From: Alberto Novo (alnovo@inwind.it)
Date: 01/12/02-04:20:36 PM Z
In the B&S site there is something about this argument.
However, to keep Cr out from a solution the way is this:
1) Cr VI is reduced to Cr III in an acidic medium by some chemicals easily
at hand of a photographer, like for example, sodium thiosulphate. So the
fixing baths may definively end their life, when exausted, redicing
dichromate. But you have to be sure that the solution is acidic.
Hydrochloric or sulphuric acid (about 1% in the final solution) are the
best.
2) Cr III need to be converted in an insoluble form, adding an excess of
strong alkaly to the solution overwelming the acidity needed in the
reduction of the dichromate. Calcium hydroxide is used in the industrial
treatment plants as it is the cheaper substance.
3) the precipitate of chromium hydrate can be settled and filtered.
4) you need to find where to dispose the chromium hydrate...
Alberto
> I am interested in the recent observations on the toxicity of Chrome
VI,....
which occurs in Dichromate, which is used in gum printing among many other
> Is there some way to effectively detoxify (at
> least in part) this solution by converting the Chromium VI to Chromium
III?
>
> Thanks,
>
> Robert Schaller
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