Abstract: Iron oxide red can be prepared by hydrothermal method from the precursor of Fe(OH)₃ and Fe(OH)₂ colloid that is obtained by adding ammonia to acidic leaching solution produced by the reaction of pyrite cinders with sulfuric acid.With a Guangdong pyrite cinder as raw material, research laid stress on the best process conditions after acid leaching for preparing iron oxide red preparation by acid leaching-hydrothermal method.The results show that at the conditions of a total iron concentration in acidic leaching solution of 2.0 mol/L, hydrothermal reaction temperature of 200 ℃ and time of 0.5 h, and acidic leaching solution's pH=8 and n(Fe²⁺)/n(Fe³⁺)=0.11, an iron oxide red that satisfies the quality indexes for state standard for Class A product can be obtained, with main phases being Fe₂O₃ and FeO(OH) and particles being uniformly pseudocubic.Meanwhile, ammonium sulfate of industrial first grade can also be gained from the filtrate of hydrothermal reaction product.

Key words: Pyrite cider, Acid leaching, Hydrothermal method, Iron oxide red