Mechanisms of arsenate adsorption by highly-ordered nano-structured silicate media impregnated with metal oxides

The highly ordered mesoporous silica media, SBA-15, was synthesized and incorporated with iron, aluminum, and zinc oxides using an incipientwetness impregnation technique. Adsorption capacities and kinetics of metal-impregnated SBA-15 were compared with activated alumina which is widely used for arsenic removal. Media impregnated with 10% of aluminum by weight (designated to Al10SBA-15) had 1.9-2.7 times greater arsenate adsorption capacities in a wide range of initial arsenate concentrations and a 15 times greater initial sorption rate at pH 7.2 than activated alumina. By employing one- and two-site models, surface complexation modeling was conducted to investigate the relationship between the aluminum oxidation states in different media and adsorption behaviors shown by adsorption isotherms and kinetics since the oxidation phase of aluminum incorporated onto the surface of SBA-15 was Al-O, which has a lower oxidation state than activated alumina (Al2O3). Surface complexation modeling results for arsenate adsorption edges conducted with different pH indicated thatthe monodentate complex (SAsO(4)2-) was dominant in Al10SBA-15, while bidentate complexes (XHAsO4 and XAsO4-) were dominant in activated alumina at pH 7.2, respectively. In kinetic studies at pH 7.2 + 0.02, Al10SBA-15 had only a fast-rate step of initial adsorption, while activated alumina had fast- and slow-rate steps of arsenate adsorption. Therefore, it can be inferred that the monodentate arsenate complex, predominant in Al10SBA-15, leads to faster adsorption rates than bidentate arsenate complexes favored with activated alumina. An arsenate adsorption behavior and arsenate surface complexation were thought to be well explained by aluminum oxidation states and surface structural properties of media.     

Coprecipitation of arsenate with metal oxides. 2. Nature, mineralogy, and reactivity of iron(III) precipitates

Coprecipitation of arsenic with iron or aluminum occurs in natural environments and is a remediation technology used to remove this toxic metalloid from drinking water and hydrometallurgical solutions. In this work, we studied the nature, mineralogy, and reactivity toward phosphate of iron-arsenate coprecipitates formed at As(V)/Fe(III) molar ratios (R) of 0, 0.01, or 0.1 and at pH 4.0, 7.0, and 10.0 aged for 30 or 210 days at 50 degrees C and studied the desorption of arsenate. At R = 0, goethite and hematite (with ferrihydrite at pH 4.0 and 7.0) crystallized, whereas at R = 0.01, the formation of ferrihydrite increased and hematite crystallization was favored over goethite. In some samples, the morphology of hematite changed from rounded platy crystals to ellipsoids. At R = 0.1, ferrihydrite formed in all the coprecipitates and remained unchanged even after 210 days of aging. The surface area and chemical composition of the precipitates were affected by pH, R, and aging. Chemical dissolution of the samples showed that arsenate was present mainly in ferrihydrite, but at R = 0.01, it was partially incorporated into the structures of crystalline Fe oxides. The sorption of phosphate on to the coprecipitates was affected not only by the mineralogy and surface area of the samples but also by the amounts of arsenate present in the oxides. The samples formed at pH 4.0 and 7.0 and at R = 0.1 sorbed lower amounts of phosphate than the precipitates obtained at R = 0 or 0.01, despite the former having a larger surface area and showing only a presence of short-range ordered materials. This is mainly due to the fact that in the coprecipitates at R = 0.1 arsenate occupied many sorption sites, thus preventing phosphate sorption. Less than 20% of the arsenate present in the coprecipitates formed at R = 0.1 was removed by phosphate and more from the samples synthesized at pH 7.0 or 10.0 than at pH 4.0. Moreover, we found that more arsenate was desorbed by phosphate from a ferrihydrite on which arsenate was added than from an iron-arsenate coprecipitate, attributed to the partial occlusion of some arsenate anions into the framework of the coprecipitate. XPS analyses confirmed these findings.     

