Discussion in 'Black and White' started by kathryn_treacy, Aug 18, 2016.
A short 2002 thread on silver recovery - it may help
Cheap silver recovery system
We all probably poop more mercury.......
Speciation of mercury excreted in feces from individuals with amalgam fillings. - PubMed - NCBI
Electrolytic systems extract silver however the remaining silver level is still too high for federal level and far too high for most state levels. Iron wool trickle systems can pass most federal and state levels.
Strange as it may seem, the major use for rapid fixers (ammonium thiosulphate) is as a plant fertiliser.
You can even plate or re-plate decorative silver-plated items with it. If they have a copper layer, you don't even need electricity.
However, removing the silver won't make the thiosulphate content or the potential for chemical contamination any less.
Two or three gallons? Just dig a hole and pour it in! Obviously not anywhere where animals graze, or where you want to grow crops or vegetables. Nor where it's going to leak into an aquifer, but I'm sure you must be able to find a couple of square feet of sacrificial dirt somewhere. If you dig the hole deep enough it may not even kill off the topsoil that you replace.
Do they have laws about disposing of silver in Nevada? Where the stuff occurs naturally anyway.
So using steel wool without soap (oil?) and putting it in a plastic? metal? bucket and then pouring the fixer on top of the wool and then letting it sit covered? for some number of hours or days? will allow me to pour the liquid out down the drain. Then I have steel wool with silver in it. Can this be thrown away? Or do I need to dispose of that in any special way? Is there a ratio of how much wool I should use vs. the amount of spent fixer? Typically I used the fixer a few times before pouring into the bottle.
When I was young, I poured it all down the drain and didn't even know it was harmful. I'm just trying to do the right thing now. Thanks for responding. Maybe you helpful folks can fill in some details for me to try.
Kmac yes I saw that thread and that is one of the threads that gave me the steel wool in a bucket idea, but there is never a lot of detail. for me a few jugs of this stuff is decades worth for me and I shoot less film today. I expect it's a one time shot. I may have more but I won't accumulate much more or as fast.
And pouring it down the pipes once I remove the steel wool after the procedure won't cause any risk to the pipes? Or do I need to do it in the street in the drain?
Thanks again for your posts.
In the street drain puts it directly into the rivers etc.
Not the same as the sewer or septic tank.
Check you local sewer treatment regs, many allow small amounts from home low volume developers.
It’s a matter of balance of volume over time.
Two thoughts - you could air evaporate the liquid - the residue from your current chemistry plus another half a lifetime of hobby use would not fill a two pound coffee can.
Second, before I lived in the country, our suburban town had a facility that accepted hazardous waste, virtually anything that shouldn't go in the garbage. Can't recall if there was a small fee, but you did have to show I.D. to prove you were a resident. When clearing the house to move I brought them worse things than photo chemicals with no problem.
Fixer formulas, sodium thiosulfate and ammonium thiosulfate contain sulfur. Spent fixers contain silver in solution. A high volume photofinisher may have a fixer silver loading exceeding 10 grams per liter. Silver is what the municipalities don’t want. This is because, in the course of their treatment, silver compounds fall out of solution and comingle with the sludge. Sewer operators sell sludge; it is used to make fertilizers and as land fill. High silver content reduces the value of the sludge. (1 gram = about 1 raisin).
However, silver is not the real problem. This is true because the fixer, loaded with sulfur, reacts with silver forming an inert compound, silver sulfide (harmless). The real menace: A few drops of fixer causes chlorine to effervesce and come out of solution (this is the stuff of aquarium de-chlorinator. The treatment plant must chlorinate to kill bacteria (federal law). The chlorine level must be high like that of a swimming pool. Fixer from a commercial lab will elevate the cost of chlorination. Home-based darkroom activity has minuscule effect, likely below detectable levels.
Why the fuss? Municipalities test for silver. The test uses nitric acid to liberate silver sulfide. Thus the test is positive. However, nature can’t liberate this compound, so the sludge is benign. This does not change the fact that a positive test reduces the selling price of the sludge.
Electronic silver recovery at the photo lab, if operated with due diligence, reduces the silver content of the fixer from 10 grams per liter to 1 gram per liter. The plated-out silver is 95 to 98 percent pure. If the lab attempts to continue extracting silver, the lowest they can get is perhaps ½ gram per liter, and this will be degraded because it will be silver sulfide, which has greatly reduced value, it is harder to refine. At about ½ gram per liter, electrolyte activity ceases. To obtain 5 mg (federal requirement) the lab must polish the effluent with iron wool or chemical precipitation.
Why would a photo lab use electrolytic method? Fixer becomes exhausted as the silver level climbs. Using the electrolytic method to reduce silver in the fixer to 1 gram per liter is desirable as this solution can be reintroduced into the processing machine. Fixer treated with iron wool is contaminated and thus discarded.
Spent developer reverts to coal tar and the alkali solution is neutralized by the chlorine which is an acid. Fact is, home darkrooms contribute a thimble full of effluent and this no impact. It is the commercial photo labs that municipalities are worried about. Factorial: There is a fact that ordinary households (no photo lob activity) contribute a surprisingly high level of silver to the waste stream. The source is unknown. In many cases, the silver content will be at or above the 5mg federal standard.
I was a registered environmental assessor licensed in California for photo effluent.
Ok, so are you saying I should just not worry about it? Or are you saying I should use the steel wool and then throw both the liquid down the drain and the wool in the trash?
It kind of sounds like you're saying it doesn't matter and I'm making a mountain out of a molehill.
Hmm... that's what I get
out of it...
