Sulfur Heteroatoms Research Articles

Characterization of Sulfur Compounds in Oilsands Bitumen by Methylation Followed by Positive-Ion Electrospray Ionization and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Sulfur compounds in Canadian oilsands bitumen were reacted with methyl iodide in the presence of silver tetrafluoroborate and converted to methylsulfonium salts. The methylsulfonium salts were characterized by positive-ion electrospray ionization (ESI) and Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS). Heteroatoms were characterized by their class (number of nitrogen, oxygen, and sulfur heteroatoms), type [rings plus double bonds (DBE)], and carbon number distribution. The S1, S2, S3, O1S1, O1S2, O2S1, and N1S1 sulfur-containing class species were identified in bitumen-derived methylsulfonium salts. The molecular weights of the sulfur compounds were varied from 200 to 700 Da. The Sx class species were the predominant heteroatom compounds. The S1, S2, and S3 class species comprised 74%, 11%, and 1%, respectively, of the total identified species. As the sulfur atom number increased, the DBE of the abundant Sx class species shifted to a higher value. Sulfur species identified from...

Crystal Structure of 3-(4-Methoxy-benzylidene)-isothiochroman-4-one

Abstract The title compound, 3-(4-methoxy-benzyli-dene)-isothiochroman-4-one (C 17 H 14 O 2 S) was preparedfrom the reaction of isothiochroman-4-one with benzalde-hyde in the presence of small amount of HCl. The structureof the synthesised compound was determined by IR, 1 HNMR and X-ray crystallography. The structure was solvedin monoclinic, space group P2 1 /n with a = 3.9773 (7) A˚ ,b = 10.918 (2) A˚ , c = 30.609 (6) A˚ , b = 90.615 (3) ,V = 1329.1 (4) A˚ 3 ,Z= 4 and with R int = 0.047. Thebicyclic ring of isothiochroman-4-one moiety does notadopt a planar geometry. The molecular conformation isstable via C10–H O1 and C16–H S1 intramolecularhydrogen-bonding interactions. These contacts involvemolecules in an extended two-dimensional sheet to the bcplane.Keywords Crystal structure 3-(4-Methoxy-benzylidene)-isothiochroman-4-one Benzaldehyde Isothiochroman-4-oneIntroductionSpiro-heterocyclic compounds containing one or two func-tionalised arms at various positions have emerged aspotentially interesting drugs owing to their patented selec-tive antitumoral behaviour against breast-cancer (MCF7-strains) [1], antitubercular agents [2] or anti-HIV agents [3].These studies showed that spiro-heterocyclic compoundsbearing an oxygen or sulfur heteroatom in the 3-position/C=O are highly active not only as anti-tubercular oranti-HIV agents but as potential combined antitubercular/anti-HIV agents [4]. From the general structure–activityrelationship, it appears that functionalized side chain(s)characterised by pendant sites such as (O=C–Y–Z), whereY–Z is N=N or O–N, are crucial for bioactivity. Theincorporated heteroatom centres S or O on 3-position seemto have critical interactions with the bacterial cell receptorsor may be as centre donors in metal complexation. Theisothiochroman-4-one, was prepared since a long time [5]by cyclising the chloride 4-phenyl-3-thiabutanoi¨c acid innitrobenzene in presence of tri-chloride aluminium. Thechloride 4-phenyl-3-thiabutanoi¨c acid has been cyclisedby addition of trichloride aluminium in a mixture of(chloroforme/disulfure-carbone). A group of researcher [6]has improved its yield by cyclising the 4-phenyl-3-thiabut-anoi¨cacid(3)byadditionofphosphoricanhydride[P

Catalytic Performance of Symmetrical and Unsymmetrical Sulfur‐Containing Pincer Complexes: Synthesis and Tandem Catalytic Activity of the First PCS‐Pincer Palladium Complex

