MSO<SUB>4</SUB>-H<SUB>2</SUB>O-C<SUB>2</SUB>H<SUB>5</SUB>OH系 (M=Ni, Co, Zn, Cd, Cu) の相平衡に及ぼす硫酸添加の影響

Abstract

As a further study on the phase equilibria in the metal sulfate-water-ethanol systems, the influence of sulfuric acid adding to the systems was investigated at 298K, and also at 278K for nickel and zinc sulfate systems.The solubility ofsulfates in sulfuric acid-ethanol-water mixture decreased considerably with increasing concentration of alcohol, and increased slightly with increasing concentration of sulfuric acid. The recoveries of crystallized salts by addition of 2kg of ethanol ranged from a minimum of 64% in the zinc sulfate system to a maximum of 98% in the copper sulfate system for the solutions containing 1 mole of sulfate and 3 moles of sulfuric acid per kilogram of water at 298K.The temperatures at which heptahydrates transform to hexahydrates in the nickel, cobalt, and zinc sulfate systems varied with amounts of ethanol and sulfuric acid present. Hexahydrates crystallized out from the solutions at lower temperatures in the presence of sulfuric acid.It may be concluded that these properties can be applicable to practical processes in which sulfuric acid is present in almost all case. In practice, however, it may be more efficient to neutralize the solution prior to crystallization process, or to recycle the spent solution after a partial precipitation of salt from pregnant solution.