7RE: [labcleanout] Re: Disposal guidance: heavy metals
- Feb 22, 2006You're asolutely right, Dave, that RCRA isn't the only reg one must
consider, and I know that the left coast tends to be a tad more paranoid.
(I was in California last month, and noticed that resturants had a sign
posted: Warning: this establishment uses compounds known to cause cancer,
birth defects and heartburn, or something to that effect. Sorta makes one
lose one's appetite!) Copper sulfate is used as a source of copper in feeds
and supplements, and when I was a kid it was used to deworm sheep.
Nevertheless, you are correct that the copper ion is quite toxic to lower
life forms and can't be disposed of in a willy-nilly fashion. I check the
pretreatment standards for the POTW at the end of the pipe before I put
anything down the drain. As for cupric sulfide, it gets an NFPA rating of 0
for reactivity (though that's a bit generous; it will react with some
things, like strong oxidizers) and is said to be insoluble in dilute acids.
(See attached.) A strong acid with a pH of 2 is 0.1N, and I think that
qualifies as dilute. CuS can be oxidized pretty easily, but the product is
CuSO4, so we're right back where we started. I dispose of CuSO4 by putting
it in a pesticide drum, and no one has ever complained; I think one could do
the same with CuS. Another issue to consider: sometimes it is cheaper to
just ship a material rather than spend a lot of time reducing its volume or
treating it, since here at least disposers charge by the drum, and one can
usually find room for a liter or so of Benedict's solution or whatever. I
might try the glucose idea, though, and see how it goes. It could be a
teaching opportunity, too. Rosemary
>From: "Dave Waddell" <waddellenviro@...>_________________________________________________________________
>Subject: [labcleanout] Re: Disposal guidance: heavy metals
>Date: Wed, 22 Feb 2006 15:38:59 -0000
>Thanks Rosemary. I always enjoy our conversations and always learn
>I like the treatment methods you've described. One challenge we and
>California face is our state toxicity criteria includes acute toxicity
>measured in oral-rat LD50, inhalation-rat LC50, Dermal rabbit LD50 and
>aquatic tox to salmonids (usually rainbow trout) as a TLM-96. Copper
>sulfate designates as a Washington State-only dangerous waste at
>concentrations over 1% in compounds or solutions due to oral toxicity
>of 300 mg/kg. So we always have to be careful about assuming non-RCRA
>substances aren't hazardous.
>Since the copper (II) sulfide resulting from precipitation of the
>Benedict's is completely insoluble, toxicity won't be an issue. Can I
>assume it won't generate hydrogen sulfide gas when exposed to pH
>conditions between 2 and 12.5 so it doesn't designate as reactive?
>-- In firstname.lastname@example.org, "rosemary bottcher" <rbottcher@...>
>Hi, Dave. First, I'd suggest that hazardous and non-hazardous wastes
>not be mixed, for obvious reasons. Benedict's solution is not a RCRA
>waste and isn't particularly worrisome. I wouldn't recommend puting a
>lot of it down the drain, however, because the copper ion can make the
>POTW's precious bugs sick. Evaporation of solutions will certainly
>reduce the volume of waste to be disposed of, but it can take a looong
>time. I prefer to speed things up by adding Na2S to precipitate the
>sulfides of "heavy" metals. I put that in quotes because can anyone
>out there tell me exactly what is the definition of "heavy metal?"
>Folks call arsenic a "heavy metal" and it's not even a metal!) I also
>use Na2S to detect the presence of "heavy metals" in unknowns. As for
>the Benedict's solution, how about this: add an excess of reducing
>sugar, cook it and throw the mess away? Rosemary
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