Hi-Tech Metals '18: conference diary

Hi-Tech Metals '18, the first in the planned series, got off to a very quiet start at Cape Town's Vineyard Hotel, with 31 delegates from 10 countries, 15 of the delegates having attended Process Mineralogy '18 earlier in the week. 

Vineyard Hotel, Cape Town

Processing of the Hi-Tech Metals is an area of crucial importance to society as a whole, and mineral processing will play a vital role, so we expect this conference series to evolve and grow in future years.
 

Thursday November 22nd

In recent years a number of expressions have been applied to describe a group of commodities that are considered essential ingredients for technology development and economic prosperity. In some publications, these are referred to as “high technology metals”, in others they are named “strategic” or even “critical raw materials“. To add confusion the actual composition of this this large and disjointed group of commodities is subject to ongoing change – depending largely on perspective, technology and material development, geostrategic positioning and market status.

Jens Gutzmer

In his opening keynote lecture, Jens Gutzmer, of Helmholtz Institute Freiberg for Resource Technology, Germany, attending his first MEI Conference, set the scene for the conference by addressing the reasons for the apparent confusion – and the inherent weakness of processes to identify “critical raw materials”. Furthermore, results of current efforts to quantify global resource potentials especially of by-product metals – many of which are regarded as “critical” - were discussed, as well as considering the role of recycling vs. primary production in the near- to mid-term supply of high technology metals.

 There is no doubt that recycling will be one of the great future challenges of minerals processing. With increasing trends in the production and consumption of technology devices and materials, the demand for metals including lithium, cobalt and rare earth elements are increasing exponentially.

It is now widely accepted that technology and metal-rich industrial waste represent significant secondary resources that must be harnessed to sustain the development of new technology materials. However, the recovery and re-use of the metals from these strategic wastes are still challenging. In particular, the solubilisation, separation and recovery in forms that are useful for manufacturing remain key areas that warrant further research.

Naomi Boxall, of CSIRO Land and Water, Australia, reviewed the recycling of technology-relevant metals from electronic, mining and industrial wastes, and opportunities and challenges associated with their re-use in the manufacture of new technology materials were identified. Naomi also discussed the extent to which the recovery and recycling of value from these wastes minimises the environmental impact associated with their production and disposal. Clearly, effective recycling of metals can help sustain the future of technology manufacturing.

However, as highlighted by Rudolf Stauber, of Fraunhofer ISC, Germany, the complexity of devices is high making recycling for technology metals complicated. Therefore the generation of concentrated fractions is an important step in the process chain of treating secondary raw materials. In addition there is an increasing demand for intelligent sorting solutions to meet the growing complexity and heterogeneity of material flows.

Rudolf focused on innovative recycling technologies for the recovery of critical raw materials from secondary resources by gas phase transport reactions, hydrogen processes and bioleaching. These recycling technologies can be adapted amongst others for rare earth based permanent magnets (REPM) and lithium-ion batteries. Hence in the field of magnets he highlighted the performance of recycled REPM produced out of scrap material for the application in electric motors. 

Rudolf Stauber and Naomi Boxall

Following the coffee break Philippe Giaro of Université de Liège, Belgium stressed that the characterization of e-waste is critical in ensuring an optimized recovery of “hi-tech” and critical elements. While this is a new problem that is focused on e-waste, it is an old problem relatively well understood in mining through process mineralogy. Characterization of metallic alloys and their associated textures (i.e. liberation, association) are all key metrics, which help provide a better understanding on the distribution and location of economical valuable element/metals, and thus opening opportunities for recovery process optimization.

Philippe presented a study on the first use of the Zeiss Mineralogic (and possibly Automated Quantitative Mineralogy) being deployed in e-waste characterization. This study outlines a new application area for automated mineralogy in e-waste characterization and how for effective recycling, there is a need for careful and robust material characterization.

The Nechalacho rare-earth element (REE) deposit is located in the Northwest Territories, Canada. The main rare-earth minerals (REM) in the deposit are zircon, allanite, bastnäsite, synchysite, monazite, columbite (Fe) and fergusonite; with quartz, feldspars and iron oxides accounting for most of the gangue. In the first of four presentations by Chris Marion, of McGill University, Canada, he showed how recent studies investigating the use of a Knelson Concentrator and a Multi Gravity Separator (MGS) have demonstrated that both centrifugal gravity techniques have the potential to produce a high-grade pre-concentrate. However, both techniques resulted in low recoveries. This study investigates multiple stages of centrifugal gravity separation, operating at more ideal conditions, to evaluate and compare the effectiveness of a Knelson Concentrator and a MGS for the beneficiation of the Nechalacho Deposit.  

