Studies on the constituents of the green alga <Emphasis Type="Italic">Ulva lactuca</Emphasis>

Phytochemical investigations on a marine green alga Ulva lactuca led to the isolation of two new compounds (E)-6-heptacosen-5-one (1) and (E)-6-octadecen-5-ol (2), along with four known compounds, (Z)-10-hexacosene (3), docosanoic acid (4), palmitic acid (5), and isofucosterol (6). Compounds 3 and 4 were isolated for the first time from this species. The structures of the compounds were deduced with the help of modern spectroscopic techniques.     

Reduction of uranium concentration in well water by Chlorella (Chlorella pyrendoidosa) a fresh water algae immobilized in calcium alginate

A great deal of research has been directed towards the problem of reduction of uranium concentration from few hundreds of ppb to less than 20 ppb, a limit of uranium in drinking water from ground water resources fixed in Dec, 2001 by US, Environmental Protection Agency. Laboratory simulated experiments were carried out for the reduction of U(VI) concentration in well water from few thousands of ppb to less than 20 ppb. Well water samples were spiked with U(IV) ranging from 1000 to 2000 ppb. The contaminated solutions were passed through a glass column containing of chlorella impregnated beads of calcium alginate. Chlorella(Chlorella pyrendoidosa), a fresh water algae, was immobilized in sodium alginate in the form of beads by using 0.2M calcium chloride solution. The solution was passed again through a charcoal solution to remove any trace of impurities. The concentration of uranium after treatment ranged from 10 to 20 ppb. The concentration of other major cations and anions in the solution were also monitored. This low cost kit was proposed for on-line removal of uranium from ground water used for drinking purposes. For taking care of waste disposal, 99-100% of the adsorbed uranium on beads was recovered by 0.1M HNO₃. The desorption results suggest that the uptake of uranium by Chlorella is a physico-chemical adsorption on the cell surface, not a biological activity. The uranium in the algal cells is coupled to the ligand, which can be easily substituted with NO₃ ^-. This revised version was published online in July 2006 with corrections to the Cover Date.     

Bioaccumulation of uranium 234U and 238U in marine birds

In the paper was presented results of our study about uranium ²³⁴U and ²³⁸U radioactivity in the marine birds samples, collected in the Polish area of the southern Baltic Sea. We chose 11 species of sea birds: three species permanently residing at southern Baltic, four species of wintering birds and three species of migrating birds. The obtained results indicated that uranium is very irregularly distributed in organs and tissues of marine birds. The highest uranium content is characterized in liver, rest of viscera and feathers, the smallest in skin and muscles. The uranium concentration was higher for carnivorous species (long-tailed duck (C. hyemalis), common eider (S. mollissima), lower for species eating fish (great cormorant (P. carbo), common guillemot (U. aalge), red-throated diver (G. stellata) and razorbill (A. tarda)), but the biggest amounts for herbivorous species [tufted duck (A. fuligula) and eurasian coot (F. atra)]. About 63–67% of uranium, which was located in feathers of two species of marine birds: razorbill (A. tarda) and long-tailed duck (C. hymealis), was apparently adsorbed, which suggests that uranium adsorption on the feathers may be an important transfer from air to water.     

Distribution of uranium in sediment of creek ecosystem

The present study was carried on distribution of uranium isotopes and Thorium in marine sediment from creek of Mumbai Harbour Bay (MHB) using radiochemical separation followed by alpha spectrometry. The activity concentration of uranium and thorium in sediment of MHB has ranged between 1–4 and 1.8–4.5 ppm respectively. The activity ratio of ²³⁴U/²³⁸U in sediment was found close to unity at most of the locations of creek suggesting a conservative behaviour. The observed Th/U ratio (0.9) in comparison to global Th/U ratio (?3.5) in the creek sediment indicates that it receives low radiogenic nature of terronenous input.     

