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Title: Theoretical study of the dissolution of copper from chalcopyrite
Author: Chen, Vincent Huair-Yu
ISNI:       0000 0004 6348 3855
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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A lot is unknown about the chemical mechanisms relevant to the dissolution of Cu from CuFeS2. This is a severe problem in the context of hydrometallurgical extraction, as it is currently not possible to obtain economical Cu yields from CuFeS2 mineral. In this work, periodic hybrid-exchange density functional calculations have been performed on CuFeS2 bulk and slabs representing various surface orientations. In the bulk study, geometric, electronic and magnetic properties of the ground state have been obtained and compared with experiment to validate the density functional methodol- ogy. In addition, the bonding properties of CuFeS2 have been studied, leading to the conclusion that CuFeS2 is semi-ionic. From the slab calculations, the surface energetics have been used to predict the surface morphology of CuFeS2, and hence the surface orientations likely to be exposed upon cleavage. In particular, the polar (112)/(-1-1-2) surface pair featured heavily in the predicted equilibrium crystallites due to its remarkably low surface energy. The stability of the surface pair was attributed to a combination of geometric and electronic stabilisation mechanisms. In the final part of this work, an attempt was made to develop a QM/MM embedded cluster methodology for the purpose of studying Cu dissolution mechanisms. The methodology was benchmarked against the periodic QM methodology employed in the study of CuFeS2 bulk and surfaces. The embedded cluster methodology was in general able to accurately reproduce the periodic QM electronic structure. However, the potential energy surfaces and optimised geometries predicted by the embedded cluster methodology differed significantly to those obtained from periodic slab calculations. The developed methodology was therefore deemed to be unsuitable for further study; this is likely due to the inability of the embedding charges to robustly model long range electrostatic interactions.
Supervisor: Hunt, Patricia A. ; Harrison, Nicholas M. ; Haynes, Peter Sponsor: Engineering and Physical Sciences Research Council ; Rio Tinto PLC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral