METHOD OF SEPARATING MAGNESIUM FROM WET-PROCESS PHOSPHORIC ACID

A method of separating magnesium from wet-process phosphoric acid characterized in that the magnesium is separated as a readily filterable fluoride-phosphate complex compound containing magnesium and aluminum. The fluoride ion required for formation of the magnesium-containing precipitate is preferably formed by hydrolysis of fluorine compounds normally in the crude acid. In the case of insufficient quantities of any of said precipitation components, additions of such components are made to the acid or to the reaction components from which the acid is produced. The wet-process phosphoric acid low in magnesium is especially useful for production of stable ammonium polyphosphate fertilizer solutions.