Precipitation of solids in plumbing systems (i.e., scaling) is a major problem in both traditional tank (electric and gas) and tank-less building hot water systems. Scaling can cause energy inefficiencies, flow reduction, pressure loss, and erosion corrosion damage. Consumers are also concerned with unsightly soap scum, cloudy water, discolored glassware, and failing infrastructure including appliances and fixtures. There are many treatments available that claim to ameliorate scaling problems, and several efforts have been made to develop standardized test protocols to verify and quantify their performance. This work critically evaluated previous testing efforts and revealed limitations in terms of reproducibility and a need to measure all key aspects of scale deposition including quantity, location, aesthetic and other issues. A Standardized Scaling Test Protocol (SSTP) was conceived and vetted to address these deficiencies and measure key parameters of calcium carbonate scaling throughout a model premise plumbing system, while using a synthesized test water that could provide reproducible results in any laboratory. This synthetic water and methodology was able to produce significant scaling in a model hot water system within the targeted 5-day experimental time frame. The average amount of scale recovered for the triplicate control tests (with no scale reduction device) was 25.1 grams of calcium carbonate with a 95% confidence interval of 20.3-29.8 grams of calcium carbonate. The approach also worked in recreating scaling in natural waters and was used to verify the performance of a wide array of scale reduction technologies including cation exchange softeners, electrochemical deionization, physical magnets or electric field generators, media induced precipitation, sacrificial media (phosphate), and sacrificial media (citric acid). While calcium carbonate precipitation within a water distribution system is generally undesirable; it was recently discovered that calcium carbonate particles are sometimes naturally clogging leaks in pipes and extending the lifetime of aging infrastructure. Corrosion inhibitors, mainly phosphates, have been increasingly dosed (up to 3.0 mg/L as PO4) into water to inhibit the corrosion of lead and copper pipelines in potable water systems since the advent of the Lead and Copper Rule (LCR) in 1991 by US Environmental Protection Agency (EPA). Phosphate corrosion inhibitors are now used at over 50% of water utilities in the United States and they can affect calcium carbonate scaling kinetics. In bench-scale experiments, the critical concentrations of phosphates that could inhibit leak repair over the short-term in one water tested were: tripolyphosphate (0.05 mg/L as P) < hexametaphosphate (0.1 mg/L) < orthophosphate (0.3 mg/L). The results prove that dosing of phosphates for corrosion control will also affect the kinetics and likelihood of calcium carbonate precipitation, with both beneficial and adverse consequences for pipes and consumers. Specifically, increased use of inhibitors for corrosion control is expected to reduce the likelihood of all calcium carbonate scaling problems while reducing the likelihood of autogenous pipe leak repair. In Providence, RI the dosing of orthophosphate at relatively high pH to control a lead corrosion problem, caused formation of a white precipitate, consumer reports of white water, clogging of aerators and loss of the added soluble phosphate corrosion control inhibitor due to precipitation. The precipitate was identified as a calcium phosphate solid. Field and lab scale tests suggest that at doses below 2 mg/L as PO4, precipitation did not occur in water at pH 10.4 even when the water was heated to 48°C. However, if the water was dosed above 2 mg/L as PO4 precipitation occurred within 5 minutes, and once pre-existing particles were formed precipitation tended to continue even at much lower phosphate doses. Virtually all of the phosphate precipitated within 4 hours at the upper range of 60°C that is commonly found in water heaters. Thus, dosing of phosphate can actually increase scaling problems in some circumstances. Prior work has highlighted a need for a simplified bench-scale test that can be used to rapidly screen for qualitative trends in scaling. The SSTP and practical experience showed that the vast majority of scaling occurred in the water heater. Therefore, a simplified