Mobile phone scrap can contain precious metals, such as gold and copper. VTT
Technical Research Centre of Finland has developed a biological filter made of
mushroom mycelium mats enabling recovery of as much as 80% of the gold in
electronic scrap. Extraction of copper from circuit board waste, on the other
hand, can be enhanced significantly by flotation the crushed and sieved
Although research into the biological methods is active, these are still
rarely used in metal recovery chains. In a European “Value from Waste”
project, VTT developed both biological and mechanical pre-treatment methods
for more efficient recovery of precious metals from electronic waste. Other
methods developed by researchers included recovery of gold from dissolved
materials by biosorption and extraction, using as few harmful chemicals as
Fungi catch gold and filter out impurities
VTT has developed a method that harnesses biosorbents, such as fungal and
algae biomass, for the recovery of precious metals converted to a solution. In
VTT tests, more than 80% of the gold in the solution adhered to the biomass,
compared with only 10–20% of the harmful process chemicals.
The uniqueness of the method lies in the structure of the biomass. Different
filament structures can be formed, for example, into biological filters, which
makes further industrial processing of precious metals easier.
Gold also separates well in liquid-liquid extraction
The project developed a method with high extraction capacity for gold
recovery, using the newest environmentally-friendly extraction reagents. In
VTT experiments, it was possible to recover more than 90% of the metal
solution dissolved from a circuit board with the help of functional ionic
liquid. The method facilitates extraction of desired components from
Recovering copper from circuit boards by flotation
The new pre-treatment methods developed by VTT allow separation of most
plastics and ceramics from waste. In VTT experiments, cell phones were crushed
and the particles sieved and separated magnetically and by eddy current into
circuit board fraction. Treating once more by crushing, sieving and flotation,
resulted in a fraction with high concentration of valuable metals for solution
extraction experiments. Flotation raised the copper content of circuit board
fraction from 25% to 45%, while gold content increased by a factor of 1.5.
“Value from Waste” project
The growth of cleantech industry, the rise in the world market prices of
metals, and concentration of metal production in China have resulted in a
situation in which extraction of several metals from waste streams has become
advisable even in Finland. Ever stricter recycling and utilisation rates for
electronic waste are also pushing the development of recycling technologies.
The purpose of the EU project “Value from Waste” was to develop recovery
processes on a more sustainable basis, to clean materials of impurities that
reduce opportunities for further use, and to increase the amount of recovered
The methods developed in the project included mechanical pre-treatment,
solution extraction, use of biological methods, and optimisation of treatment
chains. The new treatment methods will enable the metal refining industry to
use cleaner electronic waste in larger amounts.
In the two-year “Value from Waste” project of the research consortium AERTO
(Associated European Research and Technology Organizations), VTT participated
in joint technology R&D with the following six European research institutes:
Fraunhofer ICT and Umsicht (Germany), CEA (France), TNO (the Netherlands),
SINTEF (Norway), Tecnalia (Spain) and SP (Sweden). The project was
co-ordinated by SINTEF from Norway.
Flotation is a separation method that separates hydrophobic particles from
hydrophilic particles by blowing air into sludge containing both types of
particles. Hydrophobic particles are picked up by air bubbles and float to the
top of the sludge as froth that can be skimmed off mechanically.
Liquid-liquid extraction is a method that extracts metals at aqueous
interface selectively into another organic interface immiscible with water.
This method, widely used in industrial processes, enables selective extraction
of precious and heavy metals from water. The metal solution concentrated into
an organic interface is thus extracted in purer form for further processing.
PHOTO: Mobile phone
scap (Photo: Antonin Halas)