Treated domestic sewage: kinetics of Escherichia coli and total coliform inactivation by oxidation with hydrogen peroxide

Hydrogen peroxide has been used for decades in developed countries as an oxidizing agent in the treatment of water, domestic sewage and industrial effluents. This study evaluated the influence of the concentration of H2O2 and pH on the inactivation of Escherichia coli cells and the disinfection of sewage treated. The results showed that the inactivation rate increased with pH and H2O2. The presence of other contaminants dissolved in the effluent is probably the cause of these differences, because E. coli inactivation in synthetic wastewater was found to be much faster than in the real treated domestic sewage.

Preparation and immobilization of diNOsarcobalt(III) complex in zeolite y for the catalyzed production of hydrogen peroxide

A complex cation, diNOsarcobalt(III), [Co(diNOsar)]3+, (diNOsar = 1,8-dinitro-3,6,10,13,16,19-hexaazabicyclo-[6.6.6]eicosane), was synthesized and immobilized in the cavities of a Y zeolite by the reaction of precursor species in the pores of the zeolite. The encapsulated material was compared to the compound diNOsarcobalt(III) chloride, [Co(diNOsar)]Cl3. Both diNOsarcobalt(III) chloride and the zeolite-encapsulated complex, [Co(diNOsar)]3+/zeolite, were obtained in high yield and characterized by ultraviolet-visible and infrared spectroscopy. X-ray diffraction demonstrated the incorporation of the complex cation into the pores of the zeolite. The catalytic production of hydrogen peroxide from oxygenated water confirmed the successful synthesis of the complex diNOsarcobalt(III) immobilized in the zeolite.

A simple spectrophotometric method for the determination of methyldopa using p-chloranil in the presence of hydrogen peroxide

A simple, rapid and sensitive spectrophotometric method has been developed for the determination of methyldopa in pharmaceutical formulations. The method is based on the reaction between tetrachloro-p-benzoquinone (p-chloranil) and methyldopa, accelerated by hydrogen peroxide (H2O2), producing a violet-red compound (λmax = 535 nm) at ambient temperature (25.0 ± 0.2 ºC). Experimental design methodologies were used to optimize the measurement conditions. Beer's law is obeyed in a concentration range from 2.10 x 10-4 to 2.48 x 10-3 mol L-1 (r = 0.9997). The limit of detection was 7.55 x 10-6 mol L-1 and the limit of quantification was 2.52 x 10-5 mol L-1. The intraday precision and interday precision were studied for 10 replicate analyses of 1.59 x 10-3 mol L-1 methyldopa solution and the respective coefficients of variation were 0.7 and 1.1 %. The proposed method was successfully applied to the determination of methyldopa in commercial brands of pharmaceuticals. No interferences were observed from the common excipients in the formulations. The results obtained by the proposed method were favorably compared with those given by the Brazilian Pharmacopoeia procedure at 95 % confidence level.

Simulation of hydrogen peroxide direct synthesis in a microreactor

A set of models in Aspen plus was built to simulate the direct synthesis process of hydrogen peroxide in a micro-reactor system. This process model can be used to carry out material balance calculation under various experimental conditions. Three thermodynamic property methods were compared by calculating gas solubility and Uniquac-RK method was finally selected for process model. Two different operation modes with corresponding operation conditions were proposed as the starting point of future experiments. Simulations for these two modes were carried out to get the information of material streams. Moreover, some hydrodynamic parameters such as gas/liquid superficial velocity, gas holdup were also calculated with improved process model. These parameters proved the proposed experimental conditions reasonable to some extent. The influence of operation conditions including temperature, pressure and circulation ratio was analyzed for the first operation mode, where pure oxygen was fed into dissolving tank and hydrogen-carbon dioxide mixture was fed into microreactor directly. The preferred operation conditions for the system are low temperature (2°C) and high pressure (30 bar) in dissolving tank. High circulation ratio might be good in the sense that more oxygen could be dissolved and fed into reactor for reactions, but meanwhile hydrodynamics of microreactor should be considered. Furthermore, more operation conditions of reactor gas/liquid feeds in both of two operation modes were proposed to provide guidance for future experiment design and corresponding hydrodynamic parameters were also calculated. Finally, safety issue was considered from thermodynamic point of view and there is no explosion danger at given experimental plan since the released reaction heat will not cause solvent vaporization inside the microchannels. The improvement of process model still needs further study based on the future experimental results.