bench-scale test consisting of a heating element in a small volume of water could be used to focus on the most sensitive aspect of scaling. A 3-hour bench-scale test was developed to quickly examine scaling with orders of magnitude less volume, time, labor, cost, and space requirements. This approach was used to evaluate aspects of scaling in water heaters for the following illustrative examples: (1) scale impacts of combined phosphate corrosion inhibitor addition and partial water softening at centralized treatment plants, (2) role of silica concentration in scaling propensity and deposit durability, (3) effects of phosphate addition on scaling in a water known to cause erosion corrosion pipe damage. This dissertation reveals the complexity of scaling for consumers and water utilities and provides tools to systematically study and resolve these practical problems. Dosing of phosphate corrosion control inhibitors can increase scaling from calcium phosphate, decrease scaling of calcium carbonate, and in other cases will have little or no effect on scaling. Both calcium carbonate and calcium phosphate can contribute to scaling as controlled by pH, temperature, hardness, phosphate dose, and other circumstances. The standardized bench and pilot scale approaches developed herein, can serve as a basis for building knowledge reproducibly in any modern laboratory. These methods can also be used to verify performance claims for a wide range of scale reduction technologies, test treatments that could be applied at centralized treatment plants, and optimize water heater design dependent on water chemistry. / Doctor of Philosophy / Precipitation of solids in plumbing systems (i.e., scaling) is a major problem in both traditional tank (electric and gas) and tank-less hot water systems. In addition to scale build up within the hot water system, consumers are also concerned with unsightly soap scum, cloudy water, discolored glassware, and failing infrastructure including appliances and fixtures. There are many treatments available that claim to mitigate scaling problems, and several efforts have been made to develop standardized test protocols to verify and quantify their performance. This work evaluated previous testing efforts to determine limitations in their methodology. A Standardized Scaling Test Protocol (SSTP) was developed to address these deficiencies and measure key parameters of calcium carbonate scaling throughout a model home plumbing system, while using a test water that could provide reproducible results in any laboratory. The test water was able to produce significant scaling within a 5-day test period with reproducible results. While calcium carbonate precipitation within a water distribution system is generally undesirable; it was recently discovered that calcium carbonate particles are sometimes naturally repairing leaks in pipes and extending the lifetime of aging plumbing systems. An increasing number of water treatment plants are adding corrosion inhibitors to water to prevent the corrosion of lead and copper pipelines. Small scale lab experiments were run to determine how effective this natural leak repair was when there were corrosion inhibitors in the water. The results showed that most corrosion inhibitors also prevented or delayed calcium carbonate precipitation which reduced the likelihood of pipe repair through clogging leaks. In Providence, RI the addition of a corrosion inhibitor caused a white precipitate to form in the water which led to consumer complaints of white water and clogging of aerators. This was due to the uniquely high pH of the water. The precipitate was identified as a calcium phosphate solid. Field and lab scale tests suggest that there is a critical inhibitor dose, below which no precipitation occurred in the high pH water. However, if the water was dosed above this critical limit, precipitation occurred immediately and continued as time went on. Prior work has highlighted a need for a simplified bench-scale test that can be used to rapidly screen for qualitative trends in scaling. A 3-hour bench-scale test was developed to quickly examine key aspects of scaling with orders of magnitude less volume, time, labor, cost, and space requirements. This dissertation reveals the complexity of scaling for consumers and water utilities and provides tools to systematically study and resolve these practical problems.

