SPECIFIC ION EFFECTS IN NaCl-KCl FLOTATION WITH CARBOXYLATES
Wei Huang and Anh V Nguyen
School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
Email: anh.nguyen@eng.uq.edu.au
ABSTRACT
Potash flotation is an industrially proven success of flotation of soluble salts, but its collector adsorption
mechanism remains elusive. In this paper, specific ion effects in NaCl-KCl flotation with carboxylate
collectors were investigated. Flotation recovery and contact angle were determined as a function of brine
composition of NaCl and KCl. The experimental results have shown that wettability of KCl and flotation of
the soluble salts with laurate collectors were dependent on brine ion composition. Specifically, adding Na +
to brines decreased hydrophobicity of KCl crystals and their flotation recovery. Both KCl and NaCl could
be floated with laurate collectors. However, flotation of NaCl was greatly enhanced by adding K + to brine
whereas flotation of KCl was significantly suppressed by the presence of Na ions. The decrease in KCl
recovery upon adding Na+ is attributed to the counter-ion binding in the pulp. The flotation recovery
enhancement of NaCl in the presence of K+ is explained by two effects: 1) increasing K+ concentration leads
to a better dispersion of collector colloids in the pulp and 2) K + enhances the collector adsorption at NaCl
crystal surfaces. The water affinity matching rule can explain the specific ion binding behaviors and
supported by the SFG spectroscopic results.
KEYWORDS
Potash flotation, contact angle, specific ion effect