Nanostructured shuriken-like BiVO4 with preferentially exposed {010} facets: preparation, formation mechanism, and enhanced photocatalytic performance.

Nanostructured shuriken-like monoclinic scheelite phase BiVO4 (mBiVO4) with preferentially exposed {010} facets was synthesized by a solvothermal process in a glycerol (Gly)/water mixed solvent using ethylenediamine tetraacetic acid disodium (EDTA) as the structure-directing agent. EDTA competes with Gly to control the kind and concentration of reaction species in the system, and thereby the preferential growth of mBiVO4 nanocrystals along the {010} facets as well as formation of a shuriken-like morphology can take place at the same time. The formation mechanism of products with different microstructures is proposed. The optimized mBiVO4 photocatalyst obtained using 0.4 mmol EDTA exhibited highest photocatalytic activity for methylene blue (MB) degradation, which could be attributed to the highest exposure degree of the active {010} facets, as well as the shuriken-like nanostructure, which enhanced the separation of photogenerated electrons and holes.

Hydrolysis of cellulose catalyzed by quaternary ammonium perrhenates in 1-allyl-3-methylimidazolium chloride.

Quaternary ammonium perrhenates were applied as catalyst to promote the hydrolysis of cellulose in 1-allyl-3-methylimidazolium chloride ([Amim]Cl). The quaternary ammonium perrhenates displayed good catalytic performance for cellulose hydrolysis. Water was also proven to be effective to promote cellulose hydrolysis. Accordingly, 97% of total reduced sugar (TRS) and 42% of glucose yields could be obtained under the condition of using 5mol% of tetramethyl ammonium perrhenate as catalyst, 70µL of water, ca. 0.6mmol of microcrystalline cellulose (MCC) and 2.0g of [Amim]Cl as solvent under microwave irradiation for 30min at 150°C (optimal conditions). The influence of quaternary ammonium cation on the efficiency of cellulose hydrolysis was examined based on different cation structures of perrhenates. The mechanism on perrhenate catalyzed cellulose hydrolysis is also discussed, whereas hydrogen bonding between ReO4 anion and hydroxyl groups of cellulose is assumed to be the key step for depolymerization of cellulose.

Solid-phase extraction based on a molecularly imprinted polymer for the selective determination of four benzophenones in tap and river water.

This work reports the preparation of molecularly imprinted polymer particles for the selective extraction and determination of four benzophenones from aqueous media. The polymer was prepared by using 4-vinylpridine as functional monomer, ethylene glycol dimethacrylate as cross-linker, acetonitrile as porogenic solvent and 2,2',4,4'-tetrehydroxybenzophenone as template. Good specific adsorption capacity (Qmax = 27.90 µmol/g) for 2,2',4,4'-tetrehydroxybenzophenone was obtained in the sorption experiment and good class selectivity for 2,2',4,4'-tetrehydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dehydroxy-4,4'-dimethoxybenzophenone was demonstrated by the chromatographic evaluation experiment. Factors affecting the extraction efficiency of the molecularly imprinted solid-phase extraction procedure were investigated systematically. An accurate and sensitive analytical method based on the molecularly imprinted solid-phase extraction coupled with high-performance liquid chromatography and diode array detection has been successfully developed for the simultaneous determination of four benzophenones from tap water and river water with method detection limits of 0.25-0.72 ng/mL. The recoveries of benzophenones for water samples at two spiking levels (500 and 5000 ng/mL for each benzophenone) were in the range of 86.9-103.3% with relative standard deviations (n = 3) below 9.2%.

Activation of hydrogen peroxide by ionic liquids: mechanistic studies and application in the epoxidation of olefins.