The synthesis and catalytic applications of a new aryl-based unsymmetrical PCS-pincer complex are reported. Preparation of the robust air- and moisture-stable PCS-pincer palladium complex 5[X] started from the symmetrical alpha,alpha'-dibromo-meta-xylene and involved the selective substitution of one bromide by PPh(2)(BH(3)), followed by substitution of the second bromide by SPh and subsequent introduction of the palladium. The new PCS complexes (5[X]) were employed as catalysts in two important organic transformations. Firstly, complex 5[Cl] displays high catalytic activity in aldol reactions but enters the catalytic cycle as a precatalyst. Secondly, complex 5[BF(4)] displays tandem catalytic activity in the coupling of allyl chlorides with aldehydes and imines in the presence of hexamethylditin. In these tandem catalytic reactions the first process is the conversion of allyl chlorides into trimethylallyltin (and trimethyltin chloride) with Sn(2)Me(6), which is followed by catalytic allylation of aldehyde and sulfonimine substrates. In addition, we present a new catalytic process for the one-pot allylation of 4-nitrobenzaldehyde with vinyloxirane. The catalytic performance of the novel PCS-pincer palladium complex was compared to those of its symmetrical PCP- and SCS-pincer complex analogues. It was concluded that the unsymmetrical PCS complex advantageously unifies the attractive catalytic features of the corresponding symmetrical pincer complexes including both (pi-) electron-withdrawing (such as phosphorus) or (sigma-) electron-donating (such as sulfur and nitrogen) heteroatoms. Thus, in the aldol reaction the PCS-pincer palladium complex 5[X] provides a high turnover frequency, while in the tandem process both reactions are catalysed with sufficiently high activity.

Discoloration and detoxicification of a Congo red dye solution by means of ozone treatment for a possible water reuse

The objective of this study was to investigate the degradation and mineralization of an azo-dye, the Congo red, in aqueous solutions using ozone. Phytotoxicity and the inhibitory effects on the microbial activity of the raw and the ozonated solutions were also carried out with the aim of water reuse and environment protection. Decolorization of the aqueous solutions, disappearance of the parent compound, chemical oxygen demand (COD) and total organic carbon (TOC) removal were the main parameters monitored in this study. To control the mineralization of the Congo red, pH of the ozonated solution and heteroatoms released from the mother molecule such NH 4 +, NO 3 − and SO 4 2− were determined. It was concluded that ozone by itself is strong enough to decolorize these aqueous solutions in the early stage of the oxidation process. Nonetheless, efficient mineralization had not been achieved. Significant drops in COD (54%) were registered. The extent of TOC removal was about 32%. Sulfur heteroatom was totally oxidized to SO 4 2− ions while the central –N N– azo ring was partially converted to NH 4 + and NO 3 −. Results of the kinetic studies showed that ozonation of the selected molecule was a pseudo-first-order reaction with respect to dye concentration. The obtained results also demonstrate that ozone process reduced the phytotoxicity of the raw solution and enhanced the biodegradability of the treated azo-dyes-wastewater. Hence, this show that ozone remains one of the effective technologies for the discoloration and the detoxification of organic dyes in wastewater.

Response of human erythroleukemia cells to heteroarotinoids

All trans‐Retinoic acid (RA) is a naturally occurring molecule that binds to retinoic acid receptors and contributes to proliferation regulation. Heteroarotinoids (Hets) are synthetic structural analogues to RA, defined as systems with one aromatic ring and one heteroatom that exhibit lower toxicity as well as increased biological activity. In this study, human erythroleukemia cells were cultured for 72 h and chemically treated for the latter 48 h with Het 1, Het 4, thapsigargin (TH) for positive apoptosis control, RA for biological activity standard, and no treatment for control. Cells were assayed for viability and growth inhibition using trypan blue exclusion, relative levels of apoptosis induction using Hoechst stain and propidium iodide with fluorescent microscopy, and tissue transglutaminase (tTG) expression. RA showed the least growth inhibition and apoptosis induction relative to Het 1 and Het 4. Het 1 and Het 4 showed approximately equivalent growth inhibition relative to control, three‐fold greater than RA. Het 1 and Het 4 resulted in a 89% and 77% apoptosis induction relative to TH respectively. Het 1 and Het 4 also showed a 4‐5‐fold increase in apoptosis relative to control. Both Het 1 and Het 4 contain sulfur heteroatoms and the increased biological activity of Het 1 is attributed to the presence of a thiourea link. Relative to other modifications, changes to the end of the side chain made virtually no enhancement. Support for this research was supplied by the College of Health, Science and Environment and Faculty/Student Research Grant program of Slippery Rock University.

