Abstract:

The quality of flotation depends on the different wettability between organic and mineral matter. A method was adopted in order to promote the performance of low-rank coal flotation, in which the low-rank coal slime first adsorbed calcium ions and then surfactant molecules （C₁₂EO₁₅） and reached adsorption equilibrium, and was finally treated by ultrasonic wave to desorb the surfactant. The results indicated that calcium ions could promote the adsorption of C₁₂EO₁₅ on the surface of organic matter, in which the adsorption capacity was increased from 7.14 mg/g to 7.39 mg/g. When the time of desorption treatment reached 60 s, C₁₂EO₁₅ molecules would desorb from the surface of organic matter but further adsorb on the surface of mineral matter. The amounts of hydrophilic and hydrophobic functional groups on the surface of organic matter both increased after desorption treatment, and the wetting heat was improved from 31.79 J/g to 32.93 J/g. As the time of desorption treatment increased, the yield and ash content of clean coal increased, respectively. When the time of desorption treatment was 30 s, the best flotation performance could be obtained, in which the yield of clean coal was 72.01% and the ash content of clean coal was 30.85%.

Key words: low-rank coal, surfactant, ion, desorption, flotation