Metso Insights Blog Mining and metals blog Socrates: New insight on leaching & recovery of gold from ore in cyanide-free glycine media
Metals refining
Dec 15, 2020

Socrates: New insight on leaching & recovery of gold from ore in cyanide-free glycine media

The European Training Network for the sustainable, near zero-waste valorization of critical metal-containing industrial process residues named SOCRATES has been launched in September 2016 in the framework of the Marie Skłodowska-Curie Action (MSCA-ETN). As a basis for a concerted effort to strengthen the EU’s critical-metal supply chain for Ge, In, Ga and Sb, SOCRATES trained 14 Early-Stage Researchers (ESRs) in technological innovation, such as metal extraction (WP1), metal recovery (WP2), residual matrix valorization (WP3) and integrated assessment (WP4).
sustainable metals

Early-stage researchers were extensively trained in scientific, technical and soft skills, each researching a part of the value chain. After four years of intensive collaboration between the academic and industrial partners, the project ended on August 31, 2020.


Successful collaboration

SOCRATES brought together the organizations from academia, industry and the research sector (Table 1). Metso Outotec Research Center in Pori, Finland was also involved in SOCRATES together with Aalto University’s research group of Hydrometallurgy and Corrosion in Espoo, Finland.

Participants of SOCRATES
Participants of SOCRATES
Socrates metals
Scope of the SOCRATES project in the metals value

Metso Outotec Research Center hosted two early-stage researchers (Pelin Altinkaya and Ivan Korolev) working on leaching and electrochemical recovery of critical and valuable metals in cyanide-free solutions under supervision of Professor Mari Lundström. The research was focused on leaching kinetics of metal dissolution and selective electrowinning of metals from complex process solutions. Optimal leaching parameters for gold extraction were evaluated using response surface methodology.

Collaboration between Metso Outotec Research Center and Aalto University resulted in several successful research projects. The goal of one of the investigations was to extract gold from mildly refractory ore in cyanide-free glycine agitating leaching media, followed by gold recovery from pregnant leach solution. This study was conducted by Pelin Altinkaya, Zulin Wang, Ivan Korolev, Joseph Hamuyuni, Mika Haapalainen, Eero Kolehmainen, Kirsi Yliniemi and Mari Lundström.


Unique findings

The results of the mentioned research have been published in the peer-review international journal. The study showed two major findings: that the adequate gold extraction (90%) can be achieved in totally cyanide-free glycine media, with intensive agitation in the presence of oxygen within the industrially acceptable timeframe (Figure 2), and that gold can be successfully (88%) recovered from pregnant glycine solution by the electrochemical-redox replacement (EDRR) method. 

leaching gold
Comparison of gold extraction in glycine media vs. conventional cyanidation. Source: Altinkaya P., Wang, Z., Korolev I., Hamuyuni, J., Haapalainen, M., Kolehmainen, E., Yliniemi, K., Lundström, M. (2020). Leaching and recovery of gold from ore in cyanide-free glycine media. Minerals Engineering, 158, 106610.

The results per early-stage researchers are now featured on the project website. All scientific publications originating from the project (open access journal and conference papers) can be found online.

You can read the full research article here:



This project has received funding from the European Union's EU Framework Programme for Research and Innovation Horizon 2020 under Grant Agreement No 721385. Project website:

This article is part of our Hydrometallurgy Newsletter Issue 1/2020. Visit the issue front page for all articles and greetings from Mikko Rantaharju, Vice President of Hydrometallurgy business line.

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