Killing of Invasive Species of Ship’s Ballast Water in 20t/h System Using Hydroxyl Radicals

A pilot-scale experiment of 20t/h for the treatment of ships ballast water was done in this paper. With the method of strong ionization discharge of dielectric barrier, O₂ in air and H₂O at gas state are ionized and dissociated into large numbers of OH radicals, and then dissolved into a part of ballast water to form dissolved OH with the concentration of 24.3 mg/L. When the dissolved OH concentration is 0.63 mg/L, the kill efficiencies of bacteria, mono-algae, protozoan reached 100% within 2.67 s. The contents of chl-a, chl-b, chl-c and carotenoid were decreased to 35–64% within 8.0 s and not be tested after 5 min. At the same time, the ballast water quality was greatly improved. Therefore, the treatment of ships ballast water using OH radicals is a kind of advanced oxidation technology, which is considered as zero pollution, zero emission and zero residual in the process of the production, of OH radicals and the treatment of ballast water.Key Project of National Foundation Research from Science and Technology Ministry of China, (2002CCC00900). Key and General Projects of National Natural Science Foundation of China (NSFC: 60031001, 60371035).     

Theoretical calculations of95Mo-NMR chemical shifts for compounds [MoO4−n S n ]2−

Summary Theoretical calculation of⁹⁵Mo-NMR chemical shifts for [MoO_4–n S _n ]^2– (n=0–4) compounds is reported here for the first time on the basis of Fenske-Hall method and Sum-Over-State (SOS) perturbation theory. A systematic decrease in shielding of⁹⁵Mo nuclei with increase of number of sulfur in [MoO_4–n S _n ]^2–, which is observed experimentally, can be reasonably explained by our calculation. A good linear relationship between chemical shifts of calculation and experiment is obtained. The electronic structure and bonding in these compounds are also discussed.Supported by Nature Science Foundation of China     

Nanosilver resonance scattering spectral method for determination of hydroxyl radical and its application

Silver nanoparticles were prepared under a microwave high-pressure condition using citric acid sodium as a reducer while the excess citrate was removed under high speed centrifugation. There is a resonance scattering (RS) peak at 470 nm for silver nanoparticles. In a pH 4.0 HAc-NaAc buffer solution, hydroxyl radicals from the Fenton reaction can oxidize silver nanoparticles to Ag , resulting in the RS intensity decreasing. The decreased RS intensity at 470 nm (△I 470 nm) is linear with respect to the concentration of H2O2 (C) in the range of 0.27-7.56 μmol/L with a detection limit of 0.23 μmol/L. Its regression equation is △I 470 nm = 24.3 C 13.8 with a correlation coefficient of 0.9959. This method was applied to screening the antioxidants with satisfactory results.     

[trans-en2Os (ŋ-H2)]2 + as an1H NMR probe for the coordination of some anticancer metal complexes to deoxyguanotide

The molecular hydrogen complex of osmium, [trans-en₂Os (ŋ-H₂)]²⁺ (en, entlylendediamine) is a new¹H NMR recognition probe for biomolecules. By using this probe, the coordination between deoxyguanylic acid (dGMP) and four metal anticancer complexes, titanocene dichloride, (C₂H₅)₂SnCl₂(phen). (C₂H₅)₂SnCl₂ and cisplatin are studied in D₂O under the condition near the physiological one. The results show that the former three complexes mainly and strongly coordinate with the phosphate oxygen of dGMP, while cisplatin mainly coordinates with N(7) of dGMP. Project supported by the National Natural Science Foundation of China, the Natural Science Foundation of Shanxi Province and the Youth Science Foundation of Shanxi Province.     

Long-wave light absorption and photochemical decomposition of peroxide radicals

Photochemical decomposition of alkylperoxide radicals in glassy matrices at 77 K was experimentally studied. Irradiation with light up to 405 nm leads to the photodecomposition of peroxide radicals. The quantum yield of the reaction was estimated to be 10^–2. A light-induced angular dependence of the ESR spectra of peroxide radicals resulting from photoselection was detected. The photoselection found proves that the photodecomposition is induced by the absorption of light in the inherent absorption band of RO₂.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1074–1077, June, 1995.The work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 95-03-08505) and the International Science Foundation (Grants NBU 000 and NBU 300).     

