Basic research project 2008: "Elucidation of mechanisms of immobilization of heavy metals during inorganic polymer synthesis using ferronickel slag"
Project acronym: GeoImmob
Project duration: 01/09/2008 - 31/08/2010
Funded by: Research Committee of Technical University Crete, budget 12,000 Euros.
Scientific coordinator : K. Komnitsas, Professor, Mineral Resources Engineering Department, Technical University Crete, 73 100, Hania, Crete, Greece, tel.: +30 28210 37686, fax: 30-2821069554, e-mail: komni@mred.tuc.gr.
Researchers:
Project summary: Development of new environmentally friendly technologies is required in order to improve the management of mining and metallurgical wastes and to minimize environmental impacts, as well as the disposal cost. Geopolymerisation is an emerging technology that may contribute to the utilization of various wastes and the development of new materials with advanced properties such as high compressive strength and immobilisation efficiency.
Despite the intense research efforts carried out the last decade regarding inorganic polymer technology, the wide utilisation of the products is restricted due to limited data regarding their durability under various environments. As far as mechanisms involved when various wastes are used as raw materials further research is required.
The present research project investigates the mechanisms of immobilisation of heavy metals (Cu, Pb, Cd, Cr, Ni, Co, As) in inorganic polymers (geopolymers) synthesised using electric arc furnace ferronickel slag. The effect of factors such as addition percentage of metals (up to 3% w/w), anions added in the mixture (nitrates or sulphate salts) on the compressive strength of the final products is assessed. When addition percentages are higher than 2% w/w the compressive strength is negatively affected no matter if heavy metals are added either as nitrate or sulfate salts. The application of TCLP test shows that the metals are immobilised effectively in the inorganic polymeric matrix.
Geochemical stability of the specimens is estimated through immersion in various aquatic or acidic solutions (distilled water, sea water, simulated acid rain, 0.05 N HCl solution) or subjection to freeze-thaw cycles. The strength of specimens decreases substantially only when they are immersed in corrosive HCl solution . Analytical techniques (XRD, FTIR, TG-DTG and SEM) are used in order to define new formed phases that play an important role in the immobilisation of heavy metals.
Geopolymerisation is one of the research topics carried out in the research unit of "Management of mining / metallurgical wastes and rehabilitation of contaminated soils". The main part of the project was carried out in the line of Mrs Zaharaki's PhD thesis which was completed successfully on July 1st, 2009. Moreover, various MSc and diploma thesis have been carried out during the last six years.
Timetable:
Publications:
Pictures:
Fig.1: Ferronickel slag (as received from LARCO S.A.)
Fig.2: Slag-based inorganic polymer containing 1% w/w Pb as PbSO4
Fig.3: Slag-based inorganic polymers immersed in distilled water, sea water, simulated acid rain and HCl solution 0.05 N (left to right)