I am removing high phosphorous (5~10%) nickel electroless plating from ceramic circuit boards using 4 part concentrated nitric acid to 8 parts water and 1 part 35% hydrogen peroxide, generally following a published recipe for this task. This works well at 60°C.

I'm doing everything slowly and carefully in a hood with proper protective equipment in another group's laboratory.

They have a modest (50 liter?) acid disposal storage tank, but the container does not appear to be vented. There's just a screw cap that you close and tighten when done. I'm a little worried that even after my solution cools, it has the capacity to produce oxygen gas after disposal in their container.

From this Quora post I understand that one might be able to catalyze decomposition of peroxide using an iron (II) salt, but that suggestion does not apply to a nitric acid solution with added peroxide.

I also don't want to boil the solution to decompose the peroxide, for safety reasons.

Question: How might one go about decomposing hydrogen peroxide in a nitric acid solution so that it can be disposed of, with out generating oxygen gas later?

I suppose that leaving it at 60°C for a few days, loosely covered so that it doesn't evaporate too quickly might work, but I have no way to know.

I am removing high phosphorous (5~10%) nickel electroless plating from alumina circuit boards using 125 ml concentrated nitric acid to 250 ml water and 60 ml 35% hydrogen peroxide, generally following a published recipe for this task. This works well at 60°C. (I need to re-use the ceramic boards)

I'm doing everything slowly and carefully in a hood with proper protective equipment in another group's laboratory.

They have a modest (50 liter?) acid disposal storage tank, but the container does not appear to be vented. There's just a screw cap that you close and tighten when done. I'm a little worried that even after my solution cools, it has the capacity to produce oxygen gas after disposal in their container.

From this Quora post I understand that one might be able to catalyze decomposition of peroxide using an iron (II) salt, but that suggestion does not apply to a nitric acid solution with added peroxide.

I also don't want to boil the solution to decompose the peroxide, for safety reasons.

Question: How might one go about decomposing hydrogen peroxide in a nitric acid solution so that it can be disposed of, with out generating oxygen gas later?

I suppose that leaving it at 60°C for a few days, loosely covered so that it doesn't evaporate too quickly might work, but I have no way to know.