Monday, 30 June 2014

Innovations in the processing of difficult and low grade gold ores

While declining grades has always been an ever-present risk for all metallurgical commodities, it has become particularly severe for precious metals where average precious grades are trending towards 1 gram per tonne, or lower. Exploration success in finding long-life, medium grade deposits has been poor with most recent finds being low grade, complex ores. New precious metal resources are more difficult to process due to a host of factors such as mineral refractoriness, high sulfur ores, gold ores with high levels of copper, high silver-gold ores , carbonaceous gold ores, clay-rich ores and gold ores with high levels of reactive sulfides, or a combination of these factors. Moreover, the mining, comminution and processing of low grade gold ores with the concomitant waste generation and reagent consumption, in the context of declining commodity prices and rapidly increasing energy costs, require an overall rethink of both current operations and the feasible extraction of future mineral resources.
Jacques Eksteen at a previous Falmouth conference
Some recent developments in the areas of pre-concentration, flotation, leaching and competitive adsorption within the context of difficult and low grade gold ores will be reviewed in a keynote lecture by Prof. Jacques Eksteen at Precious Metals '15 in Falmouth next May.
Jacques Eksteen is the manager of the Gold Processing Technology Group at the Western Australian School of Mines, Curtin University and is the project manager of the AMIRA P420E project on “Environmentally responsible gold ore processing” which is supported by 14 industry sponsors. He was the Group Consulting Metallurgist for Lonmin Plc in Smelting and Refining from mid-2007, and was appointed as professor and chair: extractive metallurgy at Curtin University in February 2012. He has been a regular contributor to MEI's Precious Metals conferences, and also to the Nickel Processing events which run back to back with them.

Sunday, 29 June 2014

Polzeath to Padstow

A very pleasant day out today, walking from Polzeath on the north Cornwall coast, to Padstow.

This is an easy 4 mile walk as the coast path follows the dunes on the estuary of the River Camel, passing by the church of St. Enodoc, where lie the remains of the poet John Betjamin (see posting of 27th January 2013).

Approaching the Camel Estuary
Camel Estuary

Walking the dunes

At Rock, we took the ferry across the Camel to a very busy Padstow. After a quick pasty lunch we left the crowds behind and returned to Polzeath, which is only a 40 mile drive from Falmouth.

Padstow Harbour

More Cornish Walks
More on Cornwall

Thursday, 26 June 2014

Process Mineralogy '14 programme published

The provisional programme for Process Mineralogy '14, which will be held in Cape Town in November, has now been published.

The opening session of Process Mineralogy '14
This is very provisional at this stage, and as the programme evolves updates will be posted on the conference website (Twitter #ProcessMineralogy14). If you like the programme, and feel that you can contribute, please send a short abstract as soon as possible.

We are also pleased to announce a new dinner venue. The conference dinner will be held at moyo Kirstenbosch, at the foot of Table Mountain in the beautiful Kirstenbosch Botanical Gardens.

Kirstenbosch Gardens

Wednesday, 25 June 2014

Is South Africa's precious metals era drawing to a close?

Last year I reported on South Africa's decline as a major gold producer (posting of 25th September 2013), from being the number 1 producer a decade ago to now number 6 in the world rankings.

Is platinum, of which South Africa has 90% of the world’s deposits, set to go the same way as the country's ageing, deep gold mines? This is the question asked in African Mining Brief, reporting on a recent University of Cape Town Graduate School of Business round table.

The current mining strike, which ends today, is the latest challenge to beleaguer South Africa's battered and once hugely profitable platinum industry. After 2008, South Africa, the world’s largest producer of platinum, was hard-hit by the global recession and erosion of the market for platinum and its by-product, rhodium. Making a recovery, it has since been knocked by a surge in the scrap supply and the recycling of platinum by other producers, as well as by palladium, produced largely by Russia, and used as a platinum substitute catalyst notably in the auto industry. The current platinum strike has been the longest and most expensive strike in South Africa’s mining history, with some 70,000 miners now returning to work after downing tools on 23 January 2014, costing mining firms R19 billion in lost revenue, miners approximately R8.8 billion in wages and the country's GDP a drop of 0.6% in the first quarter.

