Abstract--The rapid phase quantification method using X-ray diffraction (XRD) with a position-sensitive detector (PSD), outlined by Cressey and Schofield (1996), has been extended to facilitate mineral phase quantification of clay-beating samples. In addition, correction factors for differences in matrix absorption effects have been calculated and applied. The method now enables mudrock mineralogy to be quantified rapidly and efficiently. Using this approach overcomes many of the problems hitherto associated with the quantitative analysis of clay minerals, in particular the effects of preferred orientation of crystallites and variable sample-area irradiation, that make the task of quantification extremely difficult by conventional Bragg-Brentano scanning diffractometry.
The paper discusses the mineralogical and chemical stability of the Oxford Clay as a landfill liner for the containment of domestic waste. The results from a series of batch equilibrium experiments with the mudrock and a synthetic leachate are compared with samples of a liner cored from a 15‐year‐old site in the Formation. The effects of leachate on the Clay include mineral dissolution, exchange of cations, particle‐size reduction and collapse of illite‐smectite. In situ mixed‐assemblage mineral liners, such as the Oxford Clay, are capable of attenuating leachate components and buffering acid leachates whilst the predominant clay minerals, i.e. illite and kaolinite, remain stable. Alterations to the mineralogy and chemistry of the samples resulting from both short‐term and long‐term exposure to leachate are discussed with reference to the implications to landfill practice.
The mineralogical and chemical integrity of mineral liners for domestic waste landfill sites was investigated using a series of batch reactor experiments. A synthetic acetogenic leachate was developed based on the composition of domestic waste leachates. The interactions between the synthetic leachate and mudrocks used by Shanks and McEwan Ltd. to line landfill sites located in the United Kingdom are described. The results of the laboratory experiments are contrasted against those obtained from samples of a 15-year-old mineral liner from a landfill site located near Stewartby, Bedfordshire. The interactions between a concentrated, ionic solution, such as a leachate, and mineral liners include ion-exchange, particle size reduction, mineral dissolution and clay-mineral disordering and collapse. Bentonites and high-swelling clays are more susceptible to mineral transformations than mixed assemblage mudrocks and low-swelling clays. Understanding the interactions between leachate and mudrocks will assist the prediction of the long term performance and integrity of natural lining materials.
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