The aim of the current project is to determine if Zeolite-A is suitable for lead remediation in pyrite ash contaminated soils. Pyrite ash is the waste product formed by roasting sulphide-bearing minerals for the production of sulphuric acid. The main sulphide mineral in the original material is pyrite, FeS2. After roasting, the soils contain a large amount of iron oxide in the form of hematite (α-Fe2O3), as this is the main product in the roasting process of pyrite. It was found that concentrations of 23000 to 26000 ppm of lead were present in the pyrite ash layers. Zeolite-A was chosen as a method of remediation because it is a synthetic zeolite that is easy to synthesise, has a small pore size, and has a high affinity towards lead as shown by other studies on wastewater treatment. Zeolite-A was added to soil samples and washed with water and dilute nitric acid to simulate rain and acid rain conditions. It was found that the addition of Zeolite- A to all soil samples investigated resulted in a pH increase by over 2 pH units. In soils washed with acid, having a pH of around 0.30, the pH increased to about 3.00. In soils with a pH of around 4.50, the addition of Zeolite-A increased the pH to nearly 8.00. It was demonstrated that the addition of Zeolite-A to the samples resulted in a reduction of lead ions in all the leachates, independent of initial pH. The effect of Zeolite-A varied as a function of pH, but was found to reduce lead concentration in the leachate by approximately 82% to 99%. It was concluded to be successful for lead remediation. One explanation for the successful result of lead remediation by Zeolite-A was the formation of a natural zeolite, gismondine (CaAl2Si2O8⋅4H2O). It was found that gismondine was formed both when the soils were washed with water or with acid. Hence, the gismondine formation was independent of pH. It is also proposed by this study that Zeolite-A stimulated the crystalline formation of gismondine.

Post-combustion capture using amine-based solvents has been considered as the most viable technology for carbon capture, to mitigate industrial carbon dioxide (CO2) emissions; but the solvents show a number of shortcomings. Recently, ionic liquids (ILs) are suggested as possible alternative to amine-based solvents, for they can be molecularly engineered to match various target thermophysical properties. This work focused on the development of systematic approaches to design IL-based solvents for carbon capture purpose. The first focus of this work is to develop an insight-based based visual approach to determine potential IL solvents as substitute to conventional carbon capture solvents. This approach allows visualisation of high-dimensional problem to be visualised in two or three dimensions, and assist designers without mathematical programming background in IL design. Following that, a mathematical optimisation approach to design optimal IL solvent for CO2 capture purpose was developed as second focus of this thesis. This has been done by formulating the IL solvent design problem as mixed integer non-linear programming (MINLP) optimisation problem. The abovementioned approaches were developed to design task-specific ILs with high CO2 absorption capacity as substitute to common carbon capture solvents. However, studies show that such ILs are relatively more expensive and have higher viscosities. To reduce the cost and viscosity of solvent, task-specific IL can be mixed with conventional IL, ensuring CO2 solubility remains high, while viscosity and cost are acceptable. Hence, the previously developed visual approach was extended to design pure ILs and IL mixtures, specifically to capture CO2. In order to ensure the designed IL is performing at its optimum (highest CO2 solubility in this case), the operating conditions of the carbon capture process shall be considered because they will affect the thermophysical properties and CO2 solubility of ILs. Therefore, the forth focus of this work will be incorporation of operating temperature and pressure into design of IL solvents. Similarly, the design problem was formulated as MINLP problem and solved using mathematical optimisation approach, where operating temperature and pressure were defined as variables through disjunctive programming. Replacing solvent for carbon capture system to IL-based solvent or installing carbon capture system will affect the overall process, as this will affect the utilities consumption of carbon capture system. Therefore, process design has been integrated with IL design in this thesis, to study how the solvent substitution affects the entire process, and followed by retrofitting of the entire process including carbon capture system accordingly. The design problem was formulated and solved as MINLP problem. Finally, this thesis concludes with possible extensions and future works in this area of research work.

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No description available.