Platinum itself is extremely labour-intensive to mine in deep shafts and complex to process and the panel forecast that opencast mines, which are low in investment but high in environmental impact, and mechanisation, lie ahead, a shift away from traditional labour-intensive shaft mining.

All in all the future looks bleak for South African mining, vindicating our decision to move MEI's Precious Metals '15 to Falmouth, close to the rapidly evolving European precious metals producers.

Monday, 23 June 2014

Young Persons' Awards

It is always good to hear of young people in our industry being awarded for their endeavours, so I was pleased to receive an email recently from Prof. Dee Bradshaw of JKMRC, Australia, who is currently on sabbatical at Hacettepe University, Turkey. Dee is also one of MEI's two consultants for Flotation '15. She sent me news of two recent alumni from the Sustainable Minerals Institute at the University of Queensland (UQ) who have both published in Minerals Engineering and who have been rewarded with recognition from their University for outstanding theses. She "thoroughly expects both of them to be leaders in the field in the future".
The two young researchers each won a prestigious Dean’s Award for Research Higher Degree Excellence 2013. The award, given by the Dean of the UQ Graduate School, gives formal recognition to outstanding PhD and MPhil graduates who have demonstrated excellence in a research higher degree and who have been commended by advisers and independent examiners for substantial contribution to their field of research.
Dr. Wenying Lui's PhD thesis was "A quantitative risk-based approach for improving water quality management in the minerals industry: flotation as an example" Her advisers were Prof. Chris Moran and Dr. Sue Vink.
Wenying has published 5 papers in high-ranking international journals and has also published several conference papers, having presented her work at Procemin 2011 in Chile and the SME Annual Meeting in USA in 2012. She is currently working as a postdoctoral research fellow at the University of British Columbia in Canada.
Wenying (left) with fellow PhD students and staff, 2011
Gerson Sandoval-Zambrano‘s PhD project was entitled "Development of a novel strategy to estimate flotation recovery as a function of particle size and mineral liberation." Gerson was supervised by Dr. Elaine Wightman, Prof. Dee Bradshaw and Dr. Gonzalo Montes-Atenas.
After finishing his undergraduate degree at the University of Concepcion, Chile and gaining some relevant industrial experience in Chile, Gerson joined the JKMRC, Sustainable Minerals Institute (SMI) in 2009 as a PhD candidate. The aim of his research was to develop a novel methodology to predict the efficiency of separating valuable minerals from waste based on the characteristics of individual particles. The outcomes from his work have the potential to reduce the cost and time typically associated with conducting the detailed analysis required to develop a particle property based model of a mineral processing circuit. 
During his candidature Gerson wrote four papers, one of which was published in Minerals Engineering. Two of his papers were published in the peer-reviewed conference proceedings from Procemin 2011 in Chile, which he attended and presented his work. Gerson also presented his work at Flotation '11 and Flotation '13 in Cape Town. This led him to win the SMI Student Publishing award in 2011. In 2012 Gerson was the 23rd winner of the Ian Morley Prize which acknowledges the best overall performance and achievements as a postgraduate student at the JKMRC. He is currently working as a senior engineer at Aminpro, Santiago, Chile.
Gerson´s farewell from Brisbane (front: Gerson, Jocelyn Quinteros, Dr. Cathy Evans,
Prof. Dee Bradshaw. Back: Dr. Elaine Wightman, Prof. N.W. Johnson, Mrs Johnson)
Congratulations Wenying and Gerson, I am sure we will hear much more of you both in the future.

Thursday, 19 June 2014

Cornish Mining Sundowner- June

The sun shone brightly last week for the SRCR '14 sundowner, and has continued to do so all week, so it was a very warm evening at the Chain Locker pub in Falmouth for today's Cornish Mining Sundowner. A disappointingly low turnout, however, probably due to tonight's vital World Cup match between England and Uruguay, which I rushed home to watch (even more disappointing!).

Good though to catch up with a few mineral processors, including Bentley Orchard of Weir Minerals, and Jim Turner, who graduated from CSM in1984 and is now based in nearby Penryn as a senior mineral processing engineer with Micon International.

