Destruction Of Organic Compounds Research Articles

Rapid degradation of methylene blue in a novel heterogeneous Fe3O4 @rGO@TiO2-catalyzed photo-Fenton system.

Herein, a ternary nanocomposite with TiO2 nanoparticles anchored on reduced graphene oxide (rGO)-encapsulated Fe3O4 spheres (Fe3O4@rGO@TiO2) is presented as a high efficient heterogeneous catalyst for photo-Fenton degradation of recalcitrant pollutants under neutral pH. Fe3O4@rGO@TiO2 was synthesized by depositing TiO2 nanoparticles on the surface of the Fe3O4 spheres wrapped by graphene oxide (GO) which was obtained by an electrostatic layer-by-layer method. This as-prepared catalyst reflected good ferromagnetism and superior stability which makes it convenient to be separated and recycled. Due to the synergic effects between the different components composed the catalyst, swift reduction of Fe3+ can be achieved to regenerate Fe2+. Fe3O4@rGO@TiO2 exhibited enhancing catalytic activity for the degradation of azo-dyes compared with Fe3O4, Fe3O4@SiO2@TiO2 or SiO2@rGO@TiO2, further conforming the rapid redox reaction between Fe2+ and Fe3+. All these merits indicate that the composite catalyst possesses great potential for visible-light driven destruction of organic compounds.

Volatile organic compounds destruction by catalytic oxidation for environmental applications.

Volatile organic compounds destruction by catalytic oxidation for environmental applications.

Destruction of organic Cl and Br compounds through incineration enhanced by alkali and alumina addition

Thermochemical destruction of organic Cl and Br compounds in a combustion system was studied. A Cl compound and three Br compounds, namely, 1,2,3,4-tetrachlorobenzene (TeCB), 1,2,4,5-tetrabromobenzene (TeBB), tetrabromobisphenol A (TBBPA), and decabromodiphenyl ether (DBDE) were used. The samples on a boat were combusted at 600 °C followed by gas combustion at 800, 900, and 1,100 °C. An off-gas was adsorptively collected and introduced into a Cl and Br detector by thermal desorption. The destruction efficiency was evaluated using the organic halogen residual ratio (OX-RR) (μg g−1). Halogenated benzene compounds such as TeCB and TeBB were destructed moderately (OX-RR for these compounds at 800, 900 and 1,100 °C was 112, 35 and 32 μg g−1 and 258, 57 and 48 μg g−1, respectively); on the other hand, the destruction of TBBPA and DBDE, namely fire retardants, was difficult (OX-RR at 800 °C for these compounds was 7,159 and 718 μg g−1, respectively). Addition of an alkali and an alumina to a sample enhanced the destruction of organic compounds drastically by several times. This destruction enhancement occurred at temperature as low as 600 °C. Such chemical halogen control is effective to thermal destruction of organic Cl and Br compounds.

Research into acetone removal from air by biofiltration using a biofilter with straight structure plates

The biological air treatment method is based on the biological destruction of organic compounds using certain cultures of microorganisms. This method is simple and may be applied in many branches of industry. The main element of biological air treatment devices is a filter charge. Tests were carried out using a new-generation laboratory air purifier with a plate structure. This purifier is called biofilter. The biofilter has a special system for packing material humidification which does not require additional energy inputs. In order to extend the packing material's durability, it was composed of thermally treated birch fibre. Pollutant (acetone) biodegradation occurred on thermally treated wood fibre in this research. According to the performed tests and the received results, the process of biodestruction was highly efficient. When acetone was passed through biofilter's packing material at 0.08 m s−1 rate, the efficiency of the biofiltration process was from 70% up to 90%. The species of bacteria capable of removing acetone vapour from the air, i.e. Bacillus (B. cereus, B. subtilis), Pseudomonas (P. aeruginosa, P. putida), Stapylococcus (S. aureus) and Rhodococcus sp., was identified in this study during the process of biofiltration. Their amount in the biological packing material changed from 1.6 × 107 to 3.7 × 1011 CFU g−1.

