Lignite flotation in inorganic salt solutions

Abstract

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 this study. 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 determined that the magnitude of negative charge significantly decreased above 10(-2) M concentration of the salts and the flotation of lignite without flotation reagents also started to take place at concentrations higher than the same value. The contact angles measured on the lignite surfaces also increased with increasing salt concentration. The lignite sample was hydrophilic, 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. In addition, it was determined that MgCl2 and CaCl2 salts were more effective on the lignite flotation than NaCl salt.