Sulfide Anion Research Articles

Anthraquinone polymer catalysts for alkaline delignification of lignocellulosic matter. Part 3. Delignification of softwood and action on a phenolic β-O-4 lignin model in kraft pulping conditions

Abstract The delignification action of four new anthraquinone (AQ) polystyrene catalysts – three of them linear (CP-A, CP-B, CP-C) and one cross-linked (CP-3D) – were investigated on softwood (Pinus pinaster) chips under kraft pulping conditions, and their catalytic efficiency gains (EGs) were compared to that of AQ, with EGAQ=100. The catalytic EG of the hydrophobic polymers CP-B and CP-3D was 96%, while the inherent hydrophilic catalyst CP-C showed an EG of 30%. Interpretation: hydrogen sulfide anions presented in the kraft pulp liquor might participate in the delignification mechanisms as redox active mediators in the case of the hydrophobic polymers. Moreover, the latter could be recovered after pulping, and delignification tests with the recovered materials revealed that they preserved their catalytic properties. Mechanistic studies were carried out with a phenolic β-O-4 lignin model compound in the presence or absence of glucose (mimicking the carbohydrate end groups) and/or NaSH. It was shown that the cross-linked CP-3D polymer reacted with the lignin model through electron transfer reactions, a process most likely mediated by glucose and HS- redox active species. The concept of grafting AQ into polymeric substrates is discussed in terms of reusable delignification catalysts for large-scale pulping processes under kraft conditions.

Cyclic voltammetric studies of carbon steel corrosion in chloride-formation water solution and effect of some inorganic salts

The influence of sulfide, sulfate and bicarbonate anions on the pitting corrosion behavior of carbon steel in formation water containing chloride ions were analyzed by means of cyclic voltammetry technique and complemented by X-ray diffraction (XRD) investigation. The anodic response exhibits a well-defined anodic peak A, followed by a passive region. A pronounced increase in the anodic current density is observed in the passive region at pitting potential (Epit). On the other hand, the cathodic sweep shows two cathodic peaks CI and CII. The data show that the presence of chloride ions causes pitting corrosion of carbon steel in formation water. It was found that both the pitting potential Epit and the repassivation potential (Epro) decreased with increase in Cl− ions concentration. Data clearly show that the presence of Na2S with 0.3M of chloride ions has a strong accelerating effect on the active dissolution and pitting corrosion of carbon steel in formation water, while the presence of Na2SO4 and NaHCO3 with chloride ions has an inhibiting effect on the active dissolution and pitting corrosion.

A Retrievable and Highly Selective Fluorescent Probe for Monitoring Sulfide and Imaging in Living Cells

A novel selective fluorescent chemosensor based on an 8-hydroxyquinoline-appended fluorescein derivative (L1) was synthesized and characterized. Once combined with Cu(2+), it displayed high specificity for sulfide anion. Among the various anions, only sulfide anion induced the revival of fluoresecence of L1, which was quenched by Cu(2+), resulting in "off-on"-type sensing of sulfide anion. What's more, the sensor was retrievable to indicate sulfide anions with Cu(2+), and S(2-), in turn, increased. With the addition of Cu(2+), compound L1 could give rise to a visible pink-to-yellow color change and green fluorescence quenching. The resulting yellow solution could change to pink and regenerate to green fluorescence immediately upon the addition of sulfide anion; however, no changes were observed in the presence of other anions, including CN(-), P(2)O(7)(4-), and other forms of sulfate, making compound L1 an extremely selective and efficient sulfide chemosensor. The signal transduction occurs via reversible formation-separation of complex L1Cu and CuS. What's more, the biological imaging study has demonstrated that the chemosensor can detect sulfur anions in biological systems at a relatively low concentration.

