A Novel Silver Recovery Method from Waste Photographic Films with NaOH Stripping

Silver, one of the precious and noble metals, is used in large quantities for many purposes, particularly in the photographic industry. It has been reported that 25% of the world’s silver needs are supplied by recycling and that 75% of this is obtained from photographic waste. For this reason, the methods applied to recover silver from photographic waste are important in reducing cost and time, and have a positive effect on environmental pollution. Compared to other films, waste X-ray photographic film contains a great deal of silver to enhance its sensitivity to transmitted X-rays and 1.5% to 2.0% silver by weight survives in the emulsion on the polyester film base, even after the developing and fixing processes. These waste films are a good source of silver that is reused for a variety of purposes including light-sensitive materials. Various studies have been carried out over a long period of time to recover the silver from these wastes, and most of them have been patented. The silver recovery methods from waste films can be classified as (a) burning the films directly, (b) oxidation of the metallic silver following electrolysis3−8, and (c) stripping the gelatin-silver layer using different solutions9−21. The second and third methods have been used more extensively for the recovery of