Abstract
The mining industry generates a notable amount of mine tailings (MTs). Disposal of MTs creates environmental impacts such as air pollution and the release of heavy metals into surface and underground water. The European Union (EU)-funded project “Integrated mineral technologies for more sustainable raw material supply” (ITERAMS) includes an effort to produce eco-friendly backfill materials to enhance operation and mine safety and covers for surface deposits of tailings based on geopolymerization technology. This paper investigates the effects of activator concentration, curing temperature and time on alkali-activated materials based on low-alumina MTs from the Cu/Ni mine in Northern Finland. Alkaline activators containing sodium silicate solution (Na2SiO3) at different concentrations were used and two different curing temperatures, 40 °C and 60 °C, for periods of 7, 14, and 28 days were considered. Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD) were performed to investigate the structure, morphology and phase compositions of the alkali-activated products. The effect of curing temperature and alkaline solutions on mechanical strength and water absorption were investigated. The results indicate that the alkalinity and curing temperature affect the mechanical and microstructural properties of the compositions of alkali-activated MTs. The 30 wt% Na2SiO3 addition enables the alkali activated MT to improve the compressive strength with a highest value of 6.44 and 15.70 MPa after 28 days of curing at 40 °C and 60 °C, respectively. The results of this study deliver useful information for recycling and utilization of MTs as sustainable material through the alkali activation.Graphic
Highlights
The mining industry creates a huge amount of mine tailings (MTs) each year [1, 2]
This paper studies the feasibility of alkali-activated mine tailings (AAMTs) with different percentages of Na2SiO3 solution
The patterns of the alkali-activated product of the five MT-Na specimens can be classified into two types: (a) patterns with the peaks that are remnant from parent MT and (b) patterns with the peaks that are formed during alkali activation
Summary
The mining industry creates a huge amount of mine tailings (MTs) each year [1, 2]. MTs are crushed rock deposits left over after the metal-bearing minerals have been extracted from the ore [3]. The huge amount of MTs produced by mining operations and caused environmental and safety problems, including serious water pollution. The pollution raised up from contamination of surface water, groundwater, and soils by the leaching of heavy metals, and sulphur compounds [4]. There are different approaches to reduce the potential environmental hazards related to MTs: (i) isolation of MTs, which includes isolation of MTs from the nearby environment by capping the tailing impoundment surface (ii) chemical stabilization of MTs by chemical or cementitious material additions in order to immobilize the heavy metals through physical–chemical reactions, and (iii) a combination of these two methods. The effect of additives cause an improvement at the surface erosion resistance and reduce water penetration, which led to isolates the underlying tailings from the surrounding environment [5–7]. OPC recommends benefits in the stabilization of MTs, there are still some problems such as high energy consumption and C O2 emissions which are related to the OPC addition
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