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Recycling of Electronic Scrap at Umicore. Precious Metals Refining


Abstract and Figures

With the new legislation for Waste Electrical and Electronic Equipment (WEEE) coming up in Europe a substantial increase of end-of-life electronic equipment to be treated will take place. In this context, often much attention is placed on logistical issues, dismantling and shredding/pre-processing of electronic-scrap, whereas the final, physical metals recovery step in a smelter is often just taken for granted. However, a state-of-the-art smelter and refinery process has a major impact on recycling efficiency, in terms of elements and value that are recovered as well as in terms of toxic control and overall environmental performance. Umicore has recently completed major investments at its Hoboken plant, where besides precious metals and copper a large variety of base and special metals are recovered. Equipped with state-of the art off-gas and waste water purification installations, the plant has been developed to the globally most advanced full-scale processor of various precious metals containing secondary materials such as automotive catalysts and electronic-scrap, generating optimum metal yields at increased productivity. To utilise this potential to its full extend for WEEE fractions like circuit boards or mobile phones, especially the interface between pre-processing (shredding/sorting) and smelting/refining is of importance. Here, a mutual optimization of sorting depth as well as of destination of the various fractions produced can lead to a substantial increase in overall yields, especially for precious and special metals.
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Recycling of Electronic Scrap
Waste - Secondary Raw Materials III, Strbske Pleso, June 2006 1
Recycling of Electronic Scrap at Umicore Precious Metals Refining
Dr. Christian Hagelüken
Umicore Precious Metals Refining
A. Greinerstraat 14
B-2660 Hoboken, Belgium
With the new legislation for Waste Electrical and Electronic Equipment (WEEE) coming up in Europe a sub-
stantial increase of end-of-life electronic equipment to be treated will take place. In this context, often much
attention is placed on logistical issues, dismantling and shredding/pre-processing of electronic-scrap,
whereas the final, physical metals recovery step in a smelter is often just taken for granted.
However, a state-of-the-art smelter and refinery process has a major impact on recycling efficiency, in terms
of elements and value that are recovered as well as in terms of toxic control and overall environmental per-
formance. Umicore has recently completed major investments at its Hoboken plant, where besides precious
metals and copper a large variety of base and special metals are recovered. Equipped with state-of the art
off-gas and waste water purification installations, the plant has been developed to the globally most ad-
vanced full-scale processor of various precious metals containing secondary materials such as automotive
catalysts and electronic-scrap, generating optimum metal yields at increased productivity. To utilise this po-
tential to its full extend for WEEE fractions like circuit boards or mobile phones, especially the interface be-
tween pre-processing (shredding/sorting) and smelting/refining is of importance. Here, a mutual optimisation
of sorting depth as well as of destination of the various fractions produced can lead to a substantial increase
in overall yields, especially for precious and special metals.
1 Introduction
Umicore is a speciality materials group. Its activities are centred on four business areas: Precious Metals
Services, Precious Metals Products and Catalysts, Advanced Materials and Zinc Specialities. Each business
area is divided into market-focused business units. The company focuses on application areas where its
experience in materials science, chemistry and metallurgy can make a real difference. The Umicore Group
has industrial operations on all continents and serves a global customer base; it generated a turnover of
EUR 6.6 billion in 2005 and currently employs some 14,000 people. In 2003 Umicore took over the former
Degussa precious metals activities.
The business unit Umicore Precious Metals Refining operates at Hoboken near Antwerp, Belgium, an inte-
grated metals smelter and refinery, which recovers and sells a wide range of metals from complex precious
metals bearing materials: gold, silver and the platinum group metals (PGMs: palladium, platinum, rhodium,
iridium, ruthenium), special metals (selenium, tellurium, indium), secondary metals (antimony, tin, arsenic,
bismuth) and base metals (copper, lead, nickel). Other by-products of the plant are sulphuric acid (from
offgas-purification) and a depleted slag, which is used as construction material and in the concrete industry.
Important feed materials are various industrial wastes and by-products from other non-ferrous industries
(e.g. drosses, mattes, speiss, anode slimes), precious metals sweeps & bullions, spent industrial catalysts,
as well as consumer recyclables such as car exhaust catalysts or printed circuit boards/ electronic compo-
nents. In total over 250,000 t of feed-materials are treated annually in a highly flexible flowsheet whilst gen-
erating minimal waste. The plant is one of the world's largest precious metals recycling facilities with a ca-
pacity of over 50 t PGMs, over 100 t of gold and 2400 t of silver. [1]
Christian Hagelüken
Figure 1: Aerial view of Umicore's Hoboken plant
2 Flowsheet
Basically the recycling operations at the Hoboken Works are streamlined along two processes: The Precious
Metals Operations (PMO) are fully tuned for the efficient refining of an extended range of complex and valu-
able raw materials, containing precious metals. The Base Metals Operations focus on flexibly, cost-efficient
processing of by-products from the PMO. Major investments of € 200 million have been recently completed,
to develop, install and run new metallurgical operations, completely shifting Hoboken’s focus from mining
concentrates to recyclable materials and industrial by-products.
