High Temperature Hydrolysis of Aluminum Sulfate Solutions.
U S Patent 1983 Jul; (4):
Alohso4 is precipitated from al2(so4)3 solutions, such as obtained by leaching aluminous ores, e.g., clays, by hydrolysis at >300 deg c at appropriate pressures in an autoclave. The alohso4 is easily rinsed to remove impurities and is readily converted to metallurgical-grade al2o3 by calcination. Thus, solutions containing al2(so4)3 were hydrolyzed at 170 deg-320 deg c. The product obtained at <300 deg c had a composition and x-ray diffraction pattern corresponding to those of (h3o)2al6(so4)4(oh)12 and the yield was lower than at >300 deg c. At >300 deg c, alohso4 was the product.
U.S. Patent No. 4,394,368, July 19, 1983; Chem. Abstr. 98:182,030P