Bedlasky
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Heavy metals waste
Hi.
I plan to buy some heavy metal compounds - sodium molybdate, strontium nitrate and nickel sulfate. I have some lead in home too, maybe I will some
piece of it dissolve in HCl. What with waste of these metals? I plan to use only small amount of these compounds (maybe nickel sulfate in larger
scale, but waste I would precipitate as nickel hydroxide or basic carbonate). So should I pour it in in small amount to the drain or should I pour it
in to the container? And what with waste in container?
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j_sum1
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I think nickel is your most problematic here. I won't speak specifically to that since I am inexperienced with Ni.
As a rule, heavy metals are most problematic as organic compounds. Soluble salts are the second most problematic. Aerosol dust can acually be worse
than solubles but is easier to manage. And at the lowest end of the hazard scale are bulk chunks of insoluble material.
Some places will accept hazardous waste. I know that woelen collects his and takes his to his local waste treatment (in solution form I think)
labelled as photographic chemical waste.
I recycle where I can. I recover Cr when possible. Ditto Cu, and other transition metals. Ag I convert back to metal. Non-toxic and non-hazardous (Fe
for example) I sumply flush down the drain with plenty of water.
Anything that might pose a problem (Ba or non-recyclable quantities of Pb for example) I precipitate and store temporarily. Periodically I mix a
slurry of this waste with cement and sand and let it set into a brick. Once completely hard I dispose of as solid waste which goes to landfill.
My quantities are generally pretty low: typically test tube scale. I also source a lot of material from otc sources. (I am currently experimenting
with extraction of V from steel alloy.) I figure my waste will in most cases be on a par with normal household disposal of these things. I aim to do
better from an environmental perspective than an average householder would.
That said, if I was to start experimenting with something I have not used before, say Ni or As, one of my first steps would be to research and come up
with a sensible disposal or recycling protocol.
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woelen
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I collect heavy metal waste in a bottle and if it is full, then I bring it to a municipal waste processing facility. I tell them it is photography
darkroom waste. On the bottle I write "heavy metal waste" with symbols of the heavy metals in it (e.g. Pb, Ni, Mo, V). I never had any questions about
this bottle. If I would tell them it is waste from chemistry experiments then I probably would get more questions, hence my telling that it is
photography darkroom waste. It is important for me that the waste does not go down the drain. Because I mostly work in ml quantities (test tubes), it
takes a long time before I have a full bottle.
Besides that, not all metals need to go in that waste. The following metals go down the drain:
- titanium
- iron
- chromium (after assuring that it is reduced to the +3 oxidation state)
- manganese
- zinc
- lanthanides
- tin
- alkali metals
- alkine earth metals, except barium (I do not do experiments with the extremely toxic beryllium)
- aluminium
None of these are really toxic, and especially when only test tube quantities (100's of mg) are used, I see no problem in flushing these down the
drain.
[Edited on 10-5-19 by woelen]
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Bedlasky
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Thanks for answers.
I mostly work in test tube scale too. Sometimes I make few grams of some compound (for example I made few weeks ago some copper oxides and copper
chloride) or crystals - but this proceses does have only really small scale of heavy metal waste. My only heavy metal now is copper. I will try
recover back as much material as I can and use it again. Municipal waste processing facility is cca 10 minutes from my home, so I will collect waste
and carry off to it.
[Edited on 10-5-2019 by Bedlasky]
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Sigmatropic
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For copper specifically, I add aluminium foil wait for the exothermic reaction to set in.
Ot if that doesn't happen (when there is no chloride present) add a small amount of HCl to break the passivation layer and let the reaction run its
course. Ultimately giving copper metal as a fine powder which I then dispose of down the drain. Or filter it off and then dispose of it in regular
waste and the filtrate down the drain.
I would think this works for all metals that have a higher oxidation potential than aluminum and that would include most heavy metals, heavy earth
alkali metals (Sr, Ba) excluded. Is there anyone who can confirm this? Since these have insoluble sulfates, carbonates and hydroxides there's no
problem.
But as someone else has said, sometimes it is the solution that is the problem.
[Edited on 10-5-2019 by Sigmatropic]
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Bedlasky
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I tried mix aluminium foil with chromium(III) salts but nothing happened. But with Cu2+ is reaction pretty quickly in acidic environment.
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woelen
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Thread Moved
23-5-2019 at 11:39 |
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