The N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine and its phenoxyl and aminyl radicals

The N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine Ph—NH—C₆H₄—OH (D _NH= 353.4, D _OH=339.3 kJ mol^–1) and its semiquinone radicals D _NH(Ph—NH—C₆H₄—O^·) = 273.6, D _OH(Ph—N^·—C₆H₄—OH) = 259.5 kJ mol^–1 were first estimated using the parabolic model and experimental data (rate constants) on two elementary reactions with participation of N-phenyl-1,4-benzoquinonemonoimine (2). One of the reactions, namely, that of 2 with aromatic amines, was studied in this work using a specially developed method.     

Mechanism of OH radical-induced oxidation of <Emphasis Type="Italic">p</Emphasis>-cresol to <Emphasis Type="Italic">p</Emphasis>-methylphenoxyl radical

The OH radical-induced oxidation of p-cresol to p-methylphenoxyl radical was studied in aqueous solution in a wide pH range by means of pulse radiolysis combined with optical spectroscopy. OH-adduct cyclohexadienyl type radicals were identified as intermediates of the reaction. In the acidic pH range the first-order rate coefficient of phenoxyl radical formation was found linearly dependent on the H₃O⁺ concentration yielding a bimolecular rate coefficient of 1.8 × 10⁸ mol^–1 dm³ s^–1. In the alkaline range a linear dependence was found on the OH^– concentration with rate coefficient of 4.9 × 10¹⁰ mol^–1 dm³ s^–1. These findings were interpreted in terms of acid-base catalysis of the H₂O elimination from the OH-adduct. With the time resolution applied, 30 ns, the radical cation p-CH₃C₆H₄OH^+. was not observed as intermediate.     

Effects of hydroxyl radicals and oxygen species on the 4-chlorophenol degradation by photoelectrocatalytic reactions with TiO2-film electrodes

The supported nano-TiO₂ electrode was prepared by sol–gel and hydrothermal method, and the photoelectrocatalytic degradation of 4-chlorophenol (4-CP) under UV irradiation has been investigated to reveal the roles of hydroxyl radicals and dissolved oxygen species for TiO₂-assisted photocatalytic reactions. The degradation kinetics, the formation and decay of intermediates, the isotopic tracer experiments with H₂O¹⁸, the removal yield of total organic carbon and the formation of active radical species in the presence of oxygen or not were examined by HPLC, GC–MS, TOC and spin-trap ESR spectrometry. It was found that most of OH radicals in the primary hydroxylated intermediates derived from the oxidation of adsorbed H₂O or HO⁻ by photo-holes in the electrochemically assisted TiO₂ photocatalytic system. It also indicates that the enhancement in the separation efficiency of photogenerated charges by applying a positive bias (+0.5 V vs SCE) has little role in the following decomposition and mineralization of these hydroxylated intermediates in the absence of oxygen. According to above experimental results, the pathway of 4-CP photocatalytic degradation was deduced initially. Due to the combined effect of OH radicals and dissolved oxygen species, the hydroxylated 4-chlorphenol, via cis, cis-3-chloromuconic acid, was decomposed into low molecular weight acid and CO₂.     

Chromium(III) Hydroxide Solubility in The Aqueous Na+-OH?-H2PO?4-HPO2?4-PO3?4-H2O System: A Thermodynamic Model

Chromium(III)-phosphate reactions are expected to be important in managing high-level radioactive wastes stored in tanks at many DOE sites. Extensive studies on the solubility of amorphous Cr(III) solids in a wide range of pH (2.8–14) and phosphate concentrations (10^–4 to 1.0 m) at room temperature (22±2)°C were carried out to obtain reliable thermodynamic data for important Cr(III)-phosphate reactions. A combination of techniques (XRD, XANES, EXAFS, Raman spectroscopy, total chemical composition, and thermodynamic analyses of solubility data) was used to characterize solid and aqueous species. Contrary to the data recently reported in the literature,⁽¹⁾ only a limited number of aqueous species [Cr(OH)₃H₂PO^–₄, Cr(OH)₃(H₂PO₄)^2–₂), and Cr(OH)₃HPO^2–₄] with up to about four orders of magnitude lower values for the formation constants of these species are required to explain Cr(III)-phosphate reactions in a wide range of pH and phosphate concentrations. The log K^o values of reactions involving these species [Cr(OH)₃(aq)+H₂PO^–₄&#x21CC;Cr(OH)₃H₂PO^–₄; Cr(OH)₃(aq)+2H₂PO^–₄&#x21CC;Cr(OH)₃(H₂PO₄)^2–₂; Cr(OH)₃(aq)+HPO^2–₄&#x21CC;Cr(OH)₃HPO^2–₄] were found to be 2.78±0.3, 3.48±0.3, and 1.97±0.3, respectively.     