Over the past decade a completely
renewed plant has been built on site. The
processes are based on complex
lead/copper/nickel metallurgy, using these
base metals as collectors for precious
metals and special metals, such as Sb,
Bi, Sn, Se, Te, In. The main advantage of
the innovated plant is increased
productivity, combined with greater
efficiency, which results in maximised
metal recovery rates. Complex feed
materials, which often contain certain
elements of concern, are systematically
worked upon and turned into recycled,
useful products (figs. 2 & 3).
Figure 2: New flowsheet for Umicore's
integrated metals smelter and refinery
Recycling of Electronic Scrap
Waste - Secondary Raw Materials III, Strbske Pleso, June 2006 3
Figure 3: Principle Input-Output streams for Umicore's integrated metals smelter and refinery;
Cu/Pb/Ni are used to collect precious and special metals
3 Sampling and assaying
The extended, continuously changing mix of complex feed materials such as e-scrap, catalysts, tankhouse
slimes, etc. make sampling and assaying a key success factor for sustainable precious metals recycling. An
accurate determination of the exact composition and the precious metal content of the received materials is
crucial to enable a correct settlement with the customers, but also to steer the optimum processing of the
material through the plant. The sampling and assaying processes are continuously innovated in close col-
laboration with the suppliers, most of the technologies applied are in-house developed. Automation and in-
formation management are important supporting tools to achieve maximum accuracy. The full range of in-
dustrial by-products and recyclable materials are sampled on site.
The operations undergo independent,
internal and external assessments regularly.
Figure 4: Flowsheet for sampling of circuit boards
To obtain a truly representative sample for circuit boards, 100% of the boards are shredded down to a size
of 4 x 4 cm, the primary sample from this first step is then reshredded to 7 x 7 mm, after which a secondary
sample is taken and further prepared to obtain a lab-sample for analysis (fig. 4). Other than in pre-
processing, shredding is applied here only to reduce the size of the material, so that representative incre-
ments can be taken. Sorting out of any materials or fractions does not take place, everything is subsequently
treated in the smelter operations.
Umicore Process
Recovery of
Metals & Energy
Au Ru
Ag Cu Ni
Zn SiO
Se As
Te Pb
Clean off gas Clean waste water
Precious Metals
Ag, Au,
Pt, Pd, Rh, Ir, Ru
Base & Special Metals
Pb, Cu, Ni,
Sb, Sn, Bi, Se, In, Te, As
Au Ir
Shredding to max.
size 4 x 4 cm
Stream sampling
Shredding to 7x 7 mm
Rotating tube divider
Final sample
Christian Hagelüken
4 Smelting and Refining
The main processing steps of the Precious Metals Operations (PMO) are the smelter, the copper-leaching &
electro winning plant and the precious metals refinery. The operations are designed in such a way that raw
materials can enter the flow-sheet at the most optimal process step, determined by their physical aspect,
their analytical fingerprint and their (precious) metals value. The smelter furnace uses the IsaSmelt, sub-
merged lance combustion technology (fig. 5). This involves injecting oxygen-enriched air and fuel in a molten
bath and adding coke as a reducing agent for the metals. Plastics or other organic substances that are con-
tained in the feed partially substitute the coke as reducing agent and fuel as energy source. The smelter
separates precious metals in a copper bullion from mostly all other metals concentrated in a lead slag, which
is further treated at the Base Metals Operations. After leaching out the copper in the leaching and copper-
electro winning plant (fig 5), the precious metals are collected in a residue that is further refined at the pre-
cious metals refinery. This combines classical methods (cupellation) with unique in-house developed proc-
esses (silver refinery) to enable the in-house recovery of all possible variations and ratios of silver, gold and
the platinum group metals (platinum, palladium, rhodium, iridium and ruthenium).
The main processing steps of the Base Metals Operations (BMO) are the lead blast furnace, the lead refin-
ery and the special metals plant. The lead blast furnace reduces the oxidised lead slag from the smelter
together with high lead containing third party raw materials and transforms them into impure lead bullion,
nickel speiss, copper matte and depleted slag. The impure lead bullion, collecting most of the non-precious
metals, is further treated in the lead refinery (Harris process). Besides pure lead and sodium antimonate the
process generates special metals residues, further refined into pure metals (indium, selenium, tellurium) in
the special metals refinery. Bismuth and tin intermediates are tolled out to dedicated companies to produce
pure metals which are marketed by Umicore.
After leaching the nickel out of the nickel speiss and turning it into nickel sulphate at Umicore's Olen plant,
the remaining precious metals residue is treated at the precious metals refinery. The copper matte from the
lead blast furnace returns to the IsaSmelt furnace. The depleted blast furnace slag is physically calibrated for
use in the concrete industry or used as dyke fortification substance.
Figure 5: Umicore's IsaSmelt furnace (left and centre) and electrowinning plant (right)
The Umicore process with its various 'scavenger steps' achieves high overall recovery yields for the precious
metals, since - independent which way they take through the flowsheet (Cu, Pb, Ni) - they finally are all
separated and enter into the precious metals refinery.