Philippe Giaro and Chris Marion

Rare Earths were also the subject of the papers in the afternoon session. Nebeal Faris, of RMIT University, Australia) described how the beneficiation of ferruginous rare earth bearing ores, derived from lateritic deposits, by conventional mineral dressing processes is made difficult by the characteristics of the ore such as fine grain size, complex texture and similar physical characteristics between rare earth minerals and iron oxide gangue.

Nebeal showed how the removal of iron oxides would offer significant advantages with respect to downstream rare earth mineral processing. The purpose of the work presented was to demonstrate at bench scale the feasibility of magnetically separating iron oxides from a lateritic rare earth ore after the ore had been subjected to reduction roasting to convert weakly magnetic iron (III) oxides to magnetite. The target products from the test work were an upgraded rare earth feed and an iron concentrate suitable for further processing.  

The rare-earth elements are strategic metals and their growing economic and strategic importance, coupled with uncertainty in the global supply of REE from China, have led to concerns about the future supply of many of these metals. Due to these supply concerns and the increasing demand of REE, many new rare earth mineral deposits with novel mineralogy are being investigated. These deposits are often complex and contain multiple REMs for which there is limited processing knowledge.

Chris Marion of McGill University looked at expansion of the flotation knowledge base of various REMs through an improved understanding of their physico-chemical properties. The minerals investigated were bastnäsite, parasite, monazite, eudialyte, fergusonite and allanite. The study included zeta potential and microflotation studies using common rare-earth collectors (fatty acids and hydroximates), in the presence and absence of activating ions (cobalt and lead) and depressants (citric acid and biopolymers). 

Anthony Geneyton, of Université de Lorraine, France, discussed a study to develop a new approach using a lanthanum chloride and carboxylate collector combination with the aim of improving the selective and effective collector adsorption onto the rare-earth phosphate minerals. Bubble/particle adhesion tests with sodium oleate collector were performed indicating a higher mineral surface hydrophobicity when using lanthanum chloride. Flotation experiments were performed with sodium oleate showing enhanced monazite recovery and flotation rate in presence of lanthanum chloride. The best flotation performance was obtained when the lanthanum chloride was added prior to the collector.

With regards to the performed XPS study and the literature data, Anthony suggested that lanthanum ions or lanthanum species strongly interact with the under-coordinated phosphate groups on the monazite surface playing a role of a bridge between the monazite surface and the carboxylate group of the collector. The workers observed that the lanthanum chloride dosage and mode of addition must be strictly controlled to avoid a decrease of the availability of the collector and thus a decrease of the monazite recovery and flotation rate. It was shown that the addition of non-ionic reagents significantly enhanced the adsorption of the collector and thus the rare earth recovery under conditions where the presence of cations limit the natural collector adsorption. 

Nebeal Faris and Anthony Geneyton

According to Levie Bumhira, of Stellenbosch University, South Africa, recovery of rare earth elements from secondary resources such as end-of-life fluorescent lamps will play an increasingly important role in the REEs market. Recycling of REEs from fluorescent powders often focuses on the recovery of Y and Eu, which have high value and are easily recovered. However, the recovery of other REEs present in more stable phosphor powders (e.g. Ce and Tb) should also be considered.

Levie discussed a project aimed at evaluating a multiple stage leaching process for REE recovery from phosphor powders by investigating the effects of temperature, acid concentration and material pre-treatment on leaching behaviour. First stage leaching with H2SO4 resulted in 98 % yttrium and 91 % europium dissolution, but insignificant terbium and cerium leaching. Following alkali fusion of the first stage residue, Tb and Ce recoveries exceeding 95 % were achieved in the second HCl leaching stage. The precipitation of Ca species impacted REE leaching efficiency.    

Levie Bumhira with Stellenbosch colleague Bruce Musariri
and University of Coventry's John Graves

A very good first day ended with a sundowner in the hotel gardens.

 

More on day 1 on the posting of November 22nd.

 

Friday November 23rd

Lithium was the focus of the 6 papers presented in the morning session. Lithium is a strategic metal due to its high-tech usages, mostly for batteries in electrical vehicles, but it also has a high supply risk. Due to high market prices, several resources are under (re)evaluation.