Coprecipitation of arsenate with metal oxides: nature, mineralogy, and reactivity of aluminum precipitates

Arsenic mobilization in soils is mainly controlled by sorption/desorption processes, but arsenic also may be coprecipitated with aluminum and/or iron in natural environments. Although coprecipitation of arsenic with aluminum and iron oxides is an effective treatment process for arsenic removal from drinking water, the nature and reactivity of aluminum- or iron-arsenic coprecipitates has received little attention. We studied the mineralogy, chemical composition, and surface properties of aluminum-arsenate coprecipitates, as well as the sorption of phosphate on and the loss of arsenate from these precipitates. Aluminum-arsenate coprecipitates were synthesized at pH 4.0, 7.0, or 10.0 and As/Al molar ratio (R) of 0, 0.01, or 0.1 and were aged 30 or 210 d at 50 degrees C. In the absence of arsenate, gibbsite (pH 4.0 or 7.0) and bayerite (pH 10.0) formed, whereas in the presence of arsenate, very poorly crystalline precipitates formed. Short-range ordered materials (mainly poorly crystalline boehmite) formed at pH 4.0 (R = 0.01 and 0.1), 7.0, and 10.0 (R= 0.1) and did not transform into Al(OH)3 polymorphs even after prolonged aging. The surface properties and chemical composition of the aluminum precipitates were affected by the initial pH, R, and aging. Chemical dissolution of the samples by 6 mol L(-1) HCl and 0.2 mol L(-1) oxalic acid/ oxalate solution indicated that arsenate was present mainly in the short-range ordered precipitates. The sorption of phosphate onto the precipitates was influenced by the nature of the samples and the amounts of arsenate present in the precipitates. Large amounts of phosphate partially replaced arsenate only from the samples formed at R = 0.1. The quantities of arsenate desorbed from these coprecipitates by phosphate increased with increasing phosphate concentration, reaction time, and precipitate age butwere always lessthan 30% of the amounts of arsenate present in the materials and were particularly low (<4%) from the sample prepared at pH 4.0. Arsenate appeared to be occluded within the network of short-range ordered materials and/or sorbed onto the external surfaces of the precipitates, but sorption on the external surfaces seemed to increase by increasing pH of sample preparation and aging. Furthermore, at pH 4.0 more than in neutral or alkaline systems the formation of aluminum arsenate precipitates seemed to be favored. Finally, we have observed that greater amounts of phosphate were sorbed on an aluminum-arsenate coprecipitate than on a preformed aluminum oxide equilibrated with arsenate under the same conditions (R = 0.1, pH 7.0). In contrast, the opposite occurred for arsenate desorption, which was attributed to the larger amounts of arsenate occluded in the coprecipitate.     

Photodegradation of decabromodiphenyl ether adsorbed onto clay minerals, metal oxides, and sediment

The photodebromination of decabromodiphenyl ether (BDE-209) adsorbed onto six different solid matrixes was investigated in sunlight and by irradiation with 350 +/- 50 nm lamps (four lamps at 24 W each). After 14 days of lamp irradiation, BDE-209 degraded with a half-life of 36 and 44 days, respectively, on montmorillonite or kaolinite, with much slower degradation occurring when sorbed on organic carbon-rich natural sediment (t1/2 = 150 days). In late summer and fall sunlight (40.5 degrees N, elevation 600 ft), the half-lives of BDE-209 sorbed on montmorillonite and kaolinite were 261 and 408 days, respectively. Under both irradiation schemes, no significant loss of BDE-209 occurred when sorbed to aluminum hydroxide, iron oxide (ferrihydrite), or manganese dioxide (birnessite). Upon exposure to both lamp and solar light and in the presence of montmorillonite and kaolinite, numerous lesser brominated congeners (tri- to nonabromodiphenyl ethers) were produced. Nearly identical product distribution was evident on montmorillonite and kaolinite. Dark control experiments for each mineral showed no disappearance of BDE-209 or appearance of degradation products. These results suggest that photodegradation of BDE-209 on mineral aerosols during long-range atmospheric transport may be an important fate process for BDE-209 in the environment.     