Polysulfide Poisoning of Ag Electrocatalyst during L-Ascorbate Ion Electro-oxidation in Alkaline Solution

L-ascorbate anion electro-oxidation on a silver electrode in hydroxide solution in the absence and presence of sodium polysulfide of concentrations from 1 × 10 −5 to 4.5 × 10 −4 mol/L was studied using cyclic voltammetry and electrochemical impedance spectroscopy. Both hydroxide and polysulfide ions inhibited L-ascorbate ion oxidation, with the poisoning effect of polysulfide ion being more pronounced in the potential range of −0.3 to −0.2 V/SCE. The time constants for L-ascorbate ion oxidation in the absence and presence of polysulfide were, 10 −3 to 1 × 10 −2 s and 1 × 10 −4 to 1 × 10 −2 s, respectively depending on the potential used for the impedance analysis. Based on the cyclic voltammetry findings, a mechanism for L-ascorbate oxidation in the presence of polysulfide ions was proposed. Impedance calculations based on the kinetic analysis can account for the occurrence of a negative impedance in a potential region around −0.2 V/SCE in the Nyquist polts. The electro-catalytic oxidation of L-ascorbate ion on a Ag electrode in the presence of adsorbed hydroxide and poly sulfide anions was investigated using electrochemical methods. Both hydroxide and polysulfide ions inhibited L-ascorbate ion oxidation, with the poisoning effect of polysulfide ion being more pronounced in the potential range of −0.3 to −0.2 V/SCE.

Two new ternary lanthanide antimony chalcogenides: Yb4Sb2S11.25 and Tm4Sb2Se11.68 containing chalcogenide Q2− and dichalcogenide (Q2)2− anions

Dark red and dark brown crystals of Yb4Sb2S11.25 and Tm8Sb4Se11.68, respectively, were obtained from the reaction of the elements in Sb2Q3 (Q=S, Se) fluxes. Both non-stoichiometric compounds are orthorhombic and crystallize in the same space group Pnnm, with two formula units per unit cell (a=12.446(2), b=5.341(1), c=12.058(2) for sulfide and a=13.126(2), b=5.623(1), c=12.499(2) for the selenide). Their crystal structures are dominated by lanthanide-chalcogenide polyhedra (CN=7 and 8), which share corners, edges, triangular- and square-faces to form a three-dimensional framework embedding antinomy cations. The latter are coordinated by three sulfide anions with 5(1+2+2) secondary contacts forming basically infinite chains running along [010]. The chalcogens in both compounds form chalcogenide Q2− and dichalcogenide (Q2)2− anionic units. The optical analysis made on those compounds shows that both are semiconductors with band gap of 1.71 and 1.22eV for Yb4Sb2S11.25 and Tm4Sb2Se11.75, respectively.

Decomposition of methionine by low energy electrons

In this work, we present the results from low energy (<12 eV) electron impact on isolated methionine, Met. We show that dissociative electron attachment is the operative mechanism for the sulfur content amino-acid fragmentation. The two most dominant fragments are attributed to the (Met-H)(-) and (C(4)NOH(5))(-) ions that are formed at energy below 2 eV. The formation of the latter anion is accompanied by the loss of neutral counterparts, which are most likely a water molecule and highly toxic methanethiol, CH(3)SH. Further fragments are associated with the damage at the sulfur end of the amino acid, producing the methyl sulfide anion CH(3)S(-) or sulfur containing neutrals. In the context of radiation induced damage to biological material at the nano-scale level, the present interest of methionine arises from the implication of the molecule in biological processes (e.g., S-adenosyl methionine for the stimulation of DNA methyltransferase reactions or protein synthesis).

A simple and sensitive sensor for rapid detection of sulfide anions using DNA-templated copper nanoparticles as fluorescent probes

A simple and rapid method for the detection of S(2-) anions with high selectivity and sensitivity has been developed by using random double-strand DNA-templated formation of copper nanoparticles as novel fluorescence probes in aqueous solution.