With Bentley Orchard, Steve Wilson and Jim Turner
Also in attendance were Steve Wilson, tailings backfill designer with Paterson & Cooke, and his colleague Paul Ainsworth, who graduated in the last batch of mineral processors from CSM in 2006.

Paul Ainsworth and girlfriend Charlotte with Steve Wilson
The next Sundowner will be held on Thursday July 24th, and as always there is an open invitation to anyone who has any connection with the minerals industry to join us at the Chain Locker.

Wednesday, 18 June 2014

Report on Sustainability through Resource Conservation and Recycling '14

Sustainability through Resource Conservation and Recycling '14 (SRCR '14) was held at the St. Michael's Hotel, Falmouth, Cornwall, from June 11-12, 2014, and was sponsored by Outotec, Ecoseed, Industrial Minerals and AT International.

Thursday 12th June

SRCR is one of MEI's smaller conferences, and this morning Jon welcomed the 38 delegates, nine of whom were here earlier in the week for Biohydromet '14. Despite the relatively small number, 17 countries are represented at the conference, Australia, Belgium, Brazil, Canada, Chile, China, Finland, France, Japan, Morocco, South Africa, South Korea, Spain, The Netherlands, Turkey, UK, USA.

Jon with Markus Reuter
Metals are an essential and critical component of today’s society; their ubiquitous presence in virtually all energy and material production processes, products, infrastructure, confirms this. Metals play a key role in enabling sustainability through societies various high-tech applications. However, the resources of our planet are limited, as is the strain to which we can subject it in terms of emissions, pollution, and disposal of waste. For these reasons, finding ways to lower the environmental footprint of our collective existence and therefore lowering greenhouse gas emissions and help mitigate climate change is a vital priority. This was the theme of the keynote lecture from Markus Reuter, of Outotec, Finland, and MEI's consultant, who summarised the UNEP report on Metal Recycling: Opportunities, Limits, Infrastructure.

Glen Corder, of the University of Queensland, Australia, then discussed the translation of global knowledge on industrial ecology to enhance uptake of metals recycling in an Australian context. Australia’s rich stocks of mineral resources have been the source of national wealth and competitive advantage in the past. However, the security of this wealth is not guaranteed into the future, and what were once considered waste materials are now becoming accessible and valuable as ‘above-ground’ mineral resources. Globally there is growing capacity and innovation in recycling, closed-loop supply chains and Australia’s role as a global leader in primary production must anticipate and adapt to the implications of a rise in the importance of recycling.

Alan Jean-Marie of Altran Research, France, then took us up to the coffee break with a presentation on the coupling life cycle assessment and process simulation to evaluate the environmental impacts of plastic waste management applied to PET bottles recovery.

Antoinette van Schaik of MARAS, The Netherlands, took the floor after coffee with 10 design for recycling rules. Based on the information gathered in this study combined with the expertise of the authors as also published in the recent UNEP report on Metal Recycling, comprehensive simulation based Design for Recycling (DfR) rules and guidelines have been developed. These rank from simple guidelines and material (in) compatibility tables to detailed recycling system based DfR rules. The rules address the technological and economical possibilities and limits in the entire recycling system from design to metallurgy in relation to material interactions, recovery, losses and emissions and resource efficiency.

The concept of sustainability, which is now well entrenched in the minerals industry, can be an effective driver for higher levels of innovation, as discussed in a second paper by Glen Corder. With the minerals industry venturing into riskier locations, new mining projects need to deliver both strong sustainability benefits while meeting the necessary technical and financial requirements. Improved approaches to recycling, resources conservation, energy and water efficiency, greenhouse gas reduction, biodiversity, local enterprise development, and community development programs all meet the aims of good sustainability practice and require innovative techniques to move away from the ‘business as usual’ paradigm.

