Chemical and mineralogical aspects of soil formation in bauxite residue

Talitha Santini

    Research output: ThesisDoctoral Thesis

    918 Downloads (Pure)

    Abstract

    [Truncated] Bauxite residue mud (BRM; also known as ‘red mud’) is an alkaline, sodic-saline byproduct of the Bayer process in which alumina is extracted from its ore, bauxite. Rehabilitation of BRM storage areas usually involves deposition of a capping layer over the mud (consisting of imported soil combined with fertilisers and other amendments, and can include an impermeable synthetic membrane separating the capping layer from the deposit) followed by establishment of vegetation in the capping layer (the ‘cap and store’ approach). The alumina industry is now moving towards in situ remediation approaches to residue management, which involve amendment of the BRM with applied treatments, and establishment of vegetation directly in the residue surface. Surface applications of various organic and inorganic amendments that increase the chemical and physical ability of the mud to support vegetation and other biota have been investigated previously; however, most of these studies are short term (≤5 years) and focus on immediate impacts of amendments on plant nutrition, and neglect to consider soil formation processes and how these will change the amended residue over time. Insofar as the objective of in situ remediation is to achieve a sustainable plant cover, pedogenesis (soil formation) is implicit in the modification of BRM properties.

    The aims of this project were to:

    1. Evaluate a weathering trajectory for BRM as determined by laboratory simulations;

    2. Review methods employed for the chemical analysis of bauxite residue, identifying potential flaws and suggesting modifications to methods where necessary to overcome these flaws, and;

    3. Investigate the response of bauxite residue to applied treatments and weathering (>20 years), and the effects of natural processes on modifying the residue towards a soil with targeted properties, under the influence of factors such as climate, initial residue properties, vegetation, topography and time.

    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2012

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