Kinetics and mechanism of metal ion catalysis. Part III. Osmium(VIII) catalysed oxidation of m-hydroxybenzaldehyde by Fe(CN)6 3− in alkaline medium

Os^VIII-catalysed oxidation of m-hydroxybenzaldehyde by alkaline Fe(CN)₆ ^3– has been studied in the 0.01–0.05 M [OH^–] range. Higher [OH^–] concentrations were not possible as the substrate turned yellow at [OH^–] > 0.05 M. The very low solubility of the substrate in H₂O restricted the kinetic study to [OH^–] < 0.01 M. A mechanism, consistent with the results is proposed.     

Double proton shifts in associates of formic acid with CH4, NH3, H2O,CH3F,NH2F,HOF, and HF molecules

The mechanisms of double synchronous proton transfer in associates of formic acid with solvent molecules of the HC(O)OHX (X = CH₄, NH₃, H₂O, or HF) and HC(O)OHFHY (Y = CH₃F, NH₂F, HOF, F₂, or HF) types have been studied by anab initio (SCF/3G) method. The calculated activation barriers of the reactions are 78.52, 17.72, 9.91, and 7.06 kcal mol^–1 in the former case and 120.1, 259.4, 228.7, 182.8, and 0.35 kcal mol^–1 in the latter case. In the latter case, simultaneously with the double transfer of protons, migration of two fluorine atoms along the chain of the associate occurs.Dedicated to Academician of the RAS N. S. Zefirov (on his 60th birthday).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1690–1700, September, 1995.The present work was carried out with financial support from the Russian Foundation for Basic Research (Project Nos. 93-03-4972 and 93-03-18692) and the International Science Foundation (Grant ISF RNJ 000).     

Crown-ether styryl dyes

The surface enhanced Raman scattering (SERS) spectra of styryl dyes containing a crown-ether group and a heteroaromatic residue with sulfoalkyl (1a) or alkyl (1b)N-substituent and of their complexes with Mg²⁺ cations were recorded in the 10^–4–10^–8 mol L^–1 concentration range. A model for the interaction of compoundsla,b with a silver surface during their adsorption on an electrochemically treated electrode was suggested. Fastcis-trans relaxation of the adsorbed molecules1a,b and complexes (1a,b)Mg²⁺ was found. It was shown that at [1a] = 10^–5 mol L^–1 and moderate molar ratios (C _Mg/[1a] = 3/1 to 9/1) in acetonitrile solutions, (trans-1a)Mg²⁺ complexes are joined into head-to-tail type dimers. An excess of Mg²⁺ cations (C_Mg/[1a] > 100) leads to dissociation of the dimers yielding (trans-1a)(Mg²⁺)₂ complexes. The formation of dimers from complexes (trans-1a)Mg²⁺ is accompanied by a substantial distortion of the planar structure oftrans-1a. This may be an important factor influencing the efficiency of photocycloaddition involving dimers of (trans-1a)Mg²⁺.For part 15, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2429–2436, December, 1995.The work was carried out with financial support of the Russian Foundation for Basic Research (Project No. 94-03-08760) and, to some extent, of INTAS (Grant No. 93-1829) and of the International Science Foundation (Grant No. MHAOOO).     

Untersuchungen an Kristallhydraten anorganischer Salze, 8. Mitt. Interpretation der Schwingungsspektren vonM(BF4)2·6H2O fürM=Fe2+, Co2+, Ni2+

The infrared and Raman spectra were recorded in the range 4000–160 cm^–1 forM(BF₄)₂·6 H₂O whereM=Fe²⁺, Co²⁺, Ni²⁺. The spectroscopic data support the X-ray structural data in showing that in the crystal hydrates studied two kinds of hydrogen bonds are present: H₂O...H₂O and OH₂... F₄B^–. The energies and molecular force constants (f _OH and fH₂O) andr _OH for OH₂...F₄B^– were calculated for the three crystal hydrates. It was found that the bond OH₂... F₄B^– is comparatively weak, with mean energy 3.7–3.3 kcal/mol. Two types of water molecule with different structures are existing as the first are participating in H₂O...H–O–H...F₄B^– and the second in BF₄ ^–...H–O–H...F₄B^–.     

