Stoichiometric Amount Of H2O2 Research Articles

Surface modification of arsenic sulfide particles for their stabilization

Arsenic sulfide slag (ASS), the product of sulfide precipitation from arsenic wastewater, needs further processing to protect the environment. Oxidation of trivalent to pentavalent arsenic with H2O2 and stabilization of arsenic with CaO in the form of water-insoluble calcium arsenate, Ca3(AsO4)2, are now relatively mature methods. Their disadvantages, however, are the large amounts of sludge produced and of the oxidant H2O2 used. In this paper, to reduce the use of lime and the oxidizing agent, surface modification of arsenic sulfide particles (ASP) was studied. ASS was mixed with calcium oxide in different proportions to obtain mixed slag which was oxidized with hydrogen peroxide. High-resolution spectroscopic examination showed that calcium arsenate completely covered the ASP surface when the stoichiometric amounts of H2O2 and CaO were 50 and 100%, respectively. The stability of the arsenic in the surface modified ASP was evaluated using USEPA toxicity characteristics leaching procedure (TCLP) in which the ASS was cured with cement. The arsenic leaching concentration from the solidified body in which the ASS to cement ratio is 1:2 could be reduced to 0.63 mg/L for dosages of 30% CaO and >30% H2O2, which is lower than the USEPA and Chinese regulatory thresholds of 5 mg/L and 1.2 mg/L, respectively. The method developed successfully saves a large quantity of the hydrogen peroxide oxidant and has the potential to reduce industrial toxic arsenic slag discharge.

Increasing Photo-Fenton process Efficiency: The effect of high temperatures

The possibility to intensify the homogeneous photo-Fenton by increasing temperature (up to 90 °C) has been deeply investigated using phenol as model pollutant and treating a real landfill leachate effluent. TOC removal rate was significantly improved as temperature increases. The required irradiation time to mineralize 1 g/L of phenol using the stoichiometric amount of H2O2 and 10 mg/L Fe2+ decreases from 120 min at 50 °C to less than 30 min when the experiments were carried out at 90 °C. Besides, within this range, the value of H2O2 consumption efficiency (ηH2O2), defined here as g of TOC converted per g of H2O2 consumed, was maintained around 0.15, which confirm the scarce effect of thermal H2O2 decomposition into O2 and H2O. More interestingly, the Irradiation Energetic Efficiency, defined as the TOC converted per W-h of energy emitted to the solution, dramatically increased with temperature, with a maximum value of 1.04 g of TOC per W-h reached at 90 °C. These results significantly improve those reached using dark Fenton under comparable experimental conditions. Similar trend was observed when high temperature photo-Fenton was applied to landfill leachates, using the stoichiometric amount of H2O2 (2.12 g/g COD) and 10 mg/L Fe2+. The required irradiation time to achieve maximum TOC and COD removals (around 80%) was reduced from 180 to 45 min by increasing temperature from 50 to 90 °C and the irradiation efficiency increased 4-fold withing this range of temperature. In addition, a kinetic model has been proposed to fit TOC evolution in both phenol and the leachate treatment. According to this, firstly temperature promotes the rapid degradation of TOC by the hydroxyl radicals produced by Fenton reaction decreasing the wastewater turbidity and colour. Subsequently, photo-Fenton reaction plays a key role, promoting organic acids and other by-products mineralization. The results of this paper reveal that, far from being a drawback due to undesirable H2O2 thermal decomposition into O2 and H2O, high temperatures could be efficiently used to enhance the cost-efficiency of photoassisted processes. To the best of our knowledge, this is the first time that such a wide range of temperature up to 90 °C is explored. Thereby, the outcomes of this research confirm temperature as a promising way to intensify photoassisted treatments, reducing both the reaction time and the required energy (W-h) and operational costs to partially oxidized and/or mineralize organic matter in highly organic loaded wastewaters.

