Letteratura scientifica selezionata sul tema "Speciation at equilibrium"
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Articoli di riviste sul tema "Speciation at equilibrium":
1
Chen, Min, e R. Stephen Reid. "Solution speciation in the aqueous Na(I)–EDTA and K(I)–EDTA systems". Canadian Journal of Chemistry 71, n. 5 (1 maggio 1993): 763–68. http://dx.doi.org/10.1139/v93-100.
Abstract (sommario):
Speciation in the aqueous sodium(I) – ethylenediaminetetraacetic acid and potassium(I) – ethylenediaminetetraacetic acid equilibrium systems was investigated by automated gravimetric potentiometric titration. It was found that in both cases, particularly below neutral pH values, speciation includes a previously uncharacterized diprotonated complex. All formation and acid dissociation constants were measured for the full systems. The validity of previous literature equilibrium constants, which are based on incomplete equilibrium models, is discussed.
2
Filella, Montserrat, e Peter M. May. "The aqueous chemistry of tellurium: critically-selected equilibrium constants for the low-molecular-weight inorganic species". Environmental Chemistry 16, n. 4 (2019): 289. http://dx.doi.org/10.1071/en19017.
Abstract (sommario):
Environmental contextEquilibrium constants are required in many scientific disciplines such as biology, medicine, engineering, and in particular chemistry. Lack of reliable equilibrium constants for tellurium has restricted our understanding of its speciation and behaviour in the environment. This study presents a reliable set of equilibrium constants for tellurium, thereby providing a more coherent basis for future experimental investigations of the geochemistry, biochemistry and toxicology of this element. AbstractRelatively little information is available in the literature regarding the speciation and solubility of tellurium in aqueous solutions. The available thermodynamic data have been critically evaluated and entered into a thermodynamic database. The Joint Expert Speciation System suite of computer programs has been used to achieve thermodynamic consistency and provide a critically-selected set of equilibrium constants that can later be used for modelling purposes.
3
Arp, Paul A., e Rock Ouimet. "Aluminum speciation in soil solutions: Equilibrium calculations". Water, Air, & Soil Pollution 31, n. 1-2 (1986): 359–66. http://dx.doi.org/10.1007/bf00630852.
4
Harris, W. R. "Equilibrium Model for Speciation of Aluminum in Serum". Clinical Chemistry 38, n. 9 (1 settembre 1992): 1809–18. http://dx.doi.org/10.1093/clinchem/38.9.1809.
Abstract (sommario):
Abstract An equilibrium model for the speciation of Al3+ in normal serum has been developed in which 81% of the aluminum is bound to transferrin. The remaining 19% exists primarily as Al(PO4)(OH)-, with minor amounts of citrate and hydroxide species. The model meets several key criteria. The concentration of free aluminum is below the upper limit set by the solubility product of aluminum phosphate. The fraction of low-molecular-mass aluminum species agrees with experimental studies on the fraction of ultrafiltrable aluminum in both normal and uremic serum. Lastly, the model accounts for the relative effectiveness of EDTA, citrate, and desferrioxamine B for binding aluminum in serum by including competition from zinc, magnesium, and calcium for these ligands. Uncertainties in the available thermodynamic database are discussed.
5
Marang, Laura, Pascal Reiller, Monique Pepe e Marc F. Benedetti. "Donnan Membrane Approach: From Equilibrium to Dynamic Speciation". Environmental Science & Technology 40, n. 17 (settembre 2006): 5496–501. http://dx.doi.org/10.1021/es060608t.
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Wang, Peiming, Jerzy J. Kosinski, Malgorzata M. Lencka, Andrzej Anderko e Ronald D. Springer. "Thermodynamic modeling of boric acid and selected metal borate systems". Pure and Applied Chemistry 85, n. 11 (1 novembre 2013): 2117–44. http://dx.doi.org/10.1351/pac-con-12-07-09.
Abstract (sommario):
A comprehensive thermodynamic model, referred to as the mixed-solvent electrolyte (MSE) model, has been applied to calculate phase equilibria, speciation, and other thermodynamic properties of selected systems that are of interest for understanding the chemistry of salt lakes and natural waters. In particular, solubilities and chemical speciation have been analyzed for various boron-containing systems, which represent an important subset of solution chemistry for such applications. The model has been shown to reproduce the speciation, solubility, and vapor–liquid equilibrium (VLE) data in the boric acid + water system over wide ranges of temperature and concentration. Specifically, solubilities have been accurately represented in the full concentration range of the B2O3 + H2O system (xB2O3 = 0~1), which includes H3BO3. The accuracy of the model has also been demonstrated by calculating solubilities in various aqueous borate systems, i.e., MnO + B2O3 + H2O (where M = Li, Na, Ca, Mg), and their mixtures with a chloride salt or an acid (i.e., LiCl, NaCl, HCl). The model predicts the effects of chemical speciation, temperature, and concentrations of various acid, base, and salt components on the formation of competing solid phases.
7
Halstensen, Maths, Henrik Jilvero, Wathsala N. Jinadasa e Klaus-J. Jens. "Equilibrium Measurements of the NH3-CO2-H2O System: Speciation Based on Raman Spectroscopy and Multivariate Modeling". Journal of Chemistry 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/7590506.
Abstract (sommario):
Liquid speciation is important for reliable process design and optimization of gas-liquid absorption process. Liquid-phase speciation methods are currently available, although they involve tedious and time-consuming laboratory work. Raman spectroscopy is well suited for in situ monitoring of aqueous chemical reactions. Here, we report on the development of a method for speciation of the CO2-NH3-H2O equilibrium using Raman spectroscopy and PLS-R modeling. The quantification methodology presented here offers a novel approach to provide rapid and reliable predictions of the carbon distribution of the CO2-NH3-H2O system, which may be used for process control and optimization. Validation of the reported speciation method which is based on independent, known, NH3-CO2-H2O solutions shows estimated prediction uncertainties for carbonate, bicarbonate, and carbamate of 6.45 mmol/kg H2O, 34.39 mmol/kg H2O, and 100.9 mmol/kg H2O, respectively.
8
Heck, R. J., e A. R. Mermut. "The chemistry of saturation extracts of Solonetzic and associated soils". Canadian Journal of Soil Science 72, n. 1 (1 febbraio 1992): 43–56. http://dx.doi.org/10.4141/cjss92-005.
Abstract (sommario):
Cation speciation in soil extracts from a catenary sequence of salt-affected soils was studied to understand the chemical evolution of Solonetzic soils in a closed basin. Major changes in cation speciation were found to occur at each phase of soil development. The proportion of thermodynamically active cations was greater in the extracts from the more leached profiles. Saturation indices suggested that the extracts achieved equilibrium with calcite and gypsum, when present in the soil, within 24 h. Accumulations and/or losses of gypsum and calcite from saline layers indicate that there are ongoing changes in their stability. The ratio of Ca2+/Mg2+ suggested a possible equilibrium with Mg-bearing calcites; conditions existed in certain horizons for the formation of this group of minerals. Correlations between exchangeable sodium ratios and sodium adsorption ratios calculated using cation concentration and activity were similar; however, using activities to determine the exchange constants resulted in significant differences.Key words: Cation speciation, saturation indices, cation adsorption, exchange selectivity constants, Solonetzic soils
9
Fitzgerald, John, Colton Bentley e Bas Vriens. "Geochemical Equilibrium Modelling of the Aqueous Speciation of Select Trace Elements in the Great Lakes". Water 15, n. 8 (11 aprile 2023): 1483. http://dx.doi.org/10.3390/w15081483.
Abstract (sommario):
The behaviour and fate of trace elements in surface waters are greatly affected by their chemical form in solution, but the aqueous speciation of dissolved trace elements in the North American Great Lakes has received relatively little attention. Here, we present results from geochemical equilibrium modelling with 2021 surface water quality data to examine the spatiotemporal dynamics of trace element speciation in the Great Lakes. The relative abundance of aqueous trace element species appeared consistent with variability in solution chemistry and followed basin-wide trends in pH, alkalinity, salinity, and nutrient levels. The speciation of alkali metals was dominated by free monovalent cations, and that of oxyanion-forming elements by oxoacids, whereas significant fractions (>1%) of other aqueous complexes were also evident for rare earth elements (e.g., Ce and Gd as carbonates), alkaline earth metals (e.g., Sr as sulfates), or transition metals (e.g., Zn as phosphates). Spatially, differences in the relative abundance of aqueous trace element species were <2 orders of magnitude, with the highest variation (~50-fold) occurring for select chloride-complexes, resulting from upstream-to-downstream salinity increases in the basin. Finally, simulations of various future water quality scenarios (e.g., decreasing P levels, increasing temperature and salinity) suggest that the speciation of most trace elements is robust temporally as well. This study demonstrates how considering aqueous speciation may help improve the understanding of trace element dynamics and support water quality management in the Great Lakes.