Modeling of the thermal influence of fires on the physicochemical properties and microbial activity of litter in cryogenic soils

Periodic surface fires in the cryolithozone (the northern taiga subzone) are the main factor determining the qualitative and quantitative characteristics of the soil organic matter. The specific features of the changes in the physicochemical parameters and microbial activity of the organic horizons in the cryogenic soils under larch forests of the northern taiga after the impact of high temperatures were revealed. The temperatures of fires of different intensity were simulated in laboratory conditions. The thermal impact on the litter organic matter during the surface fires may increase the CO2 emission from the surface of the soil in the postfire communities due to the destruction of organic compounds only for a short time. After fires of high intensity with strong mineralization of the litters, during a period of more than 1 month, the pyrogenic effect on the organic horizons of the soils under the larch forests of the cryolithozone determined the reduction of the CO2 emissions in the freshly burned areas as compared to the intact stands.

Studying nitrogen influence on efficiency of vibrocavitation treatment of dairy factory wastewater

Creating highly efficient methods of wastewater decontamination and destruction of present organic compounds is one of the promising trends for solving problems in technology of water treatment. The technology for wastewater treatment of organic and biological contaminants, based on the cavitation water treatment is proposed in the paper. Theoretical knowledge and experimental researches in the field of cavitation has given ground to a method of vibro-resonance cavitation processing of liquids, which specific feature is organic combination of high-intensity of the formed cavitation field with significant treatment capacity. For its implementation, a low vibration electromagnetic resonance cavitator, which is of a simple structural design, energy saving and convenient in operation and maintenance was developed. The studies of vibrocavitation treatment efficiency, carried out on the dairy factory wastewater in the presence of nitrogen, indicate synergism of vibrocavitation action in the presence of gas that is confirmed by the calculated values of effective rate constants of microbial decontamination and destruction of organic compounds. The obtained results show high efficiency of wastewater treatment, conditioned by shock-dynamic, cavitation effects of sterilization and side phenomena of physical and electromagnetic nature, enhancing its effectiveness. Such integrated approach provides greater efficiency of the process on the whole process and opens the prospect of practical application in technologies of wastewater treatment at food enterprises.

Temperature sensitivity of organic compound destruction in SCWO process

To study the temperature sensitivity of the destruction of organic compounds in supercritical water oxidation process (SCWO), oxidation effects of twelve chemicals in supercritical water were investigated. The SCWO reaction rates of different compounds improved to varying degrees with the increase of temperature, so the highest slope of the temperature-effect curve (imax) was defined as the maximum ratio of removal ratio to working temperature. It is an important index to stand for the temperature sensitivity effect in SCWO. It was proven that the higher imax is, the more significant the effect of temperature on the SCWO effect is. Since the high-temperature area of SCWO equipment is subject to considerable damage from fatigue, the temperature is of great significance in SCWO equipment operation. Generally, most compounds (imax > 0.25) can be completely oxidized when the reactor temperature reaches 500°C. However, some compounds (imax > 0.25) need a higher temperature for complete oxidation, up to 560°C. To analyze the correlation coefficients between imax and various molecular descriptors, a quantum chemical method was used in this study. The structures of the twelve organic compounds were optimized by the Density Functional Theory B3LYP/6-311G method, as well as their quantum properties. It was shown that six molecular descriptors were negatively correlated to imax while other three descriptors were positively correlated to imax. Among them, dipole moment had the greatest effect on the oxidation thermodynamics of the twelve organic compounds. Once a correlation between molecular descriptors and imax is established, SCWO can be run at an appropriate temperature according to molecular structure.

Photo Catalytic Degradation of Effluent of Iron and Power Plant Industries in Aqueous Solution by CDS Nano Catalyst Using UV Irradiation