Long‐Living Holes in Grey Anatase TiO2 Enable Noble‐Metal‐Free and Sacrificial‐Agent‐Free Water Splitting

Titanium dioxide has been the benchmark semiconductor in photocatalysis for more than 40 years. Full water splitting, that is, decomposing water into H2 and O2 in stoichiometric amounts and with an acceptable activity, still remains a challenge, even when TiO2‐based photocatalysts are used in combination with noble‐metal co‐catalysts. The bottleneck of anatase‐type TiO2 remains the water oxidation, that is, the hole transfer reaction from pristine anatase to the aqueous environment. In this work, we report that “grey” (defect engineered) anatase can provide a drastically enhanced lifetime of photogenerated holes, which, in turn, enables an efficient oxidation reaction of water to peroxide via a two‐electron pathway. As a result, a Ni@grey anatase TiO2 catalyst can be constructed with an impressive performance in terms of photocatalytic splitting of neutral water into H2 and a stoichiometric amount of H2O2 without the need of any noble metals or sacrificial agents. The finding of long hole lifetimes in grey anatase opens up a wide spectrum of further photocatalytic applications of this material.

Degradation of widespread cyanotoxins with high impact in drinking water (microcystins, cylindrospermopsin, anatoxin-a and saxitoxin) by CWPO

The occurrence of harmful cyanobacterial blooms has unabated increased over the last few decades, posing a significant risk for public health. In this work, we investigate the feasibility of catalytic wet peroxide oxidation (CWPO) promoted by modified natural magnetite (Fe3O4-R400/H2O2), as an inexpensive, simple-operation and environmentally-friendly process for the removal of the cyanotoxins that show the major impact on drinking water: microcystins (MC-LR and MC-RR), cylindrospermopsin (CYN), anatoxin-a (ATX) and saxitoxin (STX). The performance of the system was evaluated under ambient conditions and circumneutral pH (pH0 = 5) using relevant cyanotoxin concentrations (100–500 μg L−1). The nature of the cyanotoxins determined their reactivity towards CWPO, which decreased in the following order: MC-RR > CYN > MC-LR ≫ ATX > STX. In this sense, microcystins and CYN were completely removed in short reaction times (1–1.5 h) with a low catalyst concentration (0.2 g L−1) and the stoichiometric amount of H2O2 (2–2.6 mg L−1), while only 60–80% conversion was achieved with ATX and STX in 5 h. In these cases, an intensification of the operating conditions (1 g L−1 catalyst and up to 30 mg H2O2 L−1) was required to remove both toxins in 1 h. The impact of the main components of freshwaters i.e. natural organic matter (NOM) and several inorganic ions (HCO3−, HPO42-, SO42-) on the performance of the process was also investigated. Although the former led to a partial inhibition of the reaction due to HO· scavenging and catalyst coating, the latter did not show any remarkably effect, and the versatility of the process was finally confirmed in a real surface water. To further demonstrate the effectiveness of the catalytic system, the toxicity of both the initial cyanotoxins and the resulting CWPO effluents was measured with the brine shrimp Artemia salina. Remarkably, all CWPO effluents were non-toxic at the end of the treatment.

Carbon nanotubes as catalysts for wet peroxide oxidation: The effect of surface chemistry

Three magnetic carbon nanotube (CNT) samples, named A30 (N-doped), E30 (undoped) and E10A20 (selectively N-doped), synthesized by catalytic chemical vapor deposition, were modified by introducing oxygenated surface groups (oxidation with HNO3, samples CNT-N), and by heat treatment at 800 °C for the removal of surface functionalities (samples CNT-HT). Both treatments lead to higher specific surface areas. The acid treatment results in more acidic surfaces, with higher amounts of oxygenated species being introduced on N-doped surfaces. Heat-treated samples are less hydrophilic than those treated with nitric acid, heat treatment leading to neutral or basic surfaces, only N-quaternary and N-pyridinic species being found by XPS on N-doped surfaces. These materials were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated 4-nitrophenol solutions (4-NP, 5 g L−1) at atmospheric pressure, T = 50 °C and pH = 3, using a catalyst load of 2.5 g L−1 and the stoichiometric amount of H2O2 needed for the complete mineralization of 4-NP. The high temperature treatment enhanced significantly the activity of the CNTs towards CWPO, evaluated in terms of 4-NP and total organic carbon conversion, due to the increased hydrophobicity of their surface. In particular, E30HT and E10A20HT were able to remove ca. 100% of 4-NP after 8 h of operation. On the other hand, by treating the CNTs with HNO3, the activity of the less hydrophilic samples decreased upon increasing the concentration of surface oxygen-containing functionalities, whilst the reactivity generated inside the opened nanotubes improved the activity of the highly hydrophilic A30 N.