Development of an environmentally friendly method of starch oxidation by hydrogen peroxide and a complex water-soluble Iron catalyst

Oxidized starch is a key component in the paper industry, where it is used as both surfacing sizer and filler. Large quantities are annually used for this purpose; however, the methods for the oxidation are not environmentally friendly. In our research, we have studied the possibility to replace the harmful oxidation agents, such as hypochlorite or iodates and transition metal catalysts, with a more environmentally friendly oxidant, hydrogen peroxide (H2O2), and a special metal complex catalyst (FePcS), of which only a small amount is needed. The work comprised batch and semi-batch studies by H2O2, ultrasound studies of starch particles, determination of low-molecular by-products and determination of the decomposition kinetics of H2O2 in the presence of starch and the catalyst. This resulted in a waste-free oxidation method, which only produces water and oxygen as side products. The starch oxidation was studied in both semi-batch and batch modes in respective to the oxidant (H2O2) addition. The semi-batch mode proved to yield a sufficient degree of substitution (COOH groups) for industrial purposes. Treatment of starch granules by ultrasound was found to improve the reactivity of starch. The kinetic results were found out to have a rather complex pattern – several oxidation phases were observed, apparently due to the fact that the oxidation reaction in the beginning only took place on the surface, whereas after a prolonged reaction time, partial degradation of the solid starch granules allowed further reaction in the interior parts. Batch-mode experiments enabled a more detailed study of the mechanisms of starch in the presence of H2O2 and the catalyst, but yielded less oxidized starch due to rapid decomposition of H2O2 due to its high concentrations. The effect of the solid-liquid (S/L) ratio in the reaction system was studied in batch experiments. These studies revealed that the presence of the catalyst and the starch enhance the H2O2 decomposition.

Combination of catalyst development and chemical reaction engineering : a key aspect to improve the hydrogen peroxide direct synthesis

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Safety study of hydrogen peroxide direct synthesis

Kandidaatintyön johdantokappaleessa esitellään vetyperoksidi ja mihin sitä käytetään teollisuudessa. Työssä vertaillaan antrakinoniprosessia ja suoraa prosessia sekä selvitetään nykyisin enemmän vetyperoksidituotantoon käytetyn antrakinoniprosessin ongelmakohdat ja osoitetaan, miksi suora synteesi vetyperoksidin tuotannossa olisi parempi vaihtoehto. Kandidaatintyön käsittelee suurilta osin turvallisuusongelmia, joita esiintyy suoran synteesin yhteydessä. Kirjallisuudesta on etsitty ratkaisuja näihin ongelmiin, kuten membraaniprosessin käyttöä räjähdysvaaran välttämiseksi. Pienemmän reaktorin eli ns. mikroreaktorin käyttö tuo mukanaan monia etuja vetyperoksidin tuotantoon. Tällöin prosessi on turvallisempi ja sitä on helpompi hallita. Mikroreaktorissa voidaan käyttää korkeampia lämpötiloja ja paineita kuin makroreaktorilla ilman, että räjähdysvaara prosessissa kasvaisi. Mikroreaktorin sisällä olevat mikrokanavat luovat turvallisen ympäristön synteesille. Aspen plus – simulointiohjelmalla mallinnettiin ja simulointiin suoran prosessin kriittisiä virtoja mikroreaktorissa. Tarkoituksena oli löytää virrat, joissa kulkee mahdollisesti räjähtävä kaasuseos. Kaasumaiset prosessivirrat ovat kriittisimmät vetyperoksidin suorassa synteesissä, koska ne aiheuttavat todennäköisemmin räjähdyksen kuin nestemäiset prosessivirrat. Kaikkein eniten prosessiturvallisuutta uhkaavat ainevirrat ennen ja jälkeen mikroreaktoria.

Development of a process for the direct synthesis of hydrogen peroxide in a novel microstructured reactor

