Effect of Calcium Ions on Induction Time Between a Coal Particle and Air Bubble

Abstract

Particle-bubble attachment is an essential step for a successful flotation; the induction time is defined as the minimum contact time required for particle-bubble attachment in a solution. A novel induction timer was built to investigate the effect of calcium ions on induction time between the coal particle and air bubble. The induction-time measurement of coal particle and air bubble attachment indicated that induction time increased with increasing concentration of calcium ions. The induction time was 17 ms in the deionized water; however, the induction time increased to 32 ms at a calcium ions concentration of 1 mmol/L. X-ray Photoelectron Spectroscopy analysis showed that either Ca(OH)2(s) or CaCO3 precipitated on the coal surface after the adsorption of calcium ions. The precipitate of Ca(OH)2(s) and CaCO3 are hydrophilic and would weaken the hydrophobicity of the coal surface, so the induction time between the coal particle and air bubble increased with the presence of calcium ions.