Carbon Capture and Storage (CCS) is one option to meet the increasing energy demand as well as reduce net CO2 emissions to the atmosphere. Chemical Looping Combustion (CLC) is a promising CCS technology proposed to meet the challenge of mitigating the carbon dioxide (CO2) emissions. CLC process can be based on interconnected fluidized beds, consisting of air reactor, fuel reactor and oxygen carrier (OC) which undergoes redox reactions while it circulates between the reactors. The main products are CO2 and water, thus eliminating the need of an additional energy intensive CO2 separation. The feasibility of CLC depends on the oxygen carrier's (OC) ability to transfer O2 from air reactor to fuel reactor and have sufficient oxygen capacity, high reactivity and withstand a high number of redox cycles without significant loss in performance. OCs based on transition metal oxides of Cu, Co, Fe, Mn and Ni has been explored. Nevertheless, research is focused on improving the OCs performance with the aim to overcome their various practical limitations. Mechanical mixing and impregnation which fails to provide a high degree of dispersion and high metal loading respectively are commonly used for OC synthesis. Very few works have been reported for Mn-oxide and co-precipitated oxygen carriers. The few studies on co-precipitated OCs mainly use strong base as precipitants. One drawback to this is the repetitive washing of precipitate to remove excess alkali ions and controlled loading of active components cannot be easily obtained. In this study, weak base instead of strong base was used in the synthesis of OCs. This is the first time this controlled approach has been applied to prepare oxygen carrier in CLC for manganese and iron. This thesis is a novel research on development and detailed investigation of co-precipitated Mn-oxide and Fe-oxide OCs with ZrO2 and combined ZrO2–CeO2 support. The reaction kinetics, stability and oxygen transfer capacity (OTC) of the OCs were studied by TGA up to 1173 K in H2, CO and CH4. Characterization of physical and chemical structures of particles was obtained by SEM-EDX, XRD, BET and pycnometer. The result reveals that regardless of the composition of the co-precipitated oxygen carriers, there was no interaction of the metal oxides with the support material which could have altered the thermodynamics of the redox system. Furthermore, co-precipitated Mn/Zr and Fe/Zr OCs were more reactive than their counterpart prepared by impregnation and mechanical mixing. Also, changes in reactivity and OTC suggest that the synergistic effect varies with ratios of the single oxides in the bimetallic OCs. Co-precipitated Mn-rich oxygen carriers were more reactive than Fe-rich OCs. Interestingly, OCs with zirconia-ceria support exhibited activation tendency behaviour. Moreover, the use of combined zirconia-ceria for bimetallic Mn-Fe oxide reversed the characteristic progressive decrease in the performance of the OC with equimolar composition. For co-precipitated Mn-Fe Oxide oxygen carriers, zirconia content of 44 wt. % is sufficient to maintain the mechanical integrity of the particles during redox reactions compared to a zirconia content of 20 wt. %. This research has resulted in the development of highly reactive and stable oxygen carriers, which are promising for CLC. Mn/Zr OC reached full conversion in less than 48 secs and bimetallic Mn-Fe OCs reached 30% conversion in less than 43 secs in CH4 and maintained stability in a thirty multicycle test. The redox reaction kinetics of the most reactive oxygen carrier using CH4, H2, CO and air was investigated at isothermal conditions (973-1173 K) to determine the kinetic parameters. Models of the reduction and oxidation reactions were selected by using a model fitting method. The nucleation model was the most statistically significant and suitable model for describing the reduction and oxidation behaviour of the oxygen carrier. The values of activation energy obtained for the reduction reaction in CH4, H2 and CO were 142.8 KJ/mol, 32.95 KJ/mol and 26.37 KJ/mol respectively. Whereas, for the oxidation reaction, the activation energy obtained using air was 28.83 KJ/mol. In the application of co-precipitation technique for the synthesis of multicomponent materials, a heterogeneous product could be obtained from using improper preparation conditions. Results from this research have demonstrated that, the application of the well-designed co-precipitation procedure effectively produced composite materials (up to four co-precipitated mixed metal oxides) with controlled compositions and homogeneous dispersion. Furthermore, this study provides insight into the fundamental behaviours of co-precipitated manganese and iron based oxygen carriers to aid the design and optimization of future materials development.

