Abstract: A method for removing at least one impurity from coal is provided. The method comprises providing coal having a plurality of impurities and contacting the coal with a first leaching solution. The first leaching solution reacts with at least one of the impurities to produce one or more first products soluble in the first leaching solution. The method further comprises adding a neutralizing composition to the first leaching solution. The neutralizing composition reacts with the first leaching solution to form a precipitate. The method further comprises separating at least a portion of the first leaching solution from the coal and the precipitate and contacting the coal and the precipitate with a second leaching solution. The second leaching solution reacts with at least one of the impurities and the precipitate to form one or more second products and one or more third products, respectively, the second products and the third products being soluble in the second leaching solution.

Abstract: A process for treating mixtures of solid coal and fly ash containing metallic oxides, silicon dioxide and sulfur compounds in order to produce treated coal and substantially pure silicon dioxide comprising (1) reacting a mixture of the coal and fly ash with hydrogen fluoride in water to produce a liquid stream comprising silicon fluoride and metal fluorides and a solids stream comprising unreacted coal and sulfur compounds; (2) reacting the sulfur compounds with metallic nitrates dissolved in water to form an aqueous solution of nitrate, metallic and sulfur ions; (3) separating the aqueous solution of nitrate, sulfur and metallic ions from the solid coal; (4) washing the previously treated solid coal with water; (5) reacting the silicon fluorides and metal fluorides with metallic nitrates in an aqueous mixture to form solid silicon dioxide; and separating the solid silicon dioxide from the aqueous mixture.