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Query: UMLS:C1835664 (TOC)
 2,763 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this study ozone and the H2O2/O3 oxidation system are used to decolorize aqueous solutions of Orange II (Or-II) and Acid Red 27 (AR-27). Investigations are carried out in a semi-batch bubble column reactor. A system of series-parallel reactions is proposed to describe the mechanism of dye oxidation. The stoichiometric ratio for the first reaction is found to be 1 mol dye per mol O3, while the overall ozone demand for both reactions one and two is found to be 5 and 6 moles for Or-II and AR-27 respectively. Molecular and radical kinetics are compared: a radical scavenger, t-butanol, can be added to ensure only the molecular reaction of ozone, or hydrogen peroxide can be supplied through a peristaltic pump, to initiate radical reactivity. Results reveal that colour removal is ensured by direct ozone attack. For both dyes, TOC removal efficiencies of 50 - 60 % are obtained by the action of the hydroxyl free radical. However, this is not improved by addition of H2O2, thus demonstrating that organic species alone ensure HO degrees radical production during ozonation. Both the mass transfer and the ozone reactivity with the dyes are considered to evaluate the kinetic parameters for the molecular pathway.
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PMID:Oxidation pathways for ozonation of azo dyes in a semi-batch reactor: a kinetic parameters approach. 1517 46

Orange II, C.I. Acid Orange 7 (AO7), is oxidatively decolorized via catalytic oxidation by iron(III) phthalocyanine-tetrasulfonic acid (Fe(III)-PcTS) as a biomimetic catalyst and KHSO(5) as an oxygen donor. The nature of the decolorization of AO7 was investigated in the catalyst concentration range of 10-50 microM, in which the initial concentration of AO7 was 417 mg l(-1). A 99.6% decolorization was observed at [KHSO(5)] = 2.5 mM and [Fe(III)-PcTS] = 20 microM after a 3-h reaction period. However, the fact that only 4.9% of the TOC was removed indicated that the conversion to CO(2) was incomplete. The results of a total organic nitrogen analysis of the reaction mixture showed that the nitrogen in the azo chain was mainly converted to N(2) gas. In addition, 38.6% of the AO7 was converted to 1,2-dihydroxynaphthalene, and 21.4% to p-phenolsulfonic acid. These results indicate that the degradation via this catalytic system involves the conversion of AO7 to phenolic compounds, followed by N(2) production. In addition, a Microtox test showed that toxicity of the solution increased as a result of AO7 oxidation using this catalytic system.
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PMID:Decolorization of orange II by catalytic oxidation using iron (III) phthalocyanine-tetrasulfonic acid. 1551 89

Discoloration and mineralization of an azo dye Orange II was conducted by using a bentonite clay-based Fe nanocomposite (Fe-B) film as a heterogeneous photo-Fenton catalyst in the presence of UVC light and H(2)O(2). Under optimal conditions (pH=3.0, 10 mM H(2)O(2), and 1 x 8W UVC), 100% discoloration and 50-60% TOC removal of 0.2 mM Orange II can be achieved in 90 and 120 min, respectively. The mineralization kinetics of 0.2 mM Orange II is much slower than the corresponding discoloration kinetics. Under the same conditions, the Fe leaching from the Fe-B-coated catalyst film is very low. The Fe-B-coated catalyst film could be used in the pre-treatment of wastewater for an integrated system consisting of a photochemical reactor and a biological reactor. Multi-run experimental results reveal that the Fe-B-coated catalyst film could have a long-term stability for the discoloration and mineralization of Orange II. A comparison between the performance of the Fe-B-coated catalyst film and a suspended Fe-B catalyst in the discoloration and mineralization of Orange II was also discussed.
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PMID:Discoloration and mineralization of Orange II by using a bentonite clay-based Fe nanocomposite film as a heterogeneous photo-Fenton catalyst. 1560 68

Modification of beta-PbO(2) electrodes was carried out by TiO(2) co-deposition and characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The 2.0 g TiO(2) (the amount of TiO(2) used in 200 mL electrodeposition solution) modified beta-PbO(2) electrode was more compact and more uniform in comparison with the unmodified beta-PbO(2) electrode. TiO(2) particles were tightly attached on and between beta-PbO(2) crystals on modified beta-PbO(2) electrode. It was also used in electrochemically assisted photocatalytic degradation (EAPD) of Acid Orange 7. Compared with the total efficiency by a single application of ultraviolet irradiation and electrochemical procedure, application of a 1.5 V potential in EAPD improved the apparent first-order rate constant by 44.2% for 2.0 g TiO(2) modified beta-PbO(2) electrode even if it was not freshly used. A synergetic effect was significant. Within the amount of TiO(2) investigated, the more TiO(2) used in electro-deposition solution, the higher the degradation efficiencies were. Effects of initial dye concentration, initial pH values and applied potentials across the electrodes were investigated. Acidic condition and high potentials applied across the electrodes favored color or TOC removal of the dye. Decolorization rate decreased with an increase in the dye concentration in the range of 5-50mg/L. Experiments above demonstrate that TiO(2) modified beta-PbO(2) electrode, which realized TiO(2) immobilization successfully, performed well in EAPD of Acid Orange 7.
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PMID:Electrochemically assisted photocatalytic degradation of Acid Orange 7 with beta-PbO2 electrodes modified by TiO2. 1638 94