Reiner Neumann, of CETEM, Brazil, presented a case study on a pre-concentrate from the Argemela deposit in northern Portugal, which has an overall grade of 4.1% Li2O, the carrier being montebrasite. The ore grades around 40% of the mineral, and the main gangue phases are quartz (also around 40%) and muscovite. Several other phosphates are associated with montebrasite, planerite and childrenite predominating. This challenges the hydrometallurgical extraction of lithium from the concentrate.

Reiner showed how an initial sulphuric roasting step was optimized by TGA at 800°C, above the dehydroxilation of planerite (340°C) and decomposition of montebrasite (740°C) temperatures. Over 95% of the lithium was extracted with water at room temperature, and the residue, dominated by quartz and berlinite, has less than 0.5% Li2O. Al and Fe are then precipitated as hydroxides by lowering the pH, and after filtering them out any Mg is precipitated by raising the pH to 12. The final lithium carbonate is precipitated by reacting with Na2CO3, at neutral pH. 

Lev Filippov, of Université de Lorraine, France, also presented a case study on a Portugese ore, the Gonçalo lithium bearing mica rich pegmatite ore, on which mineralogical analysis indicated that lepidolite occurs in coarse grained textures, which allows a noticeable liberation of gangue minerals from the fine grained lepidolite intergrowths with quartz, K feldspar and albite, making full liberation difficult to attain.

Taking advantage of the coarser gangue liberation, image analysis was used to predict grade histograms of different size fractions, simulated by a developed random comminution algorithm. These histograms were used to simulate different pre-concentration scenarios at crushing sizes using optical sorting, allowing a Li pre-concentrate to be produced. A scaled approach of grinding and sieving produced a lepidolite rich fraction >210 µm which was processed using a Corona electrostatic separator to obtain a Li pre-concentrate assaying 3.5 % Li2O from a feed grade containing 1.8 % Li2O. Flotation testwork performed with the fine size fraction (-210+63 µm),  showed that lepidolite flotation is optimized between pH 3 and 5, where concentrates assaying 4.2-4.5 % Li2O corresponding to 87-95% Li recovery were attained at the rougher stage.  

Reiner Neumann and Lev Filippov

Traditionally, lithium has been obtained from brines, however, the expected increase in demand will require new hard rock deposits to be found and exploited. The main mineral containing lithium in pegmatite hard rock deposits is spodumene. There is relatively little recent work that has been published on the flotation of spodumene, which is an issue at a time where lithium supply security has become a top priority for technology companies. To develop an improved fundamental understanding of spodumene flotation, its zeta potential and microflotation behaviour in the presence and absence of different flotation reagents were studied at McGill University, Canada, and presented by Chris Marion. The reagents tested were sodium oleate, octyl hydroxamate and dodecylamine. Chris compared the results obtained for spodumene with that of common gangue minerals.

Keliber Ltd. is a Finnish SME aiming at production of battery-grade lithium carbonate using a novel leaching process and utilizing the company’s own spodumene ores as the raw material. The process chain, starting with mining and ending with the production of high-quality lithium carbonate is multi-staged and complicated. Pekka Tanskanen, of Keliber,  presented the main process stages and underlined certain points critical for lithium recovery and the quality of the final product. 

As the lithium ion battery (LiB) market is growing rapidly, LiB wastes will increase in the future and LiB components such as Co, Li, but also graphite, are forecast to be critical materials. These critical materials are contained in the black mass produced by LiBs recycling.

Anna Vanderbruggen, of Helmholtz Institute Freiberg for Resource Technology, Germany, presented original research focused on graphite beneficiation from cathode lithium metal oxides by flotation. Detailed characterization of the pyrolyzed black mass (inculding MLA, XRF and XRD) showed that the graphite particles are fully liberated from the copper foils. Batch flotation showed that pretreatment, such as attritioning, improves process efficiency while preserving the shape of spheriodized graphite. Concentrate impurities mainly comprise fine particles from cathode active materials, which can be removed with desliming and flotation cleaner stages. Anna felt that this research is expected to bring about an innovative and useful process for the recycling industry. 

Pekka Tanskanen and Anna Vanderbruggen

Bruce Musariri, of Stellenbosch University, South Africa, also discussed the importance of recycling LiBs. Current hydrometallurgical metal recycling processes involve dismantling and size reduction followed by leaching with mineral acids; these lixiviants present environmental challenges of their own.