Carbon Capture and Storage (CCS) has been considered as one of the most promising techniques to reduce anthropogenic CO2 emissions in the atmosphere. As an alternative to replace the traditional technology of aqueous amine scrubbing, solid adsorbents looping technology (SALT) has attracted growing attention. Among various solid adsorbent materials, carbon-based materials with unique properties such as wide availability, relatively low cost, highly porous structure ease of regeneration, and stable cyclic performance, have been considered as promising candidates at both low pressure and moderate to high partial pressure. In this PhD research, activated carbon spheres derived from two different precursors, which are phenolic resin and coal-tar pitch, have been prepared and modified with potassium intercalation to improve CO2 capture performance for post combustion carbon capture. The project aims to investigate the factors that affect CO2 adsorption performance for post combustion carbon capture. Firstly, series of spherical activated carbon beads (with a uniform diameter of ca. 0.6-0.8 mm) derived from phenolic resin have been developed and characterised. The results show that the surface polarity can be enhanced by potassium intercalation. The intercalation of potassium significantly increased the CO2 capacity of the AC beads by a factor of up to 2 at 0.15 bar while the effects of the treatment on their mechanical strength and morphological features were negligible at KOH/AC mass ratios of 0.3 and below. The factors other than adsorption that affect the performance of phenolic resin derived carbon spheres were also investigated in terms of adsorption kinetics, cyclic performance, heat of adsorption, the effect of moisture, and regeneration heat. Secondly, coal tar pitch derived activated carbons, with uniform spherical diameter of 1-2 mm were synthesised via two different activation approaches, which is firstly an initial steam activation followed by KOH activation, and secondly one-step KOH activation, both with mild KOH/carbon mass ratios. Samples prepared with one-step KOH activation method had shown a better microporous structure and a higher CO2 adsorption capacity. Owing to the narrow micropores and K-doping, the samples demonstrated outstanding CO2 capacities at relatively low CO2 partial pressure. Multicycle stability was examined over 50 cycles of adsorption and desorption, and both samples present excellent adsorption kinetics and regeneration ability. Finally, the volumetric CO2 uptake of best performing samples were also calculated and compared with other candidates. Based on our previous results, further investigation towards the influence of precursor materials and correlation between microporosity pore size ranging from 0.4 nm to 2 nm and CO2 uptakes have been carried out. Future work on how to improve the CO2 sorption performances of the studied materials has been proposed.

A rise of 2 oC in the Earth’s temperature is likely to occur when the concentration of CO2 in the atmosphere reaches approximately 450 ppm. CO2 emissions are closely related to the continual use of fossil fuels. In order to make fossil fuels sustainable, carbon capture & storage (CCS) is required to reduce CO2 emissions. There are three leading CO2 capture methods, namely post-combustion capture, oxy-fuel combustion and integrated gasification combined cycle (IGCC) pre-combustion capture. CO2 hydrate (CO2:6H2O) formation has been investigated as a way to capture CO2 in the IGCC conditions. The formation of hydrate in this work was experimentally investigated in an isochoric system (batch mode) inside a vertical fixed bed reactor (FBR), also known as high pressure volumetric analyser (HPVA). Standard silica gel with an average particle size of 200-500 µm, mean pore size of 5.14 nm, a pore volume of 0.64 cm3/g and a surface area of 499 m2/g was used as a porous medium. The presence of hydrate in FBR was justified by using graphic methods. The solubility of CO2 in water using Henry’s Law and the experimental pressure–time (P-t) curve were analysed to determine the formation of hydrate. Hydrate formation was confirmed when the mole fraction of CO2 dissolved in water exceeded the Henry’s Law value as well as a two-stage pressure drop in the experimental P-t curve. Initially, various sample preparation methods (methods 1, 2, 3 and 4) were studied leading to the selection of method 4 (the use of vigorous stirring) which had the highest moisture content (14.8 wt%) and the greatest water conversion to hydrate (40.5 mol%) at 275 K and 36 bar in a pure CO2 gas system. Also, high regeneration and repeatability of the results for all samples prepared by method 4 were expected as less water was occluded inside silica gel pores. Further investigations in pure CO2 gas systems highlighted the effect of type of silicas used, the importance of the type of promoters used, the concentration of promoters, experimental driving force, silica pore size, bed height and the amount of moisture content for formation of hydrate. Standard silica gel was the only silica found to show hydrate formation due to the best distribution of pore size. The high amount of bulk water inside zeolites 13X and spherical MCF-17 (21.3 and 50.8 wt% respectively) was the main reason of no hydrate formation observed. Additionally, the combined-promoters designated type T1-5 (0.01 mol% sodium dodecyl sulphate (SDS) + 5.6 mol% tetrahydrofuran (THF)) and type T3-2 (0.01 mol% SDS + 0.1 mol% tetra-butyl ammonium bromide (TBAB)) were the two best obtaining a CO2 uptake of 5.95 and 5.57 mmol of CO2 per g of H2O respectively. Ethylene glycol mono-ethyl ether (EGME; 0.1 mol%) was a good alternative to THF when combined with SDS (0.01 mol%) with a CO2 uptake of 5.45 mmol of CO2 per g of H2O for this combined-promoter designated type T1A-2. In addition, the CO2 uptake increased as ∆P increased or ∆T decreased. Moreover, mesoporous silica (silica gel) performed better than microporous silica (zeolite 13X) where the formation of hydrate by zeolite 13X was observed with minimal CO2 uptake (0.58 mmol of CO2 per g of H2O) when the bed height was reduced. Additionally, the total amount of CO2 consumed through hydrate formation increased as the amount of water inside mesoporous silica increased which was not the case for microporous silica. Furthermore, the experiments performed in the IGCC conditions (283 K and 70 bar) by employing T1-5 and T3-2 in a fuel gas mixture demonstrated low hydrate formation with a CO2 uptake of 1.5 and 1.1 mmol of CO2 per g of H2O respectively. This was expected due to the slow kinetics since CO2 molecules were competing with H2 molecules which also reduced the selectivity of CO2 molecules during hydrate formation. Hence, in reality, pure CO2 system is the best option for CCS through hydrate formation at the right operating conditions as compared to fuel gas mixture.

