Work

Dual effect of calcium ions on sodium oleate adsorption and spodumene flotation

Year: 2026

Type: article

Abstract: The flotation of spodumene with sodium oleate is highly sensitive to Ca²⁺ concentration, but the underlying interfacial mechanisms remain unclear, especially under inhibitory conditions. To address this, we systematically investigated how Ca²⁺ governs the spodumene-oleate system using micro-flotation, solution chemistry, and nanoscale force measurements. Flotation tests at pH 8.5 reveal a pronounced dual role of Ca²⁺. Low Ca²⁺ dosages activate the spodumene surface, increasing the recovery to about 76% at an optimum concentration of 5×10⁻⁵ M, whereas concentrations above 9×10⁻⁵ M cause a sharp decline, with recovery falling even below that in deionized water. Adsorption and zeta potential measurements indicate that activation arises from a 1:1 Ca²⁺/Li⁺ ion exchange, which generates highly active coordination sites for oleate chemisorption. In contrast, excess Ca²⁺ promotes the bulk precipitation of calcium dioleate, reducing the concentration of soluble oleate ions and leaving less collector available for adsorption on the spodumene surface. AFM force measurements further show that, under inhibitory conditions, the deposited calcium dioleate forms a soft, viscoelastic colloidal coating, characterized by long-range adhesion and extended pull-off stretching. This coating physically passivates the spodumene surface and acts as an interfacial barrier to bubble-particle attachment. By linking solution chemistry with nanoscale interfacial mechanics, this work clarifies the dual role of Ca²⁺ in spodumene flotation and provides new insight into mineral systems sensitive to water hardness.

Source: Minerals Engineering

DOI: 10.1016/j.mineng.2026.110882