RECOVERY AND PURIFICATION OF BORON FROM COAL FLY-ASH

A process has been developed to recover boron from coal fly ash in which boron exists at low concentration in a mixture of high concentration of less desirable species. Of the boron contained in the ash, 72% can be leached with dilute sulfuric acid when the pH of the final pregnant liquor is kept at 7.0, the other undesirable transition metals being left in the residue. The boron is then concentrated using chelating resin with a functional group of glucamic type. Eightyseven percent of the boron is recovered and is then concentrated to 3.6 g/dm3 with a purity of 98.9 percent. This liquor is further treated to remove impurities by a solvent extraction technique, employing 2-ethyl-1,3-hexanediol as an extractant, and a purified liquor for borax production is obtained. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.