Modified prostaglandins: New possibilities for the pharmacological control of immunodeficient states

The role of exogenous prostaglandins (PGs) as immune response and allergic inflammation regulators and the existing notions of the interaction between synthetic PGs or their modified analogs with prostanoid receptors are considered. Based on the principles of structural complementarity, the immunotropic effects of new synthetic 11-deoxyprostanoids of the E1, E2, and F2α series, modified at the α-and ω-chains and containing pharmacophores at various positions of the prostanoid skeleton, were studied as dependent on the dose and the chemical structure. It is established that prostanoids of the E series, which are deprived of oxo and hydroxy groups at the cyclopentane ring but contain a complete or nearly complete α-chain and a malonic ether fragment at the ω-chain, exhibit no immunotropic activity. On the other hand, the PG analogs containing 9-keto groups enhance both the cellular and humoral immunogenesis in mice immunized (sensitized) with sheep red blood cells. The presence of an oxo group at position 7 is also important for the immunopositive response and the pharmacological activity. The enhancement of the ligand — receptor interaction is retained upon replacing the cyclopentane fragment by the bicycloheptane moiety. The ω-chain modification by incorporating a sulfur heteroatom at position 13 caused no substantial changes in the immunomodulating activity, whereas the ω-chain modification resulting in the formation of 1-amino-3-oxo-oct-1-enyl fragment can be considered as an important condition for obtaining immunopositive prostanoids. As a rule, the ability to enhance the humoral immunity was increased on going from the E to F series of prostanoids. The pharmacodynamic parameters of the immune response evidenced a high affinity of F-prostanoids to EP receptors. It can be suggested that F-prostanoids may act as agonists of these receptors. From this standpoint, a decrease in the immunoactivity of compounds having too bulky fragments in the ω-chain is quite reasonable. Thus, some of the ligands affine to prostanoid receptors are worthy of attention as prototypes of safe and efficient low-molecular immunoregulators of a new generation.

Excited state behaviour of some thio-analogues of 1,3-distyrylbenzene

The excited state properties of 1, n-distyrylbenzene ( n = 2, 3 or 4) and hetero-analogues have being investigated in the authors’ laboratory by fluorimetry, nanosecond and femtosecond laser flash photolysis, and conventional photochemical techniques as well as by the help of theoretical calculations. The aim of the present article is to survey recent results of the study on the internal rotation around double bonds, i.e. cis– trans photoisomerization ( cis and trans are indicated in the text by Z and E, respectively) and single bonds (i.e. conformational equilibria) in some thio-analogues of E, E-1,3-distyrylbenzene where the central or side benzene rings were replaced by thiophene rings. Some peculiarities in the photobehaviour of these compounds will be thus evidenced. The main effect of the sulphur heteroatom in the side rings is a decrease in the radiative relaxation and an increase in the E, E → Z, E photoisomerization yield caused by decreased torsional barriers in S 1 and/or increased triplet yields, which opens the way to isomerization in the triplet manifold. On the other hand, when sulphur is in the central ring, the fluorescence decrease favours non-reactive and non-radiative deactivations. In the case of 2,5-distyrylthiophene with a central thiophene ring, the photobehaviour of the stereoisomers with one or both cis double bonds ( Z, E and Z, Z) showed diabatic/adiabatic formation of the E, E isomer in both lowest excited states of singlet and triplet multiplicities. In the case of Z, Z, the adiabatic process (directly from Z, Z * to E, E *) is characterized by a “one photon–two bonds” mechanism. The presence of conformational equilibria in solutions of distyrylbenzenes was found to play a role in their relaxation properties since different conformers can have different deactivation channels, specifically in the case of the 1,3 compound with side 3′-thienyl groups. The results obtained by selective irradiation, as a function of the excitation wavelength and temperature, and supported by theoretical calculations, evidenced uncommon rotamer interconversion during the short S 1 lifetime of this compound.

