Carbon dioxide dissolution into water is a ubiquitous chemical process on earth, and having a full understanding of this process is becoming ever more important as we seek to understand the consequences of 250 years of exponentially-increasing anthropogenic C02 emissions to the atmosphere since the start of the Industrial Revolution. We examine the dissolution of C02 into water in a number of contexts. First, we analyse what happens to a range of chemical species dissolved in water following an injection of additional C02. We consider the well-mixed problem, and use the method of matched asymptotic expansions to obtain new expressions for the changes in the species' concentrations with time, the new final chemical equilibrium, and the time scales over which this equilibrium is reached, as functions of time, the parameters and the initial condition. These results can be used to help predict the changes in the pH and concentrations of dissolved carbonic species that will occur in the oceans as a result of anthropogenic C02 emissions, and in saline aquifer formations after pumping C02 deep underground. Second, we consider what happens deep underground in a saline aquifer when C02 has been pumped in, spreads through the pore space, and dissolves into the resident water, when advection, diffusion, and chemical reaction have varying levels of relative importance. We examine the length scales over which the dissolved C02 will spread out through an individual pore, ahead of a spreading drop of C02, and the concentrations of the different chemical species within the pore, in the steady-state case. Finally, some experiments have been carried out to investigate the effect of an injection of gaseous C02 on the chemical composition and pH of a saturated limestone aquifer formation. As the C02 enters the soil, it dissolves into the water, and we model the changes in the chemical composition of the water/limestone mixture with time.

The research described in this thesis relates to the development and optimisation of a novel polymerisation reaction and its subsequent use in the generation of novel ‘Polymers of Intrinsic Microporosity’ (PIMs). The polymerisation reaction takes monomers containing two or more aromatic amines and fuses them together by the synthesis of a bridged bicyclic heterocyclic link called Tröger’s base (TB). This link not only strongly holds the polymer chain together, but also provides a site of contortion, which is necessary for a PIM to exhibit microporosity. The first part of this work introduces the background to the research, detailing the reasons behind the development of a new class of PIM and the competitor materials. Following this is detailed the optimisation of the TB forming condensation reaction and the synthesis of a variety of amine functionalised monomers. Also described in this section is the optimisation of a second condensation reaction used for the synthesis of a family of compounds based around a coumaron framework, all of which lack amine functionality. This precedes discussion of X-ray crystal structure analysis of several TB model compounds, amine functionalised monomers and coumaron-based compounds. After this is a description of the development of the novel TB polymerisation reaction, the results of the TB polymerisation of the amine functionalised monomers, characterisation of the successful polymers and the attempted polymerisation of two coumaron-based monomers. The final part of this work reports the experimental procedure for each compound together with full characterisation. In closing, the TB polymerisation reaction has successfully used for the production of highly stable and soluble PIMs exhibiting a wide range of microporosity, with BET surface areas ranging from 0 m2/g to 1035 m2/g. A few of these PIMs have been found to have excellent molecular weight, capable of forming strong membranes, suitable for gas separation, most notably for the purification of oxygen, hydrogen and carbon dioxide from nitrogen. Conversely, the synthesis of coumaron-based PIMs proved unsuccessful, but nevertheless this research should allow the future synthesis of a coumaron-based PIM. The research on TB polymerisation detailed in this thesis has contributed towards an International Patent122 and a paper in Science123so can be deemed to have been successful by that measure.

No description available.

The flux of carbon in to and out of the atmosphere exerts a fundamental control over the Earth's climate. The oceans contain almost two orders of magnitude more carbon than the atmosphere, and consequently, small fluctuations within the oceanic carbon reservoir can have very significant effects on air-sea CO₂ exchange, and the climate of the planet. Pelagic carbonates represent a major long-term flux of carbon from the surface ocean to deep-sea sediments. Within sediments, the biologically produced carbonates act as a longterm carbon store, but also as chemical recorders of past surface ocean conditions. Counterintuitively, despite the production and sedimentation of carbonate acting as a CO₂ sink, over periods shorter than the mixing-time of the ocean, the pH change associated with calcium carbonate precipitation enriches the surface waters in CO₂ and elevates the equilibrium value of gaseous exchange with the atmosphere. Coccolithophores, ubiquitous marine photosynthetic plankton, produce calcium carbonate plates, coccoliths, which account for around one third of all marine calcium carbonate production. Sedimentary coccoliths therefore represent a valuable repository of surface ocean geochemical data, as well as a very significant carbon-cycle flux. This thesis examines how the mass of calcium carbonate produced by coccolithophores has changed in response to rising levels of atmospheric CO₂. A -40% increase in average coccolith mass over the last 230 years, paralleling anthropogenic CO₂ release, is demonstrated within a high-accumulation rate North Atlantic sediment core. Additionally, a flow-cytometry method is presented, which enables the automatic separation of coccoliths from clay particles in sedimentary samples, representing the first step in a coccolith cleaning procedure, which should ultimately enable down-core measurements of coccolith trace-element/calcium ratios. Complementing this work I describe results from continuous dissolution analysis of cultured coccoliths which allows a first-order evaluation of trace-element partitioning into coccoliths produced by the species Coccoliths pelagicus, and present a conceptual methodology to allow the determination of single-species coccolith chemical data.

