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7RE: [labcleanout] Re: Disposal guidance: heavy metals

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  • rosemary bottcher
    Feb 22, 2006
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      You'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@...>
      >Reply-To: labcleanout@yahoogroups.com
      >To: labcleanout@yahoogroups.com
      >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
      >something new.
      >
      >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?
      >
      >Dave W.
      >
      >-- In labcleanout@yahoogroups.com, "rosemary bottcher" <rbottcher@...>
      >wrote:
      > >
      >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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