10
Smith, Bradley J., e Vincent A. Patrick. "Quantitative Determination of Aqueous Dodecatungstophosphoric Acid Speciation by NMR Spectroscopy". Australian Journal of Chemistry 57, n. 3 (2004): 261. http://dx.doi.org/10.1071/ch02037.
Abstract (sommario):
The speciation and equilibria during base decomposition of α-[PW12O40]3– have been determined using 31P and 183W NMR spectroscopy over the pH range 0.7–13.5. NMR spectroscopy was used to directly observe the polytungstate species in aqueous solution at high concentration (0.25 mol L–1) and follows the progressive decomposition of [PW12O40]3– to WO42– and PO43–. It was found unexpectedly in the pH range 1.2–2.3 that [PW12O40]3– did not decompose directly to [PW11O39]7– but first formed an equilibrium with [P2W18O62]6–, [P2W21O71]6–, and some new, stable, intermediate species before converting into α-[PW11O39]7–.
Tesi sul tema "Speciation at equilibrium":
1
Wardle, Brian. "Equilibrium speciation modelling of copper in sea water". Thesis, Manchester Metropolitan University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336493.
2
Sjöstedt, Carin. "Iron and aluminium speciation in Swedish freshwaters : Implications for geochemical modelling". Doctoral thesis, KTH, Miljögeokemi och ekoteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-94528.
Abstract (sommario):
Speciation governs transport and toxicity of trace metals and is important to monitor in natural waters. Geochemical models that predict speciation are valuable tools for monitoring. They can be used for risk assessments and future scenarios such as termination of liming. However, there are often large uncertainties concerning the speciation of iron and aluminium in the models, due to the complicated chemistry of these metals. Both are important in governing the speciation of other metals, due to (i) their capacity to form minerals onto which metals can adsorb and (ii) their ability to compete for binding sites to natural organic matter (NOM). Aluminium is also potentially toxic and is therefore closely monitored in acidified freshwaters. In this study different phases of iron in Swedish lakes were characterised. This required a good method for preconcentrating the iron colloids. A new method was developed in this thesis that uses an anion-exchange column to isolate the iron colloids prior to characterisation with extended X-ray absorption fine structure (EXAFS) spectroscopy. Iron was present as ferrihydrite in particles but was also strongly monomerically complexed to NOM in two Swedish lakes. Based on the results an internally consistent process-based geochemical equilibrium model was presented for Swedish freshwaters. The model was validated for pH (n = 9 400) and inorganic monomeric aluminium (Ali) (n = 3 400). The model could simulate pH and Ali simultaneously, and be used for scenario modelling. In this thesis, modelling scenarios for decreases and complete termination of liming are presented for the 3 000 limed Swedish lakes. The results suggest that liming can be terminated in 30 % of the Swedish lakes and decreased in many other lakes.QC 20120919
3
Monroe, Melanie. "The tempo and mode of evolution : a neontological reappraisal". Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-49761.
Abstract (sommario):
The theory of “punctuated equilibrium” suggests that species evolve rapidly during or immediately upon speciation, “punctuating” long periods of little or no morphological evolution. Here I confirm that body size differences within clades of birds and mammals are best explained using a model of punctuated evolution. This allows me to suggest that rates of speciation and extinction are responsible for why there are more small mammals than large, as large mammals likely speciate and go extinct at a higher rate than small mammals, and hence undergo cladogenetic change more often. Likewise, mammals appear to evolve at a higher rate than birds, because mammals, as a whole, speciate and go extinct at a higher rate than birds. Furthermore I show that mass extinctions and competition, i.e. forms of natural selection, do not seem to explain differences in body size between species on a macroevolutionary scale. Taken together, these findings not only contradict the idea that apparently different rates of evolution are due to differential selection intensities, and emphasize the importance of the speciation process in evolution, but raise the intriguing question as to what limits evolution in established species. Here I suggest that phenotypic traits, dependent on one another for development and/or function may constrain evolution by exerting stabilizing selection from within the organism, as opposed to external environmental selection, which has been the main focus of evolutionary studies thus far.Teorin om "punkterad jämvikt" säger att arter utvecklas snabbt under och omedelbart efter artbildning, vilket "punkterar" långa perioder med lite eller ingen morfologisk föränding. I den här avhandlingen visar jag att skillnader i kroppsstorlek inom klader (grupp med gemensam förfader) hos fåglar och däggdjur förklaras bäst när man använder en modell med punkterad evolution. Detta gör i sin tur att jag kan föreslå att hastigheten var med artbildning och utdöende sker, förklarar varför det finns fler små däggdjur än stora, eftersom stora däggdjur sannolikt bildar nya arter och dör ut med en högre hastighet än små däggdjur. Likaså förefaller däggdjur i sin helhet att evolvera med en högre hastighet än fåglar, detta eftersom däggdjur bildar nya arter och dör ut med en högre hastighet än fåglar. Dessutom visar jag att massutdöenden och konkurrens (naturlig selektion) inte verkar förklara skillnader mellan arter över makroevolutionära skalor (över geologisk tid). Sammantaget motsäger dessa resultat inte bara idén om att skenbart olika hastighet på evolution främst beror på skillnader i selektionstryck utan understryker också vikten av artbildningsprocessen som en viktig faktor som styr evolutionens hastighet. Dessutom leder dessa resultat till frågan om vad som begränsar evolutionen hos redan etablerade arter. Här föreslår jag att fenotypiska karaktärsdrag som är beroende av varandra för sin funktion och utveckling kan begränsa evolutionen genom att utöva stabiliserande selektion inifrån organismen, i motsats till selektion från den omgivande miljön vilket har varit fokus för de flesta evolutionära studier hittills.
4
Benavente, Martha. "Adsorption of Metallic Ions onto Chitosan : Equilibrium and Kinetic Studies". Licentiate thesis, Stockholm : Kemiteknik, Chemical and Engineering and Technology, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4746.
5
Bokma, F. (Folmer). "Why most birds are small – a macro-ecological approach to the evolution of avian body size". Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514273451.