The iron and power plant industries consume significant amount of water during the power generation and finishing operations. In this operation a used water having high chemical oxygen demand contents and the waste water discharged in rivers or public sewage treatment plant. Their treatment has been a necessary aspect for human prosperity and ecological environment. This paper shows the detailed study of photo catalytic degradation of effluent carried out in the presence of an aqueous solution of TiO2 nano catalyst irradiated with UV light in a batch reactor. It was observe that photo catalytic degradation of effluent obey pseudo first order kinetics according to langum-uir Hinshelwood model. The influences of various factors in rate of reaction are, initial effluent concentration, catalyst concentration and UV light irradiation time on degradation efficiency were scientifically studied. The degradation of eluent was determined by Photo colorimeter and determines the COD degradation through transmittance of effluent. Keywords - Photo catalytic degradation, TiO2 nano catalyst, COD, AOP's, Iron and power plant waste water. I. INTRODUCTION Environmental pollution is produced either by a natural source or by some anthropogenic activity, or by human. Which has an adverse effect on humans, animals, plants and materials? The inordinate population growth, fast industrialization, rapid urbanization and modified agricultural operations have intensified the pollution of air and water both and as a consequence, the human health is seriously affected by this environmental and ecological disorder. If this situation is not controlled timely, it would become a malignant problem for the survival of mankind on this planet. Environment pollution by organic pollutant also sets several ecological problems, which is increased by the fact that most of them are difficult to degrade using standard biological methods. For the removal of such recalcitrant pollutants some traditional, physical techniques such as adsorption on activated charcoal, ultra filtration, reverse osmosis and coagulation is used efficiently. Nevertheless they are nondestructive. Recently there has been considerable interest on the utilization of advanced oxidation process (AOPs) for the destruction of organic compounds in contaminated water. The key advantage of this degradation method is that it can be carried out under ambient condition and lead to complete degradation of organic compounds. Among the advanced oxidation process heterogeneous photo catalysis appears as an emerging technology leading to the total mineralization of most of the organic pollutants. If a suitable semiconductors are irradiated with visible or UV light electron excitation from Valance band to conduction band results and a vacancy or hole is left in the valance band such have the effect of a positive charge. Thus in turn generates the formation of holes on the surface of the semiconductor, which can react with oxygen, water and hydroxide ion to form hydroxyl radicals. Furthermore, super oxide radicals are formed from the reaction of excited electrons with oxygen molecules. The highly reactive oxygen species so formed react with the organic pollutants resulting in their oxidation. The kinetics of photo catalytic degradation of many organic compounds in TiO2 suspensions under visible irradiation has often been matched to the simple langmuir-hinshelwood equation -1 r = -dc/d t ……equation-1

Comparison of various organic compounds destruction on rare earths doped Ti/Sb-SnO2 electrodes

Ti/Sb-SnO2 and three kinds of rare earths (REs), namely Ce, Gd, and Eu doped Ti/Sb-SnO2 electrodes were prepared and tested for their capacity on electrocatalytic degradation of three kinds of basal aromatic compounds (benzoquinone, hydroquinone and catechol) and six kinds of aliphatic acids (maleic acid, fumaric acid, succinic acid, malonic acid, oxalic acid and acetic acid). The elimination of selected organics as well as their TOC removal with different doped Ti/Sb-SnO2 electrodes was described by first-order kinetics. Compared with Ti/Sb-SnO2, the Gd and Eu doped electrodes show better performance on the degradation of most of the selected organics, while Ce doped electrode shows either closely or lower efficiency on the degradation of these selected organics. Besides electrode material, the molecular structure of organic compound has obvious effect on its degradation in the electrocatalytic process. Catechol is more resistant to the electrophilic attack by hydroxyl radicals than benzoquinone and hydroquinone. The compound with more complicate molecular structure or longer carbon chain is more difficult to be mineralized. The aliphatic acid with higher oxygen content or more double bonds is more readily to be oxidized in the electrocatalytic process.

Doped manganese (IV) oxide in processes of destruction and removal of organic compounds from aqueous solutions

Possible use of the doped manganese (IV) oxide electrodeposited from fluoride electrolytes in the processes of anodic oxidation and destruction of organic compounds in aqueous solutions has been analyzed. The phase composition of the specified oxide was investigated depending on the nature of cation dopant entering into the electrolyte composition. The use of the Fe2+-doped manganese (IV) oxide as an anodic material for the phenol destruction and also the use of manganese (IV) oxide doped with ammonium oxide ions for the removal of the water-soluble form of hydrocarbons during the emergency blowout of oil and oil products were studied