In this study, composite system was developed to enhance mechanical properties of plastic pallets. The potential of graphite nanoplatelets (GnP)/PP composites for the application in packaging was scrutinized by examining mechanical properties, thermal properties, flow properties, and morphology as a function of GnP loading and by comparison of two mixing methods: physical melt compounding (PMC) and chemical pretreatment compounding (CPC) processes. Incorporation of the GnP into PP resulted in a significant enhancement in the mechanical strength (tensile, impact, and flexural strength) and thermal decomposition temperature compared to the neat PP specimen. The CPC process clearly shows good exfoliation and better distribution on the PP matrix compared to the PMC method based on morphological evaluation measured by SEM. The impact test at low temperature revealed that the composites made by the CPC process showed 64% higher impact strength than neat PP due to higher even-distribution of GnP molecules into the PP matrix. We attempted to discover the degree of dispersion of natural fiber (kenaf) and graphite nanoplatelets (GnP) into the polypropylene (PP) polymer matrix and the effect of filler-adding sequence on physical and mechanical properties. Tensile strength of the composites was increased up to 25%. In the case of Young's modulus, composites showed a 56% enhancement compared to the control. However, the impact strength decreased as a result of the increased brittleness when kenaf fiber was added. Another study investigated the effects of hybrid filler systems (graphite nanoplatelets (GnP)/commercially available modified calcium carbonate (mCaCO3) nanoparticles) on mechanical and physical properties of polypropylene nanocomposites with three variables, filler loading amount, the number of compounding processes, and the compounding order of two different fillers. The impact strength of composite samples, containing 1wt% of GnP and mCaCO3 nanoparticles, increased up to 64% compared to neat PP. Among all tested samples, the highest tensile strength was found at 1wt% of mCaCO3 nanoparticles regardless of the presence or absence of GnP addition. There was no significant difference in flexural strength regardless of any nano-filler addition. However, both the flexural modulus and Young's modulus increased significantly when 10wt% of mCaCO3 nanoparticles were added. The number of compounding processes did not affect any strength, and the single compounding process was found to be more effective than the double compounding process. It may be contributed by thermal degradation of polymeric structure by double heat processing. This study can be able to provide a solution for value-added high-end products in various industries such as application in logistics, aerospace or electric automobile, where carbon-based nanomaterials are more affordable. / Doctor of Philosophy / Pallets are the basic structure of a unit load which allows handling and storage efficiency. The advantages of plastic pallets are durability, cleanliness, and performance reliability, However, those are expensive and have lower mechanical properties than that of wood, such as low strength, creeps and deformation. Therefore, hybrid composites were fabricated using various fillers, such as graphite nanoplatelets, kenaf fiber or calcium carbonate on polypropylene matrix to enhance mechanical properties for plastic pallets. In order to fabricate the composites, two methods were utilized and compared: physical melt compounding (PMC) and chemical pretreatment compounding (CPC) processes. Graphite nanoplatelets (GnP) reinforced polypropylene (PP) composites made by both PMC and CPC process showed significance in the mechanical process compared to the neat PP. Moreover, the CPC process showed better dispersion on the PP matrix resulting in higher impact strength in low temperature. Based on the first chapter, we attempted to focus on reducing weight and sustainability using natural fiber. At the same time, when two or more fillers are reinforced in a polymer matrix, I wondered if the order in which the fillers were added could affect properties. Kenaf fiber and GnP were reinforced in the PP matrix through the CPC process to discover the degree of dispersion of fillers and the effect of filler-adding sequence on physical and mechanical properties. Tensile strength of the composites was increased up to 25%. In the case of Young's modulus, composites showed a 56% enhancement compared to the control. However, the impact strength decreased as a result of the increased brittleness when kenaf fiber was added. Another study investigated the effects of hybrid filler systems (GnP/commercially available modified calcium carbonate (mCaCO3) nanoparticles) on mechanical and physical properties of polypropylene nanocomposites with three variables, filler loading amount, the number of compounding processes, and the compounding order of two different fillers. This study was concentrating on the impact strength based on the result that the material adding sequence affects the mechanical strength when manufacturing the hybrid composites. The hybrid composite system on GnP/mCaCO3/PP resulted in enhancement of impact strength, tensile strength, flexural modulus and Young's modulus. The number of compounding processes did not affect any strength, and the single compounding process was found to be more effective than the double compounding process. Enhancement of impact strength in low temperature, and effect of filler-adding sequence on mechanical properties in hybrid composite system can be able to provide a solution for value-added high-end products in various industries such as application in logistics, aerospace or electric automobiles, where carbon-based nanomaterials are more affordable.

