Method for the recovery of silver from waste photographic fixer solutions

Patent · Sun Jan 01 00:00:00 EST 1984

OSTI ID:864979

Posey, Franz A ^[1]; Palko, Aloysius A ^[2]

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1. Concord, TN
2. Oak Ridge, TN

The method of the present invention is directed to the recovery of silver from spent photographic fixer solutions and for providing an effluent essentially silver-free that is suitable for discharge into commercial sewage systems. The present method involves the steps of introducing the spent photographic fixer solution into an alkaline hypochlorite solution. The oxidizing conditions of the alkaline hypochlorite solution are maintained during the addition of the fixer solution so that the silver ion complexing agents of thiosulfate and sulfite ions are effectively destroyed. Hydrazine monohydrate is then added to the oxidizing solution to form a reducing solution to effect the formation of a precipitate of silver which can be readily removed by filtration or decanting. Experimental tests indicate that greater than 99.99% of the original silver in the spent photographic fixer can be efficiently removed by practicing the present method. Also, the chemical and biological oxygen demand of the remaining effluent is significantly reduced so as to permit the discharge thereof into sewage systems at levels in compliance with federal and state environmental standards.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• DOE Contract Number: W-7405-ENG-26
• Assignee: United States of America as represented by United States (Washington, DC)
• Patent Number(s): US 4445935
• OSTI ID: 864979
• Country of Publication: United States
• Language: English

Related Subjects

method
recovery
silver
waste
photographic
fixer
solutions
directed
spent
providing
effluent
essentially
silver-free
suitable
discharge
commercial
sewage
systems
involves
steps
introducing
solution
alkaline
hypochlorite
oxidizing
conditions
maintained
addition
complexing
agents
thiosulfate
sulfite
effectively
destroyed
hydrazine
monohydrate
added
form
reducing
effect
formation
precipitate
readily
removed
filtration
decanting
experimental
tests
indicate
99
original
efficiently
practicing
chemical
biological
oxygen
demand
remaining
significantly
reduced
permit
levels
compliance
federal
environmental
standards
oxidizing conditions
significantly reduce
complexing agents
method involves
complexing agent
significantly reduced
readily removed
oxygen demand
experimental tests
photographic fixer
method involve
oxidizing solution
hypochlorite solution
fixer solution
fixer solutions
/75/423/