Patented lance design
Promotes formation of a
frozen slag layer on the
lance tip
Frozen slag coating
Protects lance from wea
Vigorously stirred bath
by submerged lance
ensuring rapid chemical
reactions and good mixing
can be directly
charged without
further treatment
Refractory lined
designed to
for molten product
Oxygen enriched air and oil/nat. gas
are injected down the lance
Offgas and fume:
special design for
efficient offgas collection with minimised
solids carryover
Recycling of Electronic Scrap
Waste - Secondary Raw Materials III, Strbske Pleso, June 2006 5
5 Environment, Health and Safety
As for Umicore as a whole, Umicore Precious Metals Refining is committed to responsible, proactive and
transparent management of environmental issues. An environmental management system according to ISO
14001 has been implemented at Hoboken in close connection with the quality system (ISO 9001). The envi-
ronmental performance of the plant is continuously monitored, installations and procedures are continuously
being adapted to new legislation in compliance with the European and even stricter Flemish legal environ-
mental requirements. All relevant data are reported to the Flemish authorities in detail and to the public in an
annual environmental report. Since 1995 over € 100 million have been invested in continuous improvement
of the plant's environmental performance.
Air: Hygienic gases and process gases are cooled with energy recovery and cleaned using 'Best Available
Techniques' (BAT). Sulphur present in some feed materials is converted into SO2, which is transformed to
sulphuric acid in the "contact" plant - the gas treatment and contact process acting as a "perfect filter". On
the stack, SO2 and NOx are continuously monitored with a direct display of the measured value in the control
rooms, so that the operators can react immediately (see fig. 6). Diffuse emissions from stockyards and roads
are abated by intensive sprinkling, using either fixed sprinkling systems or watering carts. Further measures
in place include dust free emptying of shipped drums or big bags, dust free sampling procedures, storage of
critical materials in containers inside a warehouse, emptying of the containers under aspiration, transport in
covered belt systems etc. Besides their environmental importance these installations also prevent any losses
of precious metals with the dust fraction, which further improves sampling accuracy and metal yields. Thanks
to these continuous measures, plant emissions are already very low and further show a decreasing trend.
Water: Not only process water, but also cooling water, all rainwater, sprinkling water, etc. is treated in an
onsite BAT waste water treatment plant (WWTP): acids are neutralised, metals, sulphates and fluorine are
removed by physical chemistry processes. Two thirds of the cleaned water is reused internally while one
third is discharged into the river Scheldt.
Soil: All stockyards are provided with a contained concrete floor, all rain and sprinkling water are collected
and treated in the WWTP. The historical soil contamination in the plant is being controlled and huge areas
are being covered with brick rubble to prevent dust generation. Contaminated groundwater is drained away
and treated in the WWTP. A project to rehabilitate the adjacent residential area is ongoing.
Waste: Much is done to find useful applications for all plant outputs: sulphuric acid is sold to the market,
depleted slag is further used, covered by certificates issued by the Flamish authorities. Waste, containing
elements that can't be recycled any further, adds up to only 4 % of the incoming material and is disposed of
in duly licensed landfills. A project to decrease further the amount of waste for landfills is ongoing.
cooler Electrostatic
precipitator Quenching Sulphuric
gasses Process
Filter dust Dust
measurement of
dust, metals, SO
, CO, C
Heat recovery:
High pressure steam
for internal use
Water to Water
Treatment Plant Periodic
measurement of
dust, metals,
, NO
, CO,
, HF, HCl
of SO
, NO
sampling for
Figure 6: Offgas emission control installations at the IsaSmelt furnace
Christian Hagelüken
6 Processing of electronic scrap at Umicore Hoboken
Umicore sources its recycling materials on a world-wide basis and provides customised solutions to manu-
facturers, collectors, pre-processors and other stakeholders of the electronics lifecycle, making use of an
international network of sales offices and partners. To fully benefit from economies of scale, all end-
processing takes part at the Hoboken plant for a wide range of electronic materials, which can be catego-
rised under different aspects.
Value of material
Keeping in mind that "low" and "high" value or grade are relative terms only, even a "high value" electronic
scrap is low value compared e.g. to a precious metal catalyst. E-scrap usually is grouped by the Au-content.
The following examples give some general indications:
- Low value (< 100 ppm Au): TV-boards, monitor boards, (cordless) phones, calculators, shredded bulk
material after Al-/Fe-separation, etc.
- Medium value (100-400 ppm Au): PC-boards, laptop-and handheld-computers, mobile phones, etc.
- High value (> 400 ppm Au): Circuit boards from main-frames, some mobile phones, ICs, MLCCs
Origin of material (production residues or end-of-life streams)
Typical production residues treated by Umicore are populated or unpopulated circuit boards, precious metal
containing punchings and lead frames, multi-layer ceramic capacitors (MLCC), IC's, certain automotive elec-
tronic components, but also overstock and obsolete materials of small devices like mobile phones, calcula-
tors, handheld or laptop computers, digital cameras etc. After removal of batteries and sampling, these small
devices can be treated directly in the IsaSmelt furnace. Important for production waste is a guaranteed, con-
trolled and well-documented destruction and recycling, safely excluding any unwanted re-use of parts.
End-of-life (EOL) streams are supplied by collection schemes, pre-processors, traders and sometimes also
by manufacturers who operate individual take-back systems. With the exception of some small devices (mo-
bile phones etc.) EOL streams have been dismantled and/or pre-processed to remove large plastic parts,
iron and aluminium. Typical materials are printed circuit boards, cut-off parts relatively rich in precious metals
or fractions deriving from shredding and mechanical sorting processes such as metallic granules (mostly
copper based), mixed plastics fractions with residual metals, and (precious) metals containing dusts. Pelleti-
sation of such dust can facilitate sampling and treatment.