An interbasinal study of Late Cambrian cyclic carbonate successions in the Appalachian and Cordilleran passive margins, the Texas cratonic embayment and the southern Oklahoma aulacogen has provided controls on the simultaneous development of peritidal to subtidal meter-scale cycles and the larger scale depositional sequences on which they are superimposed. Fining-upward peritidal cycles grade seaward into coarsening-upward, shallow to deep subtidal cycles that form a continuum across the carbonate platforms and are genetically linked to one another by shared lithofacies. Eustacy appears to exert the dominant control on the simultaneous development of peritidal and subtidal cycles on different carbonate platforms. Based on the recognition of dominant periodicities on power spectra derived from time series of subtidal cycles, high frequency eustatic oscillations may be controlled by Milankovitch astronomical rhythms. Interbasinal correlation of Late Cambrian depositional sequences was performed by graphic correlation and the time-equivalent intervals were correlated lithostratigraphically using isochronous biomere boundaries as time datums. Fischer plots of meter-scale cycles define changes in relative sea level based on the amount of extra accommodation space produced by eustacy beyond that provided by subsidence. Residual eustatic curves derived from subsidence analysis are useful for correlating the longer-term Late Cambrian sea level events and changes in the rate of sea level rise and fall can be used to define shorter-term events. Combining the sea level curves defined by Fischer plots and subsidence analysis with paleobathymetric curves of Late Cambrian cyclic strata suggests that the curves may approximate the form of the eustatic sea level curve. A composite "eustatic” sea level curve for the Late Cambrian was created by qualitatively combining the sea level curves defined by the different techniques for each of the four localities. “Eustatic" sea level curves defined by Fischer plots and subsidence analysis may be used to apply sequence stratigraphic concepts to onedimensional outcrop sections. Combined with systematic changes in the stacking patterns of meter-scale cycles, they can be used to define the internal composition of systems tracts, sequence boundaries, and flooding surfaces of third-order depositional sequences. One- and two-dimensional models of peritidal and subtidal cycle development indicate that peritidal cycle thickness is primarily controlled by accommodation space and deeper subtidal cycle thickness is primarily controlled by sedimentation rate. Whereas lithofacies within peritidal cycles alternate in response to fluctuations in sea level, subtidal cycle development may be related to fluctuations in fairweather and storm wave base that oscillate in harmony with sea level fluctuations. / Ph. D.

The Late Triassic platform carbonates of the Transdanubian Range, Hungary were part of a passive margin platform at the southwestern end of the Triassic Tethys now occurs in a single fault-bounded terrain. The Hungarian platform is made up of meter-scale, precessional (~20 k.y.) carbonate cycles. It contains a lower unit, the Main Dolomite Formation (600-1500m thick), which is totally dolomitized. It is overlain by the Transitional Unit (150-400m thick). The overlying Dachstein Limestone is up to 800m thick. The platform is a cyclic succession of subtidal carbonate, laminated tidal flat limestone or dolomitic caps, and reddish or greenish paleosols or reworked paleosols. The Triassic was a time of global greenhouse conditions and Milankovitch climate forcing has been well documented from lakes and off-shelf facies. The Triassic Hungarian carbonate platform records an imperfect Milankovitch eustatic signal. They lack the bundling of 5 precessional cycles into 100 k.y. eccentricity cycles or 20 cycles/400 k.y. bundle. This is interpreted to be due to many missed beats evidenced by caliches and paleosols, and thick amalgamated subtidal carbonates. These result from precessional sea-level fluctuations either not flooding the platform, or flooding it too deeply to allow shallowing up to sea-level in one precessional beat. Spectral analysis of the Hungarian carbonates was used to compare the amplitude spectra of different time series including lithology, gamma ray, self potential and neutron density. The spectra based on lithology were compared to synthetic spectra generated by computer from platforms subjected differing Milankovitch signals. Most dolomitization of the Hungarian carbonates occurred early in tidal flat settinfs during each high frequency cycle. Intertidal-supratidal dolomites are fine grained, Fe²⁺ and Mn²⁺ rich and slightly enriched in δ¹⁸O compared marine calcite cement, and formed from weakly to moderately reducing marine waters. Subtidal dolomites are slightly coarser grained, low in Fe²⁺ and Mn²⁺ and have heaviest d¹⁸O signatures, indicating more evaporative oxidizing brines beneath flats. Repeated emergence stabilized the dolomites to low Sr²⁺ and Na⁺ types similar to Cenozoic dolomites. Later, coarse-grained dolomites with very low Mn²⁺ Fe²⁺ and light δ¹⁸O signatures were formed along the platform margin by thermally driven, warm oxidizing marine water associated with Jurassic rifting of the Pennini Ocean (Neo-Tethys). The overall vertical distribution of early dolomite on the platform does not reflect long term ecstasy. Instead the regional stratigraphic trends in climatically sensitive sediments, as well as stable isotopes, suggest that intense dolomitization of the lower platform reflects a semi-arid, hot subtropical setting and megamonsoonal climate. Global cooling and increased humidity toward the latest Triassic and Early Jurassic, inhibited pervasive early dolomitization, leaving the upper platform little dolomitized. / Ph. D.

