An electrolytic plating silver recovery unit is more complex than a silver recovery cartridge, but it is actually much easier to operate and control than the processing machines that generate the used solutions. The initial cost is higher than a cartridge; however, the cost is not exorbitant and the electrolytic plating unit should be considered as the primary means for recovering silver from fixers and bleach fixers. Navy imaging facilities are not charged for silver recovery equipment. Procedures for obtaining silver recovery equipment are located in the Defense Reutilization and Marketing Manual (NOTAL), DoD 4160.21-M.
The electrolytic plating method of silver recovery uses two electrodes: a cathode and an anode. They are placed in the silver bearing solution and an electric current is passed between them, causing almost pure silver to plate onto the cathode (fig. Al-2). The silver recovery capacity of the unit is determined by the direct current density and the size of the cathodes; that is, (amperes) in relation to the surface area of the cathode.
Tank size is another measure of recovery capacity. Smaller tanks have less plating capacity because of a proportionately smaller cathode surface area. Agitation
An agitation or recirculation system provides a continuous supply of silver-laden solution to the cathode. Without this system, the current density would become too high for the amount of silver present in the solution near the cathode and result in the formation of silver sulfide. This silver sulfide decreases the efficiency of the unit.
The cathodes in various electrolytic plating units vary in design. Some units have a simple flat plate; others may have several circular disks mounted on a shaft or use a rotating cylinder (fig. Al-3). Cathodes are made of metal and there are two types: flexible and nonflexible. The flexibility of the cathode makes it easy to remove the silver flake. Those cathodes that are not flexible can be tapped lightly on a flat surface to remove
Figure AI-2.-Electrolytic recovery unit.
the silver flake, or the flake can be scraped off with a small putty knife.
SILVER RECOVERY FROM SCRAP FILM AND PAPER
The silver that remains in black-and-white film and paper after processing can also be recovered when the film and paper become scrap. When an imaging facility has a sufficient amount of black-and-white scrap, the value of the silver in it can be substantial.
Recovering silver from black-and-white film and paper scrap is more difficult than from solutions. This process requires equipment beyond the scope of Navy imaging facilities. Two factors make silver recovery difficult. First, the base must be removed; second, the silver is not in solution. Two basic methods are used to recover silver from scrap film and paper. One method is to burn the scrap, leaving a silver-rich ash. The other method is to remove the silver by a wet-chemical treatment. Both methods require further steps to separate the silver from the ash or the chemical solution.
The need to recover as much silver as possible has caused the Department of Defense (DoD) to set up a precious metals recovery program.
Figure AI-3.-Electrolytic unit with a rotating cathode.
PRECIOUS METALS RECOVERY PROGRAM
Within DoD there is a continuing requirement for precious metals in the manufacture ofdefense materials. Because of the diminishing supply of these precious metals from domestic sources and an effort to reduce the procurement cost of equipment containing precious metals, it has become necessary for DoD to establish a Precious Metals Recovery Program (PMRP). As a Photographer's Mate, you should be concerned with the recovery of silver. The requirements of the PMRP are set forth in the Navy Precious Metals Program,
NAVSUPINST 4570.23. Participation in the PMRP by all Navy imaging facilities is mandatory.
The Defense Reutilization and Marketing Service, Battle Creek, Michigan, is responsible for programs associated with the collection, recovery, and processing of precious metals. Navy imaging facilities turn in all silver or silver-bearing materials to their local Defense Reutilization and Marketing Office (DRMO). This may include scrap film and paper, used fixer, exhausted silver recovery cartridges, silver sludge, and silver flakes from electrolytic recovery units.
OBTAINING SILVER RECOVERY SUPPLIES AND EQUIPMENT
Requests for PMRP supplies, such as silver test paper, plastic collection containers, silver recovery cartridges, fittings, control valves, and replacement parts peculiar to silver recovery equipment, should be coordinated with your local DRMO. Personnel in DRMO will assist you in obtaining recovery equipment to start up silver recovery operations or to enhance the effectiveness of your current silver recovery operation. Arrangements can then be made for a facility survey to determine the specific requirements for on-site recovery equipment.
The manner in which a Navy imaging facility handles silver-bearing solutions, exhausted recovery cartridges, and silver sludge or flake is subject to security requirements outlined by local authority. As a minimum, however, the following security measures are suggested:
9 Silver that has a high degree of purity should be stored in a safe or locked cabinet within a locked room. Bulky silver-bearing material, such as fixer and scrap film and paper, should be stored in a locked room.
9 The weighing and measuring of silver-bearing materials should be accomplished by a designated weigher in the presence of a disinterested person and the initials of both persons should appear on the weight or inventory documentation.
NOTE: The same disinterested individual should not be permitted to sign for more than two consecutive accountings.
0 Entry to an area where silver with a high degree of purity is stored temporarily should be restricted to a select group of personnel. Their names should be posted on an access list that is kept current, limited to people with a "need to know," and posted inside the entrance. Visitors with a "need to know" who are granted access be accompanied by an individual on the access list and be required to sign a register. Personnel on the access list do not require a security clearance.
Persons entering areas where silver or silver-bearing material is stored should be made aware of "condition of entry" by signs located inside the entrance to the storage area.