Silver Recovery and Optimization from Waste X-Ray Photographic Film Using Sodium Hydroxide Stripping
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Date
2014-12
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Addis Ababa University
Abstract
Silver is a depleted precious resource and in the near future it all be used up. In addition to this, our country is not produced the metal at this moment. Extracting silver from enough silver-containing wastes like used X-ray photographic film will considerably save the foreign currency to import this metal. This work reports on a novel, simple, fast and cheap method to utilize waste x-ray film for recovering silver using sodium hydroxide stripping. In this study, the silver recovery was optimized against the stripping temperature, stripping time and sodium hydroxide concentration. Firstly, the film was washed, dried, cut and weighed. Then, the silver was stripped at three different factor’s level i.e. sodium hydroxide concentration (0.5M, 1.5M and 2.5M), temperature (50 oC, 70 oC and 90oC) and time (1 min, 10.5 min and 20 min.). Finally, silver was recovered by precipitation using sodium sulphide. The yield or recovery was then determined using XRF. A maximum silver recovery of 54% w/w and a purity level of 98.02% were obtained. The experimental results were then analyzed using Design Expert Software (version 7.0.0) to determine the optimum operating conditions. The optimum operating conditions found to be a stripping temperature of 70.81oc, stripping time of 10.90 minute and NaOH concentration of 1.46M. It is concluded that waste x-ray photographic film can be stripped by NaOH and precipitated by Na2S successfully and in most economical way.
Keywords: Silver recovery, waste photographic film, sodium hydroxide.
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Keywords
Silver recovery; waste photographic film; sodium hydroxide