The formation of calcium carbonate (CaCO3) (i.e. scale) in potable water systems has long been a concern in water treatment and distribution. A literature review reveals that CaCO3 scaling issues are re-emerging due to climate change, temperature increases in hot water systems and lower use of scaling and corrosion inhibitors. Moreover, we have gathered insights that suggest CaCO3 coatings can be beneficial and stop pipeline leaks via self-repair or clogging. Ironically, the actions we are taking to increase the lifespan of distribution systems (i.e. adding corrosion inhibitors) might have worsened leaks and pipe lifespans due to interference with self-repair. The increasing occurrence of scaling coupled with gaps in knowledge over CaCO3 formation in water systems make revisiting this topic timely. The concept of autogenous repair by clogging with inert particles was examined using silica and alumina. Small 250 m diameter pinhole leaks were simulated in bench-scale water recirculation systems. Silica and alumina particles were added to solutions ranging from high to low ionic strength to determine the impact of water quality on leak repair. Size distribution and zeta potential of the particles were measured. Silica particles were practically unchanged by the different solution chemistries while the size and zeta potential of alumina particles varied. The rate of clogging with silica particles was not impacted by water chemistry. Alumina particles with a positive charge clogged 100% of the leaks while negatively charged alumina could not clog 100%. Very small alumina particles (4.1 m) stayed suspended but were unable to clog leaks. / Master of Science

The influence of calcium carbonate on the properties of four non-plastic lime-stabilized soils was studied. The four soils span a range in mica content and sand content. It was found that carbonate generally increased unconfined compressive strength and secant modulus of elasticity when included as part of the lime stabilizing agent. This effect was most pronounced with soils with a large sand content and low mioa content. A calcium hydroxide-calcium carbonate weight ratio of 3 to 1 was most effective for the case where six percent additive was used. It is hypothesized that the presence of carbonate enhances pozzolanic activity in lime-stabilized non-plastic soils by increasing the solubility of siliceous minerals at high pH levels. / Master of Science

L’augmentation constante du dioxyde de carbone dans l’atmosphère est considérée comme étant la cause principale du réchauffement climatique actuel. La séquestration géologique du CO2 semble être une des meilleures solutions envisageable pour réduire les rejets des gaz à effet de serre (dont le CO2) dans l’atmosphère, seulement si l’intégrité de la couverture du réservoir est préservée sur des centaines ou des milliers d’années. Des simulations expérimentales en batch ont été réalisées afin d’observer la réactivité d’une roche de couverture argileuse et d’une roche réservoir carbonatée en présence de CO2 à 80°C et 150°C pour une pression de 150 bar avec une eau équilibrée. Le protocole analytique mis en place a permis de comparer les roches avant et après expérimentation concluant à une réactivité très faible, centrée sur l’aluminium au niveau des phyllosilicates. Les analyses texturales montrent que le CO2 n’a pas d’incidence sur les propriétés d’adsorption et sur la surface spécifique. L’étude des carbonates du réservoir par la microscopie confocale a permis de mettre en évidence des phénomènes de dissolution-précipitation qui n’ont cependant pas d’impact important sur la chimie et la structure du réservoir. Les simulations numériques réalisées sur des minéraux de référence comme la montmorillonite calcique ou le clinochlore montrent une réactivité importante en présence de CO2 non atteinte expérimentalement, certainement due à des lacunes dans les bases de données thermodynamiques ou à la cinétique des réactions. Les simulations sur Bure ne montrent pas de réactivité sur les minéraux majeurs de la marne argileuse confirmant les résultats obtenus en expérimentation batch / The constant increase in the quantity of carbon dioxide in the atmosphere is regarded as being the principal