W. Scott Dunbar

The volume integral method of eddy current modeling

The volume integral method is proposed as an alternative method for computing the impedance changes associated with eddy current measurements. In this method, the use of an appropriate Greens function for the host medium requires that integration be performed only over the volumes of defects. Although only rather simple host medium geometries are amenable to this type of modeling, the method can be linked to finite element models of more complicated geometries. In this way, the amount of finite element modeling may be minimized.

Biomining with bacteriophage: Selectivity of displayed peptides for naturally occurring sphalerite and chalcopyrite

During mineral processing, concentrates of sulfide minerals of economic interest are formed by froth flotation of fine ore particles. The method works well but recovery and selectivity can be poor for ores with complex mineralogy. There is considerable interest in methods that improve the selectivity of this process while avoiding the high costs of using flotation chemicals. Here we show the first application of phage biotechnology to the processing of economically important minerals in ore slurries. A random heptapeptide library was screened for peptide sequences that bind selectively to the minerals sphalerite (ZnS) and chalcopyrite (CuFeS2). After several rounds of enrichment, cloned phage containing the surface peptide loops KPLLMGS and QPKGPKQ bound specifically to sphalerite. Phage containing the peptide loop TPTTYKV bound to both sphalerite and chalcopyrite. By using an enzyme-linked immunosorbant assay (ELISA), the phage was characterized as strong binders compared to wild-type phage. Specificity of binding was confirmed by immunochemical visualization of phage bound to mineral particles but not to silica (a waste mineral) or pyrite. The current study focused primarily on the isolation of ZnS-specific phage that could be utilized in the separation of sphalerite from silica. At mining sites where sphalerite and chalcopyrite are not found together in natural ores, the separation of sphalerite from silica would be an appropriate enrichment step. At mining sites where sphalerite and chalcopyrite do occur together, more specific phage would be required. This bacteriophage has the potential to be used in a more selective method of mineral separation and to be the basis for advanced methods of mineral processing.

Biotechnology and the Mine of Tomorrow

Biotechnology could provide many innovative alternatives for changing the way metals are obtained. Microbes have been used to dissolve metallic minerals and release metal ions into solution, from which pure metal can be obtained by electrolysis. Plants that accumulate metals in their roots and leaves have been used to concentrate metals, and mineral-binding peptides might be used to separate minerals. However, for billions of years microbes have been interacting with metals. Microbial communities in and near mineral sources are therefore a rich source of genetic information which could be used to create synthetic or modified microbiomes that concentrate metals. This would be a complete paradigm-change with enormous scope for transforming the way metals are obtained.

MINING WASTE: TRANSFORMING MINING SYSTEMS FOR WASTE MANAGEMENT

Mining environmental management primarily focuses on concerns over the impact of waste disposal on the surface, in the form of tailings and waste rock. Traditionally waste products have only been returned to the mining void in limited quantities and surface disposal technologies have been paramount. Mining systems need to be reengineered, based on a new paradigm that mining is a business whose success is fundamentally dependent upon waste management. Strategies are available to shift this paradigm and to minimize the surface impact of waste disposal. Firstly, mining methods need to be developed that are more selective. A more futuristic strategy may be the implementation of solution mining. Pre-concentration and even the full integration of mineral processing within the mine workings could be important in this strategy in the interim. Secondly, technologies enabling the return of waste securely to the void should be pursued. This paper considers the design of new mining methods that minimize waste output. It then reviews technologies for in situ pre-concentration. Finally it addresses the issues associated with the return of waste to mined voids.

Effects of bacteriophage on the surface properties of chalcopyrite (CuFeS2), and phage‐induced flocculation of chalcopyrite, glacial till, and oil sands tailings

The binding of mineral‐specific phage to the surface of chalcopyrite (CuFeS2) was investigated by using X‐ray photoelectron spectroscopy and scanning Auger microscopy. These studies confirmed the elemental composition of the minerals and confirmed that bacteriophage were bound to the mineral surface. These techniques also revealed that the phage were not forming a continuous film over the entire surface of the CuFeS2 particles, but selectively bound to the slimes coating the particles. In addition, the effect of mineral‐specific phage binding to the surface of CuFeS2 was investigated using induction time and zeta potential measurements. Bacteriophage (1012/mL) increased the induction time (contact time resulting in 50% particle attachment to a bubble) from ∼7.5 to ∼17 ms and reversed the zeta potential from negative to positive. In the course of performing the zeta potential measurements on particles <45 µm in diameter, phage‐induced aggregation was observed. The mechanism of aggregation was explored using a range of pH (3–11) and cation concentrations. Aggregation was observed across the tested pH range and with all cations. Phage also mediated aggregation of glacial till and oil sands tailings in a dose‐dependent and particle size‐dependent manner. We conclude that binding of bacteriophage to the surface of CuFeS2 does alter its surface properties. Biotechnol. Bioeng. 2011; 108:1579–1590.

Identification of lanthanum-specific peptides for future recycling of rare earth elements from compact fluorescent lamps.

