Significance of RuO2 modified SCR catalyst for elemental mercury oxidation in coal-fired flue gas

Catalytic conversion of elemental mercury (Hg(0)) to its oxidized form has been considered as an effective way to enhance mercury removal from coal-fired power plants. In order to make good use of the existing selective catalytic reduction of NO(x) (SCR) catalysts as a cobenefit of Hg(0) conversion at lower level HCl in flue gas, various catalysts supported on titanium dioxide (TiO(2)) and commercial SCR catalysts were investigated at various cases. Among the tested catalysts, ruthenium oxides (RuO(2)) not only showed rather high catalytic activity on Hg(0) oxidation by itself, but also appeared to be well cooperative with the commercial SCR catalyst for Hg(0) conversion. In addition, the modified SCR catalyst with RuO(2) displayed an excellent tolerance to SO(2) and ammonia without any distinct negative effects on NO(x) reduction and SO(2) conversion. The demanded HCl concentration for Hg(0) oxidation can be reduced dramatically, and Hg(0) oxidation efficiency over RuO(2) doped SCR catalyst was over 90% even at about 5 ppm HCl in the simulated gases. Ru modified SCR catalyst shows a promising prospect for the cobenefit of mercury emission control.     

TiO2-photocatalyzed As(III) oxidation in a fixed-bed, flow-through reactor

Compliance with the U.S. drinking water standard for arsenic (As) of 10 microg L(-1) is required in January 2006. This will necessitate implementation of treatment technologies for As removal by thousands of water suppliers. Although a variety of such technologies is available, most require preoxidation of As(III) to As(V) for efficient performance. Previous batch studies with illuminated TiO2 slurries have demonstrated that TiO2-photocatalyzed AS(III) oxidation occurs rapidly. This study examined reaction efficiency in a flow-through, fixed-bed reactor that provides a better model for treatment in practice. Glass beads were coated with mixed P25/sol gel TiO2 and employed in an upflow reactor irradiated from above. The reactor residence time, influent As(III) concentration, number of TiO2 coatings on the beads, solution matrix, and light source were varied to characterize this reaction and determine its feasibility for water treatment. Repeated usage of the same beads in multiple experiments or extended use was found to affect effluent As(V) concentrations but not the steady-state effluent As(III) concentration, which suggests that As(III) oxidation at the TiO2 surface undergoes dynamic sorption equilibration. Catalyst poisoning was not observed either from As(V) or from competitively adsorbing anions, although the higher steady-state effluent As(III) concentrations in synthetic groundwater compared to 5 mM NaNO3 indicated that competitive sorbates in the matrix partially hinder the reaction. A reactive transport model with rate constants proportional to incident light at each bead layer fit the experimental data well despite simplifying assumptions. TiO2-photocatalyzed oxidation of As(III) was also effective under natural sunlight. Limitations to the efficiency of As(III) oxidation in the fixed-bed reactor were attributable to constraints of the reactor geometry, which could be overcome by improved design. The fixed-bed TiO2 reactor offers an environmentally benign method for As(III) oxidation.     

Role of moisture in adsorption, photocatalytic oxidation, and reemission of elemental mercury on a SiO2-TiO2 nanocomposite

A novel silica-titania (SiO2-TiO2) nanocomposite has been developed to effectively capture elemental mercury (Hg0) under UV irradiation. Moisture has been reported to have an important impact on this nanocomposite's performance. In this work, the role of moisture on Hg0 removal and reemission as well as the corresponding mechanisms was investigated. Hg0 removal experiments were carried out in a fixed-bed reactor at 65 degrees C using air as the carrier gas. Without UV irradiation, Hg0 adsorption was found to be insignificant, but it could be enhanced by the photocatalytic oxidation product, mercuric oxide (HgO), possibly due to the high affinity between HgO and Hg0. Under dry conditions 95% of Hg0 can be removed; however, increased humidity levels remarkably suppress both Hg0 adsorption and photocatalytic oxidation. Introducing water vapor can also result in significant reemission of captured Hg0 from the nanocomposite, which may be ascribed to the repellant effect of water vapor adsorbed on the superhydrophilic TiO2 surface. Exposure to UV light was found either to prohibit Hg0 reemission when photocatalytic oxidation of reemitted Hg0 prevailed or to promote Hg0 reemission when photocatalytic reduction of HgO to Hg0 dominated later on. The results indicate that minimization of Hg0 reemission can be achieved by appropriate application of UV irradiation.     