Abstract (sommario):
Abstract There are more small-bodied species of birds than those having large bodies. Generally, and relative to occurrance in any one place, small-bodied species also contain more individuals than large-bodied species. The same patterns have been documented for several groups of higher organisms for example, snakes, flowering plants and mammals, which suggests that there exists a general reason "why", which applies to other groups of species as well as to birds. This thesis attempts to identify this reason. In the first place, it is possible that most species happened to become small-bodied by chance. Simulations of neutral body-size evolution indicate however that the observed bias towards small size is stronger than that accounted for by neutral evolution. Then, the most plausible explanation for why most species are small is that small-bodied species speciate faster. However, statistical analyses accounting for historical relatedness of present-day species indicate no relation between body size and the rate of speciation. Finally, instead of little by little, the dominance of small species may have arisen suddenly, when approximately 65 million years ago (presumably) a large meteorite hit the earth, causing mass extinctions. However, analysis of body sizes and genetic differences of extant species reveals that while avian species numbers were approximately halved, the catastrophe affected small and large species equally. Thus, the reason why most species are small does not seem to be due to differential rates of speciation or extinction. Instead, the cause appears to be in the tempo and mode of evolution. It was found by analysis of extant species' body size that probably most differences in body size between species arise at the moment of speciation. Differences between small-bodied species are smaller than between large-bodied species and probably this difference also has its origin at the moment of speciation. Consequently, groups of small species stay small whereas groups of large species are more variable in body size, so that in the end most species are smallTiivistelmä Maailman noin 10 000 lintulajin joukossa pienikokoisia lajeja on enemmän kuin suurikokoisia. Yleensä pienkokoiset lajit ovat myös yksilömääriltään suurempia kuin samalla paikalla esiintyvät suurikokoiset lajit. Koska sama ilmiö on havaittu monissa muissa suurissa eliöryhmissä (esim. nisäkkäät, käärmeet ja kukkakasvit), on ilmeistä, että on olemassa yhteinen syy, joka pätee niin linnuissa kuin muissakin eliöryhmissä. Tämän väitöskirjan tavoite on selvittää, mikä tämä yhteinen syy voisi olla. Ensinnäkin on mahdollista, että suurin osa lajeista on kehittynyt pienikokoisiksi aivan sattumalta. Ruumiin koon evoluution simulaatiot kuitenkin osoittavat, että on hyvin epätodennäköistä, että neutraali evoluutio olisi johtanut pienikokoisten lajien suuriin määrään havaitussa määrin. Toinen mahdollinen selitys ilmiölle on, että pienikokoiset lajit lajiutuvat nopeammin. Tilastolliset analyysit, jotka ottavat huomioon nykyisin elävien lajien sukulaisuussuhteet, osoittavat ettei ruumin koon ja lajiutumisen vauhdin välillä ole yhteyttä. Kolmas mahdollinen selitys pienikokoisten lajien suurelle määrällä on historiallinen. On mahdollista, että pienikokoisten lajien suhteellisen suuri määrä syntyi nopeasti noin 65 miljoonaa vuotta sitten tapahtuneen massasukupuuton seurauksena, joka fossiiliaineiston perusteella kohdistui erityisesti suurikokoisiin maaeläimiin (esimerkiksi dinosauruksiin). Vertaileva analyysi nykyään elävien lintulajien ruumiin koosta ja geneettisistä eroista osoittaa, että vaikka suuri osa lintulajeista hävisi massasukupuutossa, tämä katastrofi karsi lajeja riippumatta niiden ruumiin koosta. Näyttää siis siltä, etteivät erot lajiutumisen tai sukupuuttojen esiintymisessä selitä sitä, että suurin osa lajeista on pienikokoisia. Tämän tutkimuksen tulosten perusteella syy näyttäisi sen sijaan olevan ruumiin koon kehityksen vauhdissa ja siinä tavassa, jolla kehitys yleensä etenee. Analyysi nykyisten lajien ruumiin koosta paljasti, että suurin osa eroista lajien välillä syntyy (evolutiiviessa aikataulussa) suhteellisen nopeasti lajiutumistapahtuman yhteydessä (punktualismi) eikä vähitellen pitkien aikojen kuluessa (gradualismi), kuten yleensä oletetaan. Kehityslinjojen sisällä pienikokoisten lajien väliset erot ruumiin koossa olivat pienempiä kuin isokokoisten lajien väliset erot - ja todennäköisesti myöskin tämä ero syntyy lajiutumisen yhteydessä. Tämä johtaa evoluution kuluessa tilanteeseen, että alunperin pienikokoisista lajeista kehittyneet lajit ovat myös pienikokoisia, kun taas isokokoisten lajien kehityslinjoissa on nähtävissä huomattavasti paljon enemmän vaihtelua ruumiin koossa. Näiden seurauksena eliöstöissä suurin osa lajeista lopulta on pienikokoisia
6
Gorzsás, András. "Vanadate and Peroxovanadate Complexes of Biomedical Relevance : A speciation approach with focus on diabetes". Doctoral thesis, Umeå University, Chemistry, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-489.
Abstract (sommario):
Diabetes mellitus is one of the most threatening epidemics of modern times with rapidly increasing incidence. Vanadium and peroxovanadium compounds have been shown to exert insulin–like actions and, in contrast to insulin, are orally applicable. However, problems with side–effects and toxicity remain. The exact mechanism(s) by which these compounds act are not yet fully known. Thus, a better understanding of the aqueous chemistry of vanadates and peroxovanadates in the presence of various (bio)ligands is needed.
The present thesis summarises six papers dealing mainly with aqueous speciation in different vanadate – and peroxovanadate – ligand systems of biological and medical relevance. Altogether, five ligands have been studied, including important blood constituents (lactate, citrate and phosphate), a potential drug candidate (picolinic acid), and a dipeptide (alanyl serine) to model the interaction of (peroxo)vanadate in the active site of enzymes. Since all five ligands have been studied both with vanadates and peroxovanadates, the number of systems described in the present work is eleven, including the vanadate – citrate – lactate mixed ligand system. The pH–independent formation constants have been determined for 33 ternary vanadate – ligand, 41 quaternary peroxovanadate – ligand and two vanadate – mixed ligand species in addition to the pKa values of all five ligands. These constants have been used to model physiological conditions, and the biomedical relevance of the different species is discussed.
The studies have been performed at 25 ºC in the physiological medium of 0.150 M Na(Cl), i.e. the ionic strength of human blood. No buffers have been used, and wide pH–ranges have usually been covered. The applied experimental techniques comprise mostly 51V NMR and potentiometry, but 31P, 13C, 1H and 14N NMR as well as EPR and ESI–MS have also been used to gain additional information. Multimethod data have been treated by the least–squares program LAKE and modelling has been carried out by the software package WinSGW.
Whenever possible, solution structures of the species have been proposed. In addition, simple biological tests have been carried out to determine the stability of the formed peroxovanadate complexes in the presence of human catalase. A brief comparison is given of the different vanadate – ligand and peroxovanadate – ligand systems with emphasis on observed trends and general features.
7
Olds, William. "Lignite Derived Humic Substances for Treatment of Acid Mine Drainage". Thesis, University of Canterbury. Civil and Natural Resources, 2011. http://hdl.handle.net/10092/6583.
Abstract (sommario):
Addition of alkalinity to acid mine drainage (AMD) results in the neutralisation of acidity and precipitation of dissolved metals as insoluble hydroxides. Two aspects of the current AMD treatment practice at the Stockton Mine could be enhanced. Firstly, residual water quality may be poor due to unreacted alkalinity reagents, particularly CaCO3, resulting in poor water clarity and elevated suspended solids (SS). Secondly, neutralisation to circum-neutral pH may not avoid the discharge of residual metals (Ni and Zn) due to incomplete adsorption and hydroxide precipitation.
The aim of this project was to enhance the conventional neutralisation of AMD through addition of humic substances (HS) to reduce residual SS and trace metal concentrations. Humic substances are organically derived and have a high molecular weight. Functional groups on the surface of HS are capable of binding dissolved metals, forming HS-metal complexes. Incorporation of HS complexed metals into settling floc could result in increased metal removal from the dissolved phase.
Modified jar testing was used to investigate the effects of HS addition before, after and during (pH 4.5) neutralisation of AMD in two treatment scenarios at the Stockton Mine; the Blackwater Treatment Plant (BTP) using NaOH and Ca(OH)2 and the Mangatini Stream-sump System (MSS) using CaCO3. Supernatant samples collected during the sedimentation period were analysed for basic water quality parameters (turbidity and suspended solids) and dissolved (< 0.45 µm) metal concentrations.
The addition of HS to the BTP process before (pH 2.8) and during (pH 4.5) neutralisation resulted in HS precipitation. Precipitated HS subsequently acted as a nucleation site, triggering flocculation of precipitating metal hydroxides, resulting in low turbidity and suspended solids (SS) of less than 2 NTU and 5 mg/L, respectively. The addition of HS after neutralisation (pH 7) did not result in HS precipitation. Intermolecular bridging of HS by the divalent Ca resulted in incorporation of HS into floc when neutralised by Ca(OH)2, resulting in low turbidity and SS. However, in NaOH neutralised conditions, the monovalent Na was unable to bridge HS molecules, resulting in HS remaining dissolved and contributing to elevated turbidity and SS of up to 24.4 NTU and 18.4, respectively.
The neutralisation efficiency of CaCO3 is relatively low, thus approximately 1000 mg/L CaCO3 remained unreacted in MSS scenarios, resulting in elevated turbidity and SS. When added after neutralisation, dissolved Solid Energy Humic Acid (SEHA) facilitated flocculation of residual CaCO3 SS, resulting in an up to 75% lower suspended solids than CaCO3 neutralisation alone conditions. Although the results are good, the efficiency of SEHA as a polymer compared unfavorably in a cost: benefit analysis to two commercially available polymers for the removal of residual CaCO3.