Metal pollutants such as copper released into the aqueous environment have been increasing as a result of anthropogenic activities, a topic causing global concern. Adsorption-based treatment technologies offer opportunities to remediate metal pollutants from municipal and industrial wastewater effluent. The aim of this work was to evaluate the capability of modified cellulose nanowhisker (CNW) adsorbents for the remediation of copper from water matrices under realistic conditions using response surface methodology (RSM) and artificial neural network (ANN) models. The first part of the study explored the preparation and characterisation of modified CNW adsorbents. It also focused on the stability of the modified CNW adsorbents at different time intervals under dry conditions (up to 28 days) and in the water matrix (up to 7 days). The results showed that the modified CNW adsorbents were stable at different time intervals under dry conditions and in the water matrix and proved that the functional groups were permanent and did not degrade under the tested conditions. The stability of these modified CNW adsorbents under these conditions, which is relevant from both the manufacturing and application perspectives, is reported for the first time in this study. The second part of the work focused on using copper as a case study for heavy metal pollution in a clean water matrix, to evaluate removal by modified CNWs under several conditions and ranges appropriate to wastewater treatment plants (WWTPs), using factorial experimental design. RSM and ANN models were employed in order to optimise the system and to create a predictive model to evaluate the Cu(II) removal performance by the modified CNW adsorbents. Moreover, unseen experiments not belonging to the training data set, located both inside and outside the test parameter system, were performed to test the model suitability. This is also novel, as generally only one or two parameter variations have been tested, without checking the chosen model suitability for parameters lying between the tested parameters, and certainly not for parameters lying outside the tested parameter space, as has been done in this study. The results obtained showed that the ANN model outperformed the RSM model when predicting copper removal from a clean water matrix. The Langmuir andFreundlich isotherm models were applied to the equilibrium data, and the results revealed that the Langmuir isotherm (R2 = 0.9998) had better correlation than the Freundlich isotherm (R2 = 0.9461). Experimental data was also tested in terms of kinetics studies using pseudo-first order and pseudo-second order kinetic models. The results showed that the pseudo-second-order model accurately described the kinetics of adsorption. The third part of the work was aimed at gaining a deeper understanding of the complexity and variability of the wastewater matrix, including evaluating the impact of the wastewater matrix temporally on adsorbent performance to remediate copper pollutant from a real-world wastewater matrix. This study has demonstrated that the wastewater matrix composition, which is both complex and variable, has an impact on adsorbent capability and performance. A benchmark study was adopted as a ‘new’ water quality parameter to inform on the effects of the wastewater matrix (wastewater composition and its variability) on the modified CNW adsorbent’s capability to remediate copper from this matrix. Since the process of adsorption from wastewater is often complicated due to the variation in wastewater composition, results obtained from the benchmark experiments were included as one of the independent variables in ANN modelling, unlike in other optimisation studies. The performance of the ANN and RSM models was statistically evaluated in terms of coefficient of determination (R2), absolute average deviation (AAD), and root mean squared error (RMSE) on predicted experimental outcomes. The ANN model including the variability of wastewater composition fitted the experimental data with excellent accuracy and better prediction (R2 = 0.9963) than both the ANN model that did not include this variability (R2 = 0.9945), and the RSM model (R2 = 0.9409). The outcome of this study showed that by supplying the ANN model with the data obtained from the benchmark experiments as the fourth independent variable, it was possible to improve the predictability of the ANN model. Continuous flow experiments for remediation of spiked Cu(II) from the wastewater matrix were conducted. However, the physical structure of modified CNW adsorbents renders them unsuitable for use in column operation. Therefore, a more detailed study of the mechanical properties of CNW adsorbents would be necessary in order to improve the strength and stability of the adsorbents. This work has demonstrated that modified CNW are promising adsorbents to remediate copper from water matrices under realistic conditions including wastewater complexity and variability. The use of models to predict the test parameter system and account for matrix variability when evaluating CNW adsorbents for remediating Cu from a real-world wastewater matrix may also provide the foundation for assessing other treatment technologies in the future.