As it will be elaborated in the following chapter, mechanical pre-processing has to be conducted in a way
that the loss of valuable (precious) metals into sidestreams, from which they cannot be recovered any more
is minimised. WEEE contains significant amounts of pollutants as well as high burnloss constituents like
plastics. Plastic fractions contain halogens from flame retardants and thus require special installations in a
metallurgical operation to safely prevent the emission of dioxins, furanes or other harmful elements. If, as it
is the case for Umicore's Hoboken smelter, such installations are existing, plastics can be utilised partly as
coke and fuel substitute (feedstock-recycling), which can positively affect the calculation of recycling rates.
Prior to sampling at Hoboken, the material is stored in a secured area. All material streams are traceable
and can be demonstrated to the relevant authorities and to suppliers transparently. The settlement of a recy-
cling lot with the supplier/customer usually is conducted as a toll refining transaction on an assay based for-
mula, refining terms comprise treatment and refining charges, metal credits (in % of analytical value) and
return times for the metals. Additionally, other services like early hedging, financing, metal account man-
agement and logistical assistance are offered. Some (very) low-grade fractions of electronic scrap, where
the net intrinsic metals value after deduction of treatment costs is negative, are also taken in against a gate
fee (in which the metal value is incorporated). Typical examples are metal contaminated mixed plastic frac-
tions. Nevertheless, supplying such material for the customer often is overall more eco-efficient than - usu-
ally complex - mechanical separation of the metals with a subsequent feed of the mixed plastics into a mu-
nicipal incinerator (again, at a gate fee there), where the metals are lost.
Recycling of Electronic Scrap
Waste - Secondary Raw Materials III, Strbske Pleso, June 2006 7
e.g. separating Cu + PM
from feed into own fraction
Recovery rate** %
Concentration rate* %
* in output fraction
** of target metal
PM-loss %
Recovery rate per
individually separated material %
100% 100% 100%
Fe Al plastics
A less complete separation of Fe, Al,
plastics can significantly reduce PM-
losses by unintended co-separation
Figure 7: Photos of some electronic materials/fractions treated by Umicore
7 Recycling chain for electronic scrap
The recycling chain for WEEE consists of different, usually subsequent steps, which are collection, disman-
tling, shredding/pre-processing, and end-processing of the various materials and metals. The final, physical
recovery step at the end-processor - transferring specific WEEE-fractions like circuit boards into refined met-
als - is crucial for value recovery, and also the environmental impacts connected with end-processing can be
quite substantial (both positively and negatively). In today's discussion on the optimisation of WEEE-
recycling, raising attention is put on maximising eco-efficiency, i.e. the environmental and economical bal-
ance, by maximising physical recycling and revenues obtainable thereof, while minimising environmental
burden and total costs connected with the recycling chain. Due to the considerable environmental impacts of
mining and refining precious metals from primary ores, a high overall recycling yield of the precious metals
has not only economical but also large ecological benefits (recycling 1 kg of gold also ecologically is much
more beneficial than recycling 1 kg of iron). In a solely weight based calculation of recycling quotes - as it
presently prevails in the WEEE-Directive - this effect is not considered accordingly.
A holistic optimisation of WEEE recycling has to consider the entire recycling chain, considering the interde-
pendencies between the main steps and including all generated sidestreams. Much more attention in this
context should be placed on the interfaces. Whatever is done e.g. in pre-processing influences the perform-
ance of the subsequent end-processing steps and thus the total chain results. Especially between modern
integrated metals smelters and dedicated shredding and sorting plants, further improvement can be
achieved by mutual optimisation of sorting depth as well as composition and destination of the various frac-
tions produced. Pre-processing usually includes coarse shredding, often followed by some manual sorting,
further size reduction, and mechanical separation techniques. Here, typically magnetic sorting and eddy
current separation of aluminium and other non-ferrous metals are applied, sometimes in combination with
further processing steps (heavy media separation, air tables, sifting etc.). Like in mineral processing of ores,
also for electronic scrap the concentration-yield function applies, as is schematically shown in fig. 8.
