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WO1990001077A1 - Procede de precipitation electrolytique pour la recuperation de metaux - Google Patents

Procede de precipitation electrolytique pour la recuperation de metaux Download PDF

Info

Publication number
WO1990001077A1
WO1990001077A1 PCT/US1989/002429 US8902429W WO9001077A1 WO 1990001077 A1 WO1990001077 A1 WO 1990001077A1 US 8902429 W US8902429 W US 8902429W WO 9001077 A1 WO9001077 A1 WO 9001077A1
Authority
WO
WIPO (PCT)
Prior art keywords
silver
sulfide
cathode
metal
process according
Prior art date
Application number
PCT/US1989/002429
Other languages
English (en)
Inventor
George A. Lorenzo
Curtis O. Rhodes
Susan M. Grube
Original Assignee
Cpac, 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 Cpac, Inc. filed Critical Cpac, Inc.
Publication of WO1990001077A1 publication Critical patent/WO1990001077A1/fr

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
    • C02F1/4676—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electroreduction
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G5/00—Compounds of silver
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B11/00—Obtaining noble metals
    • C22B11/04—Obtaining noble metals by wet processes
    • C22B11/042—Recovery of noble metals from waste materials
    • C22B11/046—Recovery of noble metals from waste materials from manufactured products, e.g. from printed circuit boards, from photographic films, paper or baths
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
    • C02F2103/40—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32 from the manufacture or use of photosensitive materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • Electrolysis procedures have also had the further problem of producing undesirable, and in some instances, dangerous amounts of volatile gases, such as sulfur dioxide, hydrogen sulfide, and ammonia.
  • volatile gases such as sulfur dioxide, hydrogen sulfide, and ammonia.
  • spent photographic processing solution is in the form of soluble thiosulfate and/or sulfite compounds; and during the electrolytic process, the reaction conditions are chosen to produce insoluble silver sulfide without any substantial formation of silver metal. Preferably, the reaction conditions are also chosen to keep the formation of undesirable volatile gases, such as sulfur dioxide, hydrogen sulfide, and ammonia at a minimum level.
  • the silver sulfide that is formed during the electrolytic process is precipitated and recovered by filtration to form an effluent that can be safely discarded without violation of current environmental requirements.
  • the effluent contains no more than 1 mg./liter of silver; and, if desired, the silver content of the effluent can be reduced to 0.5 mg./liter of silver and lower.
  • Our electrolytic precipitation process can also be used to recover other metals from solutions, as insoluble metal sulfides, by forming the thiosulfate or sulfite of the metal and operating the electrolytic process to precipitate the metal sulfide, rather than to plate the metal on the cathode. So our electrolytic precipitation process may have practical uses beyond the processing of photographic waste solutions.
  • the process of this invention is pref ⁇ erably used for recovering silver from photographic processing solutions, the process can also be used to recover other metals.
  • the metals present in the solution are preferably in the form of the thiosulfate or sulfite or a combination of the thiosulfate and sulfite; and during electrolysis, the metals should form an insoluble sulfide.
  • Other metals that form insoluble sulfides that may be electrolytically precipitated by our invention are iron, nickel, zinc, copper, tin, lead, and the like.
  • the process of this invention is preferably used to recover silver as precipitated silver sulfide from the waste effluent of "washless" mini-labs
  • the process can also be used to treat concentrated silver-bearing wastes from large photofinishing labs using wash processes.
  • our experience with the invention has involved mostly precipitation of silver sulfide from photographic processing solutions, and partly because this problem presents a good way of explaining our invention, we have chosen photographic waste treatment as representative of processes to which our invention can be applied.
  • the sulfide formation takes place at the cathode. Any metal that may be formed also occurs at the cathode, but the formation of metal is kept to a minimum during the process. For photographic processing solutions, this is done with a current density within the range of 5 to 150 amps/square foot of cathode and a DC voltage preferably within the -J 5 range of 2-10 VDC. The lower the current density and the voltage, the longer the reaction time. At too low a voltage and current density, unwanted silver plating can occur on the cathode; and at very high voltages and current densities, silver sulfide may redissolve. 2o
  • the preferred electrolysis conditions depend upon the spent or used solution that is treated.
  • an anode rod or cylinder is positioned concentrically within a cylindrical cathode; and the cathode-to-anode area ratio is at least 1:1, preferably 2:1 to 4:1 and as high as 8:1.
  • a stainless steel cathode and a carbon anode are preferred, but carbon cathodes can be used; and at high current densities (e.g., 60-150 amps/square foot) , platinized titanium can be used as an anode.
  • An iron (or carbon steel) anode can be used as well. If iron is used, this provides iron ions to react with excess sulfide and helps reduce hydrogen sulfide odor emission.
  • the pH of the electrolysis reaction is within the range of 4-13. At the lower pH levels, undesirable amounts of hydrogen sulfide and sulfur dioxide may form; and at the higher pH levels, too much ammonia may form. It is preferred to use a pH of 6-9 and most preferably about 6-8 to keep the volatile gases at a low level.
  • the pH of the reaction can be controlled by the initial addition of photographic developer or other basic compounds, such as sodium carbonate, sodium sulfite, or sodium hydroxide; or by addition of acidic compounds, such as sulfuric acid, sodium bisulfate, or sodium bisulfite. Temperature controls are not required for elec ⁇ trolytic precipitation, but the temperature usually rises slightly. The temperature can be within the range of 25-50°C, usually 25-30°C.
