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The separation of copper sulfide ore minerals from gangue using magnetic nanoparticles functionalized with peptides selected via phage display : a proof of concept Greene, Robert Crandall

Abstract

Copper is one of the most important mineral resources. While much unmined copper remains to meet increasing demands, reserve deposit concentrations are dropping while increasing in mineralogical complexity. Porphyry deposits containing the largest reserves have an average grade of 0.25% and often contain elevated concentrations of arsenic in comparison to the deposits that supplied most copper before the 20th century. The current copper porphyry processing scheme first concentrates sulfide ores via froth flotation, then smelts these concentrates. These processes are energy intensive and employ toxic chemical reagents. Low grade deposits must be extensively milled to release ore from gangue. Copper sulfide grains milled to 2000 ppm cannot be smelted without releasing gaseous arsenic compounds. Common flotation reagents cannot distinguish between arsenic-bearing enargite (Cu₃AsS₄) and chalcopyrite (CuFeS₂). Biotechnology, however, offers a solution to these problems with peptides. Peptides displayed on bacteriophage can be selected for their binding affinity to a specific mineral phase. In this thesis, peptides that bind to chalcopyrite and not to silicate gangue were attached to iron oxide nanoparticles coated with aminopropyl silane via a polyethylene glycol cross-linker. Attachment of the peptides to the nanoparticles was confirmed with FTIR and UV-vis spectroscopy. The nanoparticles were then used to coat and magnetically concentrate chalcopyrite. The nanoparticles preferentially concentrated

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