for reuse. In addition, faster degradation and mineralization of phenacetin (PNT) in catalytic ozonation by CFOH were observed. The generation/decay of intermediates and H2O2 were identified in the studied processes. The yield and decomposition rate of H2O2 in the reaction determined the concentration of OH, which was found to be the key for the better catalytic activity of CFOH. Furthermore, the fates of benzene- and open-ring intermediates in the processes were also investigated. The surface reactions, including surface adsorption and catalytic reaction were observed for the mineralization of intermediates generated from PNT oxidation. These surface reactions became more significant when using CFOH as the catalyst, which justifies the better mineralization ability of CFOH.