The basic rule is that the recovery rate for a specific metal (or material) from an input stream is decreasing
with a rising concentration rate (purity) of that metal separated into an output fraction. From the perspective
of a targeted metal in an output fraction this 'con-
centration dilemma' means that the more complete
this metal is separated from an input stream, the
more it will be contaminated after separation by non
target material. When separating several major
metals (with respect to their share in the feed) in
subsequent processing steps from a complex feed
material, the unintended co-separation of 'minor'
metals can add up substantially. [4]
Figure 8: Interface optimisation between mechanical pre-processing and metallurgical refining
Christian Hagelüken
In the concrete case of electronic scrap this means that the mechanical separation of Fe, Al and plastics
always bears the risk of inevitably losing precious metals (PMs) in these streams. All these losses add up
and reduce the overall PM-yield of pre-processing, which generally aims to concentrate the PMs in a copper
fraction. Accepting higher impurities of Fe, Al and plastics in the copper fraction can boost the overall PM
recovery and thus the generated value. In the case of circuit boards or small devices with a relatively high
concentration of PMs, further shredding and sorting out Fe, Al and plastics in many cases even can be
counter-productive. In circuit boards most PMs are strongly interlinked with plastics, ceramcics or NF-metals,
part of them easily go into dusts, others follow the Fe-fraction and the Al. Especially eddy current separation
in many cases is not selective enough for these materials and significant portions of circuit board pieces can
be contained in the "Al-fraction". Optical sorting or other scavenging processes can be applied, but usually
the better solution is to directly treat circuit boards and small devices in an efficient metallurgical process,
which was designed to maximise PM-yields and "co-separates" other metals by metallurgical means. A case
study from TU-Delft has proven, that this "direct smelter route" for a mobile phone is the most eco-efficient
solution (after having removed the battery). [3], [5]
Another field of interface optimisation are mixed plastic fractions with metal residues from pre-processing. In
most cases it is not economically feasible to further separate these into the various plastic types. The most
common outlets for these mixed fractions, landfill or incineration plants are becoming increasingly restricted
and costly under the recent legislative developments. Furthermore, all residual metals would be inevitably
lost. Separating residual metals by mechanical means can become quite costly while generating only little
additional metal value. If some minimum contents of valuable metals are included, a dedicated preparation
of these fractions to make them fit into an integrated smelter is a possibility that should be considered on a
case to case basis. There will be no general solution but individual best routes depending on type of WEEE,
companies involved and also regional aspects. Requirements in this context are an open dialogue and co-
operative approach between the relevant stakeholders, as well as transparent material flows up to the final
destinations, which until now is often not the case.
7 Conclusions
Integrated metals smelters are a crucial part of the WEEE-recycling chain, which can further increase its
efficiency if interfaces to pre-processing are consequently optimised. Their ability to recover numerous met-
als at high yields and without any "downcycling" in quality can contribute to a significant future supply of sec-
ondary metals. Moreover, such operations can offer possibilities to utilise plastic fractions contained in
WEEE as feedstock substitute for coke. However, it has to be understood that by far not any "copper
smelter" can treat electronic scrap in an environmentally sound way. Only a handfull of integrated smelters
and refiners in the world have the necessary installations for offgas and waste water purification. Umicore's
Hoboken plant has been developed to the globally most advanced full-scale processor of various precious
metals containing fractions from electronic scrap, generating optimum metal yields at competitive terms.
[1] Hagelüken, C: Recycling of electronic scrap at Umicore's integreated metals smelter and refinery, proceedings of
EMC 2005, vol. 1, pp. 307-323, Dresden Sept. 2005.
[2] Where are WEEE going?, Proceedings of a workshop at Antwerp, Umicore, Oct. 2004. (CD-ROM)
[3] Van Heukelem, A., M. Reuter et. al.: Eco efficient optimization of pre-processing and metal smelting, Electronic
Goes Green 2004+, Proceedings, pp. 657-661, Berlin 2004.
[4] Hagelüken, C: Improving metal returns and eco-efficiency in electronics recycling, Proceedings of the 2006 Interna-
tional Symposium on Electronics & the Environment IEEE, pp.218-223, San Francisco May 2006.
[5] Huisman, J.: QWERTY and eco-efficiency analysis on cellular phone treatment in Sweden, TU Delft, April 2004.
[6] http:/
... In the subsequent copper electrowinning, ruthenium is partially oxidized to the highly volatile and toxic ruthenium tetroxide, which leads to losses of ruthenium and thus, to a lower recycling rate for this product. No systematic studies on Recycling process for materials containing precious metals (PM), (simplified and modified according to [2]). ...
... Jaskula [7] summarizes the literature on the behavior of platinum group metals in copper electrowinning. For the dissolution of ruthenium from a copper anode containing Recycling process for materials containing precious metals (PM), (simplified and modified according to [2]). ...
Full-text available
The recycling of material containing precious metals can lead to the entry of ruthenium into the copper electrowinning process, by so far unknown effects. There, ruthenium is oxidized to highly volatile ruthenium tetroxide. In order to avoid ruthenium losses during electrolysis, the oxidation behavior of ruthenium in copper electrowinning was investigated by testing different oxygen overvoltages using lead alloy and diamond anodes. Furthermore, the temperature and the current density were varied to investigate a possible chemical or electrochemical reaction. The results of the study show that ruthenium is not directly electrochemically oxidized to ruthenium tetroxide at the anode. Especially at anodes with high oxygen overvoltage, the formation of other oxidants occurs parallel to the oxygen evolution in the electrolyte. These oxidants oxidize ruthenium compounds to highly volatile ruthenium tetroxide by chemical reactions. These reactions depend mainly on temperature; the formation of the active oxidants depends on the anodic potential. To avoid ruthenium losses in the copper electrowinning process, anodes with a low anodic potential should be used at low electrolyte temperatures.
... Therefore, the alloy density, in this CE, was approximately 7.07 g/cm 3 at 1500 • C, the smelting-collection temperature in this study, namely, ρ A = 7.07 g/cm 3 . Furthermore, the density of slag (ρ s ) can be approximately calculated based on the temperature and compositions of molten slag, as shown in Equations (12) and (13) [39]: ...
