Mineral Separation with Biological Macromolecules

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Previous work has demonstrated that peptides of 7 to 12 amino acids selectively bind to minerals of economic interest such as chalcopyrite, enargite, and sphalerite. It was suggested that this could be the basis of a selective mineral separation scheme. More recent work has shown that magnetic nanoparticles functionalized with mineral binding peptides, effectively a magnetic collector, could be used to separate ultra-fine (<38 microns) mineral particles of interest from a synthetic mixture of mineral particles using a magnet once the functionalized nanoparticles were added to the mixture. Separation of chalcopyrite from quartz in mixtures of ultra-fine particles was achieved with 80% recovery and separation of chalcopyrite from enargite was achieved with 65% recovery. A better understanding of the peptide binding mechanism to minerals is needed. Spectroscopic imaging techniques will be applied to characterize the peptide-mineral binding, particularly to determine the role of polar amino acids which, based on alanine scans of the binding peptides, are necessary for binding. Using peptide-functionalized magnetic nanoparticles a SQUID magnetometer will be used to measure the magnetic response of the coated mineral particles to enable the correct determination of the nanoparticle dose.A second objective is to scale up the magnetic separation process. At industrial scale the use of peptides to recover small mineral particles will require that the interaction between the peptides and the mineral particles be confined to a small volume such as a small diameter tube, a form of process intensification. A manifold of small diameter Teflon tubes for mixing slurry with magnetic collectors may provide an inexpensive scalable alternative. Thirdly, since custom peptide manufacture is expensive, an alternative is needed in order for the use of magnetic collectors in mineral separation to be economically viable. Recent work by others has shown that it may be possible to genetically engineer simple bacteria such as E coli, to both synthesize magnetite within their intracellular structures and to enable them to display mineral binding peptides on their outer membranes, thus providing a natural magnetic collector simply by growing the genetically engineered bacteria. Similar genetic engineering can also be done with yeast. These possibilities will be investigated. This program will advance the state of the art of mineral separation and provide several alternatives for better recovery and separation of desired minerals. Also there are many opportunities for HQP training in genetic engineering, micro-reactor design, and technology implementation in the mining industry.