cause of the current global warming. The geological sequestration of CO2 seems to be an ideal solution to reduce the increase of greenhouse gases (of which CO2) in the atmosphere but only if the reservoir’s caprock keep its integrity for several hundreds or thousands of years. Batch experimental simulations were conducted to observe the reactivity of a caprock made of clay and a carbonate reservoir with CO2 at 80°C and 150°C for a pressure of 150 bar with an equilibrated water. The analytical protocol established allowed to compare the rocks before and after experimentations finding a very low reactivity, focusing on aluminium in phyllosilicates. Textural analysis shows that CO2 does not affect the properties of adsorption and the specific surface. The study of carbonate reservoir by confocal microscopy has revealed phenomena of dissolution-precipitation which have no significant impact on chemistry and structure of the reservoir. The numerical simulations carried out on mineral reference as calcium montmorillonite or clinochlore show a significant reaction in the presence of CO2 not achieved experimentally, probably due to lacunas in the thermodynamic databases or the kinetics of reactions. The simulations on Bure show no reaction on the major minerals confirming the results with batch experiments

Le dioxyde de carbone occupe une place particulière dans l'amplification anthropogénique de l'effet de serre. En particulier, son utilisation dans la synthèse de carbonates organiques à partir d'alcools constituerait une alternative à l'emploi actuel du phosgène ou du monoxyde de carbone. L'insertion de CO2 dans Sn-OCH3 liaison de dialkyldimethoxystannanes est reconnue comme la première étape pour la formation du carbonate de diméthyle (DMC) à partir du méthanol et CO2. L'identification des étapes ultérieures est cruciale pour améliorer l'activité et est encore l’objet de débats car les espèces étain ont la propension à l’oligomérisation. Nous avons utilisé des calculs basés sur la Théorie de la Fonctionnelle de la Densité pour donner un aperçu sur le mécanisme de réaction. L'insertion de CO2 est promue par l’interaction acide-base concertée de Lewis de CO2 avec l'étain et l'atome d'oxygène du ligand méthoxy. Le chemin principal de la réaction pour la formation de DMC est proposé selon un réarrangement intramoléculaire des espèces monomériques, Me2Sn[OC(O)OCH3]2. Le processus conduit à un transfert d'un groupe méthyle d'un carbonate de méthyle à l'autre via un anneau de 4 atomes ou 6 atomes formant un fragment Sn-CO3. Dans une deuxième étape, le méthanol réagit avec un intermédiaire et conduit à la formation de DMC et un complexe de trimère qui peut permettre la régénération des réactifs. Mais un complexe décanucléaire d’étain peut être aussi produit par une réaction latérale. Enfin, un cycle catalytique pour produire le DMC a pu être élaboré. Les calculs DFT sont en accord avec les données expérimentales et permettent une analyse comparative des chemins de réaction / Carbon dioxide occupies a special place in the amplification of the anthropogenic greenhouse effect. In particular, its use in the synthesis of organic carbonates from alcohols, constitute an alternative to the current application of phosgene or carbon monoxide. The insertion of CO2 into the Sn-OCH3 bond of dialkyldimethoxystannanes is recognized as the first step to dimethyl carbonate (DMC) formation from methanol and carbon dioxide. The identification of the subsequent steps is crucial for activity improvements and is still under debate as the tin species have the propensity for oligomerization. We have used density functional theory calculations to provide insight into the reaction mechanism. The CO2 insertion into the Sn-OCH3 bond is promoted by the concerted Lewis acid-base interaction of CO2 with tin and the oxygen atom of the methoxy ligand. The major reaction pathway to DMC is proposed to occur via an intramolecular rearrangement of the monomeric species, Me2Sn[OC(O)OCH3]2. The process results in the transfer of a methyl group from one methyl carbonate to the other via a 4-membered or 6-membered ring forming the Sn-CO3 moiety. In a second stage, methanol reacts with one intermediate and leads to DMC formation and a trimer compound which may allow the regeneration of the reactant. Also a decanuclear tin complex is produced due to the lateral reaction. Finally a catalytic cycle for DMC production in methanol can be elaborated. DFT calculations are in agreement with the experimental data and allow a comparative analysis of reaction channels