Kinetics and mechanisms of oxidation by metal ions. Part XIII. Osmium(VIII)-catalysed oxidation of cycloalkanols by alkaline hexacyanoferrate(III)

Summary The kinetics of OsO₄-catalysed oxidation of cyclopentanol, cyclohexanol and cyclooctanol by alkaline hexacyanoferrate(III) have been studied at low [OH^–] so that the equilibrium between alcohol and alkoxide ion is not unduly shifted towards the latter. The reaction shows a first-order dependence in [OH^–]. The order of the reaction with respect to cycloalcohol is fractional, indicating the formation of an intermediate complex with Os^VIII since the order with respect to hexacyanoferrate(III) ion is zero. The order with respect to Os^VIII may be expressed by the equation k_obs=a+b[Os^VIII]. The analysis of the rate data indicates a significant degree of complex formation between [OsO₃(OH)₃]^– and ROH. It was found that the bimolecular rate constant k for the redox reaction between complex and OH^–k₁, the forward rate constant for the formation of alkoxide ion. The activation parameters of these rate constants are reported.     

Hydroxyl mechanism of the antimalarial effect of artemisinin and its analogs

Kinetic schemes for the intramolecular oxidation of four artemisinin analogs, which are used as drugs against malaria, were developed. Each stage of the kinetic scheme is characterized by the enthalpy, activation energy, and rate constant calculated using the model of intersecting parabolas. The competition of mono- and bimolecular radical reactions was taken into account when developing the schemes. The hydroperoxide groups are formed as a result of the intramolecular oxidation of these compounds and generate free radicals in the reaction with Fe^II. Among these free radicals, hydroxyl radicals play the key role, since their yield (n _OH) correlates with the antimalarial activity of the peroxide compound. The efficiency of the drug (index IC₅₀) exponentially depends on n _OH and is expressed by the formula IC₅₀(Artemisinin)/IC₅₀(Compound) = 1.54·10⁻⁶exp(3.9n _OH). The elementary reactions resulting in the generation of hydroxyl radicals are considered. It is supposed that DNA of a malaria parasite is the main biological target for hydroxyl radicals.     

Synthesis, spectroscopic, structural and theoretical characterization of hydrogensquarate and mononuclear Au(III)-complex of dipeptide phenylalanyltyrosine

The mononuclear Au(III)-complex ([Au(C₁₈H₁₈N₂O₄)Cl]) and hydrogensquarate ([C₂₂H₂₁N₂O₈]) of dipeptide phenylalanyltyrosine (H–Phe–Tyr–OH) have been synthezised, characterized spectroscopically and structurally by means of solid-state linear-polarized IR-spectroscopy, ¹H- and ¹³C-NMR, ESI-MS, HPLC-MS–MS, FAB-MS, TGS and DSC methods. The structure of the Au(III)-complex has been predicted theoretically by DFT calculations. The dipeptide coordinated in a tridentate manner via –NH₂, –COO⁻ and N⁻-groups. One Cl⁻ ion is attached to the metal centre as a terminal ligand, yielding a planar AuN₂OCl chromophor. The hydrogensquarate consists in positive charged dipeptide moiety and negative one hydrogensquarate (HSq⁻) anion stabilizing by strong intermolecular hydrogen bonds.     

Direct electrochemistry and enzymatic activity of hemoglobin in positively charged colloid Au nanoparticles and hemoglobin layer-by-layer self-assembly films

Alternate adsorption of positively charged colloid-Au nanoparticles (nano-Au⊕) and negatively charged hemoglobin (Hb) on L-cysteine (L-cys) modified gold electrode resulted in the assembly of {Hb/nano-Au⊕}n layer-by-layer films/L-cys modified gold electrode. The nano-Au⊕ was characterized by transmission electron micrograph (TEM) and microelectrophoresis. The modified electrode interface morphology was characterized by electrochemical impedance spectroscopy (EIS), atomic force mi- croscopy (AFM), cyclic voltammograms (CV) and chronoamperometry. Direct electron transfer between hemoglobin and gold electrodes was studied, and the apparent Michaelis-Menten constant ( km app) of the modified electrode was evaluated to be 0.10 mmol·L?1. Moreover, the higher activity of proteins in the nano-Au⊕ films could be retained compared with the electropolymerization membrane, since the pro- teins in nano-Au⊕ films retained their near-native structure. Direct electron transfer between hemoglo- bin and electrode and electrochemically catalyzed reduction of hydrogen peroxide on a modified elec- trode was studied, and the linear range was from 2.1×10-8 to 1.2 ×10?3 mol·L-1 (r = 0.994) with a detection limit of 1.1×10-8 mol·L-1 H2O2.     