Full-text available
Co-treatment for two kinds of hazardous solid waste is an effective method to reduce cost and increase recycle efficiency of value resource. This work developed an integrated process based on capture of red mud (RM) and a one-step heat-treatment process to efficiently recover PGMs from spent auto-catalysts (SAC) and reuse RM simultaneously. Firstly, the iron oxide in RM was reduced to metallic iron to capture PGMs by the reduction process, without the addition of an extra reducing agent, since SAC contained abundant organic volatiles. Then, the mixed waste of SAC and RM was melted under high temperature with additives of CaO and H3BO3. More than 99% of PGMs can be extracted under the optimal conditions of 40–50 wt% of RM addition, 14 wt% of H3BO3 addition, 0.7–0.8 of basicity, 1500 °C of temperature, and 40 min of holding time. In addition, PGM content in obtained glassy slag was less than 1 g/t. The mechanism of iron trapping PGMs was also discussed in detailed, which mainly contained two stages: migration of PGMs and separation of PGM-bearing alloy and slag phases. Besides, the obtained glassy slag was further prepared into glass-ceramic by a one-step heat-treatment process. It was found that the prepared glass-ceramic has good thermostability and an excellent stabilizing effect on heavy metals. Overall, the results indicated that the developed integrated smelting–collection process is an efficient and promising method for the reutilization of SAC and RM.
... Generally, pyrometallurgical and electrochemical treatments [13,14] are used to recover base metals (Cu, Sn, Pb…) from secondary resources. PM sludges produced by this "primary" treatment is then treated using a multi-step complex hydrometallurgical process, composed of a leaching step -cyanide (Mc-Arthur Forest process [15]) or aqua regia leaching [16,17] and followed by numerous separation steps using volatile solvents -liquid/liquid extraction, fractional distillationbefore a final recovery of each PM by electrolysis, cementation or crystallization. These multi-step processes, set up at the end of the 20th century, have some important limitations for workers or installation safety and remain far from sustainable development considerations. ...
Precious metal refining from ore or electronic devices includes hydrometallurgical processes with major concern about toxicity or wastewater production. As an alternative, one-step electroleaching-electrochemical deposition process (EL-ECD) using ionic liquid mixtures was evaluated for palladium and gold recovery. A halide based ionic liquid combined with a diluting ionic liquid was chosen among ten electrolytes after cyclic voltammetry and potentiostatic experiments. These low viscous electrolytes allow complexing Au and Pd, leading to metal leaching at low anodic potential. Moreover, the complexes formed could be simultaneously deposited at the cathode. Metal behaviour is similar for all halide anions tested (chloride, bromide and iodide). Results show that chloride based mixtures are the more suitable electrolyte providing the highest leaching faradic yield. This process appears more sustainable than conventional processes (chlorination, cyanide leaching) thanks to the electrolyte stability limiting solvent losses but also workers exposition.
... Currently, most WEEE is treated using the pyrometallurgical processes established for primary feed concentrates and/or high-value precious metal waste (mainly comprising jewellery and residual copper scraps) in large-scale state-of-the-art recovery plants [33]. Flowsheets of (A) precious metals being recycled from WEEE by a pyrometallurgical process, reproduced with permission from [39] and (B) simplified plan of the Umicore integrated smelter-refinery plant, reproduced with permission from [40]. ...
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The direct use in catalysis of precious metal recovery products from industrial and consumer waste is a very promising recent area of investigation. It represents a more sustainable, environmentally benign, and profitable way of managing the low abundance of precious metals, as well as encouraging new ways of exploiting their catalytic properties. This review demonstrates the feasibility and sustainability of this innovative approach, inspired by circular economy models, and aims to stimulate further research and industrial processes based on the valorisation of secondary resources of these raw materials. The overview of the use of recovered gold and palladium in catalytic processes will be complemented by critical appraisal of the recovery and reuse approaches that have been proposed.
... Copper collection is more suitable to processing of spent catalyst with the carrier of cordierite by adding flux (SiO 2 , CaO, etc.), collector (CuCO 3 or CuO), and reductant (coke, coal, etc.) due to its low treatment temperature (1400-1550 • C) and weak reductive atmosphere. However, long smelting time and high cost are still problems to be solved (Hagelüken, 2006;Zhang et al., 2019). Ding et al. proposed a method which collected PGMs by iron during smelting using Na 2 B 4 O 7 , CaO, Na 2 O and CaF 2 as fluxes in the temperature range 1300-1400 • C (Ding et al., 2020). ...
The feasibility of a facile route to recover platinum-group metals (PGMs) from spent catalyst by microwave smelting of spent catalyst with the additions of nickel matte as metal collector and sodium salts as fluxes was verified, based on the thermodynamic and experimental analyses which evaluated the dielectric properties, conductivities/resistances and viscosities of the materials involved in the smelting process. The results showed that the combined use of sodium salts (Na2B4O7 and Na2CO3) reduced the viscosity and smelting temperature effectively by breaking the silicon-oxygen tetrahedron structure which facilitated the collection of PGMs and the separation of PGMs-enriched nickel matte from smelting slag. In association with the eddy current loss and swirling sedimentation effect produced by microwave heating, 98.59% of Pt, 97.91% of Pd and 97.16% of Rh were collected under the optimal smelting conditions of the mass ratios of nickel matte, Na2B4O7 and Na2CO3 to spent catalyst of 1.25, 0.575 and 0.125, respectively, temperature of 1250 °C, time of 2 h, and N2 atmosphere. This new strategy enabled rapid collection of PGMs from spent catalyst at the low temperature within a short time, contributing to energy conservation and environmental protection.