介孔材料选择性降低卷烟烟气中苯并(a)芘的研究

本文根据介孔材料择形催化的原理,研制出了可选择性降害且适合于烟草工业应用的介孔材料。在降低卷烟烟气苯并(a)芘的试验中,考察了M48介孔材料和金属元素掺杂的MeM48介孔材料与卷烟烟气作用效果,发现在基本上不改变卷烟风格的基础上,MeM48和M48均可以选择性降低卷烟烟气中的苯并(a)芘,且降低率明显高于文献报道值;同时还发现无论将材料介入到卷烟滤嘴中还是烟丝中,MeM48介孔材料降低苯并(a)芘的效果明显优于M48材料。      

Alkali metal poisoning of a CeO2-WO3 catalyst used in the selective catalytic reduction of NOx with NH3: an experimental and theoretical study

The alkali metal-induced deactivation of a novel CeO(2)-WO(3) (CeW) catalyst used for selective catalytic reduction (SCR) was investigated. The CeW catalyst could resist greater amounts of alkali metals than V(2)O(5)-WO(3)/TiO(2). At the same molar concentration, the K-poisoned catalyst exhibited a greater loss in activity compared with the Na-poisoned catalyst below 200 °C. A combination of experimental and theoretical methods, including NH(3)-TPD, DRIFTS, H(2)-TPR, and density functional theory (DFT) calculations, were used to elucidate the mechanism of the alkali metal deactivation of the CeW catalyst in SCR reaction. Experiments results indicated that decreases in the reduction activity and the quantity of Br?nsted acid sites rather than the acid strength were responsible for the catalyst deactivation. The DFT calculations revealed that Na and K could easily adsorb on the CeW (110) surface and that the surface oxygen could migrate to cover the active tungsten, and then inhibit the SCR of NO(x) with ammonia. Hot water washing is a convenient and effective method to regenerate alkali metal-poisoned CeW catalysts, and the catalytic activity could be recovered 90% of the fresh catalyst.     

Coadsorption of arsenic(III) and arsenic(V) onto hydrous ferric oxide: effects on abiotic oxidation of arsenic(III), extraction efficiency, and model accuracy

Single solute adsorption and coadsorption of As(III) and As(V) onto hydrous ferric oxide (HFO), oxidation of As(III), and extraction efficiencies were measured in 0.2 atm O2. Oxidation was negligible for single-adsorbate experiments, but significant oxidation was observed in the presence of As(V) and HFO. Single-adsorbate As(III) or As(V) were incompletely extracted (0.5 M NaOH for 20 min), but all As was recovered in coadsorbate experiments. Single-adsorbate data were well-simulated using published surface complexation models, but those models (calibrated for single-adsorbate results) provided poor fits for coadsorbate experiments. An amended model accurately simulated single- and coadsorbate results. Model predictions of significant change in As(III) surface complex speciation in coadsorbate experiments was confirmed using zeta potential measurements. Our results demonstrate that mobility of arsenic in groundwater and removal in engineered treatment systems are more complicated when both As(III) and As(V) are present than anticipated based on single-adsorbate experimental results.     

Prediction of water activity, a(w), in cook-soak equilibrated intermediate moisture meats

The relationship between the moisture content and water activity, a(w), of several meat samples adjusted to intermediate moisture water activities by cook-soak equilibration in glycerol solutions containing 9·5% sodium chloride was determined. Within experimental error the relationship was found to be unique for all the lean meats studied. It was also found that a modification of the Grover method (Grover, 1947) in which a(w) is determined from the well established relationship between a(w) and sucrose equivalent, E(s), was an excellent predictor of the final a(w) of the ssystem. E(s) was calculated from E(s) = E(1)X(1) + E(1)X(2) + … etc. where E(1) are specific constants for each humectant and X(1) and X(2) are given as weight of humectant in the system/weight of water in the system. E values of 9·0 and 2·2 for sodium chloride and glycerol were applicable for initial salt concentrations of 0 to 20 (w/w)_and glycerol concentrations of 0 to 90% (w/w) The method was equally applicable to propylene glycol (E value 3·2)/salt systems and sorbitol (E value 1·0)/salt systems.     

