Silver and support recovery from photosensitive material waste comprises silver halogenation, silver halide solubilisation, silver sepn. by electrolysis and gelatin removal

Abstract

In a process for recovering Ag and the support from photosensitive waste material, the waste contg. metallic Ag in addn. to Ag halide is treated preliminarily with an acidic oxidising chlorinating soln. to halogenate the metallic Ag. The Ag halide is then solubilised with a mixt. of Na thiosulphate and K pyrosulphite. Metallic Ag free waste is solubilised directly. The Ag in the soln. obtd. is sepd. electrolytically. The support is then treated with a soln. of Nacl basified with Na2CO3 or NaOH to remove the gelatin for further use. In order to recover Ag and the support with high yields, the waste is treated preliminarily, to halogenate metallic Ag, with a soln. of aqua regia diluted with demineralised water in ratio 1:1 to 1:10 or with the mixt. consisting of 0.1-100 g. NaCl, 0.6-600 ml. HNO3 and 200-2000 ml. demineralised water. The solubilisation of Ag halide takes place in a soln. contg. 200-600 g/l. Na thiosulphate and 10-400 g/l. K pyrosulphite. The support is worked up, to remove gelatin, with an Nacl soln. contg. 0.15-12% active Cl2 and an addn. of 0.1-10% Na2CO3 or NaOH.