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WO1993003417A1 - Regeneration de fixateur d'agent de blanchiment - Google Patents

Regeneration de fixateur d'agent de blanchiment Download PDF

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Publication number
WO1993003417A1
WO1993003417A1 PCT/CA1992/000324 CA9200324W WO9303417A1 WO 1993003417 A1 WO1993003417 A1 WO 1993003417A1 CA 9200324 W CA9200324 W CA 9200324W WO 9303417 A1 WO9303417 A1 WO 9303417A1
Authority
WO
WIPO (PCT)
Prior art keywords
solution
bleach fixer
silver
bleach
sulfite
Prior art date
Application number
PCT/CA1992/000324
Other languages
English (en)
Inventor
Michael E. Dutka
Paul H. Whitney
Keith E. Malcolm
Original Assignee
Technology Transfer Barbados Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Technology Transfer Barbados Inc. filed Critical Technology Transfer Barbados Inc.
Publication of WO1993003417A1 publication Critical patent/WO1993003417A1/fr

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C7/00—Multicolour photographic processes or agents therefor; Regeneration of such processing agents; Photosensitive materials for multicolour processes
    • G03C7/30—Colour processes using colour-coupling substances; Materials therefor; Preparing or processing such materials
    • G03C7/44—Regeneration; Replenishers
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C5/00—Photographic processes or agents therefor; Regeneration of such processing agents
    • G03C5/26—Processes using silver-salt-containing photosensitive materials or agents therefor
    • G03C5/395—Regeneration of photographic processing agents other than developers; Replenishers therefor
    • G03C5/3952—Chemical, mechanical or thermal methods, e.g. oxidation, precipitation, centrifugation