Effect of oxide formation mechanisms on lead adsorption by biogenic manganese (hydr)oxides, iron (hydr)oxides, and their mixtures

The effects of iron and manganese (hydr)oxide formation processes on the trace metal adsorption properties of these metal (hydr)oxides and their mixtures was investigated by measuring lead adsorption by iron and manganese (hydr)oxides prepared by a variety of methods. Amorphous iron (hydr)oxide formed by fast precipitation at pH 7.5 exhibited greater Pb adsorption (gamma(max) = 50 mmol of Pb/mol of Fe at pH 6.0) than iron (hydr)oxide formed by slow, diffusion-controlled oxidation of Fe(II) at pH 4.5-7.0 or goethite. Biogenic manganese(III/IV) (hydr)oxide prepared by enzymatic oxidation of Mn(II) by the bacterium Leptothrix discophora SS-1 adsorbed five times more Pb (per mole of Mn) than an abiotic manganese (hydr)oxide prepared by oxidation of Mn(II) with permanganate, and 500-5000 times more Pb than pyrolusite oxides (betaMnO2). X-ray crystallography indicated that biogenic manganese (hydr)oxide and iron (hydr)oxide were predominantly amorphous or poorly crystalline and their X-ray diffraction patterns were not significantly affected by the presence of the other (hydr)oxide during formation. When iron and manganese (hydr)oxides were mixed after formation, or for Mn biologically oxidized with iron(III) (hydr)oxide present, observed Pb adsorption was similar to that expected for the mixture based on Langmuir parameters for the individual (hydr)oxides. These results indicate that interactions in iron/manganese (hydr)oxide mixtures related to the formation process and sequence of formation such as site masking, alterations in specific surface area, or changes in crystalline structure either did not occur or had a negligible effect on Pb adsorption by the mixtures.     

Total phenolic compounds,radical scavenging and metal chelation of extracts from Icelandic seaweeds

Screening of potential antioxidant activities of water and 70% acetone extracts from ten species of Icelandic seaweeds was performed using three antioxidant assays. Significant differences were observed both in total phenolic contents (TPC) and antioxidant activities of extracts from the various species evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, oxygen radical absorbance capacity (ORAC) and ferrous ion-chelating ability assays. Acetone extracts from three Fucoid species had the highest TPC and consequently exhibited the strongest radical scavenging activities. High correlation was found between TPC of seaweed extracts and their scavenging capacity against DPPH and peroxyl radicals, indicating an important role of algal polyphenols as chain-breaking antioxidants. However, water extracts generally had higher ferrous ion-chelating activity than 70% acetone extracts and no correlation was found with their TPC, suggesting that other components such as polysaccharides, proteins or peptides in the extracts were more effective chelators of ferrous ions than phenolic compounds.     

Quality and safety evaluation of genetically modified potatoes spunta with Cry V gene: compositional analysis, determination of some toxins, antinutrients compounds and feeding study in rats

The aim of this study was to evaluate the composition, nutritional and toxicology safety of GM potato Spunta lines compared to that of conventional potato Spunta. Compositional analyses were conducted to measure the proximate chemical composition with references to 14 components, total solid, protein, lipid, crude fibre, ash, carbohydrate, starch, reducing sugar, nonreducing sugar, sodium, calcium, potassium, phosphorus, and ascorbic acid. Some toxins and anti-nutrients compounds were determined. Feeding study of GM potatoes line (G2 and G3) in rats were done for 30 days. Four groups of albino rats were used for studying the effect and the safety assessment of GM potatoes Spunta G2 and G3. Group (I) was fed on control basal diet, group (II) was fed on control diet plus 30% freeze-dried nongenetically modified potato Spunta, group (III) was fed on control diet plus 30% freeze-dried genetically modified potato Spunta, and group (IV) was fed on control diet plus 30% freeze-dried genetically modified potato Spunta GMO G3. There were no significant differences between GM potatoes G2, G3, and Spunta control potato line in the proximate chemical composition. The levels of glycoalkaloids in transgenic potato tubers and nontransgenic were determined and there were also no significant differences between the GM potatoes and conventional potato line, the levels were in agreement with a safety level recommended by FAO/WHO (200 mg/ kg) for acute toxicity. Protease inhibitor activity and total phenol were estimated and no significant differences between the GM potatoes line and conventional potato Spunta line were found. During the period tested, rats in each group (I, II, III, IV) grew well without marked differences in appearance. No statistical difference were found in food intake, daily body weight gain and feed efficiency. But there is a slightly significant difference in finally body weight between the control group and experimental groups. No significant difference were found in serum biochemical value between each groups, and also between relative organs weight (liver, spleen, heart, kidney, testes). From these results, it can be concluded that the GM potatoes Spunta line (G2 and G3) with Cry V gene are confirmed to have nearly the composition and biochemical characteristics as non-GM potato Spunta.     

