The invention provides a method for preparing ultra-pure
coal by using a chemical method and recovering waste liquid, which comprises the following steps: mixing
coal with an alkaline solution, carrying out alkali
dissolution treatment, and carrying out
solid-liquid separation to obtain alkali
dissolution filter residues; mixing the alkali-soluble filter residues with water, carrying out
dealkalization treatment, and carrying out
solid-liquid separation to obtain dealkalized filter residues; mixing the dealkalized filter residues with an acid solution, carrying out
acid dissolution treatment, and carrying out
solid-liquid separation to obtain acid-dissolved filter residues; and
drying the acid-soluble filter residues to obtain the ultra-pure
coal. Wherein the alkaline solution comprises
sodium ions,
calcium ions and hydroxyl ions, the
molar ratio of the
sodium ions to the
aluminum element in the coal is (18-30): 1, the
molar ratio of the
calcium ions to the
silicon element in the coal is (1.0-1.1): 1, and the concentration of the hydroxyl ions is 15-18 mol / L. According to the method provided by the invention, not only is the ultra-pure coal with relatively low ash content prepared, but also the removal rate of aluminum in the coal is increased, and aluminum
recovery is realized; the consumption of the alkaline solution is reduced, and the cost is reduced.