Microreactors have proven to be versatile tools for process intensification. Over recent decades, they have increasingly been used for product and process development in chemical industries. Enhanced heat and mass transfer in the reactors due to the extremely high surfacearea- to-volume ratio and interfacial area allow chemical processes to be operated at extreme conditions. Safety is improved by the small holdup volume of the reactors and effective control of pressure and temperature. Hydrogen peroxide is a powerful green oxidant that is used in a wide range of industries. Reduction and auto-oxidation of anthraquinones is currently the main process for hydrogen peroxide production. Direct synthesis is a green alternative and has potential for on-site production. However, there are two limitations: safety concerns because of the explosive gas mixture produced and low selectivity of the process. The aim of this thesis was to develop a process for direct synthesis of hydrogen peroxide utilizing microreactor technology. Experimental and numerical approaches were applied for development of the microreactor. Development of a novel microreactor was commenced by studying the hydrodynamics and mass transfer in prototype microreactor plates. The prototypes were designed and fabricated with the assistance of CFD modeling to optimize the shape and size of the microstructure. Empirical correlations for the mass transfer coefficient were derived. The pressure drop in micro T-mixers was investigated experimentally and numerically. Correlations describing the friction factor for different flow regimes were developed and predicted values were in good agreement with experimental results. Experimental studies were conducted to develop a highly active and selective catalyst with a proper form for the microreactor. Pd catalysts supported on activated carbon cloths were prepared by different treatments during the catalyst preparation. A variety of characterization methods were used for catalyst investigation. The surface chemistry of the support and the oxidation state of the metallic phase in the catalyst play important roles in catalyst activity and selectivity for the direct synthesis. The direct synthesis of hydrogen peroxide was investigated in a bench-scale continuous process using the novel microreactor developed. The microreactor was fabricated based on the hydrodynamic and mass transfer studies and provided a high interfacial area and high mass transfer coefficient. The catalysts were prepared under optimum treatment conditions. The direct synthesis was conducted at various conditions. The thesis represents a step towards a commercially viable direct synthesis. The focus is on the two main challenges: mitigating the safety problem by utilization of microprocess technology and improving the selectivity by catalyst development.

Effect of trolox C on cardiac contracture induced by hydrogen peroxide

Hydrogen peroxide (H2O2) perfused into the aorta of the isolated rat heart induces a positive inotropic effect, with cardiac arrhythmia such as extrasystolic potentiation or cardiac contractures, depending on the dose. The last effect is similar to the "stone heart" observed in reperfusion injury and may be ascribed to lipoperoxidation (LPO) of the membrane lipids, to protein damage, to reduction of the ATP level, to enzymatic alterations and to cardioactive compounds liberated by LPO. These effects may result in calcium overload of the cardiac fibers and contracture ("stone heart"). Hearts from male Wistar rats (300-350 g) were perfused at 31oC with Tyrode, 0.2 mM trolox C, 256 mM H2O2 or trolox C + H2O2. Cardiac contractures (baseline elevation of the myograms obtained) were observed when hearts were perfused with H2O2 (Tyrode: 5.9 ± 3.2; H2O2: 60.5 ± 13.9% of the initial value); perfusion with H2O2 increased the LPO of rat heart homogenates measured by chemiluminescence (Tyrode: 3,199 ± 259; H2O2: 5,304 ± 133 cps mg protein-1 60 min-1), oxygen uptake (Tyrode: 0.44 ± 0.1; H2O2: 3.2 ± 0.8 nmol min-1 mg protein-1) and malonaldehyde (TBARS) formation (Tyrode: 0.12 ± 0; H2O2: 0.37 ± 0.1 nmol/ml). Previous perfusion with 0.2 mM trolox C reduced the LPO (chemiluminescence: 4,098 ± 531), oxygen uptake (0.51 ± 0) and TBARS (0.13 ± 0) but did not prevent the H2O2-induced contractures (33.3 ± 16%). ATP (Tyrode: 2.84 ± 0; H2O2: 0.57 ± 0) and glycogen levels (Tyrode: 0.46 ± 0; H2O2: 0.26 ± 0) were reduced by H2O2. Trolox did not prevent these effects (ATP: 0.84 ± 0 and glycogen: 0.27 ± 0). Trolox C is known to be more effective than a -tocopherol or g -tocopherol in reducing LPO though it lacks the phytol portion of vitamin E to be fixed to the cell membranes. Trolox C, unlike vitamin A, did not prevent the glycogen reduction induced by H2O2. Trolox C induced a positive chronotropic effect that resulted in higher energy consumption. The reduction of energy level seemed to be more important than LPO in the mechanism of H2O2-induced contracture

Catalytic direct synthesis of hydrogen peroxide in a novel microstructured reactor