As components of electronic scrap, rare earth minerals are an interesting but little used source of raw materials that are highly important for the recycling industry. Currently, there exists no cost‐efficient technology to separate rare earth minerals from an electronic scrap mixture. In this study, phage surface display has been used as a key method to develop peptides with high specificity for particular inorganic targets in electronic scrap. Lanthanum phosphate doped with cerium and terbium as part of the fluorescent phosphors of spent compact fluorescent lamps (CFL) was used as a target material of economic interest to test the suitability of the phage display method to the separation of rare earth minerals. One random pVIII phage library was screened for peptide sequences that bind specifically to the fluorescent phosphor LaPO4:Ce3+,Tb3+ (LAP). The library contained at least 100 binding pVIII peptides per phage particle with a diversity of 1 × 109 different phage per library. After three rounds of enrichment, a phage clone containing the surface peptide loop RCQYPLCS was found to bind specifically to LAP. Specificity and affinity of the identified phage bound peptide was confirmed by using binding and competition assays, immunofluorescence assays, and zeta potential measurements. Binding and immunofluorescence assays identified the peptides affinity for the fluorescent phosphor components CAT (CeMgAl11O19:Tb3+) and BAM (BaMgAl10O17:Eu2+). No affinity was found for other fluorescent phosphor components such as YOX (Y2O3:Eu3+). The binding specificity of the RCQYPLCS peptide loop was improved 3–51‐fold by using alanine scanning mutagenesis. The identification of peptides with high specificity and affinity for special components in the fluorescent phosphor in CFLs provides a potentially new strategic approach to rare earth recycling. Biotechnol. Bioeng. 2017;114: 1016–1024.

Analysis of flexible mining systems

Flexible mining systems possess the ability to adapt to internal or external changes in operating conditions and maintain production expectations. This paper reviews the nature of the various types of mining flexibility and their controlling factors. Methods for assigning a value or figure of merit to flexibility are presented. Examples focus on the use of these methods at the mine level. Option pricing was found to be a useful approach for valuation of flexibility in a strategic, long-term context such as in mine design or major modification of mine operations. Computer simulation was found to be useful for tactical evaluation of flexible opportunities in mine production control.

Identification of mineral-binding peptides that discriminate between chalcopyrite and enargite

Innovative approaches to the separation of minerals and subsequent extraction of metals are imperative owing to the increasing mineralogical complexity of ore deposits that are difficult or even impossible to separate into slurries or solutions containing only the minerals or metals of interest. Low recovery of metal is typical for these complex deposits leading to significant losses to tailings. In addition, the minerals often contain impurities, some toxic, which are difficult and costly to control or manage during the processing of a concentrate or other mineral product. One example of this complex situation is the significant economic and environmental costs associated with diluting and processing copper concentrates containing arsenic (in the form of the mineral enargite, Cu3AsS4) in the production of pure copper. To overcome these separation problems, we have utilized phage display to identify peptides that demonstrate selective recognition of enargite and the arsenic‐free copper sulfide, chalcopyrite. Screening of two random peptide phage display libraries resulted in the identification of an enargite‐selective peptide with the sequence MHKPTVHIKGPT and a chalcopyrite‐selective peptide with the sequence RKKKCKGNCCYTPQ. Mineral‐binding selectivity was demonstrated by binding studies, zeta potential determination and immunochemistry. Peptides that have the ability to discriminate between enargite and chalcopyrite provide a greener option for the separation of arsenic containing contaminants from copper concentrates. This represents the first step towards a major advance in the replacement or reduction of toxic collectors as well as reducing the level of arsenic‐bearing minerals in the early stages of mineral processing. Biotechnol. Bioeng. 2017;114: 998–1005.

Bacteriophage-induced aggregation of oil sands tailings.

Very large quantities of tailings are produced as a result of processing oil sands. After the sand particles settle out, a dense stable mixture of clay, silt, water with residual bitumen, salts, and organics called mature fine tailings (MFT) can remain in suspension for decades. Research into developing methods that would allow consolidation and sedimentation of the suspended particles is ongoing. We have studied the ability of a filamentous bacteriophage (called VP12 bearing the peptide DSQKTNPS at the N‐terminus of the major coat protein pVIII) to aggregate MFT. To understand the biophysical basis of the aggregation, phage‐induced aggregation of diluted MFT was measured at room temperature under varying conditions of pH, salt, detergent. Phage at concentrations of 5.0 × 1011/mL to 1012/mL induced rapid settling of the diluted MFT. The addition of sodium chloride (10 mM) lowered the concentration of phage required to induce aggregation. Since the non‐ionic detergents Triton‐X 100 and Tween‐20, and the ionic detergent sodium deoxycholate had little effect, hydrophobic interactions do not appear to be a major contributor to the phage‐induced aggregation of MFT. However, aggregation was prevented at pH values higher than 9.0 suggesting that positively charged amino acid residues are required for MFT aggregation by phage. Genetic engineering of the pVIII peptide sequence indicated that hydrogen bonding also contributes to phage‐induced aggregation. In addition, replacing the basic residue lysine with an alanine in the recombinant peptide of VP12 completely prevented phage‐induced aggregation. Three other phage displaying different amino acid sequences but all containing a lysine in the same position had variable aggregation efficiencies, ranging from no aggregation to rapid aggregation. We conclude that not only are the functional groups of the amino acids important, but the conformation that is adopted by the variable pVIII peptide is also important for phage‐induced MFT aggregation. Biotechnol. Bioeng. 2013; 110: 803–811.

A comparison between Offset Herringbone and El Teniente underground cave mining extraction layouts using a discrete event simulation technique

Several underground cave mining operations have realised benefits in development rates when an extraction level layout is designed according to the El Teniente style. Geotechnical benefits may accrue in adopting the advance undercut technique in which extraction drift development lags the undercut development directly above. However, few technical studies are available in the literature that directly compare the Offset Herringbone and El Teniente styles when the decision criteria focus is on development rate impacts. This paper reports on research into discrete event simulation (DES) modelling that emulates stochastically the process of building the interdependent lateral infrastructure levels within the footprint of an existing cave mining method that uses the advance undercut technique. Such DES models can capture design considerations: firstly in the early stages of development, in which a limited number of headings are available; and secondly in the full stages of development where the maximum number of headings are governed by the width of the ore body. DES modelling is discussed in this paper in a case study situation, where results indicated that an additional 3% of drawpoint drivage required in an El Teniente layout could increase development rates by an average of 9%.