Anionic Heptadecanuclear Silver(I) Cluster Constructed from in Situ Generated 2-Mercaptobenzoic Acid and a Sulfide Anion

A novel anionic heptadecanuclear silver(I) cluster, (NH(4))(17)[(μ(6)-S)@Ag(17)(mba)(16)]·22H(2)O (1; H(2)mba = 2-mercaptobenzoic acid), was obtained by the reaction of equivalent molar silver oxide and 2,2'-dithiodibenzoic acid (H(2)dtba) under ultrasonic conditions at 50 °C. Complex 1 is a discrete cluster comprised of unexpected mba ligands on the shell and a μ(6)-S(2-) ion in the core, suggesting the occurrence of in situ S-S and S-C(sp(2)) bond cleavages of the H(2)dtba ligand. This novel cluster displays moderate orange-red emission in the solid state at room temperature.

Recovery of Poly Sulfide Anions in Basic Solution Produced by the Decomposition of H2S by Fullerene

To remove poly sulfide anions from basic solution, a fullerene/toluene solution was mixed with an aqueous solution containing S2 2- ions and agitated until the color of the aqueous phase changed from yellow to transparent. The treatment was repeated several times. During each treatment, white precipitates were produced in the aqueous phase and black crystals were formed after 4th treatment. XRD results indicated that former was elemental sulfur and the latter, fullerene-sulfur compounds. Thus, we succeed in extracting and separating poly sulfide ion from aqueous solution. By the fifth treatment, c.a. 675 S2 2- ions per one fullerene were successfully collected from the aqueous solution. This reaction can be applied to recovery of other anion species in basic solution.

Effect of CdS distribution on the photocatalytic performance of resin-CdS nanocomposites

A nanocomposite, D201-CdS, made by depositing CdS nanoparticles on a resin support (D201) was found to be a promising photocatalyst with visible light response. To elucidate the structure-activity relationship, a set of D201-CdS nanocomposites varying in CdS amount and distribution were prepared by adjusting the concentration of sulfide anion and the precipitation time. The maximum compressive strength of the nanocomposites increased first with the loading of CdS and then declined with the further increase of CdS. There was a valid shell thickness of CdS due to the limitation of visible light in penetration through the resin matrix. Within a certain range of shell thickness, the increase of shell density of CdS would be favorable for the purpose of photodegradation. The shell density could be easily tuned by adjusting the fabrication condition employed in this work, which is an important merit for the potential production and application.

A Near-Infrared Fluorescence Turn-On Sensor for Sulfide Anions

The first NIR fluorescent sensor for sulfide anions was constructed based on the displacement approach. The sensing ensemble is composed of a cyanine dye, a piperazine linker, an 8-aminoquinoline ligand, and copper. The favorable attributes of the sensor include a large NIR fluorescence turn-on signal in aqueous ethanol, high sensitivity, and high selectivity. The transition-metal-based displacement strategy may open an avenue for development of NIR fluorescent sensors for a wide variety of anion targets.

A Cu@Au Nanoparticle-Based Colorimetric Competition Assay for the Detection of Sulfide Anion and Cysteine

As an extension of our previous work, which described the unique ability of the core/shell Cu@Au nanoparticle (NP) to selectively recognize iodide, (1) herein, we wish to report the development of an alternatively sensitive and selective colorimetric detection for sulfide anion and cysteine based upon the Cu@Au NP by a competition avenue. In the absence of sulfide anion or cysteine, iodide can induce an appreciable color change of the Cu@Au NP solution from purple to red by transforming the clusters of NP to single, nearly spherical, and larger ones. However, the transformation is severely interfered by the presence of sulfide or cysteine because of a higher binding strength of the S-Au bond than the I-Au one. As a result, the clear purple-to-red color change induced by iodide is affected as a correlation with the concentration of sulfide or cysteine. By taking advantage of this fact, we can detect a concentration of 3 μM for sulfide and 0.4 μM for cysteine with the naked eye or 0.3 μM (10 ppb) for sulfide and 50 nM (6 ppb) for cysteine aided by a UV/vis spectrometer. Given the detrimental effect of hydrogen sulfide and the biological importance of cysteine, the assay may become useful in the environment monitoring, water quality inspection and biomedical diagnosis as well.

