967 resultados para PURE WATER
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Spine title: Diversion of Sudbury River by the City of Boston.
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The behavior of monolayer films of free base 5,10,15,20-tetrapyridylporphinato (TPyP) and 5,10,15,20-tetrapyridylporphinato zinc(II) (ZnTPyP) on pure water, 0.1 M CdCl2, and 0.1 M CuCl2 subphases was investigated by surface pressure-area isotherms, specular X-ray reflectometry, and polarized total reflection X-ray absorption spectroscopy (PTRXAS). Surface pressure-area isotherms showed significant differences in the area per molecule on pure water compared to that on salt subphases, with a marked increase in the area observed on the salt solutions. This behavior was noted for both forms of the porphyrin and both salts investigated. Modeling of specular X-ray reflectometry data indicated that thinner and more electron dense layers on salt subphases best fit the observed profiles. These data suggest that the porphyrin macrocycle is oriented parallel to the interface on salt subphases and takes on a tilted conformation on pure water. In the case of ZnTPyP, PTRXAS was used to determine the orientation of the porphyrin moiety relative to the surface and to probe the coordination of the central Zn ion. In agreement with the pressure-area isotherms and reflectometry, the PTRXAS data indicate a change in orientation on the salt subphases.
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The literature on the evaporation of drops of pure liquids, drops containing solids and droplet sprays has been critically reviewed. An experimental study was undertaken on the drying of suspended drops of pure water and aqueous sodium sulphate decahydrate with concentrations varying from 5 to 54. 1 wt. %. Individual drops were suspended from a glass filament balance in a 26 mm I.D. vertical wind tunnel, designed and constructed to supply hot de-humidified air, to simulate conditions encountered in commercial spray driers. A novel thin film thermocouple was developed to facilitate the simultaneous measurement of drop weight and core temperature. The heat conduction through the thermocouple was reduced because of its unique design; using essentially a single 50μ diameter nickel wire. For pure water drops, the Nusselt number was found to be a function of the Reynolds, Prandtl and Transfer numbers for a temperature range between 19 to 79°C. Nu = 2 + 0.19 (1/B)0.24 Re0.5 Pr0.33 Two distinct periods were observed during the drying of aqueous sodium sulphate decahydrate. The first period was characterised by the evaporation from a free liquid surface, whilst drying in the second period was controlled by the crust resistance. Fracturing of the crust occurred randomly but was more frequent at higher concentrations and temperatures. A model was proposed for the drying of slurry drops, based on a receding evaporation interface. The model was solved numerically for the variation of core temperature, drop weight and crust thickness as a function of time. Experimental results were in excellent agreement with the model predictions although at higher temperatures modifications to the model had to be made to accommodate the unusual behaviour of sodium sulphate slurries, i.e. the formation of hydrates.
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The literature relating to the drying characteristics of pure liquid drops and particulate slurry drops has been reviewed. The experimental investigation was, therefore, divided into three parts: Pure water drops, Aqueous sodium sulphate decahydrate drops, and, Slurry drops from nine detergent formulations. The value of the constant,'Ψ, reported by Ranz and Marshall, was found to be temperature dependent. In the temperature range o 26.5≤T≤118.5°C,Ψ , for pure water drops, varied between 0.38 and 0.47. A revised correlation of the mass transfer coefficients is therefore proposed. A mathematical model for estimating the variation of crust thickness, for aqueous sodium sulphate drops, with time is proposed: β = R _ {R3 - ( 1.5G/πCo ) ( ΔHD - ΔHU) Δ} 1/3 Experimental crust thickness evaluated from stereoscan micrographs showed good agreement with theoretical prediction. It has been shown that drying characteristics of detergent drops can be evaluated from the porosity:thickness ratio, {ε/\β}. Formulations having large {ε/β I-ratios dry better than those with smaller values. The agreement between the experimental and theoretical mass transfer coefficients shows, in addition to the above correlation, that the overall mass transfer coefficient can be predicted from the expression1/K = 1/K + β/DMε 1.5 The crust is the controlling resistance to transfer in particulate slurry drops. For aqueous sodium sulphate drops, the crust provides 64.2% of the total resistance while for detergents with thicker, but less porous crusts, the value is 97.5%.