Destruction of chemical agent simulants in a supercritical water oxidation bench-scale reactor

A new design of supercritical water oxidation (SCWO) bench-scale reactor has been developed to handle high-risk wastes resulting from munitions demilitarization. The reactor consists of a concentric vertical double wall in which SCWO reaction takes place inside an inner tube (titanium grade 2, non-porous) whereas pressure resistance is ensured by a Hastelloy C-276 external vessel. The performances of this reactor were investigated with two different kinds of chemical warfare agent simulants: OPA (a mixture of isopropyl amine and isopropyl alcohol) as the binary precursor for nerve agent of sarin and thiodiglycol [TDG, (HOC 2H 4) 2S] as the model organic sulfur heteroatom. High destruction rates based on total organic carbon (TOC) were achieved (>99.99%) without production of chars or undesired gases such as carbon monoxide and methane. The carbon-containing product was carbon dioxide whereas the nitrogen-containing products were nitrogen and nitrous oxide. Sulfur was totally recovered in the aqueous effluent as sulfuric acid. No corrosion was noticed in the reactor after a cumulative operation time of more than 250 h. The titanium tube shielded successfully the pressure vessel from corrosion.

Potent Adenosine A1 and A2A Receptors Antagonists: Recent Developments

This review summarizes the current tendencies observed in the past 5 years in the development of A(1) and A(2A) adenosine receptor antagonists performed in various academia and industry. A(1) and A(2A) AR antagonists are as well xanthines as heteroaromatic derivatives and are most commonly 6:5 fused heteroatomic compounds. Among xanthine-based compounds, some common features could be pointed out. The recent A(1) AR ligands which show good biological profile, possess long alkyl chains in position 1 and 3 as well as bulky C(8)-substituent, while A(2A) AR antagonists with a high A(2A) AR affinity are C(8)-styryl substituted with N(1)-alkyl/alkynyl moiety or fused tricyclic xanthines possessing heteroatom(s) in the third cycle. The research in the field of heteroaromatic A(1) and A(2A) ARs antagonists impressively has a wide range. Ligands are as well non-fused monocyclic substituted compounds as fused bi- and tricyclic derivatives with the nitrogen, oxygen and sulfur heteroatoms. Most often, adenosine A(1) receptor non-xanthine antagonists are adenine-based, having substituted amino group and variable nitrogen atoms positions in the molecules. A(2A) AR ligands show good affinity when furanyl function, which is crucial for binding, is present in the fused bicyclic and tricyclic analogs. Moreover, tricyclic nitrogen containing antagonists in order to be active, frequently possess long-alkylphenyl moiety.

Photocatalytic degradation of an azo dye in a tubular continuous-flow photoreactor with immobilized TiO2 on glass plates

Abstract The photocatalytic degradation of C.I. Acid Red 27 (AR27), an anionic monoazo dye of acid class, in aqueous solutions was investigated in a tubular continuous-flow photoreactor with immobilized TiO2 on glass plates. The removal percent is a function of photoreactor length, volumetric flow rate and light intensity. The removal efficiency increases as the light intensity increases but it decreases when the flow rate is increased. The AR27 degradation was followed through HPLC, UV–vis and chemical oxygen demand (COD) analyses. The results of these analyses showed that the final outlet stream from the photoreactor was considerably mineralized. NH4+, NO3−, NO2− and SO42− ions were analyzed as mineralization products of nitrogen and sulfur heteroatoms, respectively. Results show that the final concentration of SO42− ions and N-containing mineralization products are less than the final expected stoichiometric values. Based on the results obtained in present and previous studies, a reaction pathway for the photocatalytic degradation of AR27 is proposed. The kinetic analysis of the decolorization of AR27 in continuous-mode shows a pseudo-first-order reaction. Results show that a linear relation exists between pseudo-first-order reaction rate constant and reciprocal of volumetric flow rate.