Although homogeneous photo-Fenton system is a very efficient method for organic wastewater treatment, it suffers from costly pH adjustment as well as difficult separation of catalysts from aqueous in practical application. Through cation exchange reaction, hydroxyl-Fe-pillared bentonite (H-Fe-P-B) was successfully prepared as a solid catalyst for UV-Fenton to degrade non-biodegradable azo-dye Orange II. Compared with raw bentonite, the content of iron, interlamellar distance and external surface area of H-Fe-P-B increased remarkably. H-Fe-P-B had good photosensitivity and catalyst reactivity. And the catalytic activity of H-Fe-P-B for H(2)O(2) came from hydroxyl-Fe between sheets rather than Fe(3+) or Fe(2+) in tetrahedral or octahedral sheets of bentonite. In UVA-H(2)O(2) system, H(2)O(2) could destroy the azo bond of excited Orange II molecules but could not effectively mineralize it. After 120 min treatment, 83% discoloration was obtained while only 2% of TOC was removed. When H-Fe-P-B was used as catalyst, a significant degradation of Orange II was observed at the same condition as UVA-H(2)O(2) system. Almost 100% discoloration and more than 60% TOC removal of Orange II could be achieved after 120 min treatment. Because of the strong surface acidity and the electronegativity of H-Fe-P-B, the pH range of this catalyst in the Orange II discoloration could be extended up to 9.5. And this catalyst showed good stability during Orange II degradation in water in wide range of pH (3.0-9.5). These results indicated that the H-Fe-P-B was a promising catalyst for UV-Fenton system.
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PMID:Catalytic degradation of Orange II by UV-Fenton with hydroxyl-Fe-pillared bentonite in water. 1673 46

The comparison of different advanced oxidation processes (AOPs), i.e. ultraviolet (UV)/TiO(2), O(3), O(3)/UV, O(3)/UV/TiO(2), Fenton and electrocoagulation (EC), is of interest to determine the best removal performance for the destruction of the target compound in an Acid Orange 6 (AO6) solution, exploring the most efficient experimental conditions as well; on the other hand, the results may provide baseline information of the combination of different AOPs in treating industrial wastewater. The following conclusions can be drawn: (1) in the effects of individual and combined ozonation and photocatalytic UV irradiation, both O(3)/UV and O(3)/UV/TiO(2) processes exhibit remarkable TOC removal capability that can achieve a 65% removal efficiency at pH 7 and O(3) dose=45mg/L; (2) the optimum pH and ratio of [H(2)O(2)]/[Fe(2+)] found for the Fenton process, are pH 4 and [H(2)O(2)]/[Fe(2+)]=6.58. The optimum [H(2)O(2)] and [Fe(2+)] under the same HF value are 58.82 and 8.93mM, respectively; (3) the optimum applied voltage found in the EC experiment is 80V, and the initial pH will affect the AO6 and TOC removal rates in that acidic conditions may be favorable for a higher removal rate; (4) the AO6 decolorization rate ranking was obtained in the order of O(3)<O(3)/UV=O(3)/UV/TiO(2)<EC<Fenton; (5) the ranking of TOC removal efficiency of selected AOPs was in the order of O(3)=Fenton<EC<O(3)/UV<O(3)/UV/TiO(2) for 30min of reaction time.
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PMID:The decolorization and mineralization of acid orange 6 azo dye in aqueous solution by advanced oxidation processes: a comparative study. 1722 65