In the modern era, metal usage can be traced in almost anything from simple household tools to complex electronic equipment. About 95 % of the electronic equipment surrounding us is built using components containing valuable metals, such as gold, silver, copper, palladium, and rare earths. Recycling electronic equipment offers a much richer resource than extracting metals from their respective ores. Printed circuit boards (PCBs) form about 3–6 % of the total electronic waste yet contain considerable quantities of precious metals. Most of the electronic waste (e-waste) that is disposed of, such as computers, mobile phones, televisions, printers, etc., are equipped with PCBs. These products are equipped with printed circuit boards(PCB) which are rich in valuable metals, including copper, aluminium, and gold. Recycling e-waste, especially PCBs, provides a route for economical and profitable extraction of valuable metals other than mining. Waste PCBs can be recycled using mechanical, pyrometallurgical, hydrometallurgical, electrometallurgical, and biometallurgical processes. In this review, the different technologies available for PCB recycling are compared, their limitations are highlighted to appreciate an environmentally friendly recovery of metals from the WPCBs. The PCBs feature a complex composition; therefore, it requires an intricate and novel approach to extract the specific metals. The review briefly analyses the different methods and techniques to extract the constituent elements and serves as a reliable reference for recycling WPCBs.
Waste electrical and electric equipment entering our recycling system poses various challenges in different stages of the whole treatment chain. Losses of valuable metals in the crushing of electrical devices through dusts and fines have been identified as one such challenge. Crushing is nevertheless crucial in order to liberate metals from each other for efficient separation in the sequential mechanical unit processes. This study investigated the relation of crushing mechanism on Printed Circuit Assemblies’ (PCAs) liberation and fines generation in the size reduction of waste mobile phones using two crusher types. The results revealed that a fast-rotating hammer mill produced better liberated PCAs with an overall PCA grade, presenting the purity of PCA fraction of 77% compared to a slow-rotating cutting mill with 58% PCA grade. However, the hammer mill produced over two times the amount of fines compared to the cutting mill. The fines fraction mainly comprised silicon and base metals but also noble metals and harmful elements which need to be taken into account when further treatment is considered. Even though the same elements could be found in the fines from both crushers, differences in the concentrations were observed. In the cutting mill, higher concentrations of ductile materials such as gold and copper were observed in the fines fraction with particle size below 4 mm compared to the hammer mill.
In this research, a simple and economical process based on hydrometallurgy is developed to directly recycle platinum group metals from spent automotive catalysts to synthesize carbon supported platinum-group metals catalysts. Spent automotive catalysts are firstly leached by HCl+H2O2 system, resulting in Pd chloro-complexes. The optimized leaching rates of Pd and Rh are 97.99±2.64 % and 87.70±1.23%, respectively. Then Pd precursor is separated from the leaching solution by precipitation, which can remove most impurities. The Pd precursor or Pd chloro-complexes solution can be used to synthesize carbon supported catalysts directly via an ethylene glycol reduction method. The samples are characterized by SEM, TEM, XRD, EDS, and ICP-OES. 2-4 nm Pd/C are successfully synthesized using recycled Pd. The recycled Pd/C exhibits excellent long-term stability, with no activity loss in the homemade SO32- depolarized electrolyser after 150 hours of 100 mA cm-2 electrolysis. The electrochemical tests indicate that the recycled Pd/C samples are not inferior to Pd/C prepared from (NH4)2PdCl4 reagent.
Alternative mining methods are becoming increasingly important towards sustainable and eco-friendly gold (Au) production. Herein, thiacrown ether (diallyl 15TCE4) with Au³⁺ recognition properties was combined with thermo-responsive N‑isopropylacrylamide (NIPAM) on a silica (SiO2) support via ARGET-ATRP to afford a multi-functional Au³⁺ adsorbent P(NIPAM-co-15TCE4)@SiO2. The adsorbent was successfully prepared as confirmed by FTIR, NMR, TGA, EA, FE-SEM and DLS. The thermo-responsiveness of P(NIPAM-co-15TCE4)@SiO2 was observed at critical temperature Tc ∼34.9 oC. At T = 50 oC (T > Tc) and pH = 2, the maximum Au³⁺ capacity qm = 100.60 mg g⁻¹ was quickly achieved within 2 h. HR-TEM/EDS, WAXD and XPS results indicate that Au³⁺ capture involves complexation, partial reduction to Au⁺ and disproportionation to Au⁰/Au³⁺. It is believed that partial Au³⁺ reduction is coupled with C-S-C oxidation to R2S=O in 15TCE4, which occurred within its cavity and/or between neighboring 15TCE4s that are closely held by the collapsed NIPAM at T > Tc. Meanwhile, desorption occurs at T < Tc through “mechano”-assisted Au release induced by the brush network movement as NIPAM component rehydrates at T = 27 oC. Complete desorption was achieved even in a very mild lixiviant (0.1M HCl/0.1M TU) that eluted tightly-bound Au species and regenerated the adsorbent via S=O reduction to C-S-C. The adsorbent is highly selective with α = 9 – 43,053 for Au³⁺ against Pd²⁺, Pt²⁺, Cu²⁺, Pb²⁺, Zn²⁺ and Ni²⁺ present in a simulated mobile phone leachate. The reversible behavior of P(NIPAM-co-15TCE4)@SiO2 for Au³⁺ capture (T > Tc) and release (T < Tc) highlights the synergy between 15TCE4 and NIPAM, making it a reusable practical adsorbent with consistent performance for Au³⁺ recovery in complex feed wastes.