  • reaction time that is required depends upon the reaction conditions that are used.
  • the desired level of silver in the effluent in the form of soluble salts can be achieved in 1 hour in some instances, but a reaction time of 4 hours or longer may sometimes be needed, depending on the cell configuration, volume and type of solution, and degree of agitation.
  • ferric*EDTA is highly desirable in reducing the amount of hydrogen sulfide that is produced.
  • Spent or used processing solutions from the production of black and white prints do not contain iron salts, such as ferric ⁇ DTA, and the addition of 200 mg./liter or more of iron in the form of ferric ⁇ DTA is very beneficial in reducing the production of hydrogen sulfide.
  • ferric-EDTA is present in the used solutions; and when ferric ⁇ DTA is present, it is preferred to use a high (2:1 or greater) cathode-to-anode area ratio because less current density and less time are required to effect silver sulfide precipitation.
  • the amount of iron that is present affects the rate of the reaction that produces the silver sulfide.
  • the more iron that is present the slower the sulfiding reaction and thus the higher the current density or the higher the cathode-to-anode ratio that is needed.
  • low current densities (10-20 amps/square foot) can be used with high cathode-to-anode area ratios (4:1 or greater).
  • Effluents contain ⁇ ing less than 1.0 mg./liter of silver can be produced in the process, depending upon the extent of the filtration.
  • Filtration can be accomplished with a single passage through a low or sub-micron-rated (0.2 to 5 microns) , pleated filter or by using a series of filters, such as a 5-10 micron filter followed by a 1 micron filter. Best results are obtained by using high porosity filters in series or parallel and allowing the filter cake to build up and become a finer filter.
  • Filtered solution is returned to the electrol- ysis reactor, preferably through a spray bar in the reactor. Recirculating the filtered solution in this manner provides all the agitation that is required during the reaction. Fresh solution is brought to the cathode for reaction, and the insoluble silver sulfide particles are kept suspended in the solution so that they can reach the filter.
  • Example 1 silver was removed as silver sulfide from processing solutions that had been used to make black and white prints.
  • the solution to be processed was prepared by mixing 4 gallons of used black and white developer, 2 gallons of used black and white fix, 14 gallons of water, and 165 ml. of photo-iron (i.e., concentrated ferric*EDTA containing 90 grams/liter of iron) to give a solution 0 containing 200 mg./liter of ferric iron to control the hydrogen sulfide odor.
  • the pH of the mixture was 9.0.
  • the solution containing 363 mg./liter of soluble silver salts, was placed in an electrolytic reactor having a 2 square foot cylindrical cathode made of 5 316 stainless steel 6 inches in diameter and a 0.9 square foot carbon anode rod about 2 inches in diameter placed concentrically within the cathode cylinder.
  • the electri ⁇ cal current that was applied was 20 amps (about 10 amps/square foot of cathode) at 5.1 VDC.
  • the solution was recirculated through a 30 micron filter. After electrolysis, the solution was filtered through the 30 micron filter and then a 5 micron filter to the drain, and the soluble silver content of the solution was measured by atomic adsorption at hourly 5 intervals to give the following results:
  • Example 2 Silver was removed as silver sulfide from 500 ml. of used color film fixing solution containing 78 grams/ _T liter of ammonium thiosulfate, 9.9 grams/liter of sodium sulfite, and 4370 mg./liter of soluble silver salts.
  • the solution was placed in an electrolysis reactor having a carbon anode and a carbon cathode. Each electrode had about 0.015 square feet of area providing a 1:1 area ratio.
  • f During electrolysis, the solution was stirred, but not filtered.
  • the samples taken were gravity filtered through a Whatman 2V filter (about 8 microns) , and the silver content was measured by atomic absorption at 20-minute intervals to provide the following results:
  • Example 3 An electrolysis solution representative of the total waste from a color processing washless mini-lab was prepared by mixing: 20 (a) film developer, 0.157 parts
  • 35 inch diameter stainless steel cathode (0.92 square feet) was used with a 3 inch diameter iron rod (0.45 square feet) .
  • the solution was recircu ⁇ lated through a single filter (20 microns for Run #1; 50 microns for Run #2) .
  • Samples taken for analysis were filtered through a Whatman 2V filter (about 8 microns) , and the soluble silver content was measured by atomic absorption at 1 hour intervals.
  • the cathode current density was about 37 amps/square foot.
  • Example 4 Silver was removed as silver sulfide from 160 ml. of used non-regenerated bleach fix plus low flow wash from color paper processing solution containing 2.4 grams/liter of iron as iron-EDTA. The pH of the solution was adjusted to 13.0 with sodium hydroxide.
  • the solution was placed in an electrolysis reactor having a stainless steel cathode plate and a carbon anode plate.
  • the cathode-to-anode area .ratio was 1:1. Fifteen amps/square foot of cathode were applied, and the solution was stirred without filtering. Samples for analysis were filtered through a Whatman 2V filter (about 8 microns) . The silver content of the solution was measured at 10-minute intervals. pH
  • the production of hydrogen sulfide can be reduced by applying current to the reactor only during the initial stages of the process. The current is shut off, but the solution is stirred and recirculated through a filter. Formation of silver sulfide continues as a result of the contact of sulfide ions with soluble silver. The formation of hydrogen sulfide can also be reduced by applying current to the reactor intermittently but continuing the recirculation of solution through the filter.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Electrochemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Metallurgy (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Manufacturing & Machinery (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Inorganic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Water Treatment By Electricity Or Magnetism (AREA)

