Effects of electrolytes on the mineralization process in oily-bubble flotation of low rank coal

The type and concentration of ions in the flotation pulp directly affect the surface potential of mineral parti- cles and bubbles hence control the mineralization process in flotation. Starting from both aspects of thermodynamics and kinetics,the influence of different electrolytes on the interaction energy between coal particles and oil bubbles was calculated by DLVO theory. Additionally,the induction time between coal particles and oily bubbles was used to evalu- ate the mineralization efficiency at different electrolyte conditions,while oily-bubble flotation tests were conducted to verify the effects of electrolytes on the attachment and mineralization processes between coal particles and oily bub- bles. The results indicated that negative values of surface potential of coal particles and oil bubbles both decreased with the increase of concentration of NaCl and CaCl2 ,and the interaction energy barrier between coal particles and oil bub- bles decreased as well. No interaction energy barrier was observed when the concentration of CaCl2 was 100 mmol / L. With the increase of concentration of the two electrolytes,it showed a gradual decline in the induction time of attach- ment of coal particles to oily bubbles and the combustible recovery was improved correspondingly. At the same electrolyte concentration,the interaction energy barrier and induction time between coal particles and oil bubbles in CaCl2 so- lution were lower than that of in NaCl solution,while the combustible recovery was higher correspondingly. However, when the concentration of AlCl3 electrolyte exceeded 20 mmol / L,the interaction energy barrier and induction time in- creased gradually while the combustible recovery decreased with the increase of concentration of AlCl3 electrolyte.