Glen Corder with Hiroki Hatayama of Japan
The global demand for minerals is defined by social and financial needs, and to ensure effective environmental protection, a number of tools and techniques have been developed. One of the most widespread tools is the Environmental Impact Assessment (EIA). This technique has many advantages, but it has also a number of disadvantages. Jorge Castilla-Gómez, of Madrid School of Mines, Spain discussed the development of a methodology to establish an environmental analysis focusing on the evolution of impacts on the environment with time.

Jorge Castilla-Gómez with Isabelle Demers of UQAT, Canada
The long-term generation of acid rock drainage (ARD) from sulfide-bearing mine waste is a major environmental liability for the mining sector. Previous studies have demonstrated that these ARD risks can be effectively avoided, and resource recovery simultaneously improved, through the pre-disposal removal of sulfide minerals, by means of flotation, as discussed by Jennifer Broadhurst, of the University of Cape Town, South Africa. She showed how life cycle assessment tools have been used to quantify and rigorously assess the environmental consequences of the flotation process for the desulfurisation of copper sulphide tailings, using a xanthate collector. The desulfurisation flotation process results in a significant decrease in human and eco-toxicity impacts, but an increase in GHG emissions and global warming potential, in comparison to conventional tailings disposal. Information from this study is used to identify improvement opportunities and guide further developmental studies.

Jennifer Broadhurst with Rabei Argane of Morocco
Following the lunch break Elisabeth Maris of Institut de Chambéry, France, presented a case study of a proposed methodology for characterisation of plastics contained in WEEE, then Liang Li of the Pangang Group Research Institute, China presented a thermodynamic analysis of the extraction of titanium from Ti-bearing BF slag.

Elisabeth Maris, with Amanda, and Chris Brough (UK)
Hiroki Hatayama of the National Institute of Advanced Industrial Science and Technology, Japan discussed methods of improving mineral extraction by reducing losses in mining and recycling.

Hiroki Hatayama (right) with Ryo Kasuya of Japan
Abandoned tailings ponds have been exploited without control for many years in the Moulouya region of Morocco, as a source of aggregate for rendering mortars. The aims of research presented by Rabei Argane of Université Cadi Ayyad, Morocco, was to assess the durability of the resulting tailings-based renders and to study their behavior when exposed to standard detrimental agents. The results confirmed that the use of mine tailings as aggregates engender a negative impact on the durability of renders.

The weather was perfect in the late afternoon for the 9 km coastal path walk into old Falmouth, and beers at the 17th century Chain Locker pub (see also posting of 13th June)

Overlooking Falmouth from the coast path





Friday 13th June

Christopher Brough of SRK Consulting Ltd, UK) discussed the former Bicapa-Tarnaveni chemical works in Romania, whhich processed chromite ore to create a sodium dichromate product. Inappropriate environmental stewardship of hexavalent chromium resulted in a significant contamination legacy. A recent environmental assessment of the site recommended that the waste storage facility (WSF) should be capped and a groundwater pump and treat solution should be installed, to treat the already contaminated groundwater. However, a second reprocessing option has been assessed, and if successful will significantly reduce the liability associated with the site and turn the WSF into a resource. Initial resource assessments of the WSF have established a potential resource for chromium, magnesium and calcium.

Management of acid mine drainage from diffuse sources is a major challenge facing the mining industry in South Africa. Semi-passive or low maintenance treatment options are most appropriate. Rob van Hille, of the University of Cape Town, discussed the optimisation of a semi-passive process, based on biological sulphate reduction with subsequent partial sulphide oxidation in a floating sulphur biofilm.

Two papers by Isabelle Demers, of UQAT, Canada showed how in operating mines acid mine drainage (AMD) is often treated using lime. This process generates a significant amount of sludge that contains metal hydroxide precipitates, gypsum, and unreacted lime. The sludge may have interesting geotechnical and geochemical properties and might be used as a partial cover (oxygen barrier) to prevent AMD generation from waste rocks and tailings. The results showed that mixtures of sludge and waste rocks, sludge and tailings and sludge and soil may be integrated in an AMD prevention and control strategy at Doyon mine site in Canada. Furthermore, the sludge stored at the Doyon mine site harbours significant vegetation after only a short period of time.

