Silver Recovery

Hallmark Refining Corporation is known for its refining capabilities and for innovative design and manufacturing of silver recovery equipment. Hallmark operates as a secondary refiner (TSDR), with a special emphasis on silver from the photographic industry and gold from the electronics industry.

Silver Recovery Technologies

Hallmark Refining offers three technologies to recover silver from silver-rich photographic processing solutions:

• Electrolytic
• Metallic replacement
• Precipitation

Considerable research over a period of years has gone into making these recovery technologies efficient, economical and user friendly.

Electrolytic Recovery

The most widely used silver recovery method for large photo processors is electrolytic, where the silver is recovered from solution by electroplating it onto a cathode. A controlled, direct electrical current is passed between two electrodes suspended in the silver-bearing solution. Silver is deposited on the cathode in the form of nearly pure silver plate.

There are two basic types of electrolytic equipment: one in which the cathode rotates in the solution and one in which the solution is pumped around a stationary cathode. Either type is capable of recovering more than 90% of the silver from silver-rich solutions. The Hallmark systems use a combination of both in a single unit.

The use of "Closed Loop" fix solutions combined with Hallmark's in-line ElectroSilver Sensor can significantly reduce the amount of silver carried over into the final wash water. This method can reduce mixing and chemical usage by up to 50%.

Metallic Replacement (CRCs)

Metallic replacement is a process where elemental iron undergoes an oxidation-reduction reaction with the silver thiosulfate to produce ferrous ions and metallic silver. The exchange reaction is very rapid, but dependent on the contact of the silver-thiosulfate complex with the iron surface. Flow rate, iron surface area, contact time, and the pH of the solution are the major variables influencing recovery efficiency.

Precipitation (TMT)

Hallmark Refining offers Mini Labs a unique precipitation technology using TMT (trimercapto-s-triazine). The intent is to make silver recovery more efficient, economical and user friendly in areas where hauling may be the only other option. Hallmark has improved upon the original Kodak SR-2000 Silver Recovery Unit and now offers a line of small and medium precipitation silver recovery units.