Kinetics of simultaneous photocatalytic degradation of phenolic compounds and reduction of metal ions with nano-TiO2

The simultaneous photocatalytic degradation of phenol and 4-nitrophenol and reduction of metal ions like copper (Cu2+) and chromium (Cr6+) was studied with solution combustion synthesized nanoanatase TiO2 (CS TiO2) and commercial titania, Degussa P-25. The presence of metal ion reduces the rate of degradation of phenol and 4-nitrophenol. It was found that Cu2+ reduction to Cu+ is accelerated in the presence of phenol. In the case of Cr6+, CS TiO2 enhances the initial adsorption of Cr6+ and complete reduction is achieved within the first 10 min of UV irradiation. The presence of phenol or 4-nitrophenol also enhances the initial adsorption of Cr6+ and its reduction. The metal ion reduction in the presence of CS TiO2 is compared with that of Degussa P-25. The rate of reduction of metal ions in presence of Degussa P-25 is twice as slow as that of CS TiO2 in presence of both phenol and 4-nitrophenol. The presence of Cu2+ and Cr6+ also induces the formation of the intermediates which were not observed for the phenol-CS TiO2 system. The formation and consumption of the intermediates are modeled with a simple series reaction mechanism. A detailed dual-cycle, multistep reaction mechanism of TiO2 photocatalysis for the simultaneous degradation and reduction is proposed and the model is developed following the network reduction technique. The kinetic rate constants in the model are evaluated for the systems studied.     

Effects of isoacids, urea, and sulfur on ruminal fermentation in sheep fed high fiber diets.

The effects of isoacids, urea N, and S on ruminal fermentation of sugarcane bagasse- or corn stover-based diets were studied in sheep. Acetate production was taken as a measure of the fermentation rate. For the sugarcane bagasse diet, neither urea nor S supplementation changed ruminal acetate production. When N and S were combined, acetate production was 44% higher (3.16 vs. 2.18 mol/d). Similar effects were noted for the corn stover diet. Increasing the level of isoacids from .1 to .2 g/kg BW per d in the diet did not change acetate production for either diet. However, N supplementation of the sugarcane bagasse diet containing the low level of isoacids resulted in a 49% greater acetate production (2.86 vs. 1.91 mol/d). Acetate production was 90% higher (3.74 vs. 1.97 mol/d) when the diet containing the high level of isoacids was supplemented with N. The corresponding increases for corn stover were 12% (2.64 to 2.95 mol/d) and 35% (2.88 to 3.87 mol/d). The results suggest that NH3 N provided by the basal diet was more limiting than isoacids. Once the N deficiency was corrected, isoacids became limiting. Ruminal digestion of high fiber diets low in N was improved by supplementation with urea, isoacids, and S.     