It is now widely believed that globally averaged temperatures will rise significantly over the next 100 years as a result of increasing atmospheric concentrations of greenhouse gases (GHG) such as carbon dioxide. Responses to the threat of future climate change are both adaptations to new climate conditions, and mitigation of the magnitude of change. Mitigation can be achieved both through reducing emissions of greenhouse gases and by increasing storage of carbon in the earth system. In particular it is thought that there is potential for increased storage of carbon on land in soils and growing vegetation. There is now a need for research on the potential impacts of changing land use on terrestrial carbon storage, in particular as rapid land use and land cover change has taken place in most of regions of world over the past few decades due to accelerated industrialization, urbanization and agricultural practice. This thesis has developed a novel methodology for estimating the impacts of land use and land cover change (LULCC) on terrestrial carbon storage using Geographic Information Systems and Optimization modelling, using a regional case study (the Tamar Valley Catchment, southwest England) and drawing entirely on secondary data sources (current distributions of soils and vegetation). A series of scenarios for future land cover change have been developed, for which carbon storage, GHG and energy emissions amount have been calculated over the short, medium and long term (2020, 2050 and 2080). Results show that in this region, improving permanent grassland and expanding forestry land are the best options for increasing carbon storage in soils and biomass. The model has been validated using sensitivity analysis, which demonstrates that although there is uncertainty within the input parameters, the results remain significant when this is modelled within the linear programme. The methodology proposed here has the potential to make an important contribution to assessing the impacts of policies relating to land use at the preparation and formulation stages, and is applicable in any geographic situation where the appropriate secondary data sources are available.

A cleaner use of fossil fuels supported by Carbon Capture and Storage (CCS) techniques is considered to be one of the main short-term strategies for addressing the global climate change problem. However, potential CO2 or CO2/SO2 seepage during some of the phases of a CCS project not only reduces its performing efficiency, but also impacts the local environment, which could have further impacts on human health. It is therefore essential to assess the potential risks and provide evidence that the impacts are well understood. Moreover, studying the effects of CO2 leakage is useful for identifying monitoring parameters if the leakage does happen, leading to the development of new approaches in detecting CO2 leaks. Accordingly, this research is carried out to assess the relevant impacts on the local environment of CO2 leakage, focusing on the environmental impacts caused by CO2 seepage associated with various soil types, mostly on the soil geochemical changes, which is currently lacked. As a cost effective approach, this research was carried out with two types of well controlled laboratory experiments: Stage I- Closed reactor experiments and Stage II- A flow through column system (designed by the author). As a supplementary study to the research of the ASGARD site, Stage I experiments were carried out with soil samples collected from the ASGARD site and gave directions for Stage II column system design. Stage II experiments were carried out with two contrasting mono-mineral sediments considering sensitivity to CO2 gas, Trucal 5 and Trucal 6 (limestone sand of different particle size) and silica sand. Certain limitations of this research have to be considered. Firstly, highly idealised samples were used in the experiments instead of true soils and there was no heterogeneity in the samples used, which is not representative of the full complexity of a natural system. Secondly, the scale limitation of the laboratory work would lead to a higher gas/mineral ratio compared with field conditions. Therefore, results from the laboratory work cannot simply represent all the soils in the field, except the specific soil related problem and the results are better to be used to demonstrate the conditions where the soils/sediments are surrounded by high levels of CO2, such as the ones nearby a leaking injection well or along a fracture/fault. Nevertheless, this study is believed to provide a step towards understanding the potential impacts of CO2 seepage in soil, and potentially to be useful as a mean of identifying indicators of related problems when applying to the full-scale design, leading to the development of new approaches in detecting CO2 leaks. Throughout the experiments, the experimental apparatus (the continuous column system) newly designed by the author was run successfully, providing an alternative way in respect to the majority of soil-column studies for assessing issues of CO2 seepage. The main impact of CO2 emissions on soil properties is to drop the pH which triggers metals mobilisation from soils (all within safety limits to plant growth). The change of pH associated with both limestone and silica sand indicates that pH is an excellent parameter to indicate the CO2 intrusion into sediments once the background is set. The response of calcium (Ca) to CO2 flux highlights that carbonate minerals are sensitive to CO2 increase and could possibly be used as a parameter to monitor CO2 leakage once the baseline for the pre-injection concentration is set.

