Precipitation of jarosite compounds as a method for removing impurities from acidic wastes from chemical coal cleaning

Spent acid from the washing stage of chemical coal cleaning processes contains sodium, iron, and sulfate impurities. One option for treating the spent acid stream is to precipitate the impurities as double salts in the jarosite compound family. This technique was studied in relation to reaction time and pH. Fe and sulfate were removed effectively from model solutions at pH levels of 1.5-2.3, but optimum Na removal was possible only within the narrow pH range of 1.4-1.6. Maximum precipitate yields were realized within about 6 hr at both 80 and 95 degree C, with at least 80% of the Fe and sulfate and 60-75% of the Na removed.