Iron catalyst supported on modified kaolin for catalytic wet peroxide oxidation

AbstractAn iron catalyst supported on the modified Tamazert kaolin has been prepared and tested in catalytic wet peroxide oxidation using phenol and 4-chlorophenol (4-CP) as target compounds (100 mg/L initial concentration). Kaolin is not usually employed as a catalytic support due to its low developed porous structure, but its textural properties may be improved upon calcination and acid and basic treatment. The catalyst was characterized by N2 adsorption–desorption and chemical analysis by total-reflection X-ray fluorescence spectroscopy. The catalytic tests were carried out in a batch reactor with a stoichiometric amount of H2O2. The catalytic efficiency was studied within the temperature range of 25–55°C at an initial pH of 3.3 and 1 g/L catalyst. Complete phenol and 4-CP removal was achieved with no significant differences in phenol and 4-CP conversions within the temperature range tested. Meanwhile, total organic carbon (TOC) reduction was greatly favoured by increasing the temperature, which may be partially attributed to a probable contribution of a homogeneous reaction associated with iron leaching. However, this effect might be of limited significance because the highest concentrations of iron in the liquid phase were below 4.5 and 8.5 mg/L in the experiments with phenol and 4-CP, respectively. At 55°C, TOC was reduced by ~70% after 4 h reaction time, with the remaining by-products corresponding almost completely to low-molecular-weight carboxylic acids of very low ecotoxicity.

Synthesis of coal fly ash zeolite for the catalytic wet peroxide oxidation of Orange II.

Fly ash, a coal combustion residue produced by Termotasajero in Colombia, has been hydrothermally treated after an alkaline fusion to produce zeolite without addition of silicon or aluminum. The starting material was thoroughly mixed with NaOH, in a 1:1.2 mass ratio, to obtain a homogeneous mixture that was heated to 100°C during different times (6, 8, and 10h) and three zeolite samples were produced. The samples were characterized by XRD, SEM, XRF, Mössbauer spectroscopy, and N2 physisorption. According to characterization results (high surface area and appropriate morphological properties including crystallinity) and synthesis time, zeolitic catalyst synthesized with 8h of hydrothermal treatment was selected to perform further analysis. This sample consisted of a mixture of zeolite X and zeolite A of high surface area (301m2g-1) and a Fe content of 6% wt/wt. The zeolite was used as a catalyst for the Fenton oxidation of Orange II. Experiments were performed in a laboratory batch reactor at 70°C and constant pH = 3, using different concentrations of H2O2. When the stoichiometric amount of H2O2 was used, good mineralization (XTOC = 45%), complete discoloration, and oxidant consumption were obtained after 240min of reaction. The sample retained activity after 16h of usage. The presence of Fe in the reaction media was always detected and a homogeneous Fenton mechanism induced by surface-leached iron is suggested.

Performance of electro-Fenton process for phenol removal using Iron electrodes and activated carbon

The objective of the present study was to investigate the efficacy of electro-Fenton (EF) oxidation process for the removal of phenol from synthetic wastewater (initial phenol concentration = 250 mg/L) under varying reaction conditions using iron electrodes. The lab scale EF runs were performed in a 1 L beaker placed on magnetic stirrer assembly. Maximum COD and TOC removals of ∼84% and ∼52%, respectively, were obtained within 30 min reaction at the following operating conditions: stoichiometric amount of H2O2 = 37.2 mM, pH = 5.2 (unadjusted), electrical conductivity = 125 μS/cm (adjusted using NaCl), stirring speed = 100 rpm, current density = 0.8 mA/cm2 and inter-electrode gap = 4 cm. At the above condition, complete phenol removal was obtained within 5 min. The effect of activated carbon (AC) as co-catalyst on the performance of EF process was also studied at the above reaction condition. With AC assisted EF process, TOC removal was increased to 75% from 52.2% (in EF). The enhanced degradation was due to the combined effect of adsorption and oxidation reactions. During modified EF, ferrous iron recycling was also higher compared to that observed during conventional EF process.