Definitions

  • hydrosulfide reagent to precipitate silver sulfide (Ag 2 S) from spent photographic bleach fixer solutions.
  • the reagent provides a source of water soluble hydrosulfide ions (HS) .
  • reaction of the HS with bleach fixer solution containing silver results in precipitation of Ag 2 S, while regenerating the thiosulfate in the bleach fixer solution. This enables recycling of the bleach fixer solution.
  • regenerating the thiosulfate in the bleach fixer solution This enables recycling of the bleach fixer solution.
  • bleach fixer from colour photo processing, it is preferred to adjust the pH and sulfite levels following silver removal to complete the regeneration process.
  • Silver recovery from the spent fixer solution used to develop various types of photographic films, including black and white, colour and X-ray films, is done for economic
  • Silver is currently recovered from the bleach fixer solution usually using a two stage electrolysis followed by either metallic replacement using cartridges filled with iron wires, or ion exchange to remove residual silver.
  • Electrolysis is costly in capital outlay and in operating costs. The silver recovery is low and environmental problems remain from disposal of the effluent solution. Electrolytic plating allows for some bleach fixer recycling, but electroplating causes a lowering of the pH of the bleach fixer solution and consumption of both sulfite and thiosulfate resulting in a decrease 5 in the fixation rate and the amount of silver that can be stripped from the film.
  • H 2 S poisonous hydrogen sulfide
  • the silver product can then be converted to metallic silver by heat treatment in an air atmosphere at 600°C or by dissolution in nitric acid.
  • a process is provided for the regeneration of a
  • the process comprises introducing a hydrosulfide
  • the resultant precipitate is isolated from the spent bleach fixer solution. Sufficient silver is thereby removed from the spent bleach fixer solution and sufficient thiosulfate is regenerated to enable recycling of the bleach fixer solution.
  • regenerating bleach fixer from colour photo processing, it is preferred to adjust the pH and sulfite levels following silver removal to complete the regeneration process.
  • the process is particularly suited for treating spent photographic bleach fixer solutions which contain thiosulfate and in particular sodium or ammonium thiosulfate.
  • the hydrosul ide reagent is preferably either sodium, potassium or ammonium hydrosulfide.
  • the hydrosulfide reagent precipitates silver in the form of silver sulfide while regenerating thiosulfate levels in the bleach fixer.
  • pH and sulfite levels are adjusted, by adding an acid solution and sulfite ions (S0 3 ) , added as a sulfite salt, following the regeneration process. A sufficient amount of an acidic solution and sulfite ions are added to the treated bleach fixer to restore the pH and sulfite ion concentration to within the operating ranges of the original bleach fix solution.
  • sufficient acid solution is added to maintain the pH of the regenerated bleach ixer from about 5.0 to about 5.5.
  • sufficient sulfite ions are added to maintain sulfite levels from about 4 g/L to about 10 g/L.
  • Figure 1 charts the daily densitometer quality control readings for maximum and minimum density, red, green, blue and black during 10 use and regeneration cycles.
  • Figure 2 shows the concentration of sulfur compounds in the bleach fixer through 10 use and regeneration cycles.
  • Figure 3 shows pH of the bleach fixer through 10 use and regeneration cycles.
  • Figure 4 shows the concentration of silver and iron in the bleach fixer through 10 use and regeneration cycles.
  • Figure 5 shows the molar ratio of moles of the hydrosulfide reagent used per moles of silver removed through 10 use and regeneration cycles.
  • Figure 6 shows the molar comparison of the moles of hydrosulfide reagent used and the moles of silver removed from the spent bleach fixer through 10 use and regeneration cycles.
  • Figure 7 shows the concentration of sodium and potassium through 10 use and regeneration cycles.
  • Figure 8 shows the ammonia concentration in the bleach fixer through 10 use and regeneration cycles.
  • the photographic processing of colour prints involves the development of an image by decomposition of silver halide crystals to metallic silver and the removal of the unused silver halides from the paper.
  • the most common form of photographic bleach fixer solution used in the printing of colour photographs contain a reducing agent, usually a form of ferric EDTA, and an ammonium thiosulfate component to act as a silver solvent. After use, therefore they include silver thiosulfate complexes which, in accordance with this invention, may be precipitated from the spent bleach fixer solution by use of the hydrosulfide reagent.
  • bleach fixer solution bleach fixer solution which has been used for fixing a color image on paper.
  • the thiosulfate-based bleach fixer solutions for example, sodium thiosulfate and ammonium thiosulfate are commonly used in photographic bleach fixer solutions.
  • the time required to dissolve residual silver halides is related to the concentration of available thiosulfate in the bleach fixer solution.
  • the silver halide, as removed from the paper forms silver thiosulfate complexes such as AgNaS 2 0 3 or AgNH 3 S 2 0 3 , the build up of which delays the removal of residual silver from the paper. It is therefore important to remove silver from the bleach fixer solution to ensure sufficient concentration of the uncomplexed thiosulfate to expediently clean the paper during the fixing process.
  • a hydrosulfide reagent which provides a source of hydrosulfide ions reacts with the various silver thiosulfate complexes to produce silver sulfide without significantly degrading the thiosulfate component of the bleach fixer solution.
  • hydrosulfide reagents include: sodium hydrosulfide, potassium hydrosulfide or ammonium hydrosulfide.
  • the sulfite level by adding a source of soluble sulfite in sufficient quantity to restore the concentration of the sulfite ions to within the normal operating range of the original bleach fix solution.
  • a source of soluble sulfite in sufficient quantity to deliver between 4 and 10 grams per litre of bleach fixer treated.
  • the operating range of sulfite ions in individual manufacture's bleach fix solutions may vary and can easily be determined by semi- quantitative analyses.
  • Sulfite is easily adjusted through the addition of 5 to 10 grams of a soluble sulfite powder, in the form of a soluble sulfite salt, per litre of bleach fixer to the processor replenishment tank while providing sufficient agitation to ensure that the powder dissolves in the solution.
