Personally I found Biohydromet '12 to have been a very special conference, as it came at a time when rapid advances in our understanding of the science of microorganisms had in effect awoken biohydrometallurgy from its long slumber, looking as though it might start to realise its true potential and provide real benefits to the minerals industry. So we looked forward in anticipation to Biohydromet '14 to assess whether the hopes and aims of two years ago had been realised.
Monday 9th June
FLSmidth and International Mining, I welcomed the 65 delegates from 21 countries this morning and then handed over to Chris Bryan, of University of Exeter, one of our consultants, who summarised the last conference and looked ahead to what we have in store in the next few days. He remarked on what a pleasure it was to see so many of the big names in biohydrometallurgy - what a guest list!
Biohydrometallurgy is becoming more important in the minerals industry, accounting for the processing of over 15% of global copper and 3% of gold and there are some very exciting developments and planned operations, many in Europe. There are new applications to a wider range of resources and biohydrometallurgy is becoming important for the processing of wastes, and reprocessing of tailings. The future of biohydrometallurgy is therefore surely bright.
Barrie Johnson of Bangor University, UK, then got the conference off to a fine start with his keynote lecture on the potential use of bacteria to extract metals from oxidised ores. Biomining is traditionally practiced to accelerate the oxidative dissolution of sulphide minerals, but recent work has demonstrated that many acidophiles can accelerate the reductive dissolution of ferric iron minerals, such as goethite. This could be used to extract metals from oxidised ores, such as laterites and manganese nodules, at low (ca. 30°C) temperatures.
Barrie was also co-author of the second paper of the morning, presented by his colleague Rose Jones, who discussed the potential of a novel acidophilic bacteria for remediating metal-rich mine waters. A presentation by Suzanne Rea, of Australia's CSIRO, on the application of salt-tolerant bioleaching microbes for mining operations where fresh water is scarce, then took us to the morning coffee break.
|Bangor University's Carmen Falagan, Barrie Johnson and Rose Jones,|
with Patrick Nee of Universal Bio Mining, USA
|Chiachi Hwang discusses the poster of Ioannis Vyrides|
of Cyprus University of Technology
|Yair Farber (centre) with Dave Dew and Paul Norris (UK)|
|Arevik Vardanyan with Ioannis Vyrides|
The afternoon session began with two papers from the University of Cape Town (UCT). Rob van Hille discussed the effect of thiocyanate on BIOX® organisms and Sue Harrison the effect of acid stress on selected mesophilic bioleaching micro-organisms, which is critical during the start-up of heap bioleaching. Stoyan Gaydardzhiev of the University of Liege, Belgium, then presented observations on the bioleaching of carrolite with a mixed culture of acidophilic bacteria.
A further paper from UCT, presented by Rob Huddy, provided an insight into the building blocks of the Metallosphaera hakonensis biofilm. The results highlighted the differences in the thermophilic mineral-microbial-interfacial environments created as a function of inoculation conditions and across tank and heap bioleach systems for processing mineral sulphides.
|Rob Huddy, Rob van Hille and Sue Harrison|
After a quick coffee, it was time to unwind and network, with the usual 6 mile coastal path walk, ending up, slightly damp at Falmouth's 17th century Chain Locker pub, where many delegates sampled real Cornish ale for the first time (see also posting of 9th June).
|At Swanpool Beach|
|At the Chain Locker|
For some years now biohydrometallurgy has been one of the process options evaluated by the mining industry for base metal sulfide and sulfidic-refractory precious metal projects. However, the difficulties of process selection are increasing substantially, because of declining ore grades, complex mineralogy, deep deposits, and environmental and societal pressures. Biohydrometallurgy is likely to play an increasing role in future mines, because the technology offers various processing methods and there is opportunity for innovation. Corale Brierley, one half, with husband Jim, of Brierley Consultancy LLC, USA delivered a fine keynote this morning highlighting how it is the obligation of researchers and practitioners of biohydrometallurgy to create new application approaches and to innovate methods effective in bioprocessing ores of the future. Her presentation looked at the mines of the future and addressed how advances in biohydrometallurgical processing might be commercially used.
She based her presentation on the bioheap leaching of copper ores, and highlighted some interesting facts, such as that 50% of all copper mined in the world was in the last 25 years, and that 18-20% of global copper production is now by bioleaching. She stressed that the growth in renewable energy is set to dramatically increase copper use.
|Corale Brierley with Pieter Van Aswegen, Jim Brierley and Jan Van Niekerk|
Chalcopyrite (CuFeS2) is the most abundant copper-containing mineral in the lithosphere, but is known to be highly recalcitrant to effective bioleaching. Often only 20-30% of its copper content is leached by conventional bioleaching bacteria, though it has been shown that more efficient extraction can be achieved at elevated temperatures (~80°C) or low redox potentials (EH ~650 mV). Although copper occurs as Cu(I) and iron as Fe(III) in chalcopyrite, little attention has been given to redox transformations of these two metals that occur during (bio)leaching, so it was interesting to hear Carmen Falagan, of Bangor University, UK discuss her work on the bioleaching significance of copper speciation during the abiotic and microbial dissolution of chalcopyrite.
Sue Harrison of UCT, South Africa then discussed the effect of physicochemical conditions on the growth and activity of Acidithiobacillus ferrooxidans on low grade chalcopyrite ore, with particular emphasis on heap leaching systems, where quantifying microbial growth and activity in both the flowing solution and in the mineral associated phases is important.
