Copper mine tailings valorization using microbial induced calcium carbonate precipitation

The solidification of copper mine tailings was investigated by using the natural biological process known as microbial induced calcium carbonate precipitation (MICP) as a potential method to valorize this waste stream. A submergent method was used to grow bio-columns and the toxicity of copper on Sporosarcina pasteurii (the ureolytic bacteria which drives the MICP process) was investigated. The bio-columns produced from copper mine tailings had a compressive strength of 0.54 MPa, lower than bio-columns produced from beach sand (1.85 MPa). The low porosity of the copper mine tailings limited the depth to which the MICP reaction could successfully occur, resulting in a 1.8 mm ± 0.4 mm crust forming around the outer extremities of the bio-columns. The results demonstrated that the particle size was a key deciding factor and that, as a result, MICP is not suitable for producing 'thick' bio-cemented materials from small particles (<100 μm) such as mine tailings. However, this method could produce thinner material such as bio-tiles or it could even be used to potentially cement together toxic dust particles typically formed on mine tailing heaps.