A process for the removal of sodium azide and sodium hydroxide from an aqueous solution

摘要

Sodium nitride is prepared and separated from the mother liquor by a process in which the mother liquor contg. 35% NaOH, and 4-10% sodium nitride is contacted with ammonia soln. in a batch or continuously operating reactor. After a predetermined waiting period the mixture separates into upper and lower layers, the upper contg. water ammonia, NaOH and sodium nitride, the lower contg. a large amount of NaOH and water and a small amount of ammonia. The ammonia is removed from the upper layer and the soln. contg. the hydroxide and the nitride is recycled to the process to combine with the initial basic soln. of sodium nitride. The ammonia is removed from the lower layer giving an approx. 50% concn. aq. soln. of NaOH free from sodium nitride and ammonia which can be used for numerous industrial applications. The recycling eventually produces a soln. contg. 11-15% sodium nitride which can be crystallised out of soln. by evaporation. The prior art process was accompanied by a considerable loss of sodium hydroxide, the majority of which is recovered at high concn. in this invention. Extra processes involving use of extra NaOH to effect the separation are not necessary.