Taste interaction of ethyl alcohol with sweet, salty, sour and bitter compounds

The influence of ethyl alcohol in concentrations ranging from 4 to 24%, on the perceived taste intensities of sucrose, citric acid, quinine, and sodium chloride was determined by 24 subjects. A paired comparison method was used in which subjects selected the sample with the greater taste intensity (sweetness, sourness, bitterness or saltiness) as well as rating the intensity on a 13-point scale. The alcohol generally enhanced the sweetness of sucrose, with results varying slightly according to the subjects' task. The sourness of citric acid, and the saltiness of sodium chloride at all but the lowest concentration, were depressed by increasing additions of alcohol. Alcohol significantly enhanced the bitterness of quinine at all four concentrations. Although these results disagree with previously reported electrophysiological measurements on alcohol-quinine mixtures, they were internally consistent, and meaningful in terms of alcoholic beverage consumption behaviour.     

Manganese oxides with rod-, wire-, tube-, and flower-like morphologies: highly effective catalysts for the removal of toluene

Nanosized rod-like, wire-like, and tubular α-MnO(2) and flower-like spherical Mn(2)O(3) have been prepared via the hydrothermal method and the CCl(4) solution method, respectively. The physicochemical properties of the materials were characterized using numerous analytical techniques. The catalytic activities of the catalysts were evaluated for toluene oxidation. It is shown that α-MnO(2) nanorods, nanowires, and nanotubes with a surface area of 45-83 m(2)/g were tetragonal in crystal structure, whereas flower-like spherical Mn(2)O(3) with a surface area of 162 m(2)/g was of cubic crystal structure. There were the presence of surface Mn ions in multiple oxidation states (e.g., Mn(3+), Mn(4+), or even Mn(2+)) and the formation of surface oxygen vacancies. The oxygen adspecies concentration and low-temperature reducibility decreased in the order of rod-like α-MnO(2) > tube-like α-MnO(2) > flower-like Mn(2)O(3) > wire-like α-MnO(2), in good agreement with the sequence of the catalytic performance of these samples. The best-performing rod-like α-MnO(2) catalyst could effectively catalyze the total oxidation of toluene at lower temperatures (T(50%) = 210 °C and T(90%) = 225 °C at space velocity = 20,000 mL/(g h)). It is concluded that the excellent catalytic performance of α-MnO(2) nanorods might be associated with the high oxygen adspecies concentration and good low-temperature reducibility. We are sure that such one-dimensional well-defined morphological manganese oxides are promising materials for the catalytic elimination of air pollutants.     

Determination of butyltin, cyclohexyltin and phenyltin compounds in beers and wines.

Butyl- cyclohexyl- and phenyltin compounds were extracted from enzymically-hydrolysed wine and beer samples with 0.05% tropolone in pentane. Methyl derivatives were made by Grignard reaction for determination by gas chromatography-atomic absorption spectrometry. Wine and beer samples contained less than 0.1 to 160 nl/ml of butyltins from an undetermined source of contamination. GC-MS confirmation of butyltins also detected phenyltin, and di- and tricyclohexyltin compounds at levels less than the GC-AAS based method detection limits of 0.05-0.13 ng Sn/mL.     

Development of engineered natural organic sorbents for environmental applications. 1. Materials, approaches, and characterizations

A technology for effecting diagenesis-like transformations in young natural organic matter (NOM) derived from common plant materials is described. Thirteen such materials were processed in liquid-phase water at superheated temperature/pressure conditions. In all cases significant changes in the physical and chemical properties of the raw NOM source materials occurred. Their carbon and nitrogen contents increased, their hydrogen and oxygen contents decreased, their surface areas initially increased dramatically, then sharply decreased, and their bulk densities and equilibrated aqueous phase pH values increased as functions of increasing temperature and pressure. Spectroscopic analyses confirmed marked changes in the molecular structures of the NOMs resulting from superheated water processing; e.g., fractions of alkyl and aromatic carbons increased while oxygen-associated functional organic carbon decreased. These changes in elemental composition and molecular structure indicate that the organic fractions of the raw materials became less polar, increasingly condensed, and more aromatic as a result of the reactions induced by superheated water processing, the changes correlating directly with the temperature/ pressure conditions employed. The results presented confirm that the long-term biogeochemical processes that in nature effect geologically slow advances in the chemical states of organic carbon can be simulated and markedly accelerated by superheated water processing.     