Photocatalytic degradation of C.I. Acid Red 27 by immobilized ZnO on glass plates in continuous-mode

The photocatalytic degradation of C.I. Acid Red 27 (AR27), an anionic monoazo dye of acid class, in aqueous solutions was investigated with immobilized ZnO catalyst on glass plates in a continuous-mode. In the slurry ZnO system the separation and recycling of the photocatalyst is practically difficult. Thus, ZnO was immobilized on solid supports to solve this problem. The removal percent increases with increasing the photoreactor volume and light intensity but it decreases when the flow rate is increased. With decreasing flow rate from 43 to 15 ml min −1, the complete decolorization and degradation was obtained at around 748 and 1080 cm 3 from photoreactor volume. The increase in the light intensity from 21.4 to 58.5 W m −2 increases the decolorization from 23 to 57.6% and degradation from 17.5 to 37.8% for 374 cm 3 of photoreactor volume. NH 4 +, NO 3 −, NO 2 − and SO 4 2− ions were analyzed as mineralization products of nitrogen and sulfur heteroatoms. Results showed that final concentration of SO 4 2− ions and N-containing mineralization products were less than the finally expected stoichiometric values. The positive slope of production of NH 4 +, NO 3 − and NO 2 − shows that these compounds are initial products resulting directly from the initial attack on the nitrogen-to-nitrogen double bond (–N N–) of the azo dye.

Calorimetric and Computational Study of 1,4-Dithiacyclohexane 1,1-Dioxide (1,4-Dithiane Sulfone)

This work reports the enthalpies of formation in the condensed and gas state of 1,4-dithiacyclohexane 1,1-dioxide (1,4-dithiane sulfone, 5), derived from the enthalpy of combustion in oxygen, measured by a rotating bomb calorimeter and the variation of vapor pressures with temperatures determined by the Knudsen effusion technique. The theoretically estimated enthalpy of formation was calculated from high-level ab initio molecular orbital calculations at the G2(MP2) level. The theoretical calculations appear to be in very good agreement with experiment. A comparison of the conversion of thiane sulfone 3 to 1,3-dithiane sulfone 4 and 1,4-dithiane sulfone 5 clearly shows the 1,3 isomer to be 6.7 kJ mol(-1) less stable, probably owing to diminished electrostatic repulsion between the sulfur heteroatoms in 1,4-sulfone 5.

New revelations on the nature of organic matter in ice cores

Analysis of organic species stored in ice cores provides a unique opportunity to obtain information about the environment of the past. Because of the trace nature of the organic components of interest, studying these species in molecular level detail within ice cores can be an analytical challenge. Using Fourier transform ion cyclotron resonance mass spectrometry with electrospray ionization, we have characterized, at an unprecedented molecular level, the organic material in an ice core collected from Franz Josef Land (Russia). Several thousand distinct molecular species are identified and provide clues to the principal sources of the organic matter. Humic‐like substances have been identified in both modern and ancient ice, despite the remote marine setting of the ice field. Species containing sulfur heteroatoms are far more abundant in the modern ice, indicating that anthropogenic sulfur emissions are also present in the high–molecular weight organic compounds preserved in ice.

Periodic trends and easy estimation of relative stabilities in 11-vertex nido-p-block-heteroboranes and -borates.