Printed circuit boards (PCBs) are an essential and central component of electronic waste. The rapid depletion of natural resources, massive generation of end-of-life PCBs and inherently metal-loaded values inevitably call for recycling and recovery. This review critically discusses the systematic and sequential processes adopted for PCB metallic recoveries via physical, pyrometallurgical, hydrometallurgical, and combined technologies. Pre-treatments play a decisive and significant role in upgradation and efficient metal extraction. A novel combination of different pre-treatments and hybrid thermal-chemical routes are often reported for improved separation efficiency and performance. Selective recovery (using solvent extraction, precipitation, polymer inclusion membrane, adsorption, ion exchange) of high purity product from multi-elemental leach solution has recently gained interest and is reviewed. Current recycling techniques at a commercial scale are preferably based on pyrometallurgy (smelting-refining), where electronic waste is only a fraction of the total feed stream. Electronic components such as monolithic ceramic capacitors, tantalum capacitors, integrated circuits, and central processing units mounted on the PCBs are important due to precious metals' presence. The futuristic recycling perspective should treat base and precious metal-rich components separately with minimal environmental effect, end product usage, and maximum economic benefit. Sustainable processing routes for converting discarded PCBs into value-added products should also be attempted, as amplified in this review. An integrated, definite framework for full resource recovery from waste PCBs was proposed.
Conference Paper
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Abstract—The efficient recovery of precious and special metals from electronic scrap has significant benefits - economically, environmentally, but also under a resource conservation aspect. The yields of these metals could be substantially improved by higher collection rates, less scrap exports to regions with insuffi- cient recycling structures, and by interface optimisation, as pointed out in this document. Keywords - electronic scrap recycling; precious metals; inte-
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With the new legislation for Waste Electrical and Electronic Equipment (WEEE) coming up in Europe and similar developments in other parts of the world, a substantial increase of end-of-life electronic equipment to be treated will take place on a global scale. In this context, often much attention is placed on logistical issues, dismantling and shredding/pre-processing of electronic-scrap, while the final, physical metals recovery step in a smelter is often just taken for granted. However, a state-of-the-art smelter and refinery process has a major impact on recycling efficiency, in terms of elements and value that are recovered as well as in terms of overall environmental performance. Besides copper and precious metals, modern integrated smelters recover a large variety of other elements, and can make use of organics such as plastics to substitute coke as a reducing agent and fuel as an energy source. Umicore has recently completed major investments at its Hoboken Works, completely shifting the plants focus from mining concentrates to recyclable materials and industrial by-products. Based on complex Cu/Pb/Ni metallurgy, the plant has been developed to the globally most advanced full-scale processor of various precious metals containing fractions from electronic scrap, generating optimum metal yields for precious and special metals at increased productivity and minimised environmental impact. Especially the interface between pre-processing (shredding/sorting) and integrated smelting offers additional optimisation potential, which can lead to a substantial increase in overall (precious) metals yields.
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The aim of this report is to investigate the environmental and economic consequences of the WEEE Directive, Annex II guidelines for cellular phones and whether the chosen set of rules are eco-efficient. Therefore, two scenarios for treatment of discarded cellular phones are compared: the current collection and treatment in Sweden for 2003 by sending handsets completely to a copper smelter (Boliden) versus following the WEEE Directive Annex II rules on ‘selective treatment’ of the PWB’s (printed circuit/ wiring boards), interpreted as manual dismantling. The outcomes of the analysis might be used to apply for an official EU-exemption for the direct smelter route for treatment of printed circuit boards from cellular phones in Sweden.
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Life-Cycle Analysis is considered an important tool, which is able to incorporate environmental considerations into decision-making. It is used for the development of strategies, which should lead to a lesser overall environ- mental impact. These conventional environmental assessment calculations focus on the use of annualized aver- age produced emissions. This paper shows an improved determination of environmental impacts for a crucial process in the end-of-life chain of electronic products: a copper smelter, as part of an integrated metals smelter and refinery. This paper proposes a statistically based LCA evaluation comprising of four steps (Plant Meas- urements/Data Reconciliation/Model Validation and LCA Statistics). This streamlined approach is necessary to determine whether one can reliably propose strategies to minimize the environmental impact. It is vital to incor- porate an operational and in this case a metallurgical perspective. LCA predictions, without this perspective, sta- tistical basis and standard deviations will prove to be inaccurate and should not serve as a basis to state an opti- mization strategy, because they fail to incorporate the effects of a changing feed strategy, or changing consumer goods properties, on the process (e.g. changing split factors) and the recycling chain.
Recycling of electronic scrap at Umicore's integreated metals smelter and refinery
  • C Hagelüken
Hagelüken, C: Recycling of electronic scrap at Umicore's integreated metals smelter and refinery, proceedings of EMC 2005, vol. 1, pp. 307-323, Dresden Sept. 2005.