Resonance scattering spectral detection of ultratrace IgG using immunonanogold-HAuCl<Subscript>4</Subscript>-NH<Subscript>2</Subscript>OH catalytic reaction

Nanogold particles of 10 nm were used to label goat anti-human IgG (GIgG) to obtain nanogold-labeled GIgG (AuGIgG). In a citrate-HCI buffer solution of pH 2.27, AuGIgG showed a strong catalytic effect on the reaction between HAuCl₄ and NH₂OH to form big gold particles that exhibited a resonance scattering (RS) peak at 796 nm. Under the chosen conditions, AuGIgG combined with IgG to form immunocomplex AuGIgG-IgG that can be removed by centrifuging at 16000 r/min. AuGIgG in the centrifuging solution also showed catalytic effect on the reaction. On those grounds, an immunonanogold catalytic RS assay for IgG was designed. With addition of IgG, the amount of AuGIgG in the centrifuging solution decreased; the RS intensity at 796 nm (I _{796 nm}) decreased linearly. The decreased intensity ΔI _{796 nm} was linear with respect to the IgG concentration in the range of 0.08–16.0 ng · mL⁻¹ with a detection limit of 0.02 ng · mL⁻¹. This assay was applied to analysis of IgG in sera with satisfactory sensitivity, selectivity and rapidity. Supported by the National Natural Science Foundation of China (Grant No. 20667001), Natural Science Foundation of Guangxi Province (Grant No. 0728213), and the Foundation of New Century Ten-Hundred-Thousand Talents of Guangxi Province     

Characterization of Silicate Complexes in Aqueous Sodium Sulfate Solutions by FAB-MS

When the sodium ion (Na⁺) concentration is increased above 0.5 mol-dm⁻³ (M), the concentrations of dissolved silica in aqueous sodium chloride (NaCl) and sodium nitrate (NaNO₃) solutions decrease because of the salting out effect. On the other hand, the concentration of the dissolved silica in aqueous sodium sulfate (Na₂SO₄) solutions increases monotonously as the concentration of Na⁺ is increased above 0.5 M. The purpose of this study is to determine the reasons why the salting-out effect is not observed in Na₂SO₄ solutions. FAB-MS (Fast Atom Bombardment Mass Spectrometry) was used to sample directly the silica species dissolved in aqueous Na₂SO₄, NaCl, and NaNO₃ solutions. In the FAB-MS spectra of these solutions, the peak intensity ratios of the linear tetramer to the cyclic tetramer largely increased for Na⁺ concentrations between (0.1 and 1) M. This shows that some characteristics of the Na₂SO₄ solutions are similar to those of the NaCl and NaNO₃ solutions. In Na₂SO₄ solutions, however, when the concentration of Na⁺ is higher than 1 M, the peak intensity of the dimer is much higher than those of the other silicate complexes. In Na₂SO₄ solutions, the SO₄²⁻ ion undergoes partial hydrolysis to form HSO⁻₄ and OH⁻ is produced. In particular, in the range where the concentration of SO₄²⁻ is high, the pH of the solution increases slightly. This higher pH yields more dimers from the hydrolysis of silicate complexes. This increase in dimer production agrees with the observation that silica dissolves in sodium hydroxide (NaOH) solutions mainly as a dimer when the concentration of NaOH is less than 0.1 M. In Na₂SO₄ solutions at high concentrations, a salting-out effect is not observed for silica. This is due to the increase in the concentration of OH⁻, which accelerates the hydrolysis of silica and results in dimer formation.     

Removal of SO2 from Gas Streams by Oxidation using Plasma-Generated Hydroxyl Radicals

The key problem for the removal of SO₂ by electrical discharge methods is how to obtain the hydroxyl radicals at high concentration and large production rates. With the micro-gap discharge method, O₂ and H₂O in simulated gas streams (N₂/O₂/H₂O/SO₂) are ionized into a large number of OH^. radicals to oxidize SO₂ into SO₃ which reacts with H₂O forming H₂SO₄ droplets at 120 °C in the absence of any catalyst or absorbent. The droplets are captured with an electrostatic precipitator. As a result, conversion of SO₂ to primarily H₂SO₄ is limited by the generation of OH^. radicals. By increasing the reduced field and concentrations of O₂ and H₂O, the amount of OH^. radicals increase resulting in more removal of SO₂ from gas streams. The removal efficiency of SO₂ reaches 100% when the residence time is only 0.74 s. Therefore, a new gas-phase oxidation method for removal of SO₂ without NH₃ additive is found.