Abstract
The effect of waste rock minerals introduced by dilution on the flotation of spodumene was investigated. The objectives of this work were to investigate how flotation yield and grades deteriorate mainly by Mg-bearing biotite and amphiboles that are introduced to the system by waste rock dilution and find the possible ways to improve the flotation performance regarding these Mg-bearing minerals.
Laboratory flotation tests were conducted with modifications to the standard procedure and new conditions. Analytical methods used in this work include mineralogical tests like electron probe micro-analyzer (EPMA) to find out accurate elemental assays for the minerals in the deposit, especially biotite. X-ray fluorescence (XRF) and atomic absorption spectroscopy (AAS) to analyse flotation products contents. Mineral liberation analysis (MLA) for liberation, associations, Mg-distribution and modal mineralogy. Information about mineral recoveries in different flotation stages was obtained from element to mineral conversion calculations with HSC Chemistry software.
The target grade and recovery of Li₂O for the Rapasaari ore were established on 4.5% and 84.18% (as a previous standard test). The use of Na₂CO₃ and starch modifiers gave promising results slightly improving the recoveries to 85.29% and 85.11% respectively while reaching almost 4.5% grade in final concentrate.
Mineral liberation analysis (MLA) showed that biotite contains most of the Mg (80–90%), other minerals are amphiboles (mainly edenite and hornblende) and in less extent chlorite and clays. Biotite and amphiboles end up in the final concentrate mostly fully liberated while apatite is mostly coarse mixed grains. Mg-bearing minerals float into the concentrate because of similar surface properties with spodumene. Those similar properties may be due to chemically active Al-O sites that form on the mineral surfaces when the mineral breaks through its cleavage planes during comminution. Al-O sites act as collector attachment spots in fatty acid flotation and compete for collector adsorption
