29 kesä Geopolymerisation of sulphidic mine tailings – GEOSULF
Name: Utilization of sulphide mine tailings in geopolymer materials
Duration: 3/2014- 3/2017
Total costs (€)/Tekes support: 929 423 € / 268 000 €
Leading research organization partner: University of Oulu (Oulu, Finland)
Contact persons: Mirja Illikainen, University of Oulu, mirja.illikainen(at)oulu.fi
Research organization partners: AGH University of Science and Technology (Krakow, Poland), Aveiro University (Aveiro, Portugal)
Company partners: Agnico Eagle Finland Oy, First Quantum Minerals Ltd, Outotec Oyj
Number of reviewed publications, incl. submitted manuscripts: 1
Number of other publications and reports: 2
Need and motivation of the project:
Disposal of mine tailings is one of the most important environmental issues during the mine lifetime. Especially tailings from processing of sulphide minerals can cause environmental and ecological risks because of their tendency to oxidize in the presence of water or air. The oxidation causes production of sulfuric acid and consequently leaching of heavy metals. Because of small particle size and harmful chemical properties, utilization possibilities of sulphide mine tailings are limited. Usually, tailings are long-term stored in large tailing bonds.
Main set targets:
The GEOSULF project aims to sustainable utilization of sulphide mine tailings in geopolymer materials. In geopolymerization, alumina and silica rich materials are activated with alkali solution. The formed geopolymer is a three-dimensional amorphous network that can immobilize hazardous components into its structure. The GEOSULF-project aims at deep understanding on geopolymerization of mine tailings into a form in which harmful substances cannot dissolve. The project involves four parts:
- Understanding of geopolymerization by model sulphide and heavy metal components
- Development of geopolymer recipes and aggregates from mine tailings
- Development of novel geopolymer based products like mine backfills and concrete bricks
- Environmental assessment of products developed
By activating sulphide mine tailings with NaOH solutions at room temperature without any co-binders, it is possible to produce paste materials with compressive strength (UCS 28d) up to 3.5 MPa, meeting the requirements set to mine backfill materials. The compressive strength of mine tailing -based geopolymer pastes can be increased up to 60 MPa when commercial ground granulated blast furnace slag (GGBFS) is used as a co-binder. In addition, sulfide mine tailings can be successfully granulated with sodium silicate solution and the agglomerates could be used as a replacement material for LECA gravel in lightweight concretes.
However, activation of mine tailings with NaOH solution significantly increased leaching of e.g. arsenic (As), antimony (Sb) and sulphur (S) from mine tailings. Although the leaching of As under NaOH activation was decreased by adding GGBFS to mine tailings, it did not prevent As leaching efficiently. Leaching of heavy metals was successfully reduced when Ca(OH)2 was used as an activator solution instead of NaOH. Leaching of S remains a challenge since the leached amount of sulfates from prepared specimens exceeded the limit set for inert landfill waste both with NaOH and Ca(OH)2 activators. At the moment, minimization of leaching of heavy metals and sulfates is under investigation. This involves usage of other alkali activator solutions and co-binders in sulphide mine tailings treatment.
Commercialization measures and/or potential
As soon as the challenge regarding the leaching of heavy metals is solved, technologies needed for geopolymer production (both granulation and casting) are easily adopted into commercial use.
List of publications
Reviewed publications, incl. submitted manuscripts
Kiventerä J., Yliniemi J., Golek L., Deja, J., Ferreira V., Illikainen M., Utilization of sulphidic mine tailings in geopolymer materials. Int J. Miner. Process. 149(2016):104-110.
Other publications and reports
- Geopolymerisation of hazardous materials, Posteri, Jätehuollon kesäpäivä Oulussa 11.6.2015
- Geopolymerization of sulphidic mine tailings, Posteri ja flash presentation, Governing Board meeting in Paris on 14-15 Oct 2015