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The literature relating to evaporation from single droplets of pure liquids, and to the drying of droplets containing solids and of droplet sprays has been reviewed. The heat and mass transfer rates for a single droplet suspended from a nozzle were studied within a 42mm I.D. horizontal wind tunnel designed to supply hot dry air, to simulate conditions encountered in a practical spray dryer. A novel rotating glass nozzle was developed to facilitate direct measurements of droplet weight and core temperature. This design minimised heat conduction through the nozzle. Revised correlations were obtained for heat and mass transfer coefficients, for evaporation from pure water droplets suspended from a rotating nozzle. Nu = 2.0 + 0.27 (l/B)°-18Re°-5Pr°-83 Sh = 2.0 + 0.575 ((T0-T.)/Tomfc) -o.o4Reo.5 ^0.33 Experimental drying studies were carried out on single droplets of different types of skin-forming materials, namely, custard, gelatin, skim milk and fructose at air temperatures ranging from 19°C to 198°C. Dried crusts were recovered and examined by Scanning Electron Microscopy. Skin-forming materials were classified into three types according to the mechanisms of skin formation. In the first type (typified by droplets of custard and starch) skin formed due to gelatinisation at high temperatures. Increasing the drying temperature resulted in increased crust resistance to mass transfer due to increased granule swelling and the crust resistance was completely transferred to a skin resistance at drying temperatures > 150°C. In the second type e.g. gelatin droplets the skin formed immediately drying had taken place at any drying temperature. At drying temperature > 60° C a more resistant skin was formed. In the third type (typified by droplets of skim milk and fructose) the skin appeared on the droplet surface at a certain stage of the drying process under any drying conditions. As the drying temperature was increased the resistance of the skin to mass transfer increased. The drying rate history of any material depended upon the nature of the skin formed which, in turn, depended upon the drying conditions. A mathematical model was proposed for the drying of the first type of skin-forming material. This was based on the assumption that, once all the granules gelatinised at the gelatinisation temperature, a skin appeared instantaneously on the droplet surface. The experimentally-observed times at which the skin appeared on the droplets surfaces were in excellent agreement with those predicted from the model. The work should assist in understanding the fundamentals of paniculate drying processes, particularly when skin-formation occurs and may be a crucial factor in volatiles retention.
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The literature relating to evaporation from single droplets of pure liquids and the drying of solution and slurry droplets, and of droplet sprays has been reviewed. The heat and mass transfer rates for individual droplets suspended in free-flight, were investigated using a specially-designed vertical wind tunnel, to simulate conditions in a spray drier. The technique represented a unique alternative method for investigating evaporation from unrestrained single droplets with variable residence times. The experiments covered droplets of pure liquid allowbreak (water, isopropanol) allowbreak and of significantly different solutions (sucrose, potassium sulphate) over a range of temperatures of 37oC to 97oC, initial concentrations of 5 to 40wt/wt% , and initial drop sizes of 2.8 to 4.6mm. Drop behaviour was recorded photographically and dried particles were examined by Scanning Electron Microscopy. Correlations were developed for mass transfer coefficients for pure water droplets in free-flight; (i) experiencing oscillations, rotation and deformation, Sh = -105 + 3.9 [Ta - Td/Tamb]0.18Re0.5Sc033 for Re approx. > 1380 (ii) when these movements had ceased or diminished, Sh = 2.0 + 0.71 [Ta - Td/Tamb]0.18Re0.5Sc033 for Re approx. < 1060. Data for isopropanol drops were correlated resonably well by these equations. The heat transfer data showed a similar transition range. The drying rate curves for drops of sucrose and potassium sulphate solution exhibited three distinct stages; an initial increase in the drying rate as drop temperature reduced to the wet-bulb temperature, a short constant-rate period and a falling-rate period characterised by formation of a crust which controlled the mass transfer rate. Due to drop perturbation the rates in the high Re number region were up to 5 times greater than predicted from theory for spherical droplets. In the case of sucrose solution a `skin' formed over the drop surface prior to crust formation. This provided an additional resistance to mass transfer and resulted in extended drying times and a smooth crust of low porosity. The relevance of the results to practical spray drying operations is discussed.
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The literature pertaining to the key stages of spray drying has been reviewed in the context of the mathematical modelling of drier performance. A critical review is also presented of previous spray drying models. A new mathematical model has been developed for prediction of spray drier performance. This is applicable to slurries of rigid, porous crust-forming materials to predict trajectories and drying profiles for droplets with a distribution of sizes sprayed from a centrifugal pressure nozzle. The model has been validated by comparing model predictions to experimental data from a pilot-scale counter-current drier and from a full-scale co-current drier. For the latter, the computed product moisture content was within 2%, and the computed air exit temperature within 10oC of experimental data. Air flow patterns have been investigated in a 1.2m diameter transparent countercurrent spray tower by flow visualisation. Smoke was introduced into various zones within the tower to trace the direction, and gauge the intensity, of the air flow. By means of a set of variable-angle air inlet nozzles, a variety of air entry configurations was investigated. The existence of a core of high rotational and axial velocity channelling up the axis of the tower was confirmed. The stability of flow within the core was found to be strongly dependent upon the air entry arrangement. A probe was developed for the measurement of air temperature and humidity profiles. This was employed for studying evaporation of pure water drops in a 1.2m diameter pilot-scale counter-current drier. A rapid approach to the exit air properties was detected within a 1m distance from the air entry ports. Measured radial profiles were found to be virtually flat but, from the axial profiles, the existence of plug-flow, well-mixed-flow and some degree of air short-circuiting can be inferred. The model and conclusions should assist in the improved design and optimum operation of industrial spray driers.