Sabine Kutschke of the Helmholtz-Institute Freiberg, Germany, took us up to the coffee break by describing the German-French project EcoMetals, which focuses on metal production from Cu- bearing primary and secondary resources in Europe. The objectives are the development of alternative methods in mineral processing involving biohydrometallurgical methods, their up scaling, the determination of economical and sustainable performances, the demonstration of bioprocesses for treatment of mineral processing wastes, and the life cycle assessment as well as the sustainability assessment for the proposed technologies.
|Sabine Kutschke (right) with Fabian Giebner|
and Simone Schopf of TU Bergakademie Freiberg
|Lucy McTaminey with Amanda|
|Sophia Kostudis is wired up|
for her presentation
Following on from this Sophia Kostudis of the Helmholtz Institute Freiberg, Germany described the heterotrophic bioleaching of the German Kupferschiefer copper ores, which are not amenable to leaching due to their high carbonate content, using microorganisms adapted to mid and higher pH ranges.
In heap bioleaching processes, air is often injected into the heap to accelerate the leaching efficiency. Chen Bowei of the General Research Institute for Nonferrous Metals, China, described how simulated heap bioleaching of a pyritic chalcocite ore was conducted at 40 °C with elevated CO2 and N2. The results indicated that the limitation of oxygen could change the bioleaching microbial community and the elevation of CO2 and N2 is favourable for the growth of sulphur-oxidizer and iron-oxidizer separately, which could be used for the regulation of the role of microorganisms in mineral bioleaching.
|Chen Bowei (right) with co-authors Li Wenjuan and Yang Limei|
The use of oxygen is a well-known practice in high-temperature bioleaching reactors, whereas air is usually preferred in medium and low-temperature operations. Anne Guezennec, of BRGM, France, described an investigation of the use of oxygen-enriched atmospheres in bioleaching reactors at 40°C in order to improve the global heat balance of the system.
Mondo Minerals is the world’s second largest talc producer and owns two talc mines, namely Sotkamo and Vuonos, in central Finland. Mariekie Gericke, of Mintek, South Africa, discussed the option to use bioleaching for the production of nickel as a metal hydroxide product (MHP) from nickel-cobalt-arsenic containing flotation by-products of the talc industry. The results show that nickel and cobalt recoveries in excess of 95% could be achieved and that stable iron and arsenic precipitates and good quality MHP could be produced.
|Mariekie Gericke with co-authors Pieter Van Aswegan of PMet Consulting,|
South Africa and David Dew of Dewality Consultants, UK
After a quick coffee it was the long, but worthwhile, coach ride to St. Austell for the conference dinner at the world famous Eden project (see also posting of 11th June). We were privileged, as usual, to have exclusive use of the Eden Project with dinner in the Mediterranean biome, used in filming of the 2002 James Bond film Die Another Day.
Wednesday 11th June
Jan van Niekerk, of BIOMIN, South Africa, opened a day containing an interesting eclectic mix of papers. BIOMIN has been successfully delivering the BIOX® process, for the treatment of refractory gold concentrates for over two decades. To date 12 successful BIOX® plants have been installed in 8 countries spanning 4 continents, confirming the technical and commercial viability of the process. BIOMIN introduced a second technology in 2010, the ASTERTM process, for the biological destruction of cyanide and thiocyanate. Two commercial ASTERTM plants are currently in operation in South Africa and Kazakhstann. Jan showed how the delivery of a successful commercial biooxidation project is dependent on the integration of the technology with the specific requirements of the project.
Jan's paper was followed by an interesting presentation by Naoko Okibe, of Kyushu University, Japan, who discussed the biooxidation of Alaskan refractory gold ore concentrates containing arsenopyrite and pyrite as major sulfide mineral components. The role of individual microbes in biooxidation cultures containing toxic As(III) was discussed.
|Naoko Okibe (right) with Sabrina Hedrich at Eden Project|
|Stoyan Gaydardzhiev (right) with Chris Bryan and Arevik Vardanyan|
|Viktor 2nd right at last nights Eden dinner with Clara Costa|
and husband Joao and Ann Grandin
|Patrick D'Hugues (right) with Cecile Leycuras, Neilish Syna and Paul Norris|
|Jon with Amir Nazari and co-author Kristian Waters at Falmouth's Chain Locker|
The discharge of As-containing acid mine drainage may cause contamination of water sources with heavy metals, and Anna Kaksonen, of CSIRO Land and Water, Australia discussed the biotreatment of As-containing acid mine drainage using sulfate reducing granules in an upflow anaerobic sludge blanket reactor.
|Anna (right) and colleage Suzy Rea enjoying the steamy Rain Forest at Eden with Marieke Gerieke|
In gold mining, arsenic often co-occurs with ammonium deriving from the degradation of cyanide used for gold recovery. Stefano Papirio of Tampere University, Finland, introduced work assessing the feasibility of maintaining nitrification in the presence of arsenic. Candidatus Nitrospira defluvii and other species belonging to Nitrospirae were the main nitrifying microbial species, tolerating high As levels and making nitrification a potent process for ammonium oxidation in mining waters. A further paper from Tampere University, presented by Sarita Ahoranta, discussed the sorption of arsenic onto biogenic iron precipitates from mining waters.
Sarita Ahoranta and Stefano Papirio with Jarno Makinen (left)
|Panellists Paul, Jim and Pieter|
Things are obviously changing rapidly in biohydrometallurgy, which is set to become a very important part of the mineral processing toolbox. So we look forward now to Biohydromet '16, which will be held in Falmouth again in June 2016.
The Proceedings from Biohydromet '14 are available from MEI, and selected papers will be published in a special Biohydrometallurgy issue of Minerals Engineering after peer-review.