Adsorption and thermodynamic behavior of uranium(VI) on <Emphasis Type="Italic">Ulva sp</Emphasis>.-Na bentonite composite adsorbent

Summary The algae-clay composite adsorbent was tested for its ability to recover U(VI) from diluted aqueous solutions. Macro marine algae (Ulva sp.) and clay (Na bentonite) were used to prepare composite adsorbent. The ability of the composite adsorbent to adsorp uranium(VI) from aqueous solution has been studied at different optimized conditions of pH, concentration of U(VI), temperature, contact time. Parameters of desorption were also investigated to recover the adsorbed uranium. The adsorption patterns of uranium on the composite adsorbent followed the Freundlich and Dubinin-Radushkevich isotherms. The thermodynamic parameters such as the enthalpy ΔH, entropy ΔS and Gibbs free energy ΔG were calculated from the slope and intercept of lnK_d vs. 1/T plots. The results suggested that the Ulva sp.-Na bentonite composite adsorbent is suitable as sorbent material for recovery and biosorption/adsorption of uranium ions from aqueous solutions.     

Uranium recovery from Uro area phosphate ore,Nuba Mountains,Sudan

This study was carried out in a laboratory scale to recover uranium from Uro area phosphate ore in the eastern part of Nuba Mountains in Sudan. Phosphate ore samples were collected, and analyzed for uranium abundance. The results showed that the samples contain a significant concentration of uranium with an average of 310.3 μg/g, which is 2.6 times higher than the world average of phosphate. The green phosphoric acid obtained from the samples was found to contain uranium in the range of 186–2049 μg/g, with an average of 603.3 μg/g, and about 98% of uranium content of the phosphate ore was rendered soluble in the phosphoric acid. An extraction process using 25% tributylphosphate, followed by stripping process using 0.5 M sodium carbonate reported that more than 98% of uranium in the green phosphoric acid exists as uranyl tricarbonate complex, moreover, sodic decomposition using 50% sodium hydroxide showed that about 98% of the uranium was precipitated as sodium diuranate concentrate that is known as the yellow cake (Na₂U₂O₇). Further purification and calcinations of the yellow cake led to the formation of the orange powder of uranium trioxide (UO₃). The chemical analysis of the obtained uranium concentrates; yellow cake and uranium trioxide proved their nuclear purity and that they meet the standard commercial specification. The obtained results proved that uranium from Uro phosphate ore was successfully recovered as uranium trioxide with an overall recovery percentage of 93%.     

Structure and Synthesis of (±)-Caudoxirene,a New Spermatozoid-Releasing and -Attracting Pheromone from the Marine Brown Alga Perithalia caudata (Phaeophyceae,Sporochnales). Part V

Cis-3-(trans-1,2-Epoxybut-3-enyl)-4-vinylcyclopentene ((±)- 4 , caudoxirene) is a new gamete-releasing and gamete-attracting pheromone from the marine brown alga Perithalia caudata (Sporochnales). The key step of its synthesis is the diastereoselective alkylation of the aldehyde 8 with the [(phenylthio)allyl]titanium reagent 9 to yield the erythro-β-hydroxy sulfide 10 which affords 4 on sequential treatment with Me₃O·BF₄ and aq. NaOH. The lowest effective concentration of (±)- 4 for gamete-release is found at 1.4 × 10^?11 mol/l seawater.     

DIFFERENTIAL EFFECT OF CALCIUM ON CHLOROPLAST MOVEMENT IN MOUGEOTIA

The flat, ribbon-shaped chloroplast in the filamentous green alga Mougeotia sp. undergoes light-induced orientational movement controlled by an intracellular tetrapolar gradient of the active form of phytochrome, P_fr. Some substructural and physiological aspects of this reaction were studied. An intracellular pattern of microfilaments (diameter: 5–10nm), presumably related to chloroplast movement, was identified in situ. In addition, it could be shown that chloroplast movement decreases parallel to a nitric acid soluble fraction of intracellular calcium. These results might indicate that phytochrome governs chloroplast movement in Mougeotia via control of the binding state of calcium.     

