Efficient separation of high-ash fine coal by the collaboration of nanobubbles and polyaluminum chloride

The purification of high-ash fine coal is limited by the fine particle size. On one hand, fine pure coal particles are difficult to be captured by bubbles due to the lower collision probability between them; on the other hand, fine clay particles are often recovered by entrainment due to their lower mass, which result in the pollution of the clean coal. In this paper, we proposed a novel method to separate high-ash fine coal by the synergistic effects of nanobubbles and polyaluminum chloride. Equipped with a range of techniques including settling efficiency analysis, rheology behavior measurements and flotation test, it was found that apparent size distribution of fine coal particles increased in the presence of nanobubbles and thus increased the final combustible recovery. The recovery of clay particles, however, is also enhanced by entrainment and/or entrapment in the presence of nanobubbles, which was alleviated with the aid of polyaluminum chloride by increasing their size distribution. The experimental results are expected to provide a valuable reference to industrial application in separating similar wastes by flotation.