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Inorganic colloids are considered as potential transporters of toxic metals in the geosphere. If inorganic colloids are stable and able to adsorb toxic metals they may enhance their apparent solubility. If these colloids are mobile in the aquatic environment they may also enhance the transport of toxic metals. It is therefore of considerable interest to determine the characteristics of inorganic colloids in relation to toxic metal transport.

No description available.

There is a public concern over the potential accumulation of heavy metals in soils. Numerous studies have already demonstrated that areas in close proximity to vehicular traffic are marked noticeably by contamination of soil, air and water. Hence, such activities can affect humans and other living organisms. The aim of this study is to investigate the pollution of soils caused by vehicular traffic, on agricultural land in Azzawiyah, Liby with the view of assessing potential application of phytoremediation options for the remediation of contaminated soils and determine whether soil amendments would improve soil remediation. In an effort to improve the status of pollution of soils by vehicular traffic, a phytoremediation method of remediation of contaminated land has been used in this study, as it is relatively inexpensive and has the potential through the appropriate selection of plant species to be effective. This method is a soil clean up technology that uses the ability of metal accumulator plants to extract metal from contaminated soil with their roots and to concentrate these metals in above-ground plant parts. In this study, the investigation area was in Azzawiyah city where the soil samples and Doedonea viscose plant were collected from the road side. These soil samples were analysed using different experiments to determine physical and chemical properties, such as pH, OM and CEC. Heavy metals in soil and Doedonea viscose shoot and root were analysed using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The findings of the study show that all soils samples collected along the highway road connecting Azzawiyah with the southern parts of Libya were found to be granular with a sandy texture. It is also found that the metal content in soil collected from the site, which is close to the roadside was relatively higher than that soil collected from the agricultural field in the same area. Furthermore, the level of Pb (840mg/kg-1) in roadside soils was higher than the natural levels of Pb in soils. In addition, Doedonea viscose plant was not a hyperaccumulor plant. Greenhouse experiments used three plants (E. camaldeulensis, Brassica Juncea and Medicago sativum) to uptake heavy metal, such as Cd, Zn and Pb from the soil samples. The greenhouse experiment results indicate that E. camaldeulensis was the best plant species for phytoremediation of Pb contaminated soils than the other two plants species (Brassica Juncea, Medicago sativum). The efficiency of the E. camaldeulensis was increased by adding amendments (e.g. compost, compost, EDTA, Hoagland solution and Alcaligenes eutrophus) to the plants pots in order to uptake the lead form soil samples. The results of the pots amendments experiments indicate that 15 mmol of EDTA and bacterial inoculums (Alcaligenes eutrophus) were the best amendments to extract lead from the soils. The study suggests that using the Alcaligenes eutrophus with the E. camaldeulensis are more suitable for phytoremediation in terms of accumulation and cost.

No description available.

The increase in global carbon dioxide emission has raised concerns about climate change. This has caused nations to consider different carbon dioxide mitigation pathways to reduce emissions. The iron and steel industry contributes to approximately 30% of total global CO2 direct emission in the industrial sector. It is an energy intense industry. Many steel mills are operating close to thermodynamic limits in efficiency. Therefore decarbonising the steel industry through process improvements is limited. Breakthrough technologies such as carbon capture and storage (CCS) is an alternative and attractive solution. In this research I have explored the application of a retrofit carbon capture technology to an existing steel mill. The steel mill chosen, combusts gases arising from the steel making processes. Different locations within the steel mill were analysed, the in-house power station and the turbo blower house were chosen for retrofit post-combustion carbon capture. Two different separation technologies were process modelled to capture the carbon dioxide from the flue gas of the in-house power station and the turbo blower house. The technologies were chemical absorption and adsorption. The two technologies were techno-economically studied. Chemical absorption, with solvent MEA, showed capability of recovering 86% of CO2 with a purity of more than 99 mol%. Adsorption using sorbent zeolite 13X was able to achieve 82% recovery with purity of 96 mol%. Sorbent activated carbon showed a capability of recovering 67% of carbon dioxide with a purity of 95 mol%. The cost of CO2 avoidance for the process using chemical absorption (MEA) was equal to $44.92/tonne CO2. For the process using adsorption (zeolite 13X) the CO2 avoided cost was equal to $44.90/tonne of CO2. Activated carbon was the most expensive capture process, out of the three processes studied. It costs $45.81/tonne of CO2 avoidance.