Neutralisation of AMD in control samples resulted in decreased concentrations of the target metal group (Ni, Zn, Cu, Cd, and Pb) by hydroxide precipitation, co-precipitation, and adsorption. Equilibrium speciation modeling showed that the HS-metal binding affinity controlled the effectiveness of HS addition for metal removal. The low HS complexation affinity of Ni and Zn resulted in no additional metal removal by HS dosing. The removal of Cu was enhanced by over 50% for SEHA 20 during-neutralisation conditions neutralised by both NaOH and Ca(OH)2. Up to 80% lower Cd concentrations were observed for all HS dose conditions when neutralised by Ca(OH)2. Data for CaCO3 HS dosed metal removal was statistically indeterminate. The high detection limit for Pb made any HS dosed removal enhancement difficult to identify, which was unfortunate as Pb has a high HS complexation affinity (Čežı́ková, Kozler et al. 2001; Milne, Kinniburgh et al. 2003). A simple cost: benefit analysis showed that the additional removal of metals by HS dosing was less efficient than conventional neutralisation alone, on a cost basis.
Overall, incorporation of HS into AMD treatment results in improved water quality for CaCO3 neutralisation and lower concentrations of metals with a high HS binding affinity, for some conditions. However, further investigation is required to improve the feasibility of HS incorporation into the AMD neutralisation process.
8
Taube, Fabian. "Characterization of Aqueous Peroxomolybdates with Catalytic Applicability". Doctoral thesis, Umeå universitet, Kemiska institutionen, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-45.
Abstract (sommario):
Abstract This thesis is a summary of five papers, containing equilibrium and structure studies of aqueous molybdate and peroxomolybdate species. Some of the peroxomolybdate species have also been studied in terms of their dynamic and catalytic properties. The primary objective was to characterize species with potential catalytic activity, with emphasis on thebleach process of kraft pulp. For this, potentiometry, EXAFS and 17O, 31P, 1H and 95 Mo NMR have been used. The molybdate speciation in 0.300 M Na2(SO4) medium was found to differ from that in 0.600 M Na(Cl) medium, in that the uncharged monomeric molybdate species H2MoO4 was stronger in the sulphate medium, while highly charged species, such as Mo7O24 6-, became somewhat less pronounced. Diperoxomolybdate species, (MoX2)n (X = peroxo ligand, n = 1-2), dominated the peroxomolybdate systems when sufficient peroxide was available. Both sulphate and chloride coordinated to molybdenum in the presence of hydrogen peroxide and these species were more inert than diperoxomolybdate species without coordinated medium anions. Chemical exchange rates increased upon protonation. A dimeric triperoxomolydate species was the only species found that contained more than two peroxo groups per molybdenum atom. At low concentrations of hydrogen peroxide, monoperoxoheptamolybdate species, Mo7X, were found. Phosphate was found to coordinate relatively weakly to molybdate in the presence of peroxide. Species with four different nuclearities, i.e. (MoX2)nP (n = 1-4), were found. At excess of peroxide, no molybdophosphates were present. Chemical exchange rates were found to be substantially lower than in the peroxomolybdate system. The aqueous monomeric diperoxomolybdate species retain the pentagonal bipyramidal seven-coordination found in the solid state, although with increased bond lengths. Sulphate seems to coordinate to molybdenum in a monodentate fashion by replacing an oxygen atom. Chloride probably coordinates by replacing an oxygen atom as well. For the dimeric diperoxomolybdate species, a single oxygen-bridge was proposed. Conjugated carbon double bonds in the side chains of lignin model compounds were found to be hydroxylated or epoxidised by peroxomolybdate species. The addition of phosphate did not affect the type or yield of oxidation products noticeably. It was also shown that hydrogen peroxide, in the absence of molybdate, did not react to any noticeable extent with the lignin model compounds under these conditions.
9
Pouget, Clémentine. "Modélisation et simulation des systèmes électrolytiques multiphasiques réactifs dans l’environnement ProSim : Application aux géo-ressources". Thesis, Pau, 2017. http://www.theses.fr/2017PAUU3005/document.
Abstract (sommario):
La simulation des procédés est un outil de développement, de dimensionnement et d’optimisation des procédés dans les industries chimiques, pétrochimiques, pharmaceutiques, alimentaires, de l’énergie ou du traitement de gaz. Elle fournit une représentation des opérations du procédé en utilisant des modèles mathématiques pour chaque opération unitaire, s’assurant du respect des bilans de matière et d’énergie. Cependant l’utilisation de la simulation des procédés dans l’industrie peut être limitée par un manque de connaissance en thermodynamique.L’étude réalisée dans le cadre de cette thèse a pour objectif d’enrichir les modèles thermodynamiques adaptés aux solutions électrolytiques des logiciels de ProSim® avec les compétences du LaTEP dans le cadre d’applications aux géo-ressources et en profitant de la modélisation des opérations unitaires déjà présentes dans les logiciels de ProSim®.Dans un premier temps, les concepts et les définitions de base de la thermodynamique des solutions, nécessaires au développement des modèles, et notamment du cas particulier des solutions électrolytiques seront présentés, aboutissant sur l’écriture des divers équilibres permettant de décrire les solutions électrolytiques.Puis les grands principes des différents modèles thermodynamiques nécessaires à l’écriture des équilibres des solutions électrolytiques seront présentés, en mettant l’accent sur les modèles de coefficient d’activité qui sont alors spécifiques aux modèles électrolytiques prenant en compte les interactions de longue portée engendrées par la présence d’ions.Enfin, trois cas d’études de systèmes électrolytiques multiphasiques réactifs appliqués aux géo-ressources sont examinés : la géothermie profonde ; le traitement de gaz acides, issus de fumées de l'oxy-combustion d’une centrale à charbon ; la récupération du lithiumChemical process simulation is a very useful tool to improve the development, design and optimization of processes. Then, it can help in the chemical, petrochemical, pharmaceutical, energy production, gas processing, environmental, and food industries. It provides a representation of the operations of the process using mathematical models for the different unit operations, ensuring that mass and energy balances are satisfied. However, the use of process simulation in industry is currently being limited by a lack of understanding of thermodynamics
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Damiani, Leonardo Hax. "SHPECK : um software de modelagem de especiação geoquímica". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/131869.
Abstract (sommario):
Um software de modelagem de especiação geoquímica é responsável pelo cálculo da distribuição das espécies dissolvidas entre solutos e complexos aquosos, e também computar os índices de saturação para diferentes minerais. Neste trabalho nós apresentamos SHPECK, um software desenvolvido para modelar sistemas de equilíbrio geoquímico usando condições de balanço de massa baseadas no conceito da lei de fases (GARRELS; CHRIST, 1965). SHPECK gera um sistema de equações de ação de massa acopladas com restrições de equilíbrio e resolve com a utilização do método se Newton-Raphson. Nosso software aceita qualquer combinação de elementos, espécies e reações, permitindo ao usuário criar diferentes ambientes de simulação e, portanto, controlar qualquet aspecto e configuração do modelo. SHPECK contém uma interface de interação com o usuário e também um banco de dados estruturado que controla todo o gerenciamento dos dados termodinâmicos utilizados para a modelagem geoquímica. Aliado a isso, apresentamos também os conceitos básicos necessários para compreenção da modelagem geoquímica seguida por uma revisão de opções de software disponíveis para modelagem geoquímica. Para finalizar, fizemos uma validação do SHPECK através da modelagem de um sistema de reações diagenéticas observadas em um reservatório asiliclástico e realizamos um estudo comparativo dos resultados do SHPECK com outros software disponíveis. Também para validação, realizamos uma avaliação de tempo de acesso ao banco de dados e pode-se notar um aumento de performance considerável através do uso de um banco de dados relacional comparando-se aos approaches existentes.A geochemical speciation modeling software is responsible for calculating the distribution of dissolved species between solutes and aqueous complexes, and also computes saturation indexes for different minerals. In this work we introduce SHPECK, a software program developed to model geochemical equilibrium systems using the mass-balance conditions based on the phase rule concept (GARRELS; CHRIST, 1965). SHPECK composes a system of mass-action equations coupled with equilibrium constraints and solve using Newton-Raphson method. Our software accepts any general combination of elements, species, and reactions, allowing the user to create different environments, simulations and, therefore, fully control any aspect and configuration of the model. It provides an interactive user interface as well as the support of a builtfrom- the-ground database structure that handles the management of the whole thermodynamic data used for the geochemical modeling. Also, we present the basic concepts for geochemical modeling followed by a computer science based review about the available geochemical modeling software. Finally, we validate SHPECK by modeling the diagenetic reactions observed in asiliciclastic reservoir and by performing a comparative study with other modelling software package. In addition to this, a database comparison was addressed and the results demonstrate a substantial improvement on the performance by the use of the SHPECK’s relational database comparing to the existent approaches.
