Fine coal recovery utilizing landfill-derived liquids
- Authors: Hall, Stephen
- Date: 2002
- Type: Text , Journal article
- Relation: International Journal of Surface Mining, Reclamation and Environment Vol. 16, no. 1 (2002), p. 40-47
- Full Text: false
- Reviewed:
- Description: Liquid effluents that arise in the landfilling of municipal solid wastes, both leachate and gas condensates, can replace some or all of the conventional coal flotation reagents. The waste management industry currently must treat these effluents, to destroy contained organics, prior to their discharge to the environment and hence they are available at no cost, or even with "dollars attached". These landfill-derived liquids contain valuable short-chain fatty acids (e.g. valeric and caproic acids) that act as both frother and collector in flotation processes. They can be further concentrated by membrane filtration to reduce the transport costs of such liquids and the ease of their use in coal recovery systems. This paper will discuss how these liquids are formed in landfills, their typical compositions and how they can be employed to recover fine coal. Data from both conventional flotation feeds (-0.5 mm) and column flotation feeds (-0.1 mm) is presented.
- Description: 2003000130
Effects of electrokinetic treatments on the properties of a salt affected soil
- Authors: Jayasekera, Samudra , Mewett, John , Hall, Stephen
- Date: 2004
- Type: Text , Journal article
- Relation: Australian Geomechanics Vol. 39, no. 4 (2004), p. 33-46
- Full Text:
- Reviewed:
- Description: This paper presents experimental results of a study undertaken to investigate the effects of electrokinetic treatments on selected chemical and physical properties of a salt contaminated (saline) soil. The study was conducted as a laboratory scale pilot project using locally available saline soil samples. The soil was subjected to an electric gradient by passing a direct current between inserted electrodes. After certain electrokinetic treatment periods, the properties of the soil were evaluated. The experimental data reveals that electrokinetic techniques could offer a low cost. rapid solution to treat saline soils. The removal efficiency of sodium ions was found to be greater than 90% within a relatively short time period of 14 to 30 days, using low current and voltage systems. After 14 to 30 days, the degree of salinity and sodicity decreased to a very low or negligible level. The unconfined compression strength of the soil increased by between 30 % to 100% in 30 days of electrokinetic treatment indicating the improvements in the physical properties, especially in the stress-strain characteristics of the soil. The liquid limit (LL) and plastic limit (PL) increased at the cathode.
- Description: C1
- Description: 2003000726
Modification of the properties of salt affected soils using electrochemical treatments
- Authors: Jayasekera, Samudra , Hall, Stephen
- Date: 2007
- Type: Text , Journal article
- Relation: Geotechnical and Geological Engineering Vol. 25, no. 1 (2007), p. 1-10
- Full Text:
- Reviewed:
- Description: In this project, an in situ soil treatment technique using the principles of electrokinetics was tested using laboratory experimental models in order to identify the potential of this approach in modifying and reinstating the physical properties of salt affected soils. Experiments were conducted in the laboratory using saline-sodic soils collected from two salt affected regions in central Victoria, Australia. Soil specimens were compacted in glass tanks to reproduce in situ density and in situ water content. Using mild steel electrodes inserted into the soil, a direct current was passed through the soil under a constant potential gradient of 0.5 V/cm for a period of 14 days. In separate experiments, distilled water and a saturated lime solution were introduced to the soil via the anode over this experimental period. It was observed that the soil dispersion, otherwise known as soil sodicity (measured as ESP - Exchangeable Sodium Percentage and SAR - Sodium Absorption Ratio) decreased by up to 90% in most regions of the soil between the electrodes. The compressive strength of the soil increased in excess of 100% with electrokinetic treatment alone while the lime-enhanced electrokinetic treatment led to an almost 200% strength increase. The liquid limit and plastic limit of the soil increased causing the plasticity index to decrease, indicating increases in soil compressive strength and workability. These results indicate the potential of this technique for improving the physical properties of salt affected soils both effectively and efficiently, and in particular gives hope for the remediation of salt affected land for infrastructure management and development. © Springer Science+Business Media, Inc. 2006.
- Description: C1
- Description: 2003004772
The use of low-toxic heavy suspensions in mineral sands evaluation and zircon fractionation
- Authors: Koroznikova, Larissa , Klutke, Cameron , McKnight, Stafford , Hall, Stephen
- Date: 2008
- Type: Text , Journal article
- Relation: Journal of The South African Institute of Mining and Metallurgy Vol. 108, no. 1 (2008), p. 25-33
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- Reviewed:
- Description: This paper outlines a simple methodology for mineral characterization, developed as part of the Australian Mineral Industry Research Association (AMIRA) managed research project P777 'The Development of Heavy Suspension Techniques for High Density Separations (Replacement of Clerici's Solution)'. The project was sponsored by De Beers, Rio Tinto and Iluka Resources. Heavy mineral characterization of samples arising from exploration, mining or metallurgical processes is frequently conducted using laboratory heavy liquid analysis. Unfortunately, there are only a limited number of high density ('heavy') liquids and these tend to be more toxic as their density increases. Low-toxicity inorganic solutions, based on tungsten compounds, have been developed that can be utilized at relative densities (RD) up to 3.0. Beyond this value organic liquids can be used; however, this presents significant health and safety hazards. Diiodomethane (methylene iodide) having a relative density of 3.31 is commonly used. Mixtures of thallium formate and thallium malonate were found in the early 1900s by Clerici to provide liquids having specific gravities between 4.0 and 5.0. For the characterization of the heavy components of mineral sand deposits (e.g. anatase RD 3.9, rutile RD 4.2, ilmenite RD 4.4-4.7 and zircon RD 4.6-4.8) there is currently no heavy liquid alternative to Clerici's solution. Clerici's solution is highly toxic and testing is now conducted by few laboratories worldwide, with costs reflecting the chemical costs, infrastructure costs and health and safety regimes (e.g. blood testing of exposed staff). A simple laboratory technique of density fractionation has been developed, employing suspensions of fine tungsten carbide particles in lithium heteropolytungstates solutions, that can replace Clerici's solution in the evaluation of fine mineral sands samples (e.g. -250 +150 microns). The developing methodology that can achieve low-cost, low-toxic separations at relative densities above 4.0 is outlined and the comparison of results with Clerici's solution presented. In addition, preliminary work on density fractionation of zircon samples is presented. Zircon fractionation relates to their inclusion, radionuclide content and metamictization. © The Southern African Institute of Mining and Metallurgy, 2008.
- Description: C1