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1993 Award "For the development of a Silver Recovery Ion Exchange System to eliminate hazardous waster (silver ion) in washwater and allow recycling of this water" ©A.M.P.A.S ® |
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A well designed electrolytic silver recovery system will normally recover 85-95% of the available silver. The remaining silver is discharged in the wash water as carryover. Normally, one resin tank is used to recover 90% of the available silver. In special circumstances two tanks in series will be used to recover an additional 90%. The Degenkolb Engineering Ion Exchange Silver Recovery / Water Recycling unit is a micro-processor controlled system which automatically recovers the silver from the wash water of a photographic laboratory. Algae control is provided by the use of sulfuric acid with an automatic pH control, or selected algaecides. All water is filtered before Ion Exchange. If the water is to be recycled, the water is re filtered and treated before returning to the processor. Differential pressure gauges are provided to determine the need to change filters. |
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Terminal Recovery of Fixer or Bleach-Fix |
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Silver from excess fixer or bleach-fix can normally be removed by the Ion Exchange unit. A relay to operate a metering pump is installed in parallel with the starter for the main system pump. When the system pump is in operation, the overflow fixer or bleach-fix is pumped into the collection tank. The fixer or bleach-fix is diluted 1:100. |
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Silver Regeneration |
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The unit automatically regenerates based on water processed; typically every 7 to 14 days. The silver is recovered with an ammonium thiosulfate solution. After regeneration, the silver rich ammonium thiosulfate is pumped to a holding tank where the solution is adjusted for use as a replenisher. The regenerate solution is used as the next batch of replenisher for the fix or bleach-fix. The silver is recovered by the normal fix or bleach-fix processing silver recovery system. Alternately, a dedicated regeneration ammonium thiosulfate system may be operated. If used for recycling, following silver removal, the system is rinsed with brine to enable recycling the water. Regeneration of the resin system is totally automatic. |
In-Situ Silver Recovery Technology |
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Ion Exchange Electronics |
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The Ion Exchange System is operated by a micro-processor. All systems include proportional pH Controllers. Flow is monitored by a digital flow control system. Adjustments to the operating sequence are accomplished by an operator interface terminal, protected with a security code. A display panel indicates the system status. All operating controls and circuit breakers are on the front panel. |
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