Aqua Regia Disposal...
mtang at stanford.edu
Tue Oct 30 06:28:40 PDT 2007
Hi John --
Thanks -- yes I spoke with Kevin brought up exactly those concerns (if
only ALL labmembers were so conscientious!) He's etching a few
nanometers of gold and Pt on a single wafer and using only a couple
humdred ml. This seems well within the acceptable dilution capacity of
our system -- and these metals are not toxic. So we agreed that
aspirating this should be OK, in this case.
shott at stanford.edu wrote:
> Thanks for raising this issue and checking before handling this
> stuff. A quick Google search seems to indicate that explosions of
> aqua regia in closed waste containers is a common .... and serious
> .... problem.
> For example, I've a attached short PDF document describing accidents
> related to both aqua regia and pirahna from the University of
> Manitoba. It seems to me that we need to come up with a better
> solution than a closed waste container.
> Let me ask a couple of questions:
> 1. Are there other etchants that might be used?
> 2. How many grams of etched gold and/or platinum do you expect to
> have in the waste material?
> In particular, I'm wondering why we can't rely on the acid waste
> neutralization system to handle this. Certainly if it were "only"
> aqua regia, the AWN system could handle it as long as we took
> appropriate precations at the pouring/diluting stage at the wet bench
> (that is, we don't want a reaction with water to spatter this stuff
> on you or anyone else). Depending on the weight of gold and/or
> platinum in the solution may cause us a problem with the
> concentration of metallic material that we are allowed to introduce
> into the waste stream. However, if we don't have a metal
> concentration problem, I think that cooling the aqua regia and then
> carefully disposing of it in the "normal" acid drains may be a safer
> Comments or additional information from anyone else on this list?
> Quoting Kevin Crabb <kcrabb at stanford.edu>:
>> Hello SNF Safety Folks,
>> I am hoping to use aqua regia (mixture of 3:1 concentrated
>> hydrochloric acid
>> to concentrated nitric acid) to remove platinum and gold grid structures
>> from my wafer. I was told it is okay to do this at the wetbench
>> general, as
>> long as I collect my waste separately.
>> However, after doing more research, it has come to my attention that
>> regia will fume (it produces chlorine gas) for hours/days (depending
>> on the
>> temperature, volume), and I was wondering how best to deal with
>> this. Would
>> it be possible to leave the waste container open in the fume hood
>> until it
>> finishes fuming? If not, is there a vented bottle cap that could be
>> Any information/suggestions on how to handle this situation would be
>> appreciated. Thanks,
>> kcrabb at stanford.edu
>> PS-If it matters, I expect to only need ~200mL of the aqua regia
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