My research has focused on two key areas. The first is fixed-bed leaching (the subject of my Ph.D. dissertation), including heap leaching of copper and gold ores, and microbial heap and dump leaching of copper sulfides and of copper concentrates supported on inert substrates (the GeoCoat ä process). The bulk of my refereed journal publications are in this area. Specific accomplishments in this area include mathematical models for heap leaching processes, (including the HeapSim simulation package, currently in use at several major mining firms), a mathematical model for rinsing reagents from spent heaps, advances in the hydrology of heap leaching, and a novel enthalpy balance model for sulfide heap leaching which has led to advances in the design and control of heaps which support extremely thermophilic microbes for the breakdown of refractory sulfides.
The second key area is the fundamentals of hydrometallurgical reactors, specifically pressure leaching autoclaves. In this field, I have developed an entirely new approach to the modeling of multistage continuous leaching reactors based on the statistical convolution principle, called the multiple convolution integral . This approach presents distinct advantages over the segregated flow and population balance methods currently in use. I have also applied this method to several reactors of industrial interest through my consulting activities, including most recently a novel combined autoclave + atmospheric leaching process for secondary copper ores which is currently being commissioned at the Sepon copper-gold mining complex in Laos at an estimated capital cost of US$190,000,000.
Most recently, my research has shifted toward process development, with the invention of a potentially important new atmospheric leaching process for the rapid and efficient recovery of copper from primary copper (chalcopyrite) concentrates, one of the most elusive and highly sought after process goals in the history of hydrometallurgy.
Refereed Journal Publications
- A. Ghahremaninezhad, T. Gheorghiu, D.G. Dixon, E. Asselin (2015) A model for silver ion catalysis of chalcopyrite (CuFeS2 . Submitted to Hydrometallurgy, accepted 21 April 2014.
- B.F. Rivera-Vasquez and D.G. Dixon (2015) Rapid atmospheric leaching of enargite in acidic ferric sulfate media. Hydrometallurgy, 152. 149–158.
- O.G. Olvera Olmedo, E. Asselin and D.G. Dixon (2014) Electrochemical dissolution of fresh and passivated chalcopyrite electrodes. Effect of pyrite on the reduction of Fe3+ ions and transport processes within the passive fil m. Electrochimica Acta, 127, 7–19.
- O.G. Olvera Olmedo, E. Asselin and D.G. Dixon (2013) Electrochemical study of the dissolution of enargite (Cu3AsS4) in contact with activated carbon. Electrochimica Acta, 107, 525–536.
- M. Eghbalnia and D.G. Dixon (2013) In situ electrochemical characterization of natural pyrite as a galvanic catalyst using single-particle microelectrode technique in ferric sulfate solutions. J Solid State Electrochemistry, 17, 235–267 .
- A . Ghahremaninezhad, D.G. Dixon, E. Asselin (2013) Electrochemical and XPS analysis of chalcopyrite (CuFeS2) dissolution in sulfuric acid solution. Electrochimica Acta, 87, 97–1 12.
- A. Ghahremaninezhad , D.G. Dixon, E. As el in (2012) The kinetics of the ferric/ferrous redox reaction on anodically passivated chalcopyrite (CuFeS2) electrode. Hydrometallurgy, 125–126, 42-49.
- G. Nazari, D.G. Dixon and D.B. Dreisinger (2012) The role of silver-enhanced pyrite in enhancing the electrical conductivity of sulfur product layer during chalcopyrite leaching in the Galvanoxrn process. Hydrometallurgy, 113–114, 177–184.
- G. Nazari, D.G. Dixon and D.B. Dreisinger (2012) The mechanism of chalcopyrite leaching in the presence of silver–enhanced pyrite in the Galvanoxrn process. Hydrometallurgy, 113-114, 122– 130.
- B. Rivera Vasquez, G. Viramontes Gamboa and D.G. Dixon (2012) Transpassive electrochemistry of chalcopyrite microparticle s. J. Electrochem. Soc., 159, C8–C 14.
- G. Nazari, D.G. Dixon and D.B. Dreisinger (201 1) The role of galena associated with silver enhanced pyrite in the kinetics of chalcopyrite leaching during the Galvanoxrn process. Hydrometallurgy, 111–112, 35-45 .
- M. Eghbalnia and D.G. Dixon (201 1) Electrochemical study of leached chalcopyrite using solid paraffin-based carbon paste electrodes. Hydrometallurgy, 110, 1–12.
- A. Ghahremaninezhad, E. Asselin , D.G. Dixon. (201 1) Electrodeposition and growth mechanism of copper sulfide nanowires. J. Phys. Chem., 115, 9320-9334.
- A. Ghahremaninezhad, E. Asselin and D.G. Dixon (201 1) One-step template-free electrosynthesis of 300 µm long copper sulfide nanowires. Electrochemistry Communications 13, 12-15.
- G. Nazari, D.G. Dixon and D.B. Dreisinger (201 1) Enhancing the kinetics of chalcopyrite leaching in the Galvanoxrn process. Hydrometallurg y 105, 251-258.