L’utilisation des microorganismes marins ou terrestres pour la séquestration à long terme du CO2 est une des solutions envisagées pour diminuer la teneur en CO2 dans l'atmosphère. Le travail de cette thèse se concentre sur les microorganismes calcifiants, et notamment les cyanobactéries, qui peuvent fixer du CO2 sous forme de biomasse et carbonate de calcium. Ce dernier, insoluble dans l’eau, précipite et peut donc constituer un puits à long terme. La compréhension des mécanismes de calcification induits par les cyanobactéries et la possibilité de contrôler ces processus sont nécessaires pour développer une technologie de séquestration du CO2. Cette biotechnologie pourrait constituer une alternative à la technologie de capture et stockage géologique du CO2. Synechococcus PCC8806 une souche marine de cyanobactérie purifiée à l'Institut Pasteur de Paris est utilisée comme organisme au cours du travail expérimental réalisé dans le cadre de cette thèse. Le premier résultat important de cette thèse est le développement d'une stratégie analytique ayant permis d'accéder à un bilan de masse carbone et calcium au cours d'une culture de cyanobactérie sur hydrogénocarbonate. La mise en œuvre de cette stratégie au cours de différents essais réalisés dans le cadre de ce travail a permis par ailleurs de quantifier avec précision la production de carbone organique (biomasse) et de carbone inorganique (CaCO3) en fonction du calcium et du carbone inorganique présent dans les milieux de culture. Nous avons ensuite étudié la précipitation de la calcite au cours de la croissance de Synechococcus PCC8806 en présence de calcium. Pour cela les conditions de culture ont été variées de telle sorte que la survenue des évènements de précipitations a pu être comprise ainsi que l'influence de sites de nucléation mis en évidence. Le grossissement des cristaux a également été étudié attentivement par microscopie électronique à balayage. Une autre partie de ce travail a permis d'identifier la source de carbone inorganique utilisée par Synechococcus PCC8806 pour la photosynthèse. Cela a été l'occasion de réécrire les équations liées aux transferts entre le CO2 atmosphérique et le système carbonaté, ainsi que les équations de photosynthèse en fonction des conditions de disponibilité des deux sources de carbone inorganique (CO2 et hydrogénocarbonate). De plus ont pu être mis en évidence, les effets des phases diurne et nocturne de la croissance de cyanobactéries sur les équilibres du système carbonaté et le pH. Ce travail a également permis de déterminer les vitesses de croissance des cyanobactéries et donc de calculer des rendements de croissance par unité de surface. Cela permettra à terme d'optimiser la production de biomasse et de calcite dans un procédé industriel / The use of marine or terrestrial microorganisms for long-term sequestration of CO2 is a possible solution to reduce the CO2 content in atmosphere. This thesis work focuses on calcifying organisms, in particular the cyanobacteria, which can fix CO2 as biomass and calcium carbonate. The latter is insoluble in water; precipitates may therefore constitute a long term sink. Understanding of the calcification mechanisms induced by cyanobacteria and the possibility of controlling these processes are necessary to develop a technology for CO2 sequestration. This biotechnology could be an alternative technology to CO2 capture and geological storage. Synechococcus strain PCC8806, marine cyanobacteria purified by the Institute Pasteur de Paris is used during the experimental work in this thesis. The first important result of this work is to develop an analytical strategy that allowed access to a mass balance of carbon and calcium in a cyanobacteria culture on hydrogencarbonate. The implementation of this strategy in various tests of this work has also allowed to accurately quantify the production of organic carbon (biomass) and inorganic carbon (CaCO3) according to the calcium and Ci introduced (hydrogencarbonate) in the medium. We then studied the calcite precipitation during growth of Synechococcus PCC8806 in the presence of calcium. For that, culture conditions were varied in order to understand the occurrence of precipitation events and the influence of nucleation sites. The development of crystals has also been carefully studied by scanning electron microscopy. Another part of this work has identified the inorganic carbon source used by Synechococcus PCC8806 for photosynthesis. This was an opportunity to rewrite the equations related to transfers between atmospheric CO2 and the carbonate medium, as well as the equations of photosynthesis depending on the conditions of availability of two sources of inorganic carbon (CO2 and hydrogencarbonate). In addition, we have revealed the effects of diurnal and nocturnal phases of the growth of cyanobacteria on the carbonate system balance and pH. This work also allowed estimating the cyanobacteria growth rates and thus calculating growth yields per unit area. This will ultimately optimize biomass and calcite production in an industrial process