Rheological and sensory performance of a protein-based sweetener (MNEI), sucrose,and aspartame in yogurt

Sweeteners and flavors are generally added to yogurt to make them more palatable. However, the addition of these ingredients may affect the fermentation process of yogurt as well as its physical and sensory characteristics. Consumers prioritize yogurt products that are “natural.” A modified single-chain form of the natural sweet protein monellin extracted from the fruit of Dioscoreophyllum cumminsii, called MNEI, could be a useful alternative to artificial sweeteners. The aim of the present work was to evaluate new rapid sensory methods in combination with rheology to assess the viability of using MNEI to develop sweetened yogurts without the calories of sugar. We studied the gelation and cooling kinetics of 4 yogurt samples (unsweetened or sweetened with MNEI, aspartame, or sucrose) by using a rheometer. Furthermore, the 4 yogurts, with and without addition of a flavoring agent, were characterized from a sensory perspective using a combination of 2 rapid sensory methods, ultra flash profile and flash profile. Rheological results showed that, when added at typical usage levels, aspartame, sucrose, and MNEI did not generally affect the yogurt fermentation process or its rheological properties. Sensory results demonstrated that texture attributes of yogurts with aspartame and sucrose were strongly linked to sweetness and flavor perception, but this was not true for MNEI-sweetened yogurts. In contrast to results obtained from samples sweetened with sucrose and aspartame, MNEI protein did not sweeten the yogurt when added before fermentation. This study highlights the enhancing effect of flavor on sweetness perception, supporting previous reports that noted synergistic effects between sucrose or aspartame and flavors. Hence, future studies should be conducted to determine how sweet proteins behave in yogurt when added after fermentation.     

Effects of canning on total mercury,protein, lipid,and moisture content in troll-caught albacore tuna (Thunnus alalunga)

Fifty-six cans containing meat from either the dorsal loin or the ventral flap of 10 troll-caught albacore tuna were tested for total mercury concentration prior to and after canning and retort cooking. The albacore tuna were harvested off the US Pacific Coast during the 2004 season and weighed between 5.4 and 10.2 kg. Tuna meat was packed in cans raw or in water or olive oil, and cans were drained before post-canning analysis. The average concentrations of total mercury were: 0.17 ppm (range 0.09–0.24 ppm) in the pre-canned samples and 0.21 ppm (range 0.10–0.33 ppm) in the post-canned samples. Although the mercury concentration per gram of tissue was significantly higher following canning, the overall amount of mercury in the samples did not change significantly.     

Gender differences in the inhibitory effects of a reduction in ambient temperature and a reduction in food quantity on reproduction in the Southern African rodent, Rhabdomys pumilio

The effects of a reduction in ambient temperature (from 26 degrees C to 15 degrees C) and a 10% reduction in daily food consumption on reproductively active male and female four-striped field mice ( Rhabdomys pumilio) were investigated. In male R. pumilio, both reduced ambient temperature and a reduction in food quantity had an inhibitory effect on spermatogenesis and on size of the reproductive organs, and this was greatest when the two factors were combined and the effect of fat was removed. Female R. pumilio responded differently and reproduction was inhibited by a reduction in food quantity, irrespective of ambient temperature. The masses of the ovaries and uterus, the numbers of developing follicles and corpora lutea, and the development of the uterine wall were all reduced by food deprivation at 26 degrees C to levels similar to those that resulted from a reduction in ambient temperature to 15 degrees C with a reduction in food quantity. It is concluded that reproduction in R. pumilio from the Eastern Cape Province of South Africa is opportunistic, that reproduction will be inhibited by an energetic challenge and that there is sexual dimorphism in the response to ambient temperature and food supply.     

