Extraction of silver from spent x-ray and photographic fixer solution in Tigray region, Ethiopia

摘要

Spent fixer solution from photographic industries and X-ray machines cause water and soil pollution if drained out without any treatment. This solution contains about 2 - 4 g of silver per liter. The maximum permitted level of silver in the waste solution is only 3 ppm. It is clear that concentration of silver in spent fixer solution may be thousand times greater than maximum stipulated limit. Moreover silver is precious and noble metal. So recovery of silver from waste fixer solution will not only prevent water and soil pollution but also prove to be profitable process. A survey in most of the places in Tigray Region shows that spent fixer solution is drained out without any treatment. The photographic industry is fast growing industry and this may lead to soil and water pollution. Two methods are identified as economical and simple without involving complicated procedures for extraction of silver. One is chemical method and the other an electrolytic method. Both methods are found to be successful; however electrolytic method is the preferred one because of its simplicity, economical and environmentally friendly. In photographic fixer solution about 2 gL~(-1) and in X-ray solution, about 3 gL~(-1) of silver were recovered.