Density functional theory computations were carried out for 11-vertex nido-p-block-hetero(carba)boranes and -borates containing silicon, germanium, tin, arsenic, antimony, sulfur, selenium and tellurium heteroatoms. A set of quantitative values called “estimated energy penalties” was derived by comparing the energies of two reference structures that differ with respect to one structural feature only. These energy penalties behave additively, i.e., they allow us to reproduce the DFT-computed relative stabilities of 11-vertex nido-heteroboranes in general with good accuracy and to predict the thermodynamic stabilities of unknown structures easily. Energy penalties for neighboring heteroatoms (HetHet and HetHet′) decrease down the group and increase along the period (indirectly proportional to covalent radii). Energy penalties for a five- rather than four-coordinate heteroatom, [Het5k(1) and Het5k(2)], generally, increase down group 14 but decrease down group 16, while there are mixed trends for group 15 heteroatoms. The sum of HetHet′ energy penalties results in different but easily predictable open-face heteroatom positions in the thermodynamically most stable mixed heterocarbaboranes and -borates with more than two heteroatoms. FigureCorrelation of HetHet′ and HetC increments with covalent radii of group 15 heteroatomsElectronic Supplementary MaterialSupplementary material is available for this article at http://dx.doi.org/10.1007/10.1007/s00894-005-0037-3 and is accessible for authorized users.

Supercritical Water Oxidation of Thiodiglycol

The total organic carbon (TOC) disappearance kinetics of the model organic sulfur heteroatom, thiodiglycol [TDG, (HOC2H4)2S], was investigated in an isothermal continuous tubular reactor under supercritical water oxidation (SCWO) conditions. The experiments were conducted at a temperature of 397−617 °C and a fixed pressure of 25 MPa, with a residence time that ranged from 9 s to 40 s. The initial TOC concentrations of TDG were varied from 1.75 mmol/L to 21.04 mmol/L and the oxygen concentrations were varied from 110% to 440% of the stoichiometric requirement. All the TOC conversions were >90% under the above experimental conditions. The major sulfur-containing products of the reaction were sulfuric acid and hydrogen sulfide, whereas the carbon-containing products included carbon monoxide, methane, and carbon dioxide. By taking into account the dependence of the oxidant and TOC concentration on the reaction rate, a global TOC disappearance rates expression was regressed from the data of 58 experiments, to ...

Kinetics of heterogeneous photocatalytic degradation of reactive dyes in an immobilized TiO 2 photocatalytic reactor

The photocatalytic degradation of two reactive dyes has been investigated by UV/TiO 2/H 2O 2 using an immobilized TiO 2 photocatalytic reactor. Reactive Blue 8 (RB 8) and Reactive Blue 220 (RB 220) textile dyes were used as model compounds. Photocatalytic degradation processes were performed using a 5-L solution containing dyes. The initial concentrations of dyes were 50 mg/L. The radiation source was two 15 W UV-C lamps. A batch mode immersion photocatalytic reactor was utilized. UV–vis and ion chromatography (IC) analyses were employed to obtain the details of the photodegradation of the selected dyes. Colored synthetic waters were completely decolorized in relatively short time after UV irradiation in the presence of various concentrations of hydrogen peroxide. Formate, acetate, oxalate, and glyoxylate anions were detected as dominant aliphatic intermediates where they were further oxidized slowly to CO 2. The UV/TiO 2/H 2O 2 process was able to oxidize the dyes with partial mineralization of carbon, nitrogen, and sulfur heteroatoms into CO 2, NO − 3, and SO 2− 4, respectively. Kinetics analysis indicates that the photocatalytic decolorization rates of the dye can be approximated by a pseudo-first-order model. The UV/TiO 2/H 2O 2 process proved to be capable of decolorization and mineralization of the reactive dyes (RB 8 and RB 220).

Theoretical Study on Electronic Structure and Optical Properties of Phenothiazine-Containing Conjugated Oligomers and Polymers