Libri sul tema "Speciation at equilibrium":
1
Brown, David S. MINTEQA1, an equilibrium metal speciation model: User's manual. Athens, Ga: Environmental Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, 1987.
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Cattani, Gino, e Mariano Mastrogiorgio, a cura di. New Developments in Evolutionary Innovation. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198837091.001.0001.
Abstract (sommario):
Evolutionary thinking has grown significantly and has had a profound impact on various fields such as economics, strategy, and technological innovation. An important paradigm that underlies the evolutionary theory of innovation is neo-Darwinian evolution. According to this paradigm, evolution is gradualist and is based on the mechanisms of variation, selection, and retention. Starting from the 1970s, new theoretical advancements in evolutionary biology have recognized the central role of punctuated equilibrium, speciation, and exaptation. However, despite their significant influence in evolutionary biology, these advancements have been reflected only partially in evolutionary approaches to economics, strategy, and technological innovation. The aim of this book is to review these advancements and explore their implications, with a particular emphasis on the role of serendipity and unpre-stateability in innovation and novelty creation.
Capitoli di libri sul tema "Speciation at equilibrium":
1
Arp, Paul A., e Rock Ouimet. "Aluminum Speciation in Soil Solutions: Equilibrium Calculations". In Acidic Precipitation, 1413–20. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-3385-9_144.
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Kester, D. R. "Equilibrium Models in Seawater: Applications and Limitations". In The Importance of Chemical “Speciation” in Environmental Processes, 337–63. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-70441-3_18.
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Du, Miting, e Gregory R. Choppin. "Correlation of Equilibrium Constants with Ionic Strength by Sit, Pitzer and Parabolic Models". In Actinide Speciation in High Ionic Strength Media, 125–39. Boston, MA: Springer US, 1999. http://dx.doi.org/10.1007/978-1-4419-8690-0_7.
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Piro, M. H., B. J. Lewis e W. T. Thompson. "A Procedure to Compute Equilibrium Gas-Phase Speciation for Use with Predominance Diagrams". In Uhlig's Corrosion Handbook, 287–97. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9780470872864.ch22.
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Schecher, William D., e Charles T. Driscoll. "ALCHEMI: A Chemical Equilibrium Model to Assess the Acid-Base Chemistry and Speciation of Aluminum in Dilute Solutions". In SSSA Special Publications, 325–56. Madison, WI, USA: Soil Science Society of America and American Society of Agronomy, 2015. http://dx.doi.org/10.2136/sssaspecpub42.c16.
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Gamble, D. S. "Interactions Between Natural Organic Polymers and Metals in Soil and Freshwater Systems: Equilibria". In The Importance of Chemical “Speciation” in Environmental Processes, 217–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-70441-3_13.
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Wang, C. Y., S. P. Bi, W. Tang, N. Gan, R. Xu e L. X. Wen. "Modeling the Distribution of Aluminum Speciation in Soil Water Equilibria with the Mineral Phase Jurbanite". In ACS Symposium Series, 100–111. Washington, DC: American Chemical Society, 2003. http://dx.doi.org/10.1021/bk-2004-0872.ch008.
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Anderson, Greg M., e David A. Crerar. "Speciation Calculations". In Thermodynamics in Geochemistry. Oxford University Press, 1993. http://dx.doi.org/10.1093/oso/9780195064643.003.0023.
Abstract (sommario):
This chapter focuses on one of the most common questions asked about natural chemical systems: what are the concentrations or activities of the different species present in a system at complete chemical equilibrium? We might be concerned, for example, with oxygen or sulfur fugacities, with the activities of complex ions, or activity ratios of reduced and oxidized species of the same component. In practice, these calculations range from trivially simple to enormously complex, depending on the number of species (and components) in the system. We will follow roughly this order—from trivial to complex—and outline some of the most common approaches used in performing speciation calculations. This simplest procedure is probably used most often, and works best with systems containing relatively few chemical species. As a general rule of thumb, you might try this if there are fewer than 10 species, but move on to another more sophisticated method for more complicated systems. As an example, we will solve for the equilibrium concentrations of all species in an acetic acid + water solution of a given concentration, m. Specifically, we might be interested in the pH of a 0.1 m HAc solution, but in calculating this we will also get the activities of all other species, whether we need them or not. This is one of the simplest examples imaginable, but the method works exactly the same way with more complicated systems. An excellent reference on this general approach is Butler (1964, Chap. 3). There are six steps to follow:… 1. Write all species of relevance or interest. Count the number of unknown species. You will need this many equations. 2. Write all known equilibrium constant equations. 3. If there are charged species, write a charge balance equation. 4. Write all known mass balance equations. 5. You should now have the same number of equations as unknown species. Reduce these by algebraic substitution to one (or two) equations that can be solved for the unknown concentrations. At first, assume all activity coefficients are 1.0.
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Brezonik, Patrick L., e William A. Arnold. "Complexation Reactions and Metal Ion Speciation". In Water Chemistry, 333–88. 2a ed. Oxford University PressNew York, 2022. http://dx.doi.org/10.1093/oso/9780197604700.003.0009.
Abstract (sommario):
Abstract This chapter deals with the second associative reaction type in ionic equilibria: complexation. After presenting definitions, the chapter describes ways to express equilibria of complexes and their components: metal ions and ligands. The chemical and ecological significance of complexes is summarized, along with the two types of complexes—inner and outer sphere. Factors affecting binding strengths of complexes are described, with attention to predictive relationships. Methods to solve and display complexation equilibria are explained, including simple examples solvable manually and computer methods for complicated situations in many natural waters. The roles of inorganic and organic ligands in metal ion speciation are described using examples ranging from soft to hard waters and high-ionic-strength seawater. The kinetics of complex formation and dissociation is treated. Although most formation reactions are fast, dissociation can be slow for strong complexes. Some metal-ligand exchange processes are slow enough to maintain non-equilibrium conditions for extended periods.
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Lieberman, Bruce S. "Stephen Jay Gould’S Evolving, Hierarchical Thoughts On Stasis". In Stephen Jay Gould, 227–41. Oxford University PressNew York, NY, 2008. http://dx.doi.org/10.1093/oso/9780195373202.003.0009.
Abstract (sommario):
Abstract Steve Gould made so many lasting contributions to paleontology and evolutionary biology that it is hard to identify any one as most significant. It is clear, however, that his work developing punctuated equilibrium with Niles Eldredge (e.g., Eldredge, 1971; 1972e; 1977c) will rank as one of the most important. Punctuated equilibrium posits that speciation takes place relatively rapidly compared to the total duration of the species and occurs in small, isolated populations usually along the margin of the species range. Because of the relatively sudden nature of speciation and because it happens in small, isolated populations, its occurrence in the fossil record will be difficult to observe. Punctuated equilibrium also posits that throughout most of their evolutionary history species are stable, displaying what was termed morphological stasis; stasis may be punctuated equilibrium’s “most important contribution to evolutionary science” (2002c, 874). The development of punctuated equilibrium represented an important theoretical breakthrough by Eldredge and Gould made possible because each author had collected abundant data from the fossil record, and also each author had a thorough understanding of evolutionary theory. The latter was particularly important.
Atti di convegni sul tema "Speciation at equilibrium":
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Kallner, Per, Anders Nordin e Rainer Backman. "Fate of Ash Forming Elements in Gas Turbine Combustion of Pulverized Wood: Chemical Equilibrium Model Calculations". In ASME 1996 Turbo Asia Conference. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-ta-025.
Abstract (sommario):
A new concept for direct combustion of wood in a gas turbine is presently developed and tested in Sweden. The process is based on a fuel rich cyclone gasifier/separator and a direct coupled modified standard gas turbine combustor. A main concern is the behaviour of ash forming elements in the turbine. A picture of this can be obtained with chemical equilibrium calculations. The objective of the present work was to determine the equilibrium speciation of the ash forming elements from wood passing through the turbine of a gas turbine engine for varying feed characteristics and operating conditions. In addition, the differences between using only stoichiometric and using non-ideal solution models as thermodynamic input data were illustrated. The equilibrium relationships at the turbine stage were evaluated in a parametric study, utilizing statistical experimental designs to systematically perform the model calculations. A wide range of operating conditions, wood compositions and cyclone elemental retention efficiencies were thereby covered. The results show considerable variation in the alkali speciation as well as in devolitalization and condensation temperatures, depending on the elemental composition. Plots of the effects of the most influential variables are presented and results not directly displayed in this work are illustrated with model equations provided.
