Abstract
The alkali activation of mine tailings is of interest to diminish the impoundment storage of large waste stream from mining industry. However, most of the mine tailings, like phosphate mine tailings generated in Finland, are rather inert and need pre-treatment to induce the reactivity for alkali activation. In this work, mechanochemical treatment was conducted to improve the reactivity of phosphate mine tailings. The ground specimens were subjected to the crystal structural analysis of X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermal analyses by Thermogravimetry/Differential Thermal Analysis (TG/DTA), showing the increment of amorphous content and structural degradation as a function of grinding time. The subsequent alkaline reactivity test illustrated incremental alkaline dissolution of Si, Al and K and a schematic diagram of altered phlogopite structure (sources of aluminosilicates in tailings) was also proposed. Additionally, the mineralogical composition of individual particles was carried out by mineral liberation analysis (MLA), thereby evaluating the influence of pre-treatment on the mineralogy of tailings. The results indicate profound micromorphological changes and structural cleavage of the precursor due to grinding, which strongly increase alkaline reactivity.
Highlights
In recent years, the frequency of extreme climates has considerably increased due to excessive emission of carbon dioxide generated from human activities
BSE images were collected via a Scanning Electron Micro scopy (SEM) with Energy-dispersion spectroscopy (EDS) and Mineral Liberation Analysis was performed on 1-min and 16-min samples to evaluate the mineralogical change within each particle
The grinding has an explicit effect on the particle size distribution and specific surface area
Summary
The frequency of extreme climates has considerably increased due to excessive emission of carbon dioxide generated from human activities. Alkali-activated materials (AAMs) have become widely studied in the application of construction due to their sustainability and low CO2 emission (Turner and Collins, 2013). AAMs can be produced from industrial waste or natural minerals, which has desirable chemical reactivity for alkali activation. Those glassy precursors such as blast furnace slag (Douglas et al, 1991), fly ash (Phair and van Deventer, 2002), other pozzolanic minerals (Xu and Van Deventer, 2000) show highest potential, while mine tailings rich in aluminosilicate or carbonate minerals are less investigated (Kinnunen et al, 2018)
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