Electroreduction of Cr(VI) to Cr(III) on reticulated vitreous carbon electrodes in a parallel-plate reactor with recirculation

The reduction of Cr(VI) to Cr(III) is achieved in a flow-by, parallel-plate reactor equipped with reticulated vitreous carbon (RVC) electrodes;this reduction can be accomplished by the application of relatively small potentials. Treatment of synthetic samples and field samples (from an electrodeposition plant) results in final Cr(VI) concentrations of 0.1 mg/L (i.e., the detection limit of the UV-vis characterization technique used here) in 25 and 43 min, respectively. Such concentrations comply with typical environmental legislation for wastewaters that regulate industrial effluents (at presenttime = 0.5 mg/L for discharges). The results show the influence of the applied potential, pH, electrode porosity, volumetric flow, and solution concentration on the Cr(VI) reduction percentage and on the required electrolysis time. Values for the mass transfer coefficient and current efficiencies are also obtained. Although current efficiencies are not high, the fast kinetics observed make this proposed treatment an appealing alternative. The lower current efficiency obtained in the case of a field sample is attributed to electrochemical activation of impurities. The required times for the reduction of Cr(VI) are significantly lower than those reported elsewhere.     

Effect of carbon,nitrogen and mineral sources on growth of Psathyerella atroumbonata (Pegler), a Nigerian edible mushroom

Effect of simple organic, inorganic and complex compounds on growth of Psathyerella atroumbonata (Pegler), a Nigerian edible mushroom, were carried out. A number of carbon compounds were utilised and glucose stimulated the best growth followed in order by mannose, cellulose and mannitol. Sorbose and myo-inositol enhanced the least growth. In the series of tested nitrogen sources, yeast extract was the most utilisable. Significant growth was supported by malt extract and l-tryptophan while poorest growth was recorded with sodium nitrate and ammonium sulphate. The best carbon/nitrogen ratio was 2:3 but the least utilised ratio was 5:1. Calcium and magnesium were the best macro-elements while micro-elements (copper and zinc) enhanced optimum growth.     

Effect of processing on the reduction of pesticide residues in a traditional Chinese medicine (TCM)

ABSTRACT

The behaviour of residues of tebuconazole, prochloraz, and abamectin in rehmannia during rehmannia decoction processing was systemically assessed. The pesticides were determined by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) after each processing step including washing, steaming and drying, carbonising, and boiling. Results showed that the pesticide residues significantly decreased after the steps of washing, carbonising, and boiling. Washing reduced pesticide residues by 41.2%–60.0%; carbonising reduced pesticides by 27.1%–71.1% in both prepared rehmannia and unprepared rehmannia. After boiling, the concentrations of tebuconazole and prochloraz were 0.0002–0.0022 mg kg^?1 in decoctions. Abamectin was not detected in rehmannia after carbonising, and it was not detected in decoctions either. The processing factors (PFs) were less than 1 during food processing, indicating that the full set of processing can reduce the residues of tebuconazole, prochloraz, and abamectin in rehmannia decoction.     

Dechlorination of trichloroethene in a continuous-flow bioelectrochemical reactor: effect of cathode potential on rate, selectivity, and electron transfer mechanisms

The exciting discovery that dechlorinating bacteria can use polarized graphite cathodes as direct electron donors in the reductive dechlorination has prompted investigations on the development of novel bioelectrochemical remediation approaches. In this work, we investigated the performance of a bioelectrochemical reactor for the treatment of trichloroethene (TCE). The reactor was continuously operated for about 570 days, at different potentiostatically controlled cathode potentials, ranging from -250 mV to -750 mV vs standard hydrogen electrode. The rate and extent of TCE dechlorination, as well as the competition for the available electrons, were highly dependent on the set cathode potential. When the cathode was controlled at -250 mV, no abiotic hydrogen production occurred and TCE dechlorination (predominantly to cis-DCE and VC), most probably sustained via direct extracellular electron transfer, proceeded at an average rate of 15.5 ± 1.2 μmol e(-)/L d. At this cathode, potential methanogenesis was almost completely suppressed and dechlorination accounted for 94.7 ± 0.1% of the electric current (15.0 ± 0.8 μA) flowing in the system. A higher rate of TCE dechlorination (up to 64 ± 2 μmol e(-)/L d) was achieved at cathode potentials lower than -450 mV, though in the presence of a very active methanogenesis which accounted for over 60% of the electric current. Remarkably, the bioelectrochemical reactor displayed a stable and reproducible performance even without the supply of organic carbon sources with the feed, confirming long-term viability.     