Imidazolium-based ionic liquids that contain perrhenate anions are very efficient reaction media for the epoxidation of olefins with H2O2 as an oxidant, thus affording cyclooctene in almost quantitative yields. The mechanism of this reaction does not follow the usual pathway through peroxo complexes, as is the case with long-known molecular transition-metal catalysts. By using in situ Raman, FTIR, and NMR spectroscopy and DFT calculations, we have shown that the formation of hydrogen bonds between the oxidant and perrhenate activates the oxidant, thereby leading to the transfer of an oxygen atom onto the olefin demonstrating the special features of an ionic liquid as a reaction environment. The influence of the imidazolium cation and the oxidant (aqueous H2O2, urea hydrogen peroxide, and tert-butyl hydrogen peroxide) on the efficiency of the epoxidation of cis-cyclooctene were examined. Other olefinic substrates were also used in this study and they exhibited good yields of the corresponding epoxides. This report shows the potential of using simple complexes or salts for the activation of hydrogen peroxide, owing to the interactions between the solvent medium and the active complex.

Contribution of tertiary amino groups to Re(VII) biosorption on modified corn stalk: competitiveness and regularity.

The effects of basic strength and steric hindrance of gels modified by dimethylamine, diethylamine, di-n-octylamine and di-2-ethylhexylamine, respectively, on rhenium (Re(VII)) adsorption capacity and selectivity were discussed. By comparing with the adsorption of other coexisting metals, such as Mo(VI), Cu(II), Pb(II), Fe(III), Zn(II), Mn(VII) and Ni(II), the gel modified by di-n-octylamine (DNOA-OCS) showed a high affinity for Re(VII) at higher hydrochloric acid concentration (C(H)(+)≥1.0 mol L(-1)), and the maximum adsorption capacity was 98.69 mg g(-1). This article not only described the adsorption behavior but also suggested isotherms, kinetics and thermodynamics of Re(VII) onto the DNOA-OCS gel in an aqueous medium using several models. Further study on adsorption of rhenium in a fixed-bed column packed with the DNOA-OCS gel under continuous and recirculating modes could confirm that the corn stalk gel modified by di-n-octylamine could be used as the adsorbent of Re(VII) from Mo-containing wastewater.

A new approach for rhenium(VII) recovery by using modified brown algae Laminaria japonica adsorbent.

Brown algae Laminaria japonica was chemically modified with sulfuric acid to obtain a crosslinked brown algae gel (CAS). The CAS gel showed a high affinity for Re(VII) comparing with other biomass gels, and the maximum adsorption capacity was evaluated as 37.20 mg g(-1) in case of pH 6, which could be explained by their different adsorption mechanisms. The adsorption equilibrium, kinetics and thermodynamic study for Re(VII) on the CAS gel was discussed in detail by the several models, such as Langmuir, Freundlich, Temkin and Dubinin-Radushkevich model for kinetics analysis, the pseudo first, the second-order, the Elovich and intraparticle diffusion equation for equilibrium analysis. Reutilization of the CAS gel was confirmed up to three adsorption-elution cycles in column-mode operation with no damage of gel, packed in the column. The result also provides a new approach for the recovery of Re(VII) from Re-containing wastewater by using the modified brown algae gel.

Physicochemical properties of air and water stable rhenium ionic liquids.

Air and water stable ionic liquids (ILs) based on catalytic functional metal rhenium, [C(n)mim][ReO(4)](n = 2,4,5,6)(1-alkyl-3-methylimidazolium perrhenate), are designed and synthesized. Their density and surface tension are measured in the temperature range of 293.15-343.15 ± 0.05 K. Some physical-chemical properties of the ILs have been calculated or estimated by the empirical methods. The ion parachor is put forward and calculated by two extrathermodynamic assumptions. According to the interstice model, the thermal expansion coefficient of ILs [C(n)mim][ReO(4)], α, are calculated and in comparison with experimental values, their magnitude order is in good agreement.

Detection of chlorogenic acid in honeysuckle using infrared-assisted extraction followed by capillary electrophoresis with UV detector.