The direct synthesis from hydrogen and oxygen is a green alternative for production of hydrogen peroxide. However, this process suffers from two challenges. Firstly, mixtures of hydrogen and oxygen are explosive over a wide range of concentrations (4-94% H2 in O2). Secondly, the catalytic reaction of hydrogen and oxygen involves several reaction pathways, many of them resulting in water production and therfore decreasing selectivity. The present work deals with these two challenges. The safety problem was dealed by employing a novel microstructured reactor. Selectivity of the reaction was highly improved by development a set of new catalysts. The final goal was to develop an effective and safe continuous process for direct synthesis of hydrogen peroxide from H2 and O2. Activated carbon cloth and Sibunit were examined as the catalysts’ supports. Palladium and gold monometallic and palladium-gold bimetallic catalysts were thoroughly investigated by numerous kinetic experiments performed in a tailored batch reactor and several catalyst charachterization methods. A complete set of data for direct synthesis of H2O2 and its catalytic decomposition and hydrogenation was obtained. These data were used to assess factors influencing selectivity and activity of the catalysts in direct synthesis of H2O2 as well as its decomposition and hydrogenation. A novel microstructured reactor was developed based on hydrodynamics and mass transfer studies in prototype microstractural plates. The shape and the size of the structural elements in the microreactor plate were optimized in a way to get high gas-liquid interfacial area and gas-liquid mass transfer. Finally, empirical correlations for the volumetric mass transfer coefficient were derived. A bench-scale continuous process was developed by using the novel microstructral plate reactor. A series of kinetic experiments were performed to investigate the effects of the gas and the liquid feed rates and their ratio, the amount of the catalyst, the gas feed composition and pressure on the final rate of H2O2 production and selectivity.

Concentration of hydrogen peroxide and improving its energy efficiency

Distillation is a unit operation of process industry, which is used to separate a liquid mixture into two or more products and to concentrate liquid mixtures. A drawback of the distillation is its high energy consumption. An increase in energy and raw material prices has led to seeking ways to improve the energy efficiency of distillation. In this Master's Thesis, these ways are studied in connection with the concentration of hydrogen peroxide at the Solvay Voikkaa Plant. The aim of this thesis is to improve the energy efficiency of the concentration of the Voikkaa Plant. The work includes a review of hydrogen peroxide and its manufacturing. In addition, the fundamentals of distillation and its energy efficiency are reviewed. An energy analysis of the concentration unit of Solvay Voikkaa Plant is presented in the process development study part. It consists of the current and past information of energy and utility consumptions, balances, and costs. After that, the potential ways to improve the energy efficiency of the distillation unit at the factory are considered and their feasibility is evaluated technically and economically. Finally, proposals to improve the energy efficiency are suggested. Advanced process control, heat integration and energy efficient equipment are the most potential ways to carry out the energy efficient improvements of the concentration at the Solvay Voikkaa factory. Optimization of the reflux flow and the temperatures of the overhead condensers can offer immediate savings in the energy and utility costs without investments. Replacing the steam ejector system with a vacuum pump would result in savings of tens of thousands of euros per year. The heat pump solutions, such as utilizing a mechanical vapor recompression or thermal vapor recompression, are not feasible due to the high investment costs and long pay back times.

Reaction of diphenyl diselenide with hydrogen peroxide and inhibition of delta-aminolevulinate dehydratase from rat liver and cucumber leaves

The interaction of the product of H2O2 and (PhSe)2 with delta-aminolevulinate dehydratase (delta-ALA-D) from mammals and plants was investigated. (PhSe)2 inhibited rat hepatic delta-ALA-D with an IC50 of 10 µM but not the enzyme from cucumber leaves. The reaction of (PhSe)2 with H2O2 for 1 h increased the inhibitory potency of the original compound and the IC50 for animal delta-ALA-D inhibition was decreased from 10 to 2 µM. delta-ALA-D from cucumber leaves was also inhibited by the products of reaction of (PhSe)2 with H2O2 with an IC50 of 4 µM. The major product of reaction of (PhSe)2 with H2O2 was identified as seleninic acid and produced an intermediate with a lambdamax at 265 nm after reaction with t-BuSH. These results suggest that the interaction of (PhSe)2 with mammal delta-ALA-D requires the presence of cysteinyl residues in close proximity. Two cysteine residues in spatial proximity have been recently described for the mammalian enzyme. Analysis of the primary structure of plant delta-ALA-D did not reveal an analogous site. In contrast to (PhSe)2, seleninic acid, as a result of the higher electrophilic nature of its selenium atom, may react with additional cysteinyl residue(s) in mammalian delta-ALA-D and also with cysteinyl residues from cucumber leaves located at a site distinct from that found at the B and A sites in mammals. Although the interaction of organochalcogens with H2O2 may have some antioxidant properties, the formation of seleninic acid as a product of this reaction may increase the toxicity of organic chalcogens such as (PhSe)2.