A New Disubstituted Polyacetylene Bearing Pyridine Moieties: Convenient Synthesis and Sensitive Chemosensor toward Sulfide Anion with High Selectivity

To develop sensitive and selective S2– chemosensors, a new disubstituted polyacetylene (P2) bearing pyridine moieties in the side chains was prepared conveniently through a postfunctional method, the strong green fluorescence of which could be completely quenched by Cu2+ ions at the concentration as low as 2.0 × 10–6 mol/L in diluted solutions. Based on the displacement strategy, by utilizing the much higher stability constant of the complex of S2– and Cu2+, the quenched fluorescence of the solution of P2 by Cu2+ ions could recover upon the addition of trace S2– anions, with the detection limit down to 5.0 × 10–7 mol/L. Moreover, no interference were observed from other anions, including SO32–, HSO3–, SO42–, ClO4–, I–, Br–, Cl–, F–, IO3–, HPO42–, PO43–, C2O42–, S2O32–, CO32–, AcO–, CN–, and P2O74–, making P2 a novel, sensitive, and selective sulfide probe.

Some important issues in electrochemistry of carbon steel in simulated concrete pore water Part 2 – Experimental

The prediction of corrosion damage to times that are experimentally inaccessible by a large factor (e.g. to over 1000 years) is vitally important in assessing various concepts for the disposal of high level nuclear waste. Such prediction can only be made using deterministic models, whose predictions are constrained to being ‘physically real’ by the natural laws [conservation of mass, energy, charge and mass charge equivalence (Faraday’s law)]. In this paper, the authors describe the measurement of experimental data that will allow the deterministic prediction of damage to the carbon steel overpack of the super container in Belgium’s proposed Boom Clay repository using the point defect model to extrapolate damage to future times. In this paper, the authors describe an experimental programme that is designed to generate values for various model parameters that will be required in making the damage predictions. The impact of chloride, sulphide and thiosulphate anions and mixtures of these species, on the electrochemical behaviour of carbon steel in contact with simulated concrete pore water, is examined.

Potentiometric electronic tongue to resolve mixtures of sulfide and perchlorate anions.

This work describes the use of an array of potentiometric sensors and an artificial neural network response model to determine perchlorate and sulfide ions in polluted waters, by what is known as an electronic tongue. Sensors used have been all-solid-state PVC membrane selective electrodes, where their ionophores were different metal-phtalocyanine complexes with specific and anion generic responses. The study case illustrates the potential use of electronic tongues in the quantification of mixtures when interfering effects need to be counterbalanced: relative errors in determination of individual ions can be decreased typically from 25% to less than 5%, if compared to the use of a single proposed ion-selective electrode.

Development of a heterobimetallic Ru(II)–Cu(II) complex for highly selective and sensitive luminescence sensing of sulfide anions

A heterobimetallic ruthenium(II)–copper(II) complex-based luminescent chemosensor, [Ru(bpy) 2(bpy-DPA)Cu] 4+ (bpy: 2,2′-bipyridine; bpy-DAP: 4-methyl-4′-[ N, N-bis(2-picolyl)amino-methylene]-2,2′-bipydine), has been designed and synthesized for the highly selective and sensitive recognition and detection of sulfide anions in 100% aqueous solutions. Owing to the high affinity of sulfide to Cu(II), the non-luminescent chemosensor can specifically and rapidly react with sulfide to yield the corresponding ruthenium(II) complex, [Ru(bpy) 2(bpy-DPA)] 2+, accompanied by the remarkable luminescence enhancement. The dose-dependent luminescence enhancement of the sensor shows a good linearity with a detection limit of 20.7 nM for sulfide anions. The novel luminescence sensor has a widely available pH range from 4.5 to 10 and an excellent response selectivity to sulfide only even in the presence of various other anions. Based on this chemosensor, a rapid, selective and sensitive luminescence method for the detection of sulfide anions in wastewater samples was established. The coefficient variations (CVs) of the method are less than 3.1%, and the recoveries are in the range of 90.9–108.5%.

