| 摘要 |
<p>PURPOSE:To recover a Zn-component as ZnCO3 at a high yield by treating Zn-contg. dust with an aq. (NH4)2CO3-contg. basic soln. to dissolve the Zn- component, then thermally decomposing and crystallizing the soln. CONSTITUTION:Various kinds of the dust contg. Zn are supplied to a dissolving stage and is dissolved with the aq. soln. contg. the basic (NH4)2CO3 formed by blowing gaseous CO2 and gaseous NH3 to form a [Zn(NH3)4CO3]-contg. liquid. The soln. is sent to a refining stage where Zn powder is added to the soln. to settle impurities contg. Pd, etc. After the impurities are removed by filtration, the low-concn. soln. is returned to the dissolving stage. The high-concn. soln. is sent to a distillation thermal decomposition and crystallization stage where ZnCO3 is deposited and the gaseous NH3 is generated. The ZnCO3 is separated by filtration and is cleaned by washing with water; thereafter the ZnCO3 is dried and recovered as the high-purity ZnCO3 powder. The gaseous NH3 generated simultaneously is returned to the dissolving stage for forming the Zn(NH3)4CO3 from the Zn-contg. dust and is recycled.</p> |