Separation studies of uranium and thorium using tetra(2-ethylhexyl) diglycolamide (TEHDGA) as an extractant

The extraction behavior of uranium, thorium and nitric acid has been investigated for the TEHDGA/isodecyl alcohol/n-dodecane solvent system. Conditional acid uptake constant (K _H) of TEHDGA/n-dodecane and the ratio of TEHDGA to nitric acid were obtained as 1.72 and 1:0.96, respectively. The extracted species of uranium and thorium in the organic phase were found to be UO₂(NO₃)₂·2TEHDGA and Th(NO₃)₄·2TEHDGA. A workable separation factor (D _Th/D _U) of the order of 300 was observed between thorium and uranium in the nitric acid range of 0.5M to 1.5M. Similar separation factor was also achieved at higher acidity when thorium was present in large concentration compared to uranium. These results indicate that TEHDGA solvent system could be a potential candidate for separation of thorium from uranium.     

Recovery of Uranium(VI) from Sulfate Leach Liquor using Modified Duolite

Silicate mercapto Duolite composite ( SMDC ) and activated Duolite A 101 D ( AD ) were prepared, characterized, and tested for uranium removal from sulfate solution using batch experiment technique. The capability of newly adsorbents for sorption of uranium was estimated and optimized under different controlling variables, including the impact of uranium initial concentration, pH of the medium, equilibrium time, temperatures, dose and interfering ions. Testing of different adsorbents for adsorption isotherms revealed that the achieved experimental data were fitting well with the Langmuir isotherm model with 68.02 mg · g^–1 and 208.33 mg · g^–1 as theoretical capacity for AD and SMDC , respectively. Thermodynamic parameters have been resulted in negative values for ΔH and ΔS indicating an exothermic and decreased randomness behavior for uranium(VI) adsorption, while negative values of ΔG indicate spontaneous uranium adsorption. The kinetics studies showed that the adsorption process was controlled expressed by pseudo-second order model. Finally, the optimized factors have been applied for uranium(VI) recovery from Gattar leach liquor producing a uranium concentrate (Na₂U₂O₇) with uranium concentration of 70 % and purity of 93.33 %.     

Production of l-lactic acid byRhizopus oryzae in a bubble column fermenter

Two distinctive forms of growth (mycelial filamentous and mycelial pellets) ofRhizopus oryzae were obtained by manipulating the initial pH of the medium with the controlled addition of CaCO₃ in a bubble fermenter. In the presence of CaCO₃, diffused filamentous growth was obtained when the initial pH of the substrate was 5.5. In the absence of CaCO3, mycelial pellet growth was obtained when the initial pH was 2.0. The fermentation study indicated that the mycelial growth has a shorter lag period before the onset of acid formation. Both physical forms of growth ofRhizopus exhibited a high yield of L-lactic acid in the bubble fermenter when the initial glucose concentration exceeded 70 g/L. A final lactic acid concentration of 62 g/L was produced by the filamentous form ofRhizopus from 78 g/L glucose after 27 h. This showed a weight yield of 80% of glucose consumed, with an average specific productivity of 1.46 g/h/g. Similarly, the pellet form ofRhizopus produced a final lactic acid concentration of 66 g/L from 76 g/L glucose after 43 h, with a weight yield of 86% and an average specific productivity of 1.53 g/h/g.     

Radioactivity of coal and ashes from Figueira coal power plant in Brazil

Summary The Figueira coal-fired power plant (CFPP) is among the Brazilian CFPP which presents higher uranium concentration. Gamma-ray spectrometry was used to determine ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³² Th and ⁴⁰K contents in pulverized coal, furnace bottom ash and fly ash samples. The natural radionuclide concentrations in pulverized coal ranged from 813 to 2609 Bq ^. kg^-1 for U series and from 22 to 40 Bq ^. kg^-1 for ²³² Th. The fly ash fraction gave concentrations ranging from 1442 to 14641 Bq ^. kg^-1, for uranium series. The same enrichment factor was observed for ²³⁸U, ²²⁶Ra and ²³² Th. Only ²¹⁰Pb and stable Pb presented a high enrichment factor for the last stage filter fly ash. The concentration of the uranium series found in the ashes is close to the limit adopted by the Brazilian guideline (CNEN-NN-4.01).²² Therefore, it is advisable to evaluate the environmental impact of the installation.     

