Method for the production of iron oxide pigment or pigment intermediate and hydrochloric acid

A method for producing an iron pigment and hydrochloric acid with reduced or substantially eliminated waste streams includes: providing an iron chloride solution, wherein the iron chloride solution includes one or both of iron (II) chloride and iron (III) chloride; neutralizing the iron chloride solution with one or both of ammonia and ammonium hydroxide to form a slurry of an iron oxide solid component and an ammonium chloride solution; separating the iron oxide solid component from the ammonium chloride solution; drying the iron oxide solid component to form an iron pigment or pigment intermediate; reacting the ammonium chloride solution with an alkaline-earth metal solid to form an alkaline-earth metal chloride solution and to evolve ammonia as a vapor, wherein at least a portion of the evolved ammonia reacts with water to form ammonium hydroxide; recycling one or both of the evolved ammonia and the formed ammonium chloride for use in connection with the neutralization step; and pyrohydrolyzing the alkaline-earth metal chloride solution to form hydrochloric acid and to regenerate the alkaline-earth metal solid. Iron pigment or pigment intermediate produced in accordance with the method may have a yellow, red, or black color.