Computer Simulation of Decomposition Mechanisms for CL‐20, Hydrazine, and Their Binary System

AbstractAn approach to simulate thermal destruction processes of energetic materials has been developed. It is based on the classification of structural features for nitro compounds and the experimental data regarding their decomposition mechanisms. This approach consists of the mathematical simulation of thermal decomposition mechanisms to predict the likely reactions that may occur during the destruction of organic compounds. On the basis of contemporary experimental data on the decomposition of energetic materials from various chemical classes, a set of semi‐empirical rules for modeling possible reaction pathways has been formulated. These rules allow the generation of a whole set of possible decomposition mechanisms for substances at different steps of their destruction. In this study, the suggested methodology is applied to 2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (CL‐20) and hydrazine and to their binary energetic mixture. It has been shown that thermal decomposition of the binary system consists in decompositions of the separate compounds at the initial stage with subsequent collisions and interactions of the resultant intermediates and decomposition products at different stages. In addition to some experimentally found decomposition products, our simulation showed some other possible compounds among the final products.

Supercritical Water Technology Applied to the Purification of Waters Contaminated by Toxic Micro-Polluting Organic Compounds

Purification of water contaminated by toxic organic compounds at low and very low concentration is a quite interesting challenge from both the technical and the economical point of view. In fact, the direct destruction of organic compounds dissolved in very diluted aqueous solution is very costly and hardly achievable. To overcome this problems it was studied and developed a new water purification process which is made of three steps: a) removal of the diluted and toxic polluting compounds by adsorption on activated carbon beds operating at ambient P ant T; b) regeneration of the exhausted carbon bed with supercritical water in order to obtain a mixture of water and polluting compounds signifi-cantly more concentrated than the contaminated liquid water; c) destruction of the toxic compounds in a continuous Supercritical Water Oxidation Reactor. Step a) was studied at laboratory scale in order to obtain all the required information for modeling the adsorption operation; step b) was modeled by using literature experimental data and, step c) was validated at pilot plant scale. In all the above mentioned steps, phenol was used as representative of polluting compounds.

Organic and total mercury determination in sediments by cold vapor atomic absorption spectrometry: methodology validation and uncertainty measurements

The purpose of the present study was to validate a method for organic Hg determination in sediment. The procedure for organic Hg was adapted from literature, where the organomercurial compounds were extracted with dichloromethane in acid medium and subsequent destruction of organic compounds by bromine chloride. Total Hg was performed according to 3051A USEPA methodology. Mercury quantification for both methodologies was then performed by CVAAS. Methodology validation was verified by analyzing certified reference materials for total Hg and methylmercury. The uncertainties for both methodologies were calculated. The quantification limit of 3.3 µg kg -1 was found for organic Hg by CVAAS.

Electro-oxidative process for the mineralization of solvent and recovery of plutonium from organic wastes

Mediated electrochemical oxidation is a promising technique for the destruction of organic compounds. Destruction of tributyl phosphate (TBP) in normal paraffin hydrocarbon (NPH) in nitric acid medium containing electro-generated Ag(II) was studied. Initially, the effect of uranium, presence of DBP along with uranium in the organic phase and direct electrochemical oxidation without catalyst (Ag) on the destruction of 30% TBP/NPH system was evaluated. For a comparison, the rate of destruction of NPH alone was studied. Further, radioactive laboratory waste solution was tested for the destruction of organic waste under similar experimental conditions. The electrolyte used in the system was 0.5 M AgNO3 in 8 M HNO3 at 333 K. The uniqueness in all these experiments is the use of a double end open porcelain diaphragm for the isolation of electrodes. Though there would be a slight reduction in the efficiency, two major hurdles viz., reduction in the concentration of nitric acid and reduction in the volume of catholyte resulting in an increase in cell voltage were avoided. The problem of the migration of Ag+/Ag2+ and accumulating at the cathode site was overcome by using double end open diaphragm and thorough mixing. The results revealed that the rate of destruction of organics is favoured in the presence of uranium in organic phase and with increase in temperature.