In this study, a novel infrared-assisted extraction method coupled capillary electrophoresis (CE) is employed to determine chlorogenic acid from a traditional Chinese medicine (TCM), honeysuckle. The effects of pH and the concentration of the running buffer, separation voltage, injection time, IR irradiation time, and anhydrous ethanol in the extraction concentration were investigated. The optimal conditions were as follows: extraction time, 30 min; extraction solvent, 80% (v/v) ethanol in water solution; and 50 mmol/L borate buffer (pH 8.7) was used as the running buffer at a separation voltage of 16 kV. The samples were injected electrokinetically at 16 kV for 8 s. Good linearity (r(2) > 0.9996) was observed over the concentration ranges investigated, and the stability of the solutions was high. Recoveries of the chlorogenic acid were from 95.53% to 106.62%, and the relative standard deviation was below 4.1%. By using this novel IR-assisted extraction method, a higher extraction efficiency than those extracted with conventional heat-reflux extraction was found. The developed IR-assisted extraction method is simple, low-cost, and efficient, offering a great promise for the quick determination of active compounds in TCM. The results indicated that IR-assisted extraction followed by CE is a reliable method for quantitative analysis of active ingredient in TCM.

Investigation on the removal of Mo(VI) from Mo-Re containing wastewater by chemically modified persimmon residua.

Persimmon waste was chemically modified by crosslinking with concentrated sulfuric acid to obtain a novel kind of adsorption gel, which was termed as crosslinked persimmon tannin (CPT), hereinafter. The adsorption behaviors of Mo(VI) with other coexisting metal ions onto the CPT gel were investigated. The gel exhibited selectivity only for Mo(VI) ions evidenced by the high value of separation factor of molybdenum and rhenium (ß(Mo/Re)=164.37), and the adsorption mechanism of Mo(VI) as a multispecies was studied. The molybdenum adsorption behavior conforms to the Langmuir model with a remarkably high adsorption capacity of 0.56 mol/kg. A kinetic study for the adsorption of molybdenum at various temperatures confirmed that the endothermic adsorption process followed pseudo-second order kinetics. Moreover, its excellent adsorption properties and applicability for Mo(VI) were demonstrated by the removal and separation of Mo(VI) from different Mo-Re containing industrial wastewaters.

(N-salicylidene)aniline derived Schiff base complexes of methyltrioxorhenium(VII): ligand influence and catalytic performance.

Methyltrioxorhenium(VII) (MTO) readily forms 1:1 adducts with several N-(salicylidene)aniline derived Schiff bases. If the aromatic rings of the N-(salicylidene)aniline ligands display non-donating or electron withdrawing substituent groups, the resulting MTO adducts show good activities in olefin epoxidations. However, steric effects seem to play a major role, leading often to instable o- and m-Schiff base-MTO adducts, while p-substituted Schiff bases usually lead to more stable adducts. In catalysis, electron-withdrawing substituents on the aniline moiety lead to better catalysts than electron donating ones. The gap between good catalysts and instable or non-existing compounds, however, is small. The general tendency, however, that good donors on the Schiff base ligands lead to shorter Re-O(Schiff base) bridges and lower catalytic activity, while the opposite is true with acceptor ligands on the Schiff bases, seems to be quite clear.

[Determination of rhenium in raffinate and residue from synthesis of methyltrioxorhenium by ICP-AES].

Methyltrioxorhenium is a novel and efficient organometallic catalyst. It has exhibited amazingly high activities in a variety of organic reactions, and can form compounds with Lewis base. Thus, the improvement of its synthesis rate has become a pop topic all over the world. The content of rhenium in raffinate and residue from the synthesis of methyltrioxorhenium is an important standard for the evaluation of synthesis rate and a foundation for the optimization of synthesis condition. UV spectrophotometry is the standard technique for the determination of rhenium. However, this method presents several disadvantanges such as low sensitivity, high interferences, and hard handling. Inductive coupled plasma-atomic emission spectrometry has many advantages such as high precision, rapid analysis speed and good stability, and can determine multi-elements simultaneously. It is widely used in determination in every walk of life. An ICP-AES method for determination of the content of rhenium in raffinate and residue from the synthesis of methyltrioxorhenium was used. The working parameters were optimized. The detection limit was 0.01 mg x L(-1). RSD was in the range of 0.48%-1.12% and recoveries in the range from 97.2%-104% were obtained. The spectrum interference can be neglected. Compared with spectrophotometer, the proposed method was proved to be simple, rapid and accurate, and the result was satisfactory.