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Past and present techniques to remove toxic organic pollutants from industrial wastewaters have involved biological, oxidative and thermal treatment, but long biological degradation lifetimes and harmful emissions released via incineration type processes poses an environmental problem. Much of the new and emerging technologies have steered away from chemical treatment and progressed towards more sustainable and environmentally friendly processes. Wet air oxidation (WAO), being one of them, uses air as the oxidant mixed with the wastewater solution to oxidise the pollutants. This technology has evolved over the years to include catalysis (CWAO) which offers a greener and more cost effective form of industrial wastewater treatment. The majority of CWAO studies involve batch treatment in autoclave reactors, but this project’s aim was to make the treatment process continuous, using an active, stable heterogeneous catalyst in a trickle-flow reactor. Phenol was chosen as the model pollutant and the goal was to reduce its concentration from 1000 ppm to below the EPA limit under the least energyintensive conditions possible. The initial stages were made up of commissioning a reactor, followed by catalyst screening and optimisation, which included correlating activity with catalyst structure and composition. HPLC followed by UV detection was used to quantify phenol conversion, while a range of surface and bulk characterisation techniques were used to determine catalyst structure. Of the catalysts screened platinum supported by silicon carbide provided the most successful results in terms of conversion. SiC’s hydrophobic nature limits the wetting experienced during a CWAO reaction; a process that hinders oxygen activation. Doping with ceria improved the catalyst’s performance, allowing the metal loading to be reduced while maintaining high conversion of phenol. However when ruthenium was the active component, the more hydrophilic alumina was the preferred support. The reaction with ruthenium relies more on catalyst wetting as it is already in the oxide form. When tests were subsequently carried out on Pt/alumina catalysts, they confirmed the need to increase the hydrophobicity in order to achieve high activity. It is proposed that when the active sites are metallic, the optimum support surface is highly hydrophobic; whereas when metal oxide provides the active sites, the optimum support surface is hydrophilic. These findings explain how some of the catalytic components contribute towards CWAO’s reaction mechanism, and activity controlled, in a way not yet shown by previous publications.

Profiles of 241Am, 137Cs, 238Pu, 239240pu & 24lPu have been studied in four cores collected from the Ravenglass saltmarsh, Cumbria and one core collected from the Irish Sea, near the effluent pipeline of the Sellafield nuclear reprocessing plant. Major and trace elements have also been measured to look at the effects of sediment composition and any redox controls on element redistribution. In addition, almost one hundred surface scrape samples were collected from the Ravenglass saltmarsh and the same radionuclides were measured to study the lateral distribution of radionuclides. Three of the Ravenglass cores have well preserved the history of Sellafield discharge since the plant became operational in 1952. There are no significant post depositional processes and redox changes for all the cores studied. However, one of the saltmarsh cores collected from the front of the marsh shows that surface erosion has occurred. Surface scrape sample results also show that erosion is a significant process which results in the redistribution of sediments within the marsh. The core collected from the Irish Sea adjacent to the effluent pipeline shows sediment mixing has operated and these mixed sediments are the main source of material to the saltmarsh. Using the Sellafield discharge records from 1952 onwards, sediment mixing rates have been estimated using a simple mathematical model and they are inferred to be between 80 % and 90 %. Isotopic ratios of Pu isotopes have been compared to those estimated ratios corresponding to particular sediment mixing rates and show good agreement up to 30 cm below the surface. There is less correlation between Sellafield discharge ratios and measured ratios in cores below 30 cm and this may be due to unreliable discharge data or more likely the advective redistribution of material in the saltmarsh. A contribution of 241Am originating from the decay of 24IPu in cores was determined. The ingrown 241Am contributes significantly to the total 241Am measured. Based on the Sellafield discharge record, it is estimated that approximately 46 % of total 24IAm in the system has originated from the decay of 241Pu discharged from the plant since 1952. Spatial distribution of radionuclides in the Ravenglass saltmarsh is controlled by sediment accumulation associated with tidal inundation frequency and the clay content in the sediments. Surface erosion also plays a major role in redistributing saltmarsh sediment labelled with older Sellafield discharge within the marsh together with the sediments originated from the River Esk.

