Group Leader. Dr RJ (Cobus) Kriek. Research Focus

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1 PGM P Group Group Leader Dr RJ (Cobus) Kriek Dr Kriek obtained his MSc in Chemistry on the Separation of Pt(IV), Pd(II) and Rh(III) by means of Differential Photocatalytic Reduction in 1994, and his PhD in Chemistry on the Separation of Platinum Group Metals: Photocatalytic Reduction and Complexation Equilibria of Pt(IV), Pd(II) and Rh(III) in 1998, both from the University of Stellenbosch, South Africa. Subsequent to obtaining a MBA Environmental Management degree from the University of Lincoln (UK) in 1999 he joined MINTEK, the Council for Mineral Technology in South Africa, working in the fields of environmental management and business development. In October 2004 he joined the North-West University s School of Chemistry at their Potchefstroom Campus. He is currently completing a MSc Hydrometallurgical Engineering degree at the University of Cape Town working on the Leaching of Selected PGMs: A Thermodynamic and Electrochemical Study Employing Less Aggressive Lixiviants. Research Focus An active group focusing on certain aspects of the chemistry and hydrometallurgy of the platinum group metals (PGMs) is being established at the North-West University (NWU), which is located in South Africa s North-West Province, also known locally as the Platinum Province as the majority of the world s platinum reserves are located and mined here. We see the research focus as dynamic, within the boundaries of industrial applicability, so as to accommodate new members to the group. Currently, however, our research focus can be schematically depicted as follows: Recovery Photocatalysis PGM Electrocatalysis Fuel Cell & Electrolyzer Speciation Leaching Electrochemistry Recovery & Processing 1

2 Key Focus Areas The key research focus areas, by no means more important than the supporting research focus areas, currently include photocatalysis, leaching and electrocatalysis. We term them key areas as they are directly linked to the areas of application, i.e. recovery, processing, and fuel cells & electrolyzers. Leaching Traditionally the PGMs are being leached employing rather aggressive methods, e.g. aqua regia, chlorine gas in a strong hydrochloric acid medium, etc. This results in increased costs due to continuous maintenance of equipment and high reagent consumption due their volatility. Research is underway to investigate the effectiveness of less aggressive lixiviants. Electrocatalysis HO 2 & O2 HO 2 & H2 ANODE CATHODE O2 4e - 4e - 2H 2 O 4H + 4H + 2H H 2O O 2+ 4H 4e + - 4H + 4e 2H 2 HO 2 HO 2 Electrode (Anode) PGM Electrocatalyst Electrode (Cathode) PGM Electrocatalyst Proton Exchange Membrane (PEM) Electrolyser for the production of hydrogen We are embarking on a project to develop, characterize and test different PGM electrocatalysts for ultimate application in electrolysers for hydrogen production (as well as in fuel cells). As fossil fuels are not renewable, together with their negative impact on the environment in contributing to the greenhouse effect and global warming, there is a push for developing a future hydrogen economy. Electrolysers produce hydrogen through an electrochemical process and fuel cells produce electricity through an electrochemical process employing, amongst other things, hydrogen. Both of these devices employ an electrocatalyst at the cathode and anode, which in the majority of cases employ a single PGM, a combination of PGMs, or a combination of PGMs and base metals. Photocatalysis Recovery of PGMs in the ppm range holds great benefit if it could be accomplished economically and on an environmentally friendly manner. Our research focuses on the development of recovery processes through the application of different photocatalysts, e.g. TiO 2 and others, under UV-illumination, for the recovery of especially Pt, Pd and Rh from solution. Not only do we investigate the photocatalytic reduction of the PGMs, but we also investigate different reactor setups so as to obtain the most optimal configuration. 2

3 Photocatalytic Charge Generation Pathways Support Focus Areas Speciation The photocatalytic reduction of PGMs depends very much on the actual PGM-complexes in solution, as shown by our research, whereas the leaching of PGMs depend very much on the stability of specific PGM-complexes in solution. As the formation constants (stability constants) of PGMs are to a large extent nonexistent, we conduct speciation studies employing spectrophotometry and potentiometry to provide us with these data. Electrochemistry Making use of rotating disk working electrodes (RDE) manufactured with the specific PGM under investigation, an electrochemical investigation provides information on the potentially optimum conditions for the leaching of the specific PGM. Rotating ring disk electrode (RRDE) studies of the PGM electrocatalyst under investigation, provides information on the effectiveness of the electrocatalyst in catalysing specific electrochemical reactions. Key Equipment Speciation Analytik Jena Diode Array UV/VIS Spectrophotometer with Hyperquad Speciation Modeling Software Metrohm Double Buret Potentiometric Autotitrator with Hyperquad Speciation Modeling Software 3

4 Electrochemistry PAR 273A Potentiostat with a Solartron HF 1255 High Frequency Response Analyzer and Pine Research Instrumention Rotating Electrodes and Speed Controller Allows Rotating Disk Electrode studies with Impedance Princeton Applied Research VMP3 Double Channel Potentiostat with EC-Lab Software, 20 Amp Booster Channel, and Pine Research Instrumention Rotating Electrodes and Speed Controller Allows Rotating Ring Disk Electrode Studies with Impedance Leaching External Temperature Controller, with Haylar Coated Pt100 Resistance Temperature Detector, for Heating Mantle, and Overhead Stirrer with Digital Display for Accurate Speed Control Students PhD Student(s) Neels le Roux Speciation of Pd with CN -, OCN - and SCN - - a spectrophotometric investigation. Elias Aphane Leaching of Pt, Pd and Rh as a means of recovery from catalytic converters. 4

5 Masters Student(s) Adele Petzer Comparing the photocatalytic reduction kinetics of Pt in a flow through and a batch photoreactor. Angelique Venter Synthesis, characterization and testing of Pt/Zr electrocatalysts for the electrolytic production of H 2 via the Hybrid Sulphur process. Hons BSc Student(s) Gregory Steyn An introductory study to the development of Pt/Nb electrocatalysts for the electrolytic production of H 2 via the Hybrid Sulphur process. Research Assistant(s) Hugo Opperman Photocatalytic reduction of platinum group metals. Henry Hoek Speciation of platinum group metals. 5

6 Publications Photocatalysis 1. R.J. Kriek, W.J. Engelbrecht, and J.J. Cruywagen, Separation and Recovery of Some Platinum Group Metals (PGM s) by means of Selective Photocatalytic Reduction, Journal of the South African Institute of Mining and Metallurgy, Volume 95, No. 2, March/April V.A. Patterson, H.M. Krieg, R.J. Kriek, and H. Bisset, Direct Synthesis of a Titania Membrane on a Centrifugally Casted Tubular Ceramic Support, Journal of Membrane Science, 285, 2006, 1-3 Speciation 1. J.J. Cruywagen and R.J. Kriek, Complexation of Palladium(II) with Chloride and Hydroxide, Journal of Coordination Chemistry, Volume 60, Issue 4, 2007,