Bruce described a project to evaluate the technical feasibility of using organic acids, which potentially have a smaller environmental impact than mineral acids, as lixiviants to recover lithium, cobalt and nickel from LiBs. Batch atmospheric leaching tests were performed with citric acid and DL-malic acid to investigate the effect of acid concentration, leaching temperature and H2O2 addition on metal leaching. Leaching with 1-1.5 M citric acid and 2 volume % H2O2 at 95°C achieved more than 95 % Co and Li dissolution; these results suggest that organic acids can possibly substitute inorganic acids as environmentally friendly lixiviants.

Significant cobalt mineralization associated with known Paleoproterozoic gold has recently been discovered at the Palokas Prospect in Northern Finland. This discovery has the potential to contribute significantly to the supply of cobalt for current battery technologies. The rocks are petrologically challenging because of their complex metamorphic and structural history, and in the first paper of the afternoon session, Pieter Botha, of Hippo Geoscience, Australia, described the development of analytical workflows based on the integration of multi-scale, multi-modal, and multi-dimensional technologies.

In this way it was possible to establish: 1) the general nature of the mineralogy and rock microstructure; 2) specific details on the texture of the ore mineralisation, including its relationship to structural deformation events; and 3) the deportment of commercially important elements. The benefits of this workflow include the ability to upscale micro-scale observations for informing further exploration work, and early-stage predictive geometallurgical models.

Pieter Botha (right) with his co-author Alan Butcher

“Theisenschlamm”, a flue dust of former copper shale processing in Germany, was deposited between 1978 and 1990. Its complex composition comprises high amounts of zinc and lead as well as a variety of low concentrated high-tech metals, such as rhenium, molybdenum, cobalt and germanium, which brought processing of this material back into focus. Since the Theisenschlamm is very fine-grained, it is well suited for hydrometallurgical processing. However, the concentrations of the high-tech metals in the pregnant leach solution are very low (1-10 mg/L). Toni Helbig, of Helmholtz Institute Freiberg for Resource Technology, Germany, described the development of a process route which includes an innovative combination of membrane filtration and solvent extraction in order to achieve selective recovery as well as enrichment of the target elements.

Rhenium is a valuable and extremely rare chemical element with unique chemical properties.  It is extracted commercially as a by-product from the processing of molybdenite associated with porphyry copper ores.  There is a present interest in recovering rhenium from copper pregnant leach solutions (PLS) produced by copper heap and stockpile leaching.  These solutions contain rhenium at very dilute concentrations, typically in the 1 mg/L concentration range.  Brent Hiskey, of the University of Arizona, USA, described laboratory column ion exchange experiments to extract rhenium from these solutions using weakly basic anion exchange resins and actual plant PLS from two operating mines.  The dynamic loading and elution behaviour of Re on Purolite® A170 and A172 was discussed. 

Brent Hiskey and Toni Helbig

Niobium, an important alloying element in steels, is primarily produced from three mines in the world: the Catalão and Araxá mines in Brazil and the Niobec mine in Canada. While current production rates are sufficient to meet global demand, concerns in the supply of niobium exist due to the geographic concentration of production. This has led to the development of many new deposits around the world, however, there is little information regarding niobium mineral beneficiation processes. While flotation is generally accepted as the most promising technique for the recovery of niobium-bearing minerals, such as pyrochlore and columbite, there is limited research detailing fundamental aspects of the process.

In the last of his four presentations, and the final paper of the conference, Chris Marion, of McGill University, described a study examinings the physico-chemical properties of pyrochlore and columbite through zeta potential and microflotation experiments. Common collectors used in niobium mineral flotation (hydroximates, fatty acids, and amines) were studied in the presence and absence of activating ions (cobalt and lead) and depressants (oxalic acid and citric acid). The results were compared to those from dolomite (a common gangue mineral). 

After summarising the conference, Amanda invited everyone for a final sundowner in the Vineyard gardens. 

We look forward to running this conference again in two years time. Although having a slow start we are confident that the series will evolve and grow, as we believe strongly that this is an area where mineral processing will contribute a crucial role in our hi-tech future.

The Proceedings of the conference are available on USB, and all authors have been invited to submit their final papers for peer-review, with a view to publication in a Virtual Special Issue of Minerals Engineering.

Photos taken at the conference can be accessed here.

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