A range of tools have been proposed to support decision making in contaminated land remediation (collectively referred to as Decision Support Tools or DSTs). From a European perspective it is clear, however, that there are considerable national differences in the decision support process, and more generally in the extent to which this process supports the se lection of less invasive, alternative and potentially more sustainable remediation options such as phytoremediation, in situ immobilisation etc. (referred to here as "gentle" remediation technologies or options). This thesis critically reviews available DSTs in terms of their fitness for purpose for the application of "gentle" remediation technologies, using published literature and data from two stakeholder surveys: the first from a European perspective (completed in the European Union ERANET SNOWMAN project SUMATECS (Sustainable Management of Trace Element Contaminated Sites)) (sample size of 130) and the second focused on contaminated land consultants and managers in the UK (sample size of 71). In general stakeholder feedback from both surveys indicates a lack of knowledge of currently available DSTs and the requirement for a simple OST using a tiered approach that can be integrated into an existing national framework. Based on this stakeholder feedback, a novel OST has been developed that will interface with an existing national framework and which will act as a guide to selection of "gentle" remediation approaches. This DST is a literature based tool that will direct users to collated information on successful practical pilot/field scale studies on " gentle remediation approaches and ensures that the elements or sustainability are considered during selection. The proposed approach is validated against data from three large-scale remediation projects, involving both gentle and more invasive remediation methods, in the UK, France and Belgium.

This research project investigated the interaction between natural organics acids and selected metal ions. The aim of the project was to provide quantitative data on the speciation of metal ions when placed in systems containing natural organic acids. It was envisaged that such data will assist in the risk assessment of the Drigg low level waste site in Cumbria. The formation and complexing ability of these natural organic acids is discussed and the classing of these acids into high molecular weight organic acids and low molecular weight organic acids. Initial investigations used a potentiometric technique to study the interaction between nickel and europium and selected low molecular weight organic acids which were thought to occur in significant concentrations in soils and groundwaters. These experiments confirmed existing critically assessed literature values, and provided an experimental methodology for further 'in-house' measurement of such values. In addition, studies were also performed on systems containing two competing organic acids. Studies of such systems showed no synergistic effect and that they could be modelled using individual stability constants. A comprehensive investigation was performed on the interaction of nickel and europium with humic acid. High Performance Size Exclusion Chromatography (HPSEC) was assessed for its applicability to study such systems and was found to be suitable. Stability constants were determined for europium and nickel with humic acid. All data was modelled using MINTEQA2, a geochemical speciation code. Further work on these systems was carried out by a column ion exchange technique which confirmed the HPSEC data. A comparison was then carried out between batch and column exchange with the conclusion that column gave lower metal bound to the humic at high concentrations due to competition from the resin. HPSEC was used to investigate systems of low molecular weight organic acids with humic acids. In these systems no evidence for mixed complexes was found and that there was good agreement between experimental data and model predictions. The role of humic acid at alkaline pH was also investigated. It was found that humic acid showed enhanced complexation with europium and that this was attributable to phenolic groups on the humic molecule. In conclusion, results have been generated which provide data for a number of important reactions that occur in the environment.

There is great need for the widespread use of indoor gas monitors as modern hermetically-sealed domestic buildings increasingly suffer from indoor air pollution. However, neither modern technologies of gas sensors nor analytical instruments are ideally suited to this purpose. The problems of gas sensors are poor selectivity and the fact that normally they can detect only one gas, and analytical instruments suffer from their large size and high price. Therefore, the aim of the project is "to develop a novel gas sensor with low cost, low power consumption, high reliability, which can detect multiple gases with excellent selectivity" for indoor gas monitoring. In the first part of the project, an SOI-CMOS micro-hotplate with a single crystal silicon (SCS) resistive heater was proposed, fabricated and characterised. The design obviates issues of traditional heater materials i.e. platinum is not CMOS compatible and polysilicon is not thermally stable due to its polycrystalline structure. The SCS micro-hotplate was found to have an ultra low power consumption of 11.6 mW to operate at 500°C, and an excellent reliability with less than 1% drift after 500 hour operation at 500°C. In the second part, a novel temperature modulation technique for a carbon black/polymer composite sensor was theoretically derived based upon linear solvation and Fickian diffusion. The processing technique comprises only two steps; summing the off and on transient conductance signals from a temperature-stepped sensor, and subtracting the steady-state signal. The technique was demonstrated by applying to a carbon black/polyvinylpyrrolidone composite sensor employing the novel micro-hotplate. Identification of water. methanol and ethanol vapours was successfully demonstrated using the peak time of the resultant curve. Furthermore, quantification of those vapours was found to be possible using the height of the peaks, which was linearly proportional to the concentration. In conclusion, a novel low-cost gas sensor has been realised that is capable of detecting more than one gas with a single sensing element and thermal modulation. This has the potential for commercial exploitation in the area of indoor air pollution monitoring.