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Duan, Haochen, e Fang Huang. "Indium (In) speciation and equilibrium In isotope fractionation between chloride-rich aqueous solution and minerals". In Goldschmidt2023. France: European Association of Geochemistry, 2023. http://dx.doi.org/10.7185/gold2023.17377.
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Sonwane, Pavankumar, Heng Ban e Thomas K. Gale. "Speciation of Chlorine and Alkali Metals in Biomass Combustion and Gasification". In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15032.
Abstract (sommario):
Alkali metals, mainly sodium and potassium, together with other ash forming inorganic components in biomass increases fouling, slagging, and high temperature corrosion during biomass combustion or gasification. To reduce the amount of alkali vapor to an acceptable level, which may be affected by Si, Al, Ca, S, Mg, and P, the information on the speciation of alkali metals is essential. In this study, thermodynamic equilibrium calculations were performed to determine the distribution and mode of occurrence of gaseous chlorine and alkali metals of three types of biomass (corn stover, switch grass, and wheat straw) in combustion and gasification processes. The influence of temperature, pressure, and air-fuel ratio was also evaluated. Results show that the excess air has limited influence on the speciation of chlorine and potassium during combustion. However, the influence of the excess air is significant during gasification. Increasing excess air enhances the formation of vapor HCl and KOH as well as reduction in vapor KCl and K2Cl2. In biomass combustion and gasification, increasing pressure increases vapor HCl and K2Cl2 and reduces the amount of vapor KCl and KOH. At higher temperatures (>1100K), the gaseous alkali species increased greatly. The results will be useful in the better development of hot gas clean-up technologies.
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Kalantari Meybodi, Mahdi, Ken S. Sorbie, Oscar Vazquez, Khosro Jarrahian e Eric J. Mackay. "A Coupled Model of Phosphonate Scale Inhibitor Interactions with Carbonate Formations". In SPE International Conference on Oilfield Chemistry. SPE, 2023. http://dx.doi.org/10.2118/213819-ms.
Abstract (sommario):
Abstract In this study, a chemical model has been developed for the simulation of the scale inhibitor (SI) interactions with carbonate systems (calcite), where the aqueous phase may contain free calcium and magnesium ions. The resulting model couples together the equations of (i) the carbonate system, (ii) the speciation of the SI, modelled as a weak polyacid, HnA, (iii) the metal (Ca2+, Mg2+) binding – SI chelant interactions and (iv) the subsequent precipitation of SI-Ca-Mg complex. These reactions are considered in conjunction with the charge balance and mass balances for calcium, magnesium, scale inhibitor and "carbon" (i.e. the carbonate system aqeous components HCO3-, CO32- and CO2 and solid CaCO3). This full equation set, with suitable reduction, results in a system of 3 non-linear equations which can be solved by the Newton-Raphson method to find the final equilibrium state of the system. The experimental results for the DETPMP/Calcite/Ca-Mg brine system from a previous study were used to check the reliability of the proposed model. The model calculates the equilibrium concentrations of all species (SI, Ca2+, Mg2+, HCO3-, CO32-, CO2, H+, and the components of the SI-Ca-Mg complexes etc.) based on their initial values and reaction constants, i.e. equilibrium constants, stability constants and solubility constants. The model can be applied either assuming a closed chemical system, or an open system and simuilation conditions were chosen in order to match the actual experiments which were matched. The model results show good quantitative agreement with the experimental results, although some assumptions must be made on the system input constants. To elucidate the precise effects that these various parameters are having in this very complex coupled system, an extensive sensitivity analysis was performed. This is especially important for uncertain parameters like stability constants of the complexes of scale inhibitor with calcium and magnesium, which are not reported in the literature. In future, this model be coupled with the adsorption model (based on the isothermal adsorption curve) and the coupled model will be incorporated into a transport model to develop a complete coupled adsorption/precipitation squeeze treatments simulation model. To our knowledge, no such model currently exists.
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Shaw, S. S. S., e K. S. S. Sorbie. "Structure, Stoichiometry, and Modelling of Mixed Calcium Magnesium Phosphonate Scale Inhibitor Complexes for Application in Precipitation Squeeze Processes". In SPE International Oilfield Scale Conference and Exhibition. SPE, 2014. http://dx.doi.org/10.2118/spe-169751-ms.
Abstract (sommario):
Abstract In this paper, the properties of precipitated “mixed” calcium and magnesium phosphonate scale inhibitor (SI) complexes formed by 9 common phosphonate species are investigated. These complexes are of the form SI_ CaNl _MgN2 where the stoichiometry (Ca2+/SI and Mg2+/SI molar ratios, i.e. N1 and N2) in various precipitates are established experimentally, and the effect of solution pH on the stoichiometry is determined. Static precipitation tests were performed varying the amounts of Ca2+ and Mg2+ present in the system (at a constant ionic strength), at test temperatures ranging from 20°C to 95°C, at a fixed [SI] = 2, 000ppm. The stoichiometries of the solid precipitates were determined by assaying for Ca2+, Mg2+, and P in the supernatant liquid, under each test condition, by ICP spectroscopy. It is shown experimentally that, for all 9 phosphonates tested, these stoichiometries (i.e. N1 and N2 in SI_ CaN1 _MgN2) depend on (i) the nature of the SI (i.e. M2+ binding sites per molecule); (ii) solution pH, which affects the speciation of the SI; (iii) the relative magnitude of the SI binding constants to Ca2+ and Mg2+ at the test pH (Kb1 and Kb2, respectively); and (iv) the solution molar ratio of Mg2+/Ca2+. It is found that, as pH increases, the combined molar ratio of Ca2+ and Mg2+ to SI, i.e. Nt = N1 + N2 in the complex, increases up to a theoretical maximum, Nt,max, depending on the chemical structure of the phosphonate (corroborating earlier work, SPE 155114, SPE 164051). In addition, the precipitation behaviour of the various compounds is modelled theoretically by developing and solving a set of simplified equilibrium equations. Very good agreement is seen between the modelling and experimental results. Such models can be used directly in the simulation of field phosphonate precipitation squeeze treatments in order to design and optimize squeeze lifetimes.
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Meybodi, M. Kalantari, K. S. Sorbie, O. Vazquez, K. Jarrahian e E. J. Mackay. "Coupled Adsorption/Precipitation Modelling of Phosphonate Scale Inhibitors in a Batch Reactive System". In SPE International Conference and Exhibition on Formation Damage Control. SPE, 2024. http://dx.doi.org/10.2118/217904-ms.
Abstract (sommario):
Abstract Scale inhibitor squeeze treatments are one of the most common ways to prevent scale deposition. The mineral scale will be inhibited if the concentration of the scale inhibitor (SI) in the produced water is above a certain threshold, known as the Minimum Inhibitor Concentration (MIC), which is controlled by scale inhibitor retention. Therefore, accurate modelling of the SI retention through adsorption (Γ) and precipitation (А) is critical to the successful design and implementation of squeeze treatments. In this study, an equilibrium model has been developed to simulate the coupled adsorption-precipitation (Ð/А) of phosphonate scale inhibitors in reactive formations, such as carbonates, in the presence of calcium and magnesium cations. In this approach, the scale inhibitor (SI) was considered as a poly weak acid that may be protonated (HnA), resulting in the complexation with Ca/Mg ions, leading to the precipitation of SI_Ca/Mg complexes. All these reactions occur in an integrated system where carbonate system reactions and adsorption of the soluble species are occurring in parallel. In the adsorption process, all the SI derivatives remaining in the solution, including free and complex species, are considered to participate in the adsorption process, described by an an adsorption isotherm model (e.g., Freundlich). For the precipitation part, the model considers the following reactions: (i) the carbonate system, (ii) SI speciation, considered as weak polyacid, HnA, (iii) the SI-metal (Ca and Mg) binding complexes, and (iv) subsequent precipitation of the SI-Ca/Mg complex. The system charge balance and the mass balances for calcium, magnesium, carbon, and SI are considered, to numerically equilibrate the system (excluding the adsorbed species), by solving a determined set of non-linear equations numerically. Following the algebraic reduction of the equations, the system is reduced to three non-linear equations that may be solved by the Newton-Raphson method. The precipitation of the SI-Ca/Mg is modelled in the equilibrium model based on the solubility of SI in the solution, determined from the lab experiments. The reliability of the proposed model was established by comparison with experimental results from a previous study (Kalantari Meybodi et al., 2023) on the interactions of DETPMP in a Calcite/brine (containing free Ca/Mg) system, where the final concentration of SI, Ca2+, Mg2+, CO2 and pH were compared. The modelling showed good general agreement with the experimental results, and a further sensitivity analysis was performed to examine the behaviour of some uncertain parameters, such as the stability constant of complexes.