The application of polyfluorenes in polymeric light-emitting diodes has been hampered because of the charge injection difficulties and the troublesome formation of a tailed emission band at long wavelengths (>500 nm) during device fabrication and operation, leading to both a color instability and reduced efficiency. The incorporation of the phenothiazine units has been proven to significantly enhance the hole injection and charge carrier balance and at the same time efficiently suppress the keto defect emission. In this contribution, we apply quantum-chemical techniques to investigate poly[10-(N-(2'-methyl)phenothiazine-3,7-diyl) and its fluorene copolymer poly[10-(N-(2'-methyl)phenothiazine-3,7-diyl)-co-alt-2,7-(9,9-dimethylfluorene)] (PFPTZ) and gain a detailed understanding the influence of phenothiazine units on the electronic and optical properties of fluorene derivatives. Density functional theory (DFT) and time-dependent DFT approaches are employed to study the neutral molecules, HOMO-LUMO gaps (Delta(H-L)), the lowest excitation energies (E(g)'s), positive and negative ions, as well as the IPs and EAs, focusing on the superiority of the electronic and optical properties attributed to the introduction of electron-donating moiety phenothiazine (PTZ) through comparing with pristine polyfluorene. The outcomes show that the highly nonplanar conformation of phenothiazine ring in the ground state preclude sufficiently close intermolecular interactions essential to forming aggregates or excimers. Furthermore, the HOMO energies lift about 0.4 eV, and thus, the IPs decrease about 0.3 eV in PFPTZ, suggesting the significant improved hole-accepting and transporting abilities, due to the electron-donating properties of phenothiazine ring by the presence of electron-rich sulfur and nitrogen heteroatoms and highly nonplanar characters, resulting in the enhanced performances in both efficiency and brightness compared with pristine polyfluorene. In addition, even though the introduction of electron-donating moiety PTZ onto fluorene leads to a slight bathochromic shift in absorption and emission spectra, the copolymer still exhibited strong blue emission.

Photooxidative degradation of Acid Red 27 in a tubular continuous-flow photoreactor: influence of operational parameters and mineralization products

The decolorization and mineralization of Acid Red 27 (AR27), an anionic monoazo dye of acid class, was investigated using UV radiation in the presence of H 2O 2 in a tubular continuous-flow photoreactor as a function of oxidant concentration, reactor length, flow rate and light intensity. The removal efficiency of AR27 depends on the operational parameters and increases as the initial concentration of H 2O 2 and light intensity are increased but it decreases when the flow rate is increased. The AR27 degradation was followed through HPLC, UV–vis and COD analyses. The results of these analyses showed that the final outlet stream from the photoreactor was completely mineralized. The UV/H 2O 2 process was also able to mineralize nitrogen and sulfur heteroatoms into NH 4 +, NO 3 −, NO 2 − and SO 4 2− ions, respectively. The nitrogen of azo group was transformed predominantly to NH 4 + ions. Decreasing the flow rate results in the reduction of COD and promotion of SO 4 2− at the final outlet stream of the photoreactor.

Photocatalytic degradation of the alimentary azo dye amaranth: Mineralization of the azo group to nitrogen

The photocatalytic degradation of amaranth, an alimentary dye, was investigated in an irradiated titanium dioxide aqueous suspension. FT-IR spectroscopy of amaranth adsorbed on TiO2 powder provided an insight to the mode of its adsorption on TiO2 via the sulfonate group located in the ortho-position with respect to the OH group. The photodisappearance of amaranth was followed by monitoring the degradation of the dye either by UV-Vis spectroscopy or by HPLC/UV-Vis analysis while the total mineralization was monitored by DCO, TOC, GC/catharometer and HPLC ion-chromatography. A prompt removal of the colors was observed which was, however, slightly less rapid than the disappearance of amaranth itself; this indicates the presence of other colored molecules, such as hydroxylated or desulfonated amaranth as suggested by the initial changes in DCO, TOC and sulfate concentrations. In addition to the decolorization, TiO2/UV-based photocatalysis was simultaneously able to fully oxidize the dye, with a complete mineralization of organic carbon into CO2. Sulfur heteroatoms were converted into SO42− ions, which remain partially adsorbed on TiO2, while the central –N=N– azo group was 100% selectively transformed into gaseous dinitrogen this represents. An ideal issue for the elimination of a nitrogen-containing pollutants. A TiO2-mediated photodegradation mechanism for the evolution of aliphatic organic acids during the amaranth photocatalytic degradation was proposed.The formation of lactic and formic acids at the beginning of irradiation-time is indicative of a the fast and easy naphtalenic ring breaking.

Dioxirane Oxidation of Sulfur‐Containing Organic Compounds

AbstractFor Abstract see ChemInform Abstract in Full Text.