The tropical forests on the island of Borneo are among of the richest in the world in terms of tree diversity, and their capacity to store a large reservoir of carbon. The Southeast Asian forests are fundamentally different from Neotropical and African forests, with their single-family dominance by dipterocarp trees, and with inherently greater stature and biomass. The carbon productivity and allocation in Asian tropical forests is still poorly quantified, and their responses to environmental drivers are still poorly understood. Almost all recent advances in tropical forest carbon cycling research have occurred in the Neotropics, with very few studies in Asia. The principal aim of this thesis is to quantify the carbon budget of a lowland dipterocarp forest in the Lambir Hills National Park, Miri, Sarawak, Malaysian Borneo. I examined and explored the productivity and carbon cycling processes and their responses to environmental factors across two major and contrasting soil types, in particular the clay and sandy loam soils. I recorded and analysed the Net Primary Productivity (NPP) and respiration for the above- and below-ground components, and observed the responses to seasonal variation and environmental drivers. Total soil respiration was relatively high and contributed a great deal to ecosystem respiration. Variation in soil respiration rates appeared closely related to soil moisture content. I found a strong diurnal cycle in soil respiration. On the basis of the first soil carbon dioxide (CO2) efflux partitioning study undertaken in a tropical forest, the diurnal cycle in total soil respiration appeared to be entirely driven by the diurnal cycle in litter respiration, and in turn litter is strongly controlled by moisture. There was little seasonal variation in allocation of net primary productivity (NPP), but there was evidence showing potential inter-annual variability for several components of NPP. Further, the allocation of NPP showed a strong seasonal shift between the forest plots on clay and sandy loam soils. Combining all the data measured and obtained in this D.Phil. thesis, the overall carbon budget assessed in this lowland dipterocarp forest showed a high level of agreement with other studies in Asia using micrometeorological techniques and the situation appears to be comparable to tropical forests in Amazonia. The key difference is that the aboveground NPP is higher and is the largest component contributing to the overall carbon budget, with relatively higher carbon use efficiency (CUE). The lowland dipterocarp forest in Lambir shows higher allocation in the above-ground NPP, and there were also differences in NPP and its allocation between sandy and clay-rich plots.

Cette thèse s'inscrit dans les problématiques liées au captage de CO2 en postcombustion et au traitement du gaz naturel. Une méthodologie a été développée dans le cadre de cette thèse afin de comprendre la cinétique d'absorption de CO2 par des solutions aqueuses de mélange d'amines. Cette méthodologie comporte l'acquisition de données expérimentales à travers un outil expérimental de type film tombant, ainsi que l'exploitation de ces données via un modèle couplant l'ensemble des phénomènes physico-chimiques mis en oeuvre au sein du réacteur. Cette méthodologie a dans un premier temps été appliquée à l'étude du système CO2-pipérazine, pour lequel l'extrapolation de la cinétique chimique de la littérature a été validée dans des gammes étendues de températures, concentrations d'amines et de taux de charge en CO2 (ratio entre le nombre de mol CO2 et le nombre de mol d'amine en solution). La cinétique d'absorption du CO2 dans le mélange complexe N-méthyldiéthanolamine-pipérazine, a ensuite été examinée. La synergie entre les deux amines pour absorber le CO2 ainsi que l'influence du taux de charge sur la cinétique chimique du système ont été quantifiées. Cette méthodologie sera mise en ?uvre au sein des projets de recherche IFPEN afin de quantifier la cinétique chimique des systèmes CO2-mélanges d'amines dans le cadre des procédés de captage de CO2 et de désacidification de gaz naturel. Paramètre essentiel de la modélisation du transfert gaz-liquide, une connaissance fine de la cinétique d'absorption du CO2 permet, in fine, d'améliorer la fiabilité du design des colonnes d'absorption industrielles / Processes based on chemical absorption are widely used for removing CO2 contained in natural gas, hydrogen or flue gas. Mixtures of amines can be used as a solvent for these applications in order to accelerate CO2 mass transfer towards the liquid phase, while keeping a low energy consumption to be regenerated. A methodology has been developed in the framework of this PhD to understand the kinetics of the absorption of CO2 into mixtures of amines. Experimental data provided by a wetted wall column apparatus have been interpreted by a rigorous model taking into account all phenomena occurring within the reactor. This work was firstly dedicated to study the kinetics of the absorption of CO2 by aqueous piperazine solutions. The extrapolation of PZ / CO2 kinetics given by the literature has been validated in a wide range of operating conditions. The kinetics of the absorption of CO2 by mixtures of N-methyldiethanolamine and piperazine has then been assessed. The synergy between both amines at low loading allowing the CO2 mass transfer to be accelerated as well as the impact of the CO2 loading on the absorption kinetics have been quantified. This methodology will be used at IFP Energies nouvelles in order to study the kinetics of the absorption of CO2 by mixtures of amines, in the framework of CO2 postcombustion capture and natural gas treatment processes development. The knowledge of the kinetics of the CO2 absorption by mixtures of amines will allow to enhance the reliability of the absorption column design

