Surface crystal chemistry of spodumene with different size fractions and implications for flotation

The flotation and adsorption of sodium oleate (NaOL) on spodumene with four different particle size fractions (45-75 mu m, 38-45 mu m, 19-38 mu m and 0-19 mu m) were investigated. The flotation recovery increases upon slightly decreasing the size fraction, reaching a peak value at a size fraction of 38-45 mu m. The recovery then decreases gradually upon further decreasing the particle size over the entire investigated range of solution pH values. The specific chemisorption sites for the anionic NaOL collector are the Al sites on the surface of negatively charged spodumene, which is confirmed by FTIR and zeta potential measurements. Anisotropic surface energies and broken bond densities are calculated based on density function theory (DFT) to characterize the surface chemistry of spodumene crystal planes. The anisotropic adsorption behavior of NaOL on different crystal planes of spodumene is studied in terms of adsorption conformations and interaction energies by molecular dynamics (MD) simulations. It is demonstrated that NaOL prefers to bind in a monodentate chelating complex configuration to the most stable surface plane, the (1 1 0) plane, which has two broken Al-O bonds. The (1 1 0) plane of spodumene is more favorable for chemisorbing NaOL than the (0 0 1) plane, which has one broken Al-O bond. The flotation behavior of spodumene with different particle sizes is well explained by the surface crystal chemistry. Based on the findings of this work, further improvement in spodumene flotation is possible if a selective comminution or grinding process is used that favors the production of (1 1 0) planes. (C) 2016 Elsevier B.V. All rights reserved.