Les travaux présentés ont pour objectif la valorisation de déchets industriels riches en carbonates pour la préparation de gels phosphocalciques. Ces gels sont destinés à des applications environnementales. Leur synthèse est basée sur la réaction des carbonates de calcium avec une solution de phosphates solubles à température ambiante et à pression atmosphérique. Le procédé élaboré à l’échelle laboratoire consiste à additionner les réactifs en variant les paramètres expérimentaux tels que le Ca/P, la température et la dilution. Cette méthode a été utilisée pour la synthèse de gels à partir de deux types de déchets industriels. Une synthèse de référence a été définie à base de carbonates de calcium purs. Dans la première partie de ce travail, une caractérisation physico-chimique et thermique des poudres synthétisées a été réalisée par différentes techniques telles que le Microscopie Electronique à Balayage (MEB), la diffraction des rayons X (XRD), la spectroscopie infrarouge à transformée de Fourier (FTIR) et la thermogravimétrie. Les résultats obtenus ont montré la formation de précurseurs de Ca-HAp qui évoluent de phosphates de calcium monocalciques à des particules de Ca-HAp amorphe. Une chronologie de cette évolution a été mise en évidence pour les carbonates de calcium purs et confirmée pour les carbonates de calcium issus des déchets industriels. La transformation des carbonates de calcium a été étudiée en réalisant un bilan massique basé sur la consommation des carbonates de calcium. Ce bilan, réalisé à température ambiante, a confirmé un taux de conversion à plus de 90% pour les carbonates de calcium purs, jusqu’à 70% des carbonates issus du premier type de déchet et 50% des carbonates correspondant au deuxième type de déchet. L’influence de certains paramètres expérimentaux s’est avérée primordiale pour l’amélioration de ce taux de conversion et particulièrement l’augmentation de la température. Dans la deuxième partie de ce travail, les propriétés rhéologiques des gels phosphocalciques ont été étudiées. Le suivi de la viscosité et des caractéristiques élastiques a permis de mettre en évidence la formation d’un gel viscoélastique qui pourrait présenter de nombreux avantages dans des applications environnementales. / The aim of this research was the valorization of industrial wastes rich in carbonates to prepare calcium phosphate gels for environmental applications. The phosphocalcic gel was prepared by precipitation from calcium carbonate industrial waste and a phosphate solution. The process consisted in mixing the reagents under a set of variable parameters (pH, Ca / P, temperature, dilution) to study the influence of each parameter on the conversion rate and the adsorption properties of the synthetized material. A reference hydroxyapatite was prepared following the same procedure with a commercial carbonate grade (98% wt), in order to compare with the waste-made hydroxyapatite. The characterization and chemical analysis of synthetized hydroxyapatites were carried out by means of rheology, particle size, Scanning Electron Microscopy, BET, ThermoGravimetric Analysis – Differential Scanning Calorimetry, X Ray Diffraction and Infrared spectroscopy (Fourrier Transformation Infra Red) analysis. The results obtained led to find out the chronology of the carbonates conversion into Ca-Hap precursors and particles of amorphous Ca-HAp. The kinetics show that the conversion rate is about 90% (wt) for pure CaCO3, 70% for the first waste and 50% for the second waste. Monitoring the viscosity and elastic properties has allowed us to demonstrate the formation of a viscoelastic gel. The synthesis of an elastic gel of calcium phosphate using CaCO3 waste seems to be a promising way to transform calcium residues into a valuable sorbent. Valorization of this gel in environmental applications for pollution remediation seems to be an advantageous perspective.