Cytotoxicity of chlorhexidine digluconate to murine macrophages and its effect on hydrogen peroxide and nitric oxide induction

Chlorhexidine, even at low concentrations, is toxic for a variety of eukaryotic cells; however, its effects on host immune cells are not well known. We evaluated in vitro chlorhexidine-induced cytotoxicity and its effects on reactive oxygen/nitrogen intermediate induction by murine peritoneal macrophages. Thioglycollate-induced cells were obtained from Swiss mice by peritoneal lavage with 5 ml of 10 mM phosphate-buffered saline, washed twice and resuspended (10(6) cells/ml) in appropriate medium for each test. Cell preparations contained more than 95% macrophages. The cytotoxicity was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay and the presence of hydrogen peroxide (H2O2) and nitric oxide (NO) by the horseradish peroxidase-dependent oxidation of phenol red and Griess reaction, respectively. The midpoint cytotoxicity values for 1- and 24-h exposures were 61.12 ± 2.46 and 21.22 ± 2.44 µg/ml, respectively. Chlorhexidine did not induce synthesis or liberation of reactive oxygen/nitrogen intermediates. When macrophages were treated with various sub-toxic doses for 1 h (1, 5, 10, and 20 µg/ml) and 24 h (0.5, 1, and 5 µg/ml) and stimulated with 200 nM phorbol myristate acetate (PMA) solution, the H2O2 production was not altered; however, the NO production induced by 10 µg/ml lipopolysaccharide (LPS) solution varied from 14.47 ± 1.46 to 22.35 ± 1.94 µmol/l and 13.50 ± 1.42 to 20.44 ± 1.40 µmol/l (N = 5). The results showed that chlorhexidine has no immunostimulating activity and sub-toxic concentrations did not affect the response of macrophages to the soluble stimulus PMA but can interfere with the receptor-dependent stimulus LPS.

Antioxidant responses of Laeonereis acuta (Polychaeta) after exposure to hydrogen peroxide

The effects of H2O2 were evaluated in the estuarine worm Laeonereis acuta (Polychaeta, Nereididae) collected at the Patos Lagoon estuary (Southern Brazil) and maintained in the laboratory under controlled salinity (10 psu diluted seawater) and temperature (20°C). The worms were exposed to H2O2 (10 and 50 µM) for 4, 7, and 10 days and the following variables were determined: oxygen consumption, catalase (CAT) and glutathione peroxidase activity in both the supernatant and pellet fractions of whole body homogenates. The concentrations of non-protein sulfhydryl and lipid peroxides (LPO) were also measured. The oxygen consumption response was biphasic, decreasing after 4 days and increasing after 7 and 10 days of exposure to 50 µM H2O2 (P < 0.05). At the same H2O2 concentration, CAT activity was lower (P < 0.05) in the pellet fraction of worms exposed for 10 days compared to control. Non-protein sulfhydryl concentration and glutathione peroxidase activity were not affected by H2O2 exposure. After 10 days, LPO levels were higher (P < 0.05) in worms exposed to 50 µM H2O2 compared to control. The reduction in the antioxidant defense was paralleled by oxidative stress as indicated by higher LPO values (441% compared to control). The reduction of CAT activity in the pellet fraction may be related to protein oxidation. These results, taken together with previous findings, suggest that the worms were not able to cope with this H2O2 concentration.

Hydrogen peroxide induces a specific DNA base change profile in the presence of the iron chelator 2,2’ dipyridyl in Escherichia coli

Pretreatment of Escherichia coli cultures with the iron chelator 2,2’-dipyridyl (1 mM) protects against the lethal effects of low concentrations of hydrogen peroxide (<15 mM). However, at H2O2 concentrations equal to or greater than 15 mM, dipyridyl pretreatment increases lethality and mutagenesis, which is attributed to the formation of different types of DNA lesions. We show here that pretreatment with dipyridyl (1 mM) prior to challenge with high H2O2 concentrations (≥15 mM) induced mainly G:C→A:T transitions (more than 100X with 15 mM and more than 250X with 20 mM over the spontaneous mutagenesis rate) in E. coli. In contrast, high H2O2 concentrations in the absence of dipyridyl preferentially induced A:T→T:A transversions (more than 1800X and more than 300X over spontaneous mutagenesis for 15 and 20 mM, respectively). We also show that in the fpg nth double mutant, the rpoB gene mutation (RifS-RifR) induced by 20 mM H2O2 alone (20X higher) was increased in 20 mM H2O2 and dipyridyl-treated cultures (110X higher), suggesting additional and/or different lesions in cells treated with H2O2 under iron deprivation. It is suggested that, upon iron deprivation, cytosine may be the main damaged base and the origin of the pre-mutagenic lesions induced by H2O2.