[Interaction of tributyltin (TBT) compound and bovine serum albumin (BSA)].

Tributyltin (TBT) compound is one of the main components of antifouling paint for boats and ships. The interaction of TBT compound and bovine serum albumin (BSA) was investigated by ultraviolet, fluorescence and circular dichroism (CD) spectra. The influences of concentration, acidity and organic solvent were also studied. The results showed that the interaction of TBT and BSA was dual, showing not only the hydrophobic actions of butyl groups but also the coordination action of tin cation with BSA molecule, which resulted in the exposures of aromatic amino acids residues of tryptophane and tyrosine in BSA molecule, the destruction of BSA secondary structure, the decrease in alpha-helix content, and the transformation of the conformation.

Investigation on the rapid degradation of congo red catalyzed by activated carbon powder under microwave irradiation.

Azo dyestuff-congo red in aqueous solution can be degraded rapidly under microwave irradiation in the presence of activated carbon powder. The results showed that the degradation ratio could reach 87.79% for 25 mL total volume with 50mg/L congo red and 2.0 g/L activated carbon powder under 1.5 min microwave irradiation. Furthermore, within the same irradiation time, congo red could be degraded fully by increasing addition amount (e.g. 3.6g/L) of activated carbon powder and the degradation ratio was up to 96.49%. Otherwise, with the same addition amount, congo red also could be degraded completely by prolonging irradiation time (e.g. 2.5 min) and the degradation ratio was up to 97.88%. In addition, the influences of microwave irradiation time, initial concentration of congo red, addition amount and used times of activated carbon powder as well as solution acidity on the degradation were discussed in details adopting UV-vis spectra, FT-IR spectra, ion chromatography, high phase liquid chromatography (HPLC) and TOC analysis technologies. Here, the method using activated carbon powder as catalyst under microwave irradiation shows many advantages including high degradation ratios, short reaction time, low costs, no intermediates and no secondary pollution. Therefore, it may be fit for dealing with various azo dyestuff wastewaters on a large scale.

MTO Schiff-base complexes: synthesis, structures and catalytic applications in olefin epoxidation.

Several Schiff-base ligands readily form complexes with methyltrioxorhenium(VII) (MTO) by undergoing a hydrogen transfer from a ligand-bound OH group to a ligand N atom. The resulting complexes are stable at room temperature and can be handled and stored in air without problems. Due to the steric demands of the ligands they display distorted trigonal-bipyramidal structures in the solid state, as shown by X-ray crystallography, with the O(-) moiety binding to the Lewis acidic Re atom and the Re-bound methyl group being located either in cis or trans position to the Schiff base. In solution, however, the steric differences seem not to be maintained, as can be deduced from (17)O NMR spectroscopy. Furthermore, the Schiff-base ligands exchange with donor ligands. Nevertheless, the catalytic behaviour is influenced significantly by the Schiff bases coordinated to the MTO moiety, which lead either to high selectivities and good activities or to catalyst decomposition. A large excess of ligand, in contrast to the observations with aromatic N-donor ligands, is detrimental to the catalytic performance as it leads to catalyst decomposition.

[Determination of trace selenium in edible fungi with graphite furnace atomic absorption spectroscopy].

In the present article, samples were digested by a quartz high-pressure digestion pot, reducing the loss of selenium in digestion. The content of selenium in edible fungi was determined by using graphite furnace atomic absorption spectroscopy, and the results showed that when the content of selenium in edible fungi was determined by using 1% Ni(NO3)2 as a matrix modifier, ashing temperature of 500 degreed C, and atomization temperature of 2 500 degrees C, and rectifying background by deuterium light, the recovery was in the range of 92.1%-115.5%, the relative standard deviation of the method was 1.28%, and the limit of detection was 15.8 microg x L(-1). The method was suitable for the determination of trace selenium in edible fungi with the advantages of being simple, rapid, sensitive, stable and accurate etc., and the results were satisfactory.

