Sustainable Minerals '18 Conference Diary

Sustainable Minerals ’18 immediately followed Biohydromet ’18 at the Windhoek Country Club, Namibia, and was MEI’s 5th in the series. The conference was organised in collaboration with the Namibia University of Science & Technology, and was sponsored by Zeiss and Outotec, with International Mining as a media partner, and CEEC as the Industry Advocate. As always, our consultant for the event was Prof. Markus Reuter, the Director of the Helmholtz Institute Freiberg for Resource Technology.

Windhoek Country Club

Thursday 14th June

This morning I welcomed the 55 delegates from 13 countries to the conference, although we had met many of them last night at the conference dinner which was held at the end of the Biohydromet conference (posting of 14th June).

Prior to getting the conference underway we observed a minute's silence in remembrance of Prof. Dee Bradshaw (posting of June 8th), a former MEI Conferences consultant, who was a great advocate of sustainable minerals and green mining, and who would surely have been at this event.

Rob Dunne

After I highlighted the crucial role that mineral processing has in sustainability (posting of June 15th) the conference got under way with a very appropriate keynote lecture from Rob Dunne, who is an Adjunct Professor at Curtin University, and the University Of Queensland, Australia. Rob’s lecture “Water- crisis, conflict, resolution (?)”, is detailed in the posting of 24th April 2017, and set the scene for two more important presentations on water which took us up to the coffee break.

Bruno Michaux, of Helmholtz Institute Freiberg for Resource Technology, Germany, discussed the potential of mineral processing simulators as a tool for water-saving strategies in the mining industry. As the mining industry is facing an increasing number of issues related to its fresh water consumption, water-saving strategies are progressively being implemented in the mineral processing plants, often leading to variations in the process water chemistry. However, the impact of water chemistry variations on the process performance is rarely known beforehand, thus creating an obstacle to the implementation of those water-saving strategies. To tackle this problem, a simulation-based approach was suggested, which relies on the modification of the flotation kinetics under varying water chemistries. This approach was illustrated with the case of a fluorite ore and compared to the more traditional approach, which consists in determining the shift in the grade – recovery curve when the process water is subject to change.

Bruno Michaux (left) with Edison Charikinya, Nicole Uys, and Jochen Petersen

Päivi Kinnunen, of VTT, Finland, introduced the European Union-funded ITERAMS project (Integrated mineral technologies for more sustainable raw material supply), which delivers new solutions to enable closed water loops in the mining operations. The isolation of process waters completely from the adjacent water systems requires development of new methods for optimising and controlling water qualities at each process step. As a bonus, this will also facilitate the recovery of additional valuable constituents. The tightly closed water cycles can be realised only if the tailings can be filtered and stacked dry. Tailings streams are modified for their easier geopolymerisation. Geopolymerisation is used to create water and oxygen tight covers on the deposited tailings. The main objective is to obtain a new paradigm proof of concept at mine sites to recycle water and valorise tailings for an improved environmental and economic result.

Päivi Kinnunen with Jennifer Broadhurst



Poster viewing during the long coffee break

Amanda with some of the excellent Country Club staff

Groundwater quality reflects the various bio- and geo-chemical interactions between the organic and inorganic matter within aqueous sediments and associated secondary water sources, impacting on the quality and speciation of the concomitant aquifer. In the case of pyrite (FeS2)-rich sediment and acid mine drainage, the oxidation in the oxic zone and the resulting acidic leachate affect the water quality. Heavy or toxic metals bearing minerals undergo leaching and redox reactions which may lead to the release of the toxic species into the porewater, with adverse consequence of chemical pollution of the environment. Jonas Addai-Mensah, of the Namibia University of Science & Technology, described a study which examined the impact of pyrite-rite sediment redox process on the quality of porewater along the sediment depth column, and on the water quality transformation of external water bodies that are in association with the pyrite-rich sediment. The implications of the findings in relationship to environmental remediation principles and sustainable development and use of land were discussed.

With Jonas Addai-Mensah and his NUST colleague Harmony Musiyarira

Sue Harrison

The co-disposal of waste rock with fine desulfurised tailings can potentially aid in the prevention of acid rock drainage (ARD) by restricting the access of oxidants to sulfide bearing rock surfaces. However, in prevention studies, optimising the packing density of waste rock dumps remains a challenge. Large void spaces between particles are prevalent. This low degree of interlocking between particles reduces the packing strength and amplifies seepage. High seepage rates contribute to oxidative weathering of the sulfide bearing rocks. A standard protocol for material placement, to enhance the packing density of these beds, is therefore paramount for the success of these co-disposal prevention methods. Conference consultant Sue Harrison, of the University of Cape Town, showed how particle packing models are exploited to obtain optimum packed beds. These packing models are evaluated by applying incremental loads to the ore beds. The pack strength of these beds is then assessed at various loads using stress-strain correlations. This study forms the basis for the development of optimised packing models for the prevention of ARD at both bench-scale and field application.

