Molybdenum and mixed acid reclaimed from spent pickling soln. - esp. where soln. is used to dissolve molybdenum mandrel wires out of tungsten filaments in electric lamp industry

摘要

Nitric acid is added to the spent soln. followed by heating, pref. to 100-150 deg.C for 0.5-10 h, so the Mo is oxidised to MoO3, which is pptd. and removed from the hot soln. by filtration. Filtration is pref. undertaken at below 100 deg.C The amt. of NHO3 added pref. corresponds with that lost by the soln. during pickling. The filtrate is pref. replenished with conc. NHO3 and/or concn. H2SO4, and re-used in pickling. The oxidn. of the Mo to MoO3 is pref. undertaken at 1-5 bars and for 3 h at 130 deg.C. The spent pickling soln. pref. contains 10-100 g/l Mo, 25-55 wt.% HNO3, and 25-45 wt.% H2SO4. Esp. used with pickling solns. used to dissolve Mo core wires out of tungsten filaments in the electric lamp industry.