[Separation and determination of selenium polysaccharide in enriched-Se cordyceps militaris].

In the present paper, the water soluble selenium polysaccharide was extracted, and isolated and purified preliminarily. The traditional method was used to extract selenium polysaccharide, which was extracted by water and sank by ethanol. The work also focused on the determination of the experiment conditions, optimizing the experiment conditions such as proportion of extract solution, extract temperature, extract times, proportion of ethanol, and standing time. The recovery of selenium polysaccharide under these conditions is 5.76%. Polysaccharide content in the powder is 46.6%, and selenium content is 92.3 mg x kg(-1).

[Study on the method of using ICP-MS to determine Se in the edible fungi].

The sample was digested by the quartzose digestion pot at high-pressure under relatively low temperature, reducing the loss of Se during the digestion process. Study on the method of using ICP-MS to determine Se in the edible fungi shows that it exhibits positive correlation between the concentration of sample and integration time, and the response value. When the concentration of Se in the sample is higher than 50 microg x L(-1), the integration time can be 0.1 s; or it can be 2.0 s when the concentration of Se is lower than 5 microg L(-1). The standard curve was accomplished for 1.0-500 microg x L(-1) when determining the content of Se in the edible fungi. The recoveries are in the range of 99.96%-102.7%. This method has advantages of simplicity, speediness, delicacy, high stability, high accuracy, etc. It is suitable for the determination of trace Se in the edible fungi.

[Chemical forms of cadmium in industrial contaminated soil and its phytoremediation].

The study showed that the adsorbed cadmium in soil could be dissolved in water, and the lower the soil pH, the higher and stronger the dissolving rate and mobility, and the more uptake by crops. The water-soluble, exchangeable and complexed cadmium contents in the contaminated soil were lower when the soil was chemically neutral, with the values being 0.68%, 12.70% and 12.40%, respectively, while the insoluble (granulated) cadmium content was 74.40%. Radish caudex in the contaminated soil could absorb cadmium, and be considered as the hyperaccumulator of soil cadmium.

Determination of active ingredients of Ilex Purpurea Hassk and its medicinal preparations by capillary electrophoresis with electrochemical detection.

A method based on capillary electrophoresis with electrochemical detection has been developed for the separation and determination of isovanillic acid, gentisic acid, kaempferol, quercetin, caffeic acid and protocatechuic acid in Ilex Purpurea Hassk and its medicinal preparations for the first time. The effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time on CE-ED were investigated. Under the optimum conditions, the analytes could be separated in a 50 mmoll(-1) borate buffer (pH 9.0) within 21 min. A 300 microm diameter carbon disk electrode has a good response at +0.95 V (versus SCE) for all analytes. The response was linear over three orders of magnitude with detection limits (S/N=3) ranging from 3 x 10(-8) to 2 x 10(-7)gml(-1) for the analytes. The method has been successfully applied to the analysis of real sample, with satisfactory results.

[Determination of active species of heavy metals in sewage sludge by ICP-MS].

Sewage sludge samples for the research from the sewage disposal plants of the north, Mantang River and Xiannu River in Shenyang were extracted and separated by H2O, HAc and organic solvents of different polarities. The active species of Cd, Pb, Cu, Zn and Cr existing in the sewage sludge were determined by ICP-MS, and the regularity and influential factors were studied under the alternation of environmental conditions. The results showed that the content of acid-soluble heavy metals was more than that of water-soluble ones, and both had coincident regularity under the alternation of time and temperature; the content of the organic solvents was positively correlated to the solvent polarity. The acid-soluble heavy metals were more active during the course of transforming, and the activity sequence of heavy metals in the same species was: water-soluble Zn>Cu>Cd> Pb>Cr, acid-soluble Cd>Cr>Cu>Zn>Pb, and organic-soluble Pb>Cd>Cr>Cu>Zn.