Treatment of hospital wastewater through the CWPO-Photoassisted process catalyzed by ilmenite

In this work, the feasibility of the CWPO-Photoassisted process for the on-site treatment of real hospital wastewaters has been evaluated using the low-cost mineral ilmenite. The ability of the process for the degradation of pharmaceuticals was firstly demonstrated in both deionized water and hospital wastewater matrices. Although the latter led to slow constant rates due to scavenging effects (0.42 and 0.02min−1, respectively), the complete elimination of the pharmaceuticals was reached in both cases operating at 30°C and using 1gL−1 ilmenite. The complete removal of coliforms in the hospital wastewater was also achieved. The treatment of the hospital wastewater was fairly efficient (TOC conversion above 80% in 5h reaction time) operating at 50°C with a catalyst load of 1gL−1 and the stoichiometric amount of H2O2, which was attributed to the combination of both CWPO and photocatalytic reactions. A lumped kinetic model allowed to describe fairly well the evolution of the global parameters viz. TOC and H2O2 along the process where both CWPO and photocatalytic reactions were considered. The unique properties of ilmenite allowed the fast degradation of the organic pollutants by CWPO into hydroxylated species, while further photocatalysis led to the formation of short-chain organic acids and their subsequent mineralization. Finally, the stability of ilmenite was confirmed upon three sequential runs.

Application of intensified Fenton oxidation to the treatment of hospital wastewater: Kinetics, ecotoxicity and disinfection

Fenton oxidation has proved to be effective for the treatment of a real hospital wastewater. The intensification of the process viz. the improvement on the efficiency of H2O2 consumption, by increasing the temperature, is necessary to operate in a single step and avoid high reaction times and the need of large H2O2 and iron concentrations. This approach would allow taking advantage of the heat energy contained in the laundry stream since the washing process is performed at high temperature to assure disinfection of the hospital textiles. In this work, temperatures within the range of 50–90°C have been tested, which allowed an effective oxidation of the real wastewater ([COD]0=365mgL−1, [Phenols]0=8.4mgL−1, [total coliforms]0=4.16×106 MPN/100mL, 5 toxicity units) with the stoichiometric amount of H2O2 (1000mgL−1) and a relatively low iron concentration (25mgL−1 Fe3+). Operating at 90°C, complete disappearance of phenolic compounds and 70% and 50% reduction of COD and TOC were achieved in 1h reaction time. Time evolution of those global parameters were appropriately fitted to pseudo-first and second order kinetic equations, providing a useful approach for design purposes. The main by‐products were short-chain organic acids (oxalic and formic), being the final effluents non-toxic. Disinfection of the hospital wastewater was also achieved at all the operating temperatures tested, as confirmed by the absence of coliforms.

Role of Nitrogen Doping on the Performance of Carbon Nanotube Catalysts: A Catalytic Wet Peroxide Oxidation Application

AbstractFour magnetic carbon nanotube (CNT) samples (undoped, completely N‐doped, and two selectively N‐doped) were synthesized by chemical vapor deposition. The materials were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated 4‐nitrophenol solutions (4‐NP, 5 g L−1). Relatively mild operating conditions were considered (atmospheric pressure, T=50 °C, pH 3), using a catalyst load of 2.5 g L−1 and the stoichiometric amount of H2O2 needed for the complete mineralization of 4‐NP. N‐doping was identified to influence considerably the CWPO performance of the materials. In particular, undoped CNTs, with a moderate hydrophobicity, favor the controllable and efficient decomposition of H2O2 into highly reactive hydroxyl radicals (HO.), thus showing high catalytic activity for 4‐NP degradation. On the other hand, the completely N‐doped catalyst, fully hydrophilic, favors a quick decomposition of H2O2 into nonreactive O2 and H2O species. The selectively N‐doped amphiphilic catalysts, that is, hybrid structures containing undoped sections followed by N‐doped ones, provided intermediate results, namely, a higher N content favored H2O2 decomposition towards nonreactive H2O and O2 species, whereas a lower N content resulted in the formation of HO., increasing 4‐NP mineralization. Catalyst stability and reusability were also investigated by consecutive CWPO runs.