  • Suitable sources of soluble sulfite salt include for example: sodium sulfite, ammonium sulfite, potassium sulfite, sodium bisulfite, ammonium bisulfite, sodium meta bisulfite, and potassium meta bisulfite.
  • bleach fix solution During the processing of photographic prints using bleach fix there is a rise in the pH of the bleach fix solution.
  • adjust the pH by adding a sufficient amount of an acidic solution to return the pH of the bleach fix solution to within the normal operating pH range for that specific bleach fix.
  • it is preferred to adjust the pH by adding a sufficient quantity of an acidic solution to adjust the pH to a range from about 5.0 to about 5.5.
  • the pH operating range of individual manufacture's bleach fix solutions may vary and can easily be determined by semi-quantitative analyses.
  • the pH is easily adjusted by the addition of small quantities of an acidic solution.
  • concentration of the acidic solution is not critical. Any suitable solution can be used provided that the addition of the acid solution does not substantially effect the overall volume of the treated fixer.
  • Suitable acidic solutions which can be used to adjust the pH include for example a 50% (vol/vol) solution of acetic acid. This should be added in an amount of approximately 1% by volume of the amount of bleach fixer being regenerated.
  • acetic acid is the acid of choice for use in the photo processing industry, sulfuric may also be used.
  • Other acidic solutions may be suitable provided that they do not interfere with the photo processing procedure.
  • the bleach fixer solution as treated in accordance with this invention, may be recycled for use as a bleach fixer solution in the photographic development process.
  • the spent bleach fixer solution with a portion of the silver removed therefrom had to be discarded because, in the process of recovering the silver, the thiosulfate component was degraded into compounds which could not be recycled and the ferric EDTA was not returned to a form which could be reused as a reducing agent.
  • the hydrosulfide reagent as used to treat the bleach fixer solution is readily available as a concentrate or in its dehydrated form.
  • sodium hydrosulfide is available commercially as a 47.5% concentrate solution which can be readily diluted to the desired concentration, for use, such as a two molar solution.
  • Sodium hydrosulfide may also be commercially obtained as a hydrated salt in the form of NaHS • 0.89 H 2 0. This salt may be dissolved in water to provide the desired concentration of solution such as a two molar solution.
  • the sodium hydrosulfide may be prepared by reacting H 2 S gas with sodium hydroxide.
  • potassium hydrosulfide and ammonium hydrosulfide may be prepared by reacting a solution of potassium hydroxide (KOH) or ammonium hydroxide, respectively with hydrogen sulfide (H 2 S) gas.
  • the hydrosulfide reagents will dissociate to provide water soluble hydrosulfide ions.
  • the silver is complexed with the thiosulfate, it is believed that the hydrosulfide ions, in one manner or another, react with the various silver thiosulfate complexes to produce silver sulfide.
  • the silver sulfide is not soluble; hence it precipitates and forms a mass which may be easily filtered or readily settles out of solution.
  • the hydrosulfide reagent in this particular equation preferentially reacts with the silver thiosulfate complex (here shown as sodium thiosulfate) and does not react in any significant way with other components of the bleach fixer solution.
  • sodium hydrosulfide will also react with sodium thiosulfate, this reaction is minimized because of the preferential reaction of sodium hydrosulfide with the silver sodium thiosulfate. It has been found that excessive amounts of sodium hydrosulfide, if introduced into the spent bleach fixer solution, will react with the sodium thiosulfate to degrade the thiosulfate to elemental sulfur, which is not desirable.
  • hydrosulfide reagent in excess of 2 moles per mole of silver in the bleach fixer solution results in increasing degradation of the thiosulfate and sulfite ions.
  • the preferred range of hydrosulfide reagent added to the spent bleach fixer solution is approximately 1.0 moles to 2.0 moles per mole of silver in the bleach fixer solution.
  • the rate of introduction of the hydrosulfide reagent to the bleach fixer solution is the rate of introduction of the hydrosulfide reagent to the bleach fixer solution and the degree of agitation of the solution. It is preferred that the rate of introduction of the hydrosulfide reagent to the spent bleach fixer solution be at a rate which is slow enough, depending upon the conditions, to avoid evolution of H 2 S gas. Hence the rate of introduction of the hydrosulfide reagent may vary considerably depending upon the degree of agitation of the bleach fixer solution. These parameters are related. Normally if the rate of introduction is increased, then correspondingly the degree of agitation of the bleach fixer solution must also be increased. Providing the degree of agitation is high enough to avoid formation of pockets of hydrosulfide reagent, the rate of introduction thereof may be correspondingly higher.
  • the bleach fixer solution should preferably be agitated.
  • the degree of agitation contemplated is that produced by a mechanical ultrasonic or gas bubbling means. Mechanical stirrers, recirculating pumps, ultrasonic stirrers, ultrasonic vibration devices or gas bubbles through the system create sufficient agitation to ensure good mixing of the introduced hydrosulfide with the bleach fixer solution to eliminate any pockets of high concentration of the hydrosulfide reagent and thereby ensure that the preferential reaction with the silver complex proceeds.
  • the rate of introduction of the reagent is selected to be in step with the degree of agitation.
  • the desired degree of agitation can be established by experimentation with a particular bleach fixer solution.
  • the bleach fixer solution may be circulated through the reaction vessel at a rate of approximately 8 to 10 litres per minute. This establishes a substantial degree of agitation in the 50 litre reaction vessel.
  • the circulation rate of the bleach fixer solution may be achieved by a suitable pump, such as a diaphragm pump which is not corroded by the bleach fixer solution.
  • the solution may be withdrawn from the bottom of the tank and returned to the side of the tank through a suitable nozzle.
  • the solution may be circulated at a pressure of 40 to 60 psi.
  • the nozzle may be approximately one quarter inch in diameter to provide for a high speed injection of the bleach fixer solution into the tank.
