Conversion-regeneration of spent picking bath - - by neutralisation with ammonia and decomposition of ammonium sulpha

摘要

Regeneration of a spent pickling bath contg. (NH4)HSO4 as the main component is carried out by neutralising the bath with ammonia; separating the precipitated solids; heating the filtrate to decompose the resulting (NH4)2SO4 into (NH4)HSO4 and NH3; and re-using (NH4)HSO4 in the pickling bath and NH3 in the neutralization operation. The process is inexpensive, and the metals dissolved in the pickling bath can be recovered.