- B.F. Rivera Vasguez and D.G. Dixon (2010) Rapid atmospheric leaching of enargite in ferric sulfate media. Hydrometallurg y, accepted May 2010 pending minor revision.
- G. Viramontes-Gamboa, M.M. Peiia-Gomar and D.G. Dixon (2010) Electrochemical hysteresis and bistability in chalcopyrite passivation. Hydrometallurg y 105, 140-147.
- A.J. Fischmann and D.G. Dixon (2010) Upgrading of a chalcopyrite concentrate by reaction with copper(II) and sulfite – unexpected formation of Chevreul’s salt, Cu2S03·CuS03·2H20. M inerals Engineering 23, 746-751 .
- A. Ghahremaninezhad, E. Asselin and D.G. Dixon (2010) In-situ electrochemical analysis of surface layers on a pyrrhotite electrode in hydrochloric acid solution. J. Electrochem. Soc. 157, C248-C257.
- A. Ghahremaninezhad, E. Asselin and D.G. Dixon (2010) Electrochemical evaluation of the surface of chalcopyrite during dissolution in sulfuric acid solution, Electrochimica Acta 55, 5041- 5056.
- A.J. Fischmann and D.G. Dixon (2009) Awaruite (Ni3Fe) as a nickel resource – leaching with ammoniacal-ammonium solution containing citrate and thiosulfate. Hydrometallurg y 99, 214-224.
- S.C. Bouffard and D.G. Dixon (2009) Modeling the performance of pyritic biooxidation heaps under various design and operating conditions. Hydrometallurg y 95, 227-238.
- S.C. Bouffard and D.G. Dixon (2009) Modeling pyrite bioleaching in isothermal test columns with the HeapSim model. Hydrometallurg y 95, 215-226.
- D.G. Dixon, D.D. Mayne and K.G. Baxter (2008) GalvanoxTM – A novel process for recovery of copper from primary copper concentrates. Canadian M etallurgical Quarterly 47, 327-336.
- G. Viramontes-Gamboa, B.F. Rivera-Vasguez and D.G. Dixon (2007) The active-passive behavior of chalcopyrite: comparative study between electrochemical and leaching responses. J. Electrochem. Soc. 154 (6), C299-C3 II.
Refereed Conference Proceedings
- L.S. Quiroz-Castillo, O.G Olvera-Olmedo, P.J. Valenzuela-Guerrero, L. Dyer and D.G. Dixon (2014) Extraction behaviour of arsenic and copper from an enargite concentrate in catalyzed atmospheric leaching conditions. Hydrometallurgy 2014 . vol. I. CIM, Westmount. Quebec p 89–99.
- A. Ghahremaninezhad, D.G. Dixon and E. Asselin (2014) New insights into electrochemical processes at the chalcopyrite electrode/sol ution interface. Hydrometallurgy 2014. vol. 1, CIM, Westmount, Quebec, pp 385–395.
- O.G. Olvera-Olmedo, L.S. Quiroz-Castillo, D.G. Dixon and E. Asselin (2014) The dissolution rate of fresh And passivated chalcopyrite electrodes in the presence of pyrite. Hydrometallurgy 2014 vol. I CIM, Westmount , Quebec, pp 409-419.
- A. Gagnon, N, Backhouse, H. Darmstadt, E. Ryan, L. Dyer, D.G. Dixon (2013) Impurity Removal from Petroleum Coke. Light Metals 2013, TMS, Warrendale, PA, pp 1057-1062.
- M. E ghbalnia and D.G. Dixon (2012) Investigation of charge transfer resistance at pyrite electrodes modified by gold and silver nanoparticles. Electrometallurgy 2012 – TMS Conference, Orlando, Florida, 1 1–15 March 2012.
- L. Dver, M. Eghbalnia, D.G. Dixon. J. Rumball and E. Asselin (2012) Electrochemical evaluation of petzite leaching. Electrometallurgy 2012 – TMS Conference, Orlando, Florida, 1 1–15 March 2012.
- A. Ghahremanine zhad , E. Asselin and D.G. Dixon (2012) Cathodic reactions on oxidized chalcopyrite electrode surfaces. Electrometallurgy 2012 – TMS Conference, Orlando, Florida, 1 1–15 March 2012.
- D.G. Dixon and K .I. Afewu (201 1) Mathematical modeling of heap leaching under drip irrigation. Percolation Leaching: The statu s globally and in Southern Africa 201 1, SAIMM, Johannesburg, S. Africa, 7–9 November 201 1 , pp. 255–284.
- I . Ghanad and D.G. Dixon (201 1) Atmospheric leaching of enargite in acidic iron sulphate media in the presence of activated carbon. HydroCopper 201 1, 6th International Seminar on Copper Hydrometallurgy , Vina del Mar, Chile, 6–8 July 201 1.
- G. Naza ri, D.G. Dixon and D.B. Dreisinger (201 1) Effects of enhanced pyrite on the Galvanoxrn process. Clean Mining 201 1, 9th International Conference on Clean Technologies for the Mining Industry, Santiago, Chile, I 0-12 April 2011.