ARD mobilises deleterious elements, increasing environmental burden for mining sector and local communities. In a further presentation by Sue Harrison, she discussed why characterisation of ARD potential of waste rock is necessary to inform their appropriate disposal in order to minimize the pollution risks. This characterisation has been typically limited to static tests using strong acid and oxidative leaching to give worst case net acid forming potential scenarios. Where ARD is considered important, long-term kinetic tests determine the rate of the net acid generation under field conditions. However, the relative kinetics of acid neutralisation and generation are not taken into account. More recently, approaches to refine ARD characterisation and prediction are being sought. The UCT biokinetic test is one of a suite of tests informing this characterisation.

In the final paper of the morning Chris Bryan, formerly with Camborne School of Mines, UK, and now with BRGM, France, and also a conference consultant, discussed the analysis of sulfidic coal production wastes using biokinetic tests combined with QEMSCAN. 

Chris Bryan (centre), with Megan Barnett and Simon Gregory of the British Geological Survey

Our two representatives from Rossing Uranium, Ignatius Shaduka and Jacklyn Mwenze

It is good to have the Dundee Precious Metals (DPM) smelter so well represented at the conference. The smelter is located near the town of Tsumeb, north-east Namibia, and has been in operation since 1963. It has been designed and build specifically to treat complex polymetallic concentrates from Tsumeb Mine, which contains high levels of copper, lead, zinc, arsenic and cadmium. An Ausmelt furnace was commissioned to treat lead concentrates in 1996 and then conversed to treat copper concentrate in 2008, when Namibian copper mines closed. Tsumeb smelter was acquired by DPM in 2010 and feed from DPM’s Chelopech mine was provided. Since the acquisition, significant investments have been made to transform the smelter to a sustainable toll-treatment facility with specific focus on improving occupational, health, safety and environmental aspects of the operation. This includes new off-gas and emissions management, new dust management system, new oxygen plant, new hazardous waste deposition facility, two new Peirce-Smith converters and new sulphuric acid plant. Barcelona Tsauses discussed how DPM is focused on empowering local people wherever it operates. Community investment in Tsumeb include small and medium enterprise development projects, education, social services and culture. Commitment to meaningful stakeholder dialogue and engagement has been the approach followed by the company. 

Barcelona Tsauses (right) with her DPM colleagues, Lawrence Tjatindi,
Zebra Kasete and Buks Kruger

The mining and minerals industry faces some of the most difficult sustainability challenges of any industrial sector. To secure its continued ‘social licence’ to operate, the industry must respond to these challenges by engaging its many different stakeholders and addressing their sustainability concerns. Many mining companies, particularly multi-nationals, are reporting the outcomes of their sustainability performance in publicly available annual reports, using integrated frameworks developed under the auspices of the responsible mining initiatives. However, the proliferation of standards and the voluntary nature of the reporting results in reporting inconsistencies both in terms of data presented (quantity and quality) and terminologies used. David Viljoen, of the University of Cape Town, discussed the application and applicability of existing sustainable performance assessment frameworks and metrics in the context of the South African gold mining industry. He reviewed and evaluated current sustainable performance reporting practices in the industry, assessing their effectiveness in promoting the sharing of information, critical to strengthening transparency and accountability.

David Viljoen (right) with Rodrigo de Almeida Silva

Low concentrated heavy metal ions are causing diverse problems for conventional metal processing, and Robert Braun, of Helmholtz Institute Freiberg for Resource Technology, Germany, discussed new biosorbents for metal recovery. Artificial peptides with metal binding affinities combine high specificity and sensitivity and being biodegradable, they do not add additional environmental pressure, therefore they are of high potential for geobiotechnology. Robert described the development of novel peptidic bio-materials for the recovery of cobalt and nickel.  