An innovative way to fix preformed nanocrystalline TiO(2) on low-density polyethylene film (LDPE-TiO(2)) is presented. The LDPE-TiO(2) film was able to mediate the complete photodiscoloration of Orange II using about seven times less catalyst than a TiO(2) suspension and proceeded with a photonic efficiency of approximately 0.02. The catalyst shows photostability over long operational periods during the photodiscoloration of the azo dye Orange II. The LDPE-TiO(2) catalyst leads to full dye discoloration under simulated solar light but only to a 30% TOC reduction since long-lived intermediates generated in solution seem to preclude full mineralization of the dye. Physical insight is provided into the mechanism of stabilization of the LDPE-TiO(2) composite during the photocatalytic process by X-ray photoelectron spectroscopy (XPS). The adherence of TiO(2) on LDPE is investigated by electron microscopy (EM) and atomic force microscopy (AFM). The thickness of the TiO(2) film is seen to vary between 1.25 and 1.69 microm for an unused LDPE-TiO(2) film and between 1.31 and 1.50 microm for a sample irradiated 10h during Orange II discoloration pointing out to a higher compactness of the TiO(2) film after the photocatalysis.
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PMID:Preparation, stabilization and characterization of TiO(2) on thin polyethylene films (LDPE). Photocatalytic applications. 1723 33

A combination of ferric chloride and sodium nitrite significantly improved the wet oxidation of the azo dye Acid Orange 7 (AO7) in acid aqueous media (pH 2.6) under moderate conditions (T=150 degrees C; oxygen pressure=0.5 MPa). To evaluate the catalytic system, wet oxidation of AO7 was carried out at temperatures between 90 and 150 degrees C and oxygen pressures ranging from 0.1 to 0.5 MPa. The effect of initial solution pH from 2.6 to 11.4 and the amount of catalyst on the degradation of AO7 were also investigated. AO7 initial concentration was kept 200 mg L(-1). The degradation process was monitored by UV-visible spectroscopy, HPLC, IC (ion chromatography), GC-MS and TOC analysis. At 150 degrees C and 0.5 MPa oxygen pressure, 56% TOC was removed after 4h of treatment, while no obvious TOC removal were achieved without catalyst at the same experimental condition. The main degradation products were some small organic acids: formic acid, acetic acid, pyruvic acid, oxalic acid, succinic acid (identified and quantified by IC) and phthalic acid (identified by GC-MS).
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PMID:NaNO(2)/FeCl(3) catalyzed wet oxidation of the azo dye Acid Orange 7. 1817 19

The simulative wastewater containing Acid Orange 7 (AO7) of 300 mg/L was electrolytically treated by a three-phase three-dimensional electrode reactor. Particular attention was paid on the comparison of treatment efficiency of different cathodes in the system. Intermediate products and concentration of *OH and H2O2 were further investigated using HPLC, UV-Vis scan and GC-MS, with the purpose of investigating the electrolysis behavior of AO7 with different cathodes. Results showed that activated carbon fiber (ACF) cathode was more effective than graphite or stainless steel cathode. Despite all of the three investigated cathodes showed high efficiency in the decolorization of AO7 (more than 96% after 60 min of electrolysis under 20 V), the TOC removal ratio of ACF system (57.4%) was much higher than those of the other two. Although the generation of *OH and H2O2 were both found in the three systems, the concentration in the system with ACF as the cathode was much higher than those in the other two, which resulted in the better mineralization ability. Moreover, the same degradation route of AO7 was found in the three systems, which involved the generation of ketone and naphthol compounds.
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PMID:[Effect of cathode material on electrolytic treatment of Acid Orange 7 by a three-phase three-dimensional electrode reactor]. 1863 43

A comparative study of the degradation of Acid Orange 7 (AO 7) aqueous solutions in acidic medium of pH 3.0 by electro-Fenton process using Pt or boron-doped diamond (BDD) anode was reported. The oxidative degradation of AO 7 by electrochemically generated hydroxyl radicals follows a pseudo-first order kinetic with a similar rate constant with BDD or Pt anode. The absolute rate constant of the AO 7 hydroxylation reaction was determined as (1.10+/-0.04)x10(10)M(-1)s(-1) by using the competition kinetic method. The comparative study of TOC measurements during electro-Fenton treatment showed a higher mineralization rate with BDD than Pt anode at the first hours of electrolysis because of the higher oxidizing power of this anode. The electro-Fenton degradation of AO 7 was followed by monitoring the formation and evolution of aromatic intermediates which are oxidized to aliphatic carboxylic acids before mineralization (transformation to CO(2) and inorganic ions, i.e. sulphate, nitrate and ammonium). The follow-up of the solution toxicity evolution shows the formation of intermediates more toxic than AO 7 and the connection between toxicity and aromaticity. A mineralization reaction pathway of AO 7 by electro-Fenton degradation involving all the intermediates identified was proposed.
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PMID:Degradation of Acid Orange 7 by electrochemically generated (*)OH radicals in acidic aqueous medium using a boron-doped diamond or platinum anode: a mechanistic study. 1876 Aug 22


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