Zeynal Erguler of Dumlupinar University, Turkey also discussed the rehabilitation of acid mine drainage, at an abandoned lignite mine site, utilising egg-shell as an absorbent. He also discussed the effect of particle size on acid mine drainage.

Barbara with Zeynal Erguler and Ozlem Bicak of Turkey

The ASTERTM  process is used to bioremediate cyanide- (CN-) and thioocyanate- (SCN-) containing waste water. This process reduces the CN- and SCN- concentrations efficiently to below 1 mg/l, facilitating reuse of process water or safe discharge. Two papers presented by Rob Huddy of the University of Cape Town discussed characterisation of the complex microbial community associated with the ASTERTM  thiocyanate biodegradation sysstem and the evaluation of the ASTERTM  process in the presence of susspended solids.

Rob Huddy and Rob van Hille with Jorge Castilla-Gómez
The morning session finished with a paper from Kyoung Kuen Yoo of the Korea Maritime and Ocean University, who discussed the effect of hydrogen peroxide addition on the citric acid leaching of Pb from contaminated soil.

Relaxing between sessions in the hotel gardens
The final session commenced with a presentation by Chenna Borra of Katholieke Universiteit Leuven, Belgium on the leaching of rare earths from red mud, and later in the afternoon Quentin Dehaine of Université de Lorraine, France discussed the recovery of the rare-earths Ce, La and Nd and rare-metals Nb, Sn, and W from wastes of a kaolin production plant in Cornwall.

Nitrate is released into the environment during mining operations, due to the use of N-based explosives and leaching agents such as cyanide. Stefano Papirio of Tampere University, Finland presented work on the assessment of nickel on denitrification of mining waters in fluidized-bed reactors.

Electric cables are essential constituents of consumer goods such as automobiles and electrical and electronic equipments. Scrap cables are traditionally sorted by physical separation methods. These techniques have limitations and lead to a loss of copper in the reject fractions that cannot currently be recycled and which are landfilled. Fanny Lambert of the University of Liege, Belgium presented a study to assess the feasibility of recovering copper from these reject fractions by using hydrometallurgy.

Fanny Lambert (right) with Elisabeth Maris
Mauricio Torem of the Catholic University of Rio de Janeiro, Brazil also presented biotechnology work, on the enhancement of biosorption of lead and cadmium ions from aqueous solution by the microorganisms Rhodococcus opacus and Rhodococcus ruber.

Mauricio Torem with Romke Kuyvenhoven (Chile) and Beatriz Firpo (Brazil)
We have two representatives from the Pangang Group Research Institute in China, and Lian Li presented their work on process optimization in vacuum distillation for titanium sponge preparation and magnesium recycling.

Liang Li and co-author Kaihua Li, with Li Jing of
Liaoning University of Science and Technology, China
The conference closed with a presentation by Sadan Kelebek of Queen's University, Canada who discussed the mineralogical characteristics of nickel and copper values in waste refractory bricks and their potential for upgrading by flotation and magnetic separation.

Sadam Kelebek (right) with Chenna Rao Borra (Belgium)
In closing the conference, Outotec's Markus Reuter stressed that minerals are at the centre of sustainability. The aim of the SRCR series of conferences has been to transfer the rich source of mineral processing knowledge accumulated over the years to a wider community dealing with waste processing and untilisation, recycling etc. Acknowledging this we have decided to change the title of future conferences to Sustainable Minerals, and Jon closed the conference with an invitation to scientists of all related disciplines to convene in Falmouth in June 2016 for Sustainable Minerals '16.

The Proceedings from SRCR '14 are available from MEI and selected papers will be published in a special issue of Minerals Engineering after peer-review.

Tuesday, 17 June 2014

Alan Apling

Sad news in this evening of the death of Dr. Alan Apling, former mineral processing lecturer at the University of Leeds.

Although we lost touch after his retirement, we used to meet up in various exotic locations around the world in the 1990s.

The photo below was taken in Antalya, Turkey in 1992. Alan is on the far left, seated next to Julia Mertins, Barbara, and Alan's wife, Jennie. In the foreground are Chris Bailey, Ekkehart Mertins and Doug Jenkinson.