Abstract

On récupère l'argent se trouvant dans des produits chimiques de traitement photographique après usage par précipitation électrolytique de sulfure d'argent insoluble provenant de solutions de traitement photographique contenant du thiosulfate d'argent, puis par filtrage du sulfure d'argent provenant du produit de l'électrolyse pour produire un effluent ne contenant pas plus de 1 mg d'argent par litre. On procède à l'électrolyse à une densité de courant comprise entre 5 et 150 amps par pied carré de cathode, une tension de c.c. comprise entre 2 et 10 volts, et un pH compris entre 4 to 13, sans formation ou dépôt sensible de métal d'argent sur la cathode.
PCT/US1989/002429 1988-07-19 1989-06-05 Procede de precipitation electrolytique pour la recuperation de metaux WO1990001077A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US22150288A 1988-07-19 1988-07-19
US221,502 1988-07-19

Publications (1)

Publication Number Publication Date
WO1990001077A1 true WO1990001077A1 (fr) 1990-02-08

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Application Number Title Priority Date Filing Date
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2289058A (en) * 1994-05-06 1995-11-08 Atomic Energy Authority Uk Treating effluent of photographic processes in an electrolytic cell to precipitate silver sulphide and filtering
FR2723594A1 (fr) * 1994-08-11 1996-02-16 Kodak Pathe Procede d'extraction de l'etain de solutions organiques par electrolyse
CN114788698A (zh) * 2021-01-26 2022-07-26 中国人民大学 硫化钠预处理的纳米银碳纤维微电极高选择性检测生物体内的硫化氢的电化学方法
CN114788698B (zh) * 2021-01-26 2025-10-10 中国人民大学 硫化钠预处理的纳米银碳纤维微电极高选择性检测生物体内的硫化氢的电化学方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1937179A (en) * 1933-07-28 1933-11-28 Weisberg & Greenwald Inc Method of recovering silver
US4088552A (en) * 1976-04-19 1978-05-09 Eastman Kodak Company Recovering silver compounds from solutions containing other silver compounds
US4256559A (en) * 1978-05-31 1981-03-17 Teijin Engineering Ltd. Method and apparatus for regenerating spent photographic bleach-fixer solution
US4455236A (en) * 1982-12-20 1984-06-19 General Electric Company Method for removing hydrogen sulfide from aqueous streams

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1937179A (en) * 1933-07-28 1933-11-28 Weisberg & Greenwald Inc Method of recovering silver
US4088552A (en) * 1976-04-19 1978-05-09 Eastman Kodak Company Recovering silver compounds from solutions containing other silver compounds
US4256559A (en) * 1978-05-31 1981-03-17 Teijin Engineering Ltd. Method and apparatus for regenerating spent photographic bleach-fixer solution
US4455236A (en) * 1982-12-20 1984-06-19 General Electric Company Method for removing hydrogen sulfide from aqueous streams

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2289058A (en) * 1994-05-06 1995-11-08 Atomic Energy Authority Uk Treating effluent of photographic processes in an electrolytic cell to precipitate silver sulphide and filtering
GB2289058B (en) * 1994-05-06 1998-05-06 Atomic Energy Authority Uk Silver removal
FR2723594A1 (fr) * 1994-08-11 1996-02-16 Kodak Pathe Procede d'extraction de l'etain de solutions organiques par electrolyse
EP0699955A1 (fr) 1994-08-11 1996-03-06 Kodak-Pathe Procédé d'extraction de l'étain par électrolyse de solutions organiques
US5578191A (en) * 1994-08-11 1996-11-26 Eastman Kodak Company Process for extracting tin from organic solutions by electrolysis
CN114788698A (zh) * 2021-01-26 2022-07-26 中国人民大学 硫化钠预处理的纳米银碳纤维微电极高选择性检测生物体内的硫化氢的电化学方法
CN114788698B (zh) * 2021-01-26 2025-10-10 中国人民大学 硫化钠预处理的纳米银碳纤维微电极高选择性检测生物体内的硫化氢的电化学方法

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