• Hodgkinson, Jane H.
• Mcnally, Clint

Abstract

echnical Section: Recovery of rare earth metals and deriving value from waste) Coal production and export are important to the Australian economy. The economic benefits of coal production in Australia however, come with a number of sustainability challenges. One of the key sustainability challenges is the generation of large amounts of waste and the associated environmental issues. Solid waste is generated in every part of the coal production value chain, most of which is placed in engineered storage facilities. Sampling and characterisation of some Australian coals and waste have shown promising elevated concentrations of rare earth elements (REE) with the potential for economic extraction. This represents a significant opportunity to derive additional value from coal production and utilisation.CSIRO has developed a multilayered framework from which optimal mine waste utilisation pathways may be determined, based on the characteristics of tailings and other wastes. This involves tailings and waste characterisation, reprocessing where indicated and repurposing and reuse of the remaining waste for a step change in sustainability of coal production. In this paper, we discuss a couple of approaches to capture value from coal mining waste while reducing the safety and environmental risks associated with tailings and waste storage facilities. One aspect of the study involved the determination of the mineral associations of REE in coal-based resources and using this knowledge in the development of innovative beneficiation and extraction technologies for these high-value metals as co-product or by-product of coal production in an environmentally acceptable manner. The second aspect of the study involved the use of the washery waste in producing geopolymer concrete products for construction purposes. This part of the study examined the use of coal mine tailings as source material in alkali activated binder for geopolymer concrete production. It also studied the suitability of coal preparation coarse and fine rejects as substitutes for aggregates and sand respectively in geopolymer concrete production. The work involved the formulation and testing of geopolymer mixes for their setting behaviour, workability and compressive strength development. These geopolymer properties were assessed using equivalent ordinary Portland cement concrete as a benchmark.It was determined that coal mine tailings with appropriate pre-treatment is a suitable precursor material for geopolymer binder formulations in terms of workability and strength development when using a mixture of concentrated sodium hydroxide solution and sodium silicate solution as the alkali activator. The optimised 7-day compressive strengths of the geopolymer binder and concrete produced by alkali activation of coal mine tailings were comparable to N32 ordinary Portland cement (OPC).

Topics

• impedance spectroscopy
• mineral
• extraction
• strength
• Sodium
• cement
• activation
• rare earth metal