  • the rate of injection of the hydrosulfide reagent may be in the range' of 2 to 3 ml per second.
  • Sufficient hydrosulfide reagent is injected into the tank at this rate until a desired molar ratio of hydrosulfide reagent to silver in the spent bleach fixer solution is in the range of 1.0 to 2.0.
  • the hydrosulfide reagent is injected adjacent the nozzle so that the reagent is swept immediately into the high speed stream of the bleach fixer solution to provide for immediate dispersal of reagent and to avoid the formation of pockets of high concentration of the reagent.
  • the nozzle may be angled within the vessel to encourage a swirl flow of the bleach fixer solution .in the vessel.
  • the invention contemplates the use of other hydrosulfide reagents i.e. compounds which provide hydrosulfide ion to the bleach fixer solution.
  • potassium hydrosulfide or ammonium hydrosulfide may also be used in converting silver as it exists in spent bleach fix solutions as used in the colour print processing industry.
  • the temperature of the bleach fixer solution does not have a direct bearing on the precipitation of silver from the bleach fixer solution. Therefore, for convenience, the process may be carried out at room temperature.
  • the silver precipitate in the form of Ag 2 S salt forms readily and has Very good settling and filtration characteristics.
  • the process is very effective in treating bleach fixer solutions and the use of the hydrosulfide reagent does not degrade, to any appreciable extent, the thiosulfate in the solution.
  • the method according to the present invention thus permits the treated bleach fixer solution to be recycled readily for reuse in the photographic development process. This prevents significant problems presently encountered with regards to disposal of the spent bleach fixer solution, avoiding pollution problems normally occurring in disposal of spent bleach fixer solutions to municipal treatment systems.
  • the silver may be recovered from the precipitate by a number of methods known in the art.
  • the precipitate may be calcined at temperatures ranging from 300°C to 600°C to convert silver sulfide to silver.
  • the silver can be recovered by dissolving the precipitate in nitric acid, or by using conventional smelting and refining techniques.
  • it may be necessary to add a small portion of fresh bleach fixer solution, in the form of a bleach fixer solution prepared ready for use or as a bleach fixer concentrate, to replenish the volume of bleach fixer, after repeated regeneration cycles.
  • the addition of bleach fixer concentrate or prepared bleach fixer solution serves to adjust the sulfite level and pH in addition to providing ferric EDTA to make up for losses due to carry-over of bleach fixer into the wash water during processing.
  • Example 1 illustrate the best modes contemplated for carrying out this invention, but are not to be construed as limiting.
  • Regeneration and reuse of the regenerated bleach fixer was repeated for ten cycles.
  • the testing was conducted using 150 litres of fresh bleach fixer solution. The testing was done under actual operating conditions. The testing was conducted during normal operations using a Hope model RA4226V Print Processor.
  • the bleach fixer used was Kodak Ektacolour RA Bleach Fix.
  • the fresh bleach fixer was prepared according to the manufacturer instructions and introduced to the replenishment tank. Following use in the processor, the first regeneration cycle took place approximately one week later. Regeneration thereafter took place every week to ten days as needed by volume use.
  • the bleach ixer solution was loaded with silver under normal operating conditions, using Kodak Ektacolor Supra Type N paper, until it reached approximately 4 grams per litre and was discharged via the processor overflow to a receiving vessel.
  • the bleach fixer solution was then transferred to a TTI CF-50 Rejuvenator and the silver was converted to silver sulfide by the addition of a hydrosulfide reagent and removed in two 40 litre batches.
  • the filtered bleach fix was transferred to the processor replenishment tank where sulfite and pH adjustment was conducted.
  • Total sulfur was measured by oxidizing the sulfur species to sulfate using hydrogen peroxide and measuring sulfur by inductively coupled plasma.
  • the thiosulfate was titrated with iodine after sulfide was precipitated and bisulfite was masked with formaldehyde using the method described by Kolthoff and Belcher in "Volumetric Analysis III, 1957, page 294.
  • Total sulfur rose through the ten regeneration cycles, largely due to the addition of fresh bleach fixer and sulfite (Figure 2) .
  • Sulfide decreased roughly by half between regenerations with no discernable quality change to the print image.
  • Thiosulfate showed less than five percent loss before the addition of fresh bleach fix necessary to make up for evaporation loss ( Figure 2) .
  • the pH was determined for all samples taken throughout the 10 regeneration cycles ( Figure 3) .
  • the pH of the solution increased during its residence in the processor. It was very easily controlled by the addition of small quantities of 50% acetic acid.
  • the addition of a 1% volume based on the total regenerated fix volume was sufficient to maintain proper pH control from cycle 3 to the end of the test.
  • the addition of 50% acetic acid was done in the replenishment tank after the addition of sulfite by manually pouring in the determined amount while agitating with a hand held laboratory stirring propellor.
  • the pH control proved to be an essential feature for the continued regeneration and reuse of the bleach fix.
  • the concentrations of silver, sodium, potassium, aluminum, and iron were analyzed using an Applied Research Laboratories Model 34000 inductively coupled plasma atomic emission spectrometer (ICP) .
  • Sodium and potassium show regular and steady increase over the 10 cycles ( Figure 7) .
  • Sodium increased due to the addition of reagent during regeneration and due to the addition of sodium sulfite to maintain sulfite levels.
  • Potassium increased during residence in the processor due either to developer carryover or dissolution from the print paper.
  • these ions have a high solubility in bleach fixer and the increasing concentrations did not show any negative effect on image fixation at these levels.
  • pH and sulfite concentration control is required for the regeneration of bleach fixer.
  • optimum pH and sulfite ion concentration was accomplished by the addition of acetic acid and sodium sulfite.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)