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Contaminants of emerging concern (CECs) are continuously being released into the environment mainly because of their incomplete removal in the sewage treatment plants (STPs). The CECs selected for the study include antibiotics (macrolides, sulfonamides and ciprofloxacin), sucralose (an artificial sweetener) and dioctyl sulfosuccinate (DOSS, chemical dispersant used in the Deepwater Horizon oil spill). After being discharged into waterways from STPs, photo degradation is a key factor in dictating the environmental fate of antibiotics and sucralose. Photodegradation efficiency depends on many factors such as pH of the matrix, matrix composition, light source and structure of the molecule. These factors exert either synergistic or antagonistic effects in the environment and thus experiments with isolated factors may not yield the same results as the natural environmental processes. Hence in the current study photodegradation of 13 CECs (antibiotics, sucralose and dicotyl sulfosuccinate) were evaluated using natural water matrices with varying composition (deionized water, fresh water and salt water) as well as radiation of different wavelengths (254 nm, 350 nm and simulated solar radiation) in order to mimic natural processes. As expected the contribution of each factor on the overall rate of photodegradation is contaminant specific, for example under similar conditions, the rate in natural waters compared to pure water was enhanced for antibiotics (2-11 fold), significantly reduced for sucralose (no degradation seen in natural waters) and similar in both media for DOSS. In general, it was observed that the studied compounds degraded faster at 254 nm, while when using a simulated sunlight radiation the rate of photolysis of DOSS increased and the rates for antibiotics decreased in comparison to the 350 nm radiation. The photo stability of the studied CECs followed the order sucralose > DOSS > macrolides > sulfonamides > ciprofloxacin and a positive relationship was observed between photo stability and their ubiquitous presence in natural aquatic matrices. An online LC-MS/MS method was developed and validated for sucralose and further applied to reclaimed waters (n =56) and drinking waters (n = 43) from South Florida. Sucralose was detected in reclaimed waters with concentrations reaching up to 18 μg/L. High frequency of detection (> 80%) in drinking waters indicate contamination of ground waters in South Florida by anthropogenic activity.^
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This study aimed mainly to evaluate the influence of xanthan gum (XG) and carboxymethylcellulose (CMC) in the filtration process of water-based drilling fluids, considering the conformational changes suffered by the polyelectrolyte with the addition of sodium chloride (NaCl) in different concentrations (0.17, 0.34 and 0.51 mol.L-1). It was also evaluated the behavior of the fluid by the addition of calcium carbonate (CaCO3) in pure water and in brine. Seeking a better understanding of the interaction between the polymers used and CaCO3, polymer adsorption analyzes were performed using a depletion method, which yielded a higher percentage of adsorption of Xanthan Gum in this material (29%), which can justify the formation of a thin and waterproof filter cake for drilling fluids containing this polymer. However, the best values of apparent viscosity (20 and 24 mPa.s) and volume of filtrate (8.0 and 8.1 mL) were obtained for the systems consisting of xanthan gum, CMC and CaCO3, in NaCl aqueous solutions concentrations of 0.34 and 0.51 mol.L-1, respectively. The values can be related to the presence of CMC that increases the apparent viscosity and reduces the volume of filtrate. In addition, the CaCO3 added acts as a bridging agent, promoting the formation of a less permeable filter cake
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Light hydrocarbon (C1-C8) profiles are compared for three wells of varying maturities: two immature DSDP wells (Site 397 near the Canary Islands and Site 530A near the Walvis Ridge in the south-east Atlantic) and a mature well, the East Cameron well in the Texas Gulf Coast. Primary migration of C1 and C2 appears to be occurring in all of the sedimentary rocks examined. Primary migration of C3+ components becomes important only as fine-grained sedimentary rocks enter the catagenetic hydrocarbon generation zone or over short distances in more permeable sections. Lateral migration along bedding planes was more important than vertical migration in sedimentary rocks of all maturities. The lightest (methane, ethane and propane gases) hydrocarbon show greater fractionation than do the C4-C8 alkanes which generally show minimal fractionation during the migrational process. Subsurface diffusion coefficients for these p.p.b. quantities of C2-C5 alkanes from immature sediments from DSDP Site 530 are estimated to be several orders of magnitude less than values reported in the literature for diffusion of much larger amounts of these compounds from mature water wet sediments into air or sandstones. Since our calculations suggest light hydrocarbons are present in amounts less than their reported solubilities in pure water at 25°C, we postulate that the sediment organic matter has a substantial effect on retarding the movement of these light hydrocarbons.
