Electrolysis grade zinc oxide-hydroxide recovery - from zinc chloride soln. by neutralising with alkali and pptn with ammonia

摘要

The pptn. of Zn oxide-hydroxide (I) suitable for electrolysis from ZnCl2 solns. (II), esp. those obtd. by elution in the ion exchange process from liquors from the wet treatment of various ores and pyritic prods., e.g. roast ore from pyritic ores contg. S and Cl and from solns. obtd. in the recovery of volatile chlorides, comprises neutralising the free acid in acidic (II) at 50-60 degrees C with an alkali (III) and then adding NH3, as gas or aq. soln., to ppte the Zn as Zn(OH)2, heating the suspension to 95-100 degrees C to attain the best pptn. conditions and then separating the pptd. (I) suitable for the prodn. of electrolytic Zn. The process allows the recovery of Zn from low grade ores. The prod. does not require further purificn. Since the process does not lead to the formation of Zn oxychloride, the formation of encrustations in the heat exchangers is avoided.