Batch and dynamic extraction of uranium(VI) from nitric acid medium by commercial phosphinic acid resin,Tulsion CH-96

Batch and dynamic extractions of uranium(VI) in 10⁻³–10⁻²M concentrations in 3–4M nitric acid medium have been investigated using a commercially available phosphinic acid resin (Tulsion CH-96). The extraction of uranium(VI) has been studied as a function of time, batch factor (V/m), concentrations of nitric acid and uranium(VI) ion. Dual extraction mechanism unique to phosphinic acid resin has been established for the extraction of uranium(VI). Distribution coefficient (K _d ) of uranium(VI) initially decreases with increasing concentration of nitric acid, reaches a minimum value at 1.3M, followed by increases in K _d . A maximum K _d value of ∼2000 ml/g was obtained at 5.0M nitric acid. Batch extraction data has been fitted into the linearized Langmuir adsorption isotherm. The performance of the resin under dynamic extraction conditions was assessed by following the breakthrough behavior of the system. Effect of flow rate, concentrations of nitric acid and uranium ion in the feed on the breakthrough behavior of the system was studied and the data was fitted using Thomas model.     

Absolute Configuration and Synthesis of (+)-Caudoxirene,the Gamete-Releasing and Gamete-Attracting Pheromone of the Brown Alga Perithalia caudata (Phaeophyceae)

The absolute configuration of the gamete-releasing and -attracting pheromone 2-vinyl-3-(5′-vinylcyclopent-2′-enyl)oxirane ( =(+)-caudoxirene; (+)- 1 ) of the marine brown alga Perithalia caudata is established as (2R,3R,1′S,5′S). Highly diastereoselective syntheses and the biological activities of three diastereoisomers of 1 are described. Compound (+)-(2R,3R,1′S,5′S)- 1 is the first fully characterized epoxypheromone from marine brown algae (Phaeophyceae).     

Highly sensitive ion preconcentration method based on flow sorbent extraction using multiwall carbon nanotubes

In this work a solid phase on-line uranium ion preconcentration system coupled with spectrophotometry has been developed. The method is based on uranyl ion preconcentration at pH 3.75 onto multiwall carbon nanotubes treated with HNO₃. After preconcentration, the uranyl ions are eluted with 0.32?mol?L^?1HCl followed by reaction with 3,6-bis[(2-arsonophenyl)-azo]-4,5-dihydroxy-2,7-naphthalendisulfonic acid 0.08%[w/v] (Arsenazo III), which had maximum monitored absorbance of 650?nm. Effects of the pertinent experimental parameters on the system were investigated by means of 2^6?2 fractional factorial design, while optimization was carried out using the Doehlert matrix. Under optimized conditions, detection and quantification limits were found to be 0.21 and 0.7?µg?L^?1, respectively. The analytical curve ranged from 5 to 150?µg?L^?1 (r?=?0.998), while the relative standard deviations (RSD) were 3.27 and 2.56% for the respective uranium concentrations of 10 and 100?µg?L^?1 (n?=?10). The features obtained for the on-line preconcentration system were: preconcentration factor of 228, concentration efficiency of 57?min^?1, consumption index of 0.13?mL and sample throughput of 15?h^?1. In order to assess the accuracy of the proposed method, addition and recovery studies were carried out on spring water samples from different sources and synthetic seawater with satisfactory results ranging from 94.85 up to 103.65%.     

Bioleaching of UO22+ Ions from Poor Uranium Ores by Means of Cyanobacteria

The present paper deals with the study on uranium (VI) leaching, as uranyl ions, from ores with a poor content in util minerals, using some algae as: Porphyridium cruentum (Smith and Soerly) Nägeli, Spirulina platensis CNM-CB-02 and Nostoc linkia (Roth) Born and Flah. The basic composition of these ores allowed the self-maintenance and self-development of these microorganisms, which have facilitated then the leaching of the uranium (VI) as UO₂ ²⁺ ions. The microbial leaching degree was comprised between 40–90%, depending on the used alga and experimental conditions.     