Le procédé Solvay génère d’énormes quantités de saumures résiduaires au pH alcalin contenant portlandite, brucite et silicates de calcium hydratés. La carbonatation conduit à un abaissement du pH, ce qui favorise la formation de deux phases majoritaires : la calcite et le gypse. L’objectif de la thèse est de valoriser les saumures résiduaires carbonatées par séparation des phases en colonne de flottation. L’étude de la carbonatation en réacteur batch, puis en colonne de carbonatation pilote montre qu’il est préférable de ne pas carbonater les saumures résiduaires jusqu’à l’équilibre thermodynamique. En effet, la mise en solution de métaux lourds intervient à partir d’un pH de l’ordre de 7,5, ce qui limiterait les rejets des saumures dans l’environnement. En outre, une carbonatation brusque et incomplète est souhaitable pour une meilleure séparation des phases par flottation. Les essais de flottation réalisés sur une colonne de 7,6 cm de diamètre et de 3 m de haut ont montré une faisabilité de la séparation des deux minéraux calciques avec l’oléate de sodium comme collecteur malgré une abondante littérature incitant à la prudence. La différence entre la taille des particules de carbonates et celle des particules de sulfates et leurs hydratations de surfaces, ainsi qu’une force ionique élevée du milieu permettent une bonne séparation des phases. Une étude des saumures synthétiques permet de mettre en évidence le rôle des cations métalliques (nature, rayon, charge…) sur la coalescence des bulles dans les conditions dynamiques et dans un milieu à forte force ionique. Une étude des paramètre de fonctionnement effectué sur une colonne de 30,5 cm de diamètre et de 10 m de haut ont permis la modélisation du procédé de flottation en colonne dans le but de proposer une procédure de dimensionnement du procédé industriel. La confrontation des résultats de simulation aux résultats réels permet la détermination des intensités des microprocessus de flottation (attachement/détachement), et conduit à la proposition d’une installation industrielle avec deux colonnes de flottation en série / Solvay process generates huge amounts of waste brines at alkaline pH containing portlandite, brucite and calcium silicate hydrates. Carbonation leads to lowering of pH which favors formation of two predominant phases: calcite and gypsum. The aim of this thesis is to develop carbonated waste brines valorization by phase separation in flotation column Study of carbonation in a batch reactor and in a carbonation pilot column shows it is preferable not to carbonate waste brines until thermodynamic equilibrium. Indeed dissolution of heavy metals occurs from a pH of about 7.5 thereby limiting discharge of brines in the environment. In addition, a sudden and incomplete carbonation is appropriate for phase separation by flotation. Flotation tests carried out in a 7.6 cm diameter and 3 m high column showed feasibility of the separation of the two calcium minerals using sodium oleate as a collector despite abundant literature for caution. The differences between the particle size of carbonates and sulfates and their surface hydration, as well as the high ionic strength of the medium allow an efficient separation of phases. Study of synthetic brines highlights the role of metal cations (nature, radius, charge…) on bubble coalescence in dynamic conditions in an environment with high ionic strength. Study of operation parameter performed on a 30.5 cm diameter and 10 m high column enabled the modeling of the column flotation process in order to provide a scale-up procedure of industrial process. Comparison of simulation results with actual results allows the determination of intensities of flotation subprocesses (attachment/detachment), and led to the proposal of an industrial plant with two flotation columns in series