Process of extraction of aluminum values from coal ash

摘要

A process for preparing a solution of high aluminum content from the combustion residue of a solid carbon-containing fuel having a carbon content of 2% or less by weight and an iron content calculated as Fe2O3 of 4% or less by weight is described. The process consists of (a) pretreating said residue with nitric acid at a temperature lower than the next extraction stage which follows and removing the nitric acid solution from the residue and then (b) extracting said treated residue with nitric acid of strength about 30% to 65% by weight strength at about 100 DEG to 225 DEG C., the amount of nitric acid employed in said pretreatment step and in said extraction step being in excess of the cationic equivalent actually dissolved in each step.