The innovation EIT RawMaterials project Morecovery is directing efforts to accelerate the transition from a linear to a circular economy by offering smart solutions for the sustainable extraction and use of raw materials from secondary sources.
Recently, a method developed at the laboratory scale for recovering Ni and Co from drainage mine water was demonstrated in the operational environment at the technology readiness level 7 (TRL 7). The success of the Morecovery project is built on the vast experience of the project partners, each with their specific expertise, including the project leader, the Geological Survey of Finland (GTK), together with Savonia University of Applied Sciences, the University of Eastern Finland, the University of Huelva, the Spanish National Research Council, the Finnish Minerals Group, Keliber and LTU Business.
The Morecovery project is aimed at creating solutions for harvesting critical raw materials (CRMs) from mine waste and side streams to boost sustainability in the raw materials sector and secure the raw materials supply of strategically important elements. The criticality of these materials derives from a combination of a rapid increase in demand and supply shortages. In turn, this has generated immense interest in the recycling and recovery of CRMs from secondary raw materials.
In 2019, we conducted a screening campaign of prospective test sites in Finland followed by a comprehensive assessment and ranking of their potential in terms of the recovery of valuable metals and minerals from water, solid streams and waste. The examined sites were closed mines representing different ore types, including Särkiniemi (Ni), Kotalahti (Ni–Cu), Hammaslahti (Cu–Zn) and Hitura (Ni–Co).
The water samples were collected from a stream or pool of drainage water by the base of the mine waste tailings facilities and analysed for metal concentrations. The main focus was on REE and other selected CRMs. Among the examined sites, the highest potential was observed for water from the jarosite-affected tailings drainage of the Hitura mine site. Consequently, the drainage water from the Hitura mine was selected as a case for studies in the laboratory and at the pilot scale.
Our approach was directed towards the use of inexpensive chemicals and proven technologies. A two-stage method for the recovery of Ni and Co from Hitura drainage water was developed in the laboratory by UEF. In the first stage, most of the Fe was removed via an oxidation–precipitation reaction, whereas Ni and Co remained in the solution. In the second process stage, Ni and Co were selectively recovered.
During the process, two types of sludge are captured and initially dewatered: Fe-rich sludge and the targeted Ni–Co-enriched sludge, which could potentially be an attractive product for further processing. The outcome of this work was the determination of the key process performance characteristics and obtaining the operating data necessary to design a pilot test rig for demonstration in the operational environment.
Based on UEF`s laboratory studies, the method was up-scaled in 2020, and work on the technical development of a pilot-scale industrial water treatment and recovery system was conducted by Savonia and GTK. A sea container was used to house the pilot test rig (12 metres long). The pilot was designed to be a continuous process with a nominal capacity of 1 m3/h, a pumped-gravity flow system, full automation and online process monitoring. The pilot container was deployed at the Hitura test site in August and remained in operation until the end of October 2020. Ni and Co recovery tests were carried out to determine the most effective dosing of the required chemicals, the retention time and mixing intensity, and to assess the effect of scale-up on system process performance.
The physical and chemical properties of sludge generated during the process, and the factors that influence these properties, were also examined. In the pilot campaign, we demonstrated the feasibility of the method developed in the laboratory and validated it in the operational environment at the TRL 7.
With the focus on new market findings and the successful introduction of services being developed in the project, the Morecovery consortium is looking further for additional opportunities and also preparing for the next pilot campaign in 2021, in the Iberian Pyrite Belt in Spain.
Małgorzata Szlachta, Senior scientist, Circular Economy Solutions, firstname.lastname@example.org