Chlorophene degradation by combined ultraviolet irradiation and ozonation

Ozonation combined with UV irradiation (UV/O3) is an advanced oxidation technique that is very promising for the destruction of organic compounds in aqueous solution. In this study, chlorophene was chosen as a model substrate to investigate the effects of pH, initial substrate concentration, ozone dose, and UV light intensity in degradation experiments. The pseudo–first-order rate constant for total organic carbon (TOC) removal was 2.4 × 10−2, 9.8 × 10−4, and 6.4 × 10−2 min−1 for O3, UV, and UV/O3 treatment, respectively. Clearly, UV-enhanced ozonation leads to a synergetic increase in the overall degradation efficiency. Comparative experiments were performed to investigate the effect of the matrix (distilled water or sewage) on chlorophene removal. The organic compounds in sewage retarded the rate of chlorophene removal by 38%, probably by competitively reacting with the oxidizing agent and screening light. The compound 2-benzoylbenzo-1,4-quinone, benzo-1,4-quinone, hydroquinone and maleic acid were identified as primary intermediates by gas chromatography-mass spectrometry. The concentrations of acetic, formic and oxalic anions were detected by ion chromatography. A possible degradation pathway is proposed on the basis of the reaction products identified.

Treatment of radioactive ionic exchange resins by super- and sub-critical water oxidation (SCWO)

As the usage of ion exchange resins increases the inventory of spent ion exchange resins increases in nuclear power plants. This study is to find an environmental-friendly process to treat theses spent resins. The test samples were prepared by diluting the slurry made by wet ball milling the spent cationic exchange resins for 24 h. The spent cationic exchange resins were separated from mixed ion exchange resins by a fluidized bed gravimetric separator. The decomposition of the samples was investigated with super-critical water oxidation (SCWO) equipment. A statistical test method – the central composite design as a statistical design of experiments – was adopted to find the optimum condition to decompose the spent exchange resins. The optimum condition was 60% of excess oxygen, 22.5 min of residence time, 0.615 wt% of NaOH, 358 of reaction temperature, and 3600 psi of reaction pressure, which is a sub-critical condition. The liquid product of the decomposition has the characteristics of 80–185 ppm of COD (Chemical Oxygen Demand), 4.0–6.0 of pH, and <1.0 ppm of corrosive components (Ni, Fe, Cr, and Mo). The exhaust gas from the SCWO equipment contained NOx of 0 ppm, SOx of 3 ppm (environment exhaust standard in Korea: NOx 200 ppm, SOx 300 ppm). Co-substituted mock samples were prepared to simulate spent cationic exchange resins from nuclear power plants which can contain radioactive Co isotopes. The conditions to obtain organic compound destruction ratio which conforms the effluent stand for the mock samples were found. The treated water filtered with 0.2-filter contained less than 1 ppm of Co. Thus Co recovery rate of more 99% was achieved.

Photooxidative destruction of organic compounds by hydrogen peroxide in water

The paper has studied the state of the art in the investigations into the kinetics and the mechanism of photoinduced oxidative destruction of organic compounds of various classes by hydrogen peroxide in aqueous media. We have analyzed the impact of physical and chemical factors (substrate structure, pH of the medium, H2O2 concentration, presence of oxygen, etc.) and the rate of the photooxidative process. The analysis of the technicoeconomic characteristics of the UV/H2O2 system in correlation with other highly effective AOP methods (Advanced Oxidation Processes) is an evidence of good prospects of using it in the technology of treating natural and industrial wastewaters from organic pollutants.

Interactions between biological and abiotic pathways in the reduction of chlorinated solvents