Review: Assessing and managing risk due to consumption of seafood contaminated with micro-organisms, parasites, and natural toxins in the US

While most seafoods consumed in the US are wholesome, a variety of infectious agents and toxins have been implicated in disease aetiology. The major risk of acute illness is associated with consumption of raw molluscan shellfish. Most reported seafood-associated illness (55%) have unknown aetiologies; they are believed to be due mainly to Norwalk, Norwalk-like, or human enteric virus infection, with a smaller proportion caused by Vibrio bacteria. Parasites are less common than microbiological infections, with anisakids and cestodes having the greatest risks. People consuming tropically-caught fish have a risk of acquiring ciguatera poisoning. Other common natural intoxications (mainly scombroid and to a lesser extent paralytic poisonings) occur due to consumption of finfish and shellfish, respectively.
Reduction of risks from the consumption of raw molluscs and other fishery products can be achieved by the following means: research to develop valid human enteric virus indicators, implementing and maintaining proper treatment and disposal of sewage, efforts aimed at identifying and limiting the number of pathogenic Vibrio species in shellfish, developing new diagnostic methods and improved processing technologies, applying risk-based control measures for potential microbial pathogens in raw shellfish, cooking of seafoods, and proper application of a Hazard Analysis Critical Control Point (HACCP) system to processing and preparation operations of fishery products.     

啤酒强制老化过程中SO2、抗氧化力与TBA值的相关性研究

研究了啤酒强制老化过程中二氧化硫含量、抗氧化力评价指标与TBA值之间的相关性。Person相关性分析表明:二氧化硫含量与DPPH自由基清除活性、ABTS自由基阳离子清除活性、还原力和金属螯合性之间有显著的正相关性,TBA值与抗氧化评价指标及二氧化硫含量之间呈显著的负相关性。逐步回归分析表明:提高啤酒中DPPH自由基清除活性可以抑制啤酒老化的TBA值,对TBA的抑制力达到97.7%。     

Ambient gas/particle partitioning. 1. Sorption mechanisms of apolar, polar, and ionizable organic compounds

There remain several ambiguities in the literature regarding the dominating sorption mechanisms involved in gas/particle partitioning, particularly for polar and ionizable compounds. The various hypothetical mechanisms would depend differently on relative humidity (RH) and the presence of various aerosol components. Thus, in order to resolve these ambiguities, here we measured the RH-dependency of gas/particle partitioning constants, K(ip), for four diverse aerosol samples and a large set of chemicals covering apolar, polar, and ionizable organic compounds. In addition, we also removed the water-soluble components from two ambient particle samples to study how their presence influences sorption behavior. The measured K(ip) values collectively indicate that a dual-phase sorption mechanism is occurring, in which organic compounds partition into a RH-independent water-insoluble organic matter phase and additionally into a RH-dependent mixed-aqueous phase. All K(ip) values could be successfully fitted to a RH-dependent dual-phase sorption model. The trends in K(ip) data further support findings that the sorption behavior of ambient aerosol samples is different from raw mineral surfaces and soot.     

Contributions to the chemistry of human hair. 1. Analyses of cystine, cysteine and cystine oxides in untreated human hair

Amino acid analysis, photometry and polarography were selected as analytical methods for the determination of thiol and disulphide groups in untreated human hair and the results are discussed. The pre-treatments necessary for the different analytical methods, e.g., hydrolysis, to some extent already induce chemical changes of the cysteine and cystine derivatives leading to method-dependent differences in the results. In many cases the partial oxidation products of cystine are supposed to be responsible for this effect. Electron Spectroscopy for Chemical Analysis (ESCA), as an analytical method for the determination of the cystine oxides, was found to be inapplicable due to insufficient resolution and sensitivity, whereas by the use of Fourier Transform Infrared (FTIR) Spectroscopy the sulphur-oxygen vibrations could be analysed and cystine monoxide and cystine dioxide were detected.