Robert Braun (left) with Guillermo Luque Consuegra, Megan Barnett and Simon Gregory

In a further paper from the Helmholtz Institute Freiberg for Resource Technology, Rohan Jain discussed the cost-competitiveness of siderophores in recovering of critical metals from waste streams. Siderophores are known for their specificity and sensitivity towards the critical metals whose supply is at risk in the future. Thus, the use of these siderophores for the recovery of these critical metals from their low concentrated wastewater is a very attractive option. However, there is no detailed cost estimation for their application in wastewater. This study detailed the economic feasibility of application of desferrioxamines for the recovery of gallium from industrial wastewater, factors such as regeneration recycles, downstream processing, cost of gallium, operational cost of the technology and cost and grade of desferrioxamine production being taken into account.

Rohan Jain (centre) with Pankaj Kumar Choubey and Rodrigo de Almeida Silva

Refractory gold ores have been the subject of numerous investigations in order to improve the leaching kinetics. This is because the cyanidation process cycle, although well established and well researched, remains very long.  Faster kinetics would help lower the production cost which is very necessary especially during lean and tough industry times. Jean Jacques Mabayo, of University of the Witwatersrand, South Africa, introduced the development and application of a new and promising reactor “Jetleach reactor” in improving the leaching kinetics of refractory ores. The Jetleach reactor is designed to create and propagate micro-cavitation by impacting two pulp streams against one another at a high velocity. The impact is expected to lead to some comminution of the solid particle in the pulp which further results in exposure of the ore to the lixiviant, permitting an enhanced attack on the ore in the pulp and thus improving the reaction kinetics.

Mauricio Torem

Excess boron in drinking and irrigation water is a serious environment and health problem because it can be toxic to many crops and lead to various human and animal diseases with long-term consumption. Mauricio Torem, of PUC-Rio, Brazil, showed how the removal of boron from aqueous solution was carried out by electrocoagulation using aluminum electrodes as anode and cathode.

Sylvi Schrader

Siderophores are biomolecules, which can form strong complexes with different metals. They are produced by microorganisms and a biotechnological production of these chelators offers an application in different processing methods. Particularly amphiphilic siderophores are very interesting for the froth flotation process, as discussed by Sylvi Schrader, of Helmholtz Institute Freiberg for Resource Technology, Germany in the final paper of the day. The hydrophilic part, carrying hydroxamate groups, is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully and Sylvi suggested that siderophores carrying the same functional groups also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, contacts the bubbles and avoids additional chemicals and further working steps for making the target mineral particles hydrophobic.

The Windhoek Country Club Golf Club provided the setting for the evening sundowner:

Friday 15th June

Yiannis Pontikes

The second day began with a keynote lecture from Yiannis Pontikes, of KU Leuven, Belgium) who discussed the conversion of iron-rich residues from metallurgical processes into novel materials. A number of hydro- and pyro-metallurgical processes lead also to Fe-rich residues that find limited applications; notable uses are in the raw meal for cement production, as aggregate in concrete, as abrasive blasting grit, and as media in geotechnical and road pavement applications. Yiannis described an alternative process, where the Fe-rich residue is used as raw material in the synthesis of inorganic polymers. These materials show properties comparable to Portland cement while having a smaller environmental footprint. 

The progressive development of new technologies increases the demand for raw materials. But primary resources are finite and mining has to be constantly optimized in order to extract raw materials from larger depths, costs rise and recycling becomes attractive. Recycling of metal-containing waste is currently performed only to a limited extent and huge amounts of potential recyclables fall into oblivion. Conventional recycling strategies based on pyrometallurgical or hydrometallurgical processes are often costly due to high energy requirements and usage of chemicals. As discussed by Rudolf Stauber, of Fraunhofer ISC, Germany, bioleaching offers a green recycling strategy, where leaching of waste material is performed by microorganisms. In this study the recycling potential of end-of life magnets was investigated by means of bioleaching with various bacteria. The highest leaching efficiencies were achieved with bacteria of the ferrooxidans species.  

Rudolf Stauber (right) with Markus Reuter



Zaynab Sadan , of the University of Cape Town, also highlighted that electronic waste is one of the fastest growing waste streams in the world and Africa is no exception. Although generally classified as hazardous waste, e-waste streams contain a diversity of materials which include metals, plastics, glass among other chemical substances. With the appropriate technology, these materials can be gainfully recovered while minimising the otherwise adverse damage that irresponsible disposal or recycling would have on humans and the environment. In the African context, recycling of e-waste presents an opportunity to develop an industry that can allow for the upskilling of the otherwise largely unskilled labour force currently employed in this industry, minimise the diverting to landfills of resource-rich waste streams and promotes the development of a secondary resource economy which is a driving force for sustainable resource management. Jochen presented a review of the current status of the e-waste recycling industry in Africa and how it aligns with sustainable resource management practices. 



