| 摘要 |
Manganese dioxide is produced by precipitating so-called manganous hydroxide, Mn(OH)2, from a manganous salt solution, oxidizing the precipitate and reacting it with an acid of dissociation constant greater than 10-5 at 25 DEG C. The manganous salt solution, e.g. manganous sulphate solution, may be prepared from low-grade manganese ores. Impurities are removed before addition of ammonia or caustic soda solution to precipitate the Mn(OH)2. The latter is washed and oxidized, e.g. by bubbling air or oxygen through a suspension at pH 8-9, to yield in fact Mn2O3. 2H2O. Acids specified are: sulphuric, nitric, hydrochloric, acetic, sulphonic and chloroacetic. Manganous salts are also formed during acidification and can be returned for Mn(OH)2 precipitation. Inorganic salts, e.g. potassium ferrous sulphate, potassium ferric sulphate and the sulphates of Al, Li, and Mg, which may be added with the acid to the extent of 0.1-2.0% by weight of the oxidized Mn(OH)2, influence the structure of the product, of which they may form a part. |
