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Q: Silver Recovery from X-Ray Film ( No Answer,   2 Comments )
Question  
Subject: Silver Recovery from X-Ray Film
Category: Science > Chemistry
Asked by: leefr-ga
List Price: $100.00
Posted: 07 May 2006 04:20 PDT
Expires: 06 Jun 2006 04:20 PDT
Question ID: 726251
Dear Researchers,

I am seeking an accurate and detailed definition for the process
of recovering silver from processed X-Ray films.
To get you started I post a nice fee and I will contribute another tip
if the answer comes quick enough.
I intend to purchase a refining machine from CPAC, So you can assume
it is in possession. Also assume very large quantities of Film.
What I have learned so far:
There are two possible processes which interest me, first one is to
run a bleach-fix solution through film and process the solution.
Second option is to lay the film in a bleach solution and then wash it
with water and run it through a fixer solution which is then
desilvered.
What I am trying to do is come up with accurate cost for the entire
process (you don't need to refer to transportation of the film). From
you I don't need the costs of machines and materials, but I do need an
exact chemicals list and machines involved in the process as well as
structures (like a bath for the film to sit in).
Please fill in the details for the two alternatives given above.
Good luck and happy research.

Lee
Answer  
There is no answer at this time.

Comments  
Subject: Re: Silver Recovery from X-Ray Film
From: seavun-ga on 23 May 2006 23:18 PDT
 
i think it is useful to you.

1.Silver recovery from synthetic photographic and medical X-ray
process effluents using activated carbon

Adsorption of silver from synthetic photographic and spent fix
solutions on granulated activated carbon in a batch process has been
investigated. The synthetic solutions prepared had similar properties
to medical X-ray and photographic process effluents. Sodium and
ammonium thiosulfates are the major lixiviants used in the dissolution
of silver halides present in photographic and medical X-ray films. The
resultant solutions contain substantial amounts of recoverable silver
complexes in the form of thiosulfates. The as received carbons were
alkaline in nature when contacted with deionised water. These carbons
showed very low silver recoveries. However, when these carbons were
pre-treated with 0.5 mol/dm3 sulphuric and nitric acids at 25 C, it
had resulted in significant silver recoveries of 98.5% and 95% from
sodium and ammonium thiosulfate solutions, respectively. These results
were achieved in a narrow range of pH between 3 and 4. Batch
atmospheric stripping of adsorbed silver by 2.0 mol/dm3 HNO3 at 85 C
was also investigated.


Conclusions
The use of synthetic spent fixing solutions have highlighted the
potential of recovering silver from the medical X-ray and photographic
process effluents using activated carbon under acidic conditions. High
silver adsorptions and recoveries in thiosulfate solutions were
observed when carbon was pre-treated using the 2 mol/dm3 HNO3 and
H2SO4 at 25 C, respectively. The high silver recoveries were observed
when the pH of solutions was maintained between 3 and 4.

HNO3 and H2SO4 pre-treatment of carbon probably resulted in the
formation of nitrogen and sulfur groups that resulted in the improved
silver recoveries of 98.5% and 91% in STS and ATS, respectively. The
silver adsorptions under the alkaline conditions indicated very low
silver recoveries of usually less than 15%. This shows that silver
adsorptions in thiosulfate solutions are pH dependent. The  ions were
seen to have no influence on both the adsorption and elution of
silver. The presence of excess  and Na+ ions were observed to improve
silver desorption.

The silver concentration in eluate was increased by threefold from 500
to 3250 mg/dm3. This indicates the objective of this work with its
potential to purify and concentrate silver from large volumes of
medical X-ray and photographic process effluents into small workable
volumes as pregnant liquors bearing very high silver concentrations.
The AgNO3 electrolyte is considered for its ease in handling during
subsequent recoveries via precipitation or electrolysis and is also
thermodynamically stable at low pH and Eh than the silver thiosulfate
electrolytes.

2. novel angular geometry for the sonochemical silver recovery process
at cylinder electrodes
In order to obtain maximum ultrasonic effect upon electrochemical
silver recovery, mass transfer measurements were investigated. The
effect on limiting current of changing the position of an ultrasonic
horn tip (i.e. vertical and horizontal) and using a cylinder electrode
(CE), was studied in an attempt to find the optimum position required
for maximum sonoelectrochemical effect. The importance of the
ultrasonic intensity, the electrode-horn distance and positioning
(angle) in assigning limiting currents was also investigated. For the
CE placed at an angle of 45 with respect to the ultrasonic horn, it
was suggested that the 50% increase in limiting current for the
?face-on? geometry is caused by an approximately 50% decrease in
diffusion layer thickness for the ?face-on? geometry compared to the
?angular? geometry due to the difference in the sonicated areas for
both geometries.


best wishes

seavun
Subject: Re: Silver Recovery from X-Ray Film
From: leefr-ga on 06 Jun 2006 16:30 PDT
 
Thank you seavun,

Good comment.
It is a bit too much of chemistry for me though :-)
I have been able to draw an accurate scheme for the process during the past month.
It seems I will start an X-Ray recycling business within a short while.
Maybe in the future I could use your vast knowledge, you can try and
contact me at leefrankel@hotmail.com if it is of interest to you.

All the best,
Lee

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