Monday, 16 June 2014

Biohydromet '14 Conference Diary

Biohydromet '14 was held at the St. Michael's Hotel, Falmouth, Cornwall from June 9-11, 2014. Two years ago, Biohydromet '12 was held in Falmouth, and in their summary of the conference MEI consultants Patrick d'Hugues, Sue Harrison and Chris Bryan felt it evident that bioheap leaching is one of the main targets for R&D and industrial applications, but tank leaching still has an important role. They highlighted the great potential for the use of biotechnology in the processing of secondary resources such as mine wastes and waste electronic equipment, and noted that emphasis should be given to co-processing of primary and secondary resources, as mining and recycling should not be seen as competitors.

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

After thanking our sponsors, 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 of Montana State University showed, by example of a spent gold heap leach, that a better understanding of the interactions between microbes and the local environment will allow improved design of in situ engineering configurations that stimulate microbial activities for more efficient metal recovery and subsequent site closure. Sabrina Hedrich, of the Federal Institute for Geosciences and Natural Resources, Germany, then discussed the abandoned Rammelsberg mine in Germany, an exploited ore deposit rich in zinc, lead, copper and silver, showing how it provides a potential habitat for microorganisms relevant in biomining.

Chiachi Hwang discusses the poster of Ioannis Vyrides
of Cyprus University of Technology
Prior to lunch, three papers dealt with various aspects of bioleaching. Currently more than 90% of the world’s copper is obtained through sulfide mineral processing. Among the copper sulfides, chalcopyrite is the most abundant and therefore economically more relevant, though averse to chemical leaching. Roberto Bobadilla-Fazzini of BioSigma S.A., Chile showed how Sulfobacillus thermosulfidooxidans strain Cutipay enhances chalcopyrite bioleaching under moderate thermophilic conditions in the presence of chloride ions. Yair Farber of the Israel Institute of Technology then discussed the bioleaching of silicate minerals by the soil bacterium Bacillus mucilaginosus under Fe-limited conditions.

Yair Farber (centre) with Dave Dew and Paul Norris (UK)

Arevik Vardanyan with Ioannis Vyrides
Arevik Vardanyan is our first ever delegate from Armenia and she presented the last paper of the morning, on behalf of the Institute of Microbiology, Armenia. The exceptional diversity of the ecogeographical conditions of Armenia and the richness of non-ferrous metals represent a great and valuable potential for investigation of the biodiversity of acidophilic chemolithotrophic bacteria as well as for isolation of new highly active strains and their communities. New acidophilic chemolithotrophic bacteria have been isolated from the Tandzut polymetallic ore of Armenia which are able to oxidize sulphur and its reduced compounds in the range of temperatures 20-400C. The isolated bacteria are able to oxidize copper concentrates only in association with Leptospirillum spp. bacteria.

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
The last paper of the day was presented by Fabian Giebner of the TU Bergakademie Freiberg, Germany who introduced three new methods to quantify biomass and activity of microbial leaching cultures.

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
Tuesday 10th June

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
The keynote provided a perfect curtain-raiser to a day of excellent presentations discussing innovations in biohydrometallurgy.

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
Finland is one of the largest gold producers in Europe. In Finnish ores, gold is often inside sulphide crystal lattices and requires pretreatment prior to cyanide leaching. Bio-oxidation is a pretreatment process that improves gold availability to cyanidation and thus results in economic and environmental savings in the overall process, as described by Sarita Ahoranta of Tampere University of Technology, Finland.

Lucy McTaminey with Amanda
Europe is increasingly looking at its own mineral reserves as a route to supply independence. However, given extensive historic mining activity, remaining ore deposits tend to be complex and low grade. Therefore, increasingly sophisticated processing options are required. Lucy McTaminey of Camborne School of Mines, UK described how a complex sulphide ore containing arsenopyrite in tight association with sphalerite was targeted. Fine grain chalcopyrite was disseminated within the sphalerite matrix, a condition known as chalcopyrite disease. Bioleaching tests were devised to test the ability to selectively leach the zinc at low temperature.