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For the SNO+ neutrinoless double beta decay search, various backgrounds, ranging from impurities present naturally to those produced cosmogenically, must be understood and reduced. Cosmogenic backgrounds are particularly difficult to reduce as they are continually regenerated while exposed to high energy cosmic rays. To reduce these cosmogenics as much as possible the tellurium used for the neutrinoless double beta decay search will be purified underground. An analysis of the purification factors achievable for insoluble cosmogenic impurities found a reduction factor of $>$20.4 at 50\% C.L.. During the purification process the tellurium will come into contact with ultra pure water and nitric acid. These liquids both carry some cosmogenic impurities with them that could be potentially transferred to the tellurium. A conservative limit is set at $<$18 events in the SNO+ region of interest (ROI) per year as a result of contaminants from these liquids. In addition to cosmogenics brought underground, muons can produce radioactive isotopes while the tellurium is stored underground. A study on the rate at which muons produce these backgrounds finds an additional 1 event per year. In order to load the tellurium into the detector, it will be combined with 1,2-butanediol to form an organometallic complex. The complex was found to have minimal effect on the SNO+ acrylic vessel for 154 years.
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Uusiutuvan energian käytön lisääntyminen lisää sähkön varastoinnin tarvetta. Litiumioniakku-jen on todettu olevan oivallisia keinoja varastoida sähköä esimerkiksi sähköautojen energian-lähteeksi. Tästä syystä akkujen kysyntä kasvaa nopeaa tahtia, jolloin nykyiset litiumlähteet ei-vät enää riitä tuottamaan tarpeeksi litiumia kasvavaan tarpeeseen. Tämän vuoksi litiumin tal-teenottoon tulee valjastaa uusia litiumin lähteitä, joiden hyödynnettävyys nykyisellä tekniikalla on pienen litiumkonsentraation ja muiden alkali- ja maa-alkalimetallien läsnäolon takia vaikeaa. Tällä hetkellä litiumia otetaan talteen eniten korkean litiumpitoisuuden luonnon suolajärvistä. Nykyisin käytössä oleva litiumin erotusprosessi on hidas ja sen käyttö pienten litiumkonsent-raatioiden suola-altailla on kannattamatonta. Tehokkaampana talteenottomenetelmänä luonnon suolajärvillä nähdään litiumin selektiivinen uutto ionisilla nesteillä. Menetelmä on todettu toi-mivaksi suolajärvillä, joilla on matala litiumkonsentraatio. Uusien suolajärvien käyttöönotto ei ratkaise kaikkia litiumin talteenottoon liittyviä ongelmia, sillä suolajärvet ovat alttiita ilmastonmuutokselle, eikä niiden litiumvarannot ole ehtymättömät. Merien litiumvarantoja sen sijaan pidetään lähes ehtymättöminä. Litiumin talteenotto meristä on mahdollista ionisia nesteitä ja membraaneja hyödyntävällä elektrodialyysilaitteistolla, jolla litiumia voidaan ottaa talteen myös hyvin pienistä pitoisuuksista. Lisäksi on mahdollista, että litiumin talteenottoon yhdistetään juomaveden valmistus. Tällainen vedenpuhdistusprosessi olisi myös hyvä kestävän kehityksen näkökulmasta.
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Tämän työn tavoitteena oli selvittää, kuinka selluloosan lisääminen vaikuttaa polysulfonirunkoisiin membraaneihin. Lisäksi työssä selvitettiin selluloosamembraanien modifiointia kitosaanilla ja bentoniitilla. Työssä muodostettiin membraanit faasi-inversiotekniikalla. Selluloosamembraanien valmistuksessa jauhettu selluloosa liuotettiin ioniseen nesteeseen. Sekä polysulfonista että selluloosasta valmistetuille membraaneille määritettiin puhdasvesivuot ja retentiot. Retention määrittämiseen käytettiin malliaineena dekstraanin vesiliuosta. Lisäksi määriteltiin polysulfonipohjaisten membraanien hydrofiilisyys tutkimalla membraanien pintojen ja vesipisaroiden välisiä kontaktikulmia. Polysulfonimembraaneihin lisätyn selluloosan havaittiin pienentävän puhdasvesivuota ja kasvattavan hydrofiilisyyttä mitä enemmän selluloosaa oli membraanimatriisissa. Kaikkien selluloosalla modifioitujen membraanien retentiot olivat suurempia kuin modifioimattoman polysulfonimembraanin. Kitosaanilla modifioitujen selluloosamembraanien valmistus ei onnistunut johtuen luultavasti kitosaanin liian suuresta partikkelikoosta. Bentoniitilla modifioitujen membraanien vuot olivat merkittävästi suuremmat sekä niiden retentiot pienemmät verrattuna modifioimattomaan selluloosamembraaniin. Tämä johtui luultavasti siitä, että bentoniitin lisääminen aiheutti membraanirakenteeseen reikiä.