Abstract

On décrit un procédé de régénération d'un fixateur d'agent décolorant résiduaire par récupération de sulfure d'argent d'une solution résiduaire. Ledit procédé convient notamment au traitement de la solution de fixateur d'agent décolorant de manière à permettre le recyclage de cette solution, ce qui donne lieu à une réduction considérable de son coût et de la pollution de l'environnement. Le procédé consiste à introduire un réactif d'hydrosulfure dans la solution de fixateur d'agent décolorant, contenant de l'argent, afin de précipiter le sulfure d'argent tout en maintenant les niveaux de pH et d'hyposulfite dans le fixateur d'agent décolorant pour pouvoir le réutiliser. La précipitation est isolée de la solution de fixateur d'agent décolorant afin d'en retirer l'argent et, à partir de là, de permettre le recyclage de ladite solution. Il est préférable d'ajuster les niveaux de pH et de sulfure après avoir retiré l'argent afin d'achever le processus de régéneration.
PCT/CA1992/000324 1991-08-09 1992-08-04 Regeneration de fixateur d'agent de blanchiment WO1993003417A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US74308691A 1991-08-09 1991-08-09
US743,086 1991-08-09

Publications (1)

Publication Number Publication Date
WO1993003417A1 true WO1993003417A1 (fr) 1993-02-18

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PCT/CA1992/000324 WO1993003417A1 (fr) 1991-08-09 1992-08-04 Regeneration de fixateur d'agent de blanchiment

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WO (1) WO1993003417A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1545032A (en) * 1925-07-07 Process op secoveeing silver
JPS55161035A (en) * 1979-06-04 1980-12-15 Konishiroku Photo Ind Co Ltd Silver recovering method for bleach-fix bath
WO1990008980A1 (fr) * 1989-02-01 1990-08-09 Eastman Kodak Company Kit de regeneration de compositions de blanchiment-fixation et son utilisation dans le traitement photographique

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1545032A (en) * 1925-07-07 Process op secoveeing silver
JPS55161035A (en) * 1979-06-04 1980-12-15 Konishiroku Photo Ind Co Ltd Silver recovering method for bleach-fix bath
WO1990008980A1 (fr) * 1989-02-01 1990-08-09 Eastman Kodak Company Kit de regeneration de compositions de blanchiment-fixation et son utilisation dans le traitement photographique

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
DATABASE WPIL Week 8108, Derwent Publications Ltd., London, GB; AN 81-12613D & JP,A,55 161 035 (KONISHIROKU PHOTO KK) 16 December 1980 *
F.ALBERT COTTON 'advanced inorganic chemistry' 1962 , INTERSCIENCE (JOHN WILEY AND SONS) , LONDON *
JOURNAL OF IMAGING TECHNOLOGY vol. 10, no. 6, December 1984, SPRINGFIELD US pages 212 - 216 T.N.HENDRICKSON ET AL *

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