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
Following lunch, Paul Norris, of the University of Exeter, discussed the influence of anoxic conditions on mineral sulfide ore bioleaching, with emphasis on heap leaching, where excessive iron precipitation could affect the access of leaching solution to mineral surfaces and impact channelling.

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
An interesting day concluded with a paper from Nadja Gelhaar of TU Bergakademie Freiberg, Germany on the effect of different media-compositions on sphalerite bioleaching.

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 of the University of Liege, Belgium discussed the possibilities for Co(III) dissolution from a cobaltiferrous copper ore ore through simultaneous bioleaching of pyrite. A bacterial consortium involving three different acidophilic chemolithotrophs was adopted for the pyrite bioleaching and the concentration of ferrous iron was found to be a key factor for cobalt solubilisation.

Stoyan Gaydardzhiev (right) with Chris Bryan and Arevik Vardanyan
From 1942 to the ‘60s, oil was produced by pyrolysis of shale in Kvarntorp, Sweden. This generated some 40 million m3 of metal rich pyrolysed shale and discarded fines that were piled on site. Viktor Sjöberg of Örebro University, Sweden presented the results of a study focusing on a low cost heterotrophic leaching of vanadium, manganese, iron and molybdenum from the fines by addition of woodchips and steel slag in outdoor 1 m3 reactor systems at low liquid to solid ratio.

Viktor 2nd right at last nights Eden dinner with Clara Costa
and husband Joao and Ann Grandin
After the morning coffee break Patrick d'Hugues of BRGM, France discussed the co-processing of sulfidic mining wastes and metal-rich post-consumer wastes by biohydrometallurgy and Jarno Mäkinen, of VTT Technical Research Centre of Finnland, the effect of pre-treatment and parameters for bioleaching of printed circuit boards, important as a large amount of WEEE is generated nowadays, with only limited technologies available for recovering valuables from this waste.

Patrick D'Hugues (right) with Cecile Leycuras, Neilish Syna and Paul Norris
Two papers on the use of biotechnology in froth flotation took us to the lunch break. Previous work from the Pontifical Catholic University of Rio de Janeiro, Brazil has demonstrated the effectiveness of bacterial strains as flotation reagents on hematite beneficiation, and Mauricio Torem discussed the evaluation of Rhodococcus ruber as a biocollector, showing that, due to its high hydrophobic properties and fast bacterial growth, it is a potential bioreagent in the iron flotation industry.

Amir Nazari, of McGill University, Canada, then introduced work on the flotation of copper-loaded hydrophobic bovine serum albumin-coated bubbles. Copper adsorption was carried out using a novel technique where a stable colloidal system containing microscopic protein-coated bubbles (less than 10 microns) is dispersed through the aqueous solution, resulting in increasing both specific surface area and contact time between extractant and metal ions. Column flotation, a mature method used to float hydrophobic minerals, was then adopted to remove the microbubbles by means of attachment to the surface of larger air bubbles.

Jon with Amir Nazari and co-author Kristian Waters at Falmouth's Chain Locker

Three papers on the removal of arsenic from mine waters followed the lunch break, and brought the technical sessions to an end.

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) 
The finale to the conference was an excellent panel discussion on the future of biohydrometallurgy, chaired by MEI Consultants Patrick D'Hugues of BRGM France and Sue Harrison of University of Cape Town, with panellists Pieter Van Aswegen of PMet Consulting, South Africa, Paul Norris of University of Exeter, UK, and Jim Brierley of Brierley Consultancy, USA. This one hour session covered many important aspects of the future role of biohydrometallurgy, and these will be highlighted in future blog postings.
Panellists Paul, Jim and Pieter
This has been a superb conference with a fairly small but very distinguished audience from academia, research institutions and industry, with a wide range of different disciplines. Sue Harrison summarised the conference, which has covered innovative technologies and the challenges for existing processes, including important trends, such as expanding the range of minerals treated by biohydrometallurgy. The biotreatment of tailings and WEEE is also becoming more important, as are remediation and water issues. One of the great challenges is transferring scientific developments from academia into industry, concerns which have been expressed at other recent MEI Conferences. She also felt that in future conferences we must address not only technological, but also social issues.

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.