UV-LED assisted catalytic wet peroxide oxidation with a Fe(II)-Fe(III)/activated carbon catalyst

This study assesses the effect of UV LED radiation on the activity and stability of an activated carbon supported iron catalyst in catalytic wet peroxide oxidation (CWPO). Experiments were carried out with a Fe(II)-Fe(III) on activated carbon catalyst, named Fe/ACM, (4wt% Fe) in a counter-flow quartz concentric tubular reactor (useful volume: 100mg/L) surrounded by a commercial LED strip (length: 5m, 120 LEDs/m, wavelength: 400nm, irradiance: 10W/m2). Phenol was used as target compound at 100mg/L and the H2O2 dose was varied within 100–500mg/L, the latter corresponding to the theoretical stoichiometric amount. The rest of operating conditions were: Ccatalyst: 500mg/L, pH0: 3 and T: 50°C. UV-LED radiation promotes the reduction of Fe3+ to Fe2+ on the catalyst surface, increasing the oxidation rate as a result of the higher H2O2 decomposition into HOX (HO and HOO) radicals. Besides, UV-LED radiation easily mineralized oxalic acid, which dramatically reduces the leaching of the active phase (from 17% to less than 4%, without and with irradiation, respectively after 180min) and increases the life cycle of the catalyst. Thus, a complete H2O2 decomposition and more than 98% TOC reduction were reached after 180min with the stoichiometric amount of H2O2. Long-term continuous experiments also confirm the beneficial effects of combining both technologies. TOC reduction above 85% was maintained within the first 100h on stream with an iron leaching close to 25% of the initial metal load. Longer times on stream led to a slow but continuously decrease of activity probably due to the blockage and/or loss of active sites.

ChemInform Abstract: Conversion of Saccharides into Formic Acid Using Hydrogen Peroxide and a Recyclable Palladium(II) Catalyst in Aqueous Alkaline Media at Ambient Temperatures.

AbstractA variety of mono‐ and disaccharides are efficiently converted into formic acid using a recyclable NHC‐amidate palladium(II) catalyst and stoichiometric amounts of H2O2 and NaOH.

Natural diatomites: Efficient green catalyst for Fenton-like oxidation of Orange II

The Fenton-like oxidation of the anionic azo-dye Orange II (100–500mg/L) was batchwise performed using commercial grade diatomites (3.5% Fe content) thermally treated.Solid samples were thoroughly characterized by several techniques. Peroxidation experiments were performed varying the diatomite calcination temperature (500, 700, 1000°C), reaction temperature (50, 60, 70, 80°C), catalyst load (0.47, 0.94, 1.89 and 3.78g), H2O2 concentration (11.0, 13.7, 20.6mmol/L) and dosing, pH (2–3.5) and initial dye concentration (0.28, 0.57, 1.43mmol/L). The influence of NaCl and oxalic acid on the catalytic performance and stability was also addressed.The best results were obtained with samples calcined at 700°C, with initial pH 3, at 70°C and using the stoichiometric amount of H2O2, since complete decoloration, TOC reduction close to 67% and negligible Fe leaching were achieved. The stability of the catalyst maintains after 20h of usage, with a final Fe loss of 2.25%. An average of 0.88mg/L of iron leached after each run, which is below the discharge limit.