Naomi Boxall

Naomi Boxall, of CSIRO Land and Water, Australia, described how Australia is at a crossroads in the management of lithium ion battery (LIB) wastes. In Australia, LIB are not classified as hazardous, despite having significant human and environmental health risks if handled and disposed of incorrectly. Unlike in Europe and Asia, there are no regulations or polices to enforce or encourage product stewardship in Australia, with the majority of small recycling schemes targeting the behaviour of the consumer, and voluntary actions of manufacturers and distributors. Although the manual sorting and dismantling of LIB waste occurs onshore, the valuable components are sent overseas for further processing, because of the limited capacity to recover the inherent metal values. Naomi reviewed the state of play for LIB recycling, considering the projections of LIB waste generation, identification of future trends, opportunities and potential for innovation for LIB recycling in Australia.

While the many definitions of a circular economy (CE) elegantly highlight its many dimensions, ultimately to fully understand the economic viability of the CE, as would be the case for any economically viable processing system, a deep understanding of all the losses, environmental impact and associated risks from the system must be understood and quantified economically, said Markus Reuter, of Helmholtz Institute for Resource Technology, Germany.  A meaningful analysis of the CE can only be made if a detailed understanding is available of the distribution of all metals and materials through the system. Above all, all required fundamental thermodynamic data and physical properties must be available for this analysis so that a simulation basis can be applied to perform this analysis and economic optimization of the complete system – from product design through recycling to final metal, material and energy recovery. This provides a more realistic process engineering analysis of the performance of the significant actors in the CE system. With the objective to improve material recovery and resource efficiency in the electronics sector, it will require brands, manufacturers and recyclers to take a product-centred approach to understand the complete lifecycle, where the inefficiencies occur in the system and which frameworks can offer solutions. To take the first step in this direction, Fairphone is starting by examining the end-of-life phase of its latest smartphone (Fairphone 2) by applying HSC Sim simulation software from Outotec to understand the phone’s recyclability, system environmental footprint, energy recovery as well as exergetic efficiency. Markus discussed these aspects, and there is more on the posting of 19th February.

Edson Charikinya

South Africa is one of the world’s major suppliers of Platinum Group Metals (PGMs). The PGMs are hosted in the Bushveld Complex, which includes three distinct mineral-bearing reefs: the Merensky Reef, the UG2 Reef and Platreef. The ores from the different reefs are processed through a number of stages that include concentration, smelting and refining to produce PGMs and base metal byproducts.  Edson Charikinya, of the University of Cape Town, described the work undertaken to develop Life Cycle Inventory (LCI) datasets, related to the production of PGMs in South Africa. A new modelling approach which aims to provide LCI metal datasets that have the highest possible degree of modularity was used. In this approach the primary production of PGMs was modelled by linking together datasets that represent different processing stages. Challenges encountered in implementing this new modelling approach were described, along with results of LCI datasets as built primarily from published company reports complemented by mass balance modelling.

Markus Reuter presented a simulation-based methodology to calculate the cost of recycling and waste treatment. Unlike conventional analysis, this methodology uses the Second Law of Thermodynamics to introduce the entropy concept to the analysis, so the quality of the flows of the system is also considered. The methodology was tested in a copper production process. The simulated process starts with a copper ore and a concentration plant through flotation. Then, copper cathodes are produced through the pyrometallurgical route of copper. As several residues are produced, i.e. dust, slags or off-gas, a sulfur capture plant and a gold refining stage is linked to the flowsheet. Once the process has been simulated with HSC Chemistry, a thermoeconomic analysis is conducted. Therefore, the cost of the copper production itself and including the sulfur capture and gold recovery is obtained.

Corby Anderson, of the Colorado School of Mines, USA, was scheduled to present the final paper of the morning, but unfortunately United Airlines had left him stranded in Washington. His paper, describing a novel process that has been developed for the dezincing of galvanized steel, can be found in the conference Proceedings.

Corby's absence allowed us to take a very long leisurely lunch and enjoy the fine food in the hotel restaurant.