Bioavailability of nutrients in rats fed on edible seaweeds,Nori (Porphyra tenera) and Wakame (Undaria pinnatifida), as a source of dietary fibre

A comparative study of the influence of two edible seaweeds, Nori (Porphyra tenera) and Wakame (Undaria pinnatifida), on dietary nutritive utilization was performed. Male adult Wistar rats were fed, for 2 weeks, diets containing Nori, Wakame or cellulose as source of dietary fibre. All diets contained similar amounts of dietary fibre (5%), protein (14%) and ash (5%). Intake, body weight gain, food efficiency (weight gain/food intake), apparent digestibility and retention coefficients for protein, fat, and minerals (calcium, iron, magnesium, zinc, sodium, and potassium) were evaluated. The addition of Wakame or Nori did not affect the gain in body weight of rats or food efficiency. Fresh and dry stool weights were higher in rats fed seaweeds than in the control group. Seaweed-fed animals showed significantly lower apparent digestibilities of protein and fat but absorbed nitrogen was more effectively used by animals. Apparent digestibility and retention coefficients for calcium, magnesium, zinc, iron, sodium and potassium were lower for seaweed-fed rats, and showed lower values for Wakame than Nori. The seaweeds could be a good source of dietary fibre in diet but they may modify digestibility of dietary protein and minerals.     

Studies on tea. I. Contents of mercury, lead, and cadmium in tea leaves and tea decoctions (author's transl)]

In a survey on 25 teas from different countries for toxic trace elements the concentration of lead was found to be up to 3.08 ppm. of Cadmium up to 0.012 ppm, and of Mercury up to 3.0 ppm, respectively. The actual concentration in the tea decoction is much lower as in the tea leaves, for lead up to 0.02 ppm and for Cadmium below the sensitivity of the method. It was recommended to set the tolerable values for these elements in the tea leaf higher as recommended for the direct consumed foodstuffs or to consider the final concentration in the tea decoction only.     

Influence of rosemary (Rosmarinus officinalis, L.) on plant sterol oxidation in extra virgin olive oil

The objective of this study was to investigate the potential role of rosemary compounds in inhibiting the plant sterol oxidation in extra virgin olive oil during heating. The stability of plant sterols was measured by quantification of plant sterol and sterol oxide formation upon 6 h of heating in both the extra virgin olive oil and its respective oil at 10% rosemary concentration (ROE). The total sterol and sitosterol oxide contents were determined by GC-flame ionization detection (GC-FID) and GC-MS techniques, respectively. Heating experiments were carried out at 180 degrees C for 0, 1, 3 and 6 h. The total sterol content in the extra virgin olive oil was 255 mg/100 g and that in the ROE 270 mg/100 g. Sitosterol was the most abundant sterol in both samples (50% of total sterol). The ROE showed a lower content of sitosterol oxides with respect to the extra virgin olive oil during heating: after 6 h of heating only 6.1% of sitosterol oxides were formed, while up to 11.5% of sitosterol oxidized in the extra virgin olive oil. Our findings suggested that rosemary compounds were able to counteract the oxidation of plant sterols in the extra virgin olive oil during heating, preventing formation of potentially harmful compounds to human health.     

Multispectroscopic studies on the interaction of 2-tert-butylhydroquinone (TBHQ), a food additive,with bovine serum albumin

The interaction of 2-tert-butylhydroquinone (TBHQ) and bovine serum albumin (BSA) was investigated by spectrophotometry, spectrofluorimetry, circular dichroism (CD) and FT-IR techniques. The experimental results indicated that the quenching mechanism of BSA by TBHQ was a static procedure. Various binding parameters were evaluated. The negative value of ΔH, positive value of ΔS and the negative value of ΔG indicated that hydrophobic and hydrogen bonding interactions play major roles in the binding of TBHQ and BSA. Based on Forster’s theory of non-radiation energy transfer, the binding distance, r, between the donor (BSA) and acceptor (TBHQ) was evaluated. The results of CD, UV–vis and FT-IR spectroscopy showed that the binding of TBHQ to BSA induced conformational changes in BSA.