Photo-Fenton oxidation of phenolic compounds catalyzed by iron-PILC

This work aimed to examine an iron pillared inter-layered clay as catalyst of the photo-Fenton process to oxidize phenolic compounds. The effect of the number of chlorine atoms substituted onto the ring was also studied. The selected clay was bentonite and the phenolic compounds were phenol, 4-chlorophenol and 2,4,6-tricholorophenol. The catalyst was synthesized by ionic exchange and characterized by X-ray diffraction, N2 physisorption, atomic absorption and X-ray photoelectron spectroscopy. In addition to the chlorine presence, the effect of other variables like initial concentration of H2O2 and catalyst loading was also evaluated. It was found that the highest 4-chlorophenol removal (94%) by degradation and mineralization is attained when using the stoichiometric amount of H2O2 and 0.8kg/m3 of catalyst. It outstands the fact that no pH adjustment was required at any moment in the experiment. Regarding the presence of chlorine in the pollutant structure, it was concluded that it significantly favors the degradation of the phenolic compound.

Ionic liquids breakdown by Fenton oxidation

Fenton oxidation has proved to be an efficient treatment for the degradation of ionic liquids (ILs) of different families viz. imidazolium, pyridinium, ammonium and phosphonium, in water. The intensification of the process, defined as the improvement on the efficiency of H2O2 consumption, by increasing the temperature is necessary to avoid high reaction times and the need of large excess of H2O2. In this work, temperatures within the range of 70–90°C have been used, which allowed an effective breakdown of the ILs tested (1gL−1 initial concentration) with the stoichiometric amount of H2O2 and a relatively low Fe3+ dose (50mgL−1). Under these conditions conversion of the ILs was achieved in less than 10min, with TOC reductions higher than 60% upon 4h reaction time, except for the phosphonium IL. The remaining TOC corresponded mainly to short-chain organic acids. The treatment reduced substantially the ecotoxicity up to final values below 0.01TU in most cases and a significant improvement of the biodegradability was achieved. Upon Fenton oxidation of the four ILs tested hydroxylated compounds of higher molecular weight than the starting ILs, fragments of ILs partially oxidized and short-chain organic acids were identified as reaction by-products. Reaction pathways are proposed.

Investigation of the reaction of [Cp*2M2O5] (M = Mo, W) with hydrogen peroxide and tert-butylhydroperoxide in MeCN; implications for olefin epoxidation catalyzed by organomolybdenum and organotungsten compounds

Compounds [Cp*2M2O5] (M = Mo, W) react with stoichiometric amounts of H2O2 (as a 30% w/w solution in water) and tBuOOH (TBHP, as a 70% w/w solution in decane) in MeCN solution to yield a variety of products as shown by the 1H NMR monitoring of the Cp* resonance. The reaction rate increases in the order W < Mo and TBHP < H2O2. While the total Cp* intensity remains constant when using stoichiometric amounts of oxidant, use of excess oxidant results in the ultimate total Cp* loss. From the decomposed solutions, crystals of [Cp*2Mo6O17] (1), (C5Me5O)[Cp*M6O18] (M = Mo, 2a; W, 2b), and (C5Me5O)2[Mo6O19] (3) were recovered and analyzed by X-ray diffraction. Catalytic cyclooctene epoxidation experiments with (nBu4N)2[M6O19] (M = Mo, W) in a 3:1 MeCN/toluene mixture at 55 °C using either aqueous H2O2 or TBHP/decane as oxidant revealed that these are not the active forms of the catalyst which is generated under the same conditions from [Cp*2M2O5], as reported in previous contributions from our group (Chem. Eur. J., 2010, 16, 9572–9584; Eur. J. Inorg. Chem., 2013, 2728–2735). Further catalytic studies using aged [Cp*2Mo2O5]/TBHP and [Cp*2W2O5]/H2O2 solutions show a small loss of activity (<50% in one week) attesting the robustness of the non-organometallic catalytically active species that is generated from the decomposition of [Cp*2M2O5]. These results cast doubts on the role of cyclopentadienyl as a supporting ligand for stable olefin epoxidation catalysts.

