Metal binding - a question for the chemically inclined.

[nhemann]

I read an article in the NYT a bit ago about how they are using fish bone meal to bind up lead in soil into compounds that cannot be absorbed by the body. It got me thinking if this would be applicable to some of the chemicals/metals used in the darkroom. Unfortunately, my chemistry is nowhere near what it should be to answer that question myself - I'm just a lowly marine engineer

The article:
http://www.nytimes.com/2011/07/21/science/earth/21fishbones.html?pagewanted=2

 

[Bob-D659]

Silver is a lot easier to recover from fixer that mining it. No need to neutralize it.

 

[nhemann]

I was never so worried about silver - the value drives its own recovery proceses and there are plenty of outlets, even if its just another person with a recovery unit. I'm especially thinking about less desirable metals like selenium and other intensifier/toners. Or for that matter just some of the more noxious beasties that could be bound up and essentially inerted.

The extreme example, though obviously not applicable, would be the vitrification of reactor material to stabilize it for long term storage.

 

[Photo Engineer]

The only heavy metals in films or papers are Osmium, Rhodium and Iridium. They are present at about 10^-6 moles per mole of silver, and the silver is present at about 300 mg / foot square in a high speed B&W film. So, there is no big worry about the film or paper.

Selenium is a problem, of course as are gold toners and some other toners. If there are concerns, they must be disposed of as hazardous waste in compliance with local regulations. Silver in the fixer is not a big problem as it can be recovered.

PE

 

[nhemann]

Hi PE,

I was hoping you would chime in sooner or later - to speak to my original point, would it be possible to do what they did in the article? i.e bind up the typical photography metals in such a way to render them essentially inert?
I realize it might be an academic question in the end but my curiosity was piqued when I read it.
neil

 

[Photo Engineer]

Well, at the end of the process, all Silver ions are bound up in the fixer, or washed out in the wash.

About all you can do is reclaim the Silver as metal via electrolysis or precipitate it out as the Hydroxide. One is easy and the the other is complex. The easy one is by electrolysis and the simplest is just throwing a chunk of steel wool into the fixer. However, this too begs the issue by replacing Silver with Iron. In the final analysis (pun intended) you end up replacing one chemical with another in all of these and local laws may be the final controlling factor.

PE

 

[Mike Wilde]

Read up on the sequestering properties of EDTA if you are interested in one way that heavy metals are extracted from those who have absorbed too much. I beleive the term is 'chelating agent'.