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Reed, G. P., D. R. Dugwell e R. Kandiyoti. "Modelling Trace Element Emissions in Co-Gasification of Sewage Sludge With Coal". In ASME Turbo Expo 2002: Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30672.
Abstract (sommario):
Gasification has attracted considerable interest from water utilities as a sewage sludge disposal option, with the advantages of waste volume reduction, pathogen destruction and energy recovery. Co-gasification with coal in a larger plant (>10 MWt) employing a gas turbine for energy recovery may reduce the risk and cost of this option. However, controlling the release of trace elements such as Pb and Zn in the gas produced may be necessary to avoid corrosion, and to meet environmental requirements. A thermodynamic equilibrium model has been used to make predictions of the speciation of trace elements in the fuel gas from co-gasification of sewage sludge with coal. Experimental data from a pilot scale 2 MWt sewage sludge/coal co-gasification plant with a hot gas filter was used to test the validity of these predictions. No significant amount of Be, Co, Cu, V and Zn was predicted to be in the form of gaseous phase species, and this was confirmed by the experimental data. On the other hand, Hg and Se were predicted to be only present in gas phase species, and this was also confirmed experimentally. The elements As, B, Cd, Pb, Sb and Sn were all predicted to form a larger amount of gaseous species than was observed in the experimental measurements. Refinement of the predictions for As and B by inclusion of specific minor/trace element interactions with Ni and Ca respectively gave a better agreement with the experimental data. Whilst the experimentally-observed lowering of Pb emissions by reduction of the gas cleaning temperature from 580 °C to 450 °C was qualitatively predicted, the concentration of Pb in the fine dust removed by the hot gas filter indicates condensation at higher temperatures than predicted. The absence of thermodynamic data for the more complex minerals and adsorbed species that may be formed is thought to account for some of these differences.
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Zeynalli, Mursal, Anas M. Hassan, Ahmed Fathy, Emad W. Al-Shalabi, Javad Iskandarov, Aaron G. Tellez Arellano, Muhammad S. Kamal e Shirish Patil. "Advancements in Surfactant-Polymer Flooding Modeling: An Extensive Review of Reservoir Simulation Tools". In SPE Conference at Oman Petroleum & Energy Show. SPE, 2024. http://dx.doi.org/10.2118/218575-ms.
Abstract (sommario):
Abstract Despite advances in renewable energy, fossil fuels remain the primary energy source, necessitating the enhancement of oil recovery techniques for both existing and new oil fields. Surfactant-polymer flooding stands out as a promising method for improving oil recovery, with its potential to alter the intricate dynamics of fluid-rock interactions in porous media. It offers distinct advantages, as polymers enhance the mobility and conformance of the injectant, mitigating issues such as viscous fingering and channeling, whereas surfactants mobilize residual oil by reducing interfacial tension and creating favorable wettability conditions. However, accurate modeling of surfactant-polymer flooding is paramount for optimizing this enhanced oil recovery (EOR) technique by understanding complex interactions, addressing inherent limitations, and facilitating informed decision-making in reservoir engineering. This paper provides a comprehensive investigation of recent advancements in surfactant-polymer modeling within prominent reservoir simulation tools, including UTCHEM, CMG-STARS, ECLIPSE, and MRST simulators. The polymer models implemented in various simulators demonstrate a wide range of functionalities, accurately portraying polymer viscosities under varying salinities and polymer concentrations, capturing non-Newtonian behavior, and accounting for phenomena such as adsorption and permeability reduction. Particularly, both UTCHEM and MRST simulators exhibit remarkable capabilities in handling polymer viscoelasticity and its impact on oil recovery. Moreover, the manually embedded correlations in MRST appear to be well-suited and effective for representing polymer mechanical degradation. On the other hand, an examination of surfactant modules in the studied simulators demonstrated the exceptional capabilities of UTCHEM, especially in the characterization of microemulsion viscosity and proper analysis of surfactant phase behavior. Unlike other simulators, UTCHEM adeptly identifies all three microemulsion types, encompassing Winsor Type I, II, and Type III. Additionally, for interfacial tension reduction, UTCHEM employs a variety of correlations, setting it apart from other simulators that primarily rely on tabular input for defined interfacial tension values, thereby underscoring another advantage of UTCHEM in modeling surfactant flooding. Finally, the incorporation of geochemical reactions significantly improves the modeling of interactions between the injected materials and the reservoir’s rock and fluids. UTCHEM encompasses extensive geochemical reaction models, covering reactions involving aqueous species, dissolution/precipitation of solid species, exchange species reactions, and surfactant-related exchange species reactions. However, CMG-STARS provides the option to either import geochemical reactions from the CMG library or allow users to insert them, ensuring minimal mass balance errors and using experimentally determined equilibrium constant values. Meanwhile, ECLIPSE triggers geochemical reactions using a specific set of keywords, while the integration of MRST with the PHREEQC system enables the utilization of geochemical reactions to assess the concentration of individual chemical species and mineral properties. The latter involves considerations such as aqueous speciation, mineral dissolution/precipitation, ion-exchange activities, and surface complexation reactions. This research serves as a benchmark for the industry, providing insights into the strengths and limitations of different simulation tools. The findings offer a detailed perspective on the dynamic developments in surfactant-polymer modeling, paving the way for enhanced decision-making in reservoir engineering and contributing to the advancement of enhanced oil recovery practices.
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Stewart, Diane L., Anthony J. Gerbino e Tony Scribner. "Application of OLI Electrolyte Simulation to the Resolution of Corrosion Concerns Within a Reciprocating Compressor". In ASME 2012 International Manufacturing Science and Engineering Conference collocated with the 40th North American Manufacturing Research Conference and in participation with the International Conference on Tribology Materials and Processing. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/msec2012-7224.
Abstract (sommario):
A 38 MMSCF/D Cooper Bessemer Model LM-9 reciprocating compressor in hydrogen service at the Praxair Westlake LA facility has experienced notable particulate contamination within the feed gas. The particulates were believed to be caused by upstream piping corrosion; however, to definitely state the cause, the properties of the fluid existing in the five-stage compressor needed to be more fully understood. An OLI electrochemical simulation software was used for dew point prediction, determination of the condensed phase ionic equilibria, and corrosion rate prediction. These tasks were beyond capabilities of the site-licensed UniSim software, as presently configured. Specifically, the model was used to identify the dew point conditions (temperature, pressure) and properties of the condensed water (pH, corrosivity, dissolved O2, and chlorine speciation). Model results were compared with site inspection findings. Subsequently, recommended limits for chlorine and oxygen in the feed gas were established to improve long term compressor reliability.
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Wright, David. "INTEGRATING PROBABILISTIC PHYLOGENETICS WITH THE THEORY OF PUNCTUATED EQUILIBRIA TO TEST THE TEMPO AND MODE OF SPECIATION IN THE FOSSIL RECORD". In GSA Connects 2022 meeting in Denver, Colorado. Geological Society of America, 2022. http://dx.doi.org/10.1130/abs/2022am-380438.
Rapporti di organizzazioni sul tema "Speciation at equilibrium":
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Moffat, Harry K., e Carlos F. Jove-Colon. Implementation of equilibrium aqueous speciation and solubility (EQ3 type) calculations into Cantera for electrolyte solutions. Office of Scientific and Technical Information (OSTI), giugno 2009. http://dx.doi.org/10.2172/970260.
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Robinson, Troy A. Equilibrium Speciation of Select Lanthanides in the Presence of Acidic Ligands in Homo- and Heterogeneous Solutions. Office of Scientific and Technical Information (OSTI), agosto 2011. http://dx.doi.org/10.2172/1024547.
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Bruland, Kenneth W. Trace Metal Speciation: Equilibrium and Kinetic Considerations on Biological Effects, Phytoplankton Uptake and Sorption Processes in Coastal Waters (Field and Laboratory Studies). Fort Belvoir, VA: Defense Technical Information Center, agosto 2001. http://dx.doi.org/10.21236/ada627883.