The fluid that exits a well operated iron or steal wool recovery system will test 1mg to 1/2 mg silver. 1 mg is the weight of a 1/1000 of a raisin. This will be further diluted by your household sewer water, nobody can detect it, it will do no harm unless you are handling 100 rolls or more a day. The iron wool contains silver that is about 30% pure. It has value and most municipalities will not permit disposal in garbage. You need to sell it to a silver recovery firm or take it to a hazardous collection point. The remainder of the photo effluent is harmless even if you are processing color film. Hazzard is in the eye of the beholder. Many municipalities will say no thank you because they don't know what they are dealing with. You can bottle all this stuff and take it to a hazard's collection site. Me, If I am process under 10 rolls of film a day, don't give this another thought. Photo effluent is low on the toxic scale because acids and bases comingle and net result is neutrality.
Ok, so use the steel wool in a bucket and pour the spent fixer backlog into the bucket through the steel wool and maybe cover for a few days then I can throw away the liquid. For the future if I don’t do more rhan the occaisonal roll I could just pour it down the drain. Then look for a silver recovery company to get rid of the silverized wool.
Methinks the Horse is...........
I'm just guessing on this, but after decades in a jug I doubt that any thiosulfate is left (this is the active ingredient in fixer that "holds" the silver). My guess is that you have a sludge in the bottom of your jugs that includes nearly all of the silver as either metallic silver or silver sulfide. If this is the case, then you are not gonna be "recovering" any significant silver with steel wool nor with electrolytic means; in essence the silver is already "recovered" in the sludge. But again, I'm just guessing; the bulk of my experience has been with continuous processes, not chemicals stored for extended periods of time.
If there is any question as to whether the liquid is still viable as a fixer you could decant a little off the top and see if it is capable of clearing a small piece of unexposed film leader. If it can't do this then there's not much likelihood that it is still holding any silver in suspension.
I will assume you are processing 35mm wide film. A 24 exposure roll less sprocket holes has an area of 0.42 sq. ft. A 36 exposure roll has an area of 0.592 sq. ft. 1000 sq. ft. of 400 ISO film contains 1.1 Troy ounces of silver. Thus one roll of 24 exposure contains about 0.0005 T oz. and a 36 exposure contains 0.0007. Suppose you process 100 rolls of 400 ISO 36 exposure. The film stock for 1000 rolls contains 100 X 0.0007 = 0.07 T oz. When the film is processed, about 60% of this silver will be in the fixer, 40% will make up the image on black & white film. If its color film, 100% will be in the fixer.
OK, how much is 0.07 T oz. = about 2 grams = about 2 resins. Do you think this amount of silver down the drain will harm?
Normally we put steel wool in a plastic container and allow the fixer to trickle in a few drops a minute. About a inch down from the top of the container we cut an exit hole and allow fluid that exits to go down the drain.
This is a chemical reaction based on the activity differences between iron and silver. The silver trades places with the iron and remains as a slugged consisting of silver sulfide. The fluid that exits contains iron in solution.
Reminds me of a high school chemistry experiment. The idea was to put a nail in the solution, which would plate out copper as it dissolved the iron, in the same way as above. For some reason, the cart I had, instead of a nail, had a bag full of tiny iron staples. There is no way to scrape the copper of thousands of staples, so my teacher instead gave me sulfuric acid to dissolve away the rest of the iron. I don't remember now if it came anywhere close to the expected answer, though.
Silver metal, and insoluble salts, don't do much down the drain. Some silver compounds are slightly bad, but not all that bad.
It is industrial sized labs that the sewage people worry about.
Alan, your figures don't add up. You stated:
"The typical roll of 35mm black & white film contains about 0.008 Troy Ounces of silver."
That's around 0.25 grams.
You then go on to say:
"A high volume photofinisher may have a fixer silver loading exceeding 10 grams per liter."
And from your previous figure that would be the entire silver content of 40 rolls of fim.
- Sorry, but I'd like to see the fixing solution that can be used to fix in excess of 40 films without regeneration.10 normally exposed and developed rolls of medium-speed film per litre would be pushing it!
Wait. I see you've now revised the silver content per roll to 0.0007 Troy oz per roll. That makes the capacity of fixer upwards of 450 rolls per litre to get 10 gms of silver in solution. Very doubtful.
In the hay-day of photofinishing I oversaw 7 giant photo labs, each sized to develop and print 20,000 rolls of film a day. Sizing is for holiday loading like Xmas volumes. Anyway, a photofinisher uses electrolytic to reduce the silver loading of the fixer to 1 gram per liter. If set lower, the silver in the electrolytic device sulfurizes. The fixer in the working tanks are replenished. If on silver recovery is utilized, the loading in those tanks can reach 10 grams per liter. Historically, when silver was under $3 per troy ounce and with no government regulation few practiced silver recovery. I have seen the stainless steel tanks with 1/2 to 3/4 inch coats of silver after years of operation. After you process several rolls, dip a shiny penny halve way submerged in the fixer. In minutes, silver will plate, because the top half is not submerged, you will be amazed at the difference top and bottom.
My number of bottles is what I remember, but they’re smaller. I probably have about a gallon of spent fixer (which I typically use 3-4 times) in bottles which may be over a decade old at this point. I sent an email to my county waste disposal and if they reply, I will post.
Obviously, if you’re not mechanically inclined to make some way to trickle the fixer onto that steel wool and just pour it in, it won’t be as effective based on what I’m hearing. I suspect that I may take up the county to dispose of it if that turns out to be possible (just in case and because I’m not really sure I have a smaller problem with a smaller amount of silver sludge). In the meantime, I still find it all fascinating and plan to keep listening.
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