Decomposition of 1,1,1-trichloroethane in hot compressed water in anti-corrosive fused silica capillary reactor and Raman spectroscopic measurement of CO2 product

Decomposition of 1,1,1-trichloroethane (TCA) in hot compressed water, with or without an oxidizer, was studied using an optically transparent anti-corrosive fused silica capillary reactor (FSCR), and Raman spectroscopy. The phase behavior of TCA in water during hydrolysis/oxidation was observed continuously under a microscope and recorded with a digital-camera/recording system, A new phase behavior of TCA was found in the presence of excess H2O2; TCA was first gasified during heating, followed by liquefaction under increasing internal pressure as a result of the formation of O2 from the decomposition of H2O2, and subsequently gasified again during further heating up to 400°C. The gaseous products of TCA oxidation in hot compressed water were monitored quantitatively and qualitatively using Raman spectroscopy. The effects of the operating parameters, namely the stoichiometric amount of oxidizer, temperature, and reaction time, were investigated. In our experiments, it was found that 100% CO2 yield was achieved with a 175% stoichiometric amount of H2O2 at 420°C after 360s. Temperature plays a key role in the decomposition of TCA and the formation of CO2 in the supercritical water oxidation (SCWO) process. Based on our results, a reaction mechanism for TCA decomposition in hot compressed water was proposed. The global reaction kinetics showed that the formation of CO2 in the SCWO of TCA was a first-order reaction.

Deep Oxidative Desulfurization of Fuels Using Peroxophosphomolybdate Catalysts in Ionic Liquids

A combination of catalytic oxidation and extraction in ionic liquid (IL) was used for the removal of benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) from the model oil. Three peroxophosphomolybdates Q3{PO4[MoO(O2)2]4} (Q = [(C4H9)4N]+, [C14H29N(CH3)3]+ and [C16H33NC5H5]+) were synthesized and characterized. In the catalytic oxidation desulfurization (CODS) system containing the peroxophosphomolybdate with short alkyl chain ([(C4H9)4N]3{PO4[MoO(O2)2]4}) and H2O2, the process exhibited low sulfur removal (16.8%). However, with addition of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4), the extraction and catalytic oxidative desulfurization (ECODS) system remarkably increased the removal of sulfur to 97.3% (with stoichiometric amounts of H2O2). The process was superior to the simple extraction with IL (16.3%). The results demonstrated that the ECODS system could deeply remove DBT from the model oil, and this desulfurization system could be recycled 4 times...

Ferritin-catalyzed consumption of hydrogen peroxide by amine buffers causes the variable Fe2+ to O2 stoichiometry of iron deposition in horse spleen ferritin

Ferritin catalyzes the oxidation of Fe2+ by O2 to form a reconstituted Fe3+ oxy-hydroxide mineral core, but extensive studies have shown that the Fe2+ to O2 stoichiometry changes with experimental conditions. At Fe2+ to horse spleen ferritin (HoSF) ratios greater than 200, an upper limit of Fe2+ to O2 of 4 is typically measured, indicating O2 is reduced to 2H2O. In contrast, a lower limit of Fe2+ to O2 of approximately 2 is measured at low Fe2+ to HoSF ratios, implicating H2O2 as a product of Fe2+ deposition. Stoichiometric amounts of H2O2 have not been measured, and H2O2 is proposed to react with an unknown system component. Evidence is presented that identifies this component as amine buffers, including 3-N-morpholinopropanesulfonic acid (MOPS), which is widely used in ferritin studies. In the presence of non-amine buffers, the Fe2+ to O2 stoichiometry was approximately 4.0, but at high concentrations of amine buffers (0.10 M) the Fe2+ to O2 stoichiometry is approximately 2.5 for iron loadings of eight to 30 Fe2+ per HoSF. Decreasing the concentration of amine buffer to zero resulted in an Fe2+ to O2 stoichiometry of approximately 4. Direct evidence for amine buffer modification during Fe2+ deposition was obtained by comparing authentic and modified buffers using mass spectrometry, NMR, and thin layer chromatography. Tris(hydroxymethyl)aminomethane, MOPS, and N-methylmorpholine (a MOPS analog) were all rapidly chemically modified during Fe2+ deposition to form N-oxides. Under identical conditions no modification was detected when amine buffer, H2O2, and O2 were combined with Fe2+ or ferritin separately. Thus, a short-lived ferritin intermediate is required for buffer modification by H2O2. Variation of the Fe2+ to O2 stoichiometry versus the Fe2+ to HoSF ratio and the amine buffer concentration are consistent with buffer modification.