Extraction of Silver From Photographic Waste

The waste photographic films/X-ray contains 1.5 2 % (w/w) black metallic silver which is recovered and reused. Around 18-20% of the world's silver needs are supplied by recycling photographic waste. Silver is a precious metal, further silver has wide uses like in jewellery, dentistry, photography, mirrors, optics, industries, etc. So the recovery of silver is beneficial in industrial, chemical and economical aspects. Recovery of silver from photographic wastes is interesting because of the economic value of silver and also from environmental point of view. In photographic industry, silver is recovered from development and fixing solution, spent rinse water and scrap films. Electrolysis is a commonly used method to recover silver from photographic wastes but it is not suitable for dilute silver concentration (less than 100 ppm) because the plating efficiencies are very low. This process requires high initial capital investment and high operating cost, and critical operating conditions that need to be constantly supervised. The 100 ppm of silver concentration in effluent is relatively high compared to recommended allowable discharge level of 0.1 to 1.0 mg/dm, which means that further treatment is required before it can be discharged to water stream. The oldest and conventional method of silver recovery, precipitation, could not achieve the recommended discharge level although it has provided an effective technique for silver recovery. This is because an industrial effluent contains complexing agents which might bind to the silver metal. This metal complex is sometime very stable and not able to be precipitated by precipitation process. To overcome the problem our method has a great potential and has been reported as an advanced technique for recovery of silver. KeywordsSilver, extraction, photographic waste.