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Bruland, Kenneth W. Trace Metal Speciation: Equilibrium and Kinetic Considerations on Biological Effects, Phytoplankton Uptake and Sorption Processes in Coastal Waters (Field and Laboratory Studies). Fort Belvoir, VA: Defense Technical Information Center, settembre 1999. http://dx.doi.org/10.21236/ada630785.
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Shenker, Moshe, Paul R. Bloom, Abraham Shaviv, Adina Paytan, Barbara J. Cade-Menun, Yona Chen e Jorge Tarchitzky. Fate of Phosphorus Originated from Treated Wastewater and Biosolids in Soils: Speciation, Transport, and Accumulation. United States Department of Agriculture, giugno 2011. http://dx.doi.org/10.32747/2011.7697103.bard.
Abstract (sommario):
Beneficial use of reclaimed wastewater (RW) and biosolids (BS) in soils is accompanied by large input of sewage-originated P. Prolonged application may result in P accumulation up to levelsBeneficial use of reclaimed wastewater (RW) and biosolids (BS) in soils is accompanied by large input of sewage-originated P. Prolonged application may result in P accumulation up to levels that impair plant nutrition, increase P loss, and promote eutrophication in downstream waters. This study aims to shed light on the RW- and BS-P forms in soils and to follow the processes that determine P reactivity, solubility, availability, and loss in RW and BS treated soils. The Technion group used sequential P extraction combined with measuring stable oxygen isotopic composition in phosphate (δ18OP) and with 31P-NMR studies to probe P speciation and transformations in soils irrigated with RW or fresh water (FW). The application of the δ18OP method to probe inorganic P (Pi) speciation and transformations in soils was developed through collaboration between the Technion and the UCSC groups. The method was used to trace Pi in water-, NaHCO3-, NaOH-, and HCl- P fractions in a calcareous clay soil (Acre, Israel) irrigated with RW or FW. The δ18OP signature changes during a month of incubation indicated biogeochemical processes. The water soluble Pi (WSPi) was affected by enzymatic activity yielding isotopic equilibrium with the water molecules in the soil solution. Further it interacted rapidly with the NaHCO3-Pi. The more stable Pi pools also exhibited isotopic alterations in the first two weeks after P application, likely related to microbial activity. Isotopic depletion which could result from organic P (PO) mineralization was followed by enrichment which may result from biologic discrimination in the uptake. Similar transformations were observed in both soils although transformations related to biological activity were more pronounced in the soil treated with RW. Specific P compounds were identified by the Technion group, using solution-state 31P-NMR in wastewater and in soil P extracts from Acre soils irrigated by RW and FW. Few identified PO compounds (e.g., D-glucose-6-phosphate) indicated coupled transformations of P and C in the wastewater. The RW soil retained higher P content, mainly in the labile fractions, but lower labile PO, than the FW soil; this and the fact that P species in the various soil extracts of the RW soil appear independent of P species in the RW are attributed to enhanced biological activity and P recycling in the RW soil. Consistent with that, both soils retained very similar P species in the soil pools. The HUJ group tested P stabilization to maximize the environmental safe application rates and the agronomic beneficial use of BS. Sequential P extraction indicated that the most reactive BS-P forms: WSP, membrane-P, and NaHCO3-P, were effectively stabilized by ferrous sulfate (FeSul), calcium oxide (CaO), or aluminum sulfate (alum). After applying the stabilized BS, or fresh BS (FBS), FBS compost (BSC), or P fertilizer (KH2PO4) to an alluvial soil, P availability was probed during 100 days of incubation. A plant-based bioassay indicated that P availability followed the order KH2PO4 >> alum-BS > BSC ≥ FBS > CaO-BS >> FeSul-BS. The WSPi concentration in soil increased following FBS or BSC application, and P mineralization further increased it during incubation. In contrast, the chemically stabilized BS reduced WSPi concentrations relative to the untreated soil. It was concluded that the chemically stabilized BS effectively controlled WSPi in the soil while still supplying P to support plant growth. Using the sequential extraction procedure the persistence of P availability in BS treated soils was shown to be of a long-term nature. 15 years after the last BS application to MN soils that were annually amended for 20 years by heavy rates of BS, about 25% of the added BS-P was found in the labile fractions. The UMN group further probed soil-P speciation in these soils by bulk and micro X-ray absorption near edge structure (XANES). This newly developed method was shown to be a powerful tool for P speciation in soils. In a control soil (no BS added), 54% of the total P was PO and it was mostly identified as phytic acid; 15% was identified as brushite and 26% as strengite. A corn crop BS amended soil included mostly P-Fe-peat complex, variscite and Al-P-peat complex but no Ca-P while in a BS-grass soil octacalcium phosphate was identified and o-phosphorylethanolamine or phytic acid was shown to dominate the PO fraction that impair plant nutrition, increase P loss, and promote eutrophication in downstream waters. This study aims to shed light on the RW- and BS-P forms in soils and to follow the processes that determine P reactivity, solubility, availability, and loss in RW and BS treated soils. The Technion group used sequential P extraction combined with measuring stable oxygen isotopic composition in phosphate (δ18OP) and with 31P-NMR studies to probe P speciation and transformations in soils irrigated with RW or fresh water (FW). The application of the δ18OP method to probe inorganic P (Pi) speciation and transformations in soils was developed through collaboration between the Technion and the UCSC groups. The method was used to trace Pi in water-, NaHCO3-, NaOH-, and HCl- P fractions in a calcareous clay soil (Acre, Israel) irrigated with RW or FW. The δ18OP signature changes during a month of incubation indicated biogeochemical processes. The water soluble Pi (WSPi) was affected by enzymatic activity yielding isotopic equilibrium with the water molecules in the soil solution. Further it interacted rapidly with the NaHCO3-Pi. The more stable Pi pools also exhibited isotopic alterations in the first two weeks after P application, likely related to microbial activity. Isotopic depletion which could result from organic P (PO) mineralization was followed by enrichment which may result from biologic discrimination in the uptake. Similar transformations were observed in both soils although transformations related to biological activity were more pronounced in the soil treated with RW. Specific P compounds were identified by the Technion group, using solution-state 31P-NMR in wastewater and in soil P extracts from Acre soils irrigated by RW and FW. Few identified PO compounds (e.g., D-glucose-6-phosphate) indicated coupled transformations of P and C in the wastewater. The RW soil retained higher P content, mainly in the labile fractions, but lower labile PO, than the FW soil; this and the fact that P species in the various soil extracts of the RW soil appear independent of P species in the RW are attributed to enhanced biological activity and P recycling in the RW soil. Consistent with that, both soils retained very similar P species in the soil pools. The HUJ group tested P stabilization to maximize the environmental safe application rates and the agronomic beneficial use of BS. Sequential P extraction indicated that the most reactive BS-P forms: WSP, membrane-P, and NaHCO3-P, were effectively stabilized by ferrous sulfate (FeSul), calcium oxide (CaO), or aluminum sulfate (alum). After applying the stabilized BS, or fresh BS (FBS), FBS compost (BSC), or P fertilizer (KH2PO4) to an alluvial soil, P availability was probed during 100 days of incubation. A plant-based bioassay indicated that P availability followed the order KH2PO4 >> alum-BS > BSC ≥ FBS > CaO-BS >> FeSul-BS. The WSPi concentration in soil increased following FBS or BSC application, and P mineralization further increased it during incubation. In contrast, the chemically stabilized BS reduced WSPi concentrations relative to the untreated soil. It was concluded that the chemically stabilized BS effectively controlled WSPi in the soil while still supplying P to support plant growth. Using the sequential extraction procedure the persistence of P availability in BS treated soils was shown to be of a long-term nature. 15 years after the last BS application to MN soils that were annually amended for 20 years by heavy rates of BS, about 25% of the added BS-P was found in the labile fractions. The UMN group further probed soil-P speciation in these soils by bulk and micro X-ray absorption near edge structure (XANES). This newly developed method was shown to be a powerful tool for P speciation in soils. In a control soil (no BS added), 54% of the total P was PO and it was mostly identified as phytic acid; 15% was identified as brushite and 26% as strengite. A corn crop BS amended soil included mostly P-Fe-peat complex, variscite and Al-P-peat complex but no Ca-P while in a BS-grass soil octacalcium phosphate was identified and o-phosphorylethanolamine or phytic acid was shown to dominate the PO fraction.