L’objectif de ce travail de thèse a été d’évaluer les propriétés inhibitrices de corrosion d’un traitement multifonctionnel utilisé dans l’industrie pétrolière. Dans la première partie de la thèse, l’influence des conditions hydrodynamiques, du temps d’immersion et de la température sur les processus de corrosion de l’acier API 5L-X65 en milieu CO2 en l’absence d’inhibiteur a été étudiée par des mesures électrochimiques (courbes de polarisation, courbes de Levich et spectroscopie d’impédance électrochimique) avec une électrode à disque tournant. A partir de ces essais, la vitesse de corrosion a été calculée pour les différentes conditions expérimentales. L’analyse couplée des résultats électrochimiques et des analyses de surface suggèrent la formation d’une couche de produits de corrosion, principalement de carbonate de fer qui recouvre la surface du métal et conduit à la diminution de la vitesse de corrosion quand le temps d’immersion, la vitesse de rotation et la température augmentent. La deuxième partie de la thèse a été consacrée à l’évaluation d’un traitement multifonctionnel contre la corrosion. Ce traitement est composé principalement de produits extraits de l’Aloe Vera (gel de l’Aloe Vera et « acibar »). Ces produits ont été choisis car ils empêchent la formation simultanée d’hydrates et de carbonate de calcium. Ces composés « verts », ainsi que la dodécylamine, qui est un inhibiteur de corrosion commercial, ont été testés à l’aide des mesures électrochimiques et par perte de masse afin de comparer leur efficacité et d’évaluer un possible effet de synergie lorsqu’ils sont utilisés en mélange. Les produits testés séparément ont un pouvoir protecteur comparable et il n’a pas été mis en évidence d’effet de synergie. En revanche, il a été montré que les composés sont compatibles entre eux. Ceci constitue un point très important pour l’utilisation de ces traitements qui permettent d’augmenter la fiabilité et la rentabilité pour la production du pétrole et du gaz. / The objective of this work was to evaluate the corrosion inhibitive properties of a multifunctional treatment used in the petroleum industry. In the first part of the thesis, the influence of hydrodynamic conditions, immersion time and temperature on the corrosion process of API 5L-X65 steel in CO2 medium in absence of inhibitor was studied by electrochemical measurements (polarization curves, Levich curves and electrochemical impedance spectroscopy) with a rotating disk electrode. From these tests, the corrosion rate was calculated for different experimental conditions. The analysis of the electrochemical results and surface analyses suggest the formation of a layer of corrosion products, mainly iron carbonate which covers the metal surface and leads to the decrease of the corrosion rate when the immersion time, the rotation speed and temperature increase. The second part of this work was devoted to the evaluation of a multifunctional treatment against corrosion. The treatment is mainly composed Aloe Vera extracts (Aloe Vera gel and "acibar”). These products were chosen because they prevent the simultaneous formation of hydrates and calcium carbonate. These "green" compounds and dodecylamine, which is a commercial corrosion inhibitor, were tested using electrochemical measurements and by mass loss in order to compare their efficiency and to evaluate a possible synergistic effect when they are used as a mixture. The products tested separately have a similar efficiency and did not reveal any synergistic effect. However, it was shown that the compounds are compatible. This is an important point for the use of these treatments which can increase the reliability and profitability for the production of oil and gas.