As discussed by UCT’s Sue Harrison, appropriate handling and disposal of coal waste is key to maximize the sustainability performance in coal processing activities. Fine particulate material comprising the desulfurized fraction of fine coal ‘waste’ streams from a two-stage flotation process was considered as the substratum for manufacture of fabricated soils, with potential for use as top soil in the rehabilitation of mine sites.  Coal waste and native soil from the Middelburg area in South Africa were used as the main substratum. Compost, anaerobic digested sludge and microalgae were added as organic matter and nutrient source. Malt residue from a micro brewing process were used as physical ameliorant. In order to validate the potential of the fabricated soils, germination and growth of the grass Eragrotis Teff indigenous to the Mpumalanga region was investigated. The germination and growth experiments showed the soil mixtures amended with malt residue gave a better response in terms of final biomass production. According this study, the use of these soil substitutes could reduce the amount of top soil used in land restoration by up to 75%. This use would significantly reduce the land-use footprint and the social and environmental impact of mining activities, thus promoting the circular economy zero-waste strategy. 

Desulphurization must be considered as an interesting approach to reclaim abandoned mines along with the recovery of valuable elements. Indeed, desulphurization produces sulfide-lean tailings, used as a mine cover, and sulfide-rich concentrate, which can contain gold associated with sulfides. Because of the weathering of old tailings, layers of oxidation products are formed on the surface of these minerals. This surface oxidation reduces sulfide hydrophobicity and consequently flotation efficiency. Ahlem Skandrani, of Université du Québec en Abitibi-Témiscamingue, Canada, described a study whose main goal was the establishment of mechanical pre-treatments of old tailings that will facilitate flotation, to ultimately produce a final desulphurized tailings and a sulfide concentrate with gold recovery. Results show that it is possible to produce a concentrate rich in sulphide and gold. Mineralogical characterization also confirms mechanical pre-treatment selection and efficiency by removing oxidation products at the particles surfaces.

Ahlem Skandrani with Zaynab Sadan

Cristina Vila

Cristina Vila, of University of Porto, Portugal, described work aimed at the recovery of valuable metals through reprocessing of abandoned mine waste deposits. Cabeço do Pião site, an old tailings dam whose property was transferred from Panasqueira Mine to the Municipality of Fundão in Portugal was used as a case study. The material deposited in the dam constitutes an imminent risk to the environment, in particular to Zézere’s river that flows close to the bottom of the tailings pile and is the main contributor for drinking water supply to the city of Lisbon. Multivariate analysis of chemical data allowed the establishment of mineralogical associations, proving to be a useful planning tool in a future selective re-mining of the tailings pile.

Aino-Maija Lakaniemi

Aino-Maija Lakaniemi, of Tampere University of Technology, Finland, showed how removal and recovery of uranium(VI) from synthetic wastewaters was studied using waste digested activated sludge (WDAS) in its native form i.e. without drying/dewatering. Batch adsorption experiments showed that WDAS can adsorb 200 (± 9.0) mg of uranium per g of WDAS. Desorption of more than 95% of uranium from WDAS was successful with both acidic (0.5 M HCl) and alkaline (1.0 M Na2CO3) eluents, such that the desorbed uranium solution could, in principle, be fed to the uranium ore processing infrastructure.

 To fully understand the limits of the Circular Economy (CE), a comprehensive model taking into account its different stages (product design, mechanical pre-processing, metallurgy, etc.) is required. A crucial aspect is to understand the inevitable losses at different stages of recycling. The complexity of the material streams in mechanical separation processes requires a detailed description of particles and their properties to successfully simulate unit processes. In the final paper of the conference, Juho Hannula, of Helmholtz Institute Freiberg for Resource Technology, Germany, presented a new approach that connects measurement-based particle properties to statistical modelling and simulation of mechanical separation processes. The proposed approach combines particle tracking with the generalization ability of neural networks. In order to demonstrate the new approach, Juho showed how Mineral Liberation Analysis data from magnetic and gravity separation processes of a complex ore was used. The applicability of the proposed approach to modelling and simulation of mechanical recycling processes was also discussed.

Juho Hannula (centre) with Rob Dunne and Rudolf Stauber

Our consultant, Markus Reuter, presented a short summary of the conference, after which MEI's Amanda Wills invited everyone to the next in the series, which will be held in Falmouth, UK, in June 2020.

One of our regular contributors described the series as unmissable events, due not only to the very topical presentations, but also to the 'family atmosphere' engendered by the long breaks, the lack of parallel sessions, and informal social events, such as the final farewell sundowner held by the side of the hotel pool (posting of 16th June).

The draft papers are available on USB from MEI, and authors have been invited to submit final papers for peer review for the virtual special issue of Minerals Engineering.
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