Displacement method to develop highly sensitive and selective dual chemosensor towards sulfide anion

By utilizing a displacement method, a macrocyclic compound 1, could report the presence of sulfide anion, with the detection limit of 7.0 × 10(-7) mol/L; moreover, no interference was observed from other anions, including SO(3)(2-), HSO(3)(-), SO(4)(2-), ClO(4)(-), I(-), Br(-), Cl(-), F(-), IO(3)(-), HPO(4)(2-), PO(4)(3-), C(2)O(4)(2-), S(2)O(3)(2-), CO(3)(2-), AcO(-), CN(-) and P(2)O(7)(4-), making compound 1 a new, highly sensitive and selective sulfide anion chemosensor.

Redox chemistry of sulphate and uranium in a phosphogypsum tailings dump

The present study aims to assess the effect of redox conditions existing within the tailings dump on the stability of phosphogypsum (e.g. sulphate reduction) and uranium(VI). Phosphogypsum sampling and in-situ measurements were carried out at a coastal tailings dump in Vasiliko Cyprus, pH, E H and solubility experiments were performed in simulated laboratory systems and thermodynamic calculations using MINTEQA2. Generally, in the open tailings dump oxidizing conditions predominate stabilizing sulphur and uranium in their hexavalent oxidation states. On the other hand, after the application of a soil/vegetative cover and in the presence of natural organic matter, anoxic conditions prevail ( E H < −70 mV) resulting in S(VI) and U(VI) reduction to S(−II) and U(IV), respectively. Although, the sulphide anion can form very insoluble compounds with heavy metal ions (e.g. Cd(II), Pb(II) etc.) and U(IV) oxide has very low solubility, partial reduction of sulphate to sulphide within gypsum may affect the stability of phosphogypsum resulting in enhanced erosion of the material by rain- and seawater and washing out of contaminants in particulate/colloidal form.

La2Pb(SiS4)2

Crystals of La(2)Pb(SiS(4))(2), dilanthanum(III) lead(II) bis[tetrasulfidosilicate(IV)], were obtained from the La-Pb-Si-S system and structurally characterized using X-ray single-crystal diffraction. The La and Pb atoms are coordinated in bicapped trigonal prisms of S atoms, with the Si atoms in tetrahedra. An occupational disorder of the La and Pb centres was refined for one position in the structure. The bicapped trigonal prisms and tetrahedra share edges. A gap located 2.629 (1) A from the sulfide anions was found around the coordination polyhedra, which makes La(2)Pb(SiS(4))(2) a prospective material in crystal engineering. The Si and one S atom lie on a threefold axis.

Sulfide anion interaction with Cu(1 0 0) and Cu modified Au(1 0 0): An electrochemical STM study

AbstractWe describe the formation of thin copper sulfide semiconductor films under electrochemical conditions. In a first step we investigated the fundamental interaction of the Cu(1 0 0) surface with a sulfide anions containing electrolyte. Beside the classical p(2 × 2)‐S and c(2 × 6)‐S adlayer phases we found the formation of a closer packed “pseudo‐c(2 × 2)”‐S phase accompanied by an expansion of the topmost copper layer. For a further investigation of this “pseudo‐c(2 × 2)”‐S phase, we switched from the bulk Cu(1 0 0) electrode to a copper monolayer on a Au(1 0 0) electrode, which can be easily prepard using copper underpotential deposition. Since such a copper monolayer is pseudomorphic to the Au(1 0 0) surface and therefore expanded by 12.5% with respect to the bulk Cu(1 0 0)‐plane, exclusively a commensurate c(2 × 2)‐S structure is instantaneously formed and remains stable over a wide potential range.