Effect of inorganic salt on flotation of lignite

In this study, the flotation of low-quality lignite coal in the presence of NaCl, MgCl2 and CaCl2 inorganic salts with/without the use of kerosene and MIBC as flotation chemicals was investigated. In addition, the zeta potential and contact angle measurements were performed. The lignite sample exhibited a negative surface charge over a broad pH range and had no isoelectric point (iep). It was also determined that the magnitude of negative charge of lignite significantly decreased above 10-2 M concentration of the salts and the flotation of lignite without flotation reagents also weakly took place at salt concentrations higher than the same value. The contact angles measured on the lignite surfaces increased with increasing salt concentration. The lignite sample have a hydrophilic character, and therefore very difficult to float. Consequently, the flotation of lignite with collector and frother was not achieved to the desired extent, even using high reagent concentrations. In the absence of flotation chemicals, high concentrations of these salts also provided low flotation performances. However, the flotation of lignite could be achieved with kerosene and MIBC in the presence of inorganic salts. The flotation experiments of lignite containing ash of 25.02% showed that a concentrate with an ash content of 19% was obtained with a combustible recovery of 51.2% at 10-1 M MgCl2 and 8 g/dm3 kerosene concentrations. In addition, it was determined that MgCl2 and CaCl2 salts were more effective on the lignite flotation than NaCl salt.