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The use of calcium oxide as a regenerable sorbent for CO2 capture has been a subject of diverse research because of the enormous benefits it offers towards decarbonizing the power industry particularly for post-combustion CO2 capture applications. These benefits include: the low energy penalty imposed on power stations (estimated as 6- 8%), it’s benign nature in comparison with synthetic amine based sorbents, its CO2 removal ability to very low concentrations (<5%) at temperatures between 450-750°C, the availability of naturally occurring limestone which is extremely cheap and the application of deactivated sorbent as a source of cheap de-carbonised CaO to the cement industry. However, calcium looping technology has its own shortfall which is mainly sorbent deactivation with increasing loop cycle number, a consequence of mainly sorbent sintering (as a result of employed high sorbent regeneration temperature >850°C) and to a lower extent sorbent fragmentation. This poses the need for fresh sorbent make-up and increases the cost of operation from cost of additional raw material and increased energy penalty from fresh sorbent calcination. In order to successfully eliminate this downside of calcium looping, the behaviors of sorbents from different limestone precursors on sintering need to be understood. This research aims to understand the role played by mineralogy and micro-structural properties of precursor limestone on the sintering ability and attrition of the resultant CaO sorbent post-cycling in order to inform material selection and to utilize naturally occurring heterogeneities (e.g. silica and other impurities). This is to form a possible standard for screening limestone samples to ascertain their suitability for calcium looping and thereby reduce the cost of the process through effective raw material selection. Chemical composition analysis was done using XRF and mineralogy analysis using XRD. Textural properties were examined using MIP and nitrogen physisorption. Sorbent’s CO2 conversion ability was observed using TGA and a bubbling fluidized bed. Sintering was estimated in terms of decline in specific surface area and qualitatively described using SEM and STEM. Sorbent attrition was estimated from the difference in sorbent mass within the 500-710 nm particle size range pre and post loop cycling.

The Trans-Suture Suite (TSS) of granitic plutons located in Northern Britain span the Iapetus Suture and represent a particularly enigmatic stage of post-Caledonian Devonian magmatism. Despite calc-alkaline affinities, proximity to the Iapetus Suture precludes a direct relationship to active subduction. Furthermore, the absence of inherited zircons distinguishes the TSS from plutons of a similar age throughout the Scottish Highlands, and is not easily reconciled with the abundance of peraluminous and S-type granites. Micro-analytical techniques are employed to analyse accessory zircon and apatite from three TSS plutons (Criffell, Fleet and Shap) in order to investigate connections between magmatic and tectonic processes within a continental suture zone. Accessory minerals contain a robust and accessible record of magma evolution. However, their trace element compositions are shown to document the final stages of pluton emplacement only, and are determined primarily by competitive crystallisation of other accessory phases at shallow crustal levels. By contrast, whole-rock compositions record an earlier stage of magma evolution that occurred in deeper and open-system crustal hot zones. The absence of inherited zircon in the final crystal assemblage reflects resorption during rapid and potentially adiabatic ascent of super-liquidus and water-rich magmas from the crustal hot zone. The concentrations of REE in apatite inclusions decrease with increasing crystallisation of other accessory minerals and in some samples have been distinguished on the basis of their host phase. In metaluminous granodiorites, no preferred crystallisation sequence is observed between host phases. In peraluminous samples, zircon-hosted apatite compositions appear more primitive compared to those hosted by other phases and reflects earlier saturation of zircon in these magmas. The isotopic record of zircon is shown to be biased towards earlier stages of magma evolution in peraluminous magmas and provides a means of assessing zircon isotope compositions in the context of often protracted histories during silicic magma evolution. The Mn content of apatite varies independently to whole-rock composition, correlating positively with decreasing oxygen fugacity and indices of increasing reduction. Apatite is proposed as a robust and effective redox proxy with application to magmatic, detrital and lunar studies of redox conditions. Zircon O-HfU- Th-Pb isotope compositions have identified increasing degrees of compositional heterogeneity in more silicic components of the TSS, including the involvement of more mafic magmas in the generation of the large S-type pluton of Fleet. Compositional trends between zircons from plutons emplaced on both sides of the Iapetus Suture are used to identify a common Avalonian component beneath the Southern Uplands and English Lake District related to Avalonian underthrusting beneath the Laurentian margin during the late Caledonian. New geochronological dating indicates that pluton emplacement occurred during periods of both pre- and post-Acadian transtension. The distinguishing characteristics of these plutons relative to other Caledonian plutons reflect their unique emplacement into the hydrated lithosphere of the Iapetus Suture Zone. Oxygen isotope disequilibrium between the magmatic compositions recorded by zircon and those of the whole-rock and some quartz crystals reflect hydrothermal alteration of the latter two archives. Hydrothermal alteration and exchange caused by 18O-rich magmatic fluids has elevated the 18O compositions of the whole-rock and some quartz crystals, with most disequilibrium observed around the outer margins of the plutons due to further fluid interaction with local 18O-rich sediments. The hydrothermal history of the TSS is markedly different from that of the British Tertiary Igneous Province where hydrothermal alteration resulted from circulation of meteoric water, reflecting significantly different magmatic and emplacement histories.

The Back to Nature project was developed as a collaborative doctoral award between the British Museum and the School of Geography and the Environment, University of Oxford. The British Museum has a large collection of limestone artefacts, some of which have deteriorated to an extent that a consolidation treatment, to improve internal cohesion, has been deemed necessary to ensure the value of the artefacts is maintained. Previous consolidation practices within the museum had centred on the use of organic consolidants. In the past, inorganic consolidants had been considered ineffective chiefly due to poor penetration depth and inconsistent deposition within the stone. Recent scientific developments within conservation, particularly the development of nano-limes, coupled with a trend towards treatments offering physical and chemical compatibility, led to the British Museum reconsidering the use of inorganic consolidants. Three inorganic consolidants: ammonium oxalate treatment, Calcite In-situ Precipitation System (CIPS), and CaLoSil have been investigated by the Back to Nature project to assess their potential for use on the British Museum’s deteriorated limestone artefacts. The investigation involved a developmental sequence of four experimental phases to assess the effectiveness of each consolidant upon freshly cut, artificially pre-weathered, and naturally weathered stone samples. In all experiments an organic silane Wacker SILRES BS OH 100 was used as a comparison. A variety of analytical methods were used including: Equotip, GrindoSonic, Scanning Electron Microscopy, Karsten Tubes, Drilling Resistance Measurement System, spectrophotometry, X-ray Diffraction and Ion Chromatography. Experiments show that the CIPS treatment could hold promise for use as a consolidant. Ammonium oxalate only appears to provide consolidation at the surface level, and CaLoSil would need modifying and more investigation before using in the museum environment. The differences noted between experiments on artificially weathered and naturally weathered stone indicate that a two-step process, involving testing on both types of samples, would give the best indication of consolidant effectiveness. High variability between samples shows a large number are needed to give an accurate interpretation of change due to consolidation.