AbstractWhile biologically mediated reductive dechlorination continues to be a significant focus of chlorinated solvent remediation, there has been an increased interest in abiotic reductive processes for the remediation of chlorinated solvents. In situ chemical reduction (ISCR) uses zero‐valent iron (ZVI)–based technologies, such as nanoscale iron and bimetallic ZVI, as well as naturally occurring reduced minerals incorporating dual‐valent iron (DVI), such as magnetite, green rust, and iron sulfides that are capable of dechlorinating solvents. A more recent area of development in ISCR has been in combining biological and abiotic processes.There are several ways in which biological and abiotic processes can be combined. First, the interaction between the two may be “causative.” For example, the Air Force Center for Engineering and the Environment's biogeochemical reductive dechlorination (BiRD) technology combines a mulch barrier with hematite and gypsum to create an iron‐sulfide‐based reducing zone. Biodegradation under sulfate‐reducing conditions produces sulfide that combines with the hematite to form iron sulfides. As such, the BiRD technology is “causative”; the biological processes create reducing minerals. The biological generation of other reducing minerals such as magnetite, siderite, and green rust is feasible and is, with magnetite, observed in nature at some petroleum sites. A second type of interaction between abiotic and biotic processes is “synergistic.” For example, biological processes can enhance the activity of reduced metals/minerals. This is the basis of the EHC® ISCR technologies, which combine ZVI with a (slowly) degradable carbon substrate. This combination rapidly creates buffered, strongly reducing conditions, which result in more complete solvent degradation (i.e., direct mineralization). The extent and level of reducing activity commonly observed are much greater when both the carbon substrate and the ZVI are present. When the carbon substrate is expended, the reducing activity due to ZVI alone is much less. The understanding of biogeochemical processes and their impact on abiotic processes is still developing. As that understanding develops, new and improved methods will be created to enhance volatile organic compound destruction. © 2009 Wiley Periodicals, Inc.

Characterization and Visible Light Photocatalytic Activity of Cerium- and Iron-Doped Titanium Dioxide Sol−Gel Materials

Cerium- and iron-based titanium dioxide catalysts are made at varying concentrations and cured at different temperatures to develop a new class of photocatalysts that displays catalytic activity for volatile organic compound destruction when irradiated with visible light. These catalysts are characterized using X-ray diffractometry, Raman spectroscopy, UV−vis diffuse reflectance spectroscopy and BET surface area analyses. The potential of these catalysts to destroy indoor air volatile organics is evaluated using a tubular reactor flow channel with visible light irradiated interior surfaces through which air contaminated with toluene, decane, ethanol, acetaldehyde, or linalool is reacted. It was found that both cerium- and iron-doped titania have lower band-gap energy than pure titania and can be activated with visible light. The anatase and rutile phase transitions of these doped titania is however similar to pure titania and is unaffected by dopants. The crystalinity is however altered and crystal sizes in the range of six to nine nanometers were obtained with the sol−gel type synthesis of the titania catalyst. Although both cerium- and iron-based titania show destruction of these volatile organics in visible light as compared to pure titania, cerium-based titania has better performance than iron-based titania. A photocatalytic oxidation reaction pathway for linalool is proposed on the basis of previous studies and compounds are identified in the exit stream of the reactor. Further, reaction rate constants for toluene, linalool, ethanol, and acetaldheyhde have been determined using a two-dimensional diffusion model (Sidheswaran and Tavlarides, 2008), and are compared with values from literature. It has been found that cerium-doped titania developed in this study performs comparably to the commercially available titania even when irradiated with visible light.

Sonochemical decomposition of dinitrotoluenes and trinitrotoluene in wastewater

Mineralization of dinitrotoluenes (DNT) and 2,4,6-trinitrotoluene (TNT) in wastewater was conducted under ultrasonic irradiation. The batch-wise experiments were carried out to elucidate the influence of various operating parameters on the sonolytic behavior, including power intensity, acidity of wastewater, reaction temperature and oxygen dosage. It is remarkable that the nitrotoluenes contained could be almost completely decomposed by the sonochemical oxidation method, wherein the pyrolytic reaction was responsible for the destruction of organic compounds. During the sonication tests, the influence of reaction temperature on the degradation of nitrotoluenes is the most significant, followed by power intensity, acidity of wastewater and oxygen dosage. Based on the spectra obtained from gas chromatograph/mass spectrometer (GC/MS), it is suggested that 2,4,6-TNT is preliminarily denitrated to 2,6-DNT. The denitration of 2,6-DNT and/or 2,4-DNT results in the formation of o-mononitrotoluene, which proceeds with the cleavage of nitro group into toluene, followed by oxidation of methyl group and decarboxylation. In this study, it is believed that the sonolytic technique established is promising for wastewater disposal in toluene nitration processes.