Polysaccharides and sterols from green algae Caulerpa lentillifera and C. sertularioides

Sterols and polysaccharides of green alga Caulerpa lentillifera grown under laboratory conditions and in mariculture and polysaccharides of green alga C. sertularioides grown under natural conditions were studied. The sterol fraction consisted of C₂₇-C₂₉ steroidal alcohols with Δ⁵-unsaturation in the steroid core regardless of the growth conditions. The dominant (79.9%) steroid component of the sterol fraction was clionasterol. The water-soluble fraction of C. lentillifera grown under laboratory conditions was a mixture of 1,4-α- and 1,3-β-D-glucans and protein. The same fraction isolated from C. lentillifera grown in mariculture contained only protein. The water-soluble fraction of C. sertularioides grown under natural conditions contained 1,3;1,6-β-D-galactan sulfated at C2. The principal components of the base-soluble polysaccharide fractions from all algae samples were 1,4-α-D-glucans. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 5-8, January-February, 2009.     

Eicosapentaenoic acid release from the red alga Pachymeniopsis lanceolata by enzymatic degradation

Forty-eight species of seaweeds from Japanese waters were screened for the valuable polyunsaturated fatty acids eicosapentaenoic acid (EPA). The eight species that contained the highest levels of these compounds were analyzed in detail. Of all species tested the red alga Pachymeniopsis lanceolata contained the highest EPA concentration, and it was present as both the free and bound forms. EPA constituted 38.7% of total fatty acids, and polar lipids were the main constituent of the total lipids in P. lanceolata. EPA was obtained from the marine algae P. lanceolata by enzymatic hydrolysis of the total lipids extract using phospholipase A₂(PLA₂). The release of EPA reached a plateau after 10 min of enzymatic treatment. These results suggest that P. lanceolata is a useful natural source of EPA and that PLA₂ treatment is a convenient method for obtaining EPA from the red alga.     

Extrapolation studies on adsorption of thorium and uranium at different solution compositions on soil sediments

Study on adsorption of thorium and uranium radionuclides by a soil sediment as a function of ionic composition of Ca, Mg and Na has been carried out. Experimentally determined slopes represents an average of adsorption on soil sediments having different relative affinities for thorium, uranium, calcium and magnesium. Both thorium and uranium were found to be adsorbed to ion-exchange sites together with calcium and magnesium cations as effective competitors An extrapolated equation for the distribution coefficientK _d was formed for both radionuclides thorium and uranium at the specified site where the soil sediments were sampled. The combined cation concentration of both calcium and magnesium in solution correlates linearly with the measuredK _d ^Th,U values.     

Development of method for determination and preconcentration of uranium in water samples using XAD-4 resin loaded with Br-PADAP

In the present work, a minicolumn of XAD-4 loaded with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) is proposed as a preconcentration system for uranium determination in well, tap and mineral water samples by spectrophotometer using arsenazo III as the chromogenic reagent. Initially, a two-level (2³) full factorial design was used for the preliminary evaluation of three factors, involving the following variables: sampling flow rate, elution flow rate, and pH. This design has revealed that, for the studied levels, buffer concentration and pH were significant factors. When the experimental conditions established in the optimization step were pH = 8.6, and an elution flow rate of 8.6 mL min^?1 using 0.5% m/v ascorbic acid, this system has allowed for the determination of uranium with a detection limit (LOD) (3σ/S) of 0.05 μg L^?1 and a quantification limit (LOQ) (10σ/S) of 0.16 μg L^?1. The precision expressed as the relative standard deviation (R.S.D.) of 0.8% and 1.9% at 10.0 and 1.0 μg L^?1, respectively- and a preconcentration factor of 184.5 for a sample volume of 50.0 mL. Accuracy was confirmed by uranium determination in the standard reference material, NIST SRM 1566b trace element units in Oyster Tissue samples, and spike tests with recuperations ranging from 93.2 to 105%; the procedure were applied for uranium determination in tap water, well water, and drinking water samples collected from Caetité and Cruz das Almas Cities, Bahia, Brazil. Five water samples were analyzed the uranium concentrations varied from 0.50 to 2.07 μg L^?1