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The ongoing depletion of fossil fuels and the severe consequences of the greenhouse effect make the development of alternative energy systems crucially important. While hydrogen is, in principle, a promising alternative, releasing nothing but energy and pure water. Hydrogen storage is complicated and no completely viable technique has been proposed so far. This work is concerned with the study of one potential alternative to pure hydrogen: ammonia, and more specifically its storage in solids. Ammonia, NH3, can be regarded as a chemical hydrogen carrier with the advantages of strongly reduced flammability and explosiveness as compared to hydrogen. Furthermore, ammine metal salts presented here as promising ammonia stores easily store up to 50 wt.-% ammonia, giving them a volumetric energy density comparable to natural gas. The model system NiX2–NH3 ( X = Cl, Br, I) is studied thoroughly with respect to ammine salt formation, thermal decomposition, air stability and structural effects. The system CuX2–NH3 ( X = Cl, Br) has an adverse thermal decomposition behaviour, making it impractical for use as an ammonia store. This system is, however, most interesting from a structural point of view and some work concerning the study of the structural behaviour of this system is presented. Finally, close chemical relatives to the metal ammine halides, the metal ammine nitrates are studied. They exhibit interesting anion arrangements, which is an impressive showcase for the combination of diffraction and spectroscopic information. The characterisation techniques in this thesis range from powder diffraction over single crystal diffraction, spectroscopy, computational modelling, thermal analyses to gravimetric uptake experiments. Further highlights are the structure solutions and refinements from powder data of (NH4)2[NiCl4(H2O)(NH3)] and Ni(NH3)2(NO3)2, the combination of crystallographic and chemical information for the elucidation of the (NH4)2[NiCl4(H2O)(NH3)] formation reaction and the growth of single crystals under ammonia flow, a technique allowing the first documented successful growth and single crystal diffraction measurement for [Cu(NH3)6]Cl2.
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Interaction of rocks with fluids can significantly change mineral assemblage and structure. This so-called hydrothermal alteration is ubiquitous in the Earth’s crust. Though the behavior of hydrothermally altered rocks can have planet-scale consequences, such as facilitating oceanic spreading along slow ridge segments and recycling volatiles into the mantle at subduction zones, the mechanisms involved in the hydrothermal alteration are often microscopic. Fluid-rock interactions take place where the fluid and rock meet. Fluid distribution, flux rate and reactive surface area control the efficiency and extent of hydrothermal alteration. Fluid-rock interactions, such as dissolution, precipitation and fluid mediated fracture and frictional sliding lead to changes in porosity and pore structure that feed back into the hydraulic and mechanical behavior of the bulk rock. Examining the nature of this highly coupled system involves coordinating observations of the mineralogy and structure of naturally altered rocks and laboratory investigation of the fine scale mechanisms of transformation under controlled conditions. In this study, I focus on fluid-rock interactions involving two common lithologies, carbonates and ultramafics, in order to elucidate the coupling between mechanical, hydraulic and chemical processes in these rocks. I perform constant strain-rate triaxial deformation and constant-stress creep tests on several suites of samples while monitoring the evolution of sample strain, permeability and physical properties. Subsequent microstructures are analyzed using optical and scanning electron microscopy. This work yields laboratory-based constraints on the extent and mechanisms of water weakening in carbonates and carbonation reactions in ultramafic rocks. I find that inundation with pore fluid thereby reducing permeability. This effect is sensitive to pore fluid saturation with respect to calcium carbonate. Fluid inundation weakens dunites as well. The addition of carbon dioxide to pore fluid enhances compaction and partial recovery of strength compared to pure water samples. Enhanced compaction in CO2-rich fluid samples is not accompanied by enhanced permeability reduction. Analysis of sample microstructures indicates that precipitation of